Thermal Image
Thermal Image
(OP)
Hi,
Perhaps you can help me.
How does one determine what settings to install into a generator protection relay for the case of the thermal image protection function?
I presume it starts with the gen-set manufacturer, but what information do i request from them? Thermal overload curves?
The Sepam protection relay manual seems to indicate different heating and cooling time constants to be set, a continuous time current parameter determined by that heating constant, and it seems to take into account harmonics (contribution to heating) etc
So my point is, it sounds complicated to set the function up. And I'm not sure what info i need from the genset manufacturer, as I'd like to get all the information at once rather than keep going back to them for additional data that I didn't know I'd need the first time around.
Thanks,
John.
Perhaps you can help me.
How does one determine what settings to install into a generator protection relay for the case of the thermal image protection function?
I presume it starts with the gen-set manufacturer, but what information do i request from them? Thermal overload curves?
The Sepam protection relay manual seems to indicate different heating and cooling time constants to be set, a continuous time current parameter determined by that heating constant, and it seems to take into account harmonics (contribution to heating) etc
So my point is, it sounds complicated to set the function up. And I'm not sure what info i need from the genset manufacturer, as I'd like to get all the information at once rather than keep going back to them for additional data that I didn't know I'd need the first time around.
Thanks,
John.






RE: Thermal Image
And it is also the first time that somebody wants to protect a generator with a thermal image function.
This function can be "simply" used for protecting transformers and motors whose operating conditions are stable. Anyway my opinion is to avoid a thermal image whose reliability should be demonstrated. I prefer thermal sensors.
A generator can operate in very different conditions. What algorythm could really calculate its thermal condition?
A generator never overheats if it operates within the limit of its capability curve:
1) The stator limit is respected because the generator has been correctly sized considering the maximum power production of the prime mover.
2) the rotor limit is respected by the exciting system if it has been correctly set
3) the overflux is controlled by a dedicated protection(59/81)
4) the negative sequence is controlled by a dedicated protection (46)
In conclusion, I suggest to avoid using the thermal function to protect a generator but to set correctly all the other protections.
RE: Thermal Image
Differential prot
Over current prot
Earth fault prot
REF
Neg sequence
Over voltage
Under voltage
Voltage controlled over current etc..
The normal prot for the thermal heating is winding tempr prot as I have come across so far.
Subramanain
RE: Thermal Image
RE: Thermal Image
Sometime the overflux function is also indicated as 59/81.
Please note that overflux is not the same as over-excitation, because you can reach that in particular voltage and frequency conditions.
Anyway the question of Jbond was how to set the thermal image function to protect a generator. My opinion is not to use that. and yours?
RE: Thermal Image
For transformers and induction machines, over-excitation and overflux would be essentially the same thing. For synchronous machines, there can be some distinction. The device number, though, is commonly referred to as over-excitation protection. The IEEE definition more accurately calls it "volts per hertz" (though I would think it "Volts per Hertz" with the proper name based units capitalized).