Testing impulse voltage withstand

This is a resin-rich system. The stator is wound with pre-formed coils on similar lines as noted above. After thorough testing on each coil for the polarization index and dissipation factor (tan S), as discussed in Sections 9.5 and 9.6, and the impulse voltage withstand test, as discussed in Section 11.4.9, the individual coils are completely cured and toughened before inserting them into the slots. The rest of the process is as noted earlier. 

Impulse voltage withstand test of the insulation system for rated voltages 2.4 kV and above for machines wound with formed coils 11/261... 

Principal considerations in framing the specification for impulse voltage withstand level and underlying the test procedures 11/262... 

Impulse voltage withstand test for system voltages 2.4 kV and above... 

Between line and load fixed terminals of each phase. ANSI-C37/20C recommends this test to be conducted at a value 10% higher than specified in Table 14.2 for both power frequency and impulse voltage withstand tests. 

For non-effectively grounded systems, having a GFF of more than 1.4, a higher level of insulation (BIL) will be essential for all equipment being used on the system to withstand a higher level of a one-minute power frequency voltage test as well as an impulse voltage withstand test if such levels (Lists I, II and III) are prescribed in the relevant standards. If not, then it may be assumed, that the prescribed test values take account of such an... 

A voltage waveform with 1.2/50 ps (wave front Tf= 1.2 ps, wave tail = 50 ps) and a current waveform with 8/20 ps are used as lightning impulses to test the withstand voltage of home appliances or electronic equipment in general. The impulse voltage is mainly used for high-impedance equipment, and its maximum value is taken as 6 kV. On the other hand, the impulse current is mainly for low-impedance equipment, and its peak value is taken as 3 kA [18,19]. 

The impulse test is basically an in-house coil insulation withstand test for surge voltages and forms a part of the test requirement for HT machines with resin-rich formed coils of 2.4 kV and above. Once the machine is assembled, such a test is unnecessary, as it may not be able to reveal deficiencies, if any, in the insulation of the coils deep inside the slots. Moreover, if a failure is noticed on the assembled machine, there is no option but to scrap the whole winding. 

For impulse withstand voltages across the contact gaps of an interrupting device, refer to lEC 60694 and lEC 60298, Wet or dew test is a weatherproof test (Section I4..5.I0) and is meant for outdoor assemblies. 

A voltage waveform with 1.2/50 ps (wavefront Tj= 1.2 ps, wavetail T(=50 ps) and a current waveform with 8/20 ps are adopted as a lightning impulse to test a withstand voltage of home appliances or electronic equipments... 

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