Generator dissipation resistance. 4

[Okpower]

I am involved in a 20 MW Generator specification and installation project. I would want to know information about excess power dissipation resistance for generators.
is it a important issue in power generator control or what??
Thanks in advance

 

[Marmite]

Do you mean a load bank?
Regards
Marmite

 

[waross]

Over power is generally avoided by the proper implementation of a governor to control and match the input energy to the load requirements.
I saw one attempt to run a small generator (about 50 KiloWatts) at 100% output and use a load bank to dissipate the energy in excess of load requirements.
The system design was not based on sound engineering principles and was an expensive failure in more than one aspect.
The project may some day be the subject of a post in the "Most Outrageous" thread in Engineering history.
If you are trying to dissipate any great percentage of the energy from a 20 MW generator, you may be able to comfortably warm a small lake and add a vacation resort as a spin-off business. I boiled a lot of water doing a load test on a diesel set 1/1000 the size of your prospective generator. That was a 20 kilowatt set, compared to your 20 Megawatt set.

Bill
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"Why not the best?"
Jimmy Carter

 

[Marmite]

I've heard of load banks being used to govern small scale hydro generators less than say 100kW where mechanical governing of the water flow and generator output is too expensive, but not anything on the 20MW scale. As Waross indicates, it would waste an extraordinary amount of energy.
Regards
Marmite

 

[ScottyUK]

Could this be a badly worded reference to the dissipation factor or tan [δ] of the windings by any chance?


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

 

[Okpower]

Actually, as Scotty says, it was a bad reference. The real question is How electrical generators are used for pre-heating gas products in a gas processing plant. So my interest is to find information about this issue, (how electrical generators are used for this process stage??)

 

[edison123]

Okpower

Are you referring to CHP (combined heat and power) generation ?

 

[ScottyUK]

Pre-heating in a gas plant? Not sure.

Our sister site is a fairly big gas processing plant and I'm not aware of any electrical generators in the conventional sense on that facility, although there is a turbo-expander or two.

Or is this just a big electric heater, a giant kettle element for want of a better description? Have you got an overview P&ID of the plant that you could upload?


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

 

[sberbece]

The long story short is: gas plants usually use the gas turbine as prime driver of the electrical generator, because there is a lot of gas around. Unfortunately, the gas turbines don’t have remarkable efficiency, meaning, they waste/release a lot of heat into the atmosphere.
On the other hand, the gas plant process requires heat to “cook” the gas and take out from it water, CO2, etc, through evaporation and controlled condensation.
In order to utilise some of the heat generated by the gas turbine, it is used a heat exchanger installed on the exhaust “pipe” of the gas turbine.
The heat exchanger transfers the heat from the exhaust gases to a heat transfer medium, which could be oil or water. In many gas plants I’ve seen oil used as transfer medium. But when big gas turbines are involved, usually the transfer medium is water which expands, becomes steam and it is used to drive a steam turbine, then part of the steam released by the steam turbine is used to heat the gas process.

So, recuperating the heat from the gas turbine, it improves the overall efficiency of the gas turbine and saves some gas being burned separately to generate heat required in the gas process.

Regards,
Stefan

 

[Okpower]

Thanks for your replys and sorry for my delay.
Now I am clearer about this issue. As additional information in a gas plant sister of my new project, the gas turbogenerators are used 50% in the oil heating for processing....this is a headache for the electrical operations plant, because they have to generate more power just to heat the oil...and the remaining power is just for export. But...operations personnel rule and they electrical personnel just obey.

 

[Okpower]

...the process i was asking was the one answered by Sberbece...thanks