Which is the primary breaker in the auxiliary system?
The motor relays trip the associated feeder breaker, 51A and 51B trip the 4 kV main breakers and the neutral relays 51N trip their associated primary breakers. It is common practice to provide a bus transfer scheme to transfer the auxiliary bus to an alternative source in the event of the loss of the primary source.
What is the nominal voltage of an auxiliary bus system?
In addition to the 4 kV (or higher) bus, a lower voltage auxiliary bus system is used to feed the dozens or hundreds of smaller motors, heating and lighting loads that are present in the plant. The nominal voltage rating of this lower voltage bus system can be 600 or 240 V.
How are overcurrent relays used in power plants?
A bus differential relay could be used to provide primary protection and the overcurrent relays provide backup protection for motor relay or switchgear failures. The time delay may then be acceptable. The pickup setting must still recognize the magnitude of starting current of the largest motor.
How are auxiliary buses used in power plants?
Current-limiting reactors can be used either as separate devices or incorporated in the switchgear. In addition to the 4 kV (or higher) bus, a lower voltage auxiliary bus system is used to feed the dozens or hundreds of smaller motors, heating and lighting loads that are present in the plant.
The motor relays trip the associated feeder breaker, 51A and 51B trip the 4 kV main breakers and the neutral relays 51N trip their associated primary breakers. It is common practice to provide a bus transfer scheme to transfer the auxiliary bus to an alternative source in the event of the loss of the primary source.
What kind of fuses do I need for auxiliary power?
There’s a variety of manufacturers who make auxiliary fuse panels that will support anywhere from 6-12 fuse positions, or 6-12 auxiliary power connections—up to 125amps in total. We recommend the fuse blocks and circuit breakers from Blue Sea Systems as they’re durable and easy to set up.
What’s the best way to control auxiliary power?
We also recommend a manual battery kill switch in between that connection. One of the most common ways to control power and properly protect circuits is with an auxiliary fuse block and max-amp circuit breaker.
Do you need a negative bus for auxiliary power?
We also recommend setups with a negative bus, as they provide a very solid ground (important for proper function and protection) and helps eliminate the need for searching for a solid ground to power your electronics. Each auxiliary connection should be protected by a fuse that is as close to the amp draw for the accessory.
