JPH03135321A - Circuit breaker - Google Patents

Abstract

PURPOSE:To enable short circuit protecting working to be performed, and miniaturize a device, and lower a cost by setting a means for determining the level of grounding current from the output of current transformers for respective phases, in the circuit breaker of a multi-phase AC electric-circuit. CONSTITUTION:In a mold case, a detection controlling circuit 11, an excess current trip 7, and a short circuit trip 8 are arranged. The input of the secondary side output of current transformers 10a, 10b, 10c, to a micro-computer 20 via a current detecting circuit 12 and phase detecting means 13a, 13b, 13c, is provided. From the micro-computer 20, excess current trip command is generated when a load current value comes to a level equal to or more than a specified level, and the excess current trip 7 is driven. Besides, arithmetic is performed on the vector sum of respective-phase load current, and the level of grounding current is determined. When its level exceeds a specified value, then trip command is generated, and a thyristor 16 is turned ON, and the short circuit trip 8 is driven.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a circuit breaker that performs a tripping operation not only due to an overload current but also due to a ground fault current.

(Prior art) When adding a tripping function based on earth leakage current to a circuit breaker that performs a tripping operation based on overload current, in the past, a circuit breaker was used to detect a minute ground fault current in an AC line. A zero-phase current transformer is interposed, and an earth leakage detection circuit is provided which drives a tripping device by turning on a thyristor, for example, with an output obtained by amplifying the secondary output of this zero-phase current transformer, and the above-mentioned tripping An earth leakage tripping operation is performed in which the main circuit contacts are opened in response to the drive of the device.

(Problem to be solved by the invention) However, in the above conventional configuration, a zero-phase current transformer and an earth leakage detection circuit are required separately, and a power supply exclusively for the earth leakage detection circuit is also required separately, which reduces the overall size. There were problems in that it led to increased formalism and increased costs.

The present invention has been made in view of the above circumstances, and its purpose is to perform earth leakage protection operation using a current transformer and signal processing means provided for overcurrent protection operation. It is an object of the present invention to provide a circuit breaker which is effective in reducing the overall size and cost.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a current transformer for each phase that detects the load current flowing in a multiphase AC circuit, and two of these current transformers. A current detection means that outputs a detection signal with a voltage level corresponding to the load current based on the next output, and a tripping operation that opens the main circuit contact when the load current value indicated by the detection signal exceeds a predetermined value. In a circuit breaker equipped with a signal processing means for executing ?, each member's ? J. A phase detecting means for detecting the phase of the current is provided, and the signal processing means is configured to detect each member's load based on the phase of each member's load current detected by the phase detecting means and the detection signal from the current detecting means. The current vector sum is calculated, the level of the ground fault current is determined based on the result of the calculation, and when the level exceeds a predetermined value, the tripping operation is executed.

(Function) When a load current flows in a polyphase AC circuit, an output voltage at a level proportional to the load current is obtained from the secondary side of each phase current transformer, and an output voltage proportional to the load current is obtained from the current detection means. A detection signal of the detected voltage level is output. At this time, when the load current becomes excessive and the load current value indicated by the detection signal exceeds a predetermined value, the signal processing means executes a tripping operation to open the main circuit contact, thereby providing overcurrent protection. An action is taken.

Further, the phase detection means detects the phase of each member charge current based on the secondary side output of the current transformer for each phase,
The signal processing means calculates a vector sum of each member charge current based on the detection phase and the detection signal from the current detection means.

At this time, the vector sum is zero if the polyphase AC circuit is in a healthy state, but when a ground fault current flows, it takes a value corresponding to the magnitude of the ground fault current.

When a ground fault current flows in this way, the signal processing means executes the tripping operation when the level of the vector sum of the member load currents calculated as described above exceeds a predetermined value, This performs the earth leakage protection operation.

In other words, the i-type protection operation can be performed using the current transformer, signal processing means, etc. provided for the overcurrent protection operation.

(Example) In Fig. 2 showing the cross-sectional structure of a three-phase circuit breaker,
The molded case 1 consists of a base 1a and a cover 1b, and power supply side terminals 2a for each phase are provided on both sides of the base 1a.
l 2 b + 2 C and load side terminals 3a, 3
b, 3c are arranged. Power supply side terminals 2a, 2b, 2
Fixed contacts 4a and 4b are shown in c.

4c, and main circuit contacts Tu, Tv, T together with fixed contacts 4a, 4b, 4c are provided in the molded case 1.
Movable contacts 5a, 5b, 5 forming w (see Figure 1)
c is rotatably supported.

Movable contacts 5 a + 5 b, 5 c are attached to the cover 1 b
It is rotated via a well-known toggle link mechanism 6a in accordance with the operation of the handle 6 protruding from the handle 6, and can be held in the on position and the off position according to the rotation. Further, the toggle link mechanism 6a has movable contacts 5a, 5.
In each case, when the overcurrent tripping device 7 and the earth leakage tripping device 8 arranged in the molded case 1 are driven with the movable contacts 5 and 5c held in the on position, the movable contacts 5
a, 5b.

Move 5C to the trip position and connect the main circuit contact Tu.

A tripping operation is performed to open Tv and Tw.

the movable contacts 5a, 5b, 5c and the load side terminal 3a,
Between each of 3b and 3c is a main circuit conductor 9g which is a multiphase AC circuit.
, 9b, 9c (see Fig. 1), and inside the molded case 1 there are main circuit conductors 9a, 9b, 9c, respectively.
Current transformer 1 for detecting each member's charge current with 9c as the primary conductor
0a, 10b.

10c is provided.

The overcurrent tripping device 7 and the earth leakage tripping device 8 are:
Each of them includes an electromagnetic solenoid, and is driven by a detection control circuit 11 disposed inside the molded case 1.

FIG. 1 shows the entire electrical configuration including the detection control circuit 11, which will be explained below.

That is, as is clear from the above description, the power supply side terminals 2a, 2b, 2c and the load side terminal 3a.

Between each of 3b and 3c are main circuit contacts Tu and Tv.

Main circuit conductors 9a, 9b, 9c are connected via Tw,
Each main circuit conductor 9a, 9b, 9c has a current transformer 10a, 10
b, 10c are provided. Current transformers 10a, 10b,
On the secondary side of 10c, there is a current detection circuit 12 as a current detection means.
is connected. This current detection circuit 12 includes a full-wave rectifier circuit and the like, and includes current transformers 10a and 1.
Based on the secondary side outputs of 0b and 10c, a voltage signal for each phase having a voltage level corresponding to each member's charge current value is output as a detection signal Sd.

Further, on the secondary side of the current transformers 10a, 10b, 10c, phase detection means 1 outputs phase signals Su, Sv, Sw indicating the phase of each member charge current based on the secondary side output.
3a, 13b, and 13c are provided.

The power supply circuit 14 connected to be supplied with power from the current detection circuit 12 is configured to provide a DC output of a constant voltage between the power supply line VDD and the common line COM having a ground potential in an operating state.

The overcurrent tripping device 7 is energized from the current detection circuit 12 via the thyristor 15, and the earth leakage tripping device 8
is configured to be energized from the current detection circuit 12 via the thyristor 16. An overcurrent trip circuit 17 and an earth leakage trip circuit 18 are connected to each gate of the thyristors 15 and 16, respectively.

The A-D conversion circuit 19 provided to be supplied with power from the power supply line VDD converts the detection signal Sd from the current detection circuit 12 into a digital value detection signal S'd and outputs it. . A microcomputer 20 serving as a signal processing means also provided to be supplied with power from the power supply circuit 14 receives a detection signal S'd from the A-D conversion circuit 19.
and phase signals Su from the phase detection means 13a, 13b, and 13c.

The configuration is such that the following control is performed based on Sv and Sw.

That is, when the load current value indicated by the detection signal S'd exceeds a predetermined upper limit level, the microcomputer 20 outputs the tripping command signal So from the output port Po, and thereby the overcurrent tripping circuit 17 thyristor 15 is turned on.

Further, the microcomputer 20 has phase signals Su, S
Based on the phase of each member load current indicated by v and Sw and the load current indicated by the detection signal S'd, the vector sum of each member load current is calculated to determine the level of the ground fault current, and the level is determined. When the predetermined value is exceeded, a tripping command signal S1 is output from the output horn boat P1, thereby turning on the thyristor 16 through the earth leakage tripping circuit 18.

In short, according to the above configuration, the main circuit conductor 9a.

When the load current flowing through 9b and 9c becomes excessive and exceeds a predetermined value, the microcomputer 20 detects this based on the detection signal Sd and activates the thyristor 15.
is turned on to drive the overcurrent tripping device 7. As a result, the main circuit contact Tu.

A tripping operation is performed in which Tv and Tw are forcibly opened, thereby performing an overcurrent protection operation.

The microcomputer 20 also includes a phase detection means 13.
a, 13b, 13c are current transformers for each phase 10a, 10b, 1
The vector sum of each member's charge current is calculated based on the phase of each member's charge current detected based on the secondary side output of 0c and the detection signal S'd. At this time, the above vector sum is zero if each member's charge current is in a healthy state, but
When a ground fault current flows, the value corresponds to the magnitude of the ground fault current. When a ground fault current flows in this way, the microcomputer 20 turns on the thyristor 16 and drives the earth leakage tripping device 8 based on the calculation result as described above. As a result, the main circuit contacts Tu, Tv, T
A tripping operation is performed in which w is forcibly opened, thereby performing a BTh protection operation.

Therefore, according to the present embodiment described above, the current transformers 10a, 10b are provided for overcurrent protection operation.

10c and the microcomputer 20, etc., it is not necessary to separately provide a zero-phase current transformer and an earth leakage detection circuit as in the past, and a dedicated earth leakage detection circuit can be used. There is no need to provide a separate power supply, and as a result, the molded case 1 can be made smaller and costs can be reduced.

[Effects of the Invention] According to the present invention, as is clear from the above description, phase detection detects the phase of each member load current based on the secondary output of the current transformer for each phase for overcurrent protection operation. The signal processing means provided for overcurrent protection operation is configured to detect each member's charge current based on the phase of each member's charge current detected by the phase detecting means and the detection signal from the current detecting means. In addition to calculating the vector sum of The current transformer, signal processing means, etc. provided for overcurrent protection operation can also be used for earth leakage protection operation, which has the excellent effect of reducing the overall size and cost. It is something.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a schematic circuit configuration diagram, and FIG. 2 is a longitudinal sectional side view. In the figure, Tu, Tv, and Tw are main circuit contacts, 7 is an overcurrent tripping device, 8 is an earth leakage tripping device, and 9a. 9b, 9c are main circuit conductors (polyphase AC circuit), 10a, 1
0b and 10c are current transformers, 11 is a detection control circuit, 12 is a current detection circuit (current detection means), 13a, 13b, 13C
14 represents a phase detection means, 14 represents an 'rIS'R circuit, and 20 represents a microcomputer (signal processing means).

Claims (1)

[Claims] 1. A current transformer for each phase that detects the load current flowing in a multiphase AC line, and a current detection means that outputs a voltage level detection signal according to the load current based on the secondary output of these current transformers. and signal processing means for performing a tripping operation of opening a main circuit contact when the load current value indicated by the detection signal exceeds a predetermined value, the current transformation for each phase The signal processing means detects the phase of each phase load current detected by the phase detection means and the current detection means. The vector sum of each phase load current is calculated based on the detection signal from the means, and the level of the ground fault current is determined based on the calculation result, and when the level exceeds a predetermined value, the tripping operation is performed. A circuit breaker configured to perform.