Developing technology for 1200 kv transformer

Transformers & Rectifiers (India) Ltd (TARIL) have participated in Mega Project of 1200 kV Testing station at BINA conceived and developed by PGCIL, by contributing one phase 333 MVA, 1150/√3/400/√3/33 kV Auto Transformer.

Development of 1200 kV technology has been a great experience for TARIL. UHV technology is not yet established. It is still in the nascent stage. There has been a few experimental test lines in USA, Japan, Italy, USSR, China etc. Commercial operation is limited to Chinese 1100 kV line commissioned in 2009 or erstwhile USSR 1150 kV line which operated for a short period.

1200 kV AC Transmission corridors are essential for India considering that excess generation in Eastern and North Eastern blocks is to be transmitted to load centres located far away in Northern and Western regions. In view of lead time available before commercialization PGCIL embarked upon idea of developing a 1200 kV test station along with a short 1200 kV transmission line using Public Private Partnership (PPP) model. First phase comprising 3 single phase Auto Transformers forming a bank of 1000 MVA, 1150/400/33 kV has been commissioned on No Load.

UHV transformer is the largest and the most critical device in the power system link. Reliability of the grid highly depends on a larger extent on the reliable transformers. Reliability is the sum total of reliable specification, reliable design, reliable material, reliable manufacturing and of course reliable O&M at site.

Developing 1200 kV Class reliable transformer for TARIL, who specialized in special transformers and power transformers up to 220 kV ranges of transformers, was a great challenge which has been met with successfully and is a history now.

The paper discusses various critical design issues experienced viz. dielectric design, thermal design, control of a powerful leakage field, short circuit withstand capability etc. UHV Transformers are essentially large rating transformers and require facilities to handle larger assembly weights and dimensions. The paper discusses the efforts made for addition in infrastructure and manufacturing facilities to manufacture such high rating transformer. Manufacturing processes & in process checks adopted have been dealt with at length. Paper also highlights the test methodology of such UHV transformers and compares test results obtained vis-a-vis designed values.