Help with negative sequence relay settings

[eeprom]

Hello,
I am working on the relay settings (for the first time) for a 1960 GE generator. I could use some advice on the 46 negative sequence relay settings. According to the GE relay manual, I need to know the K value (maximum permissible heating constant) for the machine before I can derive the relay settings. The problem is that I don't have the K value, and the people who sold us the generator also don't know the K value. Furthermore, the previous owners didn't use a 46 relay in their protection, so I can't refer to their previous settings.
I called GE, and they said that the information was proprietary, and that they wouldn't give it to me unless I hired a GE field engineer. This is an option--a very expensive option. I would prefer to avoid this option if it is possible.
So, is there any way that I can derive the 46 relay settings without knowing the K value? Or is there some way I can derive the K value? Any help here would be appreciated.

thanks

 

[slavag]

Hi Eeprom.
As Dave said to you:
"They will be probably be able to track down the information - eventually.
The k value can vary quite a bit - from 30 down to maybe 10 for very large machines."

Please send us more information.
What is a generator size?
What is a prime mover?
What is a generator voltage?
Are connected directly to grid or via step-up trafo?
What is a load type?
Are generator work continiutly or used as back-up only?
Best Regards.
Slava

 

[eeprom]

1. Who's Dave?
2. Gen. size: 44.1 MVA
3. Prime mover: steam turbine/33.3 MVA (I think)
4. Gen voltage: 13.8 kV
5. Grid connection: step up 13.8 kV to 120 kV
6. Load type: ??? I don't understand this question.
7. Gen duty: Continuous.

thanks

 

[slavag]

Dave ---- DPC, please see your previos Q at the Forum ;-).
In your case load type isn't important, isn't indusrial generator direct connected to BB.
Are you would like use EM relay 46 of GE SGC21A,21B, 21C?
Manual part number GEK 86069J?
Slava

 

[eeprom]

In regards to previous comment, "They will be probably be able to track down the information - eventually." GE's time is prohibitively expensive. This is why I am trying to avoid using GE's services. I'm sure they have the information, but I expect that it will cost me more than the value of the relay.

The numbers you mention correspond to the same relay and manual which I am using. Page 5 describes the tap settings.

 

[ScottyUK]

...but I expect that it will cost me more than the value of the relay.

Will it cost more than removing the rotor, rewinding it, and reinstating it? Add in the value of lost generation too. The relay cost is barely worth consideration in the big scheme of things.


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

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

 

[dpc]

The basic ANSI requirement for "indirectly cooled" steam turbine generators is a k = 30.

If it is something more exotic (direct hydrogen cooled), then the value will be more like k=10.

You should be able to check the ANSI standards from that era to get a pretty good idea.

30 is a reasonable starting point for a 33 MW machine, in the absence of any other information. Any protection will be better than nothing.

Cheers,

Dave

 

[eeprom]

This is a hydrogen cooled system. Where did you find the ANSI standards for K values?

 

[dpc]

For a hydrogen-cooled steam turbine-generator, I'd use a k = 10.

There are ANSI/IEEE standards covering generators. I don't have time to search out the exact standard right now.

 

[slavag]

Well, Eeprom.
For my pinion:
Go on the Dave's recommendation and don't forgot Scotty's post "The relay cost is barely worth consideration in the big scheme of things." I agree with Scotty, cost of relay usually is nothing .
Dave recommend use k=10, that mean your 46 protection will more sensetitive. is O.K.
Regards and Good Luck.
Slava

 

[eeprom]

I'll probably go with a K of 10 because it is very conservative. The lowest K value is 5.

As far as Scotty and his comment is concerned, I don't understand how anyone reading this thread would have gotten the impression that I wasn't going to protect the machine simply because I didn't want to pay GE. Apparently I haven't expressed myself very well. The reason I started this thread is because I am going to use this particular relay, but I would prefer not to pay GE over $5,000 for a 2 digit number.

 

[dpc]

We had a client who got a similar BS response from GE regarding a used GE turbine they were trying to install. I believe this came from GE field services. They eventually contacted the GE Power group at a technical inquiry level and got an answer.

 

[ScottyUK]

As far as Scotty and his comment is concerned, I don't understand how anyone reading this thread would have gotten the impression that I wasn't going to protect the machine simply because I didn't want to pay GE.

It was the comment about the advice costing more than the value of the relay which threw me: in my opinion it is the settings for the relay which are the valuable information, and the relay is just a means of implementing those settings. Of course I can understand totally the reluctance to pay robbers like GE if you can get the information elsewhere. I'm pretty sure they are worse than Siemens-Westinghouse for blatant price gouging, something which is quite an achievement considering the strength of the competition!




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

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

 

[cranky108]

So if ANSI/IEEE has typical K values for more recent machines, where would one look for K values for older small hydro units (Also GE, but probally to old for them to have data)?

 

[dpc]

GE probably still has the data -but rewinds are likely if it is really old. Hydro units are pretty robust, normally. I'd use k=30 if I had absolutely nothing else to go on. Actual value could be more like 40. This is assuming indirect cooling (air).