Recent content by sobeys81

It is for Substations actually. This desigination is kinda new to me.

Hi , I am sure some of you gurus work in utilities at a managerial or supervisor level. I will be interviewed for an Engineering Specialist position for a local distribution company. I come from a consulting engineering background. I was wondering, if you guys could explain me this role in a...

Hi My thread consists of two questions: Q#1 : What value of fault current is considered for CT saturation calculations: IEEE std is not very clear on this. A) ASymmetrical RMS 3 Phase fault Current(RMS)- 1/2 Cycle B) Symmetrical RMS 3 Phase fault Current(RMS)- 5 Cycle Q#2 In the past, I...

Thanks Gentleman, So here is what I understood : Generator will be allowed to operate with a ground fault which even might lead to catching fire. I had an impression that to run a HRG system the requirements are that there should be a electrician to detect and isolate the fault. Is this all...

Appreciate the response cranky, Kindly eloabroate on alarm functionality during a ground fault

I was away gentleman. But I have some more dilemans to get over with : There is so much concern about stator ground fault protection during a ground fault. When we issue a Alarm on a gen ground fault, what is the next course of action by the operator. I am sure a lot of you see this...

Thanks all. Cranky108, I would appreciate a little more explanation on your statement regarding 27 N3 function and why it should be shut down. After probably reading everything on the planet on stator ground fault issue, I came across certain basic rules and I will share them with you. Please...

thanks davibeach. It helped.

Thanks Davidbeach, I did not phrase my question properly. What Iwas trying to get to was that, if I have a differential protection on generator and if a ground fault occurs with in generator winding than it will shut down the system right away, so neutral grounding resistor does not play any...

Thanks all again. This is a again a question of how it is done in traditional practice. If a breaker has a differential protection 87, then having a low resistance or a high resistance groundded system make a difference in terms of stator damage during an earth fault ? Would it make a...

Thanks Odlanor. Is it also a standard practice to shut down the generator excitation during a ground fault as well, if it is a stator grounding fault ? Why I thought so because if gen. excitation is still on it will keep feeding the fault. Is this correct.

Thanks davidbeach "Ground faults start off doing damage to the winding insulation. If the current is kept low enough, that's all that will happen." So this will happen because of overvolatge ? not because small 50 A ground fault current ? Thanks

Please dont mind, if my question is stupid. I have heard this terminology stator core damage so many times. A fair size generator on 24 Kv carries 20,000 A full load current, so what damage 200 A ground fault current can do to a stator. And if it does, I am sure I am missing some thing big...

Thanks trospe, Cables at 4.16 kV are unshielded and rated for 100% insulation. Does 100% and 133 % apply to unshielded cables as well ?

we will trip. Cables at 4.16 kV are by default rated for line to line voltage. What other issue i should be concerned about. So you would call it a LRG system or a HRG system ? Thanks