Vu Thanh Hai MSc., Deputy Director, Key Laboratory For High Voltage Techniques
From September 26, 2022 to September 30, 2022, the High Voltage Key Laboratory (HVLAB) of the Institute of Energy has successfully conducted the witness testing of three-phase 220kV/250MVA power transformer with lightning impulse (Lightning Impulse Full Wave-FW and Lightning Impulse Chopped Wave-CW) according to standards IEC 60076-3:2000 (TCVN 6306-3:2006) and IEC 60076-4:2002. This power transformer was manufactured by Dong Anh Electrical Equipment Corporation for 220kV Nghia Lo Substation.
During the working process, the testing circuit configuration of the 3600kV/180kJ impulse voltage test system was calculated and appropriately positioned to ensure the requirements of the testing standard related to lightning impulses (FW and CW) applied to the transformer windings.
After setting up the test circuit configuration, the lightning impulse test of the three-phase 220kV/250MVA power transformer was performed on the 220kV and 110kV windings at all three phases. The shape and value of current impulses generated during the test were also acquired by an independent signal channel and transmitted simultaneously with the voltage impulses (FW and CW lightning impulses).
The evaluation of transformer quality through testing of lightning impulses (FW and CW) is complied with standard IEC 60076-3 (TCVN 6306-3:2006) and IEC 60076-4:2002. In this testing program, the three-phases 220kV/250MVA power transformer designated for Nghia Lo 220kV Substation has satisfied the criteria for lightning impulse test according to the above mentioned standards: there were no incident electric discharge, the shapes of testing impulses are uniform with no abnormalities occurring at the transformer windings.
The successful test of this 3-phase 220kV/250MVA transformer in the limited implementation time, with the requirement of fully testing lightning impulse items on all transformer windings, has shown a significant step forward in both capacity and experience of the staff of the Institute of Energy in providing testing and quality assessment services for electrical equipment put into operation on the national power transmission grid, making an important contribution to the strong development of Vietnam’s electricity industry.
Figure 2: Full-wave lightning impulse (Left) and Chopped-wave lightning impulse (Right) applied to the 220kV windings/phase C of the transformer
