JPH08242529A - Signal output circuit of ground fault protection relay - Google Patents

Abstract

PURPOSE: To eliminate problems, such as the production of ripples in signals passing through the shielded wires between a ground fault protection relay and a directional ground relay and a ground directional relay the incapability of the directional ground relay to test the phase judging function by itself, and thereby enhance reliability. CONSTITUTION: When connecting a ground fault protection relay 1 and a directional ground relay 2a, a photocoupler circuit is used for the output circuit of the ground fault protection relay 1. As a result the voltage of the photocoupler 21a is fed from the power supply to the directional ground relay, and thus the ground fault protection relay 1 is electrically insulated from the directional ground relay 2a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention inputs a zero-phase voltage detected on a bus, and if the zero-phase voltage is a set value or more,
The present invention relates to a signal output circuit of a ground fault protection relay that converts a zero-phase voltage into a pulse signal and outputs the pulse signal.

[0002]

2. Description of the Related Art In power transmission and distribution equipment, system conditions are constantly monitored, and if a ground fault or short-circuit fault occurs, it is immediately detected to select a fault section and promptly remove the cause of the fault from the system. Sending a shutdown command to a circuit breaker is an important responsibility. Protective relays are typically used for these responsibilities.

In the case of a high voltage distribution system in which a plurality of distribution lines are connected from one bus bar, the ground fault protection connection system shown in FIG. 2 is generally widely used. The configuration and operation of this power distribution system will be briefly described with reference to FIG. 2. The busbar has a zero-phase voltage detector (hereinafter, referred to as ZPD) for measuring the zero-phase voltage of the busbar.
Say. ) Is connected. The zero-phase voltage detected by this ZPD is sent to the ground fault protection relay 1 connected to ZPD. In the ground fault protection relay 1, when the input zero-phase voltage is equal to or higher than a preset setting value, the voltage value is converted into a pulse waveform of a constant level and transmitted to the ground fault direction relay 2a.

On the other hand, from the above-mentioned bus bar, a plurality of distribution lines F
a, Fb, ... are branched, and a circuit breaker CB for interrupting the system, a zero-phase current transformer for detecting a fault current (hereinafter, Z
It is called CT. ) Is connected. The ZCT detects a zero-phase current generated in each distribution line due to a ground fault or the like, and sends the current value to the connected ground fault direction relay 2a. Although not shown in FIG. 2, the ground fault direction relay is usually connected to a plurality of distribution lines via a zero-phase current transformer. Therefore, the ground fault protection relay 1 described above transmits a pulse signal to the plurality of ground fault direction relays.

The ground fault direction relay is a relay which detects in which direction the fault point is by inputting two different amounts of electricity and identifying the phase relationship between them. Therefore,
The ground fault direction relay 2a compares the phase of the zero phase voltage pulse input from the ground fault protection relay 1 with the phase of the zero phase current detected by ZCT. And the ground fault direction relay 2a
Outputs a phase determination output to a trip coil (not shown) if the operating range exceeds a preset value, and the circuit breaker C
Open B and disconnect the distribution line Fa from the busbar.

Next, FIG. 3 shows a circuit diagram of a connection interface section between the ground fault protection relay 1 and the ground fault direction relay 2a. According to FIG. 3, the ground fault protection relay 1 converts the zero-phase voltage input from the ZPD into a pulse signal. The signal is pulled up by the voltage of DC 12V via the inverter 11 and sent to the ground fault direction relay 2a via the two-core, shielded twisted pair wire 12.

The pulse signal input to the ground fault direction relay 2a is pulled up by the voltage of DC12V similarly to the output of the ground fault protection relay 1, passes through the inverter 13, and is input to the phase determination circuit 15 via the NOR gate 14. It In this phase determination circuit, the phase of the zero-phase voltage pulse signal and Z
The phase of the zero-phase current detected by CT is compared. Also,
A test function is provided on the ground fault direction relay 2a side. In this, a test signal can be generated from the test waveform generation circuit 16 and the phase determination function of the phase determination circuit 15 can be confirmed. The test signal of the test waveform generation circuit 16 is input to the phase determination circuit 15 via the inverter 18 and the NAND gate 14.

[0008]

Since both the ground fault protection relay 1 and the ground fault direction relay 2a are provided with a DC 12V power source, when a potential difference occurs between these two power source voltages, the shielded wire 12 is not affected. A potential difference current flows, and the pulse waveform 1 for the impedance of the shielded wire 12
Ripple occurs. Due to this ripple component, the pulse waveform of the ground fault protection relay 1 transmitted to the ground fault direction relay 2a is disturbed, and the pulse signal cannot be accurately received on the ground fault direction relay 2a side.

When the power supply on the side of the ground fault protection relay 1 goes down for some reason, the output of the inverter 13 of the ground fault direction relay 2a remains held at "HIGH" level, and the output of the NOR gate 14 becomes Fixed to "LOW" level. Therefore, the input signal from the other input terminal of the NOR gate 14, that is, the test signal from the test waveform generation circuit 16 is not sent to the phase determination circuit 15, and the phase determination function test cannot be performed.

Therefore, an object of the present invention is to provide a ground fault protection relay which eliminates the above problems by replacing the circuit of the connection interface section for the ground fault direction relay of the ground fault protection relay with a photocoupler circuit. Is.

[0011]

The present invention is directed to a ground fault which inputs a zero-phase voltage detected on a bus and, if the zero-phase voltage is a set value or more, converts the zero-phase voltage into a pulse signal and outputs the pulse signal. In the protection relay, the output circuit that outputs the pulse signal is composed of a photocoupler.

[0012]

According to the above construction, in the connection between the ground fault protection relay and the ground fault direction relay, the output circuit of the ground fault protection relay is a photocoupler circuit. Therefore, the voltage of the photocoupler is supplied from the power source of the ground fault direction relay, and the ground fault protection relay and the ground fault direction relay are electrically insulated.

Therefore, there is no problem that a ripple occurs in the signal between the ground fault protection relay and the ground fault direction relay configured by the shielded wire, or the phase judgment function cannot be tested by the ground fault direction relay itself. can do.

[0014]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the description of this embodiment, the above-mentioned FIG.
See again. A ZPD for measuring the zero-phase voltage of the busbar is connected to the busbar. The zero-phase voltage detected by this ZPD at the time of ground fault is the ground fault protection relay 1 connected to ZPD.
Sent to In the ground fault protection relay 1, when the input zero-phase voltage is equal to or higher than a preset setting value, the voltage value is converted into a pulse waveform of a constant level and transmitted to the ground fault direction relay 2a.

On the other hand, a distribution line Fa is branched from the bus bar, and a breaker CB for cutting off the system and a ZCT for detecting a fault current are connected to the distribution line Fa. The ZCT detects a zero-phase current generated in each distribution line due to a ground fault or the like, and sends the current value to the connected ground fault direction relay 2a. The ground fault direction relay is not shown in FIG.
Usually, it is connected to a plurality of distribution lines via a zero-phase current transformer.
Therefore, the ground fault protection relay 1 described above transmits a pulse signal to the plurality of ground fault direction relays.

The ground fault direction relay 2a is a ground fault protection relay 1
The phase of the zero-phase voltage pulse input from the above is compared with the phase of the zero-phase current detected by ZCT. And if the ground fault direction relay 2a exceeds the preset operation range,
Output the phase judgment output to the trip coil (not shown),
The breaker CB is opened and the distribution line Fa is disconnected from the bus bar.

Next, FIG. 1 shows a circuit diagram of a connection interface section between the ground fault protection relay 1 and the ground fault direction relay 2a, which is a feature of the present invention. According to FIG. 1, the ground fault protection relay 1 converts the zero-phase voltage into a pulse signal when the zero-phase voltage input from the ZPD is equal to or higher than a preset set value. The pulse waveform is connected to the photocoupler 21a, which is a feature of the present invention, via the inverter 11. If a ground fault occurs, the pulse signal output is electrically insulated by the photocoupler 21a and sent to the ground fault direction relay 2a via the two-core, shielded twisted pair wire 12. This signal output is normally DC12V
DC voltage of.

The pulse signal input to the ground fault direction relay 2a is pulled up by the voltage of DC12V, passes through the inverter 13 and the NOR gate 14, and is input to the phase determination circuit 15. In this phase determination circuit, the phase of the pulse signal of the zero phase voltage and the phase of the zero phase current detected by ZCT are compared. In this phase determination circuit 15, for example, when the zero-phase voltage input from the ground fault protection relay 1 is used as a reference, the phase of the zero-phase current is in the range of 45 ° to 135 ° (see FIG. 4). ) To the trip coil (not shown).

A test function is provided on the side of the ground relay 2a. This is because when the zero-phase voltage pulse output from the ground fault protection relay 1 is not present, the switch 17 is switched to generate a test signal from the test waveform generation circuit 16 and the phase determination function can be confirmed. The test signal of the test waveform generating circuit 16 is the inverter 18 and the NA.
It is input to the phase determination circuit 15 via the ND gate 14. This test signal has the same pulse waveform as the signal output by the ground fault protection relay 1.

Since the ground fault protection relay 1 outputs a pulse to a plurality of ground fault protection relays,
A plurality of the photo coupler circuits described above are also provided. For example, in the other ground-fault direction relay 2b shown in FIG. 1, the photocoupler 21b of the ground-fault protection relay 1 is connected via the shielded pair wire 12.
Is connected. In this way, by configuring the connection interface for the ground fault direction relay 2a on the side of the ground fault protection relay 1 with the photocoupler circuit, no power supply is required on the side of the ground fault protection relay 1. Therefore, conventionally, the potential difference generated between the two power source voltages of the ground fault protection relay 1 and the ground fault direction relay 2a does not occur, and the ripple generated in the pulse waveform of the impedance of the shield wire 12 does not occur.

Further, when the power supply on the ground fault protection relay 1 side is down for some reason, the output of the NOR gate 14 is fixed to the "LOW" level, so that the test signal from the test waveform generating circuit 16 is out of phase. The problem that the phase determination function test cannot be carried out because it is not sent to the determination circuit 15 is solved. Further, in the conventional circuit, the signal line from the ground fault protection relay 1 is connected to one ground fault direction relay 2a, and is connected in series from that ground fault direction relay to another ground fault direction relay. (See Figure 3). Therefore, if an accident such as a disconnection occurs in any of the connection lines, the signal of the ground fault protection relay will not be transmitted to the subsequent ground fault direction relays connected by the connection line.

However, in the present invention, by forming the transmission circuit of the ground fault protection relay with a photocoupler, the ground fault protection relay can connect a plurality of ground fault direction relays in parallel. Therefore, it is possible to minimize defects due to disconnection and the like.

[0023]

As described above, according to the ground fault protection relay of the present invention, by forming the output circuit of the pulse output of the ground fault protection relay by the photocoupler circuit, ripple occurs in the signal of the shielded wire. In addition, it is possible to eliminate problems such as the fact that the phase determination function cannot be tested by the ground fault direction relay itself, and reliability can be improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a connection portion of a ground fault protection relay and a ground fault direction relay according to an embodiment of the present invention.

FIG. 2 is a connection system diagram showing an example of ground fault protection in a high-voltage distribution system.

FIG. 3 is a circuit diagram of a connection portion of a conventional ground fault protection relay and a ground fault direction relay.

FIG. 4 is a vector diagram illustrating an operation range of a ground fault direction relay.

[Explanation of symbols]

 1 Ground fault protection relay 2a, 2b Ground fault direction relay 21a, 2b Photocoupler ZPD Zero phase voltage detector ZCT Zero phase current transformer

Claims (1)

[Claims] 1. A ground fault protection relay for inputting a zero-phase voltage detected on a bus and, if the zero-phase voltage is a set value or more, converting the zero-phase voltage to a pulse signal and outputting the pulse signal. A signal output circuit of a ground fault protection relay, wherein an output circuit for outputting is composed of a photo coupler.