Power frequency

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. 

Power frequency voltage withstand level, according to Section 14.3.3 and... 

No ni ial syste n voltage kV r.m.s.) Rated maximum system voltage V, kV(r.tn.s.) Standard one-minute power frequency withstand voltage KV (r.m.s.) Standard lightning impulse (1.2/50 ps) withstand voltage phase to ground kV (peak) ... 

More than one lightning impulse insulation level is indicative of the extent of exposure of equipment to lightning surges. Correspondingly the power frequency withstand voltage can also be more than one. 

One-minute power frequency withstand voltage from Table 32.1A. 

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

Insulation levels, power frequency and impulse withstand voltages for metal-enclosed switchgear assemblies... 

Nominal system Rated maximum One-mhuite power frequency voltai e withstand Standard lightning impulse ... 

Nominal system Rated maximum One-minute power frequency Standard lightning impulse One-minute d.c. voltage ... 

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),... 

One-minute power frequency voltage withstand at any frequency between 45 and 65 Hz (between phases and ground)... 

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. 

A repeal power frequency lest, if considered necessary, must be performed ai 80% of the prescribed test voltage. See also Section 14.5. 

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... 

The instant at w hich the power frequency current will pass through its natural zero, i.e. where i = 0, is termed its natural current zero (or current zero), where... 

A surge capacitor offers a near-open circuit during normal operation (at or near the power frequencies) and a near-short-circuit to the arriving surges at surge frequencies, while the inductance of the motor windings (<> will... 

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