JPS6150262B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for accurately measuring surface leakage current from a main circuit cable.

A conventional device of this type is shown in FIG. Moreover, FIG. 2 shows the measurement method. In the figure, 1 is the box of the closed switchboard, 2 is the door, 3 is the bridge or disconnector, 4 is the bus bar, 5 is the instrument current transformer, 6 is the conductor, 7 is the support insulator, 8 is the voltage application terminal, and 9 is the bus bar. A main circuit cable, 10 a hook rod for voltage application, 11 a switch, 12 a DC power supply, and 13 an ammeter.

Measurement using the conventional apparatus configured as described above will be explained. When a hook rod 10 is hooked onto a voltage application terminal 8 from the rear of the box 1 and a high DC voltage is applied by a DC power source 12, a leakage current is generated from the cable surface and its value is indicated on an ammeter 13. At this time, the shield breaker 3 must be turned off.

Since the conventional DC leakage current measurement is performed as described above, as shown in FIG. Various miscellaneous leakage currents, such as currents leaking from the surface of the internal insulator, also flowed into the ammeter 13, resulting in a major drawback in that only the cable leakage current could not be accurately measured.

This invention was made to eliminate the drawbacks of the conventional ones as described above, and includes a disconnector that cuts off electrical continuity between the main circuit cable and the equipment inside the panel;
A support insulator that has a conductive part in the center and supports the main circuit cable while being insulated from the panel body, and a DC voltage is applied and current flows between one end of the main circuit cable and the other end whose outer surface is grounded. It is an object of the present invention to provide a DC leakage current measuring device that can accurately measure DC leakage current by including a measurement circuit that measures the current and a bypass circuit that is connected to the conductive part and the measurement circuit.

An embodiment of the present invention will be described below with reference to the drawings. In Figures 3 and 4, the box body 1, door 2, breaker 3, bus bar 4, instrument current transformer 5, conductor 6, voltage application terminal 8, main circuit cable 9, voltage application hook bar 10, switch 11, DC power supply 12
The ammeter 13 is the same as the conventional one. 14 is a double structure insulator with a conductive part 14 in the center.
It has a. 15 is a disconnector, 16 is its operating function, and 17 is a shielded wire forming a bypass circuit.

Next, measurement in an embodiment of the present invention configured as described above will be explained. First, turn off the disconnector 3, operate the operation function 16, and turn off the disconnector 1.
5 is opened. Thereby, the instrument current transformer 5 and the shingle breaker 3 do not affect the main circuit cable 9. Next, a bypass circuit 17 is formed using the shield wire 7 to return leakage current flowing through the insulator 14 from the conductive portion 14a of the double structure insulator 14 to the power source. Finally, when the hook rod 10 is hooked onto the voltage application terminal 8 and the switch 11 is turned on to apply a high DC voltage, the current leaking only from the cable surface flows to the ammeter 13, allowing accurate measurement of the leakage current.

In the above embodiment, the leakage current of the main circuit cable was measured, but the pure leakage current of other main circuit devices can be measured by using the same type of equipment.

As described above, according to the present invention, the disconnector has a conductive part in the center of the disconnector that cuts electrical continuity between the main circuit cable and the equipment inside the panel, and insulates the main circuit cable from the panel. A supporting insulator to support, a measuring circuit that applies a DC voltage to one end of the main circuit cable and the other end whose outer surface is grounded and measures the flowing current, and is connected to the conductive part and the measuring circuit. By including the bypass circuit, it is possible to provide a DC leakage current measuring device that can accurately measure DC leakage current.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a conventional closed power distribution board, and FIG. 2 shows measurement of DC leakage current in the conventional closed power distribution board. FIG. 3 is a side sectional view of a closed switchboard according to an embodiment of the present invention, FIG. 4 is a diagram showing measurement of DC leakage current in a closed switchboard according to an embodiment of the present invention, and FIG. FIG. 6 is a diagram showing a current leakage state of a double structure insulator used in an embodiment of the present invention. In the figure, 1... box of closed switchboard, 9...
Main circuit cable, 12...DC power supply, 13...Ammeter, 14...Double structure insulator, 15...Disconnector,
17...This is a bypass circuit. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A disconnector that breaks electrical continuity between the main circuit cable and the equipment inside the panel, a support insulator that has a conductive part in the center and supports the main circuit cable while insulating it from the panel, and the main circuit. A measuring circuit that applies a DC voltage to one end of the cable and the other end whose outer surface is grounded and measures the flowing current, and a bypass circuit that is connected to the conductive part and the measuring circuit. DC leakage current measuring device.