IEEE Std 95:2002 pdf free download

IEEE Std 95:2002 pdf free download.IEEE Recommended Practice for Insulation Testing of AC Electric Machinery (2300 V and Above) With High Direct Voltage.
Prior to performing a high voltage test. harriers must he in place in restrict access to the testing area and machinc tinder test. This safety measure is necessary to prevent personnel from inadvertently coming into contact with energized equipment (see IEEE Std 510-1983).
Test personnel should be advised that application of a high direct voltage resuks in a stored charge in the capacitance of the winding under test. De-energizing the test source will not immediately dc-energize the winding. The stored charge may be hazardous to equipment and/or personnel. Windings that have been tested with direct voltage must be fully discharged and solidly grounded before being handled by personnel.
Ungrounded objects in the vicinity of the winding under test should be solidly connected to ground to prevent induced voltages.
Before making a high direct-voltage test, the stator winding should be deemed suitable for high voltage testing. Insulation resistance and polarization index should be at or above the minimum values specilied in IEEE Std 43-2000.
A machine should not be placed in service after a high direct-voltage test until the winding has been grounded for an appropriate period of lime, If a high alternating-voltage test is to follow a high direct-voltage test. ii is advisable to double the minimum grounding time to ensure that the absorbed charge does not contribute to insulation failure during the subsequent alternating-voltage test. This may occur if the residual direct voltage, superimposed on the peak alternating voltage, exceeds the electric strength of the insulation.
4.2 Influencing factors
Factors affecting the condition of the winding should be evaluated prior to pertbniiing a high direct-voltage
4.2.1 Temperature
A direct-voltage test should be made at winding temperatures at or below 40 ‘C, unless otherwise agreed upon between the user and the manufacturer.
Insulation resistance and dielectric absorption vary with temperature. Therefore, consistent temperatures are required for accurate and comparable current measurements. Winding temperatures near ambient are preferred. Otherwise, measured resistance values must be normalized before comparison (see IEEE Std 43- 2000).