CN103036222A - Control strategy optimization method for full container load (FCL) device control and protection system - Google Patents

Abstract

The invention relates to a control strategy optimization method for an FCL device control and protection system, which belongs to the field of power supply or power distribution devices. Its feature is to judge the line fault situation by phase separation, and trigger the thyristor and the controllable spark gap GAP by phase separation; the closing command to the bypass circuit breaker BCB is three phases at the same time; when the FCL device is put into operation, its feeder outlet is disabled The line reclosing function of the circuit breaker; when the line current monitoring function in the FCL device control and protection system is used when the line is empty-charged or under low load, the bypass circuit breaker is first locked to the closing position, and then disconnected after the power flow of the line rises. The bypass circuit breaker is opened, and the power flow of the line is used to meet the condition of the thyristor to trigger energy acquisition, so as to ensure that the thyristor is first triggered and turned on when the line fails. It avoids adverse effects on the system caused by asymmetric operation of line parameters for a long time, avoids damage to FCL equipment caused by reclosing again, and improves the safety and reliability of the entire device. It can be widely used in the fields of UHV and EHV power grid operation, power grid dispatching and control.

Description

A control strategy optimization method for the control and protection system of FCL device

technical field

The invention belongs to the field of power supply or power distribution devices, and in particular relates to a control method for a control and protection system of an FCL device.

Background technique

In recent years, with the continuous growth of my country's electricity load, the installed capacity has increased sharply, and the power grid structure has been continuously strengthened. The problem of excessive short-circuit current in the central power grid of some loads has become increasingly serious, endangering the safety and stability of power grid operation, and has become a safe and stable power grid. One of the main concerns of operation.

In order to maintain stable power transmission, fast short-circuit fault protection is very important. A general mechanical circuit breaker needs two or more cycles to cut off the short-circuit current, including the action time of the relay protection, and the fast current limiting device used with the circuit breaker can shorten the fault protection time.

The existing fault current limiter (Fault Current Limiter, FCL) principle is shown in Figure 1, which is mainly composed of reactor L, capacitor C and fast bypass switch K (such as thyristor, spark gap, fast mechanical switch and other types can be used) switch or a combination thereof).

Among them, the power frequency inductive reactance of the reactor L is the same as the capacitive reactance of the capacitor C. Under normal working conditions, the switch K is in the open state (corresponding to the blocking state of the thyristor), the capacitor C and the inductor L are in the power frequency series resonance state, and the total impedance is zero. When a fault is detected, the switch K is quickly closed (corresponding to the rapid conduction of the thyristor), and the capacitor is bypassed, which is equivalent to connecting the inductor L in the line to limit the current.

A FCL device put into practical use is shown in Figure 2. Its main components and functions are as follows:

(1) Current-limiting reactor (FL), which acts as a current-limiting function during a short circuit;

(2) Capacitor bank (C1, C2, C3, C4), which compensates the inductive reactance of the short-circuit current limiter under normal operating conditions; it is quickly bypassed during the system short-circuit;

(3) Thyristor valve, which is the first measure to bypass capacitors. When a short-circuit fault occurs, it will be quickly turned on, bypassing the capacitor bank, so that the reactor can limit the current;

(4) Controllable spark gap (GAP), which is an overvoltage protection device for capacitor banks. In the case of a short-circuit fault, if the thyristor fails to conduct and the voltage of the capacitor bank rises rapidly to a level that endangers the safety of the capacitor, the spark gap can act quickly;

(5) Bypass circuit breaker (BCB), which realizes reliable short-circuiting of capacitors within tens of milliseconds, and also provides means for putting in and out of capacitor banks;

(6) Metal oxide varistors (MOVL, MOV1, MOV2) are one of the necessary measures for overvoltage protection of capacitor banks.

(7) Damping circuit (DL, DR, DG), which limits and damps the discharge current to ensure the safe operation of capacitor banks, thyristor valves, spark gaps, and bypass circuit breakers;

(8) Bypass switch and isolation switch (MBS, DS1, DS2) provide means for system operation and maintenance.

Since the above-mentioned equipment, switches and their labels are all industry standards, their specific working principles and equipment structures will not be described here.

During normal operation, the reactor FL and the capacitor bank (C1, C2, C3, C4) form a series resonance, which has no effect on the system operation. When the system fails, the current flowing through the LC resonant circuit exceeds the set value (line overcurrent protection action), or the current exceeds a certain value and the current rising rate is greater than the set value (line current slope protection action), FCL control protection system It is judged that the system is faulty, and an order is issued to trigger the conduction of the thyristor. At the same time, an order is issued to trigger the spark gap (GAP) and close the bypass circuit breaker (BCB). to limit the current.

The FCL device is equipped with two sets of control and protection systems based on digital signal processors (DSP) and large-scale programmable logic devices with the same function, independent operation and mutual backup. These two sets of control and protection systems are installed in independent screen cabinets, and they do not affect each other during maintenance.

During the actual test, it was found that the operation process of the entire existing FCL control and protection equipment meets the design requirements, but there are some deficiencies in it. The action criterion is wrong, causing the corresponding protection "false action", etc., which affects the safe and stable operation of the entire device.

Contents of the invention

The technical problem to be solved by the present invention is to provide a control strategy optimization method for the control and protection system of FCL devices, which improves and optimizes the control strategy of the entire device according to the specific conditions of the electrical structure of the line. Triggering, to avoid long-term asymmetric operation of line parameters, which will cause adverse effects on the system, adjust the reclosing input conditions of the feeder outlet circuit breaker, to avoid damage to FCL equipment caused by reclosing again, and improve the safety and reliability of the entire device.

The technical solution of the present invention is to provide a method for optimizing the control strategy of the FCL device control and protection system, including that when the system fails, the current flowing through the LC resonant circuit exceeds the first line current monitoring alarm value, or the current exceeds the second line current When the alarm value is monitored and the current rising rate is greater than the slope setting value, the FCL device control and protection system issues an order to trigger the thyristor to conduct, and at the same time issues an order to trigger the spark gap GAP and close the bypass circuit breaker BCB; the capacitor bank is short-circuited, and the FCL device is external It presents pure reactance characteristics and plays the role of limiting current. It is characterized in that the control strategy of the control and protection system of the FCL device is adjusted and optimized according to the following contents:

1-1. Phase-by-phase judgment of line faults, and phase-by-phase triggering of thyristors and controllable spark gap GAP;

1-2. The closing command to the bypass circuit breaker BCB is carried out simultaneously for three phases;

1-3. When the FCL device is put into operation, the line reclosing function of the circuit breaker at the outlet of the feeder is disabled;

1-4. When the line current monitoring function in the FCL device control protection system is used to lock the bypass circuit breaker to the closing position when the line is empty or under low load, and then disconnect the bypass circuit breaker after the line flow rises The device uses the power flow of the line to meet the triggering condition of the thyristor, so as to ensure that the thyristor is first triggered and turned on when the line fails.

Further, the control strategy optimization also includes that when the line is charging, the FCL device is switched on in a resonant manner.

Further, the optimization of the control strategy also includes that the circuit parameters are in an asymmetric mode during the period from the thyristor or GAP single-phase bypass capacitor until the bypass circuit breaker is closed, and the running time in this mode is shortened as much as possible to avoid circuit Directional zero-current protection malfunctions.

Compared with prior art, the advantages of the present invention are:

1. The FCL device adopts the control method of "judging the line fault situation by phase separation, and triggering the thyristor and GAP by phase separation, but the closing command of the bypass circuit breaker is three phases at the same time", which can avoid long-term asymmetrical operation of line parameters on the system Cause adverse effects, and can avoid unreliable trigger conduction of thyristor and GAP;

2. Turn off the bypass circuit breaker after the power flow of the line rises, and use the power flow of the line to meet the triggering condition of the thyristor, so as to ensure that the thyristor is first triggered to conduct when the line fails;

3. When the FCL device is put into operation, the "line reclosing" function of the circuit breaker at the outlet of the feeder where it is located can be disabled to avoid damage to the FCL device caused by reclosure after the line protection action if an internal fault occurs in the FCL device.

Description of drawings

Figure 1 is a schematic diagram of the working principle of FCL;

Fig. 2 is the electrical structure schematic diagram of FCL device;

Figure 3 shows the adjusted and optimized control strategy.

In the figure, FL is a current-limiting reactor, C1, C2, C3, and C4 are capacitors, GAP is a controllable spark gap, BCB is a bypass circuit breaker, MOVL, MOV1, and MOV2 are metal oxide varistors, DL, DR, DG is the damping circuit, MBS is the bypass switch, DS1 is the inlet-side isolation switch, DS2 is the outlet-side isolation switch, ES1 is the inlet-side grounding switch, and ES2 is the outlet-side grounding switch.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

In Figure 1, the FCL device is mainly composed of a reactor L, a capacitor C and a fast bypass switch K.

Among them, the power frequency inductive reactance of the reactor L is the same as the capacitive reactance of the capacitor C. Under normal working conditions, the switch K is in the open state (equivalent to the thyristor in the blocking state), the capacitor C and the inductor L are in the power frequency series resonance state, and the total impedance is zero. When a fault is detected, the switch K is quickly closed (equivalent to the rapid conduction of the thyristor), and the capacitor is bypassed, which is equivalent to connecting the inductor L to the line to limit the current.

In Figure 2, during normal operation, the reactor FL and the capacitor bank (C1, C2, C3, C4) form a series resonance, which has no effect on the system operation. When the system fails, the current flowing through the LC resonant circuit exceeds the set value (line overcurrent protection action), or the current exceeds a certain value and the current rising rate is greater than the set value (line current slope protection action), FCL control protection system If it is judged that the system is faulty, an order is issued to trigger the conduction of the thyristor, and at the same time, an order is issued to trigger the spark gap (GAP) and close the bypass circuit breaker (BCB). The consequence is to short-circuit the capacitor bank, and the FCL presents a pure reactance characteristic to the outside, which plays a role in limiting the current.

Among them, the conduction time of the thyristor valve is less than 1.5 milliseconds, the GAP time is slightly longer at about 2 milliseconds, and the bypass circuit breaker time is less than 30 milliseconds. The time coordination is: generally, the thyristor is required to act first, and its action speed is fast, but it cannot withstand high current for a long time. The bypass circuit breaker is closed within 30 milliseconds after the thyristor is triggered, and the current is bypassed from the circuit breaker.

Among them, the thyristor is composed of two anti-parallel valve elements, which ensure that the conduction channel can be provided under the forward and reverse current conditions.

GAP is composed of controllable and uncontrollable gaps connected in series. GAP receives the control system signal and actively breaks down the controllable gap through a pulse transformer, causing the breakdown voltage of the entire GAP to drop, driving the breakdown of the main gap, and completing the GAP controllable breakdown function. GAP breakdown requires a certain voltage at both ends, so if the thyristor is turned on (or the bypass circuit breaker is closed), the voltage across the series capacitor decreases, and the GAP will not act.

The DL, DG, DR, TL and other components in the figure form a damping circuit to prevent the device from being damaged due to the instantaneous high current released to the thyristor or GAP during the bypass process of the series capacitor.

MOVL is used to protect the reactor, such as when overvoltage is generated at both ends of the reactor during lightning wave invasion or operation.

The remaining switch blades are used to isolate equipment and bypass equipment to ensure the normal operation of the line.

In Fig. 3, the present invention provides a control strategy optimization method of the FCL device control and protection system, including when the system fails, the current flowing through the LC resonant circuit exceeds the first line current monitoring alarm value, or the current exceeds the second line current When the alarm value is monitored and the current rising rate is greater than the slope setting value, the FCL device control and protection system issues an order to trigger the thyristor to conduct, and at the same time issues an order to trigger the spark gap GAP and close the bypass circuit breaker BCB; the capacitor bank is short-circuited, and the FCL device is external It presents pure reactance characteristics and plays the role of limiting current. The point of the invention is that the control strategy of the control and protection system of the FCL device is also adjusted and optimized according to the following contents:

1-1. Phase-by-phase judgment of line faults, and phase-by-phase triggering of thyristors and controllable spark gap GAP;

1-2. The closing command to the bypass circuit breaker BCB is carried out simultaneously for three phases;

1-3. When the FCL device is put into operation, the line reclosing function of the circuit breaker at the outlet of the feeder is disabled;

1-4. When the line current monitoring function in the FCL device control protection system is used to lock the bypass circuit breaker to the closing position when the line is empty or under low load, and then disconnect the bypass circuit breaker after the line flow rises The device uses the power flow of the line to meet the triggering condition of the thyristor, so as to ensure that the thyristor is first triggered and turned on when the line fails.

Further, the control strategy optimization also includes that when the line is charging, the FCL device is switched on in a resonant manner.

Further, the optimization of the control strategy also includes that the circuit parameters are in an asymmetric mode during the period from the thyristor or GAP single-phase bypass capacitor until the bypass circuit breaker is closed, and the running time in this mode is shortened as much as possible to avoid circuit Directional zero-current protection malfunctions.

After the above expansion and adjustment of the control strategy of the FCL device control and protection system, the A-phase artificial grounding short circuit test was successfully carried out in the XX line of the XX substation. During the fault, the FCL device responded correctly and quickly and successfully reduced the short-circuit current from 10 kA to 8 kA (8 ohms), and the performance of all parameters reached the expected target. It can be seen from the unfolded recording diagram that after the fault occurs, the thyristor valve group is turned on within 1 millisecond, which suppresses the increase of the fault current.

After installing the FCL device, the overvoltage level of the substations on both sides meets the requirements. No abnormal phenomenon was found in the equipment test and inspection, and the body of the complete set of equipment is in good condition and can meet the operation requirements. The commissioning of the FCL complete set of equipment will not cause a significant increase in the level of power frequency electromagnetic field strength, which meets the requirements of relevant standards. Since the site was put into operation, under various loads and weather conditions, the device works normally without any abnormal phenomenon.

The ultra-high voltage fault current limiter can avoid changes to the main network frame of the power grid, effectively suppress the short-circuit current of the power grid, reduce and avoid the investment cost caused by the structural adjustment of the power grid and equipment replacement caused by the short-circuit current exceeding the standard, and is suitable for XX ring network and XX power grid , XX power grid and other short-circuit current suppression has an important demonstration role, and also creates good conditions for the coordinated development of UHV and 500kV power grid.

The invention can be widely used in the fields of ultra-high voltage and ultra-high voltage power grid operation, power grid dispatching and control.

Claims (3)

1. A control strategy optimization method for an FCL device control and protection system, including when the system fails, the current flowing through the LC resonant circuit exceeds the first line current monitoring alarm value, or the current exceeds the second line current monitoring alarm value and the current rises When the rate is greater than the slope setting value, the FCL device control and protection system issues an order to trigger the thyristor to conduct, and at the same time issues an order to trigger the spark gap GAP and close the bypass circuit breaker BCB to short-circuit the capacitor bank. To limit the current, it is characterized in that the control strategy of the control and protection system of the FCL device is adjusted and optimized according to the following contents: 1-1. Phase-by-phase judgment of line faults, and phase-by-phase triggering of thyristors and controllable spark gap GAP; 1-2. The closing command to the bypass circuit breaker BCB is carried out simultaneously for three phases; 1-3. When the FCL device is put into operation, the line reclosing function of the circuit breaker at the outlet of the feeder is disabled; 1-4. When the line current monitoring function in the FCL device control protection system is used to lock the bypass circuit breaker to the closing position when the line is empty or under low load, and then disconnect the bypass circuit breaker after the line flow rises The device uses the power flow of the line to meet the triggering condition of the thyristor, so as to ensure that the thyristor is first triggered and turned on when the line fails. 2. The control strategy optimization method of the FCL device control and protection system according to claim 1, characterized in that said control strategy optimization further includes when the line is charging, the FCL device is turned on in a resonant manner. 3. According to the control strategy optimization method of the FCL device control and protection system according to claim 1, it is characterized in that the control strategy optimization also includes in the thyristor or spark intermittent GAP single-phase bypass capacitor until the bypass circuit breaker is closed in three phases During this period, the line parameters are in an asymmetric mode, and the running time in this mode should be shortened as much as possible to avoid misoperation of the zero-current protection in the line direction.

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