protective equipment Flashcards
The simplest way to protect an electrical substation from lightning is with ? protection.
direct stroke
According to the National Electrical Safety Code, substation shield (static) wire should be limited to a maximum design tension of ? per conductor.
2000
If the transmission system entering a substation does not employ shielding, the substation shield wire should not extend beyond the substation fence.
false
Station class arresters are recommended for all substations of ? and above.
10000kva
The only class arrester available for systems with voltages above ? are station class arresters.
150kv
Intermediate class arresters are available in ratings of 3 kilovolts through 69 kilovolts only.
false
There are advantages of protecting the main transformer in smaller rural substations with ? . One advantage is the lower initial cost. Utilizing alternative methods requires auxiliary equipment like CTs and relays.
power fuses
If substation power transformers are protected by fuses, the transformer surge arresters should be connected ? . This is to avoid stress and partial melting of the fuse link during an overvoltage event.
on the side of the fuses
A circuit breaker with external source and load connections made through conventional bushings is the ? type
dead tank
Circuit breakers using SF6 gas as the insulating medium are available with three operating mechanisms: pneumatic, hydraulic, and ? operated.
spring
A circuit breaker’s rating is based on its ? capacity.
load current carrying
When installing or maintaining an oil circuit breaker, inspection and adjustment of the mechanism in both the open and closed position is performed. To open and close the breaker contacts, a ? is used.
manual jack
When inspecting a substation circuit breaker, a broken seal or cracked bushing may mean there is water in the oil.
true
PCBs may be present in a substation oil-filled piece of equipment if it was built before ?
1980
SF6 gas is ? times heavier than air and will settle in low places.
5
