JPH05227650A - Lightning failure detection device - Google Patents

Abstract

PURPOSE:To provide a detector capable of discriminating exactly whether an overcurrent running in a transmission line is due to a follow current caused by a lightning flashover or due to other causes. CONSTITUTION:A lightning surge voltage is detected by a lightning surge voltage detector mounted on a transmission line 1. Only when an excess current detector 3 detects an excess current within a specific time after that, a discriminating device 4 determines that a follow current is generated due to a lightning flashover. In this way, it becomes possible to distinguish this type of failure from the failure due to a flash to ground without the generation of any follow current, and a short circuit without any transient excess current or surge voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightning accident detecting device which is used by being incorporated in a system or the like for preventing disconnection of a distribution line due to a lightning accident.

[0002]

2. Description of the Related Art With the recent widespread use of insulated electric wires, if there is a lightning strike on a distribution wire, the lightning surge may cause the electric wire coating to penetrate and break down.
A flashover accident has occurred. When such a flashover occurs in a plurality of phases, the follow-up arc is fixed at the break-through point, and the heat of the arc may melt the electric wire. Therefore, a distribution line breaker and a protective relay have been installed in the distribution line to protect the system, but this protection relay is slow, for example, 0.2 seconds in order to coordinate time with the customer circuit breaker. Since it has operating characteristics, there is a problem that the distribution line is disconnected due to an accident arc before the distribution line breaker operates.

Therefore, in order to prevent the disconnection due to such an arc, a semiconductor type switch is attached to the distribution line, and when an overcurrent flows in the distribution line, the distribution line is momentarily forcibly short-circuited and the arc is generated. A method of extinguishing the arc is being put to practical use. However, in this method, the presence or absence of an arc was determined only based on the magnitude of the current.Therefore, whether it is a lightning current due to a lightning strike, a transient overcurrent such as a motor starting current, or an arc current caused by a lightning strike, There is a problem that it is not possible to distinguish whether it is a fault current due to a short-circuit accident, and malfunction occurs in the case of lightning current due to lightning strike or transient overcurrent, and unnecessary operation occurs in the case of fault current due to short-circuit accident.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and determines whether the overcurrent flowing through a distribution line is an overcurrent due to a follow-up arc caused by a lightning flashover or other causes. It was completed in order to provide a lightning accident detection device that can accurately determine whether it is an overcurrent.

[0005]

SUMMARY OF THE INVENTION The present invention, which has been made to solve the above-mentioned problems, has a detector for a lightning surge voltage traveling on a distribution line due to a lightning strike, and an overcurrent detector for mounting on the distribution line. , A detector is provided to judge that a follow-up arc due to lightning flashover has occurred only when an overcurrent is detected within a certain time after the lightning surge voltage is detected by these detectors. It is a feature.

[0006]

The judging device of the lightning accident detecting device of the present invention does not judge that the follow-up arc caused by the lightning flashover has occurred simply by detecting the overcurrent, and does not determine the constant value after the lightning surge voltage is detected. Only when the overcurrent is detected within the time, it is judged that the follow-up arc caused by the lightning flashover has occurred.Therefore, the overcurrent due to the follow-up arc caused by the lightning flashover or the other cause may occur. It is possible to accurately determine whether it is a current. Therefore, if the semiconductor switch is operated only in the former case in accordance with the result, malfunctions and unnecessary operations as in the conventional case can be omitted.

[0007]

The present invention will be described in more detail with reference to the embodiments shown in the drawings. In FIG. 1, 1 is a distribution line, 2 is a lightning surge voltage detector mounted on this distribution line,
Reference numeral 3 is an overcurrent detector also mounted on the distribution line, and reference numeral 4 is a determination device which operates by receiving the outputs of these detectors 2 and 3.

When there is a lightning strike at point A, a lightning surge having a waveform as shown in the figure advances left and right on the distribution line 2 at the speed of light, and when the voltage exceeds the withstand voltage of the insulator device on the way, flashover occurs and flashover occurs. Due to this flashover, the lightning surge of the waveform that the tail is cut from the first lightning surge is further distributed
Go on top. Further, in the insulator device, a follow-up arc is generated due to the flashover, and if it is fixed and continued, the distribution line is melted.

FIG. 2 is a graph in which the lightning surge voltage detected by the detectors 2 and 3 and the overcurrent flowing subsequently thereto are displayed on the same time axis. In the case of a lightning strike, the lightning surge voltage is detected first, and immediately after that, the overcurrent is detected. On the other hand, in the case of lightning current due to lightning strike, the waveform has a surge superimposed on the normal load current, and in the case of a normal short-circuit accident or transient overcurrent such as motor starting current, there is no lightning surge voltage Only the current will be detected. Therefore, in the present invention, it is determined whether or not a follow-up arc due to lightning flashover has occurred by utilizing the combination of the lightning surge voltage and the overcurrent.

FIG. 3 shows the internal construction of the judging device 4 in the embodiment. The outputs of the detectors 2 and 3 are first input-converted by the input converters 5 and 6, and then the level judging parts 7 and 8.
Are input respectively. Here, lightning surge voltage detector 2
As for the overcurrent detector 3, a suitable one such as a CT, an optical sensor or the like is used as the overcurrent detector 3.

The voltage level determination unit 7 is further 10% of the value obtained by adding ± 10% as the voltage variation to the operating voltage of the distribution line 2.
The increased voltage is used as a threshold value, and when a voltage exceeding this is detected, it is determined that the lightning surge voltage has been detected. The fault current level determination unit 8 determines that overcurrent is detected when a current exceeding 500% of the load current is used as a threshold value.

An output hold circuit 9 is connected to the voltage level determination section 7 and holds the output for a fixed time (for example, 10 ms) after detecting a lightning surge voltage.
Since the lightning surge voltage travels on the distribution line 1 at almost the speed of light, for example, even if a lightning strike occurs at the end of a line with a constant length of 100 km, it will take about 30 minutes to reach the distribution substation where the device of the present invention is installed. It only takes 0.33ms. For this reason, it is sufficient to hold the output for 10 ms, which corresponds to a half cycle of the commercial frequency (50 Hz), and when a follow-up arc occurs due to lightning flashover, the accident current is always detected during this period.

Therefore, only when the lightning surge voltage is detected and the overcurrent is detected within the fixed time during which the output hold circuit 9 holds the lightning surge voltage, the determination circuit 4 produces an output and is caused by the lightning flashover. It is determined that a follow-up arc has occurred. FIG. 4 is a block diagram showing this operation flow.

As described above, in the lightning accident detection device of the present invention, the follow-up arc caused by the lightning flashover is generated only when the overcurrent is detected within the fixed time after the lightning surge voltage is detected. Since the determination is made, it is possible to accurately determine whether the overcurrent is caused by the follow-up arc caused by the lightning flashover or the overcurrent caused by other causes. Therefore, as shown in FIG. 5, if the semiconductor switch 10 is controlled by using this lightning accident detection device, the semiconductor switch 10 is closed only when a follow-up arc occurs due to a lightning flashover, and the distribution line is closed. It becomes possible to extinguish the arc by forcibly shorting the line before the circuit breaker starts operating. In this case, it becomes possible to open the semiconductor switch 10 immediately after extinguishing the arc and restore the system to the normal state.

[0015]

As described above, according to the present invention, it is possible to accurately determine whether the overcurrent is caused by the follow-up arc caused by the lightning flashover or the overcurrent caused by other causes. As in the prior art, it is possible to prevent malfunctions in the case of transient currents such as lightning currents due to lightning strikes and motor starting currents, and unnecessary operations in the case of normal short circuit accidents. Therefore, the present invention contributes greatly to industrial development as a lightning accident detection device that solves the conventional problems.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between voltage and current in the event of a lightning strike.

FIG. 3 is a block diagram showing a main part of the embodiment.

FIG. 4 is a flow sheet showing an operation flow of the embodiment.

FIG. 5 is a circuit diagram showing an example in which the device of the embodiment is combined with a semiconductor switch.

[Explanation of symbols]

 1 Distribution line 2 Lightning surge voltage detector 3 Overcurrent detector 4 Judgment device

Claims (1)

[Claims] 1. A lightning surge voltage detector traveling on a distribution line due to a lightning strike and a fault current detector are mounted on the distribution line, and within a fixed time after the lightning surge voltage is detected by these detectors. A lightning accident detection device comprising a determination device that determines that a follow-up arc due to a lightning flashover has occurred only when an overcurrent is detected in the.