JP2000324679A - Low-voltage side electric circuit grounding direction relay - Google Patents

Abstract

PROBLEM TO BE SOLVED: To operate only a circuit breaker at a grounded low-voltage side electric circuit by deciding which of low-voltage side electric circuit from among a plurality of high/low voltage transformers where low-voltage side coil winding is commonly grounded has been grounded. SOLUTION: A relay 1 is provided with a phase comparison circuit 9a for deciding a grounded low-voltage side electric circuit, by comparing the phase of a grounding current that flows through a grounding bus, when either of low-voltage side electric circuit of high/low-voltage transformers where low- voltage side coil winding has been commonly grounded to a Type-B grounding electrode is grounded with the phase of a grounding current that flows to a grounding wire which is connected between the specific grounding point of each low-voltage side coil winding and the grounding bus, and an output circuit 12b for causing a circuit breaker at the low-voltage side electric circuit that has been decided to be grounded to operate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low voltage side electric circuit in which a low voltage side winding of any of a plurality of high / low voltage transformers whose low voltage side winding is commonly grounded to a class B ground electrode is grounded. And to operate a circuit breaker of the low-voltage side electric circuit in which a ground fault has occurred.

[0002]

2. Description of the Related Art
As a private electric facility such as a building or a factory, for example, a three-phase three-wire high / low voltage transformer having a high voltage side of 6.6 kv and a low voltage side of 200 v, a high voltage side of 6.6 kv and a low voltage side of 200 kv are used.
A v-100v single-phase three-wire high-low voltage transformer and the like are installed. In the case of the above-described three-phase three-wire high-low voltage transformer or single-phase three-wire high-low voltage transformer, according to Article 24 of the Technical Standards for Electrical Equipment, the neutral point of the low-voltage winding or the low-voltage winding Class B grounding work at one of the terminals (below a predetermined ground resistance value, usually
It is obliged to perform a common grounding pole work in which only one pole is provided for one customer. FIG. 5 shows that the neutral point N of the low-voltage side winding of the single-phase three-wire high-low-voltage transformer Tr1 and one of the low-voltage side winding terminals TE of the three-phase three-wire high-low-voltage transformer Tr2 are:
FIG. 4 is an electric circuit diagram schematically showing that the power supply device is typically connected to a common type B ground electrode EB provided for only one pole per customer.

The cables connected to the low-voltage side electric circuit of the single-phase three-wire high-low voltage transformer Tr1 and the three-phase three-wire high-low voltage transformer Tr2 have recently become long, and furthermore, capacitors are used as constituent elements. In many cases, an electronic device having a built-in line filter or the like is connected as a load. Therefore, in general,
The apparent ground capacitance (floating capacitance) C of the low-voltage side electric circuit is large.

In the above-mentioned low-voltage side electric circuit, as shown in FIG. 5, the cable of the low-voltage side electric circuit of the three-phase three-wire high / low voltage transformer Tr2 is, for example, D-class grounding (usually a conduit tube, a control panel,
When a ground fault occurs in a conduit in which a control panel or the like is grounded), a ground fault current from the ground fault point is represented by a ground fault resistance R and a D-class ground wire EDL connected to the conduit as indicated by a broken line. , Ground capacitance (floating capacitance) C, single-phase three-wire high-low voltage transformer Tr
1 is a single-phase circuit that is not directly related to the ground fault because it flows in a closed circuit composed of the low-voltage side electric circuit, the class B ground line EBL, and the low-voltage side electric circuit of the three-phase three-wire high-low voltage transformer Tr2. There is a problem that the ground fault circuit breaker ELB on the low voltage side electric circuit of the wire type high / low voltage transformer Tr1 is operated unnecessarily.

[0005] Thus, the single-phase three-wire high-low voltage transformer Tr1
And the neutral point N and the low voltage side winding terminal TE of the low voltage side winding of each transformer are commonly connected to the class B ground pole EB which is a common grounding pole of the three-phase three-wire high / low voltage transformer Tr2. In addition, there is a problem that the ground fault circuit breaker ELB, which is not directly related to the low-voltage side electric circuit of the high-low voltage transformer having the ground fault, may operate.

Therefore, in the present invention, which low-voltage side electric circuit of a plurality of high-and-low-voltage transformers whose low-voltage side windings are commonly grounded is detected, and only the circuit breaker of the grounded low-voltage side electric circuit is operated. It is an object of the present invention to provide a low-voltage side electric circuit ground fault direction relay that can be used.

[0007]

The above object can be attained by the low-voltage side electric circuit ground fault directional relay described in the claims. According to the low voltage side electric circuit ground fault direction relay according to claim 1, when any one of the low voltage side electric circuits of the plurality of high voltage low voltage transformers whose low voltage side winding is grounded to the common grounding pole is grounded, the common grounding is performed. By comparing the phase of the ground fault current flowing through the ground bus connected to the pole with the phase of the ground fault current flowing through each ground wire, it is possible to detect which of the high and low voltage transformers has the low voltage side electric circuit grounded. be able to. According to the low voltage side electric circuit ground fault direction relay of claim 2, only the circuit breaker of the grounded low voltage side electric circuit can be operated, and unnecessary operation of circuit breakers other than the grounded low voltage side electric circuit is prevented. Can be avoided.

[0008]

Next, an embodiment of the present invention will be described. FIG. 1 shows the neutral point N of the low-voltage side winding of the single-phase three-wire high-low-voltage transformer Tr1 and the three-phase three-wire high-low-voltage transformer Tr.
One of the low-voltage side winding terminals TE is a predetermined ground point, and the predetermined ground point is connected to the class B ground electrode (common ground electrode) EB via the ground lines EBL1 and EBL2 and the ground bus EBL0. FIG. 4 is an electric circuit diagram showing that As shown in FIG. 1, a current detector ZCT0 for detecting a ground fault current flowing through the ground bus EBL0, a current detector ZCT1 for detecting a ground fault current flowing through the ground line EBL1, and a ground flowing through the ground line EBL2. A current detector ZCT2 for detecting a short-circuit current is provided. In addition, the current detector ZCT
0, the output terminals of the current detector ZCT1 and the current detector ZCT2 are connected to the single-phase three-wire high-low voltage transformer Tr1 or the low-voltage side electric circuit of the three-phase three-wire high-low voltage transformer Tr2. The low voltage side electric circuit ground fault direction relay 1 which operates the circuit breaker of the low voltage side electric circuit.

FIG. 2 is a block diagram showing the configuration of the low-voltage side electric circuit ground fault directional relay 1. As shown in FIG. 2, the current detector ZCT0 is connected between terminals z1 and z2, the current detector ZCT1 is connected between terminals z3 and z4, and the current detector ZCT2 is connected between terminals z5 and z6. .

An over-input protection circuit 2a connected to terminals z1 and z2, and an over-input protection circuit 2 connected to terminals z3 and z4
b and over-input protection circuit 2 connected to terminals z5 and z6
c is a circuit for preventing the input of an excessive voltage and for electrically protecting the internal circuit. The zero-phase current setting circuit 3a connected to the over-input protection circuit 2b and the zero-phase current setting circuit 3b connected to the over-input protection circuit 2c are used to detect the short-circuit currents detected by the current detectors ZCT1 and ZCT2. This circuit adjusts the input range. Zero-phase current setting circuit 3
a, the filter / amplifier circuit 4b connected to the over-input protection circuit 2a, and the filter / amplifier circuit 4c connected to the zero-phase current setting circuit 3b,
This circuit removes harmonics and high frequency components and amplifies the fundamental component of the ground fault current.

The full-wave rectifier circuit 5a connected to the filter / amplifier circuit 4b and the full-wave rectifier circuit 5b connected to the filter / amplifier circuit 4c convert the AC waveform output from the filter / amplifier circuits 4b and 4c into a DC waveform. Is a circuit that converts the
Waveform shaping circuit 6 connected to filter / amplifier circuit 4a
a, the waveform shaping circuit 6b connected to the filter / amplifier circuit 4b, and the waveform shaping circuit 6c connected to the filter / amplifier circuit 4c output 0 of each sine wave signal output from the filter / amplifier circuits 4a, 4b, 4c. This is a circuit that outputs a pulse signal when rising from volts (see FIG. 3 described later).

Smoothing circuit 7 connected to full-wave rectifier circuit 5a
a, The smoothing circuit 7b connected to the full-wave rectifier circuit 5b is a circuit that removes ripples of the DC waveform output from the full-wave rectifier circuits 5a and 5b. The level detection circuit 8a connected to the smoothing circuit 7a and the level detection circuit 8b connected to the smoothing circuit 7b determine the magnitude of each signal output from the smoothing circuits 7a and 7b, that is, the current detectors ZCT1 and ZCT2.
Is a circuit that outputs a level detection signal when the ground fault current detected in step (1) exceeds a preset reference value.

FIG. 3 shows the current detector ZCT based on the phase of the ground fault current detected by the current detector ZCT0.
9 is a timing chart of the phase comparison circuits 9a and 9b for comparing whether the phases of the ground fault currents detected in 1 and 2 are delayed or advanced. The phase comparison circuits 9a and 9b
As shown in FIG. 4, the phase of the ground fault current (waveform indicated by a two-dot chain line) detected by the current detectors ZCT1 and ZCT2 is, for example, a filter / amplifier circuit 4b,
At the time of output of 4c, the waveform is inverted to a waveform indicated by a solid line shifted 180 degrees in advance, and input to the waveform shaping circuits 6b and 6c.

The phase determination signal EV of the phase comparison circuits 9a and 9b shown in FIG. 3 is a signal inside each of the phase comparison circuits 9a and 9b, and is turned on at the rising timing of the output pulse signal of the waveform shaping circuit 6a. Waveform shaping circuit 6b
Alternatively, it is set to be turned off at the rising timing of the output pulse signal of the waveform shaping circuit 6c. And
If the phase of the ground fault current detected by the current detectors ZCT1 and ZCT2 is behind the phase of the ground fault current detected by the current detector ZCT0, the on-time of the phase determination signal EV is When the phase of the ground fault current detected by the current detectors ZCT1 and ZCT2 is shorter than the half cycle time, the ON time of the phase determination signal EV is longer than the half cycle time of the ground fault current.

As described above, the phase comparison circuits 9a and 9b
Compares a phase of the ground fault current detected by the current detector ZCT0 with a current detector ZCT by comparing the ON time of the phase determination signal EV with the time of a half cycle of the ground fault current.
1, it is determined whether the phase of the ground fault current detected by ZCT2 is delayed or advanced.

Here, the phase comparators 9a and 9b determine the phase of the ground fault current detected by the current detector ZCT0.
Based on the result of comparing whether the phase of the ground fault current detected by the current detectors ZCT1 and ZCT2 is delayed or advanced, it is possible to determine which high-low voltage transformer has the low-voltage side electric circuit in the ground fault. Will be described with reference to FIG.
The directions of the arrows of the ground fault currents I1, I2, I3 and I4 shown in FIG. 1 indicate the current directions in the positive cycle of the ground fault currents. Further, the current detectors ZCT0, ZCT1,
The arrow attached to ZCT2 indicates the direction (direction polarity) based on the winding direction of the coil of each current detector when each current detector is installed.

First, the operation of the phase comparison circuit 9a for determining a low-voltage side electric circuit on which a ground fault has occurred will be described. When the low-voltage side electric circuit of the single-phase three-wire type high-low voltage transformer Tr1 is grounded to a class D grounded conduit, for example, the ground fault current is:
Ground fault resistance R1, D class ground line EDL1, D class ground electrode ED,
Underground, Class B ground pole EB, ground bus EBL0, ground wire EB
L1, a current I1 flowing through a closed circuit composed of a low-voltage side electric circuit of a single-phase three-wire high-low-voltage transformer Tr1, and ground-fault resistances R1, D
Seed ground line EDL1, stray capacitance C2 of three-phase three-wire high-low voltage transformer Tr2, low-voltage side electric circuit of three-phase three-wire high-low voltage transformer Tr2, ground line EBL2, ground line EBL1, single-phase three-wire high-low voltage The current is shunted to a current I2 flowing through a closed circuit formed by the low-voltage side electric circuit of the transformer Tr1.

Since the ground fault current I1 flows through the ground bus EBL0, it is detected by the current detector ZCT0. The ground fault currents I1 and I2 flow through the ground line EBL1, and are detected by the current detector ZCT1. In this case, since the ground fault current I2 flows through the stray capacitance C2 of the three-phase three-wire high / low voltage transformer Tr2, the phase is advanced by approximately 90 ° from the ground fault current I1. Therefore, when the phase of the ground fault current I1 detected by the current detector ZCT0 is used as a reference, the ground fault current detected by the current detector ZCT1 has an advanced phase. As described above, the current detector ZCT0 is used as a reference with respect to the phase of the ground fault current I1 detected by the current detector ZCT0.
When the ground fault current detected by step 1 becomes the advanced phase, the phase comparison circuit 9a determines that the low-voltage side electric circuit of the single-phase three-wire high-low voltage transformer Tr1 has a ground fault, and determines the single-phase three-wire high-low voltage. It outputs a ground fault determination signal indicating that the low voltage side electric circuit of the transformer Tr1 has a ground fault.

Next, when the low-voltage side electric circuit of the three-phase three-wire type high / low voltage transformer Tr2 is grounded to a class D grounded conduit,
The ground fault current includes a ground fault resistor R2, a class D ground line EDL2, a stray capacitance C1 of the single-phase three-wire high-low voltage transformer Tr1, a low-voltage side circuit of the single-phase three-wire high-low voltage transformer Tr1, a ground line EBL1, A ground line EBL2, a current I3 flowing through a closed circuit formed by a low-voltage side electric circuit of a three-phase three-wire high-low voltage transformer Tr2, a ground fault resistance R2, a D-class ground line EDL2, a D-class ground pole ED, B
Seed ground pole EB, ground bus EBL0, ground lines EBL2, 3
And a current I4 flowing through a closed circuit formed by the low-voltage side electric circuit of the phase three-wire high / low voltage transformer Tr2.

Since the ground fault current I4 flows through the ground bus EBL0, it is detected by the current detector ZCT0. Further, since the ground fault current I3 flows through the ground line EBL1,
It is detected by the current detector ZCT1. In this case, the ground fault current I3 flows through the stray capacitance C1 of the single-phase three-wire high-low voltage transformer Tr1, so that the phase is substantially 90 ° more than the ground fault current I4.
The direction of the ground fault current I3 depends on the current detector ZC
Since it is opposite to the directional polarity (the direction of the arrow) of T1,
The phase of the ground fault current I3 detected by the current detector ZCT1 is delayed by about 90 ° from the phase of the ground fault current I4. Thus, the ground fault current I detected by the current detector ZCT1 is
If the phase of the ground fault current 3 is approximately 90 ° behind the phase of the ground fault current I4, the phase comparison circuit 9a outputs a three-phase three-wire high-low voltage transformer Tr.
No. 2 low-voltage side electric circuit is determined to have a ground fault, and the ground fault determination signal is not output.

Next, the operation of the phase comparison circuit 9b for determining the low-voltage side electric circuit having a ground fault will be described. If the low-voltage side electric circuit of the three-phase three-wire high-low voltage transformer Tr2 is grounded to a class D grounded conduit, the ground fault current will be a ground fault resistance R2, a class D ground wire EDL2, a single-phase three-wire system. The stray capacitance C1 of the low-voltage side electric circuit of the high-low voltage transformer Tr1, the low-voltage side electric circuit of the single-phase three-wire high-low voltage transformer Tr1, the ground line EBL1, and the ground line E
BL2, a current I3 flowing through a closed circuit formed by the low-voltage side electric circuit of the three-phase three-wire high-low voltage transformer Tr2, a ground fault resistance R2,
A closed circuit composed of a D-class ground line EDL2, a D-class ground electrode ED, underground, a B-class ground electrode EB, a ground bus EBL0, a ground line EBL2, and a low-voltage side electric circuit of a three-phase three-wire high-low voltage transformer Tr2. The current is divided into the flowing current I4. Therefore, the ground bus EB
Since the ground fault current I4 flows through L0 and the ground fault currents I4 and I3 flow through the ground line EBL2, the ground fault current I4 is detected by the current detector ZCT0, and the ground fault currents I3 and I4 are detected by the current detector ZCT2. Is detected. In this case, since the ground fault current I3 flows through the stray capacitance C1 of the low-voltage side electric circuit of the single-phase three-wire high-low voltage transformer Tr1, the phase is advanced by approximately 90 ° from the ground fault current I4. Therefore, when the phase of the ground fault current I4 detected by the current detector ZCT0 is used as a reference,
The ground fault current detected by the current detector ZCT2 has an advanced phase. As described above, the current detector ZC0 is used as a reference with respect to the phase of the ground fault current I4 detected by the current detector ZCT0.
When the ground fault current detected by T2 is in the advanced phase,
The phase comparison circuit 9b determines that the low-voltage side electric circuit of the three-phase three-wire high-low voltage transformer Tr2 has a ground fault, and indicates that the low-voltage side electric circuit of the three-phase three-wire high-low voltage transformer Tr2 has a ground fault. Outputs a short-circuit determination signal.

Next, when the low-voltage side electric circuit of the single-phase three-wire high / low voltage transformer Tr1 is grounded to a conduit grounded to class D,
The ground fault current is represented by a ground fault resistance R1, a class D ground line EDL1, a class D ground electrode ED, underground, a class B ground electrode EB, and a ground bus EBL.
0, a ground line EBL1, a current I1 flowing in a closed circuit formed by a low-voltage side electric circuit of a single-phase three-wire high-low voltage transformer Tr1, a ground fault resistor R1, a D-class ground wire EDL1, and a three-phase three-wire high-low voltage. Floating capacitance C2 of transformer Tr2, three-phase three-wire high-low voltage transformer T
r2, the low voltage side electric circuit, the ground line EBL2, the ground line EBL1,
It shunts to a current I2 flowing through a closed circuit formed by the low-voltage side electric circuit of the single-phase three-wire high / low voltage transformer Tr1.

The ground fault current I1 flows through the ground bus EBL0 and is detected by the current detector ZCT0. Also,
The ground fault current I2 flows through the ground line EBL2 and is detected by the current detector ZCT2. In this case, the ground fault current I
2 flows through the stray capacitance C2 of the three-phase three-wire high / low voltage transformer Tr2, so that the phase is advanced by approximately 90 ° from the ground fault current I1, but the direction of the ground fault current I2 is the same as that of the current detector ZCT2. Since the polarity is opposite to the direction polarity (the direction of the arrow), the phase of the ground fault current I1 detected by the current detector ZCT2 is delayed by about 90 ° from the phase of the ground fault current I4. in this way,
When the phase of the ground fault current I1 detected by the current detector ZCT2 is substantially 90 ° behind the phase of the ground fault current I4, the phase comparison circuit 9b operates the single-phase three-wire high-low voltage transformer Tr.
It is determined that the first low-voltage path has a ground fault, and the above-described ground fault determination signal is not output.

Next, the configuration of a circuit for operating the output relays X1 and X2 will be described. The AND circuit 10a connected to the level detection circuit 8a and the phase comparison circuit 9a outputs the above-mentioned ground fault determination signal from the phase comparison circuit 9a and outputs the level detection signal from the level detection circuit 8a. An AND signal is output. The AND circuit 10b connected to the level detection circuit 8b and the phase comparison circuit 9b outputs the above-mentioned ground fault determination signal from the phase comparison circuit 9b and outputs the level detection signal from the level detection circuit 8b. Then, an AND signal is output.

The time setting circuit 11a connected to the AND circuit 10a and the time setting circuit 11b connected to the AND circuit 10b are provided by the AND circuits 10a and 10b.
When the D signal is continuously output for a predetermined time set in advance, a relay operation signal is output to the output circuits 12a and 12b. The output circuits 12a and 12b are connected to the time setting circuit 11
When a relay operation signal is output from a and 11b, an excitation voltage is output to the coils of the output relays X1 and X2, and the output relays X1 and X2 are operated. As apparent from the above description, when the output relay X1 is operated, the single-phase three-phase
This is the case where the low voltage side electric circuit of the wire type high / low voltage transformer Tr1 is grounded and a ground fault current of a predetermined level or more flows. When the output relay X2 is activated, the low-voltage side electric circuit of the three-phase three-wire high / low voltage transformer Tr2 is grounded, and a ground fault current of a predetermined level or more flows.

The A contact of the output relay X1 is connected to a tripping coil of a circuit breaker (not shown) connected to the low-voltage side electric circuit of the single-phase three-wire high / low voltage transformer Tr1. When the contacts are closed, the trip coil is excited and the circuit breaker is activated. The B contact of the output relay X1 is connected to an alarm (not shown) including, for example, a buzzer and a lamp. When the B contact is opened, the alarm is activated, and the single-phase three-wire high-low voltage transformer Tr1 is activated. Is warned that the low-voltage side electric circuit has ground fault.

The A contact of the output relay X2 is connected to a trip coil of a circuit breaker (not shown) connected to the low-voltage side electric circuit of the three-phase three-wire high / low voltage transformer Tr2. When the contacts are closed, the trip coil is excited and the circuit breaker is activated. The B contact of the output relay X2 is connected to an alarm device configured in the same manner as described above. When the B contact is opened, the alarm is activated, and the low-voltage side electric circuit of the three-phase three-wire high-low voltage transformer Tr2 is connected. Warns that a ground fault has occurred.

The operation indicators 13a and 13b connected to the output circuits 12a and 12b are composed of, for example, light emitting diodes, and are turned on when the output relays X1 and X2 are operating. Further, a power supply circuit 14 for generating a DC voltage to be supplied to each circuit of the low-voltage side electric circuit ground fault direction relay 1 is provided.

As described above, in the phase comparison circuits 9a and 9b of the low-voltage side electric circuit ground fault direction relay 1, any one of the single-phase three-wire high-low voltage transformer Tr1 and the three-phase three-wire high-low voltage transformer Tr2 is used. It is possible to determine whether or not the low-voltage side electric circuit has a ground fault, and it is possible to reliably operate only the circuit breaker of the low-voltage side electric circuit with the ground fault.

In the above embodiment, the high / low voltage transformers to be subjected to the ground fault determination are single-phase three-wire high / low voltage transformers Tr1 and Tr3.
Although the two-phase three-wire type high-low voltage transformer Tr2 is used, any circuit may be added in the low-voltage side electric circuit ground fault direction relay 1 according to the number of high-low voltage transformers to be subjected to ground fault determination. A number of high and low voltage transformers can be subjected to ground fault determination.

[0031]

According to the present invention, it is possible to detect which low-voltage side electric circuit of a plurality of high-and-low-voltage transformers whose low-voltage side windings are commonly grounded, and to detect the low-voltage side electric circuit with the ground fault. This has the effect that only the circuit breaker can be reliably operated.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a low-voltage side electric circuit ground fault direction relay.

FIG. 3 is an operation explanatory diagram of a phase comparison circuit.

FIG. 4 is an explanatory diagram of an operation of a phase comparison circuit.

FIG. 5 is an electric circuit diagram for explaining a conventional problem.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Low-voltage side ground fault relay 9a, 9b Phase comparison circuit 10a, 10b AND circuit 11a, 11b Time setting circuit 12a, 12b Output circuit X1, X2 Output relay Tr1 Single-phase three-wire high-low-voltage transformer Tr2 Three-phase three-wire Type high / low voltage transformer N Neutral point TE Low voltage side winding terminal ZCT0 Current detector ZCT1 Current detector ZCT2 Current detector EB Class B ground pole EBL0 Ground bus EBL1 Ground wire EBL2 Ground wire

Claims (2)

[Claims] 1. A low-voltage side ground fault relay for determining a low-voltage side electric circuit of a plurality of high / low voltage transformers whose low-voltage side winding is grounded to a common grounding pole, wherein the common grounding pole is provided. Is compared with the phase of the ground fault current flowing through the ground bus connected to the ground bus connected to the ground bus connected to the predetermined ground point of each of the low voltage side windings and the ground bus. A low voltage side electric circuit ground fault direction relay provided with a detecting means for detecting the low voltage side electric circuit caused by the ground fault. 2. The low voltage side electric circuit ground fault direction relay which operates the circuit breaker of the low voltage side electric circuit which detected the ground fault.