Page 366 - Offshore Electrical Engineering Manual

CHAPTER
3
Switchgear

AIR BREAK SWITCHING DEVICES AND FUSES RATED FOR USE
AT VOLTAGES BELOW 1000 V
First, the equipment should be given a thorough mechanical and visual inspection.
This includes the following:

1. The equipment should be clean and dry and free from extraneous loose items or
tools.
2. Insulators and insulation should be clean and dry.
3. Indicating, protective and interlocking devices should operate satisfactorily.
4. All conducting connections should be secure and intact.
5. The ratings of fuses, relays and other devices should be as shown on design
drawings.
6. Cables should be of adequate cross section and correctly glanded and
terminated.
7. Internal wiring should be correctly secured.
8. Switching contacts should normally be sparingly applied with a suitable con-
tact lubricant, but the manufacturer’s manual (or the manufacturer’s advice)
should be consulted, as, in some conditions, this may lead to contact sticking or
reduced fault clearing capability.
9. The mechanisms of switching and interlocking mechanisms should be checked
for smooth and correct function.

Electrical tests will then need to be completed as follows:

1. A primary insulation test should be carried out on each phase to ground and
from each phase to phase using the test voltages shown in Table 7.3.1.
2. The insulation resistance of small wiring and ancillary components should be
tested using a Megger or similar device, where the test voltage is not greater
than 500 V direct current (DC).
3. The overloads of motor control gear should be injection-tested at 100%, 125%
and 600% setting values and checked against the manufacturer’s tripping times.
4. Each thermal or magnetic element should be tested individually. Tests made on
thermal elements should include for both ‘hot’ and ‘cold’ operating conditions.
5. The switchboard metering, i.e., all ammeters, voltmeters, current transform-
ers (CTs) and voltage transformers (VTs), etc., should be checked for correct
calibration.

Offshore Electrical Engineering Manual. https://doi.org/10.1016/B978-0-12-385499-5.00042-X 353
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