Power frequencies tests

Power frequency tests after erection at site, if required, may be conducted at 15% of the values indicated above. Also refer to field tests (Section 14,5, Table 14,8),... 

A repeal power frequency test, if considered necessary, inu.st be performed at 80% of the prescribed lest voltage. See also Section I4.5. 

ASTM D149, Test Methodsfor Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials at Commercial Power Frequencies, Vol. 8.01, ASTM, Philadelphia, Pa., 1987. 

Verification of dielectric properties, limited to power frequency voltage withstand or HV test on power as well as control and protective circuits. 

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. 

Wet test While an indoor type switchgear assembly requires only a dry power frequency voltage withstand test, the outdoor type switchgear assembly also needs a wet test under wet conditions to check the external insulation. For the test procedure refer to lEC 60060-1. 

When the required test voltage is not available at site, the reduced voltage power frequency withstand test may be carried out at still lower test voltages, depending upon the voltage availability at site. Then the duration of the test must be increased as shown in Table 14.8, and IS 10118-3 and BS 159. 

Field tests Power frequency withstand test on the primary windings (for un-grounded VTs). The value of the test voltage and the test procedure, is almost the same as that for a switchgear assembly (Section 14.5). 

Power frequency withstand test on the secondary circuit... 

The secondary windings should be capable of withstanding a rated power frequency, short-duration withstand voltage of 3 kV for I minute, (iii) Power frequency withstand test between sections... 

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... 

Protection, maintenance and testing of capacitor units 26/839 Table 26.3 Power frequency lest voltages and their duration for voltage tests on a power capacitor unit or bank... 

The above tests refer to dry power frequency voltage withstand tests for indoor units. Outdoor capacitor units will be subjected to a wet test as in lEC 60060-1. 

Rated power-frequency short-duration withstand voltage for volfoge test... 

Nominal system voltage V, Rated maximum system voltage One-minute power frequency withstand voltage at any frequency between 25 and 100 Hz (phase to ground) Field test after erection at site (phase to ground)... 

For a power frequency voltage withstand test a d.c. test is generally not recommended on a.e. equipment, unless only d.c., test voltage is available at the plaee of testing. The d.e. test values, as above, are therefore for such eventualities only and are equivalent to power frequency a.c. voltage withstand test values. 

These are generally the same as the routine tests. No field test as regards the power frequency voltage withstand or HV lest is normally prescribed on a bus system, which has already been tested at the manufacturer s works. Repealed application of high voltage may deteriorate the insulating properties of the insulation system and its life unless modification has been carried out at site or where the insulation of joints between the busbars can be completed only after erection at site. In such cases, if this test becomes essential it can be conducted,... 

IEC 60243, Electrical strength of insulating materials - Test methods - Part 1 Tests at power frequencies, 1998. 

The British standards are the same as the IEC methods and numbered as BS EN 60243. The ASTM equivalent at power frequencies is D14936 which has a similar choice of procedures. The details of the procedures are left to the material specification and, again, it should be emphasised that results are only comparable if exactly the same procedure and conditions are used. There is also a separate ASTM method37 for proof testing of thin sheet material. ASTM D153 1 38 is for direct voltage and D342639 for impulse tests. 

ASTM D149, 97 (2004). Standard test method for dielectric breakdown voltage and dielectric strength of electrical insulating materials at commercial power frequencies. 

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