Protection

[pithpal]

Could any body plz advise protection approach for dealing with utility,
some literature available on web in regard to co-gen applications.
I beleive there are some experts here on this. Any piece of word would be appreciated.
Thanks

 

[dpc]

Sorry, you're going to have to take the time to write a specific question that makes sense.

 

[davidbeach]

You can find some good material at

http://www.basler.com/html/dwntech.htm

(though I may not be entirely unbiased). I'm sure that the other relay manufacturer's would also have useful material. Rather than trying to list them,

http://home.att.net/~john.horak/

is a page that all power engineers should have bookmarked and includes links to at least 27 relay manufacturers.

 

[waross]

Have you asked your utility what their standards and requirements are for co-generation protection?

 

[pithpal]

OK dpc
Please see my question below:

we have a 500 kw co-gen at 600 V, which is still at design stage, actually we have to connect to existing distribution switchgear which is being fed from local utility. As waross said, discussing with local utility,
we will do that but what basic protection scheme can I go for, at this stage I need to get a basic understanding of
single line diagram involved. Plz advise where I can find some literture available on some basic schemes.
Thanks

 

[waross]

A very bare minimum would be
Reverse Current protection,
Over current protection,
Fault current protection, and
Acceptable Syncronizing gear.
The most basic system that I have seen was installed on a set of 2 600 KW sets and 3 350 KW sets., Prime power for a small community.
1> Fault current and overload protection.:
Provided by a circuit breaker. Further overload protection was provided by the "Dead Rack" setting in the engines fuel injection pump, which limited the maximum power output of the engine to 600 KW.
2> Reverse power protection was provided by a reverse current relay and a shunt trip in the main breaker.
3> Syncronizing was with a syncro-scope and manual closing of the main breaker.
There are a lot more desirable features which you will probable choose to add in the end. This will give you a very bare minimum to build on by adding other features.
yours

 

[davidbeach]

Purchase a copy of IEEE Std 1547. If you are familiar with those requirements your discussions with the utility will go much better than otherwise.

 

[ScottyUK]

The protection relay manufacturers have some reasonable application notes for this sort of application. They're obviously specific to a product, but the principles are very similar across the different manufacturers.

Protection functions you may care to become familiar with, in addition to those listed by waross, would be some form of zone protection (differential or REF) for the generator, and loss of grid connection (vector shift or ROCOF). In the UK, loss of grid protection is loosely referred to as 'G59' protection after the Electricity Associaition document G59/1 which details the requirements. Google on any of 'G59 protection', 'ROCOF', or 'vector shift' will find a lot of information.

The following document has some interesting discussion, although it is obviously biased heavily toward UK practice:

http://www.dti.gov.uk/renewables/publications/pdfs/kel00235.pdf

----------------------------------

I don't suffer from insanity. I enjoy it...

 

[dpc]

http://www.beckwithelectric.com/infoctr/techpapers/IntrConn.pdf

This might help a little, in addition to the other good comments above.

 

[DiscoP]

You could also look at the literature on the Areva MiCOM P941 relay see

http://www.areva-td.com

My first step would be to ask the utility about the protection they would like you to have.

 

[mc5w]

Cummins peddles cogeneration switchgear for use with their generators and these are based on Basler's cogeneration relay which combines the protective functions that you need. These packages allow you to do both manual and automatic synchronising. Your utility might want to review the schematic diagram and relay features for these cogeneration packages but they are pretty cut and dried. Alledgedly, Basler's relay is smart enough to know when a line is deenergized from the other end when an arcing fault occurs so that the Basler relay will also trip out.

Similarly, inverters for interactive solar generation include a relay that disconnects from the line when there is a power failure and can sense when 1 or more inverters are the sole source of power. Some of this is done with voltage sensing and some of this is done with impedance sensing. That is, the line impedance that a solar inverter sees changes dramatically when the utility opens its circuit breaker or fuse.