Paralleling utilities
- Thread starter gregorsc
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Re: Paralleling utilities
Paralleling switchgear can be used in either an open transition or closed transition situation.
Open transition is when the utility circuit breaker opens prior to the generator circuit breaker closing to the bus that feeds the loads (you will have a short power outage in this scenario).
Closed transitioning is when you can have the utility circuit breaker and the generator circuit breaker closed onto the load bus at the same time (you will not have a power outage in this scenario).
It sounds as if you have a Closed transition situation. The paralleling switchgear will normally have all of the control parameters that will allow the generators (Usually multiple generators) to be synchronized with the utility and then closed to the load bus so that both the utility and the generators are operating simultaneously for a short time.
The local utility will need to review and approve the control drawings from the Paralleling switchgear manufacturer to verify that all safety devices are in place to protect their line workers.
Hope this helps
-Ed
Paralleling switchgear can be used in either an open transition or closed transition situation.
Open transition is when the utility circuit breaker opens prior to the generator circuit breaker closing to the bus that feeds the loads (you will have a short power outage in this scenario).
Closed transitioning is when you can have the utility circuit breaker and the generator circuit breaker closed onto the load bus at the same time (you will not have a power outage in this scenario).
It sounds as if you have a Closed transition situation. The paralleling switchgear will normally have all of the control parameters that will allow the generators (Usually multiple generators) to be synchronized with the utility and then closed to the load bus so that both the utility and the generators are operating simultaneously for a short time.
The local utility will need to review and approve the control drawings from the Paralleling switchgear manufacturer to verify that all safety devices are in place to protect their line workers.
Hope this helps
-Ed
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Paralleling utilities
Placing the generator in parallel with the serving utility allows you to test the generator by placing some load on it. It also allows you to perform this test without losing power to the facility. Some facilities cannot tolerate the open transition that Ed described. If they lose power to their equipment, even for the short interval between "utility breaker open" and "generator breaker closed," their production will shut down and that will cost them too much money.
Be sure to get familiar with Article 705.
Placing the generator in parallel with the serving utility allows you to test the generator by placing some load on it. It also allows you to perform this test without losing power to the facility. Some facilities cannot tolerate the open transition that Ed described. If they lose power to their equipment, even for the short interval between "utility breaker open" and "generator breaker closed," their production will shut down and that will cost them too much money.
Be sure to get familiar with Article 705.
O
oliver100
Guest
Re: Paralleling utilities
2. The systems must be synchronized, i.e. the voltages between the respective (generator/utility: A-A, B-B, C-C) phases must be zero.
3. After both conditions were satisfied, then the generator can be paralleled.
After the paralleling you control the load of the generator by the governor (more gas more load).
This is seldomly done for backup/emergency generators. The real load tests are conducted in the factory or on site with banks of resistors.
1. The voltages between phases of the generator and the utility must be equal.
2. The systems must be synchronized, i.e. the voltages between the respective (generator/utility: A-A, B-B, C-C) phases must be zero.
3. After both conditions were satisfied, then the generator can be paralleled.
After the paralleling you control the load of the generator by the governor (more gas more load).
This is seldomly done for backup/emergency generators. The real load tests are conducted in the factory or on site with banks of resistors.
Re: Paralleling utilities
You said "gen-sets" above so your scenario probably involves the paralleling gear to connect 2 or more gensets in parallel to achieve a larger power output. The gear would have the main section with all the controls, relaying, etc. and then a vertical section for each genset with a drawout breaker. You do this for redundancy, reliability and cost savings. For example it could be cheaper to buy (2) 1MW gensets with gear instead of (1) 2MW genset. Also, if that big unit fails you have no backup power available. If one of the smaller units fails you can shed load and still stay online with critical systems.
Often times they want the whole setup to also parallel with utility for peak shaving applications. During high demand (high cost) times they can power most of their load with the gensets and only buy what they need from the utility. Off peak times they can do the opposite or run on utility alone.
You said "gen-sets" above so your scenario probably involves the paralleling gear to connect 2 or more gensets in parallel to achieve a larger power output. The gear would have the main section with all the controls, relaying, etc. and then a vertical section for each genset with a drawout breaker. You do this for redundancy, reliability and cost savings. For example it could be cheaper to buy (2) 1MW gensets with gear instead of (1) 2MW genset. Also, if that big unit fails you have no backup power available. If one of the smaller units fails you can shed load and still stay online with critical systems.
Often times they want the whole setup to also parallel with utility for peak shaving applications. During high demand (high cost) times they can power most of their load with the gensets and only buy what they need from the utility. Off peak times they can do the opposite or run on utility alone.
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Paralleling utilities
That's how you control the sharing of "real power" (i.e., KW). You control the sharing of "reactive load" (i.e., KVAR) by raising or lowering the setting of the voltage regulator.
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