JPH05276651A - Protective system for distribution line - Google Patents

Abstract

PURPOSE:To provide a protective system for distribution line in which the distribution line or line machines are protected against damage due to arc of fault current caused by thunderbolt. CONSTITUTION:Jumper wire 4 of distribution line 1 is passed through the case of a branch unit 5, and a zero-phase voltage detecting means and a phase current detecting means are arranged in the line. The jumper wire 4 is further connected through a switching means 11 with a branch line 13 which is led out to the outside and connected, at the end thereof, with a forced short circuit unit 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power distribution line protection system for protecting a power distribution line or a line device from an overcurrent caused by a ground fault or a short circuit accident.

[0002]

2. Description of the Related Art Conventionally, a circuit breaker equipped with an overcurrent relay (OCR) is installed in a distribution substation, and when a ground fault or a short-circuit accident due to a lightning strike occurs in a distribution line, an overcurrent occurs. Is detected, the circuit breaker is opened, and the line is protected by shutting down the line. However, the circuit breaker of the distribution substation has about 10 cycles (50Hz) at commercial frequency after detecting the overcurrent in order to coordinate with the circuit breakers of customers.
Since it was set to operate after about 0.2 seconds), the distribution line and line equipment of the system could be damaged by the arc of the fault current during this period.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to forcibly short-circuit a line immediately when an overcurrent is detected, so that a distribution line or a line device can be protected from a fault current. An object of the present invention is to provide a protection system for distribution lines that can prevent damage due to arcs. Another object of the present invention is to provide a distribution line protection system that simplifies the columns and facilitates inspection and repair of the lines.

[0004]

SUMMARY OF THE INVENTION The present invention, which has been made in order to solve the above-mentioned problems, is designed to pass a jumper wire of a distribution line into a case of a branching device, and to connect a zero-phase voltage detecting means to a circuit of the jumper wire. Current detecting means is provided, a branch line is connected to the jumper wire via the opening / closing means, the branch line is drawn out from the branching device, and the forced short-circuiting device is connected to the terminal. ..

[0005]

In the distribution line protection system of the present invention, the forcible short-circuit device forcibly short-circuits the jumper wire as soon as a lightning surge or the like is detected by the zero-phase voltage detection means and the phase current detection means. Attenuated to prevent damage to distribution lines and line equipment due to arcs. In addition, since the jumper wire is passed through the case of the branching device and the detecting means is provided, protection of the detecting means and simplification of the mounting column can be achieved. Furthermore, because the forced short-circuit device is installed at the end of the branch line via the opening / closing means, the forced short-circuit device can be easily separated from the distribution line, facilitating maintenance, and even if the branch line is opened / closed. The system is not affected.

[0006]

The present invention will now be described in more detail with reference to the illustrated embodiments. FIG. 1 is a diagram showing an example of a pillar of a protection system for a distribution line of the present invention, and FIG. 2 is a circuit diagram thereof. Figure 1
In the figure, 1 is a three-phase distribution line, each line is supported by a support insulator 3 at the upper end of the utility pole 2, and the extra length grasped by the both-end clamps 31 of the insulating spacer 30 interposed in the middle part is a jumper line. 4 is drawn into the case of the branching device 5. These jumper wires 4 are supported by bushings 6 and 7, and are connected by a relay conductor 8 in the case of the branching device 5. As shown in FIG. 2, the bushing 7 is a bushing CT having a CT 9 and constitutes a phase current detecting means for detecting the current value of each phase. Further, a voltage dividing capacitor is provided between the relay conductors 8 of each phase.
10 is provided and constitutes a zero-phase voltage detecting means.

In the case of the branching device 5, an opening / closing means 11 is connected adjacent to the relay conductor 8. This opening and closing means
As shown in FIG. 2, reference numeral 11 is composed of contacts and an opening / closing control coil 12, and a branch line 13 is drawn out of the branching device 5 via the opening / closing means 11. A forced short-circuit device 14 is connected to the end of the branch line 13. In the example, the forced short-circuit device
Reference numeral 14 is a thyristor, and when this is closed, the three phases are forcibly short-circuited. Reference numeral 15 is a command unit housed in the case 16 of the forced short-circuit device 14, and commands the opening / closing of the forced short-circuit device 14 as described later.

Reference numeral 17 is a low-voltage line supported by a low-voltage insulator 18 on the electric pole 2, and is connected to a control circuit 20 via a connector 19. The control circuit 20 receives power supply from the low voltage line 17 and controls the opening / closing means 11 described above. In the upper left portion of FIG. 2, reference numerals 21 and 22 surrounded by a chain double-dashed line are detection signal processing units connected to the above-mentioned zero-phase voltage detection means and phase current detection means. explain.

In the embodiment of FIG. 1, the jumper wire 4 is drawn into the case of the branching device 5 from the same direction, but in this configuration, the jumper wires on both sides are drawn into the switch from the same height. This is for the convenience of maintenance by facilitating the distinction from the normally installed pillars in the railway.

Next, the operation of the apparatus of the embodiment will be described. The opening / closing means 11 of the present device may be normally closed, but in that case, since the voltage is constantly applied to the thyristor of the forced short-circuit device 14, the thyristor may gradually deteriorate. Therefore, it is more preferable that the opening / closing means 11 is normally open and is closed only when the lightning approaches. This case will be described below. First, when the lightning approaches, the zero-phase voltage of the distribution line 1 changes as shown as V ₀₁ to V ₀₅ in the upper graph of FIG. 4, and the zero-phase voltage detecting means detects this. When such a change in zero-phase voltage occurs, the control circuit 20 closes the opening / closing means 11 to prepare for a lightning strike. However, the detection signal processing unit 21 includes the time limit circuit 23, and after the last rise of the zero-phase voltage exceeding the reference value, for example, 10
If the zero-phase voltage does not rise for a minute, the switching means 11
Try to open again.

When a lightning strike occurs when the opening / closing means 11 is closed to prepare for a lightning strike as described above, the zero-phase voltage detecting means detects the lightning surge voltage V ₀₆ exceeding the reference value,
Further, the phase current detecting means detects a lightning surge current I ₂ which exceeds a reference value (for example, 400 A). Then, the level determination circuit 24 in the detection signal processing unit 21 and the level determination circuit 25 in the detection signal processing unit 22 generate outputs, and the AND circuit in the command unit 15
Signal to 26. When the AND condition is satisfied, that is, when the zero-phase voltage detected by the zero-phase voltage detection means and the phase current detected by the phase current detection means closing means both exceed the reference level, the forced short-circuit device is provided. Immediately operate 14 thyristors to forcibly short-circuit each phase. This attenuates the lightning surge current on the distribution line 1,
The arc due to a lightning strike goes out. In this way, the distribution line 1 and the distribution device can be protected.

However, if the lightning surge exceeds the function of this device and the arc cannot be extinguished by operating the forced short-circuit device 14, after about 10 cycles, the substation The circuit breaker operates to cut the power to the distribution line 1. In this case, the operation of this device has failed, but the power failure of the low voltage line 17 which occurs at the same time is detected and the opening / closing means 11 is opened.

[0013]

The protection system for a distribution line according to the present invention described above has the following excellent advantages. When a fault current due to a lightning strike or the like is detected, the distribution line is immediately forcibly short-circuited, the fault current is attenuated to extinguish the arc, and damage to the distribution line or distribution equipment due to the arc can be prevented. The jumper wire is pulled through the case of the branching device, and the zero-phase voltage detection means and the phase current detection means are provided in the electric path of the jumper wire, so these detection means can be protected and the line can be easily inspected and repaired. Is. The jumper wire was connected to the branch line via the opening / closing means, this branch line was pulled out of the branching device to the outside, and the forced short-circuit device was connected to the terminal. Easy to check,
Opening / closing the opening / closing means does not affect the distribution line. If the opening / closing means is closed only when the lightning approaches as in the embodiment, the deterioration of the forced short-circuit device can be prevented.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an embodiment of the present invention.

FIG. 3 is an output waveform diagram of the zero-phase voltage detection means and the phase current detection means.

[Explanation of symbols]

 1 Distribution line 4 Jumper wire 5 Branching device 7 CT 10 as phase current detecting means 10 Voltage dividing capacitor as zero phase voltage detecting means 11 Switching means 13 Branching wire 14 Forced short-circuiting device

Claims (2)

[Claims] 1. A jumper wire of a distribution line is drawn into a case of a branching device, a zero-phase voltage detecting means and a phase current detecting means are provided in an electric path of the jumper wire, and the jumper wire is branched via an opening / closing means. A power distribution line protection system, characterized in that a forcible shorting device is connected to the terminal of the branching line by pulling out this branching line from the branching device to the outside. 2. The forced short-circuit device is activated when both the zero-phase voltage detected by the zero-phase voltage detecting means and the phase current detected by the phase current detecting means exceed a reference level. Distribution line protection system as described.