CN106199284B - Resonance early warning method and system for capacitor switching - Google Patents

Abstract

The embodiment of the invention discloses a resonance early warning system and a method for switching capacitors, wherein the method comprises the steps of judging whether the switching states of capacitors to be monitored and capacitor branches where parallel capacitors are positioned in the same capacitor bank are changed; if the switching state changes, acquiring resonance point evaluation parameters of each capacitor branch before and after the switching state changes; evaluating a parallel resonance point and a series resonance point of the capacitor to be monitored according to the resonance point evaluation parameter; calculating absolute values of differences between the parallel resonance points and the front and rear adjacent integers respectively to serve as parallel resonance early warning values; calculating absolute values of differences between the serial resonance points and the front and rear adjacent integers respectively to serve as serial resonance early warning values; judging resonance early-warning levels at which the parallel resonance early-warning value and the series resonance early-warning value are respectively located; and carrying out resonance early warning on the capacitor to be monitored according to the resonance early warning grade. The technical scheme provided by the invention can timely and effectively early warn the resonance condition caused by capacitor switching.

Description

Resonance early warning method and system for capacitor switching

technical field

The invention relates to the technical field of electric power equipment, in particular to a resonance early warning method and system for capacitor switching.

Background technique

Capacitor switching, especially the switching on or off of high-voltage shunt capacitor banks, is one of the most common operations of power equipment in power systems. However, the switching process of capacitors may cause capacitor resonance, causing capacitors to jump as soon as they are connected, and even damage capacitors in severe cases. Such events often occur in power systems.

The main reason for this problem is that the resonance point of the system changes dynamically with the change of the system operation mode, so the switching combination of the capacitor bank will also significantly change the resonance point of each capacitor in the capacitor bank, resulting in the capacitor after switching. The group is just within the resonance range of one of the internal capacitors.

The switching of the capacitor bank is one of the most important factors affecting the resonance point of the system. However, in the prior art, there is no timely and effective early warning of the resonance caused by the switching of the capacitor bank. It happens from time to time that the resonance point of the system will be changed by cutting and eventually lead to capacitor tripping or accidents.

To sum up, how to timely and effectively provide timely and effective early warning of the resonance caused by capacitor switching has become a technical problem to be solved urgently by those skilled in the art.

Contents of the invention

Embodiments of the present invention provide a resonance early warning system and method for capacitor switching to solve the problem in the prior art that there is no timely and effective early warning for resonance caused by capacitor switching.

In order to solve the above technical problems, the embodiment of the present invention discloses the following technical solutions:

According to the first aspect of the present invention, a resonance early warning system for capacitor switching is provided. The resonance early warning system is used in a power system, and the power system includes: a high-voltage bus, a low-voltage bus, and a plurality of A capacitor electrically connected to the low-voltage bus; wherein, the low-voltage bus includes multiple low-voltage bus sections, adjacent low-voltage bus sections are connected through low-voltage bus tie circuit breakers, and capacitors electrically connected to the same low-voltage bus section form a capacitor bank; the capacitor A circuit breaker, an isolating switch on the upper side of the circuit breaker, an isolating switch on the lower side of the circuit breaker, and a current transformer are connected in series on the branch; the resonance early warning system for capacitor switching includes:

Switching state discriminators electrically connected to the circuit breaker of the capacitor branch corresponding to all capacitors in the same capacitor bank, the isolating switch on the upper side of the circuit breaker, and the isolating switch on the lower side of the circuit breaker are used to judge the switching state of each capacitor branch Whether there is a change, wherein, the capacitor branches corresponding to all the capacitors include the capacitor branch in the capacitor bank where the capacitor to be monitored and the parallel capacitor paralleled with the capacitor to be monitored are located;

A resonance point evaluation parameter retrieval module electrically connected to the switching state discriminator and each capacitor branch, used to obtain the switching state change if the switching state discriminator determines that the switching state changes Evaluation parameters of the resonance points of the front and rear and each capacitor branch;

A resonance point calculator electrically connected to the resonance point evaluation parameter retrieval module, for evaluating the parallel resonance point and the series resonance point of the capacitor to be monitored according to the resonance point evaluation parameter;

A resonance early warning discriminator electrically connected to the resonance point calculator, the resonance early warning discriminator comprising:

A parallel resonance warning value sub-calculator electrically connected to the resonance point calculator, used to calculate the absolute value of the difference between the parallel resonance point and the adjacent integer before and after, as a parallel resonance warning value, and,

A series resonance warning value sub-calculator electrically connected to the resonance point calculator, used to calculate the absolute value of the difference between the series resonance point and the adjacent integer before and after, respectively, as a series resonance warning value; and,

A resonance warning level sub-discriminator electrically connected to the parallel resonance warning value sub-calculator and the series resonance warning value sub-calculator, for judging where the parallel resonance warning value and the series resonance warning value are located. Resonance warning level;

An early warning signal alarm device electrically connected to the resonance early warning discriminator is used to give a resonance early warning to the capacitor to be monitored according to the resonance early warning levels at which the parallel resonance early warning value and the series resonance early warning value are respectively located.

Preferably, the resonance warning system for capacitor switching further includes:

An online or offline state discriminator, used to judge whether the capacitor to be monitored is in the online state or in the offline state;

The switching state discriminator includes an online state quantity signal collector electrically connected to the online or offline state discriminator, and is used to collect switches related to the capacitor to be monitored if the capacitor to be monitored is in an online state. The state quantity signal of the device, wherein the state quantity signal includes: the auxiliary contact signal of the circuit breaker on each capacitor branch, the auxiliary contact signal of the disconnector on the upper side or the lower side of the circuit breaker, and the auxiliary contact signal of the low-voltage bus tie circuit breaker Contact signal;

The online switching state change discriminator electrically connected to the online state quantity signal collector is used to judge whether the state quantity signals of the same switching device at adjacent sampling times in the capacitor bank are consistent, if the state quantity signals are inconsistent , it is determined that the switching state has changed; or,

The switching state discriminator includes an offline operating state collector electrically connected to the online or offline state discriminator, and is used to obtain the current sampling time of each capacitor branch in the capacitor bank when the capacitor is in an offline state. The operating status of the capacitor and the operating status of the capacitor where the switching operation of the capacitor branch occurs;

The offline switching state change discriminator electrically connected to the offline running state collector is used to judge whether the running state of the capacitor branch is consistent before and after the switching operation of the capacitor branch, and if not, determine whether the switching state of the capacitor branch is consistent. state changes.

Preferably, the resonance warning system for capacitor switching further includes:

A harmonic current analyzer electrically connected to the online or offline state discriminator and the current transformers on each capacitor branch, used to use the current transformers on each capacitor branch if the capacitor to be monitored is in an online state Obtain the harmonic current content rate;

The resonance early warning discriminator further includes: a harmonic current content rate comparator electrically connected to the harmonic current analyzer, specifically for comparing the magnitude relationship between the harmonic current content rate and a preset early warning content rate threshold;

The early warning signal alarm is also electrically connected to the harmonic current content rate comparator, which is used for resonance early warning according to the magnitude relationship between the harmonic current content rate and the preset content rate threshold, and the resonance early warning value where the parallel resonance early warning value is located. level and the resonance warning level at which the series resonance warning value is located, the resonance warning is performed on the capacitor to be monitored.

Preferably, the resonance early warning discriminator specifically further includes:

The warning level division sub-module electrically connected to the resonance warning level sub-discriminator is used to divide the warning value range of the resonance warning level into high warning level, low warning level and no warning level from low to high.

Preferably, the resonance warning system for capacitor switching further includes:

A resonance change calculator electrically connected to the resonance point calculator, used to calculate the amount and rate of change of the parallel resonance point and the series resonance point within a predetermined time before and after the switching state changes;

The resonance early warning discriminator also includes a resonance early warning value change calculator electrically connected to the resonance change calculator, which is used to calculate the The change amount and change rate of the parallel resonance warning value and the series resonance warning value;

The resonance early warning discriminator also includes a resonance early warning change trend prediction module electrically connected to the resonance early warning value change calculator, for according to the variation and rate of change of the parallel resonance early warning value and the series resonance early warning value, Predicting the resonance warning change trend of the capacitor to be monitored.

According to the second aspect of the present invention, a resonance early warning method for capacitor switching is also provided, including:

Judging whether the switching state of the capacitor to be monitored in the same capacitor bank and the capacitor branch where the parallel capacitor paralleled with the capacitor to be monitored is located changes;

If the switching state changes, the resonance point evaluation parameters of each capacitor branch before and after the switching state change are obtained;

Evaluate the parallel resonance point and the series resonance point of the capacitor to be monitored according to the resonance point evaluation parameters;

Calculate the absolute value of the difference between the parallel resonance point and the adjacent integer before and after, as the parallel resonance warning value, and calculate the absolute value of the difference between the series resonance point and the adjacent integer before and after, respectively, as the series resonance point Resonance warning value;

judging the resonance warning levels at which the parallel resonance warning value and the series resonance warning value are respectively located;

A resonance warning is performed on the capacitor to be monitored according to the resonance warning level.

Preferably, the resonance warning method for capacitor switching also includes:

judging whether the capacitor to be monitored is in an online state or in an offline state;

If the capacitor to be monitored is in the online state, then collect the state quantity signal of the switching device related to the capacitor to be monitored; wherein, the state quantity signal includes: the auxiliary contact signal of the circuit breaker on each capacitor branch, the circuit breaker Auxiliary contact signal of upper or lower side isolating switch and auxiliary contact signal of low-voltage bus tie circuit breaker;

Judging whether the state quantity signals of the same switching device at adjacent sampling moments in the capacitor bank are consistent;

If the state quantity signals are inconsistent, it is determined that the switching state has changed; or,

If the capacitor is in an offline state, then obtain the operating state of each capacitor branch in the capacitor bank at the current sampling time and the operating state of the capacitor where the switching operation of the capacitor branch occurs;

Judging whether the operation status of the capacitor branch is consistent before and after the switching operation of the capacitor branch occurs;

If the operating states of the capacitor branches are inconsistent, it is determined that the switching state has changed.

Preferably, the resonance warning method for capacitor switching also includes:

If the capacitor to be monitored is in the online state, then use the current transformer on each capacitor branch to obtain the harmonic current content rate;

Comparing the magnitude relationship between the harmonic current content rate and the preset warning content rate threshold;

According to the magnitude relationship between the harmonic current content rate and the preset warning content rate threshold, the resonance warning level where the parallel resonance warning value is located, and the resonance warning level where the series resonance warning value is located, the capacitor to be monitored is monitored. Resonance warning.

Preferably, the judging the resonance warning level at which the parallel resonance warning value and the series resonance warning value are located includes:

The range of the absolute value of the difference between each resonance point and the adjacent integers before and after is taken as the range of the early warning value;

The range of early warning values is divided into high early warning level, low early warning level and no early warning level from low to high.

Preferably, the evaluation parameters of the resonance point include: the capacitor capacity, capacitive reactance value, reactance value, series reactance ratio and short-circuit capacity of the capacitor branch where the capacitor to be monitored and the parallel capacitor paralleled with the capacitor to be monitored are located ;

The step of evaluating the parallel resonance point and the series resonance point of the capacitor to be monitored according to the resonance point evaluation parameters includes:

和

分别计算电容器组的并联谐振点和串联谐振点；式中，n₁为并联谐振点，n₂为串联谐振点，Q_C为电容器容量，S_d为并联电容器所处母线的短路容量，X_C为所述电容器组的容抗值；X_L为电容器组串联电抗的电抗值；K为串抗率。According to the formula

and

Calculate the parallel resonance point and series resonance point of the capacitor bank respectively; in the formula, n ₁ is the parallel resonance point, n ₂ is the series resonance point, Q _C is the capacitor capacity, S _d is the short-circuit capacity of the bus where the parallel capacitor is located, X _C is the capacitive reactance value of the capacitor bank; X _L is the reactance value of the capacitor bank series reactance; K is the series reactance rate.

Preferably, the resonance warning method for capacitor switching also includes:

calculating the change amount and change rate of the parallel resonance point and the series resonance point within a predetermined time before and after the switching state changes;

calculating the change amount and change rate of the parallel resonance early warning value and the series resonance early warning value according to the change amount and change rate of the parallel resonance point and the series resonance point;

According to the change amount and change rate of the parallel resonance early warning value and the series resonance early warning value, the resonance early warning variation trend of the capacitor to be monitored is predicted.

It can be seen from the above technical solutions that the resonance early warning scheme for capacitor switching provided by the embodiment of the present invention obtains the resonance point evaluation parameters of each capacitor branch before and after the switching state changes after determining that the switching state of the capacitor changes, and then according to the Resonance point evaluation parameters Calculate the parallel resonance point and series resonance point of the capacitor to be monitored, so as to calculate the respective resonance warning value according to the parallel resonance point and series resonance point, calculate the resonance warning level at which it is located, and carry out resonance warning of the capacitor to be monitored. In summary , the resonance early warning scheme for capacitor switching can provide timely, accurate and effective early warning for the resonance caused by capacitor switching.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, In other words, other drawings can also be obtained from these drawings on the premise of not paying creative work.

FIG. 1 is a schematic flow chart of the first resonance early warning method for capacitor switching provided by an embodiment of the present invention;

FIG. 2 is a schematic flowchart of a second resonance early warning method for capacitor switching provided by an embodiment of the present invention;

FIG. 3 is a schematic flowchart of a third resonance early warning method for capacitor switching provided by an embodiment of the present invention;

4 is a schematic flowchart of a fourth resonance early warning method for capacitor switching provided by an embodiment of the present invention;

5 is a schematic flowchart of a fifth resonance warning method for capacitor switching provided by an embodiment of the present invention;

6 is a schematic flowchart of a sixth resonance warning method for capacitor switching provided by an embodiment of the present invention;

Fig. 7 is a structural schematic diagram of the first resonance early warning system for capacitor switching provided by an embodiment of the present invention;

FIG. 8 is a schematic structural diagram of a second capacitor switching resonance early warning system provided by an embodiment of the present invention;

FIG. 9 is a schematic structural diagram of a resonance early warning system for switching capacitors according to an embodiment of the present invention;

FIG. 10 is a schematic structural diagram of a resonance early warning system for fourth capacitor switching provided by an embodiment of the present invention;

Fig. 11 is a structural schematic diagram of a fifth resonance early warning system for capacitor switching provided by an embodiment of the present invention;

Fig. 12 is a structural schematic diagram of the sixth resonance early warning system for capacitor switching provided by the embodiment of the present invention;

Fig. 13 is a schematic diagram of system input and output of a capacitor in "online" mode provided by an embodiment of the present invention;

Fig. 14 is a schematic diagram of system input and output of a capacitor in "offline" mode provided by an embodiment of the present invention.

Detailed ways

In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described The embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

Referring to FIG. 1 , it is a schematic flowchart of a resonance early warning method for capacitor switching provided by an embodiment of the present invention. As shown in FIG. 1 , the resonance early warning method for capacitor switching includes:

S110: Determine whether the switching state of the capacitor to be monitored in the same capacitor bank and the capacitor branch where the capacitor to be monitored in parallel with the capacitor to be monitored changes; capacitor switching will cause capacitor resonance, causing the capacitor to jump as soon as it is closed, Even if the capacitor is damaged, in the embodiment of the present disclosure, it is necessary to measure whether the switching state of the capacitor branch of the capacitor to be monitored in the capacitor bank composed of multiple capacitors and the capacitor to be monitored in parallel with the capacitor to be monitored has changed, and further judge whether the switching state of the capacitor branch is changed. Whether the change of switching state causes capacitor resonance, specifically, it is necessary to take a capacitor to be monitored in the capacitor bank as the measurement object, and judge whether it causes the resonance change of the capacitor under test according to the switching state changes of other capacitor branches.

S120: If the switching state changes, obtain resonance point evaluation parameters of each capacitor branch before and after the switching state change;

By obtaining the resonance point evaluation parameters of each capacitor branch before and after the switching state changes, it is possible to evaluate whether the parameters change according to the resonance point, calculate the resonance of the capacitor, and then give early warning of capacitor resonance in time to avoid accidents.

S130: Calculate a parallel resonance point and a series resonance point of the capacitor to be monitored according to the resonance point evaluation parameter;

The parallel resonance point of the capacitor reflects the influence of switching changes of other capacitor branches on the capacitor, and the series resonance point reflects the influence of the switching of the capacitor branch itself on the capacitor. By calculating the parallel resonance point and series resonance of the capacitor to be monitored point, it is possible to comprehensively and accurately understand the influence of the switching of each capacitor branch in the capacitor bank on the capacitor to be monitored.

S140: Calculate the absolute value of the difference between the parallel resonance point and the adjacent integer before and after, as a parallel resonance warning value, and calculate the absolute value of the difference between the series resonance point and the adjacent integer before and after, respectively, As a series resonance warning value.

If the resonance point is an integer, it means that different capacitors or capacitor branch equipment in the capacitor bank resonate. By calculating the absolute value of the difference between the parallel resonance points and the adjacent integers before and after, it can be indicated that the parallel resonance point of the capacitor to be monitored exists. The degree of resonance and the probability of resonance occur, so as to accurately warn the parallel resonance in the capacitor bank. Similarly, calculating the absolute value of the difference between the series resonance point and the adjacent integer before and after can represent the series connection of the capacitor to be monitored. The degree and probability of resonance at the resonance point can be used to accurately predict the series resonance in the capacitor bank.

S150: Determine the resonance warning levels at which the parallel resonance warning value and the series resonance warning value are respectively located;

S160: Perform a resonance warning on the capacitor to be monitored according to the resonance warning level.

By calculating the resonance warning level where the parallel resonance warning value and the series resonance warning value are located, an accurate warning reference can be provided for the capacitor to be monitored, thereby reducing accidents caused by resonance.

The resonance early warning method for capacitor switching provided by the embodiment of the present invention obtains the resonance point evaluation parameters of each capacitor branch before and after the switching state changes after it is determined that the switching state of the capacitor changes, and then calculates the waiting time based on the resonance point evaluation parameters. Monitor the parallel resonance point and series resonance point of the capacitor, and further calculate the respective resonance warning values according to the parallel resonance point and series resonance point, and then calculate the resonance warning level where the parallel resonance point and the series resonance point are located, and carry out resonance warning for the capacitor to be monitored. It can provide timely, accurate and effective early warning of the resonance situation caused by capacitor switching.

The capacitor to be monitored is divided into online and offline states. In different states, the resonance early warning method of the capacitor to be monitored is different. Specifically, the resonance early warning method in the online state is shown in Figure 2. The capacitor input shown in the embodiment shown in Figure 1 Cut resonance early warning methods also include:

S210: Determine whether the capacitor to be monitored is online or offline; if it is online, execute step S220;

Pre-judging whether the capacitor to be monitored is online or offline can provide more accurate and rapid resonance warnings for the capacitor to be monitored according to the state of the capacitor to be monitored.

S220: Collect the state quantity signal of the switch device related to the capacitor to be monitored; wherein, the state quantity signal includes: an auxiliary contact signal of a circuit breaker on each capacitor branch, an upper side isolation switch or a lower side isolation switch of the circuit breaker Auxiliary contact signal of low-voltage bus tie circuit breaker and auxiliary contact signal;

In the power system, from the low-voltage busbar to the capacitor, there are generally disconnectors on the upper side of the circuit breaker, circuit breakers, and disconnectors on the lower side of the circuit breaker in series, which determine the on-off of the capacitor. Therefore, the capacitor can be further judged by the state quantity signal of the switching device. Resonance point, early warning of resonance point. Wherein, when closing the switching device, the isolating switch on the lower side of the circuit breaker, the circuit breaker, and the isolating switch on the upper side of the circuit breaker are combined in sequence; the order is reversed when the switch is turned off. And the switching operation of the isolating switch on the upper side of the circuit breaker is consistent with that on the isolating switch on the lower side of the circuit breaker. Therefore, only the state quantity signal of the isolating switch on the upper side of the circuit breaker or the isolating switch on the lower side of the circuit breaker can be collected.

S230: Judging whether the state quantity signals of the same switching device in the capacitor bank at adjacent sampling times are consistent;

S240: If the state quantity signals are consistent, determine that the switching state has changed;

By judging whether the state quantity signal of the same switching device at the previous and subsequent sampling times in the capacitor bank is consistent, the state of the switching device can be judged according to the state quantity signal, for example: the state quantity at the previous sampling time of the auxiliary contact and the state at the current sampling time Carry out "AND" operation to determine whether the switching value of the auxiliary contact has changed.

In the above step S210: judging whether the capacitor to be monitored is in the online state or in the offline state, the resonance early warning method in the offline state is shown in Figure 3, and the resonance early warning method for capacitor switching provided by the embodiment shown in Figure 1 also includes the following steps :

S310: Obtain the operating status of each capacitor branch in the capacitor bank at the current sampling time and the operating status of the capacitor where the switching operation of the capacitor branch occurs;

When the capacitor is offline, the operating status of each capacitor branch at the current sampling time and the operating status after the switching operation of the capacitor branch can be input manually.

S320: Judging whether the operating states of the capacitor branch are consistent before and after the switching operation of the capacitor branch occurs;

S330: If the running states of the capacitor branches are inconsistent, determine that the switching state has changed.

By judging whether the operation state of the capacitor branch is consistent before and after the switching operation of the capacitor branch, that is, performing binary "AND" operation on the operation state, it can be judged whether the switching state of each capacitor branch in the capacitor bank has changed.

Wherein, when step S210 shown in FIG. 2 determines that the capacitor to be monitored is in the online state, as shown in FIG. , also includes the following steps:

S410: Obtain the harmonic current content rate by using the current transformer on each capacitor branch;

The current transformer can convert the high-voltage strong electrical signal in the grid into a low-voltage weak electrical signal, thereby obtaining harmonic current from the high-voltage strong electrical signal in the grid. The background harmonics of the grid are changing dynamically. When the harmonic content of the grid is high And when there is a resonance condition, the resonance event of the capacitor will inevitably occur. Therefore, when the capacitor to be monitored is online, by obtaining the harmonic current in the power grid, an early warning can be given for the resonance of the capacitor to avoid accidents. .

S420: Comparing the magnitude relationship between the harmonic current content rate and the preset warning content rate threshold;

S430: According to the size relationship between the harmonic current content rate and the preset warning content rate threshold, the resonance warning level where the parallel resonance warning value is located, and the resonance warning level where the series resonance warning value is located, perform the monitoring Capacitor for resonance warning.

As a preferred embodiment: divide the resonance warning level according to the calculation result of the resonance point and the harmonic current content rate, when the harmonic current content rate is greater than or equal to 5%, and the resonance level is "high", Red warning; when the harmonic current content is greater than or equal to 5% and the resonance level is "low", a yellow warning is issued; when the harmonic current content is less than 5% and the resonance level is "high", a yellow warning is issued ; In other cases, no warning is issued; among them, the red warning has a higher possibility of resonance than the yellow warning.

The preset warning content ratio threshold can reflect the background harmonic situation of the power grid. If the harmonic current content ratio is greater than the preset warning content ratio threshold value, it indicates that the harmonic content in the power grid is high. By judging the harmonic current content ratio and The relationship between the threshold value of the preset warning content rate and the resonance warning level of the series-parallel resonance warning value can provide effective and accurate resonance warning for the capacitor to be monitored, thereby accurately judging the resonance of the capacitor to be monitored.

Wherein, the method for judging the resonance warning level at which the parallel resonance warning value and the series resonance warning value are located in Fig. 1 specifically includes:

S510: Use the range of the absolute value of the difference between each resonance point and the adjacent integer before and after as the range of the warning value;

The absolute value of the difference between the resonance point and the adjacent integers is within a certain range, such as 0 to 1. By using the range of the absolute value of the difference between each resonance point and the adjacent integers as the early warning value range, it can be treated Monitor the resonance point of the capacitor for accurate early warning.

S520: Divide the warning value range from low to high into high warning level, low warning level and no warning level;

Due to the characteristics of resonance, the closer the numerical difference between the two harmonics, or even overlap, the greater the possibility of resonance; the farther the numerical difference is, the less likely it is to occur resonance. The closer the point is to the integer, the more likely the resonance will occur; the smaller the distance, the less likely the resonance will occur. Therefore, dividing the values of the early warning value range from low to high into high early warning level, low early warning level and no early warning level can accurately determine the early warning level of the resonance point, so as to carry out accurate resonance early warning of the capacitor to be monitored.

S530: Determine the warning levels of the parallel resonance warning value and the series resonance warning value, and give a warning to the capacitor to be monitored.

Specifically, according to the calculation result of the resonance point, the division of the early warning level range of the resonance point is firstly carried out, and the resonance point n is rounded to obtain an integer k, and then the resonance point is subtracted from the integer k and the integer k+1 respectively, and then Take the absolute value to get the value m, that is, when a certain resonance point falls on the nearest integer harmonic to both sides of the resonance point, if the value m is between 0-0.1, the warning level is high, if the value m is 0.1 If the value n is greater than 0.15, the warning level is low. If the value n is greater than 0.15, there will be no warning.

By judging the early warning level of the parallel resonance early warning value and the series resonance early warning value, the capacitor to be monitored can be warned, the probability of resonance of the capacitor to be monitored can be accurately judged, and the occurrence of accidents caused by resonance can be further reduced.

Wherein, the above-mentioned resonance point evaluation parameters include: the capacitor capacity, capacitive reactance value, reactance value, series reactance rate and short-circuit capacity value of the capacitor to be monitored and the capacitor branch where the parallel capacitor connected with the capacitor to be monitored is located;

The method steps of calculating the parallel resonance point and the series resonance point of the capacitor to be monitored according to the resonance point evaluation parameters before and after the switching state change include:

和

分别计算电容器组的并联谐振点和串联谐振点；式中，n₁为并联谐振点，n₂为串联谐振点，Q_C为电容器容量，S_d为并联电容器所处母线的短路容量，X_C为所述电容器组的容抗值；X_L为电容器组串联电抗的电抗值；K为串抗率。According to the formula

and

Calculate the parallel resonance point and series resonance point of the capacitor bank respectively; in the formula, n ₁ is the parallel resonance point, n ₂ is the series resonance point, Q _C is the capacitor capacity, S _d is the short-circuit capacity of the bus where the parallel capacitor is located, X _C is the capacitive reactance value of the capacitor bank; X _L is the reactance value of the capacitor bank series reactance; K is the series reactance rate.

The parallel resonance point and series resonance point often change, so it is necessary to judge the trend of resonance warning according to the parallel resonance point and series resonance point. Therefore, as shown in Figure 6, the above resonance warning method for capacitor switching also includes:

S610: Calculate the change amount and change rate of the parallel resonance point and the series resonance point within a predetermined time before and after the switching state changes;

S620: Calculate the change amount and change rate of the parallel resonance warning value and the series resonance warning value according to the change amount and change rate of the parallel resonance point and the series resonance point;

By calculating the change amount and change rate of the parallel resonance early warning value according to the change amount and change rate of the parallel resonance point, and calculating the change amount and change rate of the series resonance point according to the change amount and change rate of the series resonance point, the resonance of the monitoring capacitor can be treated Accurately evaluate the early warning trend, and further search for capacitors that are prone to resonance accidents.

S630: Predict a resonance warning change trend of the capacitor to be monitored according to the change amount and change rate of the parallel resonance warning value and the series resonance warning value.

By predicting the change trend of resonance early warning of the capacitor to be monitored, long-term and accurate early warning can be carried out for each capacitor in the capacitor bank, the resonance trend of the capacitor can be evaluated, and the capacitor prone to resonance fault can be found.

Based on the same inventive concept, corresponding to the resonance early warning method for capacitor switching provided by the present invention, the present invention also provides an embodiment of a resonance early warning system for capacitor switching, since the method corresponding to the system embodiment is the embodiment of the present application Resonance early warning method, and the principle of the problem solved by the system is similar to the method, therefore, the implementation of the system embodiment can refer to the implementation of the method embodiment.

Referring to Fig. 7 and Fig. 8, it is a schematic structural diagram of the capacitor switching resonance early warning system provided by the embodiment of the present invention. As shown in Fig. 7, the capacitor switching resonance early warning system provided by the embodiment of the present invention is used in a power system, The power system includes: a high-voltage bus, a low-voltage bus (including section 1 of the low-voltage bus and section II of the low-voltage bus in FIG. 1 ), and a plurality of capacitors (such as C1, C2, C3 and C4); wherein, the capacitors electrically connected to the same low-voltage bus section form a capacitor bank; circuit breakers (QF1, QF2, QF3 and QF4), circuit breaker upper side isolating switches (QS11, QS21, QS31 and QS41), isolating switches under the circuit breaker (QS12, QS22, QS32 and QS42), and current transformers (CT1, CT2, CT3 and CT4); the low-voltage bus is divided into different low-voltage buses through the low-voltage bus tie circuit breaker QF12 Sections (capacitor bank I and capacitor bank II), capacitors connected in parallel to the same low-voltage bus section form a capacitor bank, and adjacent low-voltage bus sections are connected through low-voltage bus tie circuit breakers; the resonance warning system for switching capacitors includes:

The switching state discriminator 701 is electrically connected to the circuit breaker of the capacitor branch corresponding to all the capacitors in the same capacitor bank, the isolating switch on the upper side of the circuit breaker and the isolating switch on the lower side of the circuit breaker, and is used to judge the switching of each capacitor branch Whether the state changes; wherein, the capacitor branches corresponding to all the capacitors include the capacitor branch in the capacitor bank where the capacitor to be monitored and the parallel capacitor paralleled with the capacitor to be monitored are located. Wherein, as shown in FIG. 8 , the switching state discriminator 701 is also connected to the low-voltage bus tie circuit breaker.

The resonance point evaluation parameter retrieval module 702 electrically connected to the switching state discriminator 701 and the capacitor branches respectively, is used for when the switching state discriminator 701 determines that the switching state changes, Obtain the resonance point evaluation parameters of each capacitor branch before and after the switching state change;

The resonance point calculator 703 electrically connected to the resonance point evaluation parameter retrieval module 702 is used to calculate the parallel resonance point and the series resonance point of the capacitor to be monitored according to the resonance point evaluation parameter;

The resonance early warning discriminator 704 electrically connected to the resonance point calculator 703, as shown in Figure 8, the resonance early warning discriminator 704 includes:

The parallel resonance early warning value sub-calculator 7041 electrically connected to the resonance point calculator 703 is used to calculate the absolute value of the difference between the parallel resonance point and the adjacent integer before and after, respectively, as the parallel resonance early warning value;

The series resonance warning value sub-calculator 7042 electrically connected to the resonance point calculator 703 is used to calculate the absolute value of the difference between the series resonance point and the adjacent integer before and after, respectively, as a series resonance warning value;

And a resonance warning level sub-discriminator 7043 electrically connected to the parallel resonance warning value sub-calculator 7041 and the series resonance warning value sub-calculator 7042;

The early warning signal alarm 705 electrically connected to the resonance early warning level sub-discriminator 7043 is used to resonate the capacitor to be monitored according to the resonance early warning levels at which the parallel resonance early warning value and the series resonance early warning value are respectively located early warning.

The resonance early warning system for capacitor switching provided by the embodiment of the present invention obtains the resonance point evaluation parameters of each capacitor branch before and after the switching state changes after it is determined that the switching state of the capacitor changes, and then calculates the waiting time based on the resonance point evaluation parameters. Monitor the parallel resonance point and series resonance point of the capacitor, so as to calculate the respective resonance warning value according to the parallel resonance point and the series resonance point, calculate the resonance warning level at which it is located, and carry out resonance warning of the capacitor to be monitored, which can prevent the resonance caused by capacitor switching Provide timely, accurate and effective early warning of the situation.

The capacitor to be monitored is divided into online and offline states. In different states, the resonance early warning method of the capacitor to be monitored is different. Specifically, the resonance early warning system in the online state is shown in Figure 9, and the capacitor input provided by the embodiment shown in Figure 7 Cut's Resonant Early Warning System also includes:

An online or offline state discriminator 706, configured to determine whether the capacitor to be monitored is in an online state or in an offline state;

The switching state discriminator 701 includes an online state quantity signal collector 7011 electrically connected to the online or offline state discriminator 706, which is used to collect information related to the capacitor to be monitored if the capacitor to be monitored is in an online state. The state quantity signal of the switching device related to the capacitor, wherein the state quantity signal of the switching device includes: the auxiliary contact signal of the circuit breaker on each capacitor branch, the auxiliary contact signal of the upper or lower side isolation switch of the circuit breaker, and Auxiliary contact signal of low-voltage bus tie circuit breaker;

The online switching state change discriminator 7012 electrically connected to the online state quantity signal collector 7011 is used to judge whether the state quantity signals of the same switching device at adjacent sampling times in the capacitor bank are consistent, if the state quantity If the signals are consistent, it is determined that the switching state has changed;

The resonance early warning system in the offline state is also shown in Figure 9, and the resonance early warning system for capacitor switching provided by the embodiment shown in Figure 7 also includes the following structure:

The offline running state collector 7013 electrically connected to the online or offline state discriminator 706 is used to obtain the running state of each capacitor branch in the capacitor bank at the current sampling time and the occurrence of the capacitor branch if the capacitor is in the offline state. Operating status of capacitors for switching operations;

When the capacitor is offline, the operating status of the capacitor branch at the current sampling time and the operating status after the switching operation of the capacitor branch can be input manually.

The offline switching state change discriminator 7014 electrically connected to the offline running state collector 7013 is used to judge whether the running state of the capacitor branch is consistent before and after the switching operation of the capacitor branch. The above switching status changes.

Among them, when it is determined that the capacitor to be monitored is in the online state, as shown in Figure 7 and Figure 9, the above resonance warning system for capacitor switching also includes the following structure:

A harmonic current analyzer 707 electrically connected to the on-line or off-line state discriminator 706 and a current transformer (such as CT1 and CT2 corresponding to the capacitor bank 1) respectively, for if the capacitor to be monitored is on-line, use The current transformer on each capacitor branch obtains the harmonic current content rate;

The current transformer can convert the high-voltage strong electrical signal in the grid into a low-voltage weak electrical signal, thereby obtaining harmonic current from the high-voltage strong electrical signal in the grid. The background harmonics of the grid are changing dynamically. When the harmonic content of the grid is high And when there is a resonance condition, the resonance event of the capacitor will inevitably occur. Therefore, when the capacitor to be monitored is online, by obtaining the harmonic current in the power grid, an early warning can be given for the resonance of the capacitor to avoid accidents. .

As shown in Figure 10, the resonance early warning discriminator 704, in addition to the various structures provided by the above embodiments, also includes: a harmonic current content rate comparator 7044 electrically connected to the harmonic current analyzer 707, specifically used to compare the The relationship between the harmonic current content rate and the preset warning content rate threshold;

The early warning signal alarm 705 is also electrically connected to the harmonic current content rate comparator 7044, and is also used for the size relationship between the harmonic current content rate and the preset content rate threshold and the location of the parallel resonance early warning value. The resonance early warning level of the resonance early warning level and the resonance early warning level of the series resonance early warning value are used to perform resonance early warning for the capacitor to be monitored.

The preset warning content ratio threshold can reflect the background harmonic situation of the power grid. If the harmonic current content ratio is greater than the preset warning content ratio threshold value, it indicates that the harmonic content in the power grid is high. By judging the harmonic current content ratio and The relationship between the threshold value of the preset warning content rate and the resonance warning level of the series-parallel resonance warning value can provide effective and accurate resonance warning for the capacitor to be monitored, thereby accurately judging the resonance of the capacitor to be monitored.

Wherein, as shown in FIG. 11 , the resonance early warning discriminator 704 provided in the above-mentioned embodiment shown in FIG. 7 specifically includes:

The warning level division sub-module 7044 electrically connected to the resonance warning level sub-discriminator 7043 is used to divide the values of the warning value range from low to high into high warning level, low warning level and no warning level.

Specifically, according to the calculation result of the resonance point, the division of the early warning level range of the resonance point is firstly carried out, and the resonance point n is rounded to obtain an integer k, and then the resonance point is subtracted from the integer k and the integer k+1 respectively, and then Take the absolute value to get the value m, that is, when a certain resonance point falls on the nearest integer harmonic to both sides of the resonance point, if the value m is between 0-0.1, the warning level is high, if the value m is 0.1 If the value n is greater than 0.15, the warning level is low. If the value n is greater than 0.15, there will be no warning.

By judging the early warning level of the parallel resonance early warning value and the series resonance early warning value, the capacitor to be monitored can be warned, the probability of resonance of the capacitor to be monitored can be accurately judged, and accidents caused by resonance can be further reduced.

Wherein, the above-mentioned resonance point evaluation parameters include: the capacitor capacity, capacitive reactance value, reactance value, series reactance rate and short-circuit capacity value of the capacitor branch where the capacitor to be monitored and the parallel capacitor paralleled with the capacitor to be monitored are located;

The method steps of calculating the parallel resonance point and the series resonance point of the capacitor to be monitored according to the resonance point evaluation parameters before and after the switching state change include:

和

分别计算电容器组的并联谐振点和串联谐振点；式中，n₁为并联谐振点，n₂为串联谐振点，Q_C为电容器容量，S_d为并联电容器所处母线的短路容量，X_C为所述电容器组的容抗值；X_L为电容器组串联电抗的电抗值；K为串抗率。According to the formula

and

Calculate the parallel resonance point and series resonance point of the capacitor bank respectively; in the formula, n ₁ is the parallel resonance point, n ₂ is the series resonance point, Q _C is the capacitor capacity, S _d is the short-circuit capacity of the bus where the parallel capacitor is located, X _C is the capacitive reactance value of the capacitor bank; X _L is the reactance value of the capacitor bank series reactance; K is the series reactance rate.

The parallel resonance point and the series resonance point often change, so it is necessary to judge the trend of the resonance warning according to the parallel resonance point and the series resonance point. Therefore, as shown in Figure 9 and Figure 12, the resonance warning of capacitor switching provided by the above embodiment The system also includes:

The resonance change calculator 708 electrically connected to the resonance point calculator 703 is used to calculate the change amount and change rate of the parallel resonance point and the series resonance point within a predetermined time before and after the switching state changes;

The resonance early warning discriminator 704 also includes a resonance early warning value change calculator 7045 electrically connected to the resonance change calculator 708, which is specifically used to, according to the change amount and change rate of the parallel resonance point and the series resonance point, Calculating the variation and rate of change of the parallel resonance warning value and the series resonance warning value;

The resonance early warning discriminator 704 also includes a resonance early warning change trend prediction module 7046 electrically connected to the resonance early warning value change calculator 7045, which is specifically configured to The amount and the rate of change are used to predict the change trend of the resonance warning of the capacitor to be monitored.

Taking the resonance early warning system of capacitor switching shown in Figure 7 and Figure 9 as an example, and taking capacitor C1 as the capacitor to be monitored, when the capacitor C3 is online and offline respectively, the resonance effect of capacitor C3 switching on the capacitor C1 to be monitored is taken as an example, and the capacitor C1 is analyzed. Group put into operation of the resonance warning situation. Specifically, as follows:

Analyze the resonance early warning situation of capacitor bank put into operation in "online" mode.

Assuming that the circuit breaker QF1 is in the closed position, the capacitor to be monitored, that is, the first group of capacitors C1 is put into operation, and the bus tie circuit breaker QF12 is in the disconnected position, now it is necessary to put the third group of capacitors C3 into operation; analyze this operation in the "online" mode The resonance warning situation caused, the data to be collected is shown in Figure 13;

The sequence of operating C3 to be put into operation is: closing the disconnector switch QS32 on the lower side of the circuit breaker-closing the disconnector switch QS31 on the upper side of the circuit breaker-closing the circuit breaker QF3; The third group of capacitors may be put into operation, and the online state quantity signal collector 7011 is started, and the steps are as follows:

Step 701: Select "online" mode;

Step 702: Judging the operation of the capacitor bank by the online state quantity signal collector 7011; since the sequence of putting C3 into operation is QS32-combining QS31-combining QF3, at this time, the online status quantity signal collector 7011 judges that the position of QS31 changes , it can be seen that the third group of capacitors may be put into operation;

和

分别计算电容器组的并联谐振点和串联谐振点；操作前的Q_C为第一组电容器的容量，操作后的Q_C为第一组电容器的容量加上第三组电容器组的容量；Step 703: According to the formula

and

Calculate the parallel resonance point and series resonance point of the capacitor bank respectively; _QC before operation is the capacity of the first group of capacitors, and _QC after operation is the capacity of the first group of capacitors plus the capacity of the third group of capacitors;

Step 704: Harmonic current analysis; judging whether the content of each harmonic current exceeds 5%;

Step 705: Calculation of the resonance point; first, carry out the early warning level of the resonance point, round the resonance point to obtain an integer k, subtract the resonance point from the integer k and the integer k+1, and then take the absolute value to obtain the value n, that is, when a certain resonance point falls on the nearest integer harmonic to the resonance point, if the value n is between 0.-0.1, the warning level is high; if the value n is between 0.1-0.15, the warning level is is low, if the value n is greater than 0.15, no warning will be issued;

For example, the calculated parallel resonance point is 2.78, and the series resonance point is 3.92, then round up 2.78 to get 2, then subtract 2 and 3 from 2.78 and take the absolute value to get 0.78 and 0.22; the same for the series resonance point A set of numbers can be obtained as 0.92 and 008;

Step 706: resonance point evaluation; if the value n is between 0-0.1, the warning level is high; if the value n is between 0.1-0.15, the warning level is low; if the value n is greater than 0.15, no warning is given;

For the case where the parallel resonance point is 2.78 and the series resonance point is 3.92, obviously, the parallel resonance is not within the warning range, and the series resonance warning level is high;

Step 707: On-line resonance evaluation; according to the calculation results of the resonance point and the harmonic current content rate, the division of the resonance warning level is carried out: (1) the harmonic current content rate is greater than or equal to 5%, and the resonance level is high, and the red warning is issued; (2) If the harmonic current content rate is greater than or equal to 5%, and the resonance level is low, a yellow warning will be issued; (3) if the harmonic current content rate is less than 5%, and the resonance level is high, a yellow warning will be issued; (4) Other conditions are not Warning.

Step 708: In the case of reaching the resonance warning, output the number of resonance points, resonance type and resonance warning level; in the case of not reaching the resonance warning, the output warning result is empty;

With C1 in the "offline" mode, analyze the resonance warning situation of the capacitor bank put into operation.

Assume that QF1 is in the closed position, the first group of capacitors C1 is put into operation, and the bus tie circuit breaker QF12 is in the disconnected position;

Now it is necessary to put the third group of capacitors C3 into operation; analyze the resonance warning caused by this operation in the "offline" mode, the data to be collected is shown in Figure 14, and the steps are as follows:

Step 801: Select "offline" mode;

Step 802: Input the operation state of the capacitor bank; the current operation state of the capacitor branch and the operation state after the switching operation of the capacitor branch can be input to the offline operation state collector 7013 manually;

和

分别计算电容器组的并联谐振点和串联谐振点；操作前的Q_C为第一组电容器的容量，操作后的Q_C为第一组电容器的容量加上第三组电容器组的容量；Step 803: According to the formula

and

Calculate the parallel resonance point and series resonance point of the capacitor bank respectively; _QC before operation is the capacity of the first group of capacitors, and _QC after operation is the capacity of the first group of capacitors plus the capacity of the third group of capacitors;

Step 804: Harmonic current analysis; judging whether the content of each harmonic current exceeds 5%;

Step 805: Calculation of the resonance point; first perform the warning level of the resonance point, round the resonance point to obtain an integer k, subtract the resonance point from the integer k and the integer k+1 respectively, and then take the absolute value to obtain the value n, that is, when a certain resonance point falls on the nearest integer harmonic to the resonance point, if the value n is between 0.-0.1, the warning level is high; if the value n is between 0.1-0.15, the warning level is is low, if the value n is greater than 0.15, no warning will be issued;

Step 806: offline resonance point evaluation; if the value n is between 0-0.1, the warning level is high; if the value n is between 0.1-0.15, the warning level is low; if the value n is greater than 0.15, no warning is given;

Step 807: In the case of reaching the resonance warning, output the number of resonance points, resonance type and resonance warning level; in the case of not reaching the resonance warning, the output warning result is empty.

In the "online" mode of C1, analyze the resonance warning situation of the capacitor bank out of operation.

Assuming that QF1 and QF3 are in the closed position, that is, the first group of capacitors C1 and the third group of capacitors C3 are put into operation, and the bus tie circuit breaker QF12 is in the disconnected position, the third group of capacitors C3 needs to be taken out of operation; analyze in "online" mode For the resonance warning situation caused by this operation, the data to be collected is shown in Figure 9;

The sequence of operating the C3 capacitor bank to exit operation is: disconnect QF3-disconnect QS32-disconnect QS31; at this time, the online or offline state discriminator 706 can know that the displacement of the C3 capacitor has taken place by judging that the position of QF3 has changed. Start the online state quantity signal collector 7011, the steps are as follows:

Step 901: Select "online" mode;

Step 902: By judging that the position of QF3 has changed, it can be known that the operating state of the third group of capacitors may have changed;

和

分别计算电容器组的并联谐振点和串联谐振点；操作前的Q_C为第一组电容器加上第三组电容器组的容量，操作后的Q_C为第一组电容器的容量；Step 903: According to the formula

and

Calculate the parallel resonance point and series resonance point of the capacitor bank respectively; the Q _C before operation is the capacity of the first group of capacitors plus the third group of capacitors, and the Q _C after operation is the capacity of the first group of capacitors;

Step 904: Harmonic current analysis; judging whether the content of each harmonic current exceeds 5%;

Step 905: Calculation of the resonance point; first, carry out the warning level of the resonance point, round the resonance point to obtain an integer k, subtract the resonance point from the integer k and the integer k+1 respectively, and then take the absolute value to obtain the value n, that is, when a certain resonance point falls on the nearest integer harmonic to the resonance point, if the value n is between 0.-0.1, the warning level is high; if the value n is between 0.1-0.15, the warning level is is low, if the value n is greater than 0.15, no warning will be issued;

Step 906: resonance point evaluation; if the value n is between 0-0.1, the warning level is high; if the value n is between 0.1-0.15, the warning level is low; if the value n is greater than 0.15, no warning is given;

Step 907: On-line resonance evaluation; divide the resonance warning level according to the calculation result of the resonance point and the harmonic current content rate: (1) When the harmonic current content rate is greater than or equal to 5%, and the resonance level is "high" , a red warning is issued; (2) when the harmonic current content rate is greater than or equal to 5%, and the resonance level is "low", a yellow warning is issued; (3) when the harmonic current content rate is less than 5%, and the resonance level is When it is "high", a yellow warning will be issued; (4) no warning will be issued in other cases.

Step 908: In the case of reaching the resonance warning, output the number of resonance points, resonance type and resonance warning level; in the case of not reaching the resonance warning, the output warning result is empty;

In the "offline" mode of C1, analyze the resonance warning situation of the capacitor bank out of operation.

Assuming that QF1 and QF3 are in the closed position, that is, the first group of capacitors C1 and the third group of capacitors C3 are put into operation, and the bus tie circuit breaker QF12 is in the disconnected position, now it is necessary to take the third group of capacitors C3 out of operation; analyze in "offline" mode For the resonance warning caused by this operation, the data to be collected is shown in Figure 10, and the steps are as follows:

Step 1001: Select "offline" mode;

Step 1002: Input the operation state of the capacitor bank; manually input the current operation state of the capacitor branch circuit and the operation state after the switching operation of the capacitor branch circuit;

和

分别计算电容器组的并联谐振点和串联谐振点；操作前的Q_C为第一组电容器加上第三组电容器组的容量，操作后的Q_C为第一组电容器的容量；Step 1003: According to the formula

and

Calculate the parallel resonance point and series resonance point of the capacitor bank respectively; the Q _C before operation is the capacity of the first group of capacitors plus the third group of capacitors, and the Q _C after operation is the capacity of the first group of capacitors;

Step 1004: Harmonic current analysis; judging whether the content of each harmonic current exceeds 5%;

Step 1005: Calculation of the resonance point; first perform the warning level of the resonance point, round the resonance point to obtain an integer k, subtract the resonance point from the integer k and the integer k+1 respectively, and then take the absolute value to obtain the value n, that is, when a certain resonance point falls on the nearest integer harmonic to the resonance point, if the value n is between 0.-0.1, the warning level is high; if the value n is between 0.1-0.15, the warning level is is low, if the value n is greater than 0.15, no warning will be issued;

Step 1006: offline resonance point evaluation; if the value n is between 0-0.1, the warning level is high; if the value n is between 0.1-0.15, the warning level is low; if the value n is greater than 0.15, no warning is given;

Step 1007: In the case of reaching the resonance warning, output the number of resonance points, resonance type and resonance warning level; in the case of not reaching the resonance warning, the output warning result is empty.

Each embodiment in this specification is described in a progressive manner, the same and similar parts of each embodiment can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device or system embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and for relevant parts, refer to part of the description of the method embodiments.

It should be noted that in this article, relative terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply these No such actual relationship or order exists between entities or operations. Furthermore, the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus comprising a set of elements includes not only those elements, but also includes elements not expressly listed. other elements of or also include elements inherent in such a process, method, article, or device. Without further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising said element.

The above descriptions are only specific embodiments of the present invention, so that those skilled in the art can understand or implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

The foregoing is only a specific embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, some improvements and modifications can also be made without departing from the principle of the present invention. It should be regarded as the protection scope of the present invention.

Claims (10)

1. A resonance warning system for capacitor switching, characterized in that it is used in a power system, and the power system includes: a high-voltage bus, a low-voltage bus, and a plurality of capacitors electrically connected to the low-voltage bus through capacitor branches; Wherein, the low-voltage bus includes multiple low-voltage bus sections, adjacent low-voltage bus sections are connected by low-voltage bus tie circuit breakers, and capacitors electrically connected to the same low-voltage bus section form a capacitor bank; circuit breakers, The disconnector on the upper side of the circuit breaker, the disconnector on the lower side of the circuit breaker, and the current transformer; the resonance early warning system for capacitor switching includes: Switching state discriminators electrically connected to the circuit breaker of the capacitor branch corresponding to all capacitors in the same capacitor bank, the isolating switch on the upper side of the circuit breaker, and the isolating switch on the lower side of the circuit breaker are used to judge the switching state of each capacitor branch Whether there is a change, wherein, the capacitor branches corresponding to all the capacitors include the capacitor branch in the capacitor bank where the capacitor to be monitored and the parallel capacitor paralleled with the capacitor to be monitored are located; A resonance point evaluation parameter retrieval module electrically connected to the switching state discriminator and each capacitor branch, used to obtain the switching state change if the switching state discriminator determines that the switching state changes Evaluation parameters of the resonance points of the front and rear and each capacitor branch; A resonance point calculator electrically connected to the resonance point evaluation parameter retrieval module, used to evaluate the parallel resonance point and the series resonance point of the capacitor to be monitored according to the resonance point evaluation parameter; wherein, the resonance point evaluation The parameters include: the capacitor capacity, capacitive reactance value, reactance value, series reactance rate and short-circuit capacity of the capacitor to be monitored and the capacitor branch where the parallel capacitor connected to the capacitor to be monitored is located; The step of evaluating the parallel resonance point and the series resonance point of the capacitor to be monitored according to the resonance point evaluation parameters includes: According to the formula

and

Calculate the parallel resonance point and series resonance point of the capacitor bank respectively; in the formula, n ₁ is the parallel resonance point, n ₂ is the series resonance point, Q _C is the capacitor capacity, S _d is the short-circuit capacity of the bus where the parallel capacitor is located, X _C Be the capacitive reactance value of described capacitor bank; X _L is the reactance value of capacitor bank series reactance; K is the series reactance rate; A resonance early warning discriminator electrically connected to the resonance point calculator, the resonance early warning discriminator comprising: A parallel resonance early warning value sub-calculator electrically connected to the resonance point calculator, used to calculate the absolute value of the difference between the parallel resonance point and the adjacent integer before and after, as a parallel resonance early warning value; A series resonance warning value sub-calculator electrically connected to the resonance point calculator, used to calculate the absolute value of the difference between the series resonance point and the adjacent integer before and after, respectively, as a series resonance warning value; and, A resonance warning level sub-discriminator electrically connected to the parallel resonance warning value sub-calculator and the series resonance warning value sub-calculator, for judging where the parallel resonance warning value and the series resonance warning value are located. Resonance warning level; An early warning signal alarm electrically connected to the resonance early warning discriminator is used to give a resonance early warning to the capacitor to be monitored according to the resonance early warning level. 2. The resonance early warning system of capacitor switching according to claim 1, further comprising: An online or offline state discriminator, used to judge whether the capacitor to be monitored is in the online state or in the offline state; The switching state discriminator includes an online state quantity signal collector electrically connected to the online or offline state discriminator, and is used to collect switches related to the capacitor to be monitored if the capacitor to be monitored is in an online state. The state quantity signal of the device, wherein the state quantity signal includes: the auxiliary contact signal of the circuit breaker on each capacitor branch, the auxiliary contact signal of the disconnector on the upper side or the lower side of the circuit breaker, and the auxiliary contact signal of the low-voltage bus tie circuit breaker Contact signal; The online switching state change discriminator electrically connected to the online state quantity signal collector is used to judge whether the state quantity signals of the same switching device at adjacent sampling times in the capacitor bank are consistent, if the state quantity signals are inconsistent , it is determined that the switching state has changed; or, The switching state discriminator includes an offline operating state collector electrically connected to the online or offline state discriminator, and is used to obtain the current sampling time of each capacitor branch in the capacitor bank when the capacitor is in an offline state. The operating status of the capacitor and the operating status of the capacitor where the switching operation of the capacitor branch occurs; The offline switching state change discriminator electrically connected to the offline running state collector is used to judge whether the running state of the capacitor branch is consistent before and after the switching operation of the capacitor branch, and if not, determine whether the switching state of the capacitor branch is consistent. state changes. 3. The resonance early warning system of capacitor switching according to claim 2, further comprising: A harmonic current analyzer electrically connected to the on-line or off-line state discriminator and the current transformers on each capacitor branch, for if the on-line or off-line state discriminator determines that the capacitor to be monitored is in an on-line state, Use the current transformer on each capacitor branch to obtain the harmonic current content rate; The resonance early warning discriminator further includes: a harmonic current content rate comparator electrically connected to the harmonic current analyzer, specifically for comparing the magnitude relationship between the harmonic current content rate and a preset early warning content rate threshold; The early warning signal alarm is also electrically connected to the harmonic current content rate comparator, which is used for resonance early warning according to the magnitude relationship between the harmonic current content rate and the preset content rate threshold, and the resonance early warning value where the parallel resonance early warning value is located. level and the resonance warning level at which the series resonance warning value is located, the resonance warning is performed on the capacitor to be monitored. 4. The resonance early warning system for capacitor switching according to claim 1, wherein the resonance early warning discriminator specifically further includes: The warning level division sub-module electrically connected to the resonance warning level sub-discriminator is used to divide the warning value range of the resonance warning level into high warning level, low warning level and no warning level from low to high. 5. The resonance warning system of capacitor switching according to claim 1, further comprising: A resonance change calculator electrically connected to the resonance point calculator, used to calculate the amount and rate of change of the parallel resonance point and the series resonance point within a predetermined time before and after the switching state changes; The resonance early warning discriminator also includes a resonance early warning value change calculator electrically connected to the resonance change calculator, which is used to calculate the The change amount and change rate of the parallel resonance warning value and the series resonance warning value; The resonance early warning discriminator also includes a resonance early warning change trend prediction module electrically connected to the resonance early warning value change calculator, for according to the variation and rate of change of the parallel resonance early warning value and the series resonance early warning value, Predicting the resonance warning change trend of the capacitor to be monitored. 6. A resonance early warning method for capacitor switching, characterized in that it comprises: Judging whether the switching state of the capacitor to be monitored in the same capacitor bank and the capacitor branch where the parallel capacitor paralleled with the capacitor to be monitored is located changes; If the switching state changes, the resonance point evaluation parameters of each capacitor branch before and after the switching state change are obtained; According to the resonance point evaluation parameter, evaluate the parallel resonance point and the series resonance point of the capacitor to be monitored; wherein, the resonance point evaluation parameter includes: the capacitor to be monitored and a parallel capacitor connected in parallel with the capacitor to be monitored Capacitor capacity, capacitance value, reactance value, series reactance rate and short-circuit capacity of the capacitor branch where it is located; The step of evaluating the parallel resonance point and the series resonance point of the capacitor to be monitored according to the resonance point evaluation parameters includes: According to the formula

and

Calculate the parallel resonance point and series resonance point of the capacitor bank respectively; in the formula, n ₁ is the parallel resonance point, n ₂ is the series resonance point, Q _C is the capacitor capacity, S _d is the short-circuit capacity of the bus where the parallel capacitor is located, X _C Be the capacitive reactance value of described capacitor bank; X _L is the reactance value of capacitor bank series reactance; K is the series reactance rate; Calculate the absolute value of the difference between the parallel resonance point and the adjacent integer before and after, as the parallel resonance warning value, and calculate the absolute value of the difference between the series resonance point and the adjacent integer before and after, respectively, as the series resonance point Resonance warning value; judging the resonance warning levels at which the parallel resonance warning value and the series resonance warning value are respectively located; A resonance warning is performed on the capacitor to be monitored according to the resonance warning level. 7. The resonance warning method for capacitor switching according to claim 6, further comprising: judging whether the capacitor to be monitored is in an online state or in an offline state; If the capacitor to be monitored is in the online state, then collect the state quantity signal of the switching device related to the capacitor to be monitored; wherein, the state quantity signal includes: the auxiliary contact signal of the circuit breaker on each capacitor branch, the circuit breaker Auxiliary contact signal of upper or lower side isolating switch and auxiliary contact signal of low-voltage bus tie circuit breaker; Judging whether the state quantity signals of the same switching device at adjacent sampling moments in the capacitor bank are consistent; If the state quantity signals are inconsistent, it is determined that the switching state has changed; or, If the capacitor is in an offline state, then obtain the operating state of each capacitor branch in the capacitor bank at the current sampling time and the operating state of the capacitor where the switching operation of the capacitor branch occurs; Judging whether the operation status of the capacitor branch is consistent before and after the switching operation of the capacitor branch occurs; If the operating states of the capacitor branches are inconsistent, it is determined that the switching state has changed. 8. The resonance warning method for capacitor switching according to claim 7, further comprising: If the capacitor to be monitored is in the online state, then use the current transformer on each capacitor branch to obtain the harmonic current content rate; Comparing the magnitude relationship between the harmonic current content rate and the preset warning content rate threshold; According to the size relationship between the harmonic current content rate and the preset warning content rate threshold, the resonance warning level where the parallel resonance warning value is located, and the resonance warning level where the series resonance warning value is located, the capacitor to be monitored is monitored. Resonance warning. 9. The resonance early warning method for capacitor switching according to claim 6, wherein judging the resonance early warning level at which the parallel resonance early warning value and the series resonance early warning value are located comprises: The range of the absolute value of the difference between each resonance point and the adjacent integers before and after is taken as the range of the early warning value; The range of early warning values is divided into high early warning level, low early warning level and no early warning level from low to high. 10. The resonance warning method for capacitor switching according to claim 6, further comprising: Calculating the change amount and change rate of the parallel resonance point and the series resonance point within a predetermined time before and after the switching state changes; calculating the change amount and change rate of the parallel resonance warning value and the series resonance warning value according to the change amount and change rate of the parallel resonance point and the series resonance point; According to the variation and rate of change of the parallel resonance warning value and the series resonance warning value, the resonance warning variation trend of the capacitor to be monitored is predicted.

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