JP7159236B2 - Short circuit breaker for DC power supply equipment - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a short-circuit current interrupting device for interrupting a short-circuit current in DC power supply equipment.

2. Description of the Related Art In power plants such as nuclear power plants, DC power supply facilities are installed in order to supply DC power to control equipment that cannot tolerate power outages in the plant and to equipment that needs to operate even when AC power is lost.

A DC power supply facility used in a power plant includes a charger connected to an AC power supply, a storage battery connected to the charger, and a DC bus for supplying power to the DC facility.

Appropriate circuit breakers are selected and installed based on the concept of protection coordination to protect DC power supply facilities against short-circuit faults. to remove accidents.

On the other hand, following the Fukushima accident, nuclear power plants are required to supply DC power for 24 hours (conventionally, 8 hours).

In order to meet this demand, it is necessary to increase the capacity of existing storage batteries, and related power plants are greatly increasing the capacity of storage batteries.

As the storage battery capacity increases, the short-circuit current flowing into the fault point at the time of a short-circuit fault increases.

In addition, in the US NRC Information notice 2017-06 "Influence of short-circuit current in storage batteries and chargers on electrical failures in DC distribution systems", it is indicated that short-circuit current from the charger panel also needs to be considered. Therefore, the assumed short-circuit current value tends to increase further.

In general, DC circuit breakers have a breaking capacity of about 40 kA, so depending on the configuration of the DC power supply equipment, it may not be possible to break short-circuit currents that exceed the breaking capacity, making it difficult to remove faults. I know it will be.

A technique described in Patent Document 1 is available as a technique for interrupting a current in a DC circuit at the time of an accident.

In Patent Document 1, "a semiconductor element section in which a forward self-excited semiconductor element and a forward thyristor are connected in series, an arrester connected in parallel to the forward thyristor, and a capacitor in series with the semiconductor element section are connected in parallel. A direct current interrupting device comprising a connected semiconductor interrupting device, a current suppressing reactor connected in series with the semiconductor interrupting device, and a mechanical contact type disconnector or circuit breaker connected in series with the semiconductor interrupting device.

Further, Patent Document 2 describes a semiconductor switch as follows: "A series-connected auxiliary DC disconnector and high-speed disconnector, a semiconductor switch circuit, and a nonlinear resistor are connected in parallel."

JP 2016-103427 A International publication WO2015/011949

The technique described in Patent Literature 1 is a direct current interrupting device that has a small power transmission loss and enables miniaturization, and does not recognize the problem caused by an increase in short-circuit current that accompanies an increase in storage battery capacity.

For this reason, it is difficult for the technique described in Patent Document 1 to cope with the above-described increase in short-circuit current.

Further, the technique described in Patent Document 1 is to connect an arrester in parallel with a circuit breaker, operate the arrester with an overvoltage generated at the time of a short circuit, and reduce a fault current.

However, since the short-circuit current continues to flow until the arrester operates, it is thought that the short-circuit current increases during this time, increasing the possibility of damage to equipment. Also, when the storage battery is expanded, it is necessary to review the specifications again.

In addition, the technology described in Patent Document 1 uses a capacitor to generate overvoltage, but the DC power supply equipment in the power plant generates a large current of several tens of kA at the time of failure, so the required capacity will be excessive. Conceivable.

The aforementioned Patent Document 2 describes a compact and low-cost semiconductor switch circuit that improves the voltage imbalance of semiconductor switching elements connected in series.

However, like Patent Document 1, Patent Document 2 does not recognize the problem caused by an increase in short-circuit current that accompanies an increase in storage battery capacity.

Therefore, it is difficult for the technique described in Patent Literature 2 to cope with the above-described increase in short-circuit current.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and its object is to provide a DC power supply capable of reliably interrupting the short-circuit current and eliminating the short-circuit accident even if the short-circuit current increases as the storage battery capacity increases. It is to realize a short-circuit current breaking device for equipment.

In order to achieve the above object, the present invention is configured as follows.

In a short-circuit current interrupter for a DC power supply facility, a charger-side breaker arranged between a charger connected to an AC power supply and a DC power supply bus, and a power supply arranged between a storage battery and the DC power supply bus. a side circuit breaker, a bus circuit breaker arranged between a DC power supply load and the DC power supply bus, a detector for detecting the voltage and current of the DC power supply bus, and the voltage and current detected by the detector. a determination circuit that calculates circuit impedance, determines the calculated circuit impedance, and cuts off the charger-side circuit breaker and the power supply-side circuit breaker.

ADVANTAGE OF THE INVENTION According to this invention, even if a short-circuit current increases with an increase in storage battery capacity, it is possible to realize a short-circuit current interrupting device for DC power supply equipment that can reliably interrupt a short-circuit current and eliminate a short-circuit accident.

1 is a schematic configuration diagram of a DC power supply facility to which a short-circuit current breaking device according to Example 1 of the present invention is applied; FIG. 4 is a block diagram of a determination circuit; FIG. 4 is a graph showing an operating characteristic curve of a circuit breaker having mag-only characteristics; It is a schematic block diagram of Example 2 of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Example 1)
<Overall Configuration of Embodiment 1>
FIG. 1 is a schematic configuration diagram of DC power supply equipment to which a short-circuit current interrupting device according to Embodiment 1 of the present invention is applied.

In FIG. 1, AC power supply 101 is an AC power supply in a power plant. A charger 102 connected to an AC power supply 101 incorporates a rectifier therein and converts the AC power supply 101 into a DC power supply.

The DC power supply side converted into the DC power supply by the charger 102 is connected to the DC power supply bus 103 .

During normal operation of the power plant, the DC power supply output from the charger 102 is used to supply power to the DC power load (not shown in FIG. 1) and to charge the storage batteries 104a and 104b connected to the charger 102.

A bus breaker 112 is connected to the DC power supply bus 103 . Power is supplied from the DC power bus 103 to the DC power load via the bus breaker 112 .

When the AC power supply 101 is stopped, the output of the charger 102 is lost, so power is supplied to the DC power supply load from the storage batteries 104a and 104b.

The short-circuit current interrupter determines a short circuit at the nearest end of the power supply from the indicated values of detectors 105, 106, 107, and 108 for monitoring the state of the voltage and current of the DC power supply bus 103, and the power supply side circuit breakers 109, 110 and a determination circuit 200 that gives a break command to the breaker 111 on the charger side.

The power-side circuit breaker 109 is installed between the storage battery 104 a and the DC power bus 103 , and the detector 106 detects the current and voltage of the DC power bus 103 .

Also, the power supply side circuit breaker 110 is installed between the storage battery 104 b and the DC power supply bus 103 , and the detector 107 detects the current and voltage of the DC power supply bus 103 .

Also, the charger side circuit breaker 111 is installed between the charger 102 and the DC power supply bus 103 , and the detector 108 detects the current and voltage of the DC power supply bus 103 .

A detector 105 is connected to the DC power bus 103 and detects the voltage and current of the DC power bus 103 .

The determination circuit 200 calculates the circuit impedance from the voltages detected by the detectors 105, 106, 107, and 108 and the currents detected by the detectors 106, 107, and 108, and determines that a short-circuit accident has occurred when the impedance is below a certain threshold. , send a trip signal to each circuit breaker 109,110,111,112. Each circuit breaker 109, 110, 111, 112 is opened by the trip signal, and the accident is cleared.

The AC power supply 101 side of the DC power supply bus 103 is the circuit breaker primary side, and the circuit breaker 112 side connected to the DC power supply load of the DC power supply bus 103 is the circuit breaker secondary side.

Next, the operation of the short-circuit current interrupting device will be described for each case when a short-circuit failure occurs.

(Case 1)
If a short-circuit fault occurs in the DC power supply bus 103 or the circuit breaker secondary side and its resistance value (circuit impedance) is less than the first threshold value R0, it is difficult for the circuit breaker 112 of the DC power supply bus 103 to interrupt the current. The circuit breakers 109, 110 and 111 on the 101 side are cut off.

The breaking capacity of one circuit breaker 112 is about 40 kA at maximum, and when the resistance value (circuit impedance) is equal to or less than the first threshold R0, the short circuit current exceeds 40 kA. Therefore, it is difficult to interrupt current with one circuit breaker 112 .

(Case 2)
If a short-circuit fault occurs in the bus 103 and its resistance value (circuit impedance) is equal to or greater than the second threshold value R1, the circuit breakers 109, 110, and 111 on the power supply 101 side may not operate. Regardless, the breakers 109, 110 and 111 on the power supply 101 side are forcibly cut off.

Case 2 corresponds to the circuit breakers 109, 110, and 111 having only the mag-only characteristic shown in FIG.

Mag-only characteristics are characteristics that form an operating characteristic curve 301 as shown in FIG. The circuit breaker operates within the operating characteristic curve 301 .

In the case of a circuit breaker having a magnet-only characteristic, as can be understood from FIG.

(Case 3)
If a short-circuit fault occurs in the bus 103 and its resistance value (circuit impedance) is less than the second threshold value R1, or if a short-circuit fault occurs in the circuit breaker secondary side and its resistance value exceeds the first threshold value R0 , 109, 110, 111, and 112, no particular control is performed, and fault elimination is performed according to the operating characteristics of each circuit breaker 109, 110, 111, and 112. FIG.

<Configuration of Determination Circuit 200>
FIG. 2 is a block diagram of the determination circuit 200. As shown in FIG. Note that the determination circuit 200 is configured by a relay circuit or the like.

In FIG. 2, V 1 of the input section 207 is a signal indicating the voltage output from the detector 105 .

V2 of the input section 207 is a signal indicating the voltage output from the detector 106 attached between the storage battery 104a and the circuit breaker 109. FIG.

Also, I2 of the input section 207 is a signal indicating the current output from the detector 106 .

V3 of the input section 207 is a signal indicating the voltage output from the detector 107 attached between the storage battery 104b and the circuit breaker 110. FIG. Also, I3 of the input section 207 is a signal indicating the current output from the detector 107 .

V4 of input section 207 is a signal indicating the voltage output from detector 108 attached to the section between charger 102 and circuit breaker 111 . Also, I4 of the input section 207 is a signal indicating the current output from the detector 108 .

When the circuit impedance satisfies the following expression (1), that is, when the circuit impedance is equal to or less than the first threshold value R0, the circuit breakers 109, 110, and 111 on the circuit breaker primary side are cut off via the OR circuit 201A. 109 trip circuit 203 , circuit breaker 110 trip circuit 204 and circuit breaker 111 trip circuit 205 .
V1÷(I2+I3+I4)≦R0 (1)

When the circuit impedance satisfies the following equations (2), (3) or (4), that is, when the circuit impedance is equal to or greater than the second threshold value R1, the circuit breaker on the primary side of the circuit breaker A trip signal is sent to circuit breaker 109 trip circuit 203, circuit breaker 110 trip circuit 204 and circuit breaker 111 trip circuit 205, which interrupt circuits 109, 110 and 111.
V2÷I2≧R1 (2)
V3÷I3≧R1 (3)
V4÷I4≧R1 (4)

Here, the first threshold R0 is the impedance obtained by dividing the voltage of the DC power supply bus 103 by the breaking current of the bus breaker 112 ((voltage of the DC power supply bus 103)÷(breaking current of the bus breaker 112)). be. An example breaking current of breaker 112 is 40 kA.

The second threshold value R1 is the impedance obtained by dividing the voltage of the DC power supply bus 103 by the operation start current of the bus breaker 112 ((voltage of the DC power supply bus 103)/(operation start current of the bus breaker 112 (mag Only characteristic))).

A delay circuit 202 and a circuit breaker 112 trip circuit 206 for tripping the circuit breaker 112 on the secondary side of the circuit breaker are connected to the OR circuit 201A.

This is a configuration for tripping the circuit breaker 112 on the secondary side of the circuit breaker after tripping the circuit breakers 109, 110, 111 on the primary side of the circuit breaker. Even if one of the circuit breakers 109, 110, 111 is turned on for some reason after tripping the circuit breaker 109, 110, 111 on the primary side of the circuit breaker, the circuit breaker on the secondary side of the circuit breaker By setting 112 to OFF, the device can be reliably protected from a short-circuit accident.

Through the above configuration and operation, when a short circuit occurs on the circuit breaker secondary side of the DC power bus 103, a current exceeding the breaking current of the circuit breaker 112 flows, and when a short circuit occurs on the circuit breaker primary side of the DC power bus 103, individual Even in the case where the breaking current of the circuit breakers 109, 110, 111 is small and the circuit breaker on the primary side of the circuit breaker does not operate, it is possible to reliably remove the short-circuit fault.

If it is assumed that it is difficult to interrupt the short-circuit current with the circuit breaker 112 on the downstream side (secondary side of the circuit breaker) when a short-circuit accident occurs, the circuit breaker on the upstream side (the primary side of the circuit breaker) By disengaging from 109, 110, 111, the accident can be eliminated.

When the breaking capacity of the downstream side circuit breaker 112 is exceeded or when it is difficult to interrupt the fault current by the circuit breaker due to the characteristics of the upstream side circuit breakers 109, 110, 111, the upstream circuit breaker is forced to open. Therefore, short-circuit fault elimination is possible in any configuration.

According to the first embodiment of the present invention, even if the short-circuit current increases as the storage battery capacity increases, it is possible to realize a short-circuit current interrupting device for DC power supply equipment that can reliably interrupt the short-circuit current and eliminate the short-circuit accident. can be done.

In the first embodiment, the determination circuit 200 is configured by a relay circuit or the like. may be applied.

(Example 2)
Next, Example 2 of the present invention will be described.

FIG. 4 is a schematic configuration diagram of the second embodiment. The second embodiment is an example applied to an example of power interchange.

In addition, the same code|symbol is attached|subjected to the component equivalent to Example 1, and the detailed description is abbreviate|omitted. In the example of FIG. 4, the storage battery 104a, the detector 106, and the circuit breaker 109 shown in FIG. 1 are omitted. 2 can be applied.

In the first embodiment described above, as shown in FIG. 1, only a single system is assumed. However, as shown in FIG. Since 402, 403, 404, and 405 have the same characteristics, protection coordination may become difficult.

A DC power supply load 501 is connected to the circuit breaker 112 , a DC power supply load 502 is connected to the busbar connection breaker 402 , and a DC power supply load 503 is connected to the busbar connection breaker 405 .

Even in such a case, the current at the time of the accident is proportional to the circuit impedance (resistance value (=distance)). The farther away the system is, the larger the resistance that operates is set.

By activating the circuit breaker whose resistance value is equal to or less than that value, protection coordination can be achieved even in the power interchange circuit, and the power failure range can be minimized.

Next, the operation of the short-circuit current interrupting device will be described for each case when a short-circuit failure occurs.

As for case 1, case 2, and case 3 described in the first embodiment, the operation is the same in the second embodiment, so the description is omitted.

(Case 4)
When a short-circuit fault occurs at the short-circuit fault point 406 and its resistance value (circuit impedance) is equal to or lower than the third threshold value R2, the determination circuit 200 opens the busbar connection breaker 401 to break the fault, remove the fault, and remove the fault. powers the DC power load.

(Case 5)
When a short-circuit fault occurs at the short-circuit fault point 407 and its resistance value (circuit impedance) is equal to or lower than the fourth threshold value R3, the determination circuit 200 opens the busbar connection breaker 404 to break the fault, remove the fault, and remove the fault. and the DC power supply load of the flexible circuit.

Here, the third threshold value R2 and the fourth threshold value R3 are obtained by the sum of the first threshold value R0 and the resistance value (circuit impedance) calculated from the cable length of the DC power supply bus 103 (the length of the DC power supply bus). resistance value (circuit impedance).

Note that the third threshold and the fourth threshold can be collectively referred to as power supply circuit thresholds.

In the second embodiment, the same operation as in the first embodiment can be performed, and also in the power interchange circuit, protection cooperation can be achieved, and the power failure range can be minimized.

As described above, in Embodiments 1 and 2 of the present invention, the circuit breaker 111 is arranged between the DC power bus 103 and the charger 102 on the upstream side of the DC power bus 103, and the DC power bus 103 and the DC Circuit breakers 109 and 110 are arranged between the storage batteries 104a and 104b on the upstream side of the power supply bus 103, detectors 105, 106, 107, and 108 for detecting the voltage and current of the DC power supply bus 103 are arranged, and a determination circuit 200 calculates the circuit impedance from the voltages and currents detected by the detectors 105, 106, 107 and 108;

Then, the circuit breakers 109, 110, and 111 on the upstream side of the DC power supply bus 103 are configured to cut off according to the calculated circuit impedance.

A plurality of circuit breakers are arranged on the upstream side of the DC power supply bus 103. Assuming that the current flowing through each of the circuit breakers 109, 110, and 111 at the time of a short circuit fault is 40 kA, the circuit breaker on the downstream side of the DC power supply bus 103 is a circuit breaker 112, the current flowing through the circuit breaker 112 is 3×40=120 kA, which exceeds the breaking capacity and cannot be broken.

The present invention is configured to determine the occurrence of a short-circuit accident based on the calculated circuit impedance and to cut off a plurality of circuit breakers 109, 110, and 111 on the upstream side of the DC power supply bus 103 in which the short-circuit current is dispersed. A short-circuit current can be cut off reliably.

101 AC power supply 102 Charger panel 103 DC power supply bus 104a, 104b Storage battery 105, 106, 107, 108 Detector 109, 110, 111, 112, 401, 402, 403, 404, 405... Breaker, 200... Judgment circuit, 201A, 201B... OR circuit, 202... Delay circuit, 203... Breaker 109 trip circuit , 204... Circuit breaker 110 trip circuit, 205... Circuit breaker 111 trip circuit, 206... Circuit breaker 112 trip circuit, 207... Input part, 406, 407... Short-circuit failure point of flexible circuit , 501, 502, 503 . . . DC power supply loads

Claims (5)

a charger-side circuit breaker arranged between the charger connected to the AC power supply and the DC power supply bus;
a power supply side circuit breaker disposed between the storage battery and the DC power supply bus;
a bus breaker arranged between a DC power supply load and the DC power supply bus;
a detector that detects the voltage and current of the DC power supply bus;
a determination circuit that calculates a circuit impedance from the voltage and current detected by the detector, determines the calculated circuit impedance, and cuts off the charger-side circuit breaker and the power supply-side circuit breaker;
A short-circuit current interrupter for a DC power supply facility, comprising: In the short-circuit current interrupting device for DC power supply equipment according to claim 1,
When the circuit impedance is equal to or less than a first threshold, which is a value obtained by dividing the voltage of the DC power supply bus by the breaking current of the bus breaker, the determination circuit switches the charger side circuit breaker and the power supply side circuit breaker to A short-circuit current breaking device for a DC power supply facility, characterized by breaking the current. In the short-circuit current interrupting device for DC power supply equipment according to claim 2,
When the circuit impedance is equal to or greater than a second threshold value obtained by dividing the voltage of the DC power supply bus by the operation start current of the bus breaker, the determination circuit determines whether the circuit breaker on the charger side and the circuit breaker on the power supply side A short-circuit current interrupting device for a DC power supply facility, characterized by interrupting a device. In the short-circuit current interrupting device for DC power supply equipment according to claim 1,
A power supply interchange circuit having a busbar connection circuit breaker connected to the DC power busbar, wherein the circuit impedance of the determination circuit is a value obtained by dividing the voltage of the DC power supply busbar by the breaking current of the busbar circuit breaker. and the impedance calculated from the length of the DC power bus and the power circuit threshold, which is the sum of the impedance calculated from the length of the DC power bus, the short-circuit current interrupting device of the DC power supply facility, characterized in that the busbar connection breaker is interrupted when the sum is equal to or less than the power circuit threshold . In the short-circuit current interrupting device for DC power supply equipment according to claim 1,
A short-circuit current breaking device for a DC power supply facility, characterized by being used in a DC power supply facility of a power plant.

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