WO2006039836A1

WO2006039836A1 - Arc protective and fireproof circuit for electicr power cable

Info

Publication number: WO2006039836A1
Application number: PCT/CN2004/001159
Authority: WO
Inventors: Jianguo Su
Original assignee: Jianguo Su
Priority date: 2004-10-12
Filing date: 2004-10-12
Publication date: 2006-04-20
Also published as: CN100495846C; CN1868103A

Abstract

An arc protective and fireproof circuit for electric power cable includes a detecting section, a sampling section, a power supplying section, and a breaking secion. The arc protective and fireproof circuit for electric power cable is connected in series with the power cable between the source and the load. Divider resistors R2 and R3 connected in series are provided between the conductive coating of the electric power cable and the ground/neutral line. The electric signal generated on the voltage dividing point between the divider resistor R2 and R3 is rectified and filtered. Then the electric signal is sent to an amplifier and controls a breaking relay J. The on/off state of the electric power cable between the source And the load is controlled by the breaking relay J.

Description

Arc protection and fire protection circuit for power cables

Technical field

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an arc protection and fire protection circuit for a power cable, and more particularly to an arc protection and fire protection circuit for disconnecting a live wire in real time when an arc is generated between a live wire and a metal shield covering the cable.

Background technique

In the art, grounded arc circuit breaker (GFCI) circuits are well known and are commonly used to guard against grounding of the live and/or neutral lines. Normally, the grounding of the live and/or neutral lines is very dangerous and can cause very serious damage. Therefore, a grounded arc circuit breaker circuit is used to detect the grounding of the live and/or neutral lines, thereby eliminating dangerous conditions by disconnecting at least one wire between the load and the power source.

When the grounded arc circuit breaker circuit protects most people from the dangerous events of ground faults, there are other types of dangerous situations that are not protected by the grounded arc circuit breaker circuit. For example, in a cable, an arc may be generated between the live wire and the metal shield that wraps the cable. Although this arc may not pose a direct threat to the individual, it may cause the cable to burn. This is also a potential threat that cannot be ignored for people's health and safety.

A ground fault current circuit breaker circuit (GFCI) is disclosed in U.S. Patent 4,931,894, which provides the additional function of detecting and protecting the arc generated between the live wire and the metal layer or casing covering the power line. It is mainly used for arc protection with half-pressure protection. One of the arc protection coils is placed on the core of the GFCI differential transformer and is connected in series with a resistor and between the metal layer and the neutral or return line. The sensitivity to arc current protection is set to a predetermined level by adjusting the number of turns of the arc protection coil and the resistance value.

The above-mentioned U.S. Patent No. 4,931,894 A has a great drawback. In particular, the GFCI requires the use of a differential transformer for detecting arcs between the live wire and the metal layer or the neutral and metal layers, which will significantly increase the size and cost of the product. A safety circuit for a cable is disclosed in U.S. Patent 6,738,241 B1, which employs suspension sampling protection for arc protection. On the metal protective layer of the cable, it is usually in suspension. When an arc is generated between the live wire and/or the neutral wire and the metal protective layer of the cable, the arc directly triggers the thyristor protection through a special thyristor connection. The leakage protector is very common, and its arc current value is determined according to the current limiting resistor.

In the above-mentioned U.S. Patent No. 6,738,241 B1, since the thyristor is used, it cannot accurately adjust the arc current value.

Summary of the invention

SUMMARY OF THE INVENTION It is an object of the present invention to provide an arc protection and fire protection circuit that provides detection and protection against arcing between a live wire and/or a neutral wire and a metal shield and that accurately adjusts the value of the arc current.

The object of the present invention is achieved as follows: An arc protection and fire prevention circuit for a power cable, comprising a detecting portion, a sampling portion, a power supply portion, and a circuit breaking portion, characterized in that: arc protection of the power cable and series connection of the fireproof circuit In the power cable between the power source and the load, the on/off state of the power cable between the power source and the load is controlled by the open circuit relay in the arc protection and fireproof circuit; the circuit breaking portion includes the open circuit relay J, the amplifier, and the resistor R4. The output end of the amplifier is connected to the control coil L in the circuit breaker relay J, and the live line and the neutral line are respectively connected to the respective normally closed contacts in the circuit breaker relay J; the detecting portion includes two voltage dividing resistors R2 and R3 connected in series, and the series branch One end of the road is connected to the metal protection layer of the power cable of the load end, the other end is grounded or the neutral line, and the voltage dividing point between the two voltage dividing resistors R2 and R3 is connected with the sample rectifying portion; the sampling part includes the rectifying circuit and the filter capacitor C1, the input end of the rectifier circuit is connected to the voltage dividing point between the voltage dividing resistors R2 and R3 The rectified and filtered signal is input to the amplifier through the resistor R4; the power supply part includes the Zener diode DZ1, the storage capacitor C2 and the rectifying unit, and the input end of the rectifying unit is connected with the power source, and the output DC is stabilized by the Zener diode DZ1 and the storage capacitor C2. After the voltage, the operating voltage is supplied to the open circuit relay and the amplifier.

The advantages of the invention are: the circuit is simple, the circuit is protected by a suspension, when the fire line and / When an arc is generated between the center line and the metal protective layer of the wrapped cable, the power supply is quickly cut off, effectively preventing the occurrence of a fire. Due to the amplification of the transistors used, adjustments are made during production

The resistance ratio of R2 and R3 can accurately adjust the arc current value.

DRAWINGS

1 is an embodiment of an arc protection and fire protection circuit embodying the present invention;

Figure 2 is another embodiment of an arc protection and fire protection circuit embodying the present invention;

3 is a further embodiment of an arc protection and fire protection circuit embodying the present invention.

In the figure: 1, fire line, 2, center line, 3, ground line, 4, metal protective layer.

detailed description

The accompanying drawings are intended to be illustrative of the preferred embodiments of the invention

As shown in FIG. 1 , the present invention includes a detecting portion, a sample-like rectifying portion, a power supply portion, and a circuit breaking portion. The power cable includes a metal protective layer 4 and a live wire 1 and a neutral wire 2 wrapped by the metal protective layer 4, and arc protection of the power cable and The fireproof circuit is serially connected to the power cable between the power source and the load, and the on/off state of the power cable between the power source and the load is controlled by the arc circuit protection and the circuit breaker relay J in the fireproof circuit; the circuit breaking part includes the circuit breaker relay J, the amplifier The resistor 'R4, the output end of the amplifier is connected to the control coil L in the circuit breaker relay J, and the live line and the neutral line introduced at both ends are respectively connected with the corresponding normally closed contacts in the circuit breaker relay J; the detecting portion includes two series connected Voltage dividing resistors R2 and R3, one end of the series branch is connected to the metal protective layer of the power cable of the load end, the other end is grounded or the neutral line, and the voltage dividing point between the two voltage dividing resistors R2 and R3 is connected with the sample rectifying portion The sample rectification portion includes a rectifier circuit and a filter capacitor C1, and the input end of the rectifier circuit is connected to a voltage dividing point between the voltage dividing resistors R2 and R3. The rectified and filtered signal is input to the amplifier through the resistor R4. The power supply part includes the Zener diode DZ1, the storage capacitor C2 and the rectifying unit. The input end of the rectifying unit is connected to the power supply, and the output DC power is stabilized by the Zener diode DZ1 and the storage capacitor C2. After the voltage is applied, the operating voltage is supplied to the open circuit relay J and the amplifier. In this embodiment, the amplifier is a triode BG1, and the rectified and filtered signal is input to the three poles through the resistor R4. The collector of the tube BG1 and the transistor BG1 is connected to the control coil L in the breaking relay J, and the emitter is grounded or the neutral line; the breaking relay is provided with a reset switch IU; the detecting portion further includes a test switch K2 and a step-down a debugging branch composed of a resistor R1, one end of the debugging branch is connected to the live wire 1, and the other end is connected to the metal protective layer 4 of the power cable of the load end; the rectifier circuit in the sampling rectification portion includes a rectifier diode D1; The part further includes a diode D2 arranged in parallel with the control coil in the circuit breaker relay J; the rectifying unit in the power supply part is composed of diodes D3 and R5, and the output DC is grounded via the parallel Zener diode DZ1 and the storage capacitor C2 or Midline. In the specific implementation, the rectifier circuit in the sample rectification section can also use the bridge stack.

It can be seen from FIG. 2 that the embodiment is different from the embodiment shown in FIG. 1 only in that: the rectifying unit in the power supply portion is a rectifier bridge composed of a transformer B1 and four diodes D3-D6, instead of FIG. In the embodiment, the diodes D 3 and R5 and the output end of the rectifier bridge are connected in parallel with the Zener diode DZ1 and the storage capacitor C2. This embodiment can be generally used in the case where the power supply voltage is 110V.

It can be seen from FIG. 3 that the embodiment is different from the embodiment shown in FIG. 2 only in that: the primary part of the transformer B1 of the rectifying unit in the power supply part is connected in series with a capacitor C3, and the power supply voltage is high (when the power supply voltage is In the case of 220V or more, the voltage of the capacitor B3 can significantly reduce the volume of the transformer B1 and reduce the cost.

In use, since the live and neutral wires of the power cable between the power supply and the load are respectively connected to the corresponding normally closed contacts in the open circuit relay J, the power supply and the load are unblocked. When the power cable causes an arc between the live wire 1 or the neutral wire 2 and the metal shield 4 for some reason, the arc current forms a divided piezoelectric signal on the voltage dividing resistors R2 and R3, and the rectified divided piezoelectric signal is from the base. Resistor R4 input amplifier, the output signal of the amplifier is added to the open circuit relay; the DC current on the control coil L in T increases, the normally closed contact of the circuit breaker relay J is disconnected and clamped, and the power cable between the power supply and the load is cut off. , to achieve the purpose of arc protection and fire prevention. When the fault is removed, just press the reset switch K1, release the clamp to make the normally closed contact contact, and restore the power supply to the load. In order to detect the arc protection and the reliability of the fire protection circuit for the power cable, the arc generated by the live wire and the metal shield 4 can be simulated periodically or irregularly through the test switch K2 to verify the arc protection and fire circuit for the power cable. Can you cut off the power cable between the power supply and the load in time?

Claims

Patent claim

1. An arc protection and fire protection circuit for a power cable, comprising a detecting portion, a sampling portion, a power supply portion, and a circuit breaking portion, wherein:

a) The arc protection and fireproof circuit of the power cable are connected in series with the power cable between the power source and the load. The on/off state of the power cable between the power source and the load is controlled by the arc protection relay in the arc protection and fireproof circuit J;

b) The circuit breaking part includes a breaking relay J, an amplifier, and a resistor R4. The output end of the amplifier is connected with the control coil L in the breaking relay J, and the live line and the neutral line are respectively connected to the corresponding normally closed contacts in the breaking relay;

c) The detection part comprises two voltage-dividing resistors R2 and R3 connected in series, one end of the series branch is connected to the metal protection layer of the power cable of the load end, the other end is grounded or the neutral line, and between the two voltage-dividing resistors R2 and R3 The voltage dividing point is connected to the sample rectifying portion;

d) the sampling part comprises a rectifying circuit and a filter capacitor C1, the input end of the rectifying circuit is connected with a voltage dividing point between the voltage dividing resistors R2 and R3, and the rectified and filtered signal is input to the amplifier through the resistor R4;

e) The power supply part includes a Zener diode DZ1, a storage capacitor C2 and a rectifying unit. The input end of the rectifying unit is connected to the power supply, and the output DC is regulated by the Zener diode DZ1 and the storage capacitor C2 to provide work for the breaking relay and the amplifier. Voltage.

2 The arc protection and fire protection circuit for a power cable according to claim 1, characterized in that: the amplifier is a triode BG1, and the rectified and filtered signal is input to the triode BG1 via the resistor R4, and the collector of the transistor BG1 Breaking relay; The control coil L in the 连接 is connected, and the emitter is grounded or neutral.

3. The arc protection and fire protection circuit for a power cable according to claim 1, The utility model is characterized in that: the breaking relay is provided with a reset switch K1; the detecting portion further comprises a debugging branch composed of a test switch K2 and a step-down resistor R1, one end of the debugging branch is connected to the live line, and the other end is connected to the load The metal cable on the end of the power cable.

4. An arc protection and fire protection circuit for a power cable according to claim 1 or 2 or 3, wherein: said rectifier circuit in said sample-like rectification portion comprises a rectifier diode D1 or a bridge stack.

5. The arc protection and fire protection circuit for a power cable according to claim 1 or 2 or 3, wherein the rectifying unit in the power supply portion is composed of diodes D1 and R5, and the output DC is regulated. The diode DZ1 is connected in parallel with the storage capacitor C2 and grounded or connected to the neutral line.

6. The arc protection and fire protection circuit for a power cable according to claim 1 or 2 or 3, wherein: said rectifying unit in said power supply portion is rectified by transformer B1 and four diodes D3-D6 The output of the bridge and the rectifier bridge is connected in parallel with the Zener diode DZ1 and the storage capacitor C2.

7. The arc protection and fire protection circuit for a power cable according to claim 1 or 2 or 3, wherein the circuit breaking portion further comprises a diode 02 disposed in parallel with the breaking relay: [the inner control coil.

8. The arc protection and fire protection circuit for a power cable according to claim 6, characterized in that: a capacitor C3 is connected in series with the primary end of the transformer B1 in the rectifier unit.