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Recently the commissioning part of our company started a new project in a gas turbine power plant with six individual power generation units, each 160 MW.
Each power unit includes one auxiliary medium voltage switchgear to supply internal consumptions. Also common switchgear is considered for power plant common consumers and a long interconnection cable (approximately 700 m) between each MV and common panel for emergency using. This interconnection path is used instead of incoming units when their incomings can not be energized via normal path.
One day, the head of electrical commissioning group called the office engineers to help. He said,” we can not run unit 2 switchgear via normal path, and we have decided to use interconnection of common switchgear. But when we close the related circuit breaker, its relevant sensitive earth fault trips it”.
The setting of mentioned relay is similar to the other same relays in output feeders and it is adjusted at 2 A ( in primary side ) for all sensitive earth fault; because that medium voltage system is resistance grounded with maximum 10 A earth fault currents. Also all those earth fault relays are connected to special core balance current transformers.
He said they have never had any problem with other output feeders. They didn’t have enough time, and wanted permission to increase the setting of earth fault relay in commissioning duty. They knew well this activity may be accompanying a great risk.

Can you take that risk of operation?


BEST REGARDS
MSJ




Creative thinking is enjoyable,Then think about your surrounding things and other thought products. http://electrical-riddles.com
 

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Beyond my realm,buddy.I'm just a contractor.
As are most of us.
I appreciate that MSJ posts these questions. It's just that they are SO far out of the scope of most of us here it is not even funny.
I think he needs to find an electrical engineering board to get the feedback he is looking for.

Many guys here have a heavy theory background and can relate to some of what is asked. I am kind of weak in the real theory department so I don't get any of it.
 

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I do not see the normal connection of the feeders and the nomenclature and drawing is not a standard format I normally deal with. On issue could be the CT polarity, phasing of the alternate path, or the configuration of the CT is such that with the alternative path the current is additive (I do not see the CT locations).
 

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Try whacking the flux capacitor with your lineman pliers. That ought to do it.






Seriously, I don't deal with these types of things much. I knew Brian would be the guy to help on this one.
 

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"If that doesn't work, hook up your transponder to the dilithium crystals...that'll work for sure.:icon_confused: "

That's what I used to do, but those crystals are makin' me weak lately.:eek:

Best Wishes
 
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