JPH071983B2 - Discharge detection method for power cable transmission system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge detection method for a power cable transmission system.

[0002]

2. Description of the Related Art A power cable transmission system is required to have a higher reliability of insulation than devices installed in a substation.

This is because in the case of the equipment installed in the substation, it is relatively easy to manage because it is inside the substation building, and even if it should fail, it is relatively easy to replace it. On the other hand, if a problem occurs in the power cable transmission system, it is usually difficult to identify its position, and replacement (installation replacement) requires a great deal of labor and expense.

On the other hand, conventional discharge detection of this type of power cable transmission system has been performed by collectively viewing the entire power cable transmission system at the terminal end provided at the end of the line. However, with this means, not only the partial discharge pulse from a distant place (such a partial discharge pulse in a long cable line is almost all) is considerably attenuated by the time the end portion is reached, but also from the outside to the line. The amount of noise that had entered would increase, making it difficult to detect the partial discharge pulse. Moreover, the charge amount of partial discharge due to voids in the power cable insulation layer is usually several PC to several +
In addition to the extremely small amount of electric charge that is on the order of a PC, the power cable transmission system has many long power cables connected to it, which increases the capacitance and reduces the partial discharge pulse voltage to be detected. This makes the detection more difficult.

As described above, there is a difficulty in detecting partial discharge in the power cable transmission system, which is essentially different from partial discharge detection in devices in the substation.

An object of the present invention is to solve this problem, prevent damage to the power cable due to discharge in the power cable transmission system, and prevent the power transmission function from being stopped due to complete destruction of the damaged cable. It is an object of the present invention to provide a novel electric power cable transmission system discharge detection method.

By the way, the power cable line has a connecting portion every several hundred meters, but since the power cable itself is manufactured in a factory under strict quality control, there is almost no trouble. On the other hand, since the connection part is manufactured locally, and also in a narrow space such as a manhole, quality control is not performed like when the power cable is manufactured, which is not always sufficient. Therefore, statistically most of the troubles in the power cable transmission system occur at or near the connection part. In view of these findings, the present inventors provide the following solution.

[0008]

DISCLOSURE OF THE INVENTION In a discharge detection circuit according to the present invention, a well-known insulating connection portion provided in the middle of a power cable power transmission system, that is, an external shielding layer or a metal sheath is cut off along the middle of the connection portion ( Insulation type intermediate connection part (or insulation type intermediate oil stop connection part) that is insulated is interposed between the outer shield layer or the metal sheath at both ends through the insulation part (edge cut part) or a capacitor for overvoltage protection or Connect the primary winding of the pulse detection transformer through the arrester,
Partial discharge and other discharges in the power cable insulating layer from the secondary winding of the pulse detection transformer are detected as a pulsed current generated at an operating voltage.

[0009]

1 is an electric circuit diagram showing an embodiment of a discharge detecting method according to the present invention.

Due to the actual situation as described above, the occurrence of partial discharge and other discharges in the power cable line often occurs around the intermediate connecting portion rather than the main body portion of the power cable. Further, the pulsed current due to the discharge has many high-frequency components and is attenuated as it propagates through the power cable. Therefore, in the present invention, it is extremely important to connect the discharge detecting means to the intermediate connection portion where the occurrence of discharge is concerned. Also, it is of special significance to identify the location of the intermediate connection, which is unique to the power cable transmission system.

In the figure, reference numeral 4 denotes an insulating type intermediate connecting portion (or an insulating type intermediate oil stop connecting portion) in which an outer shielding layer or a metal sheath is cut (insulated) along the connecting portion. Here, the primary winding of the pulse detection transformer 3B is connected between the external shielding layer or the metal sheath at both ends thereof via the insulating portion (edge cutting portion), via the capacitor for overvoltage protection or the lightning arrester 5. Then, by connecting a corona measuring device (not shown) to the secondary winding of the pulse detection transformer 3B, pulsed discharge can be detected. With this configuration, the commercial high-frequency voltage is not applied to the pulse detection transformer 3B, and the iron core of the pulse detection transformer 3B does not saturate.

Reference numeral 1 denotes an intermediate connecting portion having no edge cutting portion. Here, the primary winding of the pulse detecting transformer 3A is connected between the outer shield layer of the intermediate connecting portion 1 or the metal sheath and the ground, and By connecting a corona measuring device (not shown) to the secondary winding, pulsed discharge can be detected.

[0013]

According to the present invention, the detection of discharge occurrence in the power cable transmission system is completely different from the conventional contents, that is, the insulation location of the insulation type intermediate connection portion provided in the middle of the system. The primary winding of the pulse detection transformer is connected between the external shielding layer or the metal sheath at both ends of the pulse detection transformer via the (edge cut portion), and the secondary winding of the pulse detection transformer. Since partial discharge and other discharges in the power cable insulation layer are detected as pulsed currents generated at the operating voltage, it has been considered difficult to determine whether or not a discharge has occurred in the power cable transmission system and the location of that discharge occurrence. It is possible to constantly monitor such things as live lines, and thus prevent ground faults due to the occurrence of the above-mentioned discharge, which in turn can prevent the power transmission function from stopping. .

[Brief description of drawings]

FIG. 1 is an electric circuit diagram of an embodiment of the present invention.

[Explanation of symbols]

2 External shield layer of power cable or metal sheath 3B Pulse detection transformer 4 Insulation type intermediate connection part (or insulation type intermediate oil stop connection part)

Claims (1)

[Claims] 1. A capacitor or a lightning arrester for protecting overvoltage between an external shield layer or a metal sheath at both ends of an insulating type intermediate connecting portion provided in the middle of a power cable transmission system via an insulating portion (edge cutting portion). Is connected to the primary winding of the pulse detection transformer, and a partial discharge or other discharge in the power cable insulating layer is detected from the secondary winding of the pulse detection transformer as a pulsed current generated at the operating voltage. Detection method for electric power cable transmission system.