JP2000166079A - Lightning surge protective circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a communication device against multiple and successive lightning surges or a long-lasting surge by connecting a current detector detecting the discharge current of a surge arrestor to the ground side of the surge arrestor, and interrupting an electromagnetic contactor if a control circuit detects the discharge current by means of the current detector. SOLUTION: When a lightning surge intruding from an AC power supply line 1 exceeds the discharge starting voltage of a surge arrester 2, the lightning surge is discharged to the ground through the surge arrester 2, so that the discharge current is detected by a current detector 3. A control circuit 8 breaks an electromagnetic contactor 9 instantaneously when the current detector 3 detects the discharge current. At this moment, a surge at or below the discharge starting voltage of the surge arrester 2 intrudes an automatic voltage regulator 5 and a communication device 10, however, the electromagnetic contactor 9 is interrupted immediately thereafter, thus the subsequent surges or a long lasting surge are prevented from entering the communication device 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightning surge protection circuit mainly mounted on a broadcasting transmitter installed in an area where lightning strikes frequently.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing a power supply system of a conventional communication device. In the figure, a communication device 10
Power is supplied from the AC power supply line 1 via a circuit breaker 4, an automatic voltage regulator 5, and an electromagnetic contactor 9. The automatic voltage regulator 5 includes a voltage detector 51 that detects an output voltage,
It is composed of a voltage regulator 52 for adjusting the output voltage and an automatic control circuit 53 for controlling the voltage regulator 52 in accordance with the detection voltage of the voltage detector 51, so that the power supply voltage supplied to the communication device 10 is adjusted to be constant. I do.

An open-phase / opposite-phase relay 7 is connected to the input side of the automatic voltage regulator 5, and an overvoltage relay 6 is connected to the output side. Open-phase / reverse-phase relay 7 and overvoltage relay 6
Is connected to the electromagnetic contactor 9. Due to the fluctuation of the receiving voltage exceeding the adjustment range of the automatic voltage regulator 5,
When the output voltage of the automatic voltage regulator 5 exceeds a rated value (for example, rated voltage + 10%) for a certain period of time (for example, 2 seconds) or more, the overvoltage relay 6 detects this and shuts off the electromagnetic contactor 9. When the output voltage of the automatic voltage regulator 5 falls within the rated value, the electromagnetic contactor 9 is controlled to automatically return. Thus, it is possible to prevent the overvoltage from being supplied to the communication device 10 and being damaged.

[0004] When the receiving voltage is out of phase or out of phase, the out-of-phase / out-of-phase relay 7 detects this and shuts off the electromagnetic contactor 9. When the receiving voltage returns to the steady state,
The electromagnetic contactor 9 is controlled to return automatically. As a result, it is possible to prevent the power supply of the open phase or the opposite phase from being supplied to the communication apparatus 10 and causing the operation failure.

As described above, the protection of the communication device 10 against the overvoltage of the receiving voltage is performed by the power supply to the communication device 10 being cut off by the overvoltage relay 6 and the electromagnetic contactor 9. However, the automatic voltage regulator 5 and the overvoltage relay 6 cannot follow an instantaneous high voltage such as a lightning surge due to operating conditions such as sensitivity and detection time.

Therefore, as protection against lightning surge, A
The surge on the input side of the automatic voltage regulator 5 on the C power supply line 1
The arrester 2 is connected to discharge the lightning surge entering from the AC power supply line 1 to the ground via the surge arrester 2.

[0007]

The surge that is lower than the discharge starting voltage of the surge arrester 2 enters the automatic voltage regulator 5 and the communication device 10. Parts and wiring used for the automatic voltage regulator 5 as a power circuit have a surge withstand capability exceeding this surge. However, the high-frequency circuit, the low-frequency circuit, the control circuit, the small relay, and the like inside the communication device 10 have a small surge resistance and may be damaged by the surge.

By the way, a lightning surge is not a single one, but a plurality of lightning surges may arrive continuously. Some lightning surges have a long surge duration alone. Depending on the magnitude, number, and duration of the lightning surge, the discharge of the surge arrester 2 alone may not be able to protect the communication device 10 from the lightning surge that enters through the AC power supply line 1.

It is an object of the present invention to provide a lightning surge protection circuit capable of protecting a communication device against a plurality of lightning surges that continuously arrive or have a long duration.

[0010]

SUMMARY OF THE INVENTION The present invention provides a lightning surge protection for a communication device to which power is supplied via an automatic voltage regulator for controlling a power supply voltage supplied from an AC power supply line to be constant and an electromagnetic contactor. In the circuit, connect a surge arrester between the AC power supply line and the ground to discharge the lightning surge that enters from the AC power supply line to the ground, and provide a current detector that detects the discharge current of the surge arrester on the ground side of the surge arrester. Connected to perform control to shut off the electromagnetic contactor when the control circuit detects the discharge current with the current detector.

Further, the control circuit performs a control to automatically return the electromagnetic contactor when the discharge current is not detected by the current detector after a predetermined time has elapsed after the electromagnetic contactor is shut off.

[0012]

FIG. 1 is a block diagram showing an embodiment of a lightning surge protection circuit according to the present invention. In the figure,
The communication device 10 is supplied with power from the AC power supply line 1 via the circuit breaker 4, the automatic voltage regulator 5, and the electromagnetic contactor 9. The automatic voltage regulator 5 includes a voltage detector 51, a voltage regulator 52, and an automatic control circuit 53 similar to those in the conventional configuration, and adjusts the power supply voltage supplied to the communication device 10 to be constant. The overvoltage relay 6 and the open-phase / out-of-phase relay 7 are connected to each other when an overvoltage of the output voltage of the automatic voltage regulator 5 is detected, or when the receiving voltage becomes open or out of phase, as in the conventional configuration. 9 is shut off so that an abnormal voltage is not supplied to the communication device 10.

A surge arrester 2 is connected between the input side of the automatic voltage regulator 5 on the AC power supply line 1 and the ground,
The lightning surge that enters from the AC power supply line 1 is discharged to the ground via the surge arrester 2.

Here, a feature of the present invention is that a current detector 3 for detecting the discharge current of the surge arrester 2 is connected to the ground side of the surge arrester 2, and an electromagnetic contactor 9 is provided when the discharge current is detected. It is in the composition which shuts off. The control circuit 8
The output of the current detector 3 is monitored, and when the discharge current of the surge arrester 2 is detected, control for shutting off the electromagnetic contactor 9 is performed. In addition, after a certain period of time (for example, one second) after the electromagnetic contactor 9 is shut off, if there is no lightning surge on the AC power supply line 1 and the discharge of the surge arrester 2 is stopped, the control circuit 8 sets the electromagnetic contactor The controller 9 is controlled to automatically return.

With such a configuration, when the lightning surge entering from the AC power supply line 1 exceeds the discharge starting voltage of the surge arrester 2, the lightning surge is discharged to the ground via the surge arrester 2, and the discharge at this time is performed. Current is current detector 3
Is detected. The control circuit 8 instantaneously shuts off the electromagnetic contactor 9 when the current detector 3 detects the discharge current.
At this time, a surge equal to or lower than the discharge starting voltage of the surge arrester 2 enters the automatic voltage regulator 5 and the communication device 10, but the electromagnetic contactor 9 is immediately shut off thereafter.
It is possible to prevent a plurality of subsequent surges or surges having a long continuous time from entering the communication device 10.

[0016]

As described above, the lightning surge protection circuit of the present invention discharges a surge arrester when a lightning surge enters from an AC power supply line, and detects the discharge current to activate an electromagnetic contactor. It shuts off and temporarily stops the supply of the power supply voltage to the communication device. As a result, it is possible to prevent a plurality of subsequent surges or a surge having a long duration from invading the communication device, and protect circuit components in the communication device from damage due to lightning surge.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a lightning surge protection circuit according to the present invention.

FIG. 2 is a block diagram showing a power supply system of a conventional communication device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC power supply line 2 Surge arrester 3 Current detector 4 Circuit breaker 5 Automatic voltage regulator 6 Overvoltage relay 7 Open-phase / out-of-phase relay 8 Control circuit 9 Electromagnetic contactor 10 Communication device 51 Voltage detector 52 Voltage regulator 53 Automatic Control circuit

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H02H 7/20 H02H 7/20 E 9/06 9/06

Claims (2)

[Claims] 1. An automatic voltage regulator for controlling a power supply voltage supplied from an AC power supply line to be constant, and a power supply when an output voltage of the automatic voltage regulator becomes overvoltage or when an open phase or an antiphase of the power supply voltage is detected. In a lightning surge protection circuit of a communication device to which power is supplied via an electromagnetic contactor for interrupting a voltage, the lightning surge protection circuit is connected between the AC power supply line and a ground, and discharges a lightning surge entering from the AC power supply line to a ground. surge·
An arrester, a current detector connected to the ground side of the surge arrester, and detecting a discharge current of the surge arrester, monitoring the current detector, and detecting the discharge current, the electromagnetic contactor. A lightning surge protection circuit, comprising: a control circuit that performs a control to cut off the lightning. 2. The control circuit according to claim 1, wherein when the discharge current is not detected by the current detector after a lapse of a predetermined time after the electromagnetic contactor is shut off, the control circuit automatically controls the electromagnetic contactor to return. Lightning surge protection circuit.