Generator fault
Generator fault
(OP)
Hello,
What happens on a diesel generator when there is a fault between the generator output terminals and the line side of the generator breaker? Specifically, how is the generator shutdown or does it just run to failure?
I am thinking about a large 480V, 1800kW self contained genset.
Thank you in advance for replies.
What happens on a diesel generator when there is a fault between the generator output terminals and the line side of the generator breaker? Specifically, how is the generator shutdown or does it just run to failure?
I am thinking about a large 480V, 1800kW self contained genset.
Thank you in advance for replies.





RE: Generator fault
Differential protection may or may not provide protection, depending if the breaker is in the protection zone.
Many sets in that size range do not have differential protection.
If the fault is to ground, ground fault protection may or may not see the fault, depending on the type of protection and the location of the CTs.
Ground fault protection will generally be for protection of loads beyond the breaker.
An exception may be an impedance grounded set with monitoring of the current to ground.
Basic ground fault protection may be incorporated in the generator circuit breaker and will not see the fault.
The last time I was involved in the purchase of a set in that size range, I requested differential protection. My request was ignored by the financial department.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Generator fault
RE: Generator fault
Your application, such as standby, prime or parallel to grid all have a possible impact on how any protection will function and what really is required.
Modern multi-function relays, like an SEL 700G could go a long way in providing very good protections for your generator, but depends on how the generator is installed, grounded and who develops and implements the protection scheme.
If you provided some additional details you may get some better answers, likely your best solution is to hire a local engineer that has experience in generator protection and local codes/regulations.
Here is a link to a paper by Beckwith regarding generator protection, https://www.beckwithelectric.com/docs/tech-papers/...
Basler also has some good papers on the subject but their new website sure makes it hard to find www.basler.com
And depending where in the world you are there may be others, but I'm assuming US or somewhere close based on your voltage and rating
Hope that helps, MikeL.
RE: Generator fault
RE: Generator fault
I've seen a 5 kVA tower light generator burn until nothing flammable is left on the generator side, the drive engine kept running! I guess that's how these small gennys are.
RE: Generator fault
the built in protection is somehow aligned to the breaker protection curve, that's why I have never seen an external filed differential protection on a diesel genset.
RE: Generator fault
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Generator fault
Ditto on a 25kVA 480V 3ph generator. The copper melted out and ran onto the floor around the generator. The customer reported that the fire department was afraid to go near because it was throwing balls of flaming copper. Once the copper had finished departing, they got close enough to hit the stop button.