JPH06351154A - Protective relay device - Google Patents

Abstract

PURPOSE:To prevent a protective relay device from malfunctioning in operation caused by a rush current of excitation, by locking a self-phase output of differential detection elements with an output of logical sum of the output a second harmonic detection element and that of a leading or lagging second harmonic detection element. CONSTITUTION:The output of a phase (an R-phase, for example) whose inclusion factor of second harmonic becomes low is locked with the output of OR between the output of a second harmonic detection element 7 of the R-phase and the output of another phase (an S-phase, for example), namely, one phase out of the two phases whose second harmonic detection elements 7 that are surely functioning. More exactly, the logical product (the output of an AND circuit 11) is computed between the R-phase output of a differential element 6 and an output of an OR-NOT circuit 14 between the R-phase second harmonic detection element 7 and the S-phase second harmonic detection element 7. Even when the R-phase differential element 6 generates an erroneous output due to a rush current of excitation, the S-phase second harmonic detection element 7 functions surely. In this way, the malfunction can be prevented in a protective relay device for a transformer even when the R-phase second harmonic element 7 fails to function.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective relay device used for transformer protection, which is provided with measures against inrush current.

[0002]

2. Description of the Related Art FIG. 5 shows an example in which the differential relay 1 is applied to a power transformer T. CT1 and CT2 are main current transformers for introducing the input currents I1 and I2 to the differential relay 1, PT1 is an instrument transformer for introducing the input voltage V to the undervoltage relay 2, 3 is a system power source, 4 Is a circuit breaker. FIG. 6 is an example of an internal circuit of the differential relay for transformer protection. In FIG. 6, 5 is an input transformer, 6 is a differential element which outputs when the difference current Id (the vector sum of I1 and I2) exceeds a predetermined value, and it is judged as an internal accident, and 7 is a difference current Id. Ratio of the second harmonic component (2f) to the included fundamental wave (1f) (2f
/ 1f) is equal to or more than a predetermined value, the second harmonic detection element is determined to be an exciting inrush current and is output, 8 is a NOT circuit for inverting the output of the second harmonic detection element, and 9 is a differential element 6. NO
It is an AND circuit that takes a logical product with the T circuit 8.

In FIG. 6, input currents I1 and I2 are introduced into a differential element 6 and a second harmonic detection element 7 through an input transformer 5, respectively. Input current I introduced to the differential element 6
1 and I2 are differential currents Id = | I1 + in the differential element 6.
Derive I2 |. In this case, the difference current Id due to the load current and the passing current at the time of an external accident becomes zero, and at the time of an internal accident, the difference current Id corresponding to the accident current is generated. The difference current I
When d becomes larger than a predetermined value, it is determined that the transformer has an internal fault, and the differential element 6 outputs. On the other hand, the second harmonic detection element 7
With respect to the input currents I1 and I2 introduced into, the second harmonic detection element 7 derives a difference current Id, and further derives a fundamental wave (1f) and a second harmonic component (2f) from the difference current Id. Ratio (2f / 1 of this fundamental wave (1f) and the second harmonic component (2f)
When f) becomes larger than a predetermined value, it is determined to be an exciting inrush current and the second harmonic detection element 7 outputs it.

By closing the circuit breaker 4 in FIG. 5, a voltage is applied to the power transformer T. When a voltage is applied to the transformer, an exciting inrush current based on the magnetization characteristics of the transformer core flows. This magnetizing inrush current apparently flows in from the power supply side like an internal accident of the transformer and becomes the operation amount (differential current Id) of the differential relay 1, which causes a malfunction of the relay (it operates even if it is not an accident). Become. Therefore, it is necessary to distinguish between the exciting inrush current and the current caused by the actual accident. As a method for this, the second inversion for the fundamental wave included in the difference current Id is used because the exciting inrush current contains a large amount of the second harmonic component. When the ratio of the harmonic component is a predetermined value (generally, about 15% is often used) or more, the inrush current is judged and the output of the differential element is locked to prevent the malfunction of the differential relay. It has elements.

However, the content ratio of the second harmonic wave depends on the phase angle of the applied voltage, the magnitude of the residual magnetism of the transformer core, etc., and only one of the three phases has a low content ratio (the above-mentioned predetermined value). It is known that the content is lower than the value). Therefore, even if the differential relay includes the second harmonic detection element as a measure against the inrush current, the second harmonic detection element 7 of the phase does not operate, and the malfunction output of the differential element 6 cannot be locked. As a differential relay, only that phase may malfunction. Therefore, as a conventional transformer protection device, this measure is taken by the configuration shown in FIG. In FIG. 7, 1 is the differential relay of FIG. 6, and 2 is the undervoltage relay shown in FIG. Reference numeral 10 is a return delay timer for delaying the return of the undervoltage relay 2, 11 is an AND circuit that takes a logical product of signals, 12 is an OR circuit that takes a logical sum of signals, and 13 is a NOT circuit that inverts the signals.

The undervoltage relay 2 operates and outputs when the power transformer T is in a non-voltage state, and recovers after the voltage is applied, but the recovery delay timer 10 continues to output for a fixed time t1. Since the exciting inrush current is a transient phenomenon and disappears after a certain time t2 after applying a voltage to the transformer T, the time t1 of the timer 10 is set to a value larger than the decay time t2 of the exciting inrush current. When the output of the timer 10 is present, a two-phase AND output of the output of the differential relay 1 of its own phase (for example, R phase) and the output of the differential relay 1 of one phase (for example, S phase) of the other phases Similarly, the OR of the two-phase AND output of the S phase and the T phase and the two-phase AND output of the T phase and the R phase
The output is used as the operation output as a protective relay device, and the timer 10
When there is no output of, the OR output of the differential relay 1 of each phase is used as the operation output as the protective relay device.

As described above, when a voltage is applied to the power transformer T, an exciting inrush current flows, which may cause the differential relay 1 to malfunction only in one phase. The decay time t2 of the exciting inrush current after the voltage is applied to the transformer T is equal to or more than the two-phase AN of the differential relay 1.
Since the D output becomes the operation output of the device, the malfunction of the protective relay device due to the excitation inrush current does not occur.

[0008]

SUMMARY OF THE INVENTION In the above conventional method,
There are the following issues. In the method shown in FIG. 7 in which a two-phase AND output is output for a certain period of time when the transformer is turned on, the transformer T requires an instrument transformer PT1 and an undervoltage relay 2, and the reset delay timer 10 has time t1 settling. There is a problem that it is difficult to obtain an appropriate value due to the relationship with the decay time t2 of the exciting inrush current. The present invention has been made to solve the above problems, and includes a transformer PT1 for an instrument and an undervoltage relay 2
Another object of the present invention is to provide a protective relay device which does not require the return delay timer 10 and does not malfunction due to an inrush current of excitation.

[0009]

A protective relay device according to a first aspect of the present invention is configured such that a current for each phase of a multi-phase alternating current circuit is introduced across a protected object having a plurality of terminals and each phase is introduced. A differential detection element that outputs when the difference current for each is greater than or equal to a predetermined value, and a second harmonic detection that outputs when the ratio of the second harmonic to the fundamental wave included in the difference current is greater than or equal to the predetermined value. In a protective relay device including an element, the output of the differential detection element of the self phase is obtained by the logical sum output of the output of the second harmonic detection element of the self phase and the output of the second harmonic detection element of the advanced phase or the delayed phase. I tried to prevent it. The protection relay device according to a second aspect of the present invention is the protective relay device according to the first aspect, instead of the logical sum output of the output of the second harmonic detection element of its own phase and the output of the second harmonic detection element of the advanced phase or the delayed phase, Second phase advance
The output of the harmonic detection element and the output of the delayed second harmonic detection element are prevented from the output of the differential detection element of the own phase. Further, the protective relay device according to claim 3 is the same as in claim 1, except that a logical sum output of the output of the second harmonic detection element of its own phase and the output of the second harmonic detection element of the advanced phase or the delayed phase, The output of the differential detection element of each phase is blocked by the logical sum output of the outputs of the second harmonic detection elements of two of the three phases.

[0010]

As described above, when a voltage is applied to the power transformer T, an exciting inrush current flows, and the second harmonic component contained in this exciting inrush current is low in only one of the three phases. The second harmonic detection element of the phase does not operate, and the malfunction output of the differential element of the phase cannot be locked and may malfunction. On the other hand, the other two phases contain a sufficient amount of the second harmonic component that allows the second harmonic detection element to operate, the second harmonic detection element operates reliably, and the differential element of each phase is The output is locked.

In the present invention, the output of the second harmonic detecting element of the phase (for example, the R phase) in which the second harmonic content has a low content rate, and a phase different from that phase, that is, the second harmonic detecting element is surely performed. OR output with the output of one phase (for example, S phase) of the two phases in which the
By locking the differential element output of the phase (R phase) in which the harmonic content has a low content rate, it is possible to prevent malfunction of the transformer protection relay device. In addition, the phase angle of the applied voltage determines which of the three phases has the second harmonic content with a low content rate,
Since it cannot be specified because it depends on the magnitude of the residual magnetism of the transformer core, it is necessary to have the same configuration and operation in all phases. With the above configuration, it is possible to provide a transformer protection relay device that does not require an instrument transformer, an undervoltage relay, and a return delay timer, and that does not malfunction due to an inrush current of excitation.

[0012]

Embodiments will be described below with reference to the drawings. Figure 1
FIG. 1 is a diagram showing an embodiment of a protective relay device according to the present invention, which is shown as transformer protection. In FIG. 1, the differential element 6 and the second
The harmonic detection element 7 is the same as the element described in FIG. 1-
1 is a differential relay that houses the differential element 6 and the second harmonic detection element 7 and outputs respective operation outputs, and 14 is an OR that takes the logical sum of the outputs of the second harmonic detection element 7 from two phases and inverts A -NOT circuit, 11 is an AND circuit that takes the logical product of the output of the differential element 6 and the output of the OR-NOT circuit 14, and 12 is an OR circuit that takes the logical sum of the outputs of the AND circuits 11 of the respective phases.

Next, the operation will be described. In the present invention, when a voltage is applied to the power transformer T, an exciting inrush current flows,
Regarding the second harmonic component contained in this excitation inrush current, only one of the three phases has a low content rate, and the second harmonic detection element 7 of that phase may not operate, but the other two phases. The second harmonic detection element 7 contains a sufficient amount of the second harmonic for operating the second harmonic detection element 7, and the second harmonic detection element 7 is designed to operate reliably.

A phase having a low second-harmonic content (for example, R
Phase) second harmonic detection element 7 output and a phase different from that phase,
That is, the OR output with the output of one phase (for example, the S phase) out of the two phases in which the second harmonic detection element 7 operates reliably, the phase (R phase) in which the second harmonic content has a low content rate. Lock the output of the differential element 6. That is, the second harmonic detection element 7 of the R phase and the second harmonic detection element of the S phase
The logical product (AND circuit 11 output) of the output of the OR-NOT circuit 14 with the harmonic detection element 7 and the output of the R-phase differential element 6 causes the R-phase differential element 6 to malfunction due to the excitation inrush current. Since the S-phase second harmonic detection element 7 operates reliably even if output, malfunctions as a transformer protection relay device are prevented even if the R-phase second harmonic detection element 7 is not operating. be able to.

In the above example, the output of the OR-NOT circuit 14 of the second harmonic detection element 7 of the R phase and the second harmonic detection element 7 of the S phase,
Logical product with R phase differential element 6 output (AND circuit 11 output)
It has been described that the erroneous output of the R-phase differential element 6 is prevented by taking the following equation. However, it is applied which phase of the exciting inrush currents generated in the three phases has a low second content. It cannot be specified because it depends on the phase angle of the applied voltage and the magnitude of the residual magnetism of the transformer core. Therefore, it is necessary to have the same configuration and operation in all phases.

To describe the other phases, OR-NO between the S-phase second harmonic detecting element 7 and the T-phase second harmonic detecting element 7
AND of the output of the T circuit 14 and the output of the S phase differential element 6 (A
By taking the output of the ND circuit 11), erroneous output of the differential element 6 of the S phase can be prevented, and the OR of the second harmonic detection element 7 of the T phase and the second harmonic detection element 7 of the R phase can be performed. -NOT circuit
It is possible to prevent erroneous output of the T-phase differential element 6 by taking the logical product of the 14 output and the T-phase differential element 6 output (AND circuit 11 output). As described above, according to the above-mentioned embodiment, the transformer P for the meter, which is necessary in the prior art, is required.
It is possible to provide a transformer protection relay device that does not require T1, the undervoltage relay 2 and the recovery delay timer 10 and does not malfunction due to the excitation inrush current.

FIG. 2 shows another embodiment of the transformer protection relay device according to the present invention. In FIG. 2, the same symbols as those in FIG. 1 have the same configurations and operations. In the present embodiment, the output of the second harmonic detection element 7 in a phase in which the second harmonic content has a low content rate (for example, the R phase) and a phase different from that phase, that is, the second harmonic detection element is surely performed. One of two phases in which 7 operates (eg T phase)
With the OR output from the output of the differential element 6, the output of the differential element 6 of the phase (R phase) in which the second harmonic component has a low content rate is locked. That is, the logical product of the OR-NOT circuit 14 output of the R-phase second harmonic detection element 7 and the T-phase second harmonic detection element 7 and the R-phase differential element 6 output (AND circuit 11 output ), Even if the R-phase differential element 6 malfunctions due to the excitation inrush current, T
Since the second harmonic detection element 7 of the phase operates reliably, the malfunction as the transformer protection relay device can be prevented even if the second harmonic detection element 7 of the R phase does not operate.

To describe the other phases, OR-NO of the second harmonic detection element 7 of the S phase and the second harmonic detection element 7 of the R phase.
AND of the output of the T circuit 14 and the output of the S phase differential element 5 (A
By taking the output of the ND circuit 11), the erroneous output of the S-phase differential element 6 can be prevented, and the OR between the T-phase second harmonic detection element 7 and the S-phase second harmonic detection element 7 is performed. -NOT circuit
It is possible to prevent erroneous output of the T-phase differential element 6 by taking the logical product of the 14 output and the T-phase differential element 6 output (AND circuit 11 output).

FIG. 3 shows another embodiment of the transformer protection relay device according to the present invention. In FIG. 3, the same symbols as those in FIG. 1 have the same configurations and operations. In the present embodiment, the second harmonic detecting element 7 is different from the output of the second harmonic detecting element 7 of the phase (for example, R phase) in which the second harmonic component has a low content rate, that is, the second harmonic detecting element 7 is surely provided.
The OR output of the respective outputs of the two phases (S phase and T phase) in which is operated locks the output of the differential element 6 of the phase (R phase) in which the second harmonic content has a low content rate. That is, an OR-NOT circuit of the S-phase second harmonic detection element 7 and the T-phase second harmonic detection element 7
The logical product (AND circuit 11 output) of the 14 outputs and the output of the R-phase differential element 6 is taken, so that the S-phase and T-phase Since the second harmonic detection element 7 operates reliably, malfunction of the transformer protection relay device can be prevented.

To describe the other phases, OR-NO between the T-phase second harmonic detection element 7 and the R-phase second harmonic detection element 7
AND of the output of the T circuit 14 and the output of the S phase differential element 6 (A
By taking the output of the ND circuit 11), the erroneous output of the S-phase differential element 6 can be prevented, and the OR between the R-phase second harmonic detection element 7 and the S-phase second harmonic detection element 7 is performed. -NOT circuit
It is possible to prevent erroneous output of the T-phase differential element 6 by taking the logical product of the 14 output and the T-phase differential element 6 output (AND circuit 11 output).

FIG. 4 shows another embodiment of the transformer protection relay device according to the present invention. In FIG. 4, the same symbols as those in FIG. 1 have the same configurations and operations. In the present embodiment, the OR output of each of the two phases (for example, the R phase and the S phase) of the three phases in which the second harmonic detection element 7 operates reliably, the differential element 6 output of each phase is obtained. Lock it. That is, an OR-NOT circuit of the R-phase second harmonic detection element 7 and the S-phase second harmonic detection element 7
By taking the logical product of the 14 outputs and the output of the differential element 6 of each phase (AND circuit 11 output), even if the differential element 6 of each phase malfunctions due to the inrush current of the R phase or the S phase, Since the second harmonic detection element 7 of one of the two phases operates reliably, malfunction of the transformer protection relay device can be prevented.

In the above example, the output of the OR-NOT circuit 14 of the second harmonic detecting element 7 of the R phase and the second harmonic detecting element 7 of the S phase,
Logical product with 6 outputs of each phase differential element (AND circuit 11 output)
Although it has been described that the malfunction of the transformer protection relay device is prevented by taking the above, the second harmonic detection element 7 of the S phase and the T
OR-NOT circuit 14 output with second phase harmonic detection element 7,
Alternatively, the OR-NOT circuit 14 output of the second harmonic detection element 7 of the T phase and the second harmonic detection element 7 of the R phase, and the differential element 6 of each phase
Even if the logical product with the output (AND circuit 11 output) is taken, malfunction as a transformer protection relay device can be prevented. In this embodiment, only the case where the erroneous output of each phase differential element is locked by the second harmonic of the R phase and the S phase is illustrated.

[0023]

As described above, according to the present invention, the transformer protection relay, which does not require the instrument transformer, the undervoltage relay and the return delay timer, which are required in the prior art, and does not malfunction due to the exciting inrush current, is provided. An electric device can be provided.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a transformer protection relay device according to the present invention.

FIG. 2 is a configuration diagram of another embodiment.

FIG. 3 is a configuration diagram of another embodiment.

FIG. 4 is a configuration diagram of another embodiment.

FIG. 5 is an application example of a differential relay to a power transformer.

FIG. 6 shows an example of an internal circuit of a differential relay.

FIG. 7 is a conventional transformer protection relay device.

[Explanation of symbols]

 1,1-1 Differential relay 2 Undervoltage relay 3 System power supply 4 Circuit breaker 5 Input transformer 6 Differential element 7 Second harmonic detection element 8,13 Inversion (NOT) circuit 9,11 AND (AND) circuit 10 Return delay timer 12 Logical sum (OR) circuit 14 Logical product-inversion (OR-NOT) circuit

Claims (3)

[Claims] 1. A differential detection element which outputs current when a current for each phase of a multi-phase AC circuit is introduced across a protected object having a plurality of terminals and a differential current for each phase is a predetermined value or more. In a protective relay device having a second harmonic detection element that outputs when the ratio of the second harmonic component to the fundamental wave included in the difference current exceeds a predetermined value, the second harmonic detection of its own phase is performed. A protective relay device, characterized in that the output of the differential detection element of its own phase is blocked by the logical sum output of the element output and the output of the advanced or delayed second harmonic detection element. 2. A phase-advancing second harmonic detection element output and a phase lag in place of a logical sum output of the self-phase second harmonic detection element output and the phase advance or phase lag second harmonic detection element output. 2. The protective relay device according to claim 1, wherein the output of the differential detection element of its own phase is blocked by the logical sum output with the output of the second harmonic detection element of. 3. A logical OR output of the output of the second harmonic detection element of its own phase and the output of the second harmonic detection element of the advanced phase or the delayed phase, instead of 3
2. The protective relay device according to claim 1, wherein the output of the differential detection element of each phase is blocked by the logical sum output of the outputs of the second harmonic detection elements of the two phases.