LV generators

[maunsell]

Ok this would be my first time ,so be gently with me.
i am trying to obtain the low down on generator sets and the synchronising of such plant with the mains.i am currently about to underake a desgin on a hospital that currently has an 1 year old 1000 kVa set.We are to extend this and provide the project with another 1000 KVa set in pararell.The existing set offers no synchonising with the mains and no facility to load test.

i am about to enter into discussions with the manufactuer ,but would like to be armed with info. as to how the system should operate, what regulations apply, and generally understand the topologhy. If someone could provide relevant information ,i.e a typical scop/guide or direct me to a useful site.

i look forward to any helpful responses.

regards

Mark

email mark.lewis@fabermaunsell.com

 

[brupp]

Beckwith is always a good source in everything synchronizing. Try

http://www.beckwithelectric.com/infoctr/iichome.htm

and look at the synchronizing section.

 

[peebee]

Don't be too worried about it, maunsell. Your situation is relatively common and straightforward. You need parallelling switchgear, which will have input breakers for each generator, and possibly for future additional generators, and will likely have at least one output distribution breaker. Your new genset can be of a different manufacture than the old one, but you may need to replace more existing controls in order to get the whole package working. Any major generator vendor should be very familiar with what you're trying to do and very willing to give you reasonable advice, and you could probably just do whatever he says and be fine.

But, since you asked. . . .

You may need to replace your existing generator governor in order for it to work with the synch. controls. You may need to provide load shedding (which is usually driven by a frequency relay as detecting frequency dips is much faster than monitoring acutal load). You will likely have additional control wiring run to your transfer equipment in order to control load shedding - depending on length & complexity of wiring, you may want to do this using either discrete contacts or via digital communications. You may have to assign prioritization to your transfer equipment as well. I'd strongly recommend a touch-screen interface for user programming of generator prioritization, load prioritization, etc, but this is somewhat a matter of personal preference.

Typically for emergency genset installations, you want both generators to immediately start. The first one to come up to speed assumes as much load as possible. When the second comes up and synchronizes, it closes to the bus and any remaining load is transferred to it. If load is less than 50%, you can likely "optimize" (shut down) to one generator (double check that, I'm not that familiar with hospital installations).

At least one PLC will likely be provided for master control, and one PLC for each generator control. You may want to consider redundant PLC or relay controls for increased reliability. You may want to consider manual controls, including a synchroscope, for manual synch.

You mentioned load bank testing. You might want to install a separate breaker on your parallelling switchgear for a portable or permanent load bank. If this was a new installation, I'd strongly consider radiator-mounted load banks for each genset, but since your existing generator doesn't have one, it probably makes less sense.

Don't be too intimidated by all this. It'll be a piece of cake.

 

[peterb]

Good stuff, peebee.
In addition to brupp's suggestion of Beckwith, you should check out Basler (synchronizing, voltage regulators) and for sure Woodward (governors, parallel operation). Your genset manufacturer probably has a wealth of info on the subject.
Oh, by the way - don't forget to talk to the utility up front. They will certainly have a lot to say on the subject of paralleling (search for other posts in this forum, there has been a lot of discussion).

 

[redtrumpet]

Also Asco and Thomson Technology for paralleling switchgear and generator controls.

 

[dpc]

I'd just like to throw in a word of caution regarding use of a hospital emergency generator for paralleling operation with utility power. This can be done, but it if the generator was originally intended as an emergency generator for life-safety power, I would think twice before attempting it.

If you are interested in simply synchronizing your two generators together to provide additional operating flexibility, this is a different matter.

But nothing should be done that would reduce the overall availability or reliability of the legally mandated use of the generators for emergency power.

 

[stevenal]

Check IEEE standard 602, also known as The White Book.

http://www.standards.ieee.org

 

[peebee]

Oops, I didn't catch that part about parallelling with the utility. Yup, be careful with that. And I agree, don't do it if these are life-safety generators.

Also, please note that there are three kinds of utility paralleling: 1) closed transition (not really paralleling), 2) momentary (usually less than 100 ms) or 3) continuous. Closed trans probably does not require coordination with the utility. Momentary will require some minor additional protective relaying and coordination with the utility. Continous will require substantial protective relaying and perhaps a different utility contract.

If you're looking at momentary or continuous, you might want to check with the utility to see if you can get an "interruptible" utility rate, which can be much cheaper than the standard rates.

 

[jbartos]

A little chip to maunsell (Electrical) Jul 25, 2002 marked ///\\Ok this would be my first time, so be gently with me.
i am trying to obtain the low down on generator sets and the synchronizing of such plant with the mains.i am currently about to undertake a design on a hospital that currently has an 1 year old 1000 kVa set.We are to extend this and provide the project with another 1000 KVa set in pararell.
///What is the parallel operation going to look like? One at a time or both simultaneously?\\The existing set offers no synchronizing with the mains and no facility to load test.
///This implies that both sets will run in parallel.\\i am about to enter into discussions with the manufacturer ,but would like to be armed with info. as to how the system should operate, what regulations apply, and generally understand the topology.
///Yes, this is recommended with a tape recorder so that you do not forget anything what is said.\\ If someone could provide relevant information ,i.e a typical scope/guide or direct me to a useful site.
///The above posting provided many excellent tips.
1. Additionally, if you parallel two generators, and possibly add any rotating machinery, then the short circuit fault levels will increase. It is necessary to check if the existing buses and switchgear and dowstream power distribution can withstand, interrupt the higher fault levels during the parallel operation of the two sets.
2. Paralleling, synchronization, protective relaying, and associated hardware (communications) can be supplied by the mentioned firm above,

http://www.basler.com

http://www.ge.com

http://www.abb.com

etc.
3. What is the voltage level?
4. What is the prime mover?