JPH067148B2 - Partial discharge measurement method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for measuring partial discharge in an insulation connection portion of a power cable line.

[Conventional technology]

FIG. 4 (a) shows a conventional partial discharge measuring method. A power cable 21 is connected via an insulating connection portion 20, and terminal connection portions 22 are provided at both ends. The terminal connection part 22 is provided with a high-voltage charging terminal 23, and the metal sheath in the vicinity of the insulating connection part 20 is grounded via the detection impedance 6. A measuring instrument 7 is connected to detect the potential difference across the detection impedance 6. Incidentally, C _K is a coupling capacitor.

With the above configuration, a high voltage is applied to the high voltage applying terminal 23. When a partial discharge occurs in the insulator in this state, a high frequency pulse is induced in the conductor and the metal sheath, the high frequency pulse of the metal sheath flows into the detection impedance 6, and a potential difference proportional to the magnitude of the high frequency pulse is generated at both ends thereof. . The partial discharge is measured by detecting the potential difference by the measuring device 7.

When calibrating the measurement sensitivity of the measuring device 7, the high voltage charging of the high voltage terminal 23 is stopped, and the calibration signal generator 8 is connected to the termination connecting portion 11.
A high frequency pulse for calibration is applied between the conductor of the power cable 21 and the metal sheath by connecting to the vicinity of. The equivalent circuit is shown in Fig. 4 (b). As shown in FIG. 4, the calibration signal generator 8 applies a high frequency pulse of V _Q volts between the conductor 10 of the power cable 21 and the metal sheath 12 via a capacitor of capacitance C _Q. Capacitance C between the conductor 10 and the metal sheath 12
Is formed and the high-frequency pulse that has flowed through the capacitor of electrostatic capacitance C is shunted to the detection impedance 6. In this way, the sensitivity of the measuring device 7 is calibrated. Where capacitance C
Let Q be the apparent discharge charge of the capacitor and V ₁ be the potential difference: Q = V _Q · C _Q = V ₁ · C (1) From equation (1), Is obtained. Even if the detection impedance is connected between the metal sheaths on both sides of the insulating cylinder of the insulating connection portion 20, substantially the same effect can be obtained.

[Problems to be Solved by the Invention]

However, according to the conventional partial discharge measurement method, when the power cable line becomes long, such as several Km, its level V _Q is attenuated until a high-frequency pulse for calibration is transmitted to the partial discharge measurement position. In addition, since C >> C _Q is normally satisfied, the value of V _{1 in} the equation (2) becomes small, and there is an inconvenience that a predetermined calibration operation cannot be performed. Further, there is a disadvantage that the workability is poor because the position of the terminal end connecting the calibration signal generator is far from the position of the measuring point for performing the calibration operation.

Therefore, an object of the present invention is to provide a partial discharge measurement method capable of obtaining a predetermined level of calibration signal.

Another object of the present invention is to provide a partial discharge measuring method which improves the workability of the calibration operation.

[Means for Solving the Problems]

In order to achieve the above object, the present invention provides a pair of detection electrodes for electrostatic coupling in the vicinity of the outer surface of the anticorrosion layer of an insulating connection part with an insulating tube interposed therebetween, and a partial discharge is generated between the pair of detection electrodes. Connect the detection impedance to which the measuring instrument to be connected is connected, connect the calibration pulse generator in parallel to the detection impedance, and by the calibration pulse output from the calibration pulse generator,
There is provided a partial discharge measuring method characterized in that a measuring instrument is calibrated, and a potential difference generated at both ends of a detection impedance based on a high frequency pulse is measured by the measuring instrument.

Further, the present invention provides a pair of detection electrodes for electrostatic coupling with an insulating tube sandwiched between the outer surface of the anticorrosion layer of the insulation connection part, and a measuring device for measuring partial discharge is connected between the pair of detection electrodes. Connected to the detection impedance, and adjacent to the outer surface of the anticorrosion layer of the insulation connection, the calibration electrode of a pair of measuring instruments for electrostatic coupling is adjacent to a pair of detection electrodes that are provided with a connection tube in between. The calibration pulse generator is connected to the pair of calibration electrodes, and the calibration pulse output from the calibration pulse generator
There is provided a partial discharge measuring method characterized in that a measuring instrument is calibrated, and a potential difference generated at both ends of a detection impedance based on a high frequency pulse is measured by the measuring instrument.

〔Example〕

 Hereinafter, the partial discharge measuring method of the present invention will be described in detail.

FIG. 1 shows an embodiment of the present invention, in which an anticorrosion vinyl layer 1 on a metal sheath and an anticorrosion vinyl layer 2 on a metal body tube of an insulating connection part
Are continuous, and the metal barrel is insulated by the insulating cylinder 3. A pair of detection electrodes 4 and a pair of calibration electrodes 5 are provided on the outer surface of the anticorrosion vinyl layer 2 on the metal barrel, and the detection impedance 6 and the calibration signal generator 8 are connected in parallel to these electrodes 4, 5. Are connected to.
A measuring instrument 7 is connected to the detection impedance 6 and detects the potential difference between both ends thereof.

FIG. 2 is a circuit diagram showing the embodiment of FIG.
The conductor 10 of the power cable is connected by a connection sleeve 11, capacitors of electrostatic capacitances C ₁ and C ₂ are formed between the conductor 10 and the metal barrel 12, and the metal barrel 12 is insulated by the insulating tube 3. . A detection electrode 4 and a calibration electrode 5 are provided on the outer surface of the anticorrosion vinyl layer 2 on the metal barrel 12.
The detection impedance 6, the measuring device 7, and the calibration signal generator 5 are as shown in FIG.

FIG. 3 (a) is an equivalent circuit of FIG. 2, and the same parts are indicated by the same reference numerals, and thus duplicated description will be omitted. However, the detection electrodes 4 cause the capacitors having electrostatic capacitances C _d1 and C _{d2 to be} omitted. ,
The calibration electrode 5 forms capacitors having electrostatic capacities C _P1 and C _P2 . Where C _P1 , C _P2 >> C _Q , Therefore, the equivalent circuit of FIG. 3 (b) is obtained. In this equivalent circuit, C ₁ = C ₂ , The voltage V ₂ applied across the detection impedance 6 is _{Here, C Q, C 1, C} 2, V Q are known, or can be measured. Comparing the equation (2) explained in the prior art with the equation (3) of the present invention, V ₂ = 2V ₁ (4) However, C = C ₁ . As is clear from the equation (4), the high frequency pulse is detected at a level twice as high as that in the conventional case, and it is not necessary to consider the attenuation caused by propagating through the long power cable.

In the foregoing embodiments, although the _{C P1, C P2 »C Q,} C Q
Is about 10 to 50 PF, and in order to satisfy this, the area of the calibration electrode 5 can be set to a predetermined value to be about 500 to 1000 PF. The same _{applies to} Z _cd1 , Z _cd2 >> Z.

When the calibration electrode 5 is omitted and a calibration signal is injected into the detection electrode 4, C in the equivalent circuit of FIG. 3 (a) is used.
_{Since P1} and C _P2 are omitted, the circuit becomes the same as the equivalent circuit of FIG. 3 (b). However, in order to increase the calibration accuracy, it is better to provide the calibration electrode 5.

Furthermore, although C ₁ = C ₂ and Z >> Z _c1 have been described as conditions, even if these conditions are not satisfied, calibration is possible by obtaining the correction term based on the basic equation.

〔The invention's effect〕

As described above, according to the partial discharge measuring method of the present invention, the predetermined detection electrode is provided on the metal body tube of the insulation connection portion via the anticorrosion layer, and the detection impedance and the calibration signal generator are connected in parallel therebetween. Since it is inserted as described above, the following effects can be obtained.

(1) Partial discharge can be measured with a predetermined sensitivity at the insulation connection part of a long cable line. In addition, it can be applied as is to existing lines.

(2) The distortion or attenuation of the waveform of the high frequency pulse for calibration does not occur.

(3) Since the calibration signal generator and the measuring instrument are in the same position,
Good workability.

(4) The safety is high because it is not necessary to inject a high frequency pulse for calibration into the high voltage conductor.

(5) Sensitivity can be calibrated even in a live state.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of the present invention. Figure 2 shows the first
The circuit-like explanatory drawing of a figure. 3 (a) and 3 (b) are equivalent circuit diagrams of FIG. 2, and FIGS. 4 (a) and 4 (b) are explanatory diagrams and equivalent circuit diagrams of a conventional partial discharge measuring method. Explanation of symbols 1 …… Anti-corrosion vinyl layer on metal sheath 2 …… Anti-corrosion vinyl layer on metal barrel 3 …… Insulation cylinder 4 …… Detection electrode 5 …… Calibration electrode 6 …… Detection impedance 7 …… Measurement Instrument, 8 ... Calibration signal generator 10 ... Cable conductor, 11 ... End sleeve 12 ... Metal barrel

Claims (2)

[Claims] 1. A method for measuring partial discharge in an insulation connection portion of a power cable line, wherein a pair of detection electrodes for electrostatic coupling are provided near an outer surface of an anticorrosion layer of the insulation connection portion with an insulating cylinder interposed therebetween. A measuring impedance is connected between the measuring electrodes for measuring the partial discharge, a calibration pulse generator is connected in parallel with the detecting impedance, and a calibration pulse is output from the calibration pulse generator. A partial discharge measuring method, characterized in that the measuring device is calibrated, and a potential difference generated at both ends of the detection impedance based on a high frequency pulse is measured by the measuring device. 2. A method for measuring a partial discharge in an insulation connection portion of a power cable line, wherein a pair of detection electrodes for electrostatic coupling are provided near the outer surface of the anticorrosion layer of the insulation connection portion with an insulating cylinder interposed therebetween. A detection impedance is connected to which a measuring device for measuring partial discharge is connected between the detection electrodes, and the pair of detection electrodes provided with the connection tube interposed therebetween near the outer surface of the anticorrosion layer of the insulating connection part. A pair of calibration electrodes of the measuring device for electrostatic coupling is provided adjacent to, a calibration pulse generator is connected to the pair of calibration electrodes, and the calibration pulse is output from the calibration pulse generator. A partial discharge measuring method comprising calibrating a measuring instrument, and measuring a potential difference generated at both ends of the detection impedance based on a high frequency pulse by the measuring instrument.