CN116365487A - Protection method and device for hybrid AC filter connection circuit breaker failure - Google Patents

Abstract

The invention belongs to the technical field of UHV/HVDC transmission system protection, and in particular relates to a protection method and device for failure of a hybrid AC filter connection circuit breaker. The action switch of the connection circuit breaker failure protection of the present invention is a double switch, which ensures that the two switches refer to each other and avoids the misidentification of a single switch that is difficult to be found; and according to the feature that the switch usually has a short existence time, When the double input exists for a long time, the connection circuit breaker failure protection is blocked in time to avoid false triggering of the connection circuit breaker failure protection. Moreover, in addition to the criteria corresponding to the three-phase current at the starting resistor, criteria corresponding to the zero-sequence current overcurrent and negative-sequence current overcurrent at the starting resistor are added. Detect whether the fault current exists to improve the sensitivity of the detection results; and the newly added criterion can be blocked by the CT disconnection and the corresponding control word, so that when the criterion fails, the relevant logical judgment steps are omitted and the calculation cost is saved.

Description

Protection method and device for hybrid AC filter connection circuit breaker failure

technical field

The invention belongs to the technical field of UHV/HVDC transmission system protection, and in particular relates to a protection method and device for failure of a hybrid AC filter connection circuit breaker.

Background technique

With the continuous improvement of the status of UHV DC projects in my country's power transmission system, the harmonic problems brought about by them have gradually become prominent. At present, serious harmonics exceeding the standard have appeared around the areas where some DC projects are implemented. The hybrid AC filter HAPF, in which the passive filter PF and the active filter APF are connected in series, meets various compensation requirements, and has gradually become a hot research topic in the field of harmonic suppression, and it is also the development direction of future filtering technology. As shown in Figure 1, a hybrid AC filter (HAPF) includes two parts: a passive AC filter (PF) and an active filter (APF). The APF is connected to the end of the ACF through a switch Q2. In Figure 1, the dashed box The inside is the active filter (that is, the active area of the hybrid AC filter), and the outside of the dotted box is the passive AC filter (that is, the passive area of the hybrid AC filter). The prerequisite for the hybrid AC filter to play a role is that it can be started safely and effectively and put into operation safely; when the hybrid AC filter is started, the starting resistor R0 is put into operation, and after the connecting circuit breaker Q6 is closed, the AC power supply passes through the starting resistor R0 to commutate After the charging is completed, close the starting circuit breaker Q9 connected in parallel with the starting resistor.

During the start-up of the hybrid AC filter, if a ground fault occurs between the start-up resistor R0 and the converter, and at this time the connection circuit breaker Q6 fails to trip, the existing circuit breaker protection device will receive the trip signal It will judge whether the connecting circuit breaker Q6 fails by judging whether the current at the connecting circuit breaker is greater than the current setting value, and if it fails, it will delay and trip the upper-level circuit breaker Q5. However, since the starting resistor is in the input state at this time, the fault current at the connected circuit breaker is relatively small, which is likely to be less than the current setting value for triggering the circuit breaker protection, so that the circuit breaker protection operation will not be triggered, although the fault current Small, it exists for a long time but it is enough to cause permanent damage to the starting resistor; and when the hybrid AC filter is running normally (without starting the resistor), after the fault occurs, the existing protection action except for tripping and disconnecting In addition to the circuit breaker Q6, the starting circuit breaker Q9 will also be tripped to prevent the failure of the connecting circuit breaker Q6 to trip and cause the fault current to damage the converter. When the current is small; directly lowering the current setting value that triggers the protection of the circuit breaker will lead to an increase in false triggering. Therefore, no matter during the start-up or normal operation of the hybrid AC filter, as long as the connection circuit breaker Q6 fails, the existing method of directly judging whether the connection circuit breaker Q6 failure protection is triggered by judging whether the current at the connection circuit breaker is greater than a fixed value Insufficient reliability may lead to the inability to implement the protection action of the connection circuit breaker failure in time, causing the starting resistor to be damaged by the fault current, or prone to false triggering, which affects the operating efficiency of the hybrid AC filter.

Contents of the invention

The purpose of the present invention is to provide a hybrid AC filter connection circuit breaker failure protection method and device, which is used to solve the problem of triggering connection circuit breaker failure protection in the prior art by judging whether the current at the connection circuit breaker is greater than a fixed value Insufficient reliability leads to the inability to timely implement the protection action connected to the failure of the circuit breaker or the problem that it is easy to trigger by mistake.

In order to achieve the above object, the present invention provides a protection method for a hybrid AC filter connected to a circuit breaker failure. The hybrid AC filter is composed of an active filter head end connected to a passive AC filter tail end. Under the following four conditions, after setting the delay time, control the hybrid AC filter connection circuit breaker failure protection action:

Condition 1: The action switch of the connection circuit breaker failure protection is valid;

Condition 2: There is a fault current at the starting resistor;

Condition 3: The high voltage circuit breaker is in the closing position;

Condition 4: The grounding circuit breaker changes from the open position to the closed position;

The connection circuit breaker is a circuit breaker that connects the active filter in the hybrid AC filter to the tail end of the passive AC filter; the starting resistor is a converter connected to the active filter in the hybrid AC filter resistors connected in series; the high-voltage circuit breaker is a circuit breaker that connects the head end of the passive AC filter in the hybrid AC filter to the AC bus bar; the grounding circuit breaker is a passive filter in the hybrid AC filter Grounded circuit breaker.

The beneficial effect of the above-mentioned technical scheme is: the fault protection action in the hybrid AC filter busbar area and the fault protection action in the passive area are confirmed to fail to isolate the fault through the switch-in and switch state, and the work of the fault protection action in the active area is ensured. Therefore, the follow-up judgment and protection of the failure of the connection circuit breaker can be carried out accordingly, so as to avoid false triggering of the failure protection action of the connection circuit breaker of the hybrid AC filter, improve the reliability of the failure protection action of the connection circuit breaker of the hybrid AC filter, and prevent damage to impact on the transmission system.

Further, the action switches connected to the circuit breaker failure protection are double switches, and the two inputs of the action switches connected to the circuit breaker failure protection are the same;

The method of judging whether the valid condition of the active switching input of the connection circuit breaker failure protection is: two switching inputs of the connection circuit breaker failure protection exist at the same time, and the duration of the simultaneous existence of the two switching inputs does not exceed the set duration threshold , then it is judged that the condition that the action switch-in of the connection circuit breaker failure protection is valid is met.

The beneficial effect of the above-mentioned technical solution is that: the action switches connected to the circuit breaker failure protection are double switches, and the quantities of the two switches connected to the circuit breaker failure protection are the same, which is equivalent to setting redundant switches to ensure that both Each switch is a mutual reference to avoid misidentification where a single switch is difficult to be found; and according to the fact that the switch usually has a short existence time, when the double switch exists for a long time, it will be blocked in time to connect the circuit breaker failure protection and send an alarm to avoid When the connection circuit breaker failure protection is triggered by mistake, it also reminds the staff to check and repair in time.

Further, if the CT disconnection locking failure protection logic startup control word is input, and it is determined that the three-phase current at the startup resistor has a CT disconnection, then the way to judge whether the condition of fault current at the startup resistor is satisfied is:

If any one of I _a > I _set , I _b > I _set or I _c > I _set is satisfied, it is determined that the condition of fault current at the starting resistor is satisfied;

Among them, I _a , I _b and I _c are the three-phase currents at the starting resistors respectively; I _set is the threshold value set for the connection circuit breaker failure protection.

Further, if the start control word of the CT disconnection locking failure protection logic is not input, or it is determined that the three-phase current at the starting resistor does not have a CT disconnection, then the method of judging whether the condition of fault current at the starting resistor is met is as follows:

If any one of I _a >I _set , I _b >I _set and I _c >I _set is satisfied, or any one of 3I ₀ >I _0set and I ₂ >I _2set is satisfied, it is determined that the starting resistance is satisfied Conditions for the presence of fault currents;

Among them, I _a , I _b and I _c are the three-phase currents at the starting resistor respectively; I _set is the set phase current threshold; I ₀ and I ₂ are the zero-sequence current and negative-sequence current at the starting resistor respectively; I _0set and I _2set are respectively setting zero-sequence current threshold and negative-sequence current threshold.

The beneficial effect of the above technical solution is: in addition to the criterion corresponding to the three-phase current at the starting resistor, the criterion corresponding to "zero-sequence current overcurrent and negative-sequence current overcurrent at the starting resistor" is added, thus passing A variety of criteria are provided, which can detect the existence of fault current from various aspects to improve the sensitivity of the detection results; and in order to save calculation costs as much as possible, the criterion is controlled by CT disconnection and CT disconnection locking failure protection logic word locked.

Further, the method for judging whether the condition that the high-voltage circuit breaker is in the closing position is satisfied is as follows:

If min(I _ha ,I _hb ,I _hc )>I _YL1 is satisfied, it is determined that the condition that the high-voltage circuit breaker is in the closing position is satisfied;

Among them, min(I _ha , I _hb , I _hc ) is the minimum value among the fundamental RMS values of A-phase, B-phase, and C-phase currents at the head end of the passive AC filter; I _YL1 is the first current constant value; the value range of I _YL1 is related to the rated current at the passive AC filter.

Further, the condition for the grounded circuit breaker to change from the open position to the closed position is as follows: if both the abrupt pulse edge criterion and the steady-state value criterion are met, it is determined that the grounded circuit breaker is changed from the open position to the closed position. the conditions of the location;

Among them, the abrupt pulse edge criterion is: i _da (t)-i _da (t-2T)<kI _e and i _db (t)-i _db (t-2T)<kI _e and i _dc (t)-i _dc (t-2T)<kI _e ;

Among them, i _da (t), i _db (t) and i _dc (t) are the current fundamental RMS values of phase A, phase B, and phase C of the high-voltage circuit breaker at the current sampling moment, and i _da (t-2T) , i _db (t-2T) and i _dc (t-2T) are the fundamental effective values of phase A, phase B, and phase C current at the high-voltage circuit breaker at the sampling time two sampling periods before, and k is greater than 0 The coefficient of , I _e is the rated current at the passive AC filter;

The steady-state value criterion is: min(I _da , I _db , I _dc )>I _YL2 ;

Among them, min(I _da , I _db , I _dc ) is the minimum value of the fundamental effective values of the A-phase, B-phase, and C-phase currents at the head end of the active AC filter, and I _YL2 is the second active current constant value; the value range of I _YL2 is related to the rated current at the passive AC filter.

The beneficial effect of the above-mentioned technical scheme is: the condition for judging that the grounded circuit breaker is changed from the opening position to the closing position is set to satisfy both the abrupt pulse edge criterion and the steady-state value criterion, so as to ensure that no misjudgment occurs as much as possible. In this case, the reliability of the judgment result of the grounding circuit breaker changing from the opening position to the closing position is improved.

Further, the hybrid AC filter connection circuit breaker failure protection action is: tripping the high voltage circuit breaker and the grounding circuit breaker.

Further, when the condition that the grounding circuit breaker is changed from the open position to the closed position is satisfied, if the condition 1, condition 2 and condition 3 are simultaneously met within the set extension time, it is determined that the four conditions are met at the same time .

The beneficial effect of the above technical solution is that it can avoid the situation that the logical judgment result of the fourth condition is out of sync with the logical judgment results of the first condition, the second condition and the third condition, resulting in misjudgment.

Further, the set stretching time is greater than or equal to 1 second.

The present invention also provides a protection device for failure of a hybrid AC filter connected to a circuit breaker, including a collector and a processor. The corresponding current values at the head end of the active filter and the starting resistor, the processor is used to execute program instructions to realize the above-mentioned protection method for the failure of the hybrid AC filter connected to the circuit breaker.

The protection device for the failure of the hybrid AC filter connected to the circuit breaker can achieve the same beneficial effect as the above-mentioned protection method for the failure of the hybrid AC filter connected to the circuit breaker.

Description of drawings

Fig. 1 is the circuit structural representation of hybrid AC filter in the background technology of the present invention;

Fig. 2 is a schematic diagram of the judgment logic for the protection start of the connection circuit breaker failure in the embodiment of the protection method for the connection circuit breaker failure of the hybrid AC filter of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

Embodiment of protection method for hybrid AC filter connection circuit breaker failure:

This embodiment provides a technical solution for a protection method for a hybrid AC filter connected to a circuit breaker failure, as shown in Figure 1, the hybrid AC filter applicable to the protection method in this embodiment consists of an active filter head It is connected to the tail end of the passive AC filter. The active filter corresponds to the active area of the hybrid AC filter in Figure 1. Similarly, the passive AC filter corresponds to the hybrid AC filter in Figure 1. source area; in Figure 1, T4 is the current transformer in the passive area, Q5 is the high-voltage circuit breaker; T5 is the current transformer in the active area; Q6 is the connecting circuit breaker, T7 is the grounding current transformer, and Q7 is the grounding circuit breaker. T6 is the current transformer of the starting circuit, Q9 is the circuit breaker of the starting circuit, G1 is the front ground knife switch connected to the Q6 side of the circuit breaker, G2 is the horizontal double grounding isolating switch, G3 is the horizontal non-grounding isolating switch; R0 is the starting resistor , G4 is the rear ground switch of the branch where the circuit breaker of the starting circuit is located, and PT1 and PT2 are the circuit voltage transformers;

If a fault occurs in the bus area of the hybrid AC filter, usually the protection of the bus area of the hybrid AC filter takes priority and trips the high-voltage circuit breakers Q1, Q2, Q3, Q4, and Q5 to isolate the fault. If the passive AC filter fails, the passive AC filter protection action will trip the high voltage circuit breaker Q3 or Q4. If a fault occurs in the passive area of the hybrid AC filter, the protection of the passive area of the hybrid AC filter will operate, trip the high-voltage circuit breaker Q5, and block the active AC filter at the same time. If the active area of the hybrid AC filter fails, the protection of the active area of the hybrid AC filter will operate. During normal operation, if the active area of the hybrid AC filter fails, the action result is to close Q7 and trip Q6 and Q9. Closing Q7 is to ensure that the passive area of the hybrid AC filter can still work normally; jumping off Q9 is to greatly reduce the fault current after switching on, thereby ensuring the safety of the converter, and the starting resistor itself is not damaged; jumping off Q6 is to In order to cut off the source of the fault current. In the starting process, if the active area of the hybrid AC filter fails, the action result is to close Q7 and jump Q6. If the connecting circuit breaker Q6 fails, it is necessary to trip the upper level circuit breaker Q5. Since a fault occurs during start-up, the fault current is small; while during normal operation, because the protection action not only trips Q6, but also trips Q9, the fault current detected by the failure protection is also small.

Combined with the creative analysis of the above situation, referring to the judgment logic in Figure 2, the protection method for the failure of the hybrid AC filter connection circuit breaker in this embodiment is specifically: when the following four conditions are met at the same time, after setting the delay time , to control the hybrid AC filter connection circuit breaker failure protection action, and the action result is to trip the high-voltage circuit breaker Q5 and the grounding circuit breaker Q7:

Condition 1: The action switch of the connection circuit breaker failure protection is valid;

Condition 2: There is a fault current at the starting resistor;

Condition 3: The high voltage circuit breaker is in the closing position;

Condition 4: The grounding circuit breaker changes from the open position to the closed position;

Among them, the connecting circuit breaker Q6 is a circuit breaker connecting the active filter in the hybrid AC filter with the tail end of the passive AC filter; the starting resistor R0 is connected in series with the converter of the active filter in the hybrid AC filter Connected resistors; high-voltage circuit breaker Q5 is a circuit breaker that connects the head end of the passive AC filter in the hybrid AC filter to the AC bus; the grounding circuit breaker is Q7, which connects the tail end of the passive filter in the hybrid AC filter to ground circuit breaker.

For condition 1, in this embodiment, the action switches connected to the circuit breaker failure protection are double switches, and the two switches connected to the circuit breaker failure protection have the same binary input value, which is equivalent to setting redundant switches; judging The method of whether the action switch input of the connection circuit breaker failure protection is valid is: two action switches connected to the circuit breaker failure protection exist at the same time (the action switch input of the connection circuit breaker failure protection is obtained from the action switch input contact, The action input contact refers to the action contact output after the active area protection of the hybrid AC filter, such as differential protection, overcurrent protection, unbalance protection, etc. breaker failure protection binary input terminal), and the duration of the two binary inputs at the same time does not exceed the set duration threshold, it is determined that the condition for connecting the circuit breaker failure protection to the active binary input is met; that is, when two binary inputs exist at the same time It is confirmed that the input is valid only when the switch input is valid, so as to ensure that the two inputs are mutually referenced to avoid misidentification of a single switch input that is difficult to be found; connect the action switch input for circuit breaker failure protection, the high-voltage circuit breaker is in the closing position, and is grounded The condition for the circuit breaker to change from the open position to the closed position is essentially to confirm that the passive zone of the hybrid AC filter is in a normal working state, the active zone in the hybrid AC filter is in a fault state, and the protection of the active zone has issued a trip Order. In addition, in this implementation, the duration threshold is set to 12 seconds. When the double switch input of the failure protection action of the connection circuit breaker Q6 exists for a long time for more than 12s, it will report "the protection action switch input has existed for a long time", and the connection circuit breaker failure protection will be blocked, that is, no Then execute the connection circuit breaker failure protection action; under normal circumstances, the binary input connected to the circuit breaker Q6 failure protection action usually has the characteristics of a short existence time, so if the double input exists for a long time, it may indicate that the signal transmission of the binary input is faulty or Other reasons lead to the existence of double inputs. In order to avoid the false triggering of the connection circuit breaker failure protection, when the double input of the connection circuit breaker Q6 failure protection action is found to exist for a long time, the connection circuit breaker failure protection will be blocked and an alarm will be issued to remind the staff. Overhaul in time.

For the second condition, the three-phase current at the starting resistor R0 collected by the T5 current transformer is used as the criterion: any one of the three-phase currents at the starting resistor is greater than the set threshold of the connection circuit breaker failure protection, that is, I _a >I _set , I _b >I _set or I _c >I _set ; where, I _a , I _b and I _c are the three-phase currents at the starting resistor respectively; I _set is the threshold value for the failure protection of the connection circuit breaker.

According to the characteristic that the fault current is small and difficult to judge, this embodiment provides a variety of criteria for detecting whether the fault current exists from various aspects, so as to improve the sensitivity of the detection results; except for the three-phase current corresponding to the starting resistor R0 In addition to the criterion, the criterion corresponding to "zero-sequence current I ₀ overcurrent and negative-sequence current I ₂ overcurrent at the starting resistor" is added, because the disconnection of CT will affect the zero-sequence current I _{0 and the negative sequence current I 2} at the starting resistor. Negative sequence current I ₂ causes this criterion to fail, so in order to save calculation costs as much as possible, this criterion is blocked by CT disconnection and the corresponding control word, and the corresponding control word used to block this criterion is CT disconnection blocking failure The protection logic startup control word can be set by the staff as input or exit status according to the actual needs. When it is enabled, it will block the "zero sequence current I ₀ overcurrent and negative sequence current I at the starting resistor" when the CT is disconnected. ₂ overcurrent", when exiting, the CT disconnection will no longer affect the criterion corresponding to "zero sequence current I ₀ overcurrent and negative sequence current I ₂ overcurrent at the starting resistor"; that is, if When the CT disconnection locking failure protection logic startup control word is put in and it is judged that the CT disconnection occurs in the three-phase current of the starting resistor R0, the zero and negative sequence overcurrent criterion exits (this criterion is no longer one of the criteria in condition two ), it can be judged only by the three-phase current criterion at the starting resistor; otherwise, it can be judged by the negative-sequence overcurrent, zero-sequence overcurrent or phase current overcurrent criterion. input, and it is judged that the three-phase current at the starting resistor has a CT disconnection, then the method of judging whether the condition of fault current at the starting resistor R0 is met is:

If any one of I _a > I _set , I _b > I _set or I _c > I _set is satisfied, it is judged that the condition of fault current at the starting resistor is met, that is, condition two is satisfied;

Among them, I _a , I _b and I _c are the three-phase currents at the starting resistors respectively; I _set is the threshold value set for the connection circuit breaker failure protection.

If the CT disconnection locking failure protection logic start control word is not put into use, or it is judged that the three-phase current at the starting resistor R0 does not have a CT disconnection, then the method for judging whether the fault current exists at the starting resistor is satisfied is as follows:

If any one of I _a >I _set , I _b >I _set and I _c >I _set is satisfied, or any one of 3I ₀ >I _0set and I ₂ >I _2set is satisfied, it is determined that the starting resistance is satisfied The condition of fault current exists, that is, the second condition is met;

Among them, I _a , I _b and I _c are the three-phase currents at the starting resistor R0 respectively; I _set is the set phase current threshold; I ₀ and I ₂ are the zero-sequence current and negative-sequence current at the starting resistor respectively; I _0set and I _2set are respectively setting the zero-sequence current threshold and setting the negative-sequence current threshold.

For the third condition, in this embodiment, the method of judging whether the condition that the high-voltage circuit breaker Q5 is in the closed position is satisfied is as follows:

If min(I _ha , I _hb , I _hc )>I _YL1 is met, it is determined that the condition that the high-voltage circuit breaker Q5 is in the closed position is satisfied;

Among them, min(I _ha , I _hb , I _hc ) is the effective value of the current fundamental waves of phase A, phase B, and phase C at the head end of the passive AC filter collected by the current transformer T4 in the passive area of the hybrid AC filter The minimum value in; I _YL1 is the first current constant value; the value range of I _YL1 is related to the rated current at the passive AC filter; the value range of I _YL1 in this embodiment is 0.5I _e ~0.7I _e , I _e is the rated current of the passive area of the hybrid AC filter.

For condition four, in this embodiment, the condition of grounding circuit breaker Q7 from the opening position to the closing position is as follows: if both the sudden pulse edge criterion and the steady-state value criterion are satisfied, then it is determined that the grounding circuit breaker Q7 is satisfied. The conditions for changing from the opening position to the closing position; satisfying the sudden pulse edge criterion and the steady state value criterion at the same time can ensure that there is no misjudgment as much as possible, and improve the change of the grounding circuit breaker from the opening position to the closing position. reliability of the judgment results.

Among them, the abrupt pulse edge criterion is: i _da (t)-i _da (t-2T)<kI _e and i _db (t)-i _db (t-2T)<kI _e and i _dc (t)-i _dc (t-2T)<kI _e ;

Among them, i _da (t), i _db (t) and i _dc (t) are the current fundamental RMS values of phase A, phase B, and phase C of the high-voltage circuit breaker at the current sampling moment, and i _da (t-2T) , i _db (t-2T) and i _dc (t-2T) are the fundamental effective values of phase A, phase B, and phase C current at the high-voltage circuit breaker at the sampling time two sampling periods before, and k is greater than 0 The coefficient of k in this embodiment ranges from 0.4 to 0.6, and I _e is the rated current at the passive AC filter;

The steady-state value criterion is: min(I _da , I _db , I _dc )>I _YL2 ;

Among them, min(I _da , I _db , I _dc ) is the minimum value of the fundamental effective values of the A-phase, B-phase, and C-phase currents at the head end of the active AC filter, and I _YL2 is the second active current constant value; the value range of I _YL2 is related to the rated current at the passive AC filter; the value range of I _YL1 in this embodiment is 0.5I _e ~ 0.7I _e , and I _e is the rated current of the passive area of the hybrid AC filter current.

Since the judgment on whether the grounding circuit breaker is changed from the opening position to the closing position may be faster, that is, the judgment on the fourth condition may be completed earlier, in order to avoid the logical judgment result of the fourth condition from being different from that of the first and second conditions. In this embodiment, when the grounded circuit breaker is changed from the open position to the closed position, if the condition is satisfied within the set widening time 1. Conditions 2 and 3, it is determined that the above four conditions are met at the same time; the set stretching time is greater than or equal to 1 second (not less than 1 second).

Example of a protection device for failure of a hybrid AC filter connection circuit breaker:

This embodiment presents a technical solution for a protection device for failure of a hybrid AC filter connected to a circuit breaker. The protection device includes a collector and a processor; The corresponding current values at the head end of the source AC filter, the head end of the active filter, and the starting resistor, and the processor is used to execute program instructions to realize the implementation of the protection method for the failure of the hybrid AC filter connection circuit breaker as described above The protection method in the example.

Since the specific protection mode and working principle of the protection device in this embodiment have been described in detail in the above-mentioned embodiment of the protection method for the failure of the hybrid AC filter connected to the circuit breaker, it will not be repeated here.

The present invention has following characteristics:

1) The action switches connected to the circuit breaker failure protection are double switches, and the two switches connected to the circuit breaker failure protection have the same input quantity, which is equivalent to setting up redundant switches to ensure that the two switches are referred to each other , to avoid the misidentification of a single switch input that is difficult to be found; and according to the characteristics that the switch input usually has a short existence time, when the double switch input exists for a long time, the connection circuit breaker failure protection will be blocked in time and an alarm will be issued to avoid the connection circuit breaker failure protection error. When triggered, it also reminds the staff to overhaul in time.

2) In addition to the criterion corresponding to the three-phase current at the starting resistor, the criterion corresponding to "zero-sequence current overcurrent and negative-sequence current overcurrent at the starting resistor" is added, thus by providing a variety of criteria, Whether the fault current exists can be detected from multiple aspects, so as to improve the sensitivity of the detection result.

3) In order to save calculation costs as much as possible, the criterion corresponding to "zero-sequence current _I0 overcurrent and negative-sequence current _I2 overcurrent at the starting resistor" can be blocked by CT disconnection and corresponding control word, and the staff can choose When the CT disconnection causes the criterion to be invalid, the criterion is not involved in the judgment of the failure protection of the connection circuit breaker, so as to save the logical judgment steps related to the criterion.

4) It is determined that the grounding circuit breaker is changed from the opening position to the closing position. The condition is set to satisfy the mutation pulse edge criterion and the steady state value criterion at the same time, which can ensure that there is no misjudgment as much as possible, and improve the grounding circuit breaker. The reliability of the judgment result from the opening position to the closing position.

It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and not to limit the present invention.

Claims (10)

1. The mixed AC filter is formed by connecting the head end of an active filter with the tail end of a passive AC filter, and is characterized in that when the following four conditions are simultaneously met, after the delay time is set, the mixed AC filter is controlled to be connected with the breaker for failure protection, and the protection method is characterized in that:

condition one: the action of connecting the failure protection of the circuit breaker is started effectively;

condition II: fault current exists at the starting resistor;

and (3) a third condition: the high-voltage circuit breaker is positioned at a closing position;

condition four: the grounding circuit breaker is changed from a switching-off position to a switching-on position;

the connecting breaker is a breaker for connecting an active filter in the hybrid alternating current filter with the tail end of the passive alternating current filter; the starting resistor is a resistor connected in series with an inverter of an active filter in the hybrid alternating current filter; the high-voltage circuit breaker is a circuit breaker which connects the head end of a passive alternating current filter in the mixed alternating current filter with an alternating current bus; the grounding circuit breaker is a circuit breaker for grounding the tail end of a passive filter in the hybrid alternating current filter.

2. The method for protecting a hybrid ac filter connection breaker failure according to claim 1, wherein the action opening of the connection breaker failure protection is double opening, and the opening amounts of the action opening of the two connection breaker failure protection are the same;

the mode for judging whether the action of connecting the breaker failure protection is effective is as follows: and if the action opening of the failure protection of the two connecting circuit breakers simultaneously exists and the time length of the two opening simultaneously exists does not exceed the set time length threshold, judging that the condition that the action opening of the failure protection of the connecting circuit breakers is effective is met.

3. The method for protecting a hybrid ac filter circuit breaker from failure as recited in claim 1, wherein if the CT disconnection latch failure protection logic starts the control word input and it is determined that the three-phase current at the starting resistor is CT disconnected, the method for determining whether the condition that the starting resistor has a fault current is satisfied is as follows:

if satisfy I _a ＞I _set 、I _b ＞I _set Or I _c ＞I _set If any one of the above conditions is met, judging that the condition that the fault current exists at the starting resistor is met;

wherein I is _a 、I _b And I _c Three-phase currents at the starting resistor respectively; i _set A threshold is set for connection breaker failure protection.

4. The method for protecting a hybrid ac filter circuit breaker from failure as recited in claim 3 wherein if the CT disconnection latch failure protection logic start control word is not asserted or if the CT disconnection does not occur in the three-phase current at the start resistor, determining whether the condition for the fault current at the start resistor is satisfied is as follows:

if satisfy I _a ＞I _set 、I _b ＞I _set And I _c ＞I _set Any one of or satisfy 3I ₀ ＞I _0set And I ₂ ＞I _2set If any one of the above conditions is met, judging that the condition that the fault current exists at the starting resistor is met;

wherein I is _a 、I _b And I _c Three-phase currents at the starting resistor respectively; i _set Setting a phase current threshold; i ₀ And I ₂ The zero sequence current and the negative sequence current at the starting resistor are respectively; i _0set And I _2set And setting a zero sequence current threshold value and a negative sequence current threshold value respectively.

5. The method for protecting a hybrid ac filter junction circuit breaker from failure of claim 1, wherein the determining whether the condition of the high voltage circuit breaker in the on position is satisfied is:

if the min (I) _ha ,I _hb ,I _hc )＞I _YL1 Judging that the condition that the high-voltage circuit breaker is at the closing position is met;

wherein min (I _ha ,I _hb ,I _hc ) The minimum value of the effective values of the current fundamental waves of the phase A, the phase B and the phase C at the head end of the passive alternating current filter; i _YL1 A first value of the first presence stream; i _YL1 The range of values of (2) is related to the rated current at the passive ac filter.

6. The method for protecting a hybrid ac filter junction circuit breaker from failure according to claim 1, wherein the condition for changing the ground circuit breaker from the open position to the closed position is as follows: if the abrupt pulse edge criterion and the steady state value criterion are met at the same time, judging that the condition that the grounding circuit breaker is changed from the opening position to the closing position is met;

wherein, the abrupt pulse edge criterion is: i i _da (t)|-|i _da (t-2T)|＜kI _e And |i _db (t)|-|i _db (t-2T)|＜kI _e And |i _dc (t)|-|i _dc (t-2T)|＜kI _e ；

Wherein |i _da (t)|、|i _db (t) | and |i _dc (t) | is the effective value of the current fundamental wave of the phase A, the phase B and the phase C at the high-voltage circuit breaker at the current sampling moment, |i _da (t-2T)|、|i _db (T-2T) | and |i _dc (T-2T) I is the effective value of the current fundamental wave of the phase A, the phase B and the phase C at the high-voltage circuit breaker at the sampling time before two sampling periods respectively, k is a coefficient larger than 0, I _e Is the rated current at the passive ac filter;

the steady state value criteria are: min (I) _da ,I _db ,I _dc )＞I _YL2 ；

Wherein min (I _da ,I _db ,I _dc ) Is the minimum value of the fundamental wave effective values of the phase A, the phase B and the phase C currents at the head end of the active alternating current filter, I _YL2 A second value is defined; i _YL2 The range of values of (2) is related to the rated current at the passive ac filter.

7. The method of protecting against a hybrid ac filter junction circuit breaker failure of any of claims 1-6, wherein the hybrid ac filter junction circuit breaker failure protection action is: high voltage circuit breaker and ground circuit breaker are tripped.

8. The method according to claim 6, wherein after the condition that the ground circuit breaker is changed from the opening position to the closing position is satisfied, if the condition one, the condition two and the condition three are simultaneously satisfied within the set widening time, it is determined that the four conditions are simultaneously satisfied.

9. The method for protecting against failure of a hybrid ac filter junction circuit breaker according to claim 8, wherein said set dwell time is 1 second or more.

10. A protection device for a hybrid ac filter connection breaker failure, comprising a collector for obtaining respective current values at the connection breaker, at the high voltage breaker, at the passive ac filter head end, at the active filter head end and at the starting resistor, respectively, and a processor for executing program instructions for implementing a protection method for a hybrid ac filter connection breaker failure according to any one of claims 1-9.

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