protect the generator from power grid
protect the generator from power grid
(OP)
we have a new plant in our factory it is a steam turbine which driven the generator,and it has it protection device,it`s done by Chinese engineers so they told me that the feeder of power grid should be connected always at same time with the generator while it is supplying the plant,some other peoples told me that we must have a protection device which protect the generator from the power grid like over voltage under voltage over freq. under freq. reverse power etc. so could any one help me in this issue.






RE: protect the generator from power grid
RE: protect the generator from power grid
I may be mincing words but long story short, yes you need protection, and yes, you need to ensure that the waveform produced by your 'generator' matches that on the grid. To do this, you often need some sort of controlling mechanism and the ability to 'lock out' your source until it reaches the rated voltage waveform.
As far as how EXACTLY this is accomplished in applications where you have a turbine, I look forward to some experts weighing in.
RE: protect the generator from power grid
RE: protect the generator from power grid
Isn't simple issue.
Of course it must be covered by utilities requerements.
Are connection to distribution or transsmision grid?
Firstly you must have LOSS OF MAIN protection
1. df/dt or F protections
2. Voltage step protection.
3. Maybe, out of step or pole slip protection.
4. Maybe reverse power protection or directional overcurrent+undervoltage protection.
Difficult case, if you have fast autoreclosere on your connection line. In this case maybe U1<, positive undervoltage will be used.
Hope that help.
Best Regards.
Slava
RE: protect the generator from power grid
For the best information I would refer you to the IEEE guides on generator protection. Or most utilities should have a write up on what is required for interconnection. Other guides can be found on the web sites of protective relay manufactures like SEL, ABB, Basler, or Beckwith.
Also several states have interconnection guides for interconnection to utilities within those states (also good information even if you are not in those states).
For larger generation, in the USA, the power pools may have guides for interconnection.
RE: protect the generator from power grid
Basic devices you should have when connected all the time:
Ground fault protection
Over/undervoltage
Over current
Overspeed
Phase imbalance
Extra devices when connected to the grid:
Synchronous check (to get synchronized in the first place)
Reverse power
Instantaneous overcurrent - Possibly not needed
Frequency - This may not be required as well.
The best method of sychronizing would be to power your plant from the grid and synchronize only the generator. However, I agree it is ok be connected to the grid while it is also supplying the plant. In any case, you need to have a lockout device to be sure your generators voltage, frequency, and phase angle are in sync with the grid before it is closed on the line or it could damage your machine.
What size machine is the generator?
------------------------------------------------------------------------
If it is broken, fix it. If it isn't broken, I'll soon fix that.
RE: protect the generator from power grid
An induction generator is much cheaper and more forgiving and doesn't care very much about synchronization. It must/should be connected to the grid for voltage and frequency stability. It is not traditionally used for co-gen applications but if cost and simplicity is important it may be used for co-gen.
A synchronous generator or alternator will be able to supply all or part of your plant in the event of a grid failure. This would depend on the size of the generator relative to the plant load and the presence of suitable switching.
What size is the generator and what is the plant base load?
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: protect the generator from power grid
This will give lots of information.
Depending on the size of the alternator and also the requirements of the supply company, typically;
Under/over voltage.
Under/over frequency.
Vector shift.
These 3 are as a minimum in the UK.
Larger machines/HV alternators may require.
Neutral Voltage Displacement (NVD)
Directional overcurrent.
Rate of change of frequency (ROCOF).
Mains reverse power.
The genset should have a control system to protect against under/over voltage and frequency and preferably reverse power (motoring), the mains protection can be incorporated into the control system (such as a ComAp, Deep Sea or Woodward modular controller) but the majority of supply companys insist on a seperate stand alone protection module that has a direct trip contact to disconnect the generator from the grid within 0.5 seconds of a mains "disturbance".
I hope this helps, let me know if I can explain further.
Cheers.
RE: protect the generator from power grid
RE: protect the generator from power grid
RE: protect the generator from power grid
for my pinion not bad relay for the LOSS OF MAIN protection
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RE: protect the generator from power grid
It's very common for non-native english speakers, so to speek, to misspell or understand the details in english.
RE: protect the generator from power grid
RE: protect the generator from power grid
Gee, the spell checker in word is much easer to invoke.
This is really a good forum, and I welcome reading about problems that I haven't stumbled into myself. And I perfectly understand that English can be difficult.
I also have problems with Kilo, is it with a "K" or "k". The lower case k just dosen't seem right.
RE: protect the generator from power grid
I use Firefox and it has built in spell check as you type. There are add-on to allow spell checking if you is using IE. If I were trying to write in a foreign language I'd use Word and turn on the spell check for that language. It's not that difficult to spell check one's work if one actually cares about how things look.
RE: protect the generator from power grid
RE: protect the generator from power grid
Siemens have a good protection relay Siprotec 7UM62 but there are a lot more. GE Multilin 789 is also a good and easy one. Futher there are relays from ABB and Beckwith.
And i can recommend you also a Rotor Earth Fault relay these things ar not so expensive and are easy and handfull.
RE: protect the generator from power grid
I'm not sure why this type of criticism bugs me so much, but it does. Especially if it's from someone that doesn't really know what they are talking about, but likes the "image" of professionalism. I used to work for a mid to large electrical engineering consulting firm in which the president of the company was just this type. The more paper and "proper" termonology are the way to show how good you are. I read countless documents that basically said nothing or worse yet, were technically incorrect, but boy did they look professional.
For what it is worth, there is actually a document that specifies correct use of SI units. Check out this link if interested:
http://physics.nist.gov/cuu/index.html
RE: protect the generator from power grid
http://www.selinc.com/sel-300g.htm
RE: protect the generator from power grid
I think we had here some misunderstanding
OP:
"we have a new plant in our factory it is a steam turbine which driven the generator,and it has it protection device,it`s done by Chinese engineers so they told me that the feeder of power grid should be connected always at same time with the generator while it is supplying the plant,some other peoples told me that we must have a protection device which protect the generator from the power grid like over voltage under voltage over freq. under freq. reverse power etc. so could any one help me in this issue. "
Tareksabry, as I understood, you have some generator protection, not important, what company, it;s part of generator supplier.
But you work in co-generation with the grid ( I suggest via GSU, step-up transformer).
Problem isn't generator protection, problem is loss of main protection, that means, dissconnect of grid CB on the feeding SS and fast or slow autorecloser.
Here you have so much options:
Your generator capacity is enough for plant feednig,
isn't enough, that means after decoupling from the grid, you have provide load shedding, etc.
Possible option du-feedeng, to grid and from grid.
All this points are influence on the LOSS OF MAIN protection, in lot of case it's dedicated protection and isn't part of generator protection, in the generator protection we usually use two standard protection : frequency decoupling level and ( if it request by utilities) pole slip/out-of-step.
Best Regards.
Hope that help
Slava
RE: protect the generator from power grid
I have used many GE Multilin Relays and they work well. They will have pretty much any protection you need in them and they are fully configurable with a computer. They also have Ethernet and RS485 connections if you need it to talk to a SCADA system. The good is that it is just one relay. The bad is that it is just one relay, it fails you loose all protection.
I am not sure which relay you would use for your application since I ussually work with Diesel gens but they should have something for your Turbine protection and your Utility Protetion. I would check with your Utility first on what relays they approve for your use.