JP2000037010A - Ground detection method of gas-insulated switchgear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the ground by utilizing the shielding case of a current transformer and eliminate the gas ground transformer(GPT) of a gas-insulated switchgear(GIS). SOLUTION: The shielding cases 22 of the main circuit current detecting CTs of the respective phases of a GIS have capacitances C1 between the main circuit conductors 21 of the GIS and themselves respectively. The shield cases 22 of the respective phases are connected to each other with conductors 24. A voltage dividing capacitor C2 is connected between the conductors 24 and the ground and monitored. When the ground does not exist, voltage vectors generated by the capacitances C1 of the respective phases cancel each other and hence a voltage is not applied to the voltage dividing capacitor C2. If the one-line ground exists, the relations between the voltage vectors generated by the capacitors C1 of the respective phases collapse and hence a voltage is applied to the voltage dividing capacitor C2. Therefore, the ground can be detected by monitoring the voltage of the voltage dividing capacitor C2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for detecting a ground fault in a gas insulated switchgear, and more particularly to a method for detecting a ground fault in a gas insulated switchgear which can omit a grounding transformer unit.

[0002]

2. Description of the Related Art In a gas insulated switchgear (GIS), a charging part of a switchgear component such as a bus breaker, a disconnector, a lightning arrestor, etc. is arranged almost at the center of a cylindrical grounded metal tank, and an insulating spacer or the like is used. supporting, it has a structure filled with an insulating gas such as SF ₆ therein.

FIGS. 5 and 6 show a GIS single-wire connection diagram and a GIS tank connection status in a double-bus transmission and distribution substation. The GIS is unitized into a receiving line / transmission line unit 1, a transformer circuit unit 2, a bus connecting circuit unit 3, a grounding transformer unit 4, etc., and a metal tank 31 constituting each unit is connected by a bus line 32. Have been.

Generally, the GIS has the gas ground transformer (GIS) unit 4 as described above, and the GPT has a primary winding connected to a bus, a secondary winding for an instrument, and a tertiary winding for zero-phase voltage detection. Have.

[0005] As shown in FIG. 7, the neutral point of the primary winding of the GPT is grounded, and the tertiary winding is connected with broken delta connection and limiting resistors R 1 at both ends, thereby generating a zero-phase voltage V generated at the time of ground fault. Ground fault is detected by detecting ₀ . This G
The zero-phase voltage detected by the PT activates the directional ground fault relay 67G1 or 67G2, and the fault circuit is released by the circuit breaker CB1 or CB2 to eliminate the ground fault.

[0006]

As described above, since the GPT unit 4 is connected to the GIS as a part of the GIS, the ratio of the GIS to the entire GIS increases, and the GIS cannot be reduced in size.

[0007] Further, since the inside of the GPT is formed by windings like a transformer, the reliability of the GIS itself may be reduced due to disconnection of the windings, deterioration of insulation, and the like.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for detecting a ground fault of a gas insulated switchgear capable of reducing the size of a device and improving reliability. It is in.

[0009]

According to a method of detecting a ground fault in a gas insulated switchgear of the present invention, a shield case of a current transformer of each phase for detecting a main circuit current is connected by a conductor, and between the conductor and ground. It is characterized by connecting a voltage dividing capacitor that forms a voltage dividing circuit by the capacitance between the main circuit and the shield case, and detecting a ground fault by detecting the voltage generated in this voltage dividing capacitor. is there.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a GIS receiving / transmitting line unit, 11 is a cable connecting section, 12 is a breaker section, 13 is a breaker operating section, 14 is a disconnecting section, and 15 is a disconnecting section. It is a unit monitoring panel.

FIG. 2 is an enlarged view of a current transformer (CT) installation portion of the interrupting section 12 indicated by an arrow a in FIG.
22 is a CT shield case for detecting the main circuit current, 2
3 is a tank wall of a circuit breaker part, 24 is each CT of R, S, T phase.
A conductor 25 for connecting the shield case 22 to the shield case 22; an insulating spacer 25 for extracting the conductor 24 from the tank wall 23;
C1 is a capacitance existing between the main circuit conductor 21 and the shield case of the CT, and C2 is a voltage dividing capacitor connected between the conductor 34 and the ground to form a series circuit with the capacitance C1.

FIG. 3 shows a ground fault detection (zero-phase voltage detection) circuit.
C1 _R , C1 _S , and C1 _T are capacitances between the main circuit phase conductors and the shield case of each phase CT, and C2 is connected between the conductor 24 connecting each phase shield case 22 and ground. A voltage dividing capacitor, TR is a transformer connected in parallel with the voltage dividing capacitor C2, ZD is a Zener diode for limiting the primary voltage of the transformer TR, and RF is a transformer TR.
A is an amplifier that amplifies the rectified voltage, and CP is a comparator that compares the output of the amplifier A with a set value and outputs a zero-phase voltage detection signal.

The operation of the zero-phase voltage detection circuit will be described.
Since the capacitances C1 _R , C1 _S and C1 _R are equal, FIG.
As shown in (a), when the three-phase voltages of the main circuit are balanced, the voltage vector of each phase acts in the cancel direction.
No zero-phase voltage is generated. Therefore, no voltage V2 is generated in the voltage dividing capacitor C2.

When a single-line ground fault occurs, for example, when the R-phase is completely grounded, the R-phase voltage becomes 0 and the vector relationship of the voltages generated in the capacitances C1 _R , C1 _S , and C1 _R is lost, and FIG. As shown, a zero-phase voltage V _O is generated, and a voltage V2 is generated in the voltage dividing capacitor C2.

This voltage V2 is boosted by the transformer TR, rectified by the rectifier RF, further amplified by the amplifier A, and compared with the set value by the comparator CP. Thus, the comparator CP outputs a zero-phase voltage detection signal when the output of the amplifier A is larger than the set value. Therefore,
A ground fault can be detected without using a GPT.

In the above embodiment, the zero-sequence voltage is detected by using the CT of the main circuit of the receiving / transmission line unit. However, the main circuit CT of another unit may be used.

[0017]

Since the present invention is configured as described above, the following effects can be obtained.

(1) Since the GPT unit of the GIS can be omitted, the entire GIS can be reduced in size.

(2) The cost of the GIS is reduced by the above (1).

(3) The reliability of the GIS is improved because there is no winding such as the GPT detected by the ground fault.

(4) Since the connection work of the GPT unit is eliminated, the installation period of the GIS can be shortened.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a GIS receiving / transmission line unit according to a first embodiment.

FIG. 2 is an explanatory diagram of a configuration of a part in FIG. 1;

FIG. 3 is a ground fault detection circuit diagram.

FIG. 4 is a voltage vector diagram of each phase.

FIG. 5 is a single-line connection diagram showing a connection example of a GIS of a double-bus transmission and distribution substation.

FIG. 6 is a plan view and a front view of the GIS showing a GPT connection state of the GIS.

FIG. 7 is a circuit diagram illustrating a zero-phase voltage detection method using a conventional GPT.

[Description of Signs] 1 ... GIS receiving / transmission line unit 2 ... GIS transformer circuit unit 3 ... GIS busbar communication unit 4 ... GIS GPT unit 11 ... Cable connection unit 12 ... Circuit breaker unit 13 ... Circuit breaker Operation part 14 disconnecting part 15 unit monitoring part 21 main circuit conductor 22 CT shield case 23 tank wall 24 connection wire 25 insulating spacer 31 metal tank 32 bus line C1 main circuit conductor and CT Capacitance between shield cases C2: Voltage dividing capacitor RF: Rectifier CP: Comparator GCB: Gas circuit breaker GPT: Gas ground transformer DS: Disconnector ES: Ground switch LA: Lightning arrester CT, BCT: Current transformer CH: Cable head.

Claims (1)

[Claims] 1. A shield case of a current transformer of each phase for detecting a main circuit current is connected by a conductor, and a voltage dividing circuit is formed between the conductor and the ground by a capacitance between the main circuit and the shield case. A method for detecting a ground fault in a gas insulated switchgear, comprising connecting a voltage dividing capacitor and detecting a voltage generated in the voltage dividing capacitor to detect a ground fault.