Steep Wave Front Impulse Test on High Voltage Insulators

Test method for 33kV porcelain disc insulators.

The Steep wave front test should be performed on 10 disc insulators selected at random. Each insulator should be subjected to ten successive positive and negative impulse flash-over with a wave having an effective rate of rise of 2500kV/μs. Then rated dry or wet power frequency withstand voltage shall be applied to each disc insulator. If there is no electric puncture, the insulators are considered to be successfully passed the test.

Failure of any one unit either in the steep front-of-wave test or subsequent power frequency withstand voltage test shall cause for testing another 20 units. Failure of more than one unit from the total so tested shall constitute failure to meet the requirements of this specification.  

Steep-front impulse test is the test that yields the most information on product quality and performance

This test is included as a design test in IEC 61211 for ceramic (porcelain and glass) insulators and in IEC 61109 for composite insulators. It is essentially an impulse voltage test, except that the voltage rises much faster than used in lightning and switching impulse testing.