JPH0454467A - Easy diagnostic method for mounted arrester on 3-phase power cable - Google Patents

Abstract

PURPOSE:To easily diagnose an arrester by measuring interphase voltages and arrester leaking currents flowing in each arrester in a live-line state, performing a delta-ster conversion of the interphase voltages and comparing with the voltage/current characteristics of a normal arrester. CONSTITUTION:The interphase voltages of connecting conductors 5A-5C are measured by voltmeters 6A, 6B, 6C from the surface of insulation coatings 5a-5c. The currents flowing in the conductors 5A-5C, i.e., the arrester leakage currents of each gapless arrester 4A-4C are measured in a live-line state by utilizing current transformers 7A, 7B, 7C. Then the obtained each interphase voltage are converted to each phase voltage between the conductors 5A-5C and the ground by the delta-star conversion. Thus obtained arrester impressing voltage and arrester leaking current of a certain phase are compared with the voltage/current characteristics of the normal arrester, and by this comparison, the diagnosis is easily made whether the arrester is normal or abnormal.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a three-phase power cable for simple diagnosis of whether an arrester connected to a connection part of the three-phase power cable is normal or abnormal. The present invention relates to a simple diagnosis method for mounted arresters.

U Prior Art] As shown in FIG.
Although not shown, cross-bond connections are made at locations B and 2C, and gapless arresters 4A, 4B, and 4C are installed for each phase on shielding layers (metal outer boxes) 3A, 3B, and 3C of these connection portions 2A to 2C. Connection conductors 5A and 5B each have an insulating coating at one end.

5C, and the other end of each arrester 4A to 4C is grounded to the earth. When an abnormal current flows through the shielding layer of the power cable IA to IC of each phase, the abnormal current is connected to the arrester 4A to 4C. This prevents dielectric breakdown of the insulating layer provided on the surface of the shielding layer.

In such arresters 4A to 4C, no arrester current flows because the potential between the shielding layer and the ground is zero, but when the potential increases (for example, 2 KV or more), the arrester current flows and the shielding layer It works to reduce the potential between earth to almost zero.

It is necessary to periodically inspect such arresters 4A to 4C to determine whether they are normal or have deteriorated and become abnormal due to the flow of an abnormal current.

Conventionally, such deterioration diagnosis of the arresters 4A to 4C has been carried out by removing each arrester 4A to 4C in use, connecting a new arrester 4A to 4C, and connecting each of the removed arresters 4A to 4C.
C was taken back to the factory, high voltage was applied to each arrester 4A to 4C using a high voltage generator, and the leakage current was measured.

[Problems to be Solved by the Invention] However, in this method of diagnosing arresters, the diagnosis is performed by removing each installed arrester and taking it home, which has the problem that diagnosis cannot be performed on the spot and is time-consuming. was there.

An object of the present invention is to provide a simple method for diagnosing a mounted arrester in a three-phase power cable, which allows a simple diagnosis of the mounted arrester in its current state.

[Means for Solving the Problems] To explain in detail the present invention for achieving the above object, the present invention provides a method in which each end of an arrester is connected to each shielding layer of a three-phase power cable by a connecting conductor. A simple diagnosis method for a mounted arrester in a three-phase power cable in which the other end of each of the arresters is grounded, comprising: measuring the phase-to-phase voltage between the connecting conductors;
determining the arrester applied voltage applied to each of the arresters by delta-star conversion; measuring the arrester leakage current flowing in each of the arresters; and determining the arrester applied voltage and the arrester leakage current of each of the arresters. The present invention is characterized in that a simple diagnosis of whether the arrester is normal or abnormal is performed by comparing the arrester voltage and current characteristics with the arrester voltage and current characteristics of a normal product.

[Operations] In this way, the interphase voltage between each connected conductor can be easily measured in a live wire state. By performing delta-star conversion on the basis of each measured phase-to-phase voltage, it is possible to obtain each phase voltage between each connecting conductor and the ground, that is, the arrester applied voltage applied to each arrester.

Furthermore, the arrester leakage current flowing through each arrester can be easily measured in a live wire state using a current transformer or the like.

By comparing the arrester applied voltage and arrester leakage current measured in this manner with the arrester voltage/current characteristics of a normal product, it is possible to easily diagnose whether the arrester is normal or abnormal.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings. Note that parts corresponding to those in FIG. 3 described above are indicated with the same reference numerals.

In this embodiment, as shown in FIG.
C phase-to-phase voltage (i.e., between A phase and B phase, between B phase and C phase, C
Each phase-A voltage) is measured from above the insulation coatings 5a to 5C of these connecting conductors 5A to 5C using voltmeters 6A, 6B, and 6C, respectively.

Further, the current flowing through each of the connection conductors 5A to 5C, that is, the arrester leakage current of each gapless arrester 4A to 4C is measured in a live state using current transformers 7A, 7B, and 7C.

Such arrester leakage current can be measured in a non-contact manner up to about 10XIO-6A using a combination of current transformers 7A to 7C and an ammeter.

The obtained phase-to-phase voltages are calculated by the well-known delta-star conversion as shown in FIG. -neutral point n
(voltage between phase C and neutral point n). Each phase voltage obtained by this conversion corresponds to the arrester applied voltage applied to each arrester 4A to 4C.

By comparing the arrester applied voltage and arrester leakage current of the arrester of a certain phase obtained in this way with the arrester voltage and current characteristics of a normal product provided by the arrester meter, it is possible to determine whether the arrester is normal or abnormal. Perform a simple diagnosis.

In the above embodiment, the diagnosis of a gapless arrester has been described, but the present invention is not limited thereto, and can be similarly applied to the diagnosis of an arrester with a gear.

[Effects of the Invention] As explained above, in the simple method for diagnosing the mounted arrester in a three-phase power cable according to the present invention, the phase-to-phase voltage between the connecting conductors and the arrester leakage current flowing through each arrester are measured. These measurements can be easily performed under live wire conditions. Since the measured phase-to-phase voltage is subjected to delta-star conversion, the arrester applied voltage applied to each phase voltage portion between each connecting conductor and the ground, that is, each arrester, can be easily determined. By comparing the voltage applied to the arrester and the arrester leakage current with the arrester voltage/current characteristics of a normal product, a simple diagnosis of each arrester can be easily performed without removing the arrester.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram for measuring voltage and current at the arrester connection part implementing the method of the present invention, Fig. 2 is an explanatory diagram of delta-star conversion, and Fig. 3 is a side view showing the state of connection of the arrester to the power cable. It is. IA-IC...Power cable, 28-2C...Connection part, 3A-3C...Shielding layer, 4A-4C...Arrester, 5A-5C...Connection conductor, 6A-6C...・Voltmeter, 7A to 7C...Current transformer.

Claims (1)

[Claims] A mounted arrester in a three-phase power cable, in which one end of each arrester is connected to each shielding layer of the three-phase power cable by a connecting conductor for each phase, and the other end of each arrester is grounded. In the simple diagnosis method, measuring the phase-to-phase voltage between the respective connecting conductors,
determining the arrester applied voltage applied to each of the arresters by delta-star conversion; measuring the arrester leakage current flowing in each of the arresters; and determining the arrester applied voltage and the arrester leakage current of each of the arresters. 1. A simple method for diagnosing a mounted arrester in a three-phase power cable, the method comprising: comparing the arrester voltage and current characteristics with the arrester voltage and current characteristics of a normal product to easily diagnose whether the arrester is normal or abnormal.