JPS6026413A - Ground-fault protecting relaying method and relay - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention When a one-line complete ground fault occurs at point P of the high voltage or extra high voltage electrical circuit (1) shown in Figure 1, the ground fault current Ig
flows through the ground-to-ground capacitance of the distribution line to the other two lines that are not grounded, and returns to the transformer (2). That is, depending on the magnitude of the ground electrostatic capacity of each electric line, Ic1 to Ic
4 and ■ becomes CO and flows into the transformer (2).

Conventionally, to detect and cut off a ground fault line, the electric line (1)
The zero-phase voltage ■0 generated between the neutral point and the ground is detected by a zero-phase voltage detector ZPD such as a grounding capacitor or a grounding transformer, and this is supplied to each ground fault direction relay DGR as a judgment reference signal. However, in the ground fault direction relay DGR, a method is adopted in which the phase of the zero-sequence current coming in from the zero-sequence current transformer ZC'I' is discriminated based on its phase, and it is output only when the white line is in the ground fault direction. , in this method,
When installing the zero-phase voltage detector ZPD, there are various disadvantages such as the necessity of cutting off the electrical circuit and the need for a reliable device, which increases the production cost and construction cost of the device.

The present invention utilizes the output current of a zero-phase current transformer installed in each feeder in a high-voltage distribution system consisting of six or more distribution lines, and uses the output current of a fault line current transformer to takes advantage of the fact that there is only one circuit, and the phase difference between the output current of the zero-phase current transformer installed in the faulty circuit and the output current of the zero-phase current transformers of multiple other healthy circuits is different,
9. Sum of the phases of these multiple zero-phase current transformer output currents without using ZPD. With this phase, each zero phase current transformer ZC
The present invention aims to provide a ground fault protection relay method and a relay which can eliminate the above-mentioned conventional drawbacks by detecting and cutting off a ground fault line by phase-differentiating the output current of T.

First, an embodiment of the method of the present invention will be explained with reference to FIGS. 2 to 4. (3) is a high-voltage distribution system consisting of distribution lines of F1 to F404 lines, ZCT+ to ZCT 4
are zero-phase current transformers installed on each distribution line, DGR+~DGR
Reference numeral 4 denotes a ground fault direction relay according to the present invention, which is connected to the secondary output terminal of each zero-phase current transformer. The sensitivity current setting circuit (5) which inputs the secondary output current of It consists of a phase discriminator circuit (7) to output, and a circuit (6) for each fault direction relay DGR-1 to DGR4.
) is a common connection.

Now, if a one-line complete ground fault occurs at point P of the high-voltage distribution system (3), each distribution line F1 to F4 has a ground capacitance Ji
The currents c1 to IC4 flow through C+ to C4, and the ground fault current Ig flows through the fault line F4, superimposed on the current IC4. Therefore, ZC of accident line F4
The current passing through TA is the difference between Ig and IC4. Since this current is Ig)Ic4, the transformer (8
) side toward the fault point P, and the incoming current IC1 to I (j is the ground capacitance of each distribution line F1 to F3 is 0
1 to C6, it flows from the ground to the wire and transformer (8)
It is destroyed by the current flowing towards.

In the above state, the secondary output current from the zero-phase current transformer ZC'T 4 passes through the sensitivity current setting circuit (5) and is input to the phase discrimination circuit (force) and the amplitude limiting amplification circuit (6).
The signal is then input to other ground fault direction relays DGR+ to DGR3.

Therefore, the current applied to the reference phase input circuit of the phase discrimination circuit (7) is li! This becomes the composite value of the output currents that have passed through the amplitude limiting amplification circuits of the ground fault direction relays DGR1 to DGR4 of 11F1 to F4, and the two phases are also determined by this.

This phase is a healthy line) 1~F3's received current Ic+~I
The phase is representative of C3, and by using the necessary phase shift circuit, it is possible to always make the zero-phase current on the fault line side the positive output of the phase discrimination circuit (force output).

This can be written equivalently as shown in Figure 6. In addition,
In Fig. 6, ei-64 indicates each zero-phase current transformer ZCT1~
The voltage from the secondary output signal of ZCT 4 passes through the amplitude limit increase [1] circuit, R11 to R14 are output resistances for constant current, and R1 to R4 are load resistances. In the example of operation in this equivalent circuit, 'e1 to 6 are ZCTs due to direct currents.
The output phase, 24, is the signal voltage of the ZCT output phase due to the white line ground fault. Phase signal current 11~ generated by this voltage
I4 is connected to R1-R via the output resistors 'R, 11 to R14.
4 relay input resistances are superimposed on the load circuits connected in parallel. In addition, each relay input resistance R・1~1%4 is
Since they are set to have equal values, 1/4 of the sum of +1 to i4 flows through each joint, and the voltage generated by this current (eo = Rx (i
1+i2+13-1-i4)/4) becomes the ground fault direction determination reference signal. Figure 4 shows this in vector form.

Next, referring to Fig. 5, one embodiment of the earth fault directional relay according to the present invention will be explained. (1) is a current level detection circuit, (14) is a sensitivity current setting circuit, C1 group is a switching circuit, (a6) is an amplification circuit, and U power is a constant current. US+ is a phase discrimination circuit, and tt is an input circuit.

(20+l″j: phase shift circuit, 0I) is amplification circuit, (2
Enoki is a positive phase increase rlJ and switching circuit, (23
+ is a time-limited setting circuit, (2 is an opposite phase temporary lock circuit, C
5) is an anti-phase amplification and switching circuit, (26+
07) is the lock time setting circuit, 07) is the output switching circuit, (28) is the output relay circuit, (291 is the display circuit, side is the circuit that tests the main earth fault direction relay including the zero-phase current transformer ZCT, (311 is the This is a stabilized power supply circuit.

In the above circuit configuration, the secondary output due to the zero-sequence current detected by the zero-phase current transformer ZCT is supplied to the circuit (14) via two circuits 00) and αυ, and the sensitivity is set by the two circuits (14). It is converted into a voltage with a value corresponding to the current and is passed through two circuits (16
) is supplied to circuit Q8). On the other hand, some of the signals passing through circuits (10) and (11) are transferred to circuits (131, (151)
and (I7), it is connected (h, f2) to the ground fault direction relay DGR of another line. Circuit (1 and (15) limit the unnecessary output of unnecessary minute level 0 circuit ttS has a main fault direction relay and see the figure) 0 This phase signal is connected to the circuit (
20), the phase is shifted to an easily usable phase. The ground fault direction determination reference phase signal thus obtained is amplified to a predetermined level in circuit (2I) and supplied to the seven circuits α. The zero-phase current signal input from the circuit (16) in the circuit (Ial) is discriminated by the reference phase signal input from the circuit (21), and when the phase is in the direction of the white line ground fault, a positive voltage output is output. When the phase is in the direction of the other line ground fault, a negative voltage output is output.The positive output is 9
Time-limited setting for ground fault protection cooperation is performed in circuit (23) via circuit (22), and the signal is supplied to two circuits (2 (1) and (27) to 2 circuits C; !8), and the output contact ( 321f:
Close the circuit. This output contact (3 forces can also be an open circuit contact. On the other hand, the circuit (a part of the circuit is connected to the signal through 2 forces)
An operating indicator light (3
3) and an electromagnetic-mechanical display type operating indicator light (34) that continues to display even if the ground fault is removed, and these display devices □□□)+ (34) are operated.

(l15) is a return switch for the indicator light (34). The negative output is supplied to the circuit (c26) via the circuit (25) and c26). In this circuit c24), when a ground fault direction relay device is installed on an actual power distribution line (fc), the ground fault circuit is selectively detected and the moment the circuit is opened, a reduced amplitude oscillation wave of a zero-phase component is generated. To prevent a dual ground fault directional relay from malfunctioning or unnecessary operation.

The above circuit configuration is designed as a plug-in unit that is easy to install and remove, and is designed to be inserted into a storage box that can accommodate 5 circuits at the same time. , f2 are connected to each other to form a ground fault direction relay @.

As described above, the present invention generates a reference phase by synthesizing the output signals of each zero-sequence current transformer without using a zero-sequence voltage detector, and thereby distinguishes the phase of the zero-sequence current. Output only in the direction of the connection. That is, since the zero-sequence voltage signal is also obtained from the zero-sequence current via the zero-sequence current transformer, there is no connection to the high-voltage charging section, and therefore the construction is easy and the construction cost is low. In particular, if the ground fault directional relay of the present invention is combined with a split type zero-phase current transformer, installation of a selective ground fault protection device for existing high-voltage power lines or special high-voltage power lines will be possible.

It is also possible to do this very easily without causing a power outage to the power distribution lines.

[Brief explanation of the drawing]

Fig. 1 is a single line diagram of a 6-phase line in which a conventional ground-fault relay is installed, Figure 2 is a single-line connection diagram of a 6-phase line in which a ground-fault relay according to the present invention is installed, and Fig. FIG. 4 is an equivalent circuit diagram when a complete ground fault occurs in one line; FIG. 4 is a vector diagram of the output current flowing through all the lines in FIG. 6; FIG. It is a block diagram showing (3)...High voltage distribution system, ZCT...Zero phase current transformer, DGR...Ground fault direction relay, (5)...
Sensitivity current setting circuit, (6)...amplitude limit amplification circuit, (
7)...Phase discrimination circuit.

Claims (3)

[Claims] (1) In distribution lines with six or more circuits, the output signals of the zero-phase current transformers installed on each distribution line are combined to generate a reference phase signal for determining the direction of a ground fault, and this reference phase signal is used to A ground fault protection relay method characterized by determining the ground fault direction of zero-sequence current. (2) An input circuit that generates a reference phase signal for ground fault direction determination by combining the phases of the output currents of the zero-phase current transformers installed on each of the six or more distribution lines; Connect to a phase discrimination circuit that inputs the output signal of each zero-phase current transformer and the output signal of the above input circuit, discriminates the phase in the white line ground fault direction and the phase in the other line ground fault direction, and outputs a signal separately. A ground fault protection relay consisting of: (3) The earth fault protection relay according to claim 2, wherein the zero-phase current transformer is a split-type zero-phase current transformer.