Small Generator Protection - Backup for Grid Faults 2

[mLp85]

Hi All,

Interested in people's views on which method is better for providing backup protection at a generator for grid faults.
i.e Distance or Voltage controlled Overcurrent ?

Multiple small generators in parallel, each with their own protection relays.

 

[davidbeach]

"Better" is a very vague and subjective term. One person's "better" could be somebody else's "what the heck were you thinking?"

But in general, what's the local practice? What is your backup protection backing up? If looking out onto a transmission system where you're probably backing up distance elements you might find distance easier to coordinate, but if you're in a distribution system that's full of overcurrent protection you'll probably find it more difficult to coordinate back up distance elements.

When one this sentence into the German to translate wanted, would one the fact exploit, that the word order and the punctuation already with the German conventions agree.

-- Douglas Hofstadter, Jan 1982

 

[FreddyNurk]

What's the load and arrangement look like?

I've seen VCO used for feeders in islanded systems as 'normal' protection practice using pure overcurrent for feeders doesn't behave so well with tiny machines. That scenario may not apply to what you're doing, particularly if you're connected to a larger grid rather than being the only source on the network.

EDMS Australia

 

[dpc]

For smaller generators, straight undervoltage is a a very reliable and fast means of detecting system faults and tripping the generator offline. This is based on sensing utility side voltage and opening the utility tie or tripping all units. If you are trying to carry plant load on the generators, it gets more complicated. The voltage-controlled OC is normally too slow be anything other than a backup. This is assuming interconnection at the distribution level. At transmission level, think about direct transfer trip.

 

[RRaghunath]

Agree with David Sir.
It all depends on where these generators are connected and what kind of protection is existing for outgoing feeders from that bus??
If it is a distribution bus that these generators are connected to and the outgoing feeders have only Overcurrent protection (no distance protection), the Voltage Controlled Overcurrent protection will be the appropriate choice.

R Raghunath

 

[wcaseyharman]

Just thought I’d add the I agree that it depends on the system you are connected - transmission I use distance elements and on the DG I’m currently working on voltage restrained overcurrent was more appropriate.