syncing two generators 1

[roldar]

I'm working in Guinea for an NGO troubleshooting a power problem. The office where I'm working has a 3-phase 30kVA SDMO generator. They are overlaoding it (mainly with AC units). RIght now I'm trying to balance the load but its all in an effort to reduce the blinking lights, beeping UPS's, and clicking voltage regulators. I understand that I cannont squeeze the additional 15kW out of the unit to run everything all the time. I've reccomened cuts and replacement of high demand units in favor of lower demand units. And maybe doing away with a/c units in some place all together. But I'm also looking at adding a secondary unit to kick in when the damand is there.

My question is this: How much trouble is it to install a secondary unit, mainly in the syncronization?

We cannot afford a new 50kVA unit, but could possibly afford a 20 kVA unit. But everything I've found online is the exact same unit (output, manufacurer, etc). But thos are also on the manufacturers websites. The unit would pretty much need to be supersafe and fire and forget as the maintenance and troubleshooting abilities here are lacking. I don't want to reccomend the installiation of a unit that the first time the syncing system goes down and the secondary unit is turned on off phase the whole setup meltsdown or explodes or cooks everything turned on or injures or kills the guy turing on the secnodary unit. I've heard stories about stuff coming online off phase then blowing up and injuring the guy at the switch and don't want to be responsable for it happening here.

 

[ScottyUK]

Normally a synchronising relay or synchroniser performs the actual process of synchronising the generators. An independent check-synch relay, ANSI code 25, is normally employed as an interlock to the synchroniser to prevent the type of event you are concerned about. A contact from the 25 relay is, in principle, wired in the closing circuit of the generator circuit breaker to prevent operation of the closing coils unless synchronous conditions are met. Although there are a few ways of doing this in practice, the key principle is to provide independent oversight of the synchroniser, just in case it has a 'very bad day'.

There are few other things to consider about paralleling generators, mainly relating to load sharing and governor dynamics. I don't do much with small diesel sets but waross will no doubt give you chapter & verse on the practicalities & pitfalls of running two diesel sets in parallel when he sees this post.

Over to you Bill!


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If we learn from our mistakes I'm getting a great education!

 

[davidbeach]

I'm not Bill, but my guess is that it will cost more to parallel a 30kVA and a 20kVA than it would cost to buy a 50kVA. At those sizes you will be far better off putting some of the load on the 30kVA and some of the load on the 20kVA and letting them run independently.

 

[abeltio]

Agree with independent run, very smart idea.

If the synchronization is still required: The bigger generator should be in isochronous operation and the second in droop.



saludos.
a.