JP7347952B2 - protection device - Google Patents

Description

The present invention relates to a protection device, and for example, to a protection device that electrically detects a fault in a power transformer.

In general, power transformers (hereinafter also simply referred to as "transformers") in power systems (e.g., special high voltage systems) are installed on the secondary side (low voltage side) in order to improve safety in the event of a ground fault. The neutral point of the Y connection is grounded. For example, transformers for power systems of 275 kV or higher use the direct grounding method, which grounds the neutral point without using a resistor, and transformers of 66 kV or less use the resistance grounding method, which grounds the neutral point through a resistor. is often adopted.

Further, a protection device is attached to the transformer to electrically detect an accident in the transformer (see, for example, Patent Document 1). As this protection device, a ratio differential relay is known that monitors the presence or absence of abnormality in a transformer based on the current ratio between the primary side and the secondary side of the transformer.

However, if a ground fault occurs in a system where the neutral point of the transformer is connected to the grounded side via a resistor (resistance grounding system), the magnitude of the fault current will exceed the rated current of the transformer. Because of their relatively small size, it is generally difficult to detect such ground faults by ratiometric differential relays. Therefore, for the purpose of detecting ground faults on the resistive grounding system side of transformers, a directional ground relay (DGR), which can detect faults with higher sensitivity than a ratio differential relay, is connected to a resistive grounding system. It is installed on the system side.

Japanese Patent Application Publication No. 2000-78754

By the way, depending on the substation, two or more transformers may be installed and parallel operation (parallel operation) in which the transformers are connected and operated in parallel may be performed.

For example, in a substation where transformers of 66 kV or less are operated in parallel, it is preferable to ground the neutral point of each transformer via a resistor (also referred to as "neutral point grounding resistance").

On the other hand, when a ground fault occurs, there is a possibility that electromagnetic induction disturbance may occur depending on the magnitude of the ground fault current. Therefore, an upper limit value (tolerable value) is determined for each system for the ground fault current that flows when a ground fault occurs.

As mentioned above, if a ground fault occurs when a neutral point grounding resistor is connected to all transformers and they are operated in parallel, a ground fault current will flow through each neutral point grounding resistor. There is a possibility that the total amount of ground fault current will exceed the allowable value. For this reason, in the past, in order to prevent the ground fault current from exceeding the allowable value in the event of a ground fault accident, a neutral point grounding resistance was used only at the neutral point of one transformer among multiple transformers operating in parallel. There were cases where it was necessary to connect and operate the

However, if a ground fault occurs when a transformer to which a neutral point grounding resistor is connected is operating in parallel with a transformer to which a neutral point grounding resistor is not connected, there may be a delay in eliminating the cause of the accident. The inventors of the present invention have found that this may lead to an expansion of the power outage range. Hereinafter, this will be explained in detail using figures.

FIGS. 7A and 7B are diagrams showing an example of the configuration of a substation having two transformers that operate in parallel in the related art.
As shown in FIGS. 7A and 7B, the substation 900 transforms power supplied from a power generation facility (power plant) 99 via a primary bus 98 and supplies it to a secondary bus 97. transformers 90_1 and 90_2, and a circuit breaker 93 and a ground fault direction relay (DGR) 92 provided correspondingly to each of the transformers 90_1 and 90_2.

The transformers 90_1 and 90_2 are three-phase two-winding transformers in which both the primary winding and the secondary winding are Y-connected (star-connected). The transformers 90_1 and 90_2 are configured to be able to operate in parallel. When operating in parallel, a neutral point grounding resistor R is connected to only one transformer to ensure that the ground fault current that flows in the event of a ground fault accident is permissible. I try not to exceed the value. 7A and 7B, as an example, a case is shown in which the transformer 90_1 is grounded via a neutral point grounding resistor R.

The circuit breaker 93 on the transformer 90_1 side is connected between the primary side of the transformer 90_1 and the primary bus 98, and between the secondary side of the transformer 90_1 and the secondary bus 97, respectively. The circuit breaker 93 on the transformer 90_2 side is connected between the primary side of the transformer 90_2 and the primary bus 98, and between the secondary side of the transformer 90_2 and the secondary bus 97, respectively. When the ground fault direction relay 92 detects the ground fault current flowing from the secondary side bus bar 97 side to the secondary side of the transformers 90_1 and 90_2, it controls the corresponding circuit breaker 93 to open.

Here, if a ground fault occurs when the transformer 90_1 to which the neutral point grounding resistance R is connected and the transformer 90_2 to which the neutral point grounding resistance R is not connected are operating in parallel. think about.

For example, as shown in FIG. 7A, if a ground fault occurs on the secondary side of transformer 90_2 to which neutral point grounding resistance R is not connected, the ground fault current will flow from the ground to the secondary side of transformer 90_1. It flows into the ground fault point E on the transformer 90_2 side via the neutral point grounding resistance R on the side and the secondary side bus bar 97. Therefore, the ground fault current is detected by the current detector (current transformer) CT of the ground fault direction relay 92 on the transformer 90_2 side, and the ground fault direction relay 92 opens each circuit breaker 93 on the transformer 90_2 side ( off) controlled. As a result, the transformer 90_2 in which the ground fault occurred is separated from the bus bar 98 and the secondary bus bar 97. At this time, the circuit breaker 93 on the transformer 90_1 side is in the closed (on) state, so power supply from the transformer 90_1 to the secondary bus 97 is continued.

On the other hand, as shown in FIG. 7B, if a ground fault occurs on the secondary side of the transformer 90_1 to which the neutral grounding resistor R is connected, the ground fault current will flow from the ground to the secondary side of the transformer 90_1. Although the current flows to the ground fault point E via the neutral point grounding resistance R, it does not flow to the location where the current detector CT of the ground fault direction relay 92 on the transformer 90_1 side is installed. Therefore, the ground fault direction relay 92 on the transformer 90_1 side cannot detect the ground fault current, and the closed (on) state of the circuit breaker 93 on the transformer 90_1 side is maintained. As a result, the ground fault current continues to flow, which may lead to delays in identifying and eliminating the cause of the accident and an expansion of the power outage range.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to enable reliable detection of ground faults in a substation where a plurality of transformers are operated in parallel.

A protective device according to a typical embodiment of the present invention includes a first ground fault current detection relay that detects a ground fault current flowing through a neutral point grounding resistor connected between a neutral point of a transformer and the ground. , a circuit breaker that switches connection and disconnection between the transformer and the bus, a second ground fault current detection relay that detects the ground fault current flowing in the bus, and a detection result of the first ground fault current detection relay. and a control device that controls opening of the circuit breaker when a predetermined condition based on the detection result of the second ground fault current detection relay is satisfied.

According to the exploration method according to the present invention, it is possible to reliably detect a ground fault in a substation where a plurality of transformers are operated in parallel.

1 is a diagram showing the configuration of a substation equipped with a protection device according to an embodiment of the present invention. It is a figure showing an example of composition of a control device. It is a figure which shows the control state of a circuit breaker based on the detection result of each fault overcurrent relay. FIG. 6 is a diagram showing the control state of the circuit breaker based on the detection results of each fault overcurrent relay when the presence or absence of connection of a neutral point grounding resistor is taken into consideration. FIG. 3 is a diagram for explaining the operation of the protection device according to the present embodiment. FIG. 3 is a diagram for explaining the operation of the protection device according to the present embodiment. It is a figure showing another example of composition of a control device. 1 is a diagram illustrating an example of the configuration of a substation having two transformers that operate in parallel in the related art. 1 is a diagram illustrating an example of the configuration of a substation having two transformers that operate in parallel in the related art.

1. Overview of Embodiments First, an overview of typical embodiments of the invention disclosed in this application will be described. In the following description, as an example, reference numerals on the drawings corresponding to constituent elements of the invention are written in parentheses.

[1] A protective device (10, 10_1, 10_2) according to a typical embodiment of the present invention has a neutral point connected between a neutral point of a transformer (1, 1_1, 1_2) and the ground. A first ground fault current detection relay (4A) that detects the ground fault current flowing through the grounding resistor (R), a breaker (3) that switches connection and disconnection between the transformer and the bus, and a ground fault current that flows to the bus. A second ground fault current detection relay (4B/2) that detects a ground fault current, and a predetermined condition based on the detection result of the first ground fault current detection relay and the detection result of the second ground fault current detection relay is satisfied. In this case, the circuit breaker is characterized by comprising a control device (6, 6A) that controls opening of the circuit breaker.

[2] In the above-mentioned protection device, the control device determines that the second ground-fault current detection relay is not detecting a ground-fault current while the first ground-fault current detection relay is detecting a ground-fault current. In this case, it may be determined that the predetermined condition is satisfied, and the circuit breaker may be controlled to open.

[3] In the above-mentioned protection device, the control device is configured to connect the second grounding resistor to the second grounding resistor in a state where the neutral point grounding resistor is connected to the transformer and the first grounding current detection relay detects a grounding current. If the fault current detection relay does not detect a ground fault current, it may be determined that the predetermined condition is satisfied, and the circuit breaker may be controlled to open.

[4] In the above protection device, the control device (6A) may control the circuit breaker to open when the state in which the predetermined condition is satisfied continues for a predetermined period.

2. Specific Examples of Embodiments Hereinafter, specific examples of embodiments of the present invention will be described with reference to the drawings. In addition, in the following description, the same reference numerals are given to the same component in each embodiment, and repeated description is omitted. Furthermore, it should be noted that the drawings are schematic, and the dimensional relationship of each element, the ratio of each element, etc. may differ from reality. Drawings may also include portions that differ in dimensional relationships and ratios.

FIG. 1 is a diagram showing the configuration of a substation equipped with a protection device according to an embodiment of the present invention.
A substation 100 shown in the figure includes substation equipment capable of parallel operation of a plurality of transformers, and also includes a protection device for detecting an accident occurring in each transformer.

Specifically, the substation 100 includes a plurality of transformers 1_1 to 1_n (n is (an integer greater than or equal to 2) and protection devices 10_1 to 10_n.

In addition, in the following description, an example will be explained in which the substation 100 is equipped with two transformers 1_1 and 1_2 (n=2), and protection devices 10_1 and 10_2 are installed for each transformer 1_1 and 1_2. , the number (n) of transformers is not particularly limited.
Moreover, when there is no particular distinction between the transformer 1_1 and the transformer 1_2, the suffix will be omitted and the transformer 1_2 will be referred to as "transformer 1." The protection device 10_1 and the protection device 10_2 are also written as “protection device 10”.

The transformers 1_1 and 1_2 are power transformers, and are, for example, three-phase two-winding transformers in which the primary winding and the secondary winding are each Y-connected (star-connected). For example, the rated voltage on the primary side of transformers 1_1 and 1_2 is 154 kV, and the rated voltage on the secondary side is 66 kV.

The transformers 1_1 and 1_2 are configured to be able to operate in parallel. When operating transformers 1_1 and 1_2 in parallel, in order to prevent the ground fault current from exceeding the permissible value in the event of a ground fault, a neutral point is connected to the neutral point on the secondary side of one transformer. A point grounding resistor R is connected. In this embodiment, a neutral point grounding resistance R is provided for each transformer 1_1, 1_2, and each neutral point grounding resistance R is connected to the neutral point of the secondary side of the transformer 1_1, 1_2 by, for example, a switch or the like. and ground. Here, as an example, it is assumed that the secondary side of the transformer 1_1 is grounded via a neutral point grounding resistor R.

The protection devices 10_1 and 10_2 are devices for detecting a ground fault occurring in the transformers 1_1 and 1_2. Protective devices 10_1 and 10_2 are provided for each transformer 1_1 and 1_2.
Note that since the protection device 10_1 and the protection device 10_2 have the same configuration, the protection device 10_1 will be specifically explained as a representative.

As shown in FIG. 1, the protection device 10_1 includes a circuit breaker (CB) 3, ground fault current detection relays 4A, 4B, a ground fault direction relay (DGR) 2, and a control device (CNTR) 6. ing.

The circuit breaker 3 is a device that switches connection and disconnection between the transformer 1_1 and the bus bar. As shown in FIG. 1, the circuit breaker 3 is connected between the primary side of the transformer 1_1 and the primary side bus 8, and between the secondary side of the transformer 1_1 and the secondary side bus 7. There is. In normal times, the circuit breaker 3 is in a closed state, the primary side of the transformer 1_1 and the primary side bus 8 are connected, and the secondary side of the transformer 1_1 and the secondary side bus 7 are connected.

The circuit breaker 3 is controlled to open (turned off) by control signals from the control device 6 and the ground fault direction relay 2 . When at least one of the control signal from the control device 6 and the control signal from the ground fault direction relay 2 is a signal instructing "open (off) control", the state becomes open (cut off), and the transformer 1_1 is switched to the primary side. Separate from busbars 7 and 8 respectively.

The ground fault current detection relays 4A and 4B are devices that detect overcurrent flowing through the bus bar. The ground fault current detection relays 4A and 4B are, for example, over current ground relays (OCGR). Hereinafter, the ground fault current detection relays 4A, 4B are also referred to as "ground fault overcurrent relays 4A, 4B."

The earth fault overcurrent relay (OCGR) 4A as the first earth fault current detection relay is a device that detects the earth fault current flowing through the neutral point grounding resistor R connected between the neutral point of the transformer 1_1 and the ground. It is. Specifically, the earth fault overcurrent relay 4A detects the neutral point by the current detector CT1 installed in a path passing through the neutral point grounding resistance R between the neutral point on the secondary side of the transformer 1_1 and the ground. When a ground fault current flowing through the ground resistor R (the direction of the ground fault current does not matter) is detected, the detection result is output to the control device 6.

An earth fault overcurrent relay (OCGR) 4B serving as a second ground fault current detection relay is a device that detects a ground fault current flowing between the secondary bus 7 and the transformer 1_1. Specifically, the ground fault overcurrent relay 4B detects the current from the secondary bus 7 side or When a ground fault current (the direction of the ground fault current does not matter) flowing toward the 7 side is detected, the detection result is output to the control device 6.

The ground fault direction relay (DGR) 2 controls the circuit breaker 3 to open when detecting a ground fault current flowing from the secondary bus 7 side to the transformer 1_1 side. Specifically, the ground fault direction relay 2 uses a current detector (current transformer) CT2 installed on the wire connecting the circuit breaker 3 and the secondary bus 7 to connect the ground fault direction relay 2 from the secondary bus 7 side to the transformer 1_1. When a ground fault current flowing towards the circuit breaker 3 is detected, a control signal for changing each circuit breaker 3 from a connected state to a disconnected state is output to the circuit breaker 3. The circuit breaker 3 enters a cutoff state in response to a control signal instructing opening control from the ground fault direction relay 2, and disconnects the transformer 1_1 from the primary bus 8 and the secondary bus 7.

The control device 6 is a device that controls the circuit breaker 3 based on the detection results of the ground fault overcurrent relay 4A and the detection result of the ground fault overcurrent relay 4B.
Specifically, the control device 6 controls the circuit breaker 3 to open when a predetermined condition based on the detection result of the ground fault overcurrent relay 4A and the detection result of the ground fault overcurrent relay 4B is satisfied.

FIG. 2 is a diagram showing an example of the configuration of the control device 6. As shown in FIG.
As shown in FIG. 2, the control device 6 includes a condition determination section 61 and a signal output section 62.
The condition determining unit 61 is a functional unit that determines whether a predetermined condition is satisfied based on the detection result of the ground fault overcurrent relay 4A and the detection result of the ground fault overcurrent relay 4B. Specifically, the condition determining unit 61 determines that the predetermined condition is satisfied when the ground fault overcurrent relay 4A detects a ground fault current in a state where the ground fault overcurrent relay 4B does not detect a ground fault current, In cases other than the above, it is determined that the predetermined condition is not satisfied.

The signal output section 62 outputs a control signal for controlling the opening of each circuit breaker 3 based on the determination result of the condition determination section 61. Specifically, the signal output unit 62 outputs a control signal instructing opening control (breaking) of each circuit breaker 3 when the condition determining unit 61 determines that the predetermined condition is satisfied.

Here, the control device 6 may be realized, for example, by an electronic device including a program processing device in which a processor such as a CPU processes data according to programs stored in various memories, or by an electronic device including a dedicated logic circuit or the like. It may be realized by a device, and the hardware configuration of the control device 6 is not particularly limited.

FIG. 3A is a diagram showing the control output to the circuit breaker 3 based on the detection results of the ground fault overcurrent relays 4A and 4B. In the figure, "H" represents that a ground fault current is detected, and "L" represents that a ground fault current is not detected.

As shown in FIG. 3A, the control device 6 detects that the ground fault current is detected by the ground fault overcurrent relay 4A (OCGR4A:H) by the condition determination unit 61 and the signal output unit 62, and that the ground fault current is detected by the ground fault overcurrent relay 4B. When a ground fault current is not detected (OCGR4B:L), each circuit breaker 3 is controlled to open (blocked) to disconnect the transformer 1_1 from the primary bus 8 and the secondary bus 7. In cases other than the above, the control device 6 does not perform control output. That is, the circuit breaker 3 is maintained in the closed state.

In addition to the detection results of the ground fault overcurrent relays 4A and 4B, the control device 6 may also include the presence or absence of connection of the neutral point grounding resistor R as a predetermined condition. That is, the condition determination unit 61 determines whether the ground fault overcurrent relay 4A detects a ground fault current when the neutral point grounding resistor R is connected to the transformer 1_1 and the ground fault overcurrent relay 4B is not detecting a ground fault current. If detected, it is determined that the predetermined condition is satisfied.

According to this, as shown in FIG. 3B, the control device 6 detects a ground fault current by the ground fault overcurrent relay 4A in a state where the neutral point grounding resistor R is connected to the secondary side of the transformer 1_1. (OCGR4A:H) and no ground fault current is detected by the ground fault overcurrent relay 4B (OCGR4B:L), the circuit breaker 3 is controlled to open (blocked) and the transformer 1_1 is connected to the bus 8 and the transmission line. Disconnect from wire 7.

Next, the specific operation of the protection device 10 will be explained.
4 and 5 are diagrams for explaining the operation of the protection device 10 according to this embodiment.

As shown in FIG. 4, consider a case where a ground fault occurs on the secondary side of transformer 1_1 to which neutral point grounding resistor R is connected during parallel operation of transformers 1_1 and 1_2.

In this case, as shown in FIG. 4, the ground fault current flows from the ground to the ground fault point E via the neutral point grounding resistance R on the secondary side of the transformer 1_1.
At this time, on the transformer 1_1 (protective device 10_1) side, a ground fault current is detected by the current detector CT1, so the ground fault overcurrent relay 4A outputs a detection result (H) indicating that a ground fault current has been detected. is output to the control device 6. On the other hand, since the ground fault current does not flow into the secondary bus 7, the current detector CT2 on the protection device 10_1 side does not detect the ground fault current. Therefore, the ground fault overcurrent relay 4B outputs to the control device 6 that the ground fault current is not detected (L). At this time, the ground fault direction relay 2 does not continue to output a control signal instructing opening control (blocking) to the circuit breaker 3 because the ground fault current is not detected by the current detector CT2.

The control device 6 on the protection device 10_1 side detects that the ground fault current is detected by the ground fault overcurrent relay 4A (detection result: H), and that the ground fault current is not detected by the ground fault overcurrent relay 4B (detection result: L). Therefore, it is determined that the predetermined condition is satisfied, and the circuit breaker 3 is controlled to open (off) (see FIG. 3A). As a result, each circuit breaker 3 on the protection device 10_1 side is controlled to open (cut off), and the transformer 1_1 in which the ground fault has occurred is separated from the primary bus 8 and the secondary bus 7.

On the other hand, since no ground fault current flows on the transformer 1_2 (protective device 10_2) side, the closed state (connection) of each circuit breaker 3 on the protective device 10_2 side is maintained, and from the transformer 1_2 to the secondary bus 7. Electricity supply will continue.

Therefore, according to the protection devices 10_1 and 10_2, when a ground fault occurs on the transformer side to which the neutral point grounding resistor is connected during parallel operation of multiple transformers as shown in FIG. Also, the transformer in which the ground fault has occurred is reliably separated from the primary bus 8 and the secondary bus 7, and power is continued to be supplied to the secondary bus 7 from the transformer in which the ground fault has not occurred. becomes possible.

Next, as shown in FIG. 5, consider a case where, during parallel operation of transformers 1_1 and 1_2, a ground fault occurs on the secondary side of transformer 1_2 to which neutral point grounding resistor R is not connected.

In this case, as shown in FIG. It flows into the ground fault point E via the circuit breaker 3 on the device 10_2 side.
At this time, on the transformer 1_2 (protective device 10_2) side, the ground fault current is detected by the current detector CT2, so the ground fault overcurrent relay 4B outputs a detection result (H) indicating that the ground fault current has been detected. is output to the control device 6. On the other hand, since the neutral point grounding resistor R is not connected to the transformer 1_2, no ground fault current flows into the ground fault point E via the neutral point of the transformer 1_2. Therefore, the ground fault current is not detected by the current detector CT1 on the protection device 10_2 side, and the ground fault overcurrent relay 4A outputs a detection result (L) indicating that no ground fault current is detected to the control device 6. . The control device 6 on the protection device 10_2 side detects that the ground fault current is not detected by the ground fault overcurrent relay 4A (detection result: L), and the ground fault current is detected by the ground fault overcurrent relay 4B (detection result: H ), it is determined that the predetermined condition is not satisfied, and a control signal instructing the circuit breaker 3 to open (block) is not output (see FIG. 3A).

Moreover, as shown in FIG. 5, the current detector CT2 on the protection device 10_2 side detects the ground fault current flowing from the secondary side bus 7 side toward the secondary side of the transformer 1_2. Thereby, the ground fault direction relay 2 on the protection device 10_2 side outputs a control signal instructing opening control (cutoff) to each circuit breaker 3 on the protection device 10_2 side. As a result, each circuit breaker 3 on the protection device 10_2 side is controlled to open (cut off), and the transformer 1_2 in which the ground fault has occurred can be separated from the primary bus 8 and the secondary bus 7.

On the other hand, on the transformer 1_1 (protective device 10_1) side, since a ground fault current is detected by the current detector CT2, the ground fault overcurrent relay 4B sends a detection result (H) indicating that a ground fault current has been detected. Output to the control device 6. Furthermore, since the ground fault current is detected by the current detector CT1, the ground fault overcurrent relay 4A outputs a detection result (H) indicating that the ground fault current has been detected to the control device 6. The control device 6 on the protection device 10_1 side detects that the ground fault current is detected by the ground fault overcurrent relay 4A (detection result: H), and that the ground fault current is detected by the ground fault overcurrent relay 4B (detection result: H). Therefore, it is determined that the predetermined condition is not satisfied, and a control signal instructing opening control (cutting) of the circuit breaker 3 is not output (see FIG. 3A).

Moreover, as shown in FIG. 5, the ground fault current detected by the current detector CT2 on the protection device 10_1 side is not a current flowing from the secondary side bus 7 side toward the secondary side of the transformer 1_1. Therefore, the earth fault direction relay 2 on the protection device 10_1 side does not output a control signal instructing opening control (blocking).
As a result, each circuit breaker 3 on the protection device 10_1 side is maintained in a closed state (connected), and power supply from the transformer 1_1 to the secondary bus 7 is continued.

Therefore, according to the protection devices 10_1 and 10_2, as shown in FIG. 5, when a ground fault occurs on the transformer side to which the neutral point grounding resistor is not connected during parallel operation of multiple transformers, Also, the transformer in which the ground fault has occurred is reliably separated from the primary bus 8 and the secondary bus 7, and power is continued to be supplied to the secondary bus 7 from the transformer in which the ground fault has not occurred. becomes possible.

As described above, the protection device 10 according to the present embodiment includes the ground fault overcurrent relay 4A that detects the ground fault current flowing through the neutral point grounding resistance R of the transformer 1, and the transformer 1 and the electric wire (secondary side bus bar 7). The circuit breaker 3 that switches connection and disconnection between the circuit breaker 3, the ground fault overcurrent relay 4B that detects the ground fault current flowing in the electric wire (secondary side bus 7), and the detection results of the ground fault overcurrent relay 4A and the ground fault overcurrent relay The control device 6 controls opening of the circuit breaker 3 when a predetermined condition based on the detection result of the circuit breaker 4B is satisfied.

According to the protection device 10, when the transformer 1 to which the neutral point grounding resistance R is connected is operating in parallel with another transformer 1 to which the neutral point grounding resistance R is not connected, the neutral point Even if a ground fault occurs on the transformer 1 side to which the grounding resistor R is connected, as described above, the transformer 1 where the ground fault has occurred is connected to the primary bus 8 and the secondary bus 7. It becomes possible to reliably disconnect from the transformer and continue supplying power to the secondary bus 7 from other transformers in which no ground fault has occurred.

Specifically, the control device 6 of the protection device 10 determines that the predetermined condition is satisfied when the ground fault overcurrent relay 4A detects a ground fault current while the ground fault overcurrent relay 4B does not detect a ground fault current. Then, the circuit breaker 3 is controlled to open (cut off).

According to this, it is possible to reliably shut off only the transformer where a ground fault has occurred, without shutting off transformers where no ground fault has occurred.
For example, let us consider a case where the control device 6 performs opening/closing control of the circuit breaker 3 based only on the detection result of the ground fault overcurrent relay 4A without considering the detection result of the ground fault overcurrent relay 4B. In this case, for example, when a ground fault occurs on the transformer 1_2 side to which the neutral grounding resistor R is not connected, the ground fault current flows through the path shown in FIG. The ground fault overcurrent relay 4A outputs a detection result indicating that the ground fault current has been detected to the control device 6. The control device 6 controls opening (blocking) of the circuit breaker 3 based only on the detection result output from the control device 6 . As a result, the transformer 1_1 in which no ground fault has occurred is also disconnected from the primary bus 8 and the secondary bus 7, and power supply to the secondary bus 7 is stopped.

In this way, when the circuit breaker 3 is controlled to open based only on the detection result of the ground fault overcurrent relay 4A that detects the ground fault current flowing through the neutral grounding resistor R, the transformer 1 where the ground fault has occurred is Not only that, the transformer 1 in which no ground fault has occurred is also cut off, so that the power supply from the substation 100 to the secondary bus 7 is completely stopped.

In contrast, according to the protection device 10 according to the present embodiment, not only the detection result of the ground fault overcurrent relay 4A but also the detection result of the ground fault overcurrent relay 4B that detects the ground fault current flowing to the secondary bus 7 Since the opening control of the circuit breaker 3 is carried out in consideration of the This makes it possible to reliably continue the power supply.

Furthermore, in the protective device 10 according to the present embodiment, in addition to the detection results of the ground fault overcurrent relays 4A and 4B, the presence or absence of the connection of the neutral point grounding resistor R is determined as a predetermined condition for controlling the opening of the circuit breaker 3. May be added to. That is, in a state where the neutral point grounding resistor R is connected to the transformer 1_1 and the ground fault overcurrent relay 4B is not detecting a ground fault current, the control device 6 causes the ground fault overcurrent relay 4A to detect a ground fault current. If this happens, it is determined that the predetermined condition is satisfied, and the circuit breaker 3 is controlled to open.

According to this, even though the neutral point grounding resistor R is not connected, the ground fault overcurrent relay 4A makes a false detection and the predetermined conditions based on the detection results of the ground fault overcurrent relays 4A and 4B are satisfied. Even if this occurs, it is possible to prevent the circuit breaker 3 from being erroneously shut off.

As described above, according to the protection device 10 according to the present embodiment, it is possible to reliably detect a ground fault in a substation where a plurality of transformers are operated in parallel, so that when a ground fault occurs, , it becomes possible to prevent delays in identifying and eliminating the cause of the accident and an expansion of the power outage range.

≪Expansion of the embodiment≫
As above, the invention made by the present inventors has been specifically explained based on the embodiments, but it goes without saying that the present invention is not limited thereto and can be modified in various ways without departing from the gist thereof. stomach.

For example, in the above embodiment, the case where the ground fault current detection relay 4B is a ground fault overcurrent relay is illustrated, but the present invention is not limited to this. For example, a ground fault direction relay (DGR) may be used as the ground fault current detection relay 4B instead of the ground fault overcurrent relay. For example, in FIG. 1, a ground fault direction relay (DGR) is provided as the ground fault current detection relay 4B instead of the ground fault overcurrent relay (OCGR). In this case, the ground fault direction relay serving as the ground fault current detection relay 4B detects the ground fault current flowing from the transformer 1_1 side to the secondary side bus 7 side. When the control device 6 satisfies a predetermined condition based on the detection result of the ground fault overcurrent relay (OCGR) as the ground fault current detection relay 4A and the detection result of the ground fault direction relay (DGR) as the ground fault current detection relay 4B. Then, the circuit breaker 3 is controlled to open.

Further, in the above embodiment, the transformers 1_1 and 1_2 are three-phase two-winding transformers, but they may be three-phase three-winding transformers. For example, the transformers 1_1 and 1_2 may be three-phase, three-winding transformers in which the primary and secondary windings are Y-connected and the tertiary winding is Δ-connected. In this case as well, the neutral point grounding resistor R can be connected to the neutral point on the secondary winding side.

In addition, in the above embodiment, the protection device 10 is configured to detect a ground fault on the secondary side of the transformers 1_1, 1_2, but a ground fault on the primary side of the transformers 1_1, 1_2 The protection device 10 may be configured to detect.

Further, in the embodiment described above, the protection device 10 may control the circuit breaker 3 to open (shut off) when a state in which a predetermined condition is satisfied continues for a predetermined period of time. For example, as in a control device 6A shown in FIG. 6, a timer 63 may be further provided between the condition determination section 61 and the signal output section 62. The timer 63 causes the signal output unit 62 to output a control signal instructing the opening control of each circuit breaker 3 when the condition determination unit 61 determines that a predetermined condition is satisfied continues for a predetermined period. .
According to this, for example, if a situation that satisfies a predetermined condition based on the detection results of the ground fault overcurrent relays 4A and 4B temporarily occurs due to another cause other than a ground fault accident, the circuit breaker 3 may open by mistake. It becomes possible to prevent the transformer 1 from being cut off due to the controlled operation.

1, 1_1, 1_2...Transformer, 2...Ground fault directional relay (DGR), 3...Breaker, 4A...(1st) Ground fault overcurrent relay (OCGR), 4B...(2nd) Ground fault overcurrent relay (OCGR) ), 6, 6A...Control device (CNTR), 7...Secondary side bus, 8...Primary side bus, 9...Power generation equipment (power plant), 10,10_1 to 10_n...Protective device, 61...Condition determination section, 62 ...Signal output unit, 63...Timer, 100...Substation, CT1, CT2...Current detector (current transformer), E...Grounding point, R...Neutral point grounding resistance.

Claims (3)

a first ground fault current detection relay that detects a ground fault current flowing through a neutral point grounding resistor connected between the neutral point of the transformer and the ground;
a circuit breaker that switches connection and disconnection between the transformer and the busbar;
a second ground fault current detection relay that detects a ground fault current flowing in the bus bar;
a control device that controls opening of the circuit breaker when a predetermined condition based on the detection result of the first ground fault current detection relay and the detection result of the second ground fault current detection relay is satisfied ;
The control device satisfies the predetermined condition when the second ground fault current detection relay is not detecting a ground fault current while the first ground fault current detection relay is detecting a ground fault current. and controls the circuit breaker to open.
A protective device characterized by: a first ground fault current detection relay that detects a ground fault current flowing through a neutral point grounding resistor connected between the neutral point of the transformer and the ground;
a circuit breaker that switches connection and disconnection between the transformer and the busbar;
a second ground fault current detection relay that detects a ground fault current flowing in the bus bar;
a control device that controls opening of the circuit breaker when a predetermined condition based on the detection result of the first ground fault current detection relay and the detection result of the second ground fault current detection relay is satisfied;
The control device is configured such that when the neutral point grounding resistor is connected to the transformer and the first ground fault current detection relay detects a ground fault current, the second ground fault current detection relay detects a ground fault current. A protection device characterized in that if the predetermined condition is not detected, it is determined that the predetermined condition is satisfied, and the circuit breaker is controlled to open. The protective device according to claim 1 or 2 ,
The protection device is characterized in that the control device controls opening of the circuit breaker when a state in which the predetermined condition is satisfied continues for a predetermined period of time.

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