TWI409473B - Partial discharge measuring method - Google Patents

Abstract

The present invention provides a detection method for a local discharge, having a well detection sensitivity to a local discharge signal. A low impedance by-path conductor (21) having a capacitor and arranged between a metal armourings (13A, 13B) connected through an insulating barrel (14) is used as a sensing loop, a local discharge current flowing into the by-path conductor (21) is detected by a high-frequency converter (30), thus it is easy to separate the local discharge signals from a commercial frequency current, moreover, a foreign noise radiated or transmitted by a space is not easy to overlap with the local discharge signals, thus the detection sensitivity may be improved.

Description

Partial discharge measurement method

The present invention relates to a partial discharge measuring method.

In the prior art, a partial discharge measurement method for measuring a partial discharge generated in a high-voltage power device is disclosed in Japanese Laid-Open Patent Publication No. Hei 7-174809. A method of partially discharging a pulse current by coupling the foil electrode to the outside of the power cable.

However, according to the conventional partial discharge measuring method, when a partial discharge is measured, since a high-impedance measuring device is used, external noise radiated from space or transmitted is easily superimposed on a partial discharge signal. Thereby, the measurement sensitivity of the partial discharge signal is lowered.

Accordingly, it is an object of the present invention to provide a partial discharge measuring method which has excellent measurement sensitivity to a partial discharge signal.

According to a feature of the present invention, a partial discharge measuring method comprises the steps of: providing a closed circuit for measuring, disposed outside an object to be measured, the closed circuit for measuring has a capacitor, wherein a frequency band for a part of the discharge The impedance system is less than the impedance for a commercial frequency; and A high frequency transformer is used to detect a partial discharge current flowing through the closed circuit for measurement.

In the above partial discharge measuring method, the closed circuit for measuring is formed by connecting a plurality of sheaths which are divided by an insulating tube provided on the outer periphery of one of the objects to be measured, so that partial discharge is performed. The current passes through the closed circuit for the measurement.

In the above partial discharge measuring method, the capacitance is formed using a foil electrode and a part of an insulator constituting the object to be measured.

In the above partial discharge measuring method, the measuring closed circuit is disposed between the object to be measured and a ground.

In the above partial discharge measuring method, the measuring closed circuit is disposed between the object to be measured and a device casing.

In the above partial discharge measuring method, the measuring closed circuit is formed by a plurality of objects to be measured connected by the capacitor.

(First embodiment)

Fig. 1 is a schematic view showing a partial discharge measuring method for carrying out the first embodiment of the present invention.

In the first embodiment, the bypass wire 21 having the capacitor 20 is connected to the outside of the power cable 10 as the object to be measured, and the partial discharge current flowing through the sensing circuit 21 formed by the bypass wire 21 is passed through the high-frequency transformer 30. , thereby determining a partial discharge signal.

The power cable 10 has a conductor 11, an insulator 12, metal sheaths 13A, 13B provided on the outer circumference of the insulator 12, and an insulating cylinder having metal sheaths 13A, 13B and provided on the outer periphery of a part of the metal sheaths 13A, 13B to be insulated. 14.

A system for determining a partial discharge signal from power cable 10 includes: a high frequency transformer 30 removably disposed in bypass conductor 21; an electro-optical converter (E/O) 50 that is connected by lead 40 and high The frequency transformer 30 is connected; a partial discharge signal processing device (PDM) 51 is connected to the electro-optical converter (E/O) 50 by the optical fiber 41 to measure a partial discharge signal; and a portable computer (PC) 52 is provided by the signal line. 42 is connected to a partial discharge signal processing device (PDM) 51; a spectrum analyzer (SPEC) is connected to a partial discharge signal processing device (PDM) 51 via a signal line 43; an oscilloscope (OSC) 54 is provided by a signal line 44. It is connected to a partial discharge signal processing device (PDM) 51 so that the frequency component and the discharge waveform of the partial discharge can be simultaneously observed.

The bypass wire 21 has two capacitors 20 between the metal sheath 13A and the metal sheath 13B, and is fixed to the surfaces of the metal sheath 13A and the metal sheath 13B by respective foil electrodes (not shown), thereby forming a low The impedance is measured using a closed circuit.

In the first embodiment, the closed circuit for low impedance measurement is a conductor 11 - insulator 12 - metal sheath 13A - bypass wire 21 - capacitor 20 - bypass wire 21 - high frequency transformer 30 - bypass wire 21 - capacitor 20-bypass wire 21 - metal sheath 13B - insulator 12 - conductor 11 is shown. Here, it is preferable to use the capacitor 20 having a capacitance of 500 pF or more. Further, it may be configured by a capacitor other than the two shown.

In general, when a partial discharge is measured using a foil electrode and a measured impedance, in order to obtain impedance matching, a measurement impedance of about 500 Ω to 1 KΩ is widely used, and a voltage generated at both ends of the impedance is measured to measure a portion. Discharge measurement. In the partial discharge measurement using such measured impedance, the high frequency signal based on the partial discharge is substantially as high as the open state impedance.

In the first embodiment, since the bypass wire 21 is fixed to the surface of the metal sheath 13A and the metal sheath 13B by the foil electrode and has the capacitance 20, the bypass wire 21 has a commercial frequency (50 Hz to 60 Hz). High impedance, when used for high frequency signals, the bypass wire 21 has a partial discharge low impedance, which is a frequency band (100 kHz to 100 MHz) of the partial discharge.

Next, the partial discharge measurement operation of the first embodiment will be described. When a partial discharge occurs in the vicinity of the insulating cylinder 14 provided on the outer circumference of the power cable 10, a pulsed partial discharge current flows from the metal sheath 13A to the bypass wire 21 having the capacitor 20. The high-frequency transformer 30 outputs a partial discharge signal generated based on a partial discharge current flowing into the bypass wire 21 to the electro-optical converter (E/O) 50 via the signal line 40.

The electro-optical converter (E/O) 50 converts the current input through the signal line 40 into an optical signal, and outputs it to the partial discharge signal processing device (PDM) 51 via the optical fiber 41. The partial discharge signal processing device (PDM) 51 measures a partial discharge based on the optical signal input via the optical fiber 41. The partial discharge signal processing device (PDM) 51 is provided by a portable computer (PC) 52 An operation signal is input to control the start (ON) and stop (OFF) of the partial discharge measurement. According to this partial discharge measurement, the frequency component contained in the measured partial discharge signal can be visually displayed and decomposed by the spectrum analyzer (SPEC) 53, and the waveform characteristics of the partial discharge can be displayed and analyzed by the oscilloscope (OSC) 54.

(Effects of the first embodiment)

According to the first embodiment described above, the low-impedance bypass wire 21 having the capacitance 20 is provided between the metal sheaths 13A and 13B connected by the insulating cylinder 14, and the portion flowing into the bypass wire 21 is measured by the high-frequency transformer 30. Discharge current. According to this configuration, the partial discharge signal can be easily separated from the background noise of the commercial frequency, and the external noise due to the spatial radiation or propagation is less likely to overlap with the partial discharge signal, so that the measurement sensitivity can be improved.

(Second embodiment)

Fig. 2 is a schematic view showing a partial discharge measuring method for carrying out a second embodiment of the present invention.

In the following description, portions having the same configurations and functions as those of the first embodiment are denoted by the same reference numerals.

The second embodiment differs from the first embodiment in that the insulating cylinder 14 disposed between the metal sheath 13A and the metal sheath 13B described in the first embodiment is protected by the metal sheath 13A and the metal sheath. The sleeve 13B is fastened to the fixed bolt 132 and the nut 133; a bypass wire 21 is provided between the foil electrode 31 and the metal sheath 13B provided on the surface of the insulation cylinder 14.

The metal sheath 13A and the metal sheath 13B each have a connecting flange 13a, The insulation barrel 14 provided between the connection flange 13a is fixed by the fastening of the bolt 132 and the nut 133. The insulating cylinder 14 is short-circuited by the bolt 132 and the nut 133, so that the impedance between the metal sheath 13A and the metal sheath 13B is almost zero.

The bypass wire 21 connects the foil electrode 31 and the metal sheath 13B, thereby forming a low-impedance closed circuit that takes out a partial discharge current flowing through the conductor 11 by the insulation barrel 14. If a partial discharge occurs in the vicinity of the insulating cylinder 14 of the power cable 10, a partial discharge current flows from the insulating cylinder 14 to the bypass conductor 21 via the foil electrode 31. The high frequency transformer 30 outputs a partial discharge signal generated by the partial discharge current flowing to the bypass wire 21 to the electric light converter (E/O) 50 via the signal line 40.

(Effect of the second embodiment)

According to the second embodiment described above, although one end of the bypass wire 21 is connected to the surface of the insulating cylinder 14 short-circuited by the bolt 132 and the nut 133 by the foil electrode 31, and the other end of the bypass wire 21 is made of metal With the sheath connection, it is still possible to use a foil electrode 31 and a part of the insulating cylinder 14 provided on the outer circumference of the power cable 10 to be an object to be measured, and according to this structure, external noise radiated or propagated from space is not easy. By overlapping with the partial discharge signal, good measurement sensitivity can be obtained.

Further, in the second embodiment, the configuration in which the other end of the bypass wire 21 is connected to the metal sheath 13B has been described, but the present invention is not limited thereto. The other end of the bypass wire 21 may also be connected to the metal sheath 13A.

(Third embodiment)

Fig. 3 is a schematic view showing a partial discharge measuring method for carrying out a third embodiment of the present invention.

The third embodiment is different from the first embodiment in that a bypass wire 21 having the capacitor 20 described in the first embodiment is provided as a ground line, and a low impedance is provided between the metal sheath 13 and the ground. Closed circuit.

The bypass wire 21 is disposed between the metal sheath 13A and the ground at an arbitrary length, thereby forming a low impedance bypass circuit.

(Effects of the third embodiment)

According to the third embodiment described above, the bypass wire 21 having the capacitor 20 is provided between the metal sheath 13 and the ground. Therefore, even in the case of the object to be measured which is a partial discharge, in the case where the metal sheath 13 cannot be directly grounded in the operation of the system, the bypass wire 21 can be safely and easily disposed, and the bypass wire 21 and the capacitor 20 are The resulting sensing loop is high impedance relative to the commercial frequency, while the relatively partially discharged high frequency signal is low impedance. Thereby, partial discharge measurement can be performed with good measurement sensitivity.

Fig. 4 is a partial schematic view showing a power cable of a variation of the third embodiment, in which a grounding wire 22 is provided between the metal sheath 13 and the ground.

As shown in the structure of FIG. 4, the high frequency transformer 30 may be provided in the ground line 22. However, if the length of the ground line 22 is too long, the impedance becomes high impedance due to the presence of the inductance, and it is difficult for the high-frequency component of the partial discharge to flow. Even in this case, the bypass lead wire 21 of the third embodiment can perform partial discharge measurement with good measurement sensitivity.

(Fourth embodiment)

Fig. 5 is a schematic view showing a partial discharge measuring method for carrying out a fourth embodiment of the present invention.

The fourth embodiment differs from the first embodiment in that it has an apparatus casing 16 as a gas insulated switchgear (GIS) as an object to be measured, and a casing 15 provided on the casing of the apparatus, and in the casing 15 The surface of the insulation 17 is provided with a foil electrode 31, and the sleeve 15 and the device casing 16 are connected by a bypass wire 21.

In the bypass wire 21, one end thereof is connected to the foil electrode 31 provided on the lower surface of the sleeve 15, and the other end is connected to the ground plate 32 provided on the upper side surface of the device casing 16. By this connection, the bypass wire 21 and the sleeve 15 are capacitively coupled, thereby forming a closed circuit which is low impedance with respect to the partially discharged high frequency signal.

(Effect of the fourth embodiment)

According to the fourth embodiment described above, in the gas insulated switchgear (GIS), a closed circuit of a low impedance based on capacitive coupling is provided in the same manner as a measurement target such as a power cable and a power cable end portion (box). According to this configuration, it is possible to perform partial discharge measurement with excellent measurement sensitivity as compared with the partial discharge measurement method in the conventional insulated connection portion of the power cable using the capacitance to the ground.

Further, in the fourth embodiment, the configuration of the low-impedance closed circuit for measuring the partial discharge in the gas insulated switchgear has been described. However, the present invention is not limited thereto. For example, a partial discharge can be similarly measured in the air terminal portion (tank) of the transformer or the like.

(Fifth Embodiment)

Fig. 6 is a schematic view showing a partial discharge measuring method for carrying out a fifth embodiment of the present invention.

The fifth embodiment is different from the fourth embodiment in that the bypass wire 21 described in the fourth embodiment is disposed between two objects to be measured, and the waiting measurement object is enabled by the same power source. The relative two-phase bushing 15 described in the fourth embodiment is taken out from the bypass wire 21 by the high-frequency transformer 30.

The two-phase bushing is a sleeve made up of a pair of wires. For example, the R phase insulation 17A and the R phase insulation 17B are provided, and the lower metal member 18A which is the base of the insulation 17A and the lower metal member 18B which is the base of the insulation 17B are connected by the bypass wire 21 having the two capacitors 20. The upper metal member 170 of the insulating 17A and the upper portion of the upper metal member 171 of the insulating 17B are connected by a connecting wire 19, thereby forming a closed loop of low impedance. Further, in the fifth embodiment, the configuration in which the R-phase bushings are connected to each other by the connection line 19 connecting the same phases has been described. However, the present invention is not limited thereto. For example, the objects to be measured between the T phase or the S phase may be connected to each other.

(Effects of the fifth embodiment)

According to the fifth embodiment described above, since the low-impedance closed circuit is provided by the bypass wire 21 disposed between the objects of the two cables of the same phase, the measurement sensitivity is excellent, and a single cable can be used. The lower partial discharge measurement is a more efficient partial discharge measurement. When a partial discharge occurs, the source of the signal can be grasped by using a partial discharge measuring device (PDM) 51 to grasp the source of the signal. Which cable is on.

(Sixth embodiment)

Fig. 7 is a schematic view showing a partial discharge measuring method for carrying out a sixth embodiment of the present invention.

The sixth embodiment differs from the fifth embodiment in that the configuration of the bypass conductor 21 in which the two-phase connection is applied by applying the same power source and having the same phase, which is described in the fifth embodiment, is applied. The power cables 10A and 10B are divided by the insulating cylinders 14A and 14B.

In the power cable 10A, the metal sheath 130A and the metal sheath 130B are divided by the insulating cylinder 14A. In the power cable 10B, the metal sheath 131A and the metal sheath 131B are divided by the insulating cylinder 14B. A bypass wire 21A is disposed between the metal sheath 130A and the metal sheath 131A, and a bypass wire 21B is disposed between the metal sheath 130B and the metal sheath 131B. Further, the bypass wire 21A and the bypass wire 21B are connected by a short-circuiting wire 22 constituting a part of the bypass wire, and the high-frequency transformer 30 is provided in the short-circuiting wire 22. The connecting wire 19 connects the two conductors 11A (for example, the R phase).

(Effects of the sixth embodiment)

According to the sixth embodiment described above, even in the case of two cables of the same phase divided by the insulating cylinder, partial discharge measurement with excellent measurement sensitivity and partial discharge measurement with a single cable can be performed in the same manner as in the fifth embodiment. More efficient than that.

(Other embodiments)

Further, the present invention is not limited to the above embodiment, and does not deviate or change. Various modifications can be made within the scope of the technical idea of the present invention. For example, for a metal sheath, the surface can also be covered with a rustproof layer.

10‧‧‧Power cable

11‧‧‧Conductor

12‧‧‧Insulator

13, 13A, 13B, 130A, 130B, 131A, 131B‧‧‧ metal sheath

13a‧‧‧Connection flange

14, 14A, 14B‧‧‧Insulation cylinder

15‧‧‧ casing

16‧‧‧Device housing

17, 17A, 17B‧‧‧Insulation

18A, 18B‧‧‧ base

19‧‧‧Connecting line

20‧‧‧ Capacitance

21, 21A, 21B‧‧‧ Bypass wire

22‧‧‧Short wire

30‧‧‧High frequency transformer

31‧‧‧Foil electrodes

40, 42, 43, 44‧‧‧ leads

41‧‧‧Fiber

51‧‧‧Partial discharge measuring device (PDM)

52‧‧‧ Laptop (PC)

53‧‧‧Spectrum Analyzer (SPEC)

54‧‧‧Oscilloscope (OSC)

132‧‧‧Bolts

133‧‧‧ nuts

170‧‧‧Upper metal parts

171‧‧‧Upper metal parts

Fig. 1 is a schematic view showing a partial discharge measuring method for carrying out the first embodiment of the present invention.

Fig. 2 is a schematic view showing a partial discharge measuring method for carrying out a second embodiment of the present invention.

Fig. 3 is a schematic view showing a partial discharge measuring method for carrying out a third embodiment of the present invention.

Figure 4 is a partial schematic view of a power cable with a grounding wire between the metal sheath and ground.

Fig. 5 is a schematic view showing a partial discharge measuring method for carrying out a fourth embodiment of the present invention.

Fig. 6 is a schematic view showing a partial discharge measuring method for carrying out a fifth embodiment of the present invention.

Fig. 7 is a schematic view showing a partial discharge measuring method for carrying out a sixth embodiment of the present invention.

10‧‧‧Power cable

11‧‧‧Conductor

12‧‧‧Insulator

13, 13A, 13B‧‧‧ metal sheath

13a‧‧‧Connection flange

14‧‧‧Insulation cylinder

21‧‧‧ Bypass wire

30‧‧‧High frequency transformer

40, 42, 43, 44‧‧‧ leads

41‧‧‧Fiber

51‧‧‧Partial discharge measuring device (PDM)

52‧‧‧ Laptop (PC)

53‧‧‧Spectrum Analyzer (SPEC)

54‧‧‧Oscilloscope (OSC)

132‧‧‧Bolts

133‧‧‧ nuts

Claims (5)

A partial discharge measuring method comprising the steps of: setting a closed circuit for measuring to an outside of an object to be measured, wherein an impedance of the measuring circuit in a frequency band of partial discharge is smaller than a closed circuit for measuring An impedance at a commercial frequency; and detecting a partial discharge current flowing through the closed circuit for measurement using a high frequency transformer; and the measurement object is a power cable having: a conductor disposed on an outer circumference of the conductor An insulator, a metal sheath A and B disposed on the outer circumference of the insulator via an insulating cylinder, and a foil electrode is disposed on a surface of each of the metal sheaths A and B, and is disposed upstream of the high frequency transformer The capacitors on the side and the downstream side are connected by wires to form the closed circuit for measurement to detect partial discharge. A partial discharge measuring method comprising the steps of: setting a closed circuit for measuring to an outside of an object to be measured, wherein an impedance of the measuring circuit in a frequency band of partial discharge is smaller than a closed circuit for measuring The impedance at the commercial frequency; and using a high frequency transformer to detect a partial discharge current flowing through the closed circuit for the measurement; and the measured object is a power cable having: a conductor, An insulator disposed on an outer circumference of the conductor, and metal sheaths A and B disposed on an outer circumference of the insulator via an insulating cylinder to electrically connect the metal sheaths A and B, and the metal sheath is fixed by a metal member An insulating cylinder having a foil electrode on a surface thereof, and one of the metal sheaths A and B is connected by a wire via the high-frequency transformer, thereby forming the closed circuit for measuring to detect a partial discharge . A partial discharge measuring method comprising the steps of: setting a closed circuit for measuring to an outside of an object to be measured, wherein an impedance of the measuring circuit in a frequency band of partial discharge is smaller than a closed circuit for measuring The impedance at the commercial frequency; and detecting a partial discharge current flowing through the closed circuit for measuring by using a high frequency transformer; and the measuring object is a gas insulated opening and closing device having a device casing and disposed thereon a sleeve on the outer casing of the device, through which a foil electrode disposed on a lower surface of the sleeve is electrically connected to a ground plate disposed on an upper side of the outer casing of the device, thereby forming the measurement Close the circuit to detect partial discharge. A method for measuring a partial discharge, comprising the steps of: setting a closed circuit for measuring to an outside of an object to be measured, wherein the impedance of the closed circuit at a frequency band of the partial discharge is smaller than the Determining the impedance of the closed circuit at a commercial frequency; and detecting a partial discharge current flowing through the closed circuit for measurement using a high frequency transformer; and the measured object is in-phase two gas insulated with the same power source enabled An opening and closing device, the two gas insulated opening and closing devices respectively have a device casing and a sleeve disposed on the casing of the device, and the two gas insulated opening and closing devices are connected by connecting lines connecting the upper metal parts of the sleeves to each other The capacitors are connected between the lower metal parts of the sleeve of the two gas insulated switchgear by means of the high-frequency transformers, thereby forming the closed circuit for measuring to detect partial discharge. A partial discharge measuring method comprising the steps of: setting a closed circuit for measuring to an outside of an object to be measured, wherein an impedance of the measuring circuit in a frequency band of partial discharge is smaller than a closed circuit for measuring The impedance at the commercial frequency; and the use of a high frequency transformer to detect a partial discharge current flowing through the closed circuit for the measurement; and the measured object is an in-phase two power cable, the two power cables respectively having: a conductor, a setting An insulator on the outer circumference of the conductor, and metal sheaths A and B disposed on the outer circumference of the insulator via an insulating cylinder, and the conductor portions of the two power cables are connected by a connecting line. Two metal sheaths A of the two power cables are connected by wires, and two metal sheaths B of the two power cables are connected by wires, and a short circuit having a capacitor and the high frequency transformer is disposed between the wires Thereby, the closed circuit for measurement is formed to detect a partial discharge.