IEEE 421.3-1997 pdf download IEEE Standard for High-Potential Test Requirements for Excitation Systems for Synchronous Machines
3.2 Type of tests High-potential tests fall under two categories: acceptance and service tests.
3.2.1 Acceptance Acceptance tests shall be made at the factory at standard test voltage on all circuits after Þnal assembly. Rotating equipment shall be tested after all functional testing is complete. Controls and other equipment shall be tested before functional testing. Acceptance tests, if repeated in the Þeld during installation, shall be conducted at 75% of the standard test voltage.
3.2.2 Service Service tests can be made at any time after installation to verify the integrity of the insulation. The voltage applied during service tests shall not exceed 65% of the standard test voltage. NOTEÑUsers are cautioned to follow the manufacturersÕ recommendations for protecting semiconductor components when performing high-potential tests. If a generator main Þeld circuit breaker or exciter Þeld circuit breaker is used, the exciter may be tested with or without the breaker installed. If tested with the breaker installed, the input side of the breaker (breaker open) will be subjected to the test levels established by this standard. If this test level exceeds the 75% level acceptance test voltage for the breaker, then the test must be performed with the breaker disconnected. 4. Frequency and waveshape of test voltage The test voltage shall be at the excitation system rated frequency (25Ð60 Hz), and the shape of the wave shall be a sine wave with a deviation factor not greater than 10% with the equipment under test connected to the test apparatus. As an alternate to the preceding, direct voltage (dc) may be used, in which case the peak test voltage shall be 1.7 times the rms value of the corresponding alternating voltage.
5. High-potential test considerations High-potential testing is a test of the integrity of the insulation system where little current ßows unless there is a failure of the insulation system. Excitation systems may incorporate devices that could carry signiÞcant current with no insulation system failures when voltage is applied from circuit to ground. Examples of such devices are line-to-ground capacitors, shaft current suppressors, voltage attenuators, etc. During high-poten- tial testing, the ground connection should be removed and insulated from ground so that the high-potential test applies equal stresses to the device and associated wiring, and the ground current that ßows is an indica- tion of dielectric failure.
6. Duration and application of test voltage The test voltage shall be applied continuously for a period of 60 s. The test voltage shall be successively applied to each electric circuit with all other electric circuits and metal parts grounded. Interconnected polyphase windings may be considered as one circuit.
7. Measurement of test voltage The test voltage shall be measured by a voltmeter with equipment under test connected to the test equipment. The voltmeter shall derive its voltage directly from the test voltage, through a voltage divider, through an auxiliary ratio transformer, or by means of a voltmeter coil placed in the testing transformer. The voltmeter shall indicate the rms voltage or, if direct voltage is used, the voltmeter shall indicate the peak voltage.
IEEE 421.3-1997 pdf download
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