CN113176470B - Fast switching device for limiting short-circuit current direct-current component of power system and current limiting method - Google Patents

Abstract

The invention discloses a fast switching device for limiting the DC component of short-circuit current in a power system, which comprises a fast vacuum circuit breaker, a compensating capacitor and a lightning arrester, and the fast vacuum circuit breaker, the compensating capacitor and the lightning arrester are connected in parallel. The device can solve the problems that a power system presents a high DC component and the DC component decays slowly when a short-circuit fault occurs in an asymmetrical short-circuit current. When the power system is running normally, the fast vacuum circuit breaker is closed, and the compensation capacitor and arrester are short-circuited; when an asymmetric short-circuit current is detected, the compensation capacitor and arrester are quickly put into the system circuit, and the compensation capacitor can reduce the X/R ratio. Thereby reducing the DC component of the short-circuit current in the system, enabling the high-voltage circuit breaker in operation to smoothly break the asymmetric short-circuit fault, and reducing the harm caused by the asymmetric short-circuit fault to the safe and stable operation of the power grid. The arrester can protect the compensation capacitor and prevent the short-circuit current from affecting the compensation Capacitor damage.

Description

Fast Switching Device and Current Limiting Method for Limiting DC Component of Short Circuit Current in Power System

technical field

The invention relates to the technical field of power transmission and transformation equipment, in particular to a fast switching device and a current limiting method for limiting the DC component of short-circuit current in a power system.

Background technique

With the development of the power system and the continuous expansion of the grid scale, the connection between power sources is getting closer and closer, and the problem of excessive short-circuit current in power and load-intensive areas is highlighted. The short-circuit current of the power system exceeds the standard, which is not only reflected in the expected short-circuit current exceeding the rated short-circuit breaking current level of the circuit breaker, but also in the percentage of the DC component of the short-circuit current DC component exceeding the rated asymmetric short-circuit breaking current of the circuit breaker. The increase of system capacity and the increase of load X/R ratio cause the short-circuit fault of the system to present the characteristics of large short-circuit current and high DC component, which significantly affects the breaking performance of high-voltage circuit breakers in operation and seriously threatens the safe and stable operation of the power grid. It is an unavoidable major technical and economic problem that restricts the rapid development of contemporary power grids.

At present, power grids at all levels in many regions of the country are facing the above-mentioned problem of excessive short-circuit current. Such as Ningxia Power Grid, Xinjiang Power Grid, Jiangxi Power Grid, Shanghai Power Grid, Guangzhou Power Grid and other 220kV and above systems, the effective value of the short-circuit current even exceeds 79kA, and the DC component decay time constant even exceeds 150ms. However, the maximum short-circuit breaking current of 252kV and above high-voltage circuit breakers in operation in the existing system is 63kA. The decay time constant of the DC component of the current is 120ms.

At present, there is a lack of scientific basis for the evaluation of the asymmetrical short-circuit current breaking performance of high-voltage circuit breakers in operation. The selection, maintenance and performance evaluation of high-voltage circuit breakers in operation for 220kV and above transmission systems still mainly focus on the rated electrical parameters and mechanical characteristic parameters of the circuit breakers. During the operation of the power grid, the high decay time constant of the short-circuit fault current causes the percentage of the DC component of the circuit breaker to break at the moment of breaking, which is often higher than the percentage of the DC component of the rated asymmetric short-circuit breaking current, resulting in the hidden danger of the breaking failure of the circuit breaker. At this stage, the research on the influence mechanism of the asymmetric short-circuit current DC component on the breaking performance of high-voltage circuit breakers is still very scarce, and the evaluation of the breaking performance of high-voltage circuit breakers in operation lacks scientific basis.

At this stage, there is still a lack of economical and reliable control measures for short-circuit current exceeding the standard. The breaking performance of high-voltage circuit breakers in operation is gradually difficult to meet the requirements of large short-circuit current and high DC component breaking conditions, resulting in the power grids at all levels being forced to adopt short-circuit current exceeding control measures, mainly including: power grid partition operation, main transformer split operation, line Install series reactance, extend transmission lines, etc. The divisional operation of the power grid and the split operation of the main transformer busbar can significantly reduce the short-circuit current level and the DC component level, but the reliability of the system operation is easily threatened; adding series reactance to the line and extending the transmission line can also significantly limit the short-circuit current of the system , however, additional high investment in equipment is required.

In general, the increase of system capacity and the increase of load X/R ratio cause the short-circuit fault of the system to present the characteristics of large short-circuit current and high DC component, which significantly affects the breaking performance of high-voltage circuit breakers in operation and seriously threatens the power grid. Safe and stable operation.

Contents of the invention

In view of this, it is necessary to provide a fast switching device that limits the DC component of the short-circuit current in the power system.

It is also necessary to provide a current limiting method for limiting the DC component of the short-circuit current in the power system.

A fast switching device for limiting the DC component of short-circuit current in a power system includes a fast vacuum circuit breaker, a compensation capacitor, and a lightning arrester, and the fast vacuum circuit breaker, the compensation capacitor, and the lightning arrester are connected in parallel.

Preferably, the compensation capacitor is a power capacitor with resistance to short-circuit current impact.

Preferably, the capacitive reactance of the compensation capacitor is determined by the following formula:

Among them, R is the system resistance when the maximum DC component short-circuit current occurs in the system, the unit is Ω; T _r is the system relay protection exit time, the unit is ms; T _op is the circuit breaker opening time, the unit is ms; X _L is the inductive reactance of the system when the maximum DC component short-circuit current occurs, in Ω; X _C is the capacitive reactance of the compensation capacitor, in Ω; dc% is the maximum breaking DC component percentage of the circuit breaker.

A current limiting method for limiting the DC component of short-circuit current in a power system comprises the following steps:

Step S001, connecting the fast switching device for limiting the DC component of the short-circuit current of the power system in series with the circuit breaker, and the fast vacuum circuit breaker and the circuit breaker are in the closing state;

Step S002, when a short-circuit fault with a high DC component occurs in the power system, the fast vacuum circuit breaker breaks the short-circuit current within the first three quarters of the wavelength of the short-circuit current, and transfers it to the branch where the compensation capacitor is located, and the compensation capacitor will short-circuit The DC component of the current is suppressed to the range of the DC component that the circuit breaker can break, and at the same time, the arrester limits the voltage when the short-circuit current flows through the compensation capacitor;

Step S003, when the short-circuit current flowing through the circuit breaker is less than the maximum short-circuit breaking current of the circuit breaker, the circuit breaker performs breaking operation on the power system.

Preferably, in step S002, the time for the compensation capacitor to withstand the impact of short-circuit power is the time interval from when the fast vacuum circuit breaker breaks the short-circuit current to when the circuit breaker breaks the short-circuit current.

Preferably, the time interval between the quick vacuum circuit breaker breaking the short-circuit current and the circuit breaker breaking the short-circuit current is 30-40 ms.

Preferably, the compensation capacitor is a power capacitor with resistance to short-circuit current impact.

Preferably, the capacitive reactance of the compensation capacitor is determined by the following formula:

Among them, R is the system resistance when the maximum DC component short-circuit current occurs in the system, the unit is Ω; T _r is the system relay protection exit time, the unit is ms; T _op is the circuit breaker opening time, the unit is ms; X _L is the inductive reactance of the system when the maximum DC component short-circuit current occurs, in Ω; X _C is the capacitive reactance of the compensation capacitor, in Ω; dc% is the maximum breaking DC component percentage of the circuit breaker.

Preferably, the arrester is a zinc oxide valve group, and the residual voltage of the arrester is 1.2-1.5 times that of the compensation capacitor.

Preferably, a current limiting method for limiting the DC component of short-circuit current in a power system includes the following steps:

Step S004, when the short-circuit fault of the power system is removed, during the reclosing operation of the circuit breaker, it is judged whether the short-circuit fault is a temporary fault, and at the same time, it is judged whether the DC component of the short-circuit current of the power system exceeds the limit that the circuit breaker can open. The maximum DC component of the break;

Step S005, if the short-circuit fault is a temporary fault, and the DC component of the short-circuit current in the power system exceeds the maximum DC component that the circuit breaker can break, then the fast vacuum circuit breaker opens before the circuit breaker to suppress the DC component of the short-circuit current. weight;

In step S006, the line circuit breaker is opened, and after the short-circuit current is broken, the fast vacuum circuit breaker performs closing operation again within 10 ms.

Beneficial effects: the invention discloses a fast switching device for limiting the DC component of short-circuit current in a power system, which includes a fast vacuum circuit breaker, a compensation capacitor, and a lightning arrester, and the fast vacuum circuit breaker, the compensation capacitor, and the lightning arrester are connected in parallel. The device can solve the problems of high DC component and slow decay of the DC component when a short-circuit fault occurs in an asymmetrical short-circuit current in the power system. When the power system is running normally, the fast vacuum circuit breaker is closed, and the compensation capacitor and arrester are short-circuited; when an asymmetric short-circuit current is detected, the compensation capacitor and arrester are quickly put into the system circuit, and the compensation capacitor can reduce the X/R ratio. Thereby reducing the DC component of the short-circuit current in the system, making the high-voltage circuit breaker in operation smoothly break the asymmetric short-circuit fault, and reducing the harm caused by the asymmetric short-circuit fault to the safe and stable operation of the power grid. The arrester can protect the compensation capacitor and prevent the short-circuit current from affecting the compensation Capacitor damage. The invention also discloses a method for limiting the current of the circuit breaker through the current limiting device. In the method, through the cooperation of the fast vacuum circuit breaker and the line circuit breaker, the reliability of the circuit breaker of the power system is improved, and the stability of the power supply of the power system is also improved.

Description of drawings

Fig. 1 is a structural schematic diagram of a fast switching device for limiting the DC component of a short-circuit current in a power system according to the present invention.

In the figure: a fast switching device 10 for limiting the DC component of the short-circuit current in the power system, a fast vacuum circuit breaker 20 , a compensation capacitor 30 , a lightning arrester 40 , and a circuit breaker 50 .

Detailed ways

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings that need to be used in the embodiments. Obviously, the accompanying drawings in the following description are some embodiments of the present invention. Ordinary technicians can also obtain other drawings based on these drawings on the premise of not paying creative work.

Please refer to FIG. 1 , the fast switching device 10 for limiting the DC component of the short-circuit current in the power system includes a fast vacuum circuit breaker 20, a compensation capacitor 30, and a lightning arrester 40, and the fast vacuum circuit breaker 20, the compensation capacitor 30, and the lightning arrester 40 are connected in parallel.

Because the fast switching device 10 for limiting the DC component of the short-circuit current in the power system does not have high requirements on the technical indicators of the fast vacuum circuit breaker 20, the compensation capacitor 30, and the lightning arrester 40, and its installation process only needs to install the switch shown in the present invention The device and the circuit breaker 50 can be connected in series, so it has the advantages of convenient installation and low manufacturing cost. At the same time, the maintenance process of the device of the present invention only needs to detect whether the fast vacuum circuit breaker 20 can operate reliably, whether the insulation in the compensation capacitor 30 is damaged, and whether the arrester 40 is invalid, so its overall operation and maintenance is simple. Accordingly, the overall economic cost of the fast switching device 10 for limiting the DC component of the short-circuit current in the power system according to the present invention is much lower than the cost of replacing the circuit breaker 50 .

Further, the compensation capacitor 30 is a power capacitor capable of resisting short-circuit current impact.

Further, the capacitive reactance of the compensation capacitor 30 is determined by the following formula:

Among them, R is the system resistance when the maximum DC component short-circuit current occurs in the system, the unit is Ω; T _r is the system relay protection exit time, the unit is ms; T _op is the circuit breaker 50 opening time, the unit is ms; X _L is the inductance of the system when the maximum DC component short-circuit current occurs, in Ω; X _C is the capacitive reactance of the compensation capacitor 30, in Ω; dc% is the maximum breaking DC component percentage of the circuit breaker 50.

The current limiting method for limiting the DC component of the short-circuit current in the power system includes the following steps:

Step S001, connecting the fast switching device 10 for limiting the DC component of the short-circuit current of the power system in series with the circuit breaker 50, and the fast vacuum circuit breaker 20 and the circuit breaker 50 are in the closing state;

Step S002, when a short-circuit fault with a high DC component occurs in the power system, the fast vacuum circuit breaker 20 breaks the short-circuit current within the first three quarters of the wavelength of the short-circuit current, and transfers it to the branch where the compensation capacitor 30 is located. 30 suppresses the DC component of the short-circuit current to a range within which the circuit breaker 50 can break the DC component, and at the same time, the lightning arrester 40 limits the voltage when the short-circuit current flows through the compensation capacitor 30;

Step S003 , when the short-circuit current flowing through the circuit breaker 50 is smaller than the maximum short-circuit breaking current of the circuit breaker 50 , the circuit breaker 50 performs breaking operation on the power system.

The fast vacuum circuit breaker 20 has a lower rated voltage than the line circuit breaker 50, has the function of short-circuit fault current zero-crossing detection and reclosing, and can automatically complete the opening and short-circuit current without relying on the instructions of the system relay protection. break.

At the same time, after the fast vacuum circuit breaker 20 detects a short-circuit current with a high DC component, it can complete the expected zero-crossing point of the short-circuit current with a relatively high DC component within a very short time after the short-circuit fault occurs, and adopts phase-controlled short-arc opening Breaking technology, complete short-circuit current breaking and transfer at the zero-crossing point of the first large half-wave of asymmetrical short-circuit current.

The lightning arrester 40 is used to suppress the overvoltage of the fast vacuum circuit breaker 20 and the compensation capacitor 30 , so as to protect the compensation capacitor 30 , and its residual voltage is determined according to the maximum overvoltage level that the compensation capacitor 30 can withstand.

In a preferred embodiment, the parallel branch of fast vacuum circuit breaker 20, compensation capacitor 30, and arrester 40 can be installed on an insulating platform, and then electrically connected in series with circuit breaker 50, and the rated voltage of the insulating platform should have Same rated voltage level as circuit breaker 50.

After the line circuit breaker 50 is connected with the device, the power system can avoid the problem of large-scale replacement of circuit breakers due to insufficient breaking of the DC component. Since the breakout voltage of the quick circuit breaker is only the terminal voltage of the compensation capacitor 30, its breakout withstand voltage level can be much lower than the rated voltage level of the operating line circuit breaker 50 in series with it. At the same time, due to the reduction of the break pressure level of the fast switch, the present invention has the remarkable characteristics of simple structure, small occupied area, and low manufacturing cost.

In the process of suppressing the DC component of the short-circuit current, since the compensation capacitor 30 needs to flow a short-circuit current with a relatively high DC component, the compensation capacitor 30 is required to have higher peak value and short-term withstand current performance. Since the opening time of the line circuit breaker 50 is longer than that of the fast vacuum circuit breaker 20, the time for the compensation capacitor 30 to withstand the impact of short-circuit power is the time interval from when the fast circuit breaker breaks the short-circuit current to when the line breaker 50 breaks the system short-circuit power flow, Preferably it is 30-40ms.

Further, the compensation capacitor 30 is a power capacitor with anti-short-circuit current impact to offset the excessive DC component of the short-circuit current caused by the inductive reactance of the line, thereby suppressing the DC component of the short-circuit current to a DC component that the circuit breaker 50 can break within range.

The capacitive reactance of the compensation capacitor 30 is determined according to the maximum DC component of the short-circuit current that may occur in the system and the maximum DC component that the circuit breaker can break, that is:

Among them, R is the system resistance when the maximum DC component short-circuit current occurs in the system, the unit is Ω; T _r is the system relay protection exit time, the unit is ms; T _op is the circuit breaker 50 opening time, the unit is ms; X _L is the inductance of the system when the maximum DC component short-circuit current occurs, in Ω; X _C is the capacitive reactance of the compensation capacitor 30, in Ω; dc% is the maximum breaking DC component percentage of the circuit breaker 50.

Further, the arrester 40 is a zinc oxide valve group, which is used to suppress the overvoltage of the fast vacuum circuit breaker 20 and the compensation capacitor 30, so as to protect the compensation capacitor 30, and its residual voltage depends on the tolerance of the compensation capacitor 30 The maximum overvoltage level is determined. Preferably, the residual voltage of the arrester 40 is 1.2-1.5 times that of the compensation capacitor 30 .

Further, the current limiting method for limiting the DC component of the short-circuit current in the power system includes the following steps:

Step S004, when the short-circuit fault of the power system is removed, during the reclosing operation of the circuit breaker 50, it is judged whether the short-circuit fault is a temporary fault, and at the same time, it is judged whether the DC component of the short-circuit current of the power system exceeds that of the circuit breaker 50 The maximum DC component that can be broken;

Step S005, if the short-circuit fault is a temporary fault, and the DC component of the short-circuit current in the power system exceeds the maximum DC component that the circuit breaker 50 can break, then the fast vacuum circuit breaker 20 is opened before the circuit breaker 50 to suppress the short circuit DC component of current;

In step S006, the circuit breaker 50 is opened, and after the short-circuit current is broken, the fast vacuum circuit breaker 20 performs closing operation again within 10 ms.

What is disclosed above is only a preferred embodiment of the present invention, and certainly cannot limit the scope of rights of the present invention with this. Those of ordinary skill in the art can understand the whole or part of the process of realizing the above-mentioned embodiment, and make according to the claims of the present invention The equivalent changes still belong to the scope covered by the invention.

Claims (6)

1. A fast switching device for limiting the short-circuit current DC component of the power system, characterized in that: the fast switching device for limiting the short-circuit current DC component of the power system is connected in series with a circuit breaker, and the fast switch for limiting the short-circuit current DC component of the power system The device includes a fast vacuum circuit breaker, a compensation capacitor, and a lightning arrester, and the fast vacuum circuit breaker, the compensation capacitor, and the lightning arrester are connected in parallel; the compensation capacitor is a power capacitor with resistance to short-circuit current impact, and the capacitive reactance of the compensation capacitor is passed by the following formula Sure:

Among them, R is the system resistance when the maximum DC component short-circuit current occurs in the system, the unit is Ω; T _r is the system relay protection exit time, the unit is ms; T _op is the circuit breaker opening time, the unit is ms; X _L is the inductive reactance when the maximum DC component short-circuit current occurs in the system, in Ω; X _C is the capacitive reactance of the compensation capacitor, in Ω; dc% is the maximum breaking DC component percentage of the circuit breaker. 2. A current-limiting method for limiting the DC component of the short-circuit current in a power system, characterized in that: the current-limiting method for limiting the DC component of the short-circuit current in the power system is applied to the fast switch for limiting the DC component of the short-circuit current in the power system claimed in claim 1 device, including the following steps: Step S001, connecting the fast switch device for limiting the DC component of the short-circuit current of the power system described in claim 1 in series with the line circuit breaker, and the fast vacuum circuit breaker and the line circuit breaker are in the closing state; Step S002, when a short-circuit fault with a high DC component occurs in the power system, the fast vacuum circuit breaker breaks the short-circuit current within the first three quarters of the wavelength of the short-circuit current, and transfers it to the branch where the compensation capacitor is located, and the compensation capacitor will short-circuit The DC component of the current is suppressed to the range of the DC component that the circuit breaker can break, and at the same time, the arrester limits the voltage when the short-circuit current flows through the compensation capacitor; Step S003, when the short-circuit current flowing through the circuit breaker is less than the maximum short-circuit breaking current of the circuit breaker, the circuit breaker performs breaking operation on the power system. 3. The current-limiting method for limiting the DC component of short-circuit current in power system as claimed in claim 2, characterized in that: in step S002, the time for the compensation capacitor to withstand the impact of short-circuit power is when the fast vacuum circuit breaker breaks the short-circuit current to the line circuit breaker Time interval for breaking short-circuit current. 4. The current-limiting method for limiting the DC component of short-circuit current in a power system according to claim 3, wherein the time interval between the breaking of the short-circuit current by the fast vacuum circuit breaker and the breaking of the short-circuit current by the line circuit breaker is 30-40 ms. 5. The current-limiting method for limiting the DC component of short-circuit current in power system as claimed in claim 2, characterized in that: the arrester is a zinc oxide valve group, and the residual voltage value of the action of the arrester is 1.2-1.5 times that of the compensation capacitor . 6. the current-limiting method of limiting power system short-circuit current DC component as claimed in claim 2, is characterized in that: the current-limiting method of limiting power system short-circuit current DC component comprises the following steps: Step S004, when the short-circuit fault of the power system is removed, during the reclosing operation of the circuit breaker, it is judged whether the short-circuit fault is a temporary fault, and at the same time, it is judged whether the DC component of the short-circuit current of the power system exceeds the limit that the circuit breaker can open. The maximum DC component of the break; Step S005, if the short-circuit fault is a temporary fault, and the DC component of the short-circuit current in the power system exceeds the maximum DC component that the circuit breaker can break, then the fast vacuum circuit breaker opens before the circuit breaker to suppress the DC component of the short-circuit current. weight; In step S006, the line circuit breaker is opened, and after the short-circuit current is broken, the fast vacuum circuit breaker performs closing operation again within 10 ms.

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