JPS61248331A - Fuse out detector - 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 [Field of Industrial Application] The present invention relates to a blown fuse detection device, particularly to a blown fuse detection device on the secondary side of a voltage transformer of a power transmission line drawn out from a busbar system.

[Conventional technology]

FIG. 2 is a block diagram showing a protective relay device for a busbar system to which a conventional fuse blown detection device is applied. In FIG.
CTB and CTC are current transformers installed in each phase of the transmission line A, B, and C, and FAsFB+FC is the primary side full power transmission @A, B.
, a voltage transformer PTA connected to each phase of C, p'
Secondary side detected fuses (hereinafter abbreviated as fuses) of rB and p'rc, and CB are power transmission lines A and B.

This is the breaker installed at C.

1 is a fuse blown detection device, which detects three-phase voltage ■6. ■b.

A synthetic transformer TA p TB + TC for deriving the zero-sequence voltage Vo by inputting Vct, and a zero-sequence voltage for detecting whether the zero-sequence voltage V The detection element OVG and the zero-sequence current 1. are set to a predetermined value (
For example, the output of the zero-sequence current detection element OCG, which detects whether the current is higher than 10 times the rated current, and the output of the zero-sequence voltage detection element OVG are all positive inputs, and the output of the zero-sequence current detection element OCG is inhibited (inhibit input). INHIBIT) circuit lN-1
It is composed of.

DZ is a protective distance relay for transmission lines A, B, and C.
When a fault occurs in the line, a trip command is output to breaker CB. In addition, with load current flowing through transmission lines A, B, and C, voltage transformer PTA.

Secondary side fuse FArFB of p'r, , p'rc
If at least one of the rFCs melts, it is assumed that a fault has occurred in the power transmission line, and the distance relay DZ responds unnecessarily.
A trip command will be output to the circuit breaker CB.

Therefore, in order to prevent unnecessary response of the distance relay DZ as described above, when the fuse blown detection device 1 is activated, it is connected so as to issue an alarm to the outside and automatically lock the distance relay DZ.

Next, the operation of the fuse blown detection device will be explained.

Fuse to be detected FA h FB * When all FCs are normal, the 13-phase city pressure on the output side of the fuse is Va, b, v
c is balanced at the healthy rated voltage, and the zero-sequence voltage V (
, are zero - for example, two of the voltage transformers PTA, PTB, p'rc
On the next side, when a short-circuit fault occurs in the A-phase and B-phase, the fuse FA + FB is blown, and as a result, a zero-sequence voltage V(, is generated, and the zero-sequence voltage detection element OVG is activated. On the other hand,
Since no ground fault has occurred on grid transmission lines A, B, and C, zero-sequence current is 10, and zero-sequence current detection element OCG
is inactive. Therefore, when the inhibit circuit IN-1 outputs an output indicating that the fuse is blown, it is not the fuse that is blown, but the grid transmission line A.

Even if a one-phase ground fault occurs in B and C, the zero-sequence voltage detection element OVG operates, but at this time, zero-sequence current IO is generated and the zero-sequence current detection element OCG also operates, so inhibit There is no fuse blown detection output from the circuit IN-1.

[Problem that the invention seeks to solve]

Since the conventional fuse blown detection device is configured as shown in -h, one of the fuses FA + FB HFC
If a phase or two phase fuse is blown, zero-sequence w1 voltage Vo is generated and fuse blown is detected, but if all three phase fuses are blown, zero-sequence voltage VO is not generated. Therefore, there was a problem that it could not be detected.

This invention was made in order to solve the above-mentioned problems, and it is a highly sophisticated technology that can reliably detect a fuse blown not only in one phase or two phases but also in the case where all three phases are blown. The purpose is to obtain a sensitive fuse blown detection device.

[Means to solve all problems]

The fuse blown detection device according to the present invention includes an undervoltage detection element that responds to the voltage of at least one phase of the three-phase voltage, an overcurrent detection element that responds to the current of one phase having the same name as the undervoltage detection element, and A logic circuit is provided that detects a blown fuse by logically determining the operating states of the zero-sequence voltage detection element that responds to the phase voltage and the zero-sequence current detection element that responds to the zero-sequence current.

[Effect]

The logic circuit of the fuse blown detection device according to the present invention detects a fuse blown in one phase or two phases under the condition that the zero-sequence current detection element is inoperative and the zero-sequence voltage detection element is operated, and detects the failure of the overcurrent detection element. It detects fuse rupture in all three phases under the conditions of operation and undervoltage detection element operation.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, the same parts as in FIG. 2 are given the same reference numerals, and their explanation will be omitted. 11 is a fuse rupture detection device;
A zero-phase voltage detection element OVG, a zero-phase current detection element OCG, an undervoltage detection element UV connected to one phase of the three phases (phase A in the illustrated example), and an undervoltage detection element of the three phases. The overcurrent detection element OC connected to the same human face as the logic circuit 12
The logic circuit 12 includes a first inhibit circuit lN-1 which takes the output from the zero-sequence voltage detection element OVG as an affirmative input and the output from the zero-sequence current detection element OCG as an inhibition input; A second inhibit circuit IN-2 and a first inhibit circuit IN-1 have an output from the voltage detection element UV as a positive input and an output from the overcurrent detection element OC as an inhibition input.
and an OR circuit OR whose inputs are the output of

In this case, the detection sensitivity of the undervoltage detection element UV is set to about 7 times the rated voltage so as not to react to regular fluctuations in normal voltage, and the detection sensitivity of the overcurrent detection element OC is set to about 7 times the rated voltage so as not to react to regular fluctuations in the normal voltage. Set it to about 1.5 times the rated current so that it does not respond to the current.

Next, the operation of the fuse blown detection device 11 according to the present invention will be explained. Detected fuse FA 1 FB + FC
When is normal, the three-phase voltage Va on the output side of the fuse,
Vb and Vc are balanced at healthy voltages, the zero-phase voltage detector OVG and the undervoltage detection element UV are both inoperative, and the first. Second inhibitor circuit lN-1゜lN-2 and OR
No output of fuse blown detection is generated from the circuit OR.

A phase on the secondary side of voltage transformer p'rA, PTB, PTC.

The operation when the B-phase fuse blows is the same as that of the conventional device; the first inhibit circuit lN-1 outputs an output, and the O
The R circuit OR generates a fuse blown detection output.

Next, when a three-phase short circuit fault occurs at the secondary level of the voltage transformer "A + PTB, p'rc," the fuses FA, FB,
All of the FCs are blown, and the three-phase voltage on the output side of the fuse is va.

Vb and Vc both become zero, and the undervoltage detection element UV operates. On the other hand, since no grid failure has occurred in the power transmissions HA, B, and C, the overcurrent detection element OC is inoperative.

Therefore, an output is generated from the second inhibit circuit IN-2, and an output indicating the fuse blowout is generated from the OR circuit OR.

If a 1-phase ground fault or 2-phase ground fault occurs in grid transmission lines A, B, and C instead of a blown fuse, the zero-phase voltage detection element OVG operates like the conventional device, but Since the phase current detection element OCG also operates, no output is generated from the first inhibit circuit IN-1.

Furthermore, if a three-phase fault occurs in the grid transmission lines A, B, and C, the undervoltage element UV operates, but the overcurrent detection element OC also operates, so the second inhibit circuit lN-2
No output is produced from.

In this embodiment, undervoltage detection element Uv overcurrent detection element O
Since C is installed in the A phase, AB phase short circuit and CA phase short circuit will operate in exactly the same way as the 3 phase short circuit described above, and B
Regarding the C-phase short circuit failure, the undervoltage element Uv does not operate, so no fuse blown detection output is generated in this case as well.

In the above embodiment, the overcurrent detection element OC is used together with the zero-sequence current detection element OCG as a means for detecting the occurrence of a system failure, but the detection sensitivity of the overcurrent detection element OC is as follows. As mentioned above, the current is set to about 1.5 times the rated current. Therefore, in the case of a system in which the fault current of the system is small, there is a risk that a fuse blowout may be unnecessarily detected despite the system failure.

Therefore, as a measure to prevent this false detection, instead of the overcurrent detection element 000, a current change width detection element that responds to sudden changes in fault current is used, and it is set to about 10 times the rated current.
Highly reliable fuse rupture detection system that does not react unnecessarily even when the fault current in the system is small! 2t can be obtained - [Effects of the Invention] As described above, according to the present invention, a blown fuse of one phase or two phases can be detected on the condition that the zero-sequence current detection element is inoperative and the zero-sequence overvoltage detection element is operated. However, on the condition that the undervoltage element that responds to the voltage of one phase of the three-phase voltage on the output side of the fuse operates and the overcurrent detection element or current change range detection element that responds to the current of the same phase does not operate, all three phases Since a logic circuit is provided to detect a blown fuse, it is possible to obtain a highly sensitive fuse rupture detection device that can reliably detect a blown fuse in all three phases in addition to detecting a blown fuse in one or two phases.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a blown fuse detection device according to an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional blown fuse detection device. A, B, C are grid transmission lines, PTA, PTB, PTC are voltage transformers, FAIFBIFC is the fuse to be detected, OVG
is the zero-sequence voltage detection element, OCG is the zero-sequence current detection element, Uv
is an undervoltage detection element, OC is an overcurrent detection element or current change range detection element, and 12 is a logic circuit. In the drawings, the same reference numerals indicate the same or similar parts.

Claims (2)

[Claims] (1) A zero-phase voltage detection element that responds to the zero-phase voltage obtained from the three-phase voltage passed through the three-phase detected fuse connected to the secondary side of the voltage transformer of the grid transmission line; an undervoltage detection element that responds to the voltage of at least one phase; a zero-sequence current detection element that responds to the zero-sequence current obtained from the three-phase current of the grid transmission line; and one phase that has the same name as the undervoltage detection element.
1 under the condition that the overcurrent detection element responds to the phase flow, the zero-sequence current detection element is inoperable, and the zero-sequence voltage detection element is operated.
A fuse blown detection device comprising: a logic circuit that detects fuse blown in one phase or two phases, and detects fuse blown in all three phases under the condition that the overcurrent detection element is inoperable and the undervoltage detection element is operated. (2) The fuse blowout detection device according to claim (1), wherein the overcurrent detection element is replaced with a current change width detection element.