IEEE Std C37.21 pdf free download
IEEE Std C37.21 pdf free download.Control Switchboards.
6.3.3 Polarity and phase verification
Test shall be made to ensure that connections to meters or relays, etc., are correctly made to the proper phase and with proper polarity. Instruments shall be tested to ensure that the pointers move in the proper direction and that the direction of indicated quantities is correct.
6.3.4 Sequence tests
Switchboards involving sequential operation of devices shall be tested to ensure that the devices in the sequence function properly and in the order intended.
This sequence test need not include remote equipment controlled by the switchboard. However, this equipment may be simulated, where necessary.
6.4 Field dielectric test
When dielectric withstand tests are to be made on switchboards after installation in the field, the switchboard shall not be tested at greater than 75% of the test values given in 6.3.1. Some devices must be disconnected because the applicable industry standard involves a lower or different permissible dielectric test.
As an alternative to ac dielectric tests, an insulation-resistance test using a dc voltage level no less than the ac level listed in 6.3.1, (1500 x 1.414 x O.75 for not more than 1 mm with a minimum measured insulation resistance of I Mc).
NOTE—Field tests are recommended when new units are added to an existing installation or after major field modifications are made. The equipment should be put in good condition prior to the field test. It is not expected that equipment shall be subjected to these tests after it has been stored for long periods of time or has accumulated a large amount of dust, dirt, moisture, or other contaminants without first being restored to good condition.
7. Construction
7.1 General requirements
7.1.1 Phase or polarity arrangements for ac
When tacing the tront ot the assembled devices as viewed trom the outside ot the switchboard, the phase arrangement on a three-phase control switchboard shall be 1, 2, 3 (or A, B, C) from front to back, top to bottom, or left to right. For inclined panels, the arrangement shall be as viewed perpendicular to the panel. Certain types of equipment may require other phasing arrangements. In these cases, the phasing shall be suitably indicated.
7.1.2 Polarities for dc
When facing the front of the assembled devices as viewed from the outside of the switchboard, polarities of dc connections shall be positive, negative from front to back, top to bottom, or left to right. For inclined panels, the arrangement shall be viewed perpendicular to the panel. Certain types of equipment may require other polarity arrangements. In these cases, the polarities shall be suitably indicated.
7.1.3 Phase sequence
The phase sequence, unless otherwise specified, shall be such that, when considering voltage to neutral on a polyphase system with respect to the element of time, the voltage of Phase 1 will reach a maximum ahead of the voltage of Phase 2, Phase 3, etc. This sequence shall be designated as phase sequence in the order 1,2, 3. Other suitable designations for the same order of rotation may be used.
7.1.4 Grounding
A ground system bus shall be included that will electrically connect together the structures in a switchboard assembly and shall run the full length of the switchboard.IEEE Std C37.21 pdf download.
