JPH04372519A - Breaker - Google Patents

Abstract

PURPOSE:To provide a breaker which can prevent the malfunction by unbalance property without doing complicated magnetic screening or the like to a zero- phase current transformer. CONSTITUTION:A breaker 3A is equipped with a zero-phase current transformer 6, which detects the zero-phase current flowing to the electric path 5 connected to an AC power source 1 through a switch mechanism 4, a leak detecting circuit 7, which outputs a leak trip signal b according to leak trip property, a current detector 8, which is connected to the electric path 5, an overcurrent detecting circuit 9, which outputs an overcurrent trip signal (a) according to overcurrent trip property, and a trip means, which is composed of said switch mechanism 4, a thyristor 10, and a solenoid 11 for tripping. The leak trip signal (b)of the leak detecting circuit 7 is sent to the overcurrent detecting circuit 9, and when the current detected with the current detector 8 is below the set value, it is output to the thyristor 10 and the electric path 5 is broken, but when the current detected by the current detector 8 is over the set value, it is not output and the electric path 5 is not broken.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit breaker having earth leakage tripping characteristics and overcurrent tripping characteristics.

0002

[Prior Art] Conventionally, zero-phase current transformers for earth leakage detection in earth leakage circuit breakers have residual current characteristics, and when a large current flows during startup of equipment connected to the load side, the magnetic field causes earth leakage. There was a problem in that the earth leakage circuit breaker malfunctioned due to the output even though it was not. This is called the unbalanced characteristic,
It is necessary to take measures such as magnetically shielding the zero-phase current transformer for leakage detection, and for example, a magnetic shielding structure for a zero-phase current transformer is described in Japanese Utility Model Publication No. 2-46022. This actual fairness 2-
According to Japanese Patent No. 46022, a plurality of magnetic shielding plates are provided on both sides of a zero-phase current transformer to improve the balance characteristics of the zero-phase current transformer.

0003

[Problem to be Solved by the Invention] However, as in the above-mentioned conventional method, providing a magnetic shield to a zero-phase current transformer in order to prevent malfunction of an earth leakage circuit breaker due to unbalanced characteristics would result in a complicated structure. I have no choice but to. The purpose of this invention is to
It is an object of the present invention to provide a circuit breaker capable of preventing malfunctions due to unbalanced characteristics without requiring complicated magnetic shielding of a zero-phase current transformer.

0004

[Means for Solving the Problems] The circuit breaker of the present invention includes a current detection section, an overcurrent detection circuit, a zero-phase current transformer, an earth leakage detection circuit, and a tripping means. The current detection section detects the current flowing in the electrical circuit between the AC power source and the load, and the overcurrent detection circuit has overcurrent tripping characteristics to cut off the electrical circuit based on the detected current of the current detection section. It is designed to output an overcurrent trip signal in response to the The zero-phase current transformer is designed to detect the zero-sequence current flowing in the electrical circuit, and the earth leakage detection circuit detects earth leakage according to the earth leakage tripping characteristics to interrupt the electrical circuit based on the detected current of the zero-phase current transformer. It is designed to output a trip signal. The tripping means is adapted to cut off the electric circuit in response to an overcurrent tripping signal from the overcurrent detection circuit or an earth leakage tripping signal from the earth leakage detection circuit. Furthermore, when the current detection section detects a current exceeding a set value, the tripping signal of the earth leakage detection circuit is not input to the tripping means.

[0005]

[Operation] According to the configuration of the present invention, the earth leakage detection circuit outputs an earth leakage tripping signal in accordance with the earth leakage tripping characteristics for breaking the electric circuit based on the detected current of the zero-phase current transformer. When a current exceeding the set value is detected in the circuit, the tripping signal of the earth leakage detection circuit is not input to the tripping means. Malfunctions due to unbalanced characteristics can be prevented.

[0006]

[Embodiments] [First Embodiment] A first embodiment of the present invention will be described based on the drawings. FIG. 1 is a circuit diagram of a circuit breaker according to a first embodiment of the present invention. In FIG. 1, 1 is an AC power supply, 2 is a load supplied by the AC power supply 1, and 3A
is a circuit breaker connected between AC power supply 1 and load 2.

This circuit breaker 3A includes a zero-phase current transformer 6 for detecting a zero-phase current flowing in a circuit 5 consisting of three-phase conductors 5a, 5b, and 5c connected to an AC power source 1 via a switching mechanism 4;
An earth leakage detection circuit 7 that outputs an earth leakage tripping signal b according to the earth leakage tripping characteristic for interrupting the electric line based on the detected current of the zero-phase current transformer 6, and each phase conductor 5a, 5b, 5 of the electric line 5.
A current detection unit 8 consisting of current transformers 8a, 8b, and 8c connected to the current detection unit 8 and an overcurrent trip signal a according to the overcurrent trip characteristic for interrupting the electric circuit based on the detected current of the current detection unit 8 The overcurrent detection circuit 9 outputs an overcurrent, and a tripping means includes an opening/closing mechanism section 4, a thyristor 10, and a tripping solenoid 11. In addition, 12, 13, 1
8 is a resistor, 14 is a rectifying diode, 15 is a smoothing capacitor, 16 is a test button, 17 is a test winding, and 19 is a surge absorption varistor.

Furthermore, the earth leakage tripping signal b of the earth leakage detection circuit 7 is once sent to the overcurrent detection circuit 9, and if the current detected by the current detection section 8 is less than a set value, the overcurrent detection circuit 9
When it is determined that the current is detected by the current detection section 8, the current is outputted to the thyristor 10, and when it is determined that the current detected by the current detection section 8 exceeds the set value, it is not outputted. The set value here is preferably not an overcurrent that slightly exceeds the rated current, but a current value that exceeds, for example, five times the rated current.

The operation of the circuit breaker 3A constructed as described above will be further explained below with reference to FIG. In addition, FIG. 3 is an operating characteristic curve of the circuit breaker 3A, where A shows the overcurrent tripping characteristic and B shows the earth leakage tripping characteristic. In this circuit breaker 3A, when the overcurrent detection circuit 9 determines that the current detected by the current detection section 8 is an overcurrent, the long time period LTD and short time period of the overcurrent tripping characteristics A shown in FIG. Depending on the characteristics of the time-limited region STD and the instantaneous region INST, an overcurrent trip signal a is output after a predetermined time to turn on the thyristor 10, and the trip solenoid 11 is energized to open the opening/closing mechanism section 4. As a result, the electric circuit 5 is cut off.

Furthermore, when the leakage detection circuit 7 determines that the detected current of the zero-phase current transformer 6 is a leakage current, the circuit shown in FIG.
An earth leakage tripping signal b is output to the overcurrent detection circuit 9 according to the earth leakage tripping characteristic B shown in FIG. In the overcurrent detection circuit 9,
Only when the current detected by the current detector 8 is less than the set value, the earth leakage tripping signal b from the earth leakage detection circuit 7 is output to the thyristor 10, and the electric circuit 5 is cut off.

As described above, according to this embodiment, the electric circuit 5
By not outputting the earth leakage tripping signal b to the tripping means (thyristor 10) when the current flowing through the current transformer exceeds the set value, malfunction due to the unbalanced characteristics of the zero-phase current transformer 6 can be prevented. It can be prevented. Note that the current exceeding the set value is, as shown in Figure 3, a current in the earth leakage non-operation area C, and is not an overcurrent that slightly exceeds the rated current, but an overcurrent that exceeds the rated current for a short period of time, for example, exceeding 5 times the rated current. ST
It is desirable to set the current to D.

[Second Embodiment] A second embodiment of the present invention will be explained based on the drawings. FIG. 2 is a circuit diagram of a circuit breaker according to a second embodiment of the present invention. In Figure 2, 3B
1 is a circuit breaker connected between an AC power supply 1 and a load 2, and parts corresponding to those in FIG. 1 are given the same reference numerals. Hereinafter, mainly the differences from the first embodiment will be explained.

In this circuit breaker 3B, the earth leakage tripping signal b from the earth leakage detection circuit 7 is sent via the switch 20 to the thyristor 10 as the tripping means. The switch 20 is turned on when the overcurrent detection circuit 9 determines that the current detected by the current detection section 8 is below the set value, and turns on when the current detected by the current detection section 8 exceeds the set value. It is turned off when it is determined (that is, by the earth leakage inoperation signal c).

The operating characteristics of this circuit breaker 3B are similar to those of the first embodiment, and are shown in FIG. In this circuit breaker 3B, in the overcurrent detection circuit 9, the current detection section 8
When it is determined that the detected current is an overcurrent, an overcurrent tripping signal a is output after a predetermined time according to the overcurrent tripping characteristic A shown in FIG. 3, and the tripping means (10, 11 ,4)
As in the first embodiment, the electric circuit 5 is cut off by this.

Furthermore, when the leakage detection circuit 7 determines that the detected current of the zero-phase current transformer 6 is a leakage current, the circuit shown in FIG.
An earth leakage tripping signal b is output according to the earth leakage tripping characteristic B shown in FIG. If the switch 20 is on at this time,
The electric circuit 5 is cut off by the tripping means (10, 11, 4), but if the switch 20 is in the OFF state, the tripping means (10, 11, 4)
10, 11, 4) do not operate and the electric circuit 5 is not cut off. The switch 20 receives the earth leakage inoperation signal c from the overcurrent detection circuit 9.
This earth leakage non-operation signal c is turned off when the current detected by the current detection unit 8 is in the earth leakage non-operation area C shown in FIG. , for example, a short time range S exceeding 5 times the rated current
If it is TD, it is output from the overcurrent detection circuit 9.

As described above, according to this embodiment, the current flowing through the electric line 5 exceeds the set value (
Leakage non-operation area C) If current, switch 20
By turning off the earth leakage tripping signal b and not inputting the earth leakage tripping signal b to the tripping means (thyristor 10), it is possible to prevent malfunction due to unbalanced characteristics of the zero-phase current transformer 6.

[0017]

[Effects of the Invention] The circuit breaker of the present invention does not require complicated magnetic shielding in the zero-phase current transformer, and when the current detection section detects a current exceeding a set value, the circuit breaker issues a tripping signal for the earth leakage detection circuit. Since no input is made to the tripping means, it is possible to prevent malfunction due to unbalanced characteristics of the zero-phase current transformer caused by a current exceeding a set value flowing through the electric circuit.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a circuit breaker according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a circuit breaker according to a second embodiment of the invention.

FIG. 3 is an operational characteristic diagram of the circuit breaker of the first and second embodiments.

[Explanation of symbols]

1 AC power supply 2 Load 4 Switching mechanism section (tripping means) 5 Electrical circuit 6 Zero-phase current transformer 7 Earth leakage detection circuit 8 Current detection section 9 Overcurrent detection circuit 10 Thyristor (tripping means) 11 Tripping solenoid (tripping means) Means) a Overcurrent trip signal b Earth leakage trip signal

Claims (1)

[Claims] 1. A current detection unit that detects a current flowing in an electric path between an AC power supply and a load, and an overcurrent tripping characteristic for interrupting the electric path based on the detected current of the current detection unit. an overcurrent detection circuit that outputs an overcurrent tripping signal; a zero-sequence current transformer that detects a zero-sequence current flowing in the electrical circuit; and a circuit that interrupts the electrical circuit based on the detected current of the zero-sequence current transformer. an earth leakage detection circuit that outputs an earth leakage tripping signal according to the earth leakage tripping characteristic; and a tripping means that cuts off the electric circuit by an overcurrent tripping signal of the overcurrent detection circuit or an earth leakage tripping signal of the earth leakage detection circuit. A circuit breaker, characterized in that when the current detecting section detects a current exceeding a set value, a tripping signal of the earth leakage detection circuit is not input to the tripping means.