JPH08279331A - Earth leakage breaker with excessive voltage detecting function - Google Patents

Abstract

PURPOSE: To prevent the damage of a load equipment in the case of repeating reclosing and cutting of an earth leakage breaker under the excessive voltage condition after cutting the excessive voltage. CONSTITUTION: Within a constant extension time from the time when the generation of excessive voltage in a load circuit is detected by an excessive voltage detecting circuit A till an excessive voltage operating circuit B drives a switching element 13 of a trip coil 14 so as to cut the circuit, a capacitor 31 is charged, after cut of the circuit and when the earth leakage breaker is reclosed within the discharging time of the capacitor 31, the switching element 13 is instantaneously driven through an AND circuit. When the earth leakage breaker is reclosed after cutting the excessive voltage, the circuit can be instantaneously cut without waiting the extension time, and the excessive voltage stress to be applied to a load equipment can be thereby reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an earth leakage circuit breaker with an overvoltage detecting function, which has a function of detecting an overvoltage state of a load circuit and shutting off the circuit to protect load equipment from damage due to overvoltage. The present invention relates to the configuration of an additional circuit for enhancing the protection function of equipment.

[0002]

2. Description of the Related Art Overvoltage in a power distribution system is often caused by an unbalanced load impedance when a neutral wire of a single-phase three-wire system is broken. 3A and 3B show the appearance of an earth leakage circuit breaker with an overvoltage protection function. FIG. 3A is a front view and FIG. 3B is a side view. In FIG. 3, a power supply side terminal 1 and a load side terminal 2 are arranged in front of and behind the case, and an opening / closing handle 3, an earth leakage display button 4, a test button 5 and the like are arranged on the front surface. A lead wire 6 for detecting an overvoltage is led out from the load side of the case, and the lead wire 6 is connected to a neutral wire electric path connected to the load side terminal 2.

FIG. 4 shows the internal circuit of the earth leakage breaker of FIG. In the figure, when a leakage current flows through the primary side of the zero-phase current transformer 10 (the main circuit conductor of the leakage breaker), an output voltage is generated on the secondary side. When the level of the output voltage becomes equal to or higher than the set value, the leakage detection circuit 11 composed of the IC has the resistance 12
The switching element (SCR) 13 is driven via.
As a result, the trip lip coil 14 is excited, the open / close mechanism of the earth leakage breaker (not shown) is driven, and the load circuit is cut off. The power of each of the above parts is supplied from the rectifier circuit 15 which is a diode bridge connected between the R phase and the T phase of the load side electric circuit.

On the other hand, the illustrated circuit is provided with an overvoltage detection circuit A and an overvoltage operation circuit B surrounded by a chain line.
In the overvoltage detection circuit A, either the voltage between N-R or N-T is in the overvoltage state with reference to the N phase of the load side neutral line electric circuit. In this case, the normal voltage is 100V (variable range 80 to 120V). It is set to operate at 125 to 135V. FIG. 5 shows the relationship between the normal and overvoltage states of the voltage V ₁₆ appearing in the resistor 16 of FIG. 4 and the operating levels V ₁₇ and V ₁₈ of the constant voltage diodes 17 and 18. The constant voltage diode 17 is set to a value at which a current flows at a normal voltage as shown in the figure, and the transistor 19 is always in the ON state at the normal voltage, so that the drive signal is not output to the switching element 13.

On the other hand, since the constant voltage diode 18 is set to a value at which a current flows due to an overvoltage, when the voltage between N and R or between N and T becomes an overvoltage state, the transistor 20 is turned on. Then, the transistor 19 is turned off. In this state, the resistor 21
The voltage divided by 22 and 22 is applied to drive the switching element 13. Here, the resistors 21 and 22, the capacitor 23, the diode 24, and the constant voltage diode 2
In the overvoltage operation circuit B composed of 5
When the FF state is entered, a certain time delay time is secured so that the switching element 13 is not driven instantaneously. The value of the delay time is determined by the constants of the resistors 21 and 22 and the capacitor 23, and is set to about 500 ms in this case. The reason for ensuring the delay time is that there is a possibility that a momentary overvoltage will occur on a daily basis in the power distribution system, such as when the switch is turned on, which does not adversely affect the load equipment. This is to prevent it from operating.

[0006]

The conventional earth leakage breaker has the following problems.
When the circuit voltage exceeds 135V, it is set to shut off at a constant delay time (about 500ms above). Therefore, if the earth leakage breaker operates due to overvoltage, it is not a problem if the user finds out the cause of the overvoltage, confirms that it is normal, and then recloses the earth leakage breaker, but the cause is the earth leakage breaker. If it is erroneously recognized and repeated re-closing and interruption as it is, overvoltage stress is repeatedly applied to the load device for each 500 ms delay time, which may lead to deterioration or damage of the device. Therefore, in the present invention, after the earth leakage breaker is shut off due to overvoltage,
It is an object of the present invention to provide an earth leakage breaker with an overvoltage protection function, which can minimize overvoltage stress on a load device even when it is reclosed in an overvoltage state.

[0007]

In order to achieve the above object, the present invention drives a switching element of a trip coil to shut off the load circuit while the load circuit leaks, while the voltage of the load circuit is cut off. Constantly monitor the level,
An overvoltage detection circuit that outputs an overvoltage signal when the voltage level is determined to be an overvoltage state, and an overvoltage operation circuit that drives the switching element after a certain time delay has elapsed when the overvoltage signal is output are provided. In the earth leakage breaker with over voltage detection function, when the over voltage signal is output from the over voltage detection circuit, the elapsed time timer circuit that sets the constant discharge time by charging the capacitor within the time delay time of the over voltage operation circuit, and the discharge time An instantaneous operation circuit for instantaneously driving the switching element of the trip coil when the overvoltage signal is output again is additionally provided.

[0008]

When the earth leakage breaker operates in overvoltage, a certain delay time is secured. Therefore, an elapsed time timer circuit that charges the capacitor within this time delay time and sets a constant discharge time is provided, and if the overvoltage signal is output again within the discharge time, the switching element of the trip coil is switched by the instantaneous operation circuit. Drive instantly. As a result, when the power is turned on again in the overvoltage state after the overvoltage operation, the circuit is instantaneously cut off without waiting for the delay time, and the overvoltage stress on the load device is minimized.

[0009]

1 is an internal circuit diagram of an earth leakage breaker according to an embodiment of the present invention, and FIG. 2 is a time chart for explaining its overvoltage operation. The conventional example of FIG. 4 is a circuit of FIG. 1, the elapsed time timer circuit C and the instantaneous operation circuit D is shown V _C -V _S
Has been added in between. In FIG. 1, an overvoltage operation circuit B
Output voltage (c) is divided by the constant voltage diode 26 and the resistor 27 of the elapsed time timer circuit C, and the voltage of the resistor 27 (d)
Are input to the buffer 28. Here, the operation level of the buffer 28 is set to about 80% of the voltage level when the switching element of the overvoltage operation circuit B is driven. The output voltage (e) of the buffer 28 is applied to the capacitor 31 via the diode 29 and the resistor 30 to charge it. The charging time constant at this time is determined by the resistor 30 and the capacitor 31, and is set within 100 ms.

The charging voltage (f) of the capacitor 31 is the resistance 32
Is input to the AND circuit 33 of the instantaneous operation circuit D via. The discharge time constant at this time is the resistance 32 and the capacitor 31.
It is determined by and is set to several tens of seconds. On the other hand, a resistor 34 is newly inserted in the emitter circuit of the transistor 20, its voltage (a) is input to the buffer 35, and the output voltage (b) of the buffer 35 is input to the AND circuit 33. Then, the switching element 13 is driven by the output voltage (g) of the AND circuit 33.

In FIG. 2, the output voltage (a) is applied to the buffer 35 in the overvoltage state (transistor 20 is ON),
The output voltage (b) is generated. Further, when the output voltage (c) of the overvoltage operation circuit B gradually rises and exceeds about 80% of the level when the switching element is driven, a current flows through the constant voltage diode 26 and the voltage (d) of the resistor 27 is added to the buffer 28. ,
The output voltage (e) charges the capacitor 31 and the voltage
(F) occurs. This voltage (f) is the output voltage of the buffer 35
(B) When applied to the AND circuit 33 at the same time, its output voltage
(G) is given to the switching element 13 as a drive signal at the times t ₁ and t ₂ . On the other hand, the drive signal of the overvoltage operation circuit B is given to the switching element 13 at time t ₃ when the output voltage (C) of the overvoltage operation circuit B reaches 100% of the level when the switching element is driven. In that case, the output voltage (g) at the time point t ₁ has a narrow pulse width and does not drive the switching element 13. The output voltage (g) at the time point t ₂ and the drive signal of the overvoltage operation circuit B at the time point t ₃ drive the switching element 13 almost at the same time, whereby the circuit is cut off.

After that, when the earth leakage breaker is turned on again at the time t ₄ within the discharging time of the capacitor 31, the overvoltage condition is maintained,
When the voltage (f) is input, the output voltage (b) of the buffer 35 is applied to the AND circuit 33, and the switching element 13 is instantaneously driven and cut off again. This reclosing-immediate-interruption is repeated any number of times within the discharge time of the capacitor 31. Therefore, even if the power supply is repeatedly turned on again without knowing the cause of the overvoltage, the overvoltage stress on the load device can be minimized because the power is cut off instantly.

[0013]

According to the present invention, when the earth leakage breaker detects an overvoltage and performs an interruption operation, and then is turned on again in an overvoltage state, a delay time is provided if it is within the discharge time of the elapsed time timer circuit. Since the circuit is instantly cut off without waiting, the damage to the load equipment can be reduced, and the safety of the earth leakage breaker with the overvoltage detection function can be further enhanced.

[Brief description of drawings]

FIG. 1 is an internal circuit diagram of an earth leakage breaker showing an embodiment of the present invention.

FIG. 2 is a time chart showing the voltage level of each part of FIG.

FIG. 3 is a perspective view showing an external appearance of an earth leakage breaker with an overvoltage detection function.

FIG. 4 is an internal circuit diagram of a conventional earth leakage breaker.

FIG. 5 is a diagram showing voltage levels in a normal state and an overvoltage state between N and R or N and T in FIG.

[Explanation of symbols]

 10 Zero Phase Current Transformer 11 Leakage Detection Circuit 14 Trip Coil 28 Buffer 35 Buffer A Overvoltage Detection Circuit B Overvoltage Operation Circuit C Elapsed Time Timer Circuit D Instantaneous Operation Circuit

Claims (1)

[Claims] 1. When a leakage current occurs in a load circuit, the switching element of a trip coil is driven to shut off the load circuit, while the voltage level of the load circuit is constantly monitored and it is determined that this voltage level is an overvoltage state. In the overvoltage detection circuit with an overvoltage detection circuit that outputs an overvoltage signal, and an overvoltage detection circuit having an overvoltage operation circuit that drives the switching element after a certain time delay has elapsed when the overvoltage signal is output, When an overvoltage signal is output from the overvoltage detection circuit, an elapsed time timer circuit that sets a constant discharge time by charging the capacitor within the time delay time of the overvoltage operation circuit, and if the overvoltage signal is output again within the discharge time Leakage with overvoltage detection function, characterized by adding an instantaneous operation circuit that instantaneously drives the switching element of the trip coil Circuit breaker.