mge Flashcards
main generator electrical (14 cards)
STATE the function of the 25kV Generator Distribution System
- Supply power from the Main Generator to the switchyard via the Generator Step-up Transformer (GSU)
- Supply power from the Main Generator to the UAT’s for station auxiliary power loads.
- Supply power from the switchyard to the UAT’s for station auxiliary power when the main generator is shut down.
- Provide a means to isolate the main generator from the transmission and distribution system during fault conditions.
STATE the function of the Generator breaker
The generator circuit breaker connects the main generator to the generator step-up and unit auxiliary transformers.
It is also used to isolate the generator for routine maintenance and during casualty situations.
STATE the function of the Generator breaker compressed air system
The generator breaker compressed air system is designed to supply the compressed air required by all three of the pole units associated with the generator breaker
STATE the function of the Generator Step Up (GSU) Transformer
- Steps up 25kv to 345kv for distribution to grid.
* Steps down 345 kv to 25kv for in-house use.
EXPLAIN the operation of the main generator circuit breaker including the cooling system and air pressures used
- Air operated
- Forced air cooled
- Air-blast
- 3700# air is stored and delivered at approximately 490# for operation
- Compressed air surrounding the contacts is circulated through the tubes of the heat exchanger and back to the contact assemblies There are 6 fans, with 3 heat exchangers and 2 circulating fans per pole
EXPLAIN how to place in, or remove from service the main generator breaker air compressors
- Have electrical Maintenance remove lock rods
- System lineup-close flask outlet valves, close control pwr breakers
- Close breakers for compressors
- Start compressors
- Align bkr for remote operation
- Open flask outlet valves
EXPLAIN how to place in, or remove from service the main generator circuit breaker
• Breaker can be operated from 3-pole cabinet.
- This is for MAINTENANCE only!
• Can operate all three phases or each individual phase.
- When in LOCAL all MCB control and indication is lost.
• Kirk Key interlock with generator ground disconnect must be met.
• Normal operation is from MCB
STATE the function of the main generator, exciter, and power rectifiers (SCR bridges), and DESCRIBE their relationships
- Main generator: Converts the mechanical energy of the main turbine to electrical energy for commercial usage and station auxiliary power usage.
- Exciter: Produces the magnetic field used to induce armature voltage in the Main Generator stator
- Power rectifiers: converts AC from the generator to DC for the magnetic field
STATE the high side and low side voltages for the GSU
- High side: 345kV
* Low side: 25kV
DESCRIBE the cooling system for the GSU transformer.
Each transformer has 6 forced oil/forced air cooling units. A Cooling Unit Consists of: -Oil-to-air heat exchanger. -4 fans. -1 oil circulating pump
DESCRIBE the transformer gas control system for the GSU
- Lifts @ 11.5# and reseats @ 8#
- Initiates alarm
- Not a fail-safe mechanism. Designed to limit transformer tank deformation for certain faults. A “huge” fault could still deform or rupture the tank
DESCRIBE the location and type of sensors used to monitor the Main Generator stator temperature
- RTDs are situated between the top and bottom armature bars in each stator slot
- thermocouples are used to monitor the stator cooling water outlet from each set of stator bars
DESCRIBE how the plant is affected if generator breaker cooling is lost
A loss of generator breaker cooling can initiate a turbine setback to 55% power at 5%/min
DESCRIBE how the plant is affected if GSU transformer cooling is lost
After a 30 min delay the plant will experience a set back of 2%/min to 40%.
