JP3096070B2 - Partial discharge measuring part in prefabricated connection part for power cable and partial discharge measuring method using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a partial discharge measuring section in a prefabricated connection section for a power cable capable of performing accurate partial discharge measurement and a partial discharge measuring method using the same.

[0002]

2. Description of the Related Art In a connection portion of a power cable, particularly a so-called prefab joint portion which has been frequently used in recent years,
An accurate insulation test at the interface of a reinforced insulator is desired.
As a method of the insulation test, a partial discharge test method has been conventionally known. However, there is a problem that a test operation such as inserting a detection circuit into a line after installation is troublesome, and recently, as shown in FIG. Various methods have been proposed.

[0003] This method applied to the cable insulated connection 1 is, as shown in FIG. 3, provided on the outer periphery of the reinforcing insulator 3 around the conductor connection 2, the left and right extending from the metal sheath 4 of the power cable on both sides. Are connected to each other by an insulating cylinder 6 to insulate them from each other, and their surroundings are covered with an anticorrosion layer 7. The foil electrodes 8a and 8b having a capacitance between the anticorrosion layer 7 on both sides of the insulating cylinder 6 and the connection conduits 5 present below each are attached, and the potential difference induced between the foil electrodes 8a and 8b. Is detected by the resistor 9,
In particular, it is possible to measure a partial discharge without interposing a circuit.

[0004]

However, in the above-described method, since the potential difference between the connection pipes 5 partitioned in the longitudinal direction is detected, the external noise induced in the line or the like is measured at once. As a result, when the partial discharge signal is weak, it is very difficult to accurately detect it. Further, these measurement methods are intended to evaluate the entire line of the line, and it is difficult to detect a specific portion such as an interface of a reinforcing insulator.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to measure a partial discharge in a prefabricated connection portion for a power cable capable of accurately measuring a partial discharge generated in a specific portion without being affected by external noise. An object of the present invention is to provide a partial discharge measurement method using the same.

[0006]

In order to achieve the above-mentioned object, a partial discharge measuring section in a prefabricated connection section for a power cable according to the present invention comprises a pre-mold insulator, a semi-conductor, and a pre-mold insulation reinforcement. A prefabricated connecting portion, in which a body, two annular electrodes, an insulating tape layer, and a grounded conductive layer are sequentially laminated from the inside in a longitudinal direction, a cable insulating layer near a connecting portion between conductors of a power cable. And a detection signal line extending from each of the annular electrodes.

[0007] Similarly, in the method for measuring partial discharge in a prefabricated connection portion for a power cable according to the present invention, a pre-molded insulator and a semi-conductor, a pre-molded insulation reinforcing member, and a pre-molded insulator which are spaced apart in the longitudinal direction are arranged. A plurality of annular electrodes, an insulating tape layer, and a prefabricated connection portion in which grounded conductive layers are sequentially laminated from the inside, are attached on a cable insulating layer near a connection portion between conductors of a power cable, and each of the annular electrodes is A detection signal line is drawn out, a detection impedance is interposed between the conductive layer and each of the detection electrodes, and an in-phase signal is removed by obtaining two detection signals obtained differentially to remove a partial discharge signal. It is characterized by extracting only

[0008]

By using the partial discharge measuring section in the prefabricated connection section for a power cable having the above-described configuration, a signal is induced at the detection electrode when a partial discharge occurs in the measurement target portion.

According to the above-described method for measuring partial discharge at the prefabricated connection portion for a power cable, detection signals at two adjacent measurement target portions are obtained differentially to remove external noise having the same phase, thereby reducing the EP noise. Only the partial discharge signal at the rubber mold insulator interface is extracted.

[0010]

FIG. 1 is a diagram showing the principle of the present invention. In a power cable connecting portion such as a prefab joint, a cable insulating layer 11a covering a cable conductor 10a, 10b is provided.
A pre-mold insulator 12 is provided around the periphery of 1b, and the outside thereof is covered with a grounded conductive layer 13 made of metal. The pre-mold insulator 12 is composed of two inner layers 14 made of, for example, an EP rubber mold body, one outer layer 15 made of an epoxy insulator, and two semi-conductors 16,
Radially outside the interface A between the cable insulating layer 11 and the inner layer 14 and the interface B between the inner layer 14 and the outer layer 15 to be measured for discharge, an annular detection electrode 17a inside the outer layer 15 near the conductive layer 13, 17b is buried. Also, signal lines 18a, 18b are provided from these detection electrodes 17a, 17b.
Are drawn out through holes 19a and 19b provided in the conductive layer 13, respectively.
20b. Signal lines 18a, 18b
The low frequency component is removed from the signals from the coils L1 and L2, and the signals are connected to the signal detection circuit 22 via a differential circuit including capacitors C1 and C2, resistors R1 and R2, and a differential transformer T grounded at the middle point. ing.

In the above configuration, first, before measurement, the variable capacitance C2 and the variable resistance R2 are adjusted so that the differential circuit is zero-balanced against noise invading the line and partial discharge in other parts. In this state, the detection electrode 17a and the cable insulating layer 11
, Or between the detection electrode 17b and the cable insulating layer 11, a partial discharge occurs.
When a high-frequency pulse is induced in 17b, the respective partial discharges occur independently of each other, so that the signals are detected without being canceled even through the differential circuit. On the other hand, noise generated by an external factor or partial discharge in another part of the line is not affected by any of the detection electrodes 17a and 17b.
Since the same induced pulse is also generated, it is not canceled out by the differential circuit and detected as a signal.

Therefore, according to the above-described configuration, only partial discharges generated at two specific portions to be measured for discharge are determined.
Detection can be performed without being affected by external noise.
It is preferable that the detection resistors 20a and 20b interposed between the conductive layer 13 and the detection electrodes 17a and 17b are short-circuited by the switches 21a and 21b during non-measurement.

FIG. 2 shows a specific structure when the present invention is applied to a prefab joint. In FIG. 2, the cable conductors 10 of the power cable are connected to each other, and a pre-molded insulation reinforcing member 30 made of epoxy resin or the like is provided around the exposed cable insulation layer 11. Similarly, a pre-molded insulator 31 and a semi-conductor 32 made of EP rubber or the like, which are similarly pre-molded, are press-fitted between the insulation reinforcing body 30 and the cable insulating layer 11, and are fixed by a pressing pipe 33. That is, the interface A between the cable insulating layer 11 and the pre-mold insulator 31;
The interface B between the pre-mold insulator 31 and the insulating reinforcement 30 is a measurement target of the partial discharge. On the outer periphery of the insulating reinforcing body 30 corresponding to the periphery of these interfaces A and B, a detection electrode 3 made of a semiconductive paint layer 34, a lead tape or the like is sequentially arranged from the inside.
5, an insulating tape layer 36 such as vinyl chloride and a conductive layer 37 such as a lead tape are provided. These members are formed symmetrically, and the insulating tape layer 36 and the conductive layer 37
Extends further to the other insulating tape layer 36 and the conductive layer 37 through the periphery of the insulating reinforcing body 30, but the semiconductive paint layer 34 and the detection electrode 35 are located at positions corresponding to the ends of the interfaces A and B, It is once cut off at the center. Further, a protective case 38 such as a conduit is provided on the outer periphery thereof, and is grounded together with the conductive layer 37. The detection terminal 39 connected to the detection electrode 35 is fixed to the protective case 38 via an insulating spacer 40.

At the time of measurement, the detection terminals 39 and the protection case 38 are connected to the detection resistors 20a and 20b as shown in FIG.
And the outputs of the left and right detection terminals 29 may be connected to a differential detection circuit.

In the above description, the configuration of the differential circuit is not limited to that of the embodiment, but various configurations can be considered. Further, in the above-described embodiment, only one phase of the power cable has been described. However, the present invention can be similarly implemented in multiple phases. Furthermore, it is also possible to take out the differential output of each phase further differentially and measure a plurality of phases at the same time, or to activate signals of a plurality of longitudinal connection parts by using detection signals of other connection parts. It is possible.

[0016]

As described above, the partial discharge measuring part and the partial discharge measuring method using the prefabricated connecting part for the power cable according to the present invention can be applied to the specific measuring object part such as the connecting part of the power cable. The generated partial discharge can be measured accurately without being affected by extraneous noise, and accurate determination of the discharge can be made, which is extremely effective in ensuring the safety of the cable route.

[Brief description of the drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a partial sectional view of a prefab joint.

FIG. 3 is a side view of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Cable conductor 11 Cable insulating layer 13, 37 Conductive layer 17a, 17b, 35 Detection electrode 18a, 18b Signal line 20a, 20b Detection resistor 22 Signal detection circuit 30 Insulation reinforcement

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Noriaki Imai 1008, Niibori, Kumagaya-shi, Saitama Mitsubishi Cable Industry Co., Ltd. (56) References JP-A-63-73166 (JP, A) JP-A-61-196174 (JP, A) JP-A-63-233381 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01R 31/12-31/20

Claims (2)

(57) [Claims] 1. A pre-molded insulator and semi-conductor,
Mold insulation reinforcement, two pieces spaced apart in the longitudinal direction
Ring electrode, insulating tape layer, grounded conductive layer from inside
The prefabricated connections that are sequentially laminated are
A prefabricated connection portion for a power cable , wherein the detection signal line is attached to a cable insulating layer near a connection portion between conductors and a detection signal line is drawn out from the annular electrode.
Partial discharge measurement unit that. 2. A pre-molded insulator, a semi-conductor and a pre-molded insulator.
Mold insulation reinforcement, two pieces spaced apart in the longitudinal direction
Ring electrode, insulating tape layer, grounded conductive layer from inside
The prefabricated connections that are sequentially laminated are
Deposited on the conductor between the connection portion near the cable insulation layer, wherein each drawer a detection signal line from the annular electrode, interposing a detection impedance between the conductive layer and each of the detection electrodes, the resulting 2 A prefabricated type for power cables, characterized by removing the common-mode signal by extracting two detection signals differentially and extracting only the partial discharge signal
Partial discharge measurement method at connection part .