JPH08340629A - Confirmation circuit for load side short-circuiting and grounding failure of circuit breaker - Google Patents

Abstract

PURPOSE: To check the soundness of a load side even without closing a circuit again and at the same time reduce wait time until the re-losing of the circuit in the load side short-circuiting failure confirmation circuit of a circuit breaker for opening or closing an electric circuit for connecting an AC power supply and a load provided in a power transmission/distribution system. CONSTITUTION: A current suppression impedance Z, a current detection/judgment device 1, and a three-phase AC power supply S which is lower than a system power supply voltage are connected to the secondary side of a transformer PT for measuring instruments via an auxiliary relay MC. When a circuit breaker CB is tripped due to eddy current, first the auxiliary relay MC is turned on and current is supplied from the three-phase AC power supply S to a load side. The current at that time is detected by the current detection/judgment device 1 to check to see if the load side is sound. If it is not sound, the auxiliary relay MC is turned off and at the same time, for example, the failure display is made to indicate that a short-circuiting failure continues or the circuit breaker CB is introduced and locked. Also, when the Iced side is sound, the auxiliary relay MC is turned off and then the circuit breaker CB is cloud again.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to protection of a power transmission and distribution system, and a load of a circuit breaker for confirming in advance whether or not there is a load side short circuit fault or a ground fault when a circuit breaker is turned on to supply power to a load. The present invention relates to a short circuit on the side of a circuit and a ground fault check circuit on the load side.

[0002]

2. Description of the Related Art In a power transmission and distribution system, when power is stopped due to maintenance or remodeling and power transmission is to be restarted after the work is completed, visual confirmation and insulation resistance confirmation are generally performed as prior confirmation. However, while this method is also easy, it cannot be said to be perfect, and there are cases in which there is a transformer on the load side in particular, and even if the secondary side or the like is three-phase short-circuited grounded, it may not be noticed. In this case, a short-circuit current flows when power transmission starts, and not only an overcurrent trip occurs, but also if the fixing and fixing of the short-circuit ground on the secondary side of the transformer is incomplete, the ground may come off and an arc flashover may occur. It is possible to cause an accident.

In the case where there is a transformer or transformer in which one end of the winding is grounded on the load side, or there is a device grounded via a high impedance, the insulation resistance measurement shows a ground fault on the load side. It may be difficult to determine the presence or absence.

Conventionally, in the power transmission and distribution system shown in FIG.
Even if the circuit breaker CB trips due to overcurrent or ground fault,
Since the cause of the failure may be transient, there is a method of reclosing the circuit in combination with a reclosing relay. That is, when the overcurrent relay is operating, according to the flowchart of FIG. 9, and when the grounding relay is operating, according to the flowchart of FIG. 10, the circuit is closed again after a fixed time after the overcurrent trip and the ground fault trip.

In FIG. 9, when an overcurrent occurs and an overcurrent relay (not shown) operates and the circuit breaker CB trips (steps S ₁ and S ₂ ), the reclosing relay operates in step S ₃ . Then, after a certain period of time, a reclosing command is issued in step S ₄ . Then it is determined whether the load side is healthy is in step S _5, if not healthy is the over current trip (Step S _6), reclosing becomes failure. Also if the load side is healthy, the normal load power supply is performed (step S _7), reclosing is successful.

Further, in FIG. 10, when a ground fault current is generated and a ground fault current relay (not shown) operates to trip the circuit breaker CB (steps S ₁ and S ₂ ), the reclosing relay is performed in step S ₃ . Operates, and after a certain time, step S
_{At 4} a reclose command is issued. In step S ₅ it is determined whether the load side is healthy is if not healthy become ground fault trip (Step S _6), reclosing becomes failure. Also if the load side is healthy, the normal load power supply is performed (step S _7), reclosing is successful.

As described above, conventionally, the circuit is short-circuited again even when the circuit is closed again.
Since there may be a ground fault cutoff, there were many cases where the time until reclosing was set for one minute or more in consideration of the operation duty of the circuit breaker. For example, "0"-(1 minute)-"CO"-
(3 minutes)-"CO" or "0"-(0.35sec)
-"CO"-(3 minutes)-"CO".

[0008]

The conventional reclosing method as described above has the following problems. (1) Until the circuit is reclosed, it is not known whether the short circuit or the ground fault continues.

(2) If the above-mentioned failure continues, short circuit current and ground fault current will flow again due to reclosing, which may increase damage at the failure point.

(3) Even if the cause of the failure is eliminated because the overcurrent is transient, the power failure state continues until the reclosing command is issued from the reclosing relay.

(4) Even if the ground fault is transient and the ground fault is recovered by the first ground fault trip, the power failure state continues until the reclosing command is issued from the reclosing relay. In the case of an overcurrent trip, it is necessary to wait for a certain amount of time until the circuit is closed again due to the operating responsibility of the circuit breaker.However, in the case of a ground fault trip, the normal load current is cut off. You don't have to take a long time.

The present invention has been made in view of the above points, and an object thereof is to confirm the soundness of the load side without trying to reclose the circuit and to shorten the waiting time before reclosing. It is to provide a load side short circuit and load side ground fault failure confirmation circuit of a circuit breaker.

[0013]

The present invention provides (1) a load side short circuit fault confirmation circuit for a circuit breaker for opening and closing an electric path connecting a first AC power source provided in a power transmission and distribution system and a load,
A second AC power supply for supplying electric power for confirming a load-side short-circuit fault; an opening / closing means inserted in an electric path connecting a common connection point of the circuit breaker and the load to the second AC power supply; A determination unit that detects a current flowing between the second AC power supply and the load and determines whether there is a load-side short-circuit fault based on the detected current value; and a closing unit that closes the switching means before closing the circuit breaker. When power is supplied to the load from the AC power supply No. 2, if the determination unit determines that there is no failure, the circuit breaker is closed after opening the switching means, and if the determination unit determines that there is a failure, the circuit breaker And (2) a load side ground fault check of a circuit breaker for opening and closing a circuit connecting the first AC power supply provided in the power transmission and distribution system and the load. In the circuit, supply the power to confirm the load side ground fault. Of the AC power supply, the switching means inserted in the electric path connecting the common connection point of the circuit breaker and the load, and the second AC power supply, and the load-side zero-phase voltage is detected, and based on the detected voltage value. A determination unit that determines whether or not there is a load-side ground fault, and the determination unit determines that there is no failure when power is supplied to the load from the second AC power supply by closing the switching means before closing the circuit breaker. In this case, the circuit breaker is closed after the opening / closing means is opened, and the control unit locks the closing of the breaker when the determination unit determines that there is a failure. The voltage of the AC power supply is set lower than that of the first AC power supply.

[0014]

When the circuit breaker is tripped due to a short circuit on the load side or a ground fault, the opening / closing means is first closed and the second AC power source is connected. As a result, the current or voltage supplied from the second AC power source to the load is detected by the determination unit, and the determination unit determines whether there is a short circuit or a ground fault.

If the short circuit or the ground fault continues, the closing of the circuit breaker is locked, but if there is no such failure and the load is sound, the circuit breaker is immediately closed again. In this way, if the soundness of the load can be confirmed, the circuit can be immediately reclosed, so that the unnecessary waiting time, that is, the power failure time can be shortened.

Since the voltage of the second AC power supply is set low, the power supplied from the second AC power supply to the load side when the short circuit or the ground fault is confirmed is small. Therefore, the short circuit and the damage to the ground fault are small.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, an embodiment of the load side short circuit failure confirmation circuit of the present invention is shown in FIG. In FIG. 1, a three-phase AC power source S is connected to a common connection point between the circuit breaker CB and the load side via a disconnector DS, a current suppression impedance Z, and a current detection / determination device 1.

The current detection / judgment device 1 is composed of, for example, a relay or the like, and has a disconnector D for confirming a load side short circuit failure.
The current flowing from the three-phase AC power source S when S is closed is detected, and the case where the load side is healthy and the case where there is a short circuit failure are discriminated. The current flowing from the three-phase AC power supply S is determined by the magnitude of the voltage of the power supply S, the current suppressing impedance Z and the load side circuit impedance. Even if there is a short circuit failure, the stress due to the short circuit current can be minimized as much as possible. The magnitude of the voltage of the power source S is reduced or the value of the current suppressing impedance Z is selected.

In the case of load power feeding in the device constructed as described above, first the disconnector D is set before the circuit breaker CB is closed.
Close S. At this time, the current detection / determination device 1 detects the current flowing from the three-phase AC power supply S to the load side, and determines whether the load side is sound or there is a short circuit failure. When it is confirmed that the load side is sound, the disconnector DS is opened and then the breaker CB is closed. If the load side is not healthy, the closing of the circuit breaker CB is locked.

As described above, the soundness on the load side can be confirmed before the actual power supply to the load. Moreover, since the 3-phase AC power supply S is set to be lower than the power supply voltage of the system and the current suppressing impedance Z is inserted, the damage is small even if there is a short-circuit point. The power supply capacity of S can be small.

Further, according to the present invention, the instrument transformer PT is provided on the load side of the circuit breaker CB, or when provided, the circuit can be constructed as shown in FIG. That is, unlike the main circuit, the secondary side circuit of the instrument transformer PT has a low voltage, so instead of the disconnector DS,
The current suppression impedance Z, the current detection / determination device 1 and the three-phase AC power supply S are connected to the secondary side of the instrument transformer PT via an auxiliary relay MC. According to the circuit configuration of FIG. 2, it is possible to automatically connect / disconnect the circuit. Therefore, it is possible to combine the automatic circuit and the like to operate according to the flowchart shown in FIG.

In FIG. 3, an overcurrent is generated and
Ray (not shown) tripped and the circuit breaker CB tripped
If (step S₁, S₂) Is step S₃At
The auxiliary relay MC is turned on. As a result, the three-phase AC power supply S
Current is supplied from the load side to the load side.
It is detected by the output / determination device 1. And step S _Four
It is determined whether the load side is healthy in
If not, turn off the auxiliary relay MC and (step
S_Five).
Tep S₆), The closing of the circuit breaker CB is performed (switch
Tep S₇).

If the load side is sound, the auxiliary relay MC is turned off in step S ₈ and then the circuit breaker CB is closed again in step S ₉ . The waiting time after tripping the circuit breaker CB in step S ₂ is provided as necessary.

Next, an embodiment in which the present invention is applied to a circuit for checking the presence / absence of a ground fault on the load side will be described with reference to FIG. FIG.
Then, a three-phase AC power supply S having a voltage equal to or reduced from the actual system voltage can be supplied to each phase on the load side through the switch DS, and the primary side is star-connected to extract the zero-phase voltage on the load side. As a grounding point of the neutral point, the secondary side is connected in series with each phase, both ends of which are open, a so-called broken delta connection transformer Tr is provided, and the secondary side output of the transformer Tr is a zero-phase voltage detection relay Ry. Are typing in.

In the circuit configured as described above, when power is supplied to the load, first the switch D is turned on before the breaker CB is closed.
With S as input, the three-phase voltage of the three-phase AC power supply S is applied to the load side. At that time, the zero-phase voltage appearing on the load side is detected by the zero-phase voltage detection relay Ry, and whether or not there is a ground fault on the load side depending on whether the voltage applied to the three-phase AC power source S is larger or smaller than a preset value. To judge. After the zero-phase voltage detection relay Ry determines that there is no ground fault, the switch DS is turned off, the circuit breaker CB is officially turned on, and power is supplied to the load.

In the present invention, the instrument grounding transformer GPT is provided on the load side of the circuit breaker CB, or, if provided, the circuit can be constructed as shown in FIG. That is, unlike the main circuit, the secondary side and tertiary side circuits of the instrument grounding transformer GPT have a low voltage. Therefore, instead of the switch DS, the instrument grounding transformer GP in FIG.
A three-phase AC power source S is connected to the secondary side of T via an auxiliary relay MC (relay contact), and a zero-phase voltage detection relay Ry is connected to the tertiary side via an auxiliary relay MC (relay contact). According to the circuit configuration of FIG. 5, circuit connection −
Since the disconnection can be performed automatically, it is possible to operate in accordance with the flowchart shown in FIG. 6 by combining an automatic circuit and the like.

In FIG. 6, when a ground fault occurs and a ground fault relay (not shown) operates to trip the circuit breaker CB (steps S ₁ and S ₂ ), the auxiliary relay MC is turned on in step S ₃ . Becomes As a result, a voltage is applied from the three-phase AC power supply S to the load side, and the voltage appearing on the load side at that time is detected by the zero-phase voltage detection relay Ry. Then it is determined whether the load side is healthy is in step S _4, if not healthy turns off the auxiliary relay MC (step S _5), or perform fault indication or the like in the ground fault continues (Step S ₆ ), The closing of the circuit breaker CB is locked (step S ₇ ).

Further when the load side is healthy, after auxiliary relay MC is turned off in step S _8, reclosing of the circuit breaker CB is performed in step S _9. The waiting time after tripping the circuit breaker CB in step S ₂ is provided as necessary.

In the present invention, the transformer Tr of FIG. 4 is removed, and as shown in FIG. 7, a star-connected power source is used as the three-phase AC power source S, and the ground voltage at the neutral point is zero phase. The voltage may be input to the zero-phase voltage detection relay Ry.

In the case of the circuit of FIG. 7 as well, when the load power is supplied, the switch DS is first turned on before the breaker CB is turned on, and the three-phase voltage of the three-phase AC power source S is applied to the load side. The ground voltage at the neutral point at that time is detected as a zero-phase voltage by the zero-phase voltage detection relay Ry, and the presence or absence of a load-side ground fault is determined. After the zero-phase voltage detection relay Ry determines that there is no ground fault, the switch DS is turned off, the circuit breaker CB is officially turned on, and power is supplied to the load.

[0031]

As described above, according to the present invention, the second AC power supply for supplying electric power for confirming a load side short circuit or a ground fault, a common connection point of the circuit breaker and the load, and the first AC power supply. The current flowing between the second AC power supply and the load and the opening / closing means inserted in the electric path connecting the second AC power supply are detected, and the presence or absence of the load side short-circuit fault is determined based on the detected current value. Or a second AC by detecting a load-side zero-phase voltage and determining the presence or absence of a load-side ground fault based on the detected voltage value, and closing the switching means before closing the circuit breaker. When power is supplied from the power supply to the load, if the judgment unit judges that there is no failure, the circuit breaker is closed after opening the switching means, and if the judgment unit judges that there is a failure, the circuit breaker is closed. Since it has a control unit that locks, the following excellent effects can be obtained.

(1) It is possible to confirm the soundness on the load side before actually performing power supply to the load. Also, after the breaker trips due to a short circuit or a ground fault, the soundness can be confirmed without reclosing the breaker.

(2) Since the voltage of the second AC power supply is lower than the power supply voltage of the system, even if there is a short circuit or a ground fault,
You can reduce or eliminate the damage at the time of confirmation,
Also, the power supply capacity can be reduced.

(3) When automatic reclosing is performed, a short circuit,
When the ground fault continues, the reclosing can be stopped in advance, and the damage expansion at the failure point due to the reclosing can be prevented. Further, if the soundness can be confirmed, the reclosing can be continued, so that the waiting time until the reclosing, that is, the power failure time can be shortened.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment in which the present invention is applied to a load side short circuit failure confirmation circuit.

FIG. 2 is a circuit diagram showing another embodiment when the present invention is applied to a load side short circuit failure confirmation circuit.

FIG. 3 is a flowchart of the circuit of FIG. 2 during reclosing operation.

FIG. 4 is a circuit diagram showing an embodiment when the present invention is applied to a load side ground fault confirmation circuit.

FIG. 5 is a circuit diagram showing another embodiment in which the present invention is applied to a load-side ground fault confirmation circuit.

6 is a flowchart of the circuit of FIG. 5 during the reclosing operation.

FIG. 7 is a circuit diagram showing another embodiment when the present invention is applied to a load side ground fault check circuit.

FIG. 8 is a circuit diagram of a system having a circuit breaker.

FIG. 9 is a flowchart of a conventional reclosing operation at the time of tripping a circuit breaker due to overcurrent.

FIG. 10 is a flowchart of a conventional reclosing operation at the time of tripping a circuit breaker due to a ground fault current.

Claims (12)

[Claims] 1. A power supply for confirming a load-side short-circuit fault in a circuit-breaker load-side short-circuit fault confirmation circuit that opens and closes an electric circuit connecting a load and a first AC power supply provided in a power transmission and distribution system. A second AC power supply, a switching means inserted in a circuit connecting the common connection point of the circuit breaker and the load and the second AC power supply, and a current flowing between the second AC power supply and the load. Detect
A load side short circuit failure confirmation circuit for a circuit breaker, comprising: a determination unit that determines the presence or absence of a load side short circuit failure based on the detected current value. 2. The opening / closing means is opened when the judgment section judges that there is no failure when the opening / closing means is closed and power is supplied to the load from the second AC power source before the circuit breaker is turned on. The load side short circuit fault confirmation circuit of the circuit breaker according to claim 1, further comprising a control unit that locks the closing of the circuit breaker when the rear circuit breaker is closed and the determination unit determines that there is a failure. 3. The switching means is inserted in an electric path connecting the secondary side of the transformer for instrument connected to the common connection point of the circuit breaker and the load and the second AC power source. The load side short circuit failure confirmation circuit of the circuit breaker according to claim 1 or 2. 4. The load side short circuit failure confirmation circuit of the circuit breaker according to claim 1, wherein the determination unit is a current relay. 5. The voltage of the second AC power supply is equal to the actual system voltage, and a current control impedance is inserted in a circuit connecting the switching means and the second AC power supply. A load side short circuit failure confirmation circuit of the circuit breaker according to Item 1 or 2 or 3 or 4. 6. The voltage of the second AC power supply is set to be lower than that of the first AC power supply.
Alternatively, the load side short circuit failure confirmation circuit of the circuit breaker according to 2 or 3 or 4. 7. A load-side ground fault check circuit for a circuit breaker, which opens and closes an electric path connecting a first AC power supply and a load provided in a power transmission and distribution system, with a power supply for checking a load-side ground fault. A second AC power supply for supplying power, a switching means inserted in a circuit connecting the common connection point of the circuit breaker and the load and the second AC power supply, and a load-side zero-phase voltage is detected and detected. A load side ground fault failure confirmation circuit for a circuit breaker, comprising: a determination unit that determines the presence or absence of a load side ground fault based on a voltage value. 8. The opening / closing means is opened when the judgment section judges that there is no failure when the opening / closing means is closed and power is supplied to the load from the second AC power source before the circuit breaker is turned on. The load side ground fault failure confirmation circuit of the circuit breaker according to claim 7, further comprising a control unit that locks the closing of the circuit breaker when the rear circuit breaker is closed and the determination unit determines that there is a failure. . 9. The opening / closing means is inserted in an electric path connecting a secondary side of a grounding transformer for an instrument connected to a common connection point of the circuit breaker and a load and the second AC power source, 9. The determination unit detects the voltage induced in the tertiary winding of the instrument grounding transformer, and determines whether there is a load-side ground fault on the basis of the detected voltage value. Circuit to confirm fault on the load side of the circuit breaker described in. 10. The second AC power supply is formed by star-connecting three AC power supplies, and the determination unit is connected between a neutral point of the three AC power supplies and ground. The load side ground fault check circuit of the circuit breaker according to claim 8. 11. The load side ground fault check circuit of a circuit breaker according to claim 8, wherein the judging section is composed of a zero-phase voltage detecting relay. 12. The load side of the circuit breaker according to claim 7, wherein the voltage of the second AC power supply is set lower than that of the first AC power supply. Ground fault check circuit.