JPH0718908B2 - Insulation test equipment for power cables - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a power cable insulation test apparatus, and more specifically, to adapt a DC leakage current detection impedance and a partial discharge detection impedance to a type of the cable. The present invention relates to an insulation test device that can be set remotely from a monitor unit.

TECHNICAL BACKGROUND OF THE INVENTION Devices for simultaneously measuring DC leakage current and partial discharge of a power cable are known. However, in this type of conventional device, when simultaneously measuring the DC leakage current and the partial discharge, the DC leakage current detection impedance and the partial discharge detection impedance are individually set in advance so as to match the type of the cable. However, there is a problem that the impedance selection and the circuit connection are complicated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the conventional device, and enables the DC leakage current detection impedance and the partial discharge detection impedance to be remotely set from a monitor unit so as to match the type of cable. An object of the present invention is to provide a power cable insulation test apparatus capable of simultaneously measuring DC leakage current and partial discharge with extremely high accuracy.

[Summary of the Invention] In order to achieve the above object, the present invention comprises a sensor section and a monitor section connected to the sensor section. The sensor section is provided with a high DC voltage at one end and a cable to be measured at the other end. A DC leakage current detection impedance that is connected and can select a plurality of impedance values, and a partial discharge detection impedance that is connected in parallel to the DC leakage current detection impedance via a high-frequency filter and that can select a plurality of impedance values , The monitor unit displays the output contents of the detection signal appearing at each end of the DC leakage current detection impedance and the partial discharge detection impedance, and the impedance value of the DC leakage current detection impedance and the partial discharge detection impedance. Selection signal generator that generates an impedance value selection signal for selecting It is provided with steps.

Embodiments of the Invention Embodiments of the present invention will be described below with reference to the drawings.

The power cable insulation test apparatus according to the present invention, as shown in FIG. 1 as one embodiment thereof, includes a sensor section 20 arranged in the vicinity of the head section of the cable to be measured 10 and a monitor arranged on the ground. Section 40 and the optical fibers 90A, 9 connecting between them
It consists of 0B and 90C.

The sensor unit 20 includes a case 21 to which the DC high-voltage generator 60 and the power cable 70 of the other phase functioning as the coupling capacitor C are connected, and in this case, for example, six kinds of impedance values are provided by a selection signal described later. DC leakage current detection impedance 22 configured to be selectable,
A partial discharge detection impedance 23 is arranged so that, for example, two kinds of impedance values can be selected by the selection signal, that is, the control signal.

The DC leakage current detecting impedance 22 is interposed between the cable to be measured 10 and the case 21, and the voltage between its terminals is applied to the amplifier 24. An A / D converter 25 and an electro-optical converter (hereinafter abbreviated as E / O converter) 26 are sequentially connected to the amplifier 24, and the optical fiber 90B is provided at the output end of the E / O converter. The beginning of is connected.

On the other hand, the partial discharge detection impedance 23 is connected to the DC leakage current detection impedance 22 via the high frequency filter 27.
Are connected in parallel. Then, to the detection impedance 23, an amplifier 28 for amplifying the detection signal and an E / O converter 29 are sequentially connected, and the output end of the E / O converter 29 is connected to the start end of the optical fiber 90A. There is.

The control signal input terminal of each of the detection impedances 22 and 23 has an opto-electric converter (hereinafter abbreviated as O / E converter) 3
The output end of 0 is connected, and the input end of the O / E converter 30 is connected to the start end of the optical fiber 90C.

The conductive jackets (sheath) 10a and 70a of the measured cable 10 and the power cable 70 of the other phase are both grounded.

The monitor unit 40 displays an O / E converter 41 in which the end of the optical fiber 90B is connected to the input end, and an ammeter connected to the O / E converter 41 via the D / A converter 42. Instrument 43 and recorder 44,
O / E converter 45 with the end of optical fiber 90A connected to the input end
And a counter 46 connected to this O / E converter 45 and an indicator for displaying the count value of the oscilloscope 47 and counter 46.
48, a selection switch 49 for individually selecting the impedance values of the detection impedances 22 and 23, and this switch
It is provided with a selection signal generator 50 for generating an impedance value selection signal according to the contact position of 49, and an E / O converter 51 for converting the control signal into an optical signal and applying it to the optical fiber 90C.

The operation of this embodiment will be described below. Above sensor case
When the DC high voltage generator 60 is connected to 21, the measured cable
Detection impedance 22 between the inner conductor of 10 and the sheath 10a
A high voltage is applied via. Therefore the cable 10
If the insulator is deteriorated, a DC leakage current flows through the insulator, and this leakage current causes a terminal voltage corresponding to the detection impedance 22.

At this time, since the high-pass filter 27 is connected to the cable-side terminal of the partial discharge detection impedance 23, the leakage current that is a direct current does not flow into the partial discharge detection impedance 23, and the partial discharge detection impedance 23 will be described later. Only the pulse passes through.

Then, after the terminal voltage is amplified by the amplifier 24,
It is converted into a digital signal by the A / D converter 25, further converted into a corresponding optical signal by the E / O converter 26, and added to the optical fiber 90B.

In the monitor unit 40, the optical signal indicating the DC leakage current transmitted through the optical fiber 90B is converted into an electric signal by the O / E converter 41, and converted into an analog electric signal by the D / A converter 42. . Then, the value of the analog electric signal, that is, the magnitude of the DC leakage current is displayed on the display 43 and recorded on the recorder 44.

Next, when the so-called partial discharge occurs due to the insulation deterioration of the cable 10 to be measured, and a partial discharge pulse is generated accordingly, the first wave of this pulse is the head portion of the cable 10 → high-pass filter 27 → detection impedance 23 → Sensor case 21
→ Cable 70 → It flows through the path of the sheath 70a of the cable. Further, the second wave of the partial discharge pulse, which has been reflected at the far end of the cable 10 and then reached the head of the cable, and the reflected wave of the head of the first wave propagates to the far end. The third wave reflected at the far end and propagated to the head also flows through the same path.

Therefore, as shown in FIG. 2, signals showing the first, second, and third waves of the pulse appear between both ends of the detection impedance 23, and these signals are amplified by the amplifier 28 and E / After being converted into a corresponding optical signal by the O converter 29, it is added to the optical fiber 90A.

In the monitor unit 40, the signals indicative of the first, second and third waves transmitted through the optical fiber 90A are converted into electric signals by the O / E converter 45, and these signals are counted by the pulse counter 46. And is displayed on the oscilloscope 47 in the manner shown in FIG. Therefore, the occurrence of partial discharge can be known from the display contents of the oscilloscope 47 and the pulse number display 48.

The counter 46 counts only pulse signals having a value equal to or larger than a value at a predetermined time. The distance X from the head portion of the cable 10 to be measured to the position where the partial discharge occurs is given by the following equation.

However, V _p : pulse propagation velocity l: length of the cable 10 T: time between the first and second waves By the way, depending on the type of the cable 10 to be measured, the values of the detection impedances 22 and 23 may be changed to change the sensor. It is desirable to adjust the detection sensitivity of the section 20. In this embodiment, by operating the impedance selection switch 49, an impedance value selection signal corresponding to the operated position is output from the signal generator 50, and this signal is the E / O converter 51, the optical fibers 90C and O /. It is applied to each of the detection impedances 22 and 23 via the E converter 30. Therefore, the impedance values of those detection impedances 22 and 23 are
It can be set remotely from the monitor unit 40 side so as to suit 10 types.

In this embodiment which operates as described above, the signal based on the partial discharge is transmitted through the optical fiber 90C into which the inductive noise is not mixed, so that the accurate partial discharge can be measured.

In the above embodiment, the cable 70 of the other phase is made to function as a coupling capacitor, but of course a dedicated capacitor may be interposed between the sensor case 21 and the sheath of the cable 10.

In addition, the output of the O / E converter 45 is added to a digital memory (not shown) to store the first wave, the second wave, and the third wave in the memory, and the above formula is shown based on the stored contents of this memory. The distance X can be calculated by a microcomputer (not shown).

EFFECTS OF THE INVENTION According to the present invention, the values of the DC leakage current detection impedance and the partial discharge detection impedance can be remotely set by operating the impedance selection switch from the monitor unit according to the type of the cable under test. It is easy to set both impedances, and the detection sensitivity of the sensor unit can be adjusted.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an insulation test apparatus for a power cable according to the present invention, and FIG. 2 is a waveform diagram illustrating first, second and third waves of a partial discharge pulse. 10 …… Cable to be measured 10a …… Sheath 20 …… Sensor 21 …… Case 22 …… DC leakage current detection impedance 23 …… Partial discharge detection impedance 26,29 …… E / O converter 27 …… High Filter 40 …… Monitor section 41,45 …… O / E converter 43 …… Display 44 …… Recorder 46 …… Pulse counter 47 …… Oscilloscope 48 …… Pulse number display 49 …… Selection switch 50… … Selection signal generator 51 …… E / O converter 60 …… DC high voltage generator 70 …… Other-phase cables 90A to 90C …… Optical fiber

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasutaka Fujiwara 2-1-1 1-1 Oda Sakae, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Showa Electric Wire & Cable Co., Ltd. 2-1-1 No. 1 Showa Cable Electric Co., Ltd. (72) Inventor Akira Nagaoka 2-1-1 1-1 Oda Sakae, Kawasaki-ku, Kawasaki-shi, Kanagawa Kanagawa Prefecture (56) Reference: JP-A-57-189074 (JP, A) JP 59-168377 (JP, A) JP 59-202076 (JP, A)

Claims (1)

[Claims] 1. A sensor section and a monitor section connected to the sensor section, wherein a high DC voltage is applied to one end and a cable to be measured is connected to the other end of the sensor section to select a plurality of impedance values. DC leakage current detection impedance that can be, and a partial discharge detection impedance that is connected in parallel to the DC leakage current detection impedance via a high frequency filter and a plurality of impedance values can be selected, the monitor unit, Display means for displaying the output contents of the detection signal appearing at each end of the DC leakage current detection impedance and the partial discharge detection impedance, and the impedance values of the DC leakage current detection impedance and the partial discharge detection impedance, respectively. Selection signal for generating impedance value selection signal for selection Insulation test device for a power cable, characterized in that a raw device.