JPH0538041A - Detecting device for abnormality of differential relay - Google Patents

Abstract

PURPOSE:To perform a recovering operation in a short time by obtaining an absolute value from phase currents detected by a current detection load, and discriminating whether they are smaller than respective threshold values or not. CONSTITUTION:A first comparator 1 obtains an absolute value ¦I0¦ from a zero- phase current I0 detected by a zero-phase current detection load R0 interposed between a common contact of phase current detection loads RA, RB, RC to be detected by a current detector CT1, and a ground, and compares it with a threshold value epsilon. Second comparators 2A, 2B, 2C obtain absolute values ¦IA¦, ¦IB>>, ¦IC¦ from phase currents IA, IB, IC detected by the loads RA, RB, RC, and compare them with threshold values alphaA, alphaB, alphaC. If the means 1 decides ¦I0¦> epsilon and the means 2A, 2B, 2C decide ¦IA¦ < alphaA, ¦IB¦ < alphaB, and ¦IC¦ < alphaC, a wire disconnection signal of the detector CT1 is output. Thus, a recovering operation can be performed in a short time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects the currents on the primary side and the secondary side of a transformer by a current detection circuit, and based on the ratio or difference of the detected currents on the primary side and the secondary side. The present invention relates to a differential relay abnormality detection device that detects and protects an abnormality of a protection target device.

[0002]

2. Description of the Related Art Differential relays or ratio differential relays (hereinafter referred to as "differential relays"
Means the ratio or difference of the currents i1 and i2 flowing respectively on the primary side and the secondary side of the transformer, and when the ratio or difference exceeds a certain range, the device to be protected (for example, the transformer). ) Is to block the flow of current to.

The differential relay requires a current detection circuit for detecting the currents i1 and i2 flowing through the primary side and the secondary side of the transformer, respectively. FIG. 4 shows a current detection circuit for each phase current flowing through the primary side and the secondary side of the transformer in the case of three-phase alternating current. The currents flowing through the primary side and the secondary side of the transformer T inserted in the power supply line L are detected by the current detection circuits CT1 and CT2, respectively, and the load resistances RA1, RB1, RC1 and RA2, through the auxiliary transformers ACT1 and ACT2. Voltages VA1, VB1, VC1, VA2, VB2 and VC2 are detected across RB2 and RC2.

In the above-mentioned differential relay, a fault other than the equipment to be protected, for example, the current detecting circuits CT1 and CT of the differential relay
Even if disconnection or ground fault occurs in 2, the differential relay operates.
Even in this case, since recovery is performed from the protection target device, the recovery time cannot be shortened. The present invention has been made in view of the above problems, and by independently detecting the disconnection and the ground fault of the current detection circuit of the differential relay, the failure portion can be identified and the recovery time can be shortened. An object of the present invention is to provide an abnormality detecting device for a relay.

[0005]

SUMMARY OF THE INVENTION An abnormality detecting device for a differential relay according to the present invention, which achieves the above object, comprises:
The current detection load that flows the current of each phase detected by the current detection circuit, the zero-phase current detection load interposed between the common node of the current detection load and the ground, and the zero detected by the zero-phase current detection load. Absolute value | Io | is obtained from phase current Io, first comparing means for comparing with threshold value ε, and absolute value | IA from each phase current IA, IB, IC detected by the current detection load.
│, │IB │, │IC │ are found and the thresholds αA,
The second comparing means for comparing with αB, αC and the first comparing means determine that | Io |> ε, and the second comparing means | IA | <αA, | IB | <αB , Or | IC | <
A disconnection detecting means for outputting a disconnection detection signal of the current detection circuit when it is determined to be α C is provided (claim 1).

According to the anomaly detecting apparatus having the above-mentioned structure, when the current detecting circuit is disconnected, one of | IA |, | IB |, and | IC | becomes 0, so that the threshold values αA, αB, α are respectively set.
The disconnection can be detected by comparing with C. The first comparison means determines that | Io |> ε is because when | Io | ≈0 at the time of disconnection, no current originally flows in the transformer. Even in that case, if the abnormal signal output is issued, it is impossible to distinguish between the interruption of the power supply and the disconnection of the current detection circuit.

Further, according to the present invention, a current detection load for flowing a current of each phase detected by the current detection circuit, a zero-phase current detection load interposed between a common node of the current detection load and the ground, and First comparing means for obtaining an absolute value | Io | from the zero-phase current Io detected by the phase current detection load and comparing it with the threshold value ε, and the phase currents IA and IB detected by the current detection load. , Ic and the zero-phase current Io described above | Io
+ IA │, │Io + IB │, │Io + IC │ is determined, and it is determined that the first comparison means is | Io │> ε, and the third comparison means compares the threshold values βA, βB, βC, respectively. And the third comparison means is | Io + IA | <βA, |
When it is determined that Io + IB | <βB or | Io + IC | <βC, a ground fault detection unit that outputs a ground fault detection signal of the current detection circuit is provided. The respective current detection loads and the zero-phase current detection loads have the same impedance (claim 2).

According to the anomaly detecting apparatus having the above construction, in the case of a ground fault, | Io + IA |, | Io + IB |, | Io + IC
Since either of | becomes 0, the threshold values βA, β
The ground fault can be detected by comparing with B and βC. Taking the case where the A-phase is ground-faulted as an example, the current IA flows from the ground-fault point to the ground due to the ground fault, and the sum of the shunts of the currents IB and IC that have passed through the current detection loads B and C.

[0009]

[Equation 1] Flows from the ground fault to the ground through the current detection load A. The coefficient ½ is based on the fact that the current detection load and the zero-phase current detection load have the same impedance, so that the current is divided equally. The sign − means that the current flows in the current detection load A opposite to the normal case.

On the other hand, the zero-phase current detection load is the sum of the remaining shunts of the currents IB and IC that have passed through the current detection loads B and C.

[0011]

[Equation 2] Flows. Therefore, the sum of the current detected by the current detection load A and the current detected by the zero-phase current detection load | Io + IA |

[0012]

[Equation 3] Becomes The reason why | Io |> ε is determined by the first comparing means is to distinguish between the interruption of the power supply and the ground fault of the current detection circuit.

[0013]

Embodiments will be described in detail below with reference to the accompanying drawings showing embodiments. FIG. 1 is a diagram showing the entire circuit configuration of the abnormality detection device, in which the currents iA, iB, iC flowing through the three-phase power supply line L are
It is detected by the current detection circuit CT1 on the primary side of the transformer T and detected by the current detection circuit CT2 on the secondary side. Hereinafter, only the circuit 11-1 which processes the current value detected on the primary side of the transformer T will be described, but the current value detected by the current detection circuit CT2 on the secondary side of the transformer T is the same circuit. 11
First, let's decline that it is processed by -2. Transformer T 1
Subscripts 1 and 2 indicating the secondary side and the secondary side are omitted below.

The phase currents IA, IB, IC and the zero-phase current Io = IA + IB + IC detected by the auxiliary transformer ACT are the voltage VA, VB, VC, Vo of the load resistances RA, RB, RC, Ro. Detected as. The voltage Vo is the absolute value | Vo in the absolute value circuit 4.
| And is compared with the threshold value ε in the first comparator 1. The threshold value ε is a constant set in consideration of an error amount from the equilibrium state of the three-phase AC circuit.

The voltages VA, VB, VC are absolute value circuits 5A, 5B,
Absolute values | VA |, | VB |, | VC |
The thresholds αA, αB, α in the second comparators 2A, 2B, 2C
Compared to C. The thresholds αA, αB and αC are constants set for detecting disconnection. In addition, the voltage VA, VB, VC
Is the vector sum V with the voltage Vo at the adder circuits 6A, 6B and 6C.
A + Vo, VB + Vo, VC + Vo are taken and their absolute values | VA + Vo |, | VB + Vo |, | VC + Vo
| Is taken. The third comparators 3A, 3B and 3C are compared with the threshold values βA, βB and βC. Threshold βA, β
B and βC are constants set for ground fault detection.

The outputs of the second comparators 2A, 2B and 2C are OR
Entering the circuit 7, the output of the OR circuit 7 enters the AND circuit 9 together with the output of the first comparator 1. The output of the AND circuit 9 is taken out as a disconnection signal. Third comparator 3A, 3
The outputs of B and 3C enter the OR circuit 8, and the output of the OR circuit 8 enters the AND circuit 10 together with the output of the first comparator 1. The output of the AND circuit 10 is taken out as a ground fault signal.

FIG. 2 shows a current iA, i flowing through the three-phase power supply line L.
B, iC, currents IA, IB, IC, Io flowing through the primary side of the current detection circuit CT and auxiliary transformer ACT, auxiliary transformer A
Currents flowing through the secondary side of CT kIA, kIB, kIC, kIo,
6 is an enlarged circuit diagram showing voltages VA, VB, VC, Vo of load resistances RA, RB, RC, Ro, respectively. k is an auxiliary transformer ACT
Is a constant determined by the metamorphic ratio of. Voltage VA, VB, VC, Vo
Are proportional to the currents IA, IB, IC and Io, respectively.

When one of the three phases is broken, for example, when the A-phase coil of the current detection circuit CT is broken, as shown by the mark X in FIG. 2, IA = 0. At this time, the load resistance R
The absolute value | VA | of the voltage detected at A also becomes zero. However, since the sum IB + IC of the currents IB and IC of the other phases flows through Io, | V0 | does not become zero. Therefore, a signal appears at the output of the second comparator 2A and a signal also appears at the output of the first comparator 1. Therefore, since the signal is taken out from the output of the AND circuit 9, it can be understood that the current detection circuit CT is disconnected.

FIG. 3 shows the case where one of the three phases has a ground fault. For example, if the A-phase is ground-faulted, from the ground-fault point X to the ground, the current IA and half of the currents IB and IC flowing through the primary-side B-phase coil and the primary-side C-phase coil of the auxiliary transformer ACT, respectively. sum

[0020]

[Equation 4] Flows in through the primary-side A-phase coil. This current is the secondary side A phase coil of the auxiliary transformer ACT.

[0021]

[Equation 5] Detected as. On the other hand, the remaining half of the primary side zero-phase coil of the auxiliary transformer ACT

[0022]

[Equation 6] Flows. This current is the secondary side zero-phase coil of the auxiliary transformer ACT.

[0023]

[Equation 7] Detected as. Therefore, | VA + Vo | obtained by the adder circuit 6A becomes 0, and an output appears in the third comparator 3A. On the other hand, in the primary side zero phase coil of the auxiliary transformer ACT, as described above,

[0024]

[Equation 8] Since | V0 | does not become 0, the first comparator 1
A signal also appears at the output of. Therefore, since a signal is extracted from the output of the AND circuit 10, it can be seen that the current detection circuit CT has a ground fault.

[0025]

As described above, according to the abnormality detecting device for a differential relay of the present invention (claim 1), the absolute value | IA | from the phase currents IA, IB, IC detected by the current detection load. ,
│IB│, │IC │ is calculated, and thresholds αA, αB,
Since it is determined whether or not it is smaller than α C, it can be determined whether or not the disconnection of the current detection circuit is the cause when the differential relay operates. If the current detection circuit is broken, it is possible to save the labor of inspecting the protection target device, and the restoration work can be completed in a short time.

According to the abnormality detecting device for a differential relay of the present invention (claim 2), | Io + IA |, | Io + I is calculated by using the phase currents IA, IB, IC and the zero-phase current Io.
B |, | Io + IC |
Since it is determined whether or not it is smaller than B and βC, it can be determined whether the ground fault of the current detection circuit is the cause when the differential relay is operating. If there is a ground fault in the current detection circuit, it is possible to save the labor of inspecting the protection target device, and the restoration work can be completed in a short time.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall circuit configuration of an abnormality detection device.

FIG. 2 is a partially enlarged view showing current and voltage.

FIG. 3 is a diagram showing a relationship between current and voltage when there is a one-phase ground fault.

FIG. 4 is a circuit diagram showing a current detection circuit of a general differential relay.

[Explanation of symbols]

1 first comparator, 2A, 2B, 2C second comparator, 3A, 3B, 3C third comparator, 4 absolute value circuit, 5A, 5B, 5C absolute value circuit, 6A, 6B, 6C adder circuit, 7, 8 OR circuit, 9, 10 AND circuit, T transformer, CT current detection circuit, RA, RB, RC current detection load, Ro Zero-phase current detection load

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tatsuya Raft             47 Umezu Takaune Town, Ukyo-ku, Kyoto Nissin Electric             Within the corporation

Claims (2)

[Claims] 1. A device to be protected based on a current detection circuit detecting a current on a primary side and a current on a secondary side of a transformer, and based on a ratio or a difference between the detected currents on the primary side and the secondary side. In the differential relay that detects and protects the abnormalities of the current detection load, the current detection load that flows the current of each phase detected by the current detection circuit and the zero-phase current detection load that is interposed between the common node of the current detection load and the ground. And a first comparing means for obtaining an absolute value | Io | from the zero-phase current Io detected by the zero-phase current detection load and comparing the absolute value | Io | with the threshold value ε, and each phase current IA detected by the current detection load. , IB, I
Absolute values │IA │, │IB │, │IC │ are obtained from C, and the second comparison means for comparing with the threshold values αA, αB, αC and the first comparison means are | Io │> ε. Disconnection detection for outputting a disconnection detection signal of the current detection circuit when it is determined that the second comparison means is | IA | <αA, | IB | <αB or | IC | <αC. An abnormality detecting device for a differential relay, comprising: 2. Protected equipment based on the ratio or difference between the detected currents on the primary side and the secondary side, respectively, detected by a current detection circuit. In the differential relay that detects and protects the abnormalities of the current detection load, the current detection load that flows the current of each phase detected by the current detection circuit and the zero-phase current detection load that is interposed between the common node of the current detection load and the ground. And a first comparing means for obtaining an absolute value | Io | from the zero-phase current Io detected by the zero-phase current detection load and comparing the absolute value | Io | with the threshold value ε, and each phase current IA detected by the current detection load. , IB, I
Using C and the zero-phase current Io, | Io + IA |, |
Io + IB |, | Io + IC | and third comparing means for comparing the threshold values βA, βB, βC respectively, and the first comparing means determines that | Io |> ε, and The comparison means of 3 is | Io + IA | <βA, | Io + I
When it is determined that B | <βB or | Io + IC | <βC, a ground fault detection unit that outputs a ground fault detection signal of the current detection circuit is provided, and each of the current detection load and the zero-phase current detection load is An abnormality detecting device for a differential relay, which is characterized by having the same impedance.