480/208/120 VAC(EBI) Flashcards
What is the purpose of the 408/208/120 VAC(EBI) Power System?
The system provides an adequate and reliable source of AC power to:
- Switchyard power circuit breakers
- Battery chargers
- Relay house HVAC
- Lighting
- Other miscellaneous loads
What are the major components of the EBI system?
The system consists of two outside load centers. Each load center contains:
- Incoming 6.9KV switch section
- Transformer section
- 480 VAC automatic transfer section
- Outgoing panelboard section
What are the normal and alternate power supplies to each load center transformer?
STA normal 1TB12
STA alternate 2TB12
STB normal 2TB12
STB alternate 1TB12
What is the purpose of the No-Load Transfer Switch(Selector Switch)?
Allows transfer from the normal 6.9KV power source breaker to the alternate 6.9KV power source breaker.
What is the interlock associated with the No-Load Transfer Switch(Selector Switch)?
The No-Load Transfer Switch cannot be operated unless the associated Fusible Air Interrupter Switch(FAIS) is open.
How is the Selector Switch operated for STA?
- Verify the associated FAIS is open.
- Remove the plug from the operator and insert the operating tool.
- Turn the handle until the desired line(Line 1 or Line 2) appears in the Selector Switch window.
How is the Selector Switch operated for STB?
- Verify the associated FAIS is open.
- Remove the plug and insert the operating tool in the Selector Switch slot.
- Pull out the interlock actuator on the FAIS, raise it to the “Upper” position and release it such that it’s locked in the “Upper” position.
- Turn the operating handle until the desired line(Line 1 or Line 2) appears in the window.
What is the purpose of the Fused Single Throw Air Interrupter Switch?
- Located in line with the Selector Switch prior to the transformer section of the load center.
- Provides a means of isolating the transformer section from the 6.9KV supply.
- Switch is open or closed.
What is the Interlock associated with the FAIS?
When the FAIS is closed:
- The Selector Switch cannot be operated.
- The front door of the incoming line section cannot be opened, where the fuses are located.
How is the FAIS Switch operated for STA?
- Verify the fuse door is closed and latched.
- Ensure Selector Switch is aligned.
- Ensure the key lock is retracted.
- Insert the operating handle.
- Position to open or closed.
How is the FAIS Switch operated for STB?
- Verify the fuse door is closed and latched.
- Pull the interlock actuator out and lower it to the lower position until it locks.
- Ensure the key lock is retracted.
- Pull the handle lock button out.
- Pull the handle lock down to open, or push it up to close.
Describe the STA/STB Transformer?
They are oil filled step-down transformers, 6.9KV to 480VAC, located between the incoming line section and the low voltage Automatic Transfer Switch section of the load center.
What is the purpose of the Automatic Transfer Switch, and what are the component designations?
The Automatic Transfer Switch will automatically transfer from the output of the normal transformer to the alternate transformer if voltage is degraded.
SPA/ATS
SPB/ATS
What conditions will cause the ATS to shift sources, and what are the local indications?
If the voltage on the 480 VAC side of the transformer drops below 80%, and the other source is available, the ATS will shift to the alternate source. The ATS will shift loads back to the normal source 15 minutes after the normal source recovers to greater than 80%(normal seeking).
Panel Indications:
Green light - Loads connected to the normal supply
Red light - Loads connected to the alternate supply
There is a Transfer Test Toggle Switch on the panel also.
What are the loads on Panelboard SPA?
- Battery Charger SYBC-1
- Relay House Air Handling Unit
- Relay House Duct Heater
- Battery Charger SYBC-S
- Relay House Duct Heater for Battery Room A
- Auxiliary Power To PCBs 16-21, and 28-33
- Switchyard Outside Lighting(Panelboard SLA)
