JPH03120481A - Measurement of partial discharge on live-line cable - Google Patents

Abstract

PURPOSE:To detect partial discharge with high sensitivity by connecting a bypass circuit, in which a capacitor and resistor are connected in series, to the earth line in parallel at the part of ferrite core and taking out a high frequency electric pulse from both ends of the resistor. CONSTITUTION:When an impedance 5 for partial discharge detection is constituted with the bypass circuit 11, in which the capacitor 9 and resistor 10 are connected in series, connected to the earth line 4a in parallel at the part of ferrite core 8 provided with penetrating the earth line 4a, a current with commercial frequency flowing to the earth line 4a is made to flow to the earth side passing through the core 8 and not to the side of circuit 11 due to the core 8 is a low impedance element. On the other hand, since the core 8 is the high impedance element for the high frequency electric pulse caused from the partial discharge generated on a live-line cable 1, this high frequency electric pulse is unable to pass through the core 8 and is made to flow to the side of circuit 11. Consequently, by means of taking out a signal from both ends of the resistor 10, the efficiency for taking out the signal is improved and the partial discharge can be detected with high sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for measuring partial discharge in live cables.

[Prior Art] Conventionally, as shown in FIG. 4, partial discharge of a live cable has been measured using grounding wires 4a to 4e provided at both end portions 2, intermediate connection portion 3, etc. of a live cable 1. A current transformer 6 is connected to one of the grounding wires, for example, the grounding wire 4a, as an impedance 5 for detecting partial discharge, and the high-frequency electric pulses generated by the partial discharge occurring within the live cable 1 are transferred to the current transformer 6. This was done by extracting the signal from the source and amplifying it using the amplifier 7.

[Problems to be Solved by the Invention] However, in the conventional partial discharge measuring method as described above, there is a problem that highly sensitive partial discharge measurement cannot be performed due to the following reasons (1) and (2).

(2) Partial discharge cannot be measured with high sensitivity because the electrical coupling ratio between the current transformer 6 and the grounding wire 4a is insufficient.

(2) As shown in FIG. 4, a normal live cable 1 is often grounded at two or more points by grounding wires 4a to 40, etc. For this reason, the high frequency electric pulse generated by the partial discharge also flows to the ground wires 4b to 4e other than the ground wire 4a on which the current transformer 6 is installed. In other words, ground wire 4
If there are grounding wires 4b to 4e other than a, the grounding wire 4a
The proportion of the amount of high frequency electrical pulses passing through the ground wire 4b
~4e decreases compared to the case where it does not exist. For this reason,
Highly sensitive partial discharge measurements cannot be performed.

An object of the present invention is to provide a partial discharge measurement method that easily and highly sensitively measures partial discharges caused by insulation faults in live cables.

[Means for Solving the Problems] A detailed explanation of the present invention for achieving the above object is as follows.

The invention of claim (1) is characterized in that a partial discharge detection impedance is attached to the grounding wire of the live cable, and a high frequency electric pulse generated by a partial discharge generated in the live cable is taken out via the partial discharge detection impedance. In the live cable partial discharge measurement method, the partial discharge detection impedance includes a ferrite core that is provided through the ground wire, and a ferrite core that is connected in parallel to the ground wire at the ferrite core. The invention of claim (2) is characterized in that the bypass circuit comprises a capacitor and a resistor connected in series, and the high-frequency electric pulse is extracted from both ends of the resistor to measure partial discharge. A partial discharge detection impedance is attached to any one of the plurality of ground wires of the live cable, and a high frequency electric pulse generated by a partial discharge occurring in the live cable is transmitted through the partial discharge detection impedance. In a live cable partial discharge measurement method in which partial discharge is measured by taking out a live cable, a ferrite core is attached to the outer periphery of the ground wire other than the ground wire to which the partial discharge detection impedance is attached, and the partial discharge detection impedance is connected to the ground wire. It consists of a ferrite core that is provided through the wire, and a bypass circuit that is connected in series with a capacitor and a resistor that are connected in parallel to the ground wire at the ferrite core, and the high-frequency electricity is transmitted from both ends of the resistor. It is characterized by extracting pulses and measuring partial discharge.

[Function] According to claim (1), when a high-frequency electric pulse generated by a partial discharge is about to flow into a ground wire having an impedance for detecting partial discharge, the ferrite core provided in the ground wire becomes high. It shows impedance and blocks the flow. Therefore, the high-frequency electric pulse bypasses and flows to the resistor side via the capacitor, and by extracting signals from both ends of the resistor, partial discharge can be detected with high sensitivity.

If a ferrite core is provided in a grounding wire other than the grounding wire having an impedance for detecting partial discharge as in claim (2), these grounding wires exhibit high impedance to the flow of high-frequency electric pulses, and the flow is impeded. According to claim (1), the proportion of high-frequency electric pulses that are about to flow to the grounding wire having the impedance for partial discharge detection increases.
Partial discharge can be measured with even higher sensitivity.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings. Note that portions corresponding to those in FIG. 4 described above are indicated with the same reference numerals.

1 and 2 show an embodiment corresponding to claim (1). This embodiment is characterized in that the partial discharge detection impedance 5 is configured as shown in FIG. 1 to measure partial discharges. That is, this partial discharge detection impedance 5 is composed of a ferrite core 8 provided through the ground wire 4a, and a capacitor 9 and a resistor 10 connected in parallel to the ground wire 4a at the ferrite core 8. It is composed of a bypass circuit 11 connected in series. A detection signal is taken out from both ends of this resistor 10 and applied to an amplifier 7.

When such partial discharge detection impedance 5 is provided, the ferrite core 8 is a low impedance element for the commercial frequency current flowing through the ground wire 4a, so the commercial frequency current passes through the ferrite core 8 and flows to the ground side. , does not flow to the bypass circuit 11 side of the series connection of the capacitor 9 and the resistor 10.

On the other hand, since the ferrite core 8 is a high-impedance element for the high-frequency electric pulse generated by the partial current generated in the live cable 1, the high-frequency electric pulse cannot pass through the ferrite core 8, and the capacitor 9 and resistor 10 flows to the bypass circuit 11 side of the series connection. Therefore, by extracting a signal from both ends of the resistor 10, the signal extraction efficiency is increased, and partial discharge can be detected with high sensitivity.

FIG. 3 shows an embodiment corresponding to claim (2). In this embodiment, the impedance 5 for partial discharge detection provided on the ground wire 4a has the structure shown in FIG. 1 similarly to the embodiment described above, and the remaining ground wire 4
The feature is that ferrite cores 12 are attached to the outer periphery of each of b to 4e.

In this way, since each ferrite core 12 is a low impedance element for the commercial frequency current flowing through the grounding wires 4b to 4e, the commercial frequency current passes through each ferrite core 12 and flows to the ground side.

Therefore, it does not interfere with normal grounding action. - On the other hand, since each ferrite core 12 is a high impedance element for high-frequency electric pulses generated by partial discharge generated in the live cable 1, the high-frequency electric pulses cannot pass through each ferrite core 12, and the bypass circuit of the grounding wire 4a 11
It will flow only to

Therefore, according to this embodiment, partial discharge can be detected with higher sensitivity than that of the embodiment shown in FIG.

It is preferable that the ferrite cores 8 and 12 have, for example, a two-piece structure so that they can be easily attached to the grounding wires 4a to 4e.

It may be possible to use a normal coiled inductance instead of the ferrite cores 8 and 12, but using this coiled inductance would require power outage work and the connection of each grounding wire 4a to 4e to apply it to the existing live cable 1. Since cutting work and the like are required, there are problems in that it requires a great deal of time and is inconvenient to the customer side.

[Effects of the Invention] As explained above, according to the live cable partial discharge measuring method according to the present invention, the following effects can be obtained.

According to claim (1), when a high frequency pulse generated by a partial discharge flows through a ground wire provided with an impedance for partial discharge detection, the ferrite core provided in the ground wire exhibits high impedance, so that the high frequency pulse is The pulse flows to the bypass circuit side, and therefore partial discharge can be detected with high sensitivity. Furthermore, since the ferrite core exhibits low impedance to commercial frequency current, it has the advantage of not interfering with normal grounding operations.

According to claim (2), since a ferrite core is provided for each of the remaining grounding wires except for the grounding wire provided with impedance for partial discharge detection, high-frequency electric pulses are not applied to these remaining grounding wires. Instead, the current flows only through the bypass circuit of the ground line provided with an impedance for partial discharge detection, and partial discharge can be detected with even higher sensitivity. Also, in this case, each ferrite core exhibits low impedance to commercial frequency current, so there is an advantage that it does not interfere with normal grounding.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an example of impedance for partial discharge detection used in the partial discharge measuring method according to the present invention, FIG. 2 is a line configuration diagram of the embodiment of claim (1), and FIG. 2
) is a line configuration diagram of the embodiment, and FIG. 4 is a conventional line configuration diagram. DESCRIPTION OF SYMBOLS 1... Live cable, 2... Terminal part, 3... Intermediate connection part, 4a-4e... Ground wire, 5... Impedance for partial discharge detection, 8... Ferrite core, 9・・・
・Capacitor, 10... Resistor, 11... Bypass circuit, 12... Ferrite core.

Claims (2)

[Claims] (1) Attach a partial discharge detection impedance to the ground wire of the live cable, and measure partial discharge by extracting high-frequency electric pulses generated by partial discharge occurring within the live cable via the partial discharge detection impedance. In the live cable partial discharge measurement method, the impedance for partial discharge detection includes a ferrite core provided through the ground wire, and a capacitor and a resistor connected in parallel to the ground wire at the ferrite core. A method for measuring partial discharge in a live cable, characterized in that the high-frequency electric pulse is extracted from both ends of the resistor to measure partial discharge. (2) Attach an impedance for partial discharge detection to one of the grounding wires of the plurality of grounding wires of the live cable, and use the high-frequency electric pulse generated by the partial discharge generated in the live cable to detect the partial discharge. In a live cable partial discharge measurement method in which partial discharge is measured by taking it out through an impedance, a ferrite core is attached to the outer periphery of the ground wire other than the ground wire to which the impedance for partial discharge detection is attached, and The impedance is composed of a ferrite core that is provided through the ground wire, and a bypass circuit that is connected in series with a capacitor and a resistor that are connected in parallel to the ground wire at the ferrite core. A method for measuring partial discharge in a live cable, characterized in that partial discharge is measured by extracting the high-frequency electric pulse from a live cable.