Discussion on the configuration of auxiliary material tools and facilities for PD test system

- Apr 26, 2018-

The partial discharge test of medium voltage XLPE cable involves more auxiliary test material and tool facilities, in the concrete use of these tool material facilities, there are some defects and deficiencies, need to be further perfected to ensure the safe and smooth completion of the field test, and present the specific opinions and suggestions,

For cable manufacturers and testing equipment manufacturers to improve the reference. In the partial discharge test, the amount of transformer oil is not too much, but when the oil has stolen goods, it will inevitably result in the multiplication of the test cost. Therefore, the test system should be equipped with transformer oil filtration device, so that the insulating oil can be repeatedly used to reduce the cost of testing. At the same time should also be equipped with oil equipment or appliances to avoid contamination of the test site. When the number of test products is relatively large, the test site is often due to lack of oil installation, resulting in a number of oil accumulation on the ground, the surface is exceptionally smooth. The tester often slips to the injury after entering the shielding room. At the same time, the shielding room on the ground long-term accumulation of oil, will gradually corrode insulation floor, resulting in uneven ground. The author has visited some of the use of a few years of cable bureau shielding room floor, found that there is widespread insulation floor surface potholes uneven phenomenon.

In order to protect the insulating floor, there are many manufacturers in the Bureau of shielding room insulation floor surface covered with a layer of steel to protect the cement flooring. The cutting tool of the conductive shielding layer of the XLPE cable is also necessary for the test process. Now the test equipment manufacturers to provide the stripping tool, only the cable half conductive shielding layer of the special stripping cutter, and the lack of cable sheath stripping special tools, to the inspectors to peel off the cable caused a certain difficulty. In the North one to winter, the sheath of the cable will harden to brittle, with the ordinary electrician knife and art knife cut off and peel the sheath is very difficult, at the same time, if the amount of incoming knife can easily scratch the insulation core of the copper tape shielding layer and the outer half conductive shielding layer. Especially for polyethylene sheath, peeling will appear more difficult.

At the same time, the current cross-linked stripping tools less electric, the proposed test equipment manufacturers should develop a set of manual electric dual-use of a series of partial discharge test stripping tool. The quality of test terminals is also becoming a key factor affecting the progress of partial discharge test in cable. After a long scraping of the cable thread in the test process, the cup wall may be in the Oil Cup cup wall inside the surface of the scratch residue, some dirt and small impurities in the oil may precipitate residue in the hanging scar, slowly form the discharge channel, and finally in the Oil Cup on the surface of the wall flashover discharge phenomenon, resulting in the oil cup surface breakdown and explosion. The breakdown principle is similar to the surface breakdown principle of the suspension insulator string of the tie conductor. The laying environment of the conductor suspension insulator string is very bad, its surface often can absorb the dust in the air, guano and other material, resulting in the decrease of the surface insulation ability, which leads to the explosion of the insulator surface pollution flashover phenomenon. Cable test with the end of the oil Cup, as the use of time, the inner wall and the outer wall surface finish and insulation ability will certainly decline, when the test voltage is higher, it is likely to cause the oil cup plexiglass tube is broken, general oil cup metal electrode base will not be damaged. In view of the above facts, we can buy more plexiglass tube as standby, in the test terminal problems after the timely replacement treatment to ensure the normal production and testing. China Wire and cable networkwww.xianlan315.com Oil Cup test terminal in the actual use of the process of cracking is often the 35KV test terminal, 10KV Test terminal has less burst. At the same time the oil cup at the bottom of the thimble spring may be due to the long-term use of aging, spring is insufficient, resulting in the test process conductor wire core and the contact between the electrode undesirable phenomenon. The problem can be solved in time as long as the spring is replaced in time.

At the same time equipped with the best oil cups designed for explosion-proof type, to extend its service life. In the process of partial discharge test by core of three-core cable, three insulating wires must be separated from certain insulating distance to prevent inductive discharge between cores. But for the large section 35KV three-core XLPE cable in the actual test process, we found that it is very difficult to separate the insulating core from the certain distance. Therefore, in the actual test system should consider the design of a cable three-core distance between a certain distance of the tool to ensure that the cable in the test process between the middle core of the induction discharge, when used directly into the cable cable core gap will be insulated core.

The open tool should be able to repeatedly use, but also insulating materials, with a certain strength, compression, the distraction process will not cause damage to the insulation core. At present, the use of the existing Single-Phase partial discharge test system to complete the 10KV three-core XLPE cable partial discharge, AC voltage test, has become the industry's various manufacturers generally accepted and adopted the test method. Many manufacturers use the test system has been prepared 35KV cable test terminal, a complete 10KV three-core cable factory test.

But there is also a cable test terminal developed for the 10KV three-core cable once factory test completed, such as the RT-10A test terminal developed by Shanghai Hui Dong Electric Company. In view of the partial discharge test process used in a variety of auxiliary tools, such as cable shielding layer peeling knife, cable oil cups.

Therefore, it is necessary to put a tool cabinet with the smallest size in the shielding interior design, and the position of the tool cabinet may be far away from the high-pressure test end. The design of the partial discharge shielding test room still needs to be perfected, the shielding room is preferably equipped with a special lighting device in the design, so it is more convenient to work inside.