JP2000077247A - Zero-phase voltage detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the zero-phase voltage of a distribution system without using exclusive GPT or ZPD. SOLUTION: This zero-phase voltage detecting device is formed of bushings IIA-11C positioned at the distribution line leading-in part of a power equipment or the like, in which shield boards 13 for preventing electric field concentration are provided as in a concentric circular cylinder in the outer peripheries of inside conductors 12, connected with distribution lines 9A-9C and outside connecting terminals 15 are connected with the shield boards 13, and a detecting capacitor 7 whose one edge is connected with the outside connecting terminals 15 of the bushings 11A-11C and whose other edges are connected with the ground, and a detecting part for voltage-dividing the zero-phase voltage of a distribution line system by a capacitor type transformer formed of an electrostatic capacity between the inside conductors 12 and the shield boards 13 of the busings 11A-11C and the detecting capacitor 7, and for detecting the zero-phase voltage from the inter-terminal voltage of the detecting capacitor 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zero-phase voltage detecting device for detecting a zero-phase voltage of a distribution system.

[0002]

2. Description of the Related Art Conventionally, a dedicated GPT or ZPD is used for detecting a zero-phase voltage at the time of a ground fault in a distribution system.

FIG. 3 shows a conventional zero-sequence voltage detection using a GPT.
1 shows a device and a distribution line 1 for each phase of a distribution system 1_A,
1_B, 1_CTo each phase winding 2 on the primary side of GPT2._A,
2_B, 2 _CIs connected and the ground fault of distribution system 1 occurs.
When raw, secondary winding 2 of GPT2_XGenerates a zero-phase voltage,
This zero-sequence voltage is applied to the ground fault detection relay 3, and the
The relay 3 detects the zero-phase voltage and performs a necessary relay operation.

FIG. 4 shows a conventional zero-sequence voltage detection using a ZPD.
1 shows a device and a distribution line 4 of each phase of a distribution system 4_A,
4_B, 4_CThe capacitor 5 of each phase of ZPD5_A,
5_B, 5 _CIs connected to one end of each capacitor 5_A
~ 5_CIs connected to the primary side of the ground fault detection relay 6.
Grounding via the densa 7 causes a ground fault in the power distribution system 1.
On the raw side, the zero-phase voltage of_A~ 5_CWhen
The voltage is divided by the capacitor type transformer with the capacitor 7.
And a partial voltage of the zero-phase voltage is generated between the terminals of the capacitor 7.
You.

[0005] A primary winding of a transformer 8 for insulation and detection is connected between both ends of the capacitor 7, and a zero-phase voltage is applied to a secondary winding of the transformer 8 based on a voltage between terminals of the capacitor 7. Is generated.

[0006]

The conventional zero-sequence voltage detecting devices shown in FIGS. 3 and 4 are formed by using dedicated GPTs and ZPDs, and therefore require a space for installing them, and also reduce the cost. There is a problem that reduction cannot be achieved.

SUMMARY OF THE INVENTION It is an object of the present invention to detect a zero-phase voltage of a power distribution system without using a dedicated GPT or ZPD, thereby achieving space saving and cost reduction.

[0008]

In order to solve the above-mentioned problems, a zero-sequence voltage detecting device according to the present invention comprises an internal conductor connected to a distribution line, which is located at a lead-in point of a distribution line of a power device or the like. A shield plate for preventing electric field concentration is provided concentrically on the outer periphery, and a bushing for each phase in which an external connection terminal is connected to the shield plate and one end of a detection capacitor are connected to the external connection terminal of the bushing for each phase. Is grounded, the capacitor-type transformer formed by the capacitance between the inner conductor of each phase bushing and shield plate and the detection capacitor divides the zero-phase voltage of the distribution system, and the voltage between the terminals of the detection capacitor And a detection unit for detecting a zero-phase voltage from the detection signal.

[0009] Therefore, distribution lines of power equipment and the like
Conductor of each phase bushing located in the area and prevention of electric field concentration
The capacitance between the capacitor and the shield plate is
5_A , 5_B, 5_CAnd these capacitances and
Capacitor type transformer formed by the detection capacitor at the output
Thus, the zero-phase voltage of the distribution system is detected.

Therefore, it is possible to detect the zero-sequence voltage of the distribution system by using the bushings of each phase at the distribution line drop-in point without using the dedicated GPT or ZPD for detecting the zero-sequence voltage as in the related art. It is possible to detect a ground fault in the power distribution system while reducing the cost and cost.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
1 and FIG. Figure 1 shows the distribution system 9
Of each phase at the distribution line entry point of the attached switchgear 10
Thing 11_A, 11_B, 11_CDetect using
FIG._A, 9_B, 9_C
Are the distribution lines of each phase of the distribution system 9, 10_A, 10_B , 10
_CIs a main contact of each phase of the switchgear 10, and is a bushing.
11_A~ 11 _CDistribution line 9 via internal conductor 12 of
_A~ 9_CIt is connected to the.

[0012] Then, the bushing 11 _A to 11 _C are formed as shown in FIG. 2, the shield plate 13 for electric field concentration preventing a substantially central portion outer periphery of the inner conductor 12 is disposed concentrically cylindrical inner conductor 12 and Except for both ends of the internal conductor 12, the shield plate 13 is covered with an insulator 14 of an epoxy resin mold.

Further, the bushing ₁₁ A to 11 _C 1 or more external connection terminals 15 connected to the shield plate 13 through the insulator 14 is provided, these terminals 15
Is conventionally directly connected to the ground, but in this embodiment, is grounded via the detection capacitor 7 of the ground fault detection relay 6.

And, the bushing 11_A~ 11_Cof
Capacitance is generated between the inner conductor 12 and the shield plate 13
This capacitance is equal to the capacitor 5 of the ZPD of FIG._A~
5_C These capacitances and detection capacitors
And 7 form a capacitor type transformer.
Divides the zero-phase voltage of the distribution system 9 by the detection capacitor.
A zero-phase voltage (divided voltage) is generated between the terminals of the capacitor 7.

Further, the detecting capacitor 7 and the transformer 8 form a zero-phase voltage detecting section.
A detection signal of a zero-phase voltage between the terminals of the detection capacitor 7 is output from the secondary side, and a ground fault of the power distribution system 9 is detected based on the detection signal.

The bushings 11 _A to 11 _B of the switchgear 10 at the distribution line drop-in point instead of the dedicated GPT or ZPD.
Since the zero-phase voltage of the power distribution system 9 can be detected using 11 _C , the GPT and the ZPD can be omitted, and the installation space is not required.

Of course, bushings of each phase of various power devices other than the switchgear may be used.

In the above-described embodiment, the detecting portion is formed by the detecting capacitor 7 and the transformer 8 of the ground fault detecting relay 6, but the detecting capacitor 7 and the transformer 8 of the relay other than the ground fault detecting relay are formed. The detection unit may be formed by a detection capacitor and a transformer corresponding to the above.

[0019]

The present invention has the following effects. The capacitance between the shield plate 13 of each phase of the bushing 11 _A to 11 _C of the inner conductor 12 and the electric-field concentration preventing located distribution line pull points such as power devices, corresponding to each phase of the capacitor ZPD Then, the zero-phase voltage of the power distribution system 9 can be detected by the capacitor type transformer formed by the capacitance and the detection capacitor 7 of the detection unit.

[0020] Thus, as in the prior art without using the zero-phase voltage detection dedicated GPT and ZPD, detection of the zero-phase voltage of the distribution system 9 using a bushing 11 _A to 11 _C of each phase of the distribution line pull point It is possible to detect a ground fault in the power distribution system 9 while reducing the space and cost.

[Brief description of the drawings]

FIG. 1 is a connection diagram of one embodiment of the present invention.

FIG. 2 is a connection diagram in a state where the bushing of FIG. 1 is cut.

FIG. 3 is a connection diagram of an example of a conventional device.

FIG. 4 is a connection diagram of another example of the conventional device.

[Explanation of symbols]

7 sensing capacitor 9 distribution system 11 _A to 11 _C bushing 12 the inner conductor 13 shield plate

Claims (1)

[Claims] 1. A shield plate for preventing electric field concentration is provided in a concentric cylindrical shape around an inner conductor connected to a distribution line, which is located at a lead-in point of a distribution line of a power device or the like, and an external connection terminal is provided on the shield plate. One end of the connected bushing and one end of the detection capacitor is connected to the external connection terminal of the bushing of each phase, the other end of the detection capacitor is grounded, the internal conductor of the bushing of each phase, and the shield plate. The capacitor-type transformer formed by the capacitance between the capacitor and the detection capacitor divides the zero-phase voltage of the distribution system,
A zero-phase voltage detection device, comprising: a detection unit that detects the zero-phase voltage from a voltage between terminals of the detection capacitor.