Application of Variable Frequency Series Resonant to the Transformer in the AC Withstand Voltage Test

Lin Meifen, Xu Jing
HIMALAYAL - SHANGHAI - CHINA

Abstract: The variable frequency series resonant is adopted to conduct AC withstand voltage test for large-medium transformer, which is compared with routine AC withstand voltage test method. Results indicate that the technique of  variable frequency series resonant withstand voltage test has many advantages, such as lower power supply, small volume for the equipment, not damaging the test object. What is more, it can fix some problems, which are not dealt with by routine test technique.  

Key words: Variable frequency series resonant, large-medium transformer, withstand voltage test, capacity

In the hand-over and preventive test of electric power system, AC withstand voltage test is one of the most strict, effective and direct methods to detect insulation strength of electric equipment. It is also an important mode to ensure insulation level and avoid insulation breakdown. Although AC withstand voltage test can detect the insulation defect, test conditions impose restrictions on the test. With regard to withstand voltage test of 35kV and above 8000kVA transformer, the capacitance and current is high, which requires that rated current of high-voltage test transformer be above 100mA. At present, such high-voltage test transformer and regulator are not common. What is worse, the capacity of test transformer is great and it is not easy to carry test equipment owing to its heave weight, which brings the difficult for the test on site. This paper adopts a method of variable frequency series resonant to make equipment with low current and capacity generate required test voltage. The effect is good.