JPH08242528A - Ground fault protection system - Google Patents

Abstract

PURPOSE: To make it possible to eliminate noises in signal transmission lines, the reduction of the amount of signals, and the influence of signal reflection. CONSTITUTION: A ground fault protection relay 1 and a plurality of directional ground relays 2a, 2b, ... are connected through an optical star coupler 3 using optical fibers 5 to a high-voltage distribution system composed of buses and a plurality of distribution lines Fa, Fb, .... Fed with zero-phase voltage detected at the buses, the ground fault protection relay 1 produces pulse signal output if the zero-phase voltage is equal to or above a setting value. The directional ground relays 2a, 2b, ... are fed with the pulse signal, and placed in the distribution lines Fa, Fb, ....

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connection form of a ground fault protection relay and a plurality of ground fault direction relays in a high voltage distribution system composed of a bus bar and a plurality of distribution lines connected to the bus bar.

[0002]

2. Description of the Related Art In power transmission and distribution equipment, system conditions are constantly monitored, and if a ground fault or a short-circuit fault occurs, it is immediately detected to identify the fault section and promptly eliminate the cause of the fault from the system. Sending a shutdown command to 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. 5 is generally widely used. The configuration and operation of this power distribution system will be briefly described with reference to FIG. 5. A zero-phase voltage detector (hereinafter, Z) for measuring the zero-phase voltage V ₀ of the bus is provided on the bus.
It is called PD. ) Is connected. The zero-phase voltage V ₀ detected by this ZPD is the ground fault protection relay 1 connected to the ZPD.
Sent to In the ground fault protection relay 1, when the input zero-phase voltage V ₀ is equal to or higher than a preset set value, the voltage value is converted into a pulse waveform of a constant level and transmitted to a plurality of ground fault direction relays described later. .

On the other hand, from the above-mentioned bus bar, a plurality of distribution lines F
a, Fb, ... are branched, and there are a circuit breaker CB for breaking the system, a zero-phase current transformer (hereinafter, Z) for detecting a fault current.
It is called CT. ) Are connected respectively. The ground fault direction relay is normally connected to a plurality of distribution lines Fa, Fb, ... Through ZCT. Each ZCT detects a zero-phase current I ₀ generated in each distribution line due to a ground fault or the like, and outputs the current value to a connected local fault direction relay to a two-core, shielded twisted pair wire 4. To send over. The twisted pair wire 4 is connected from the ground fault protection relay 1 to the ground fault direction relay 2a, and from the ground fault direction relay 2a to the ground fault direction relay 2b.
The wires are connected in a continuous fashion.

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 pulse signal of the zero phase voltage V ₀ input from the ground fault protection relay 1 with the phase of the zero phase current I ₀ detected by ZCT. Then, the ground fault direction relay 2a outputs a phase determination output to a trip coil (not shown), opens the circuit breaker CB, and disconnects the distribution line Fa from the bus bar if it exceeds the preset operation range. .

[0006]

By the way, the zero-phase voltage V
The connection line between the ground fault protection relay 1 to which the ₀ pulse signal is sent and the ground fault direction relay 2a and between the ground fault direction relays is a two-core, shielded twist.
The voltage level of the pulse signal flowing through the wire pair 4 is normally DC 12V. Therefore, if the distance between the devices connected by the twisted pair wire 4 becomes long,
The pulse signal is distorted due to the influence of external noise, attenuation of the signal amount, reflection of the signal, etc., which causes malfunction of the ground fault direction relay 2a.

If there is a device that generates a large current in the vicinity of the laid signal cable, an AC induction voltage (noise) generated by the large current generation source may be mixed in the pulse signal of the signal line. In order to prevent this mixture, it is necessary to take measures such as passing the signal cable through an iron pipe.
It was causing an increase in cost. Therefore, an object of the present invention is to provide a ground fault protection system in which a ground fault protection relay and a plurality of ground fault direction relays are connected using an optical fiber via an optical star coupler to eliminate the influence of noise and the like. Is.

[0008]

A ground fault protection system for achieving the above object is a zero-voltage detected on the busbar in a high voltage distribution system composed of a busbar and a plurality of distribution lines connected to the busbar. If a phase voltage is input and the zero-phase voltage is equal to or greater than a set value, a ground fault protection relay that outputs a pulse signal, and a plurality of ground fault direction relays that input the pulse signal and that are arranged in the distribution line Is connected by an optical fiber via an optical star coupler.

[0009]

According to the above construction, the ground fault protection relay and the plurality of ground fault direction relays are connected by the optical fiber via the optical star coupler. Therefore, the influence of noise on the signal transmission path, attenuation of the signal amount, and reflection of the signal can be eliminated.

[0010]

Embodiments of the present invention will now be described with reference to the accompanying drawings.
And will be described in detail. FIG. 1 shows an embodiment of the present invention.
FIG. 3 is a connection system diagram for ground fault protection. Device configuration of this connection system
The operation will be described with reference to FIG. 1.
Zero-phase voltage V₀ZPD for measuring
Zero-phase voltage V detected by ₀Is a ground fault connected to ZPD
It is sent to the protection relay 1. In the ground fault protection relay 1, input
Zero-phase voltage V₀Is above the preset value
In that case, the voltage value is converted into a constant level pulse waveform.
Furthermore, the pulse output is sent to an E / O converter (not shown).
More electrical signals are converted into optical signals, and the optical signals are converted into optical signals.
To the coupler 3 via the optical fiber 5.

The optical star coupler 3 splits one input optical signal into a plurality of optical signals and outputs them from a plurality of terminals. Specifically, the optical star coupler is shown in FIG.
As described above, a rectangular parallelepiped structure called a mixing block 6 is formed, and a plurality of optical fibers 5 are connected for input and output. The figure shows the case where the number of input / output ports is 8 × 8. FIG. 3 shows a cross-sectional structure of the optical star coupler,
A plurality of input optical fibers 5 and a plurality of output optical fibers 5'are collectively coupled at the central portion. Therefore,
When an input signal from the ground fault protection relay 1 is input from any one of the optical fibers 5, the signal is split into each output optical fiber 5 '. The optical signal insertion loss of the optical star coupler is usually 3 to 4 dB.

Returning to FIG. 1, the optical signal output from the optical star coupler 3 is composed of a plurality of ground fault direction relays 2a, which will be described later.
2b, ... Are input via the optical fiber 5, respectively.
On the other hand, a plurality of distribution lines Fa, Fb, ...
Is branched, and a circuit breaker C that cuts off the system
B, ZCT for detecting the fault current is connected. Each ZCT
Detects a zero-phase current I ₀ generated in each distribution line due to a ground fault or the like, and transmits the current value to a connected local fault direction relay.

The local fault direction relay converts an optical signal input from the ground fault protection relay 1 via the optical star coupler 3 and the optical fiber 5 from an optical signal to an electric signal by an E / O converter (not shown). Convert. In addition, the local relay direction relay,
The phase of the converted zero-phase voltage V ₀ pulse is compared with the phase of the zero-phase current I ₀ detected by ZCT. In the phase determination circuit (not shown) provided inside the ground fault direction relay, for example, when the zero phase voltage V ₀ input from the ground fault protection relay 1 is used as a reference, the phase of the zero phase current I ₀ is Delay 4
If it goes from 5 ° and is in the range of 135 ° (see Fig. 4)
Then, the phase determination output is output to a trip coil (not shown). Then, the local fault direction relay opens each breaker CB and disconnects each distribution line from the bus bar.

As described above, in this embodiment, the ground fault protection relay 1 using the optical star coupler 3 and the optical fiber 5 is used.
Even if the distance between the devices becomes long and external noise is generated due to the connection between the relays and the relays in each direction, the noise is prevented from being mixed because the optical fiber 5 electrically insulates the external noise. In addition, noise countermeasures for the cable are not required because the optical fiber 5 is used, and since the installation work of the optical fiber cable is easy, the cost for constructing the transmission path can be suppressed.

The optical star coupler 3 is preferably classified according to the number of signal input / output ports (for example, 8 × 8, 16 × 16, etc.) and used according to the applied high voltage system.

[0016]

As described above, according to the ground fault protection system of the present invention, the ground fault protection relay and the plurality of ground fault direction relays are connected by the optical fiber via the optical star coupler, thereby transmitting the signal. It is possible to eliminate the effects of noise on the path, attenuation of the signal amount, and reflection of the signal, and it is possible to provide a good signal transmission path.

Further, when the optical fiber is used, the laying work thereof is easy, so that the cost can be suppressed.

[Brief description of drawings]

FIG. 1 is a connection system diagram of ground fault protection according to an embodiment of the present invention.

FIG. 2 is an external view of an optical star coupler having 8 × 8 input / output ports.

FIG. 3 is a cross-sectional structure diagram of an optical star coupler having 8 × 8 input / output ports.

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

FIG. 5 is a connection system diagram of conventional ground fault protection.

[Explanation of symbols]

 1 Ground fault protection relay 2 Ground fault direction relay 3 Optical star coupler 5 Optical fiber ZPD Zero phase voltage detector ZCT Zero phase current transformer

Claims (1)

[Claims] 1. In a high-voltage distribution system composed of a bus bar and a plurality of distribution lines connected to the bus bar, a zero-phase voltage detected by the bus bar is input, and if the zero-phase voltage is a set value or more, A ground fault protection relay that outputs a pulse signal, and a connection between a plurality of ground fault direction relays that input the pulse signal and that are arranged in the distribution line are configured by an optical fiber via an optical star coupler. A characteristic ground fault protection system.