Development of 154kv and 275kv polymer bushings for transformer

Summary

Many power facilities were damaged by the Great East Japan Earthquake in 2011. It took one week for restoration of power supply. Earthquake scale of maximum 800 gal, which exceeded assumed designs of the substations, was observed, and many porcelain insulator-type devices were damaged. It is necessary to prepare for epicentral earthquakes such as the Nankai Trough and Capital Inland earthquakes from now on. For this reason, power companies have been started to apply polymer devices to reduce the risk of earthquake damages in power devices and restoration costs. For transformer bushings, power companies request anti-earthquake performance, existing equipment compatibility, environmental harmony (oil-less, SF6 gasless), and achievement of exchange for aged polymer devices and so on. In this time, we developed new type bushings for 154 and 275kV having eco-friendly gas and anti-earthquake performance by using polymer hollow core insulators (polymer tubes) inside with nitrogen gas and RIP (Resin Impregnated Paper) capacitor bushing. For supporting insulation between the main outdoor circuit and the transformer container (ground), the polymer tube was adopted. For the insulation of inner oil and the control of electric field in the polymer tube, RIP capacitor bushings, which have been proven track record in GIS (Gas Insulated Swichgear), etc., was adopted. By applying the suitable capacitor, it becomes possible to get the insulation structure not to discharge inside tube space and inner surface even when nitrogen gas was used. With these ideas, we developed new type polymer devices, which are lightweight, anti-earthquake performance and non-use of insulating oil and SF6 gas. Transformer oil and charging gas are also partitioned by RIP bushing. Therefore, it is possible to replace aged polymer tubes without removing transformer oil in the future. In order to confirm performance of our developed prototype polymer bushings, the related tests of Japanese transformer bushing standards (JEC-2200, JEC-5202) and IEC standard (IEC 61462) were carried out as type tests. And also, the time-history vibration tests were conducted according to Japanese transformer equipment seismic design guideline (JEAG 5003) and US seismic test standard (IEEE 693). All verification tests were successfully passed. In this paper, the development background, several innovative design concepts and verification test results of the polymer bushings for 154kV and 275kV will be introduced in details.

Additional informations

Keywords

Polymer bushing, Eco-friendly gas, Anti-earthquake performance