JPS60257369A - Arc current detecting device - Google Patents

Abstract

PURPOSE:To detect the generation of an arc without expecting the extinction of an arc current by detecting arc current on conditions that the current value is above the prescribed value and yet of irregular variation. CONSTITUTION:A differentiation circuit 6 passes through the portion of current variation. In the accident excluding an arc of the short in power system, etc., however, the current value is hardly changed and it is not passed through. The arc current in a power system and a troubled current are therefore discriminated by whether or not they can pass through the circuit 6. The size of the output of the circuit 6 is compared with the reference voltage by a level discriminating circuit 7 and in case of the output of the circuit 6 being larger a point (d) becomes a high level. When the high levelled condition is continued for the prescribed time, then, the point (d) becomes a low level and a relay contact 11 is turned on with the excitation of a relay coil 9. An over-current detecting circuit 5 is motioned similarly and turns a relay contact 10 on when the over-current holds the current value beyond the prescribed for the prescribed time. At the time when the prescribed time proceeded after the generation of an arc, relay contacts 10, 11 are turned on and an arc generation output signal is outputted, and the detection of the arc generation is enabled without expecting the extinction of an arc current.

Description

[Detailed description of the invention] The present invention relates to an arc current detection device.

Conventional arc current detection devices detect arc current only after a fault occurs in the power system and the power line is fused. In other words, there was a problem that the arc current could not be detected unless it was fused.10 Specifically, /8
Since the device detects state changes based on rupture, it cannot detect cases where the arc is temporary (for example, due to lightning or contact with a tree, etc.) and does not result in fusion G.
Therefore, since maintenance was not possible, there was a problem in that it was only a matter of preventing future accidents.

An object of the present invention is to provide an arc current detection device that detects an arc current before a power line is fused when an arc occurs.

An embodiment of the present invention will be described based on FIGS. 1 to 4. In Figure 1, ■ is a power line, 2 is a current transformer coupled to power line 1, 3 and 4 are current/voltage converters connected in series with current transformer 2, and 5 is both ends of current/voltage converter 3. an overcurrent detection circuit connected between 6 and a differentiating circuit as a current fluctuation detection circuit connected between both ends of the current/voltage converter 4;
For example, Leher'r11 constant circuit is connected to the output terminal of the differentiating circuit 6, and 8 and 9 are overcurrent detection circuits 5. Level: l'11 is a relay coil connected to the constant circuit child circuit 7 terminal, 10.11 is a normally open relay contact that responds to relay coils 8 and 9, and these relay contacts 10.11 are connected between output terminals Δ and B. connected in series. Relay coils 8, 9, relay contacts 10, 11
constitutes the arc detection circuit Ar.

The overcurrent detection circuit 5 and the level determination circuit 7 have the same circuit structure, and are specifically constructed as shown in FIG. 2. That is, a rectifying and smoothing circuit 12 consisting of a diode I]1 and a capacitor C1, a comparison circuit 13 consisting of a resistor R1, a reference voltage source E1, and a comparator OP, a resistor R2, a diode D2, a capacitor C2, and a reference voltage source -E2. =1 Time limit circuit 1 consisting of amplifier lake OP2
It is composed of 4.

As shown in FIG. 3, the differentiating circuit 6 includes a capacitor c3 and a resistor R3. The differential circuit 6 easily passes the current value change, but in the case of an accident other than an arc such as a short circuit in the power system, the current value does not change significantly, so it is not possible to pass the current value, and the output at that time is It is almost O. therefore,? The arc current and fault current of the Ti power system are distinguished depending on whether they pass through the differentiation circuit 6 or not.

The magnitude of the output of the differentiating circuit 6 is compared with the reference voltage by the comparison circuit 13, and when the output is larger, the output of the comparator OP becomes high level.

A time limit circuit 14 determines whether this high level state continues for a predetermined time, and when it continues, the output of the comparator OP2 becomes low level, and the relay coil 9 is energized to close the relay contact 11.

The overcurrent detection circuit 5 operates similarly, and when the overcurrent continues to have a current value of a predetermined value or more for a predetermined time, the relay coil 8 is energized and the relay contact 10 is closed.

Current (point a) and voltage (point a) at points a-d in Figure 1
The waveforms at points b to d) during normal operation are shown in FIG. 4(A), and the waveforms at the time of arc occurrence are shown in FIG. 4(B).

During normal operation, since both points b and d are at high level, both relay coils 8 and 9 are not excited, and relay contacts 10.
11 are both off, so no output signal is generated. When an arc occurs, when a predetermined time To has elapsed after the occurrence of an arc, both points b and d become low level, both relay coils 8.9 are energized, relay contacts 10 and 11 are turned on, and an output signal indicating the occurrence of an arc is generated. It will be done.

That is, unlike the conventional example in which arc generation is detected only after the arc current disappears, arc generation can be detected without the arc current disappearing.

Furthermore, it is possible to detect arc current in one wire in a directly grounded system. Further, it is possible to detect arc current without causing a ground fault.

Note that -1- below describes one phase (A phase, B phase, or C phase), but when applied to a distribution line system, A
It shall be installed in phase, C phase, and for systems with extra height or higher, Δ phase,
What should be installed in the B and C phases?

Although the embodiments have been described below, the arc current detection device of the present invention includes an overcurrent detection circuit coupled to a power line, a current variation detection circuit coupled to the power line, and an output of this current variation detection circuit. A level 'i'l constant circuit connected to the terminal, the output of the overcurrent detection circuit, and the output of the above 1. - It is equipped with an arc detection circuit that operates based on a logical product with the output of the health determination circuit and outputs a detection signal of arc current occurrence.

According to this invention, the arc current is detected on the condition that the current value of the arc current is equal to or higher than a predetermined value and fluctuates irregularly. This has the effect of being able to detect even temporary accidents such as contact with wood or wood.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of an embodiment of the present invention, Fig. 2 is a circuit diagram of its overcurrent detection circuit or level judgment circuit, Fig. 3 is a circuit diagram of its differential circuit, and Fig. 4 is a waveform diagram of each part. It is. ■...Power line, 5...Overcurrent detection circuit, 6...
Differential circuit (current fluctuation detection circuit), 7... Level judgment circuit, Ar... Arc detection circuit □ Time (A)゛ 4th

Claims (1)

[Claims] an overcurrent detection circuit coupled to the power line, a current fluctuation detection circuit coupled to the power line, a level determination circuit connected to the output end of the current fluctuation detection circuit, and an output of the overcurrent detection circuit and the level determination circuit. An arc current detection device comprising: an arc detection circuit that operates by logical product with the output of the circuit and outputs a detection signal of arc current generation;