Advantages of Surge Arrester on Sec.of T/F or Downstream Switchgear
Advantages of Surge Arrester on Sec.of T/F or Downstream Switchgear
(OP)
Hi,
Could anybody advise me the advantages of having a surge arrester on secondary bushing of a transformer(44/13.8 KV) or the switchgear which is being fed from this.
I think, the reasons could be on lines of switching voltage or lightening protection.
I would appreciate a word.
Thanks
Could anybody advise me the advantages of having a surge arrester on secondary bushing of a transformer(44/13.8 KV) or the switchgear which is being fed from this.
I think, the reasons could be on lines of switching voltage or lightening protection.
I would appreciate a word.
Thanks






RE: Advantages of Surge Arrester on Sec.of T/F or Downstream Switchgear
RE: Advantages of Surge Arrester on Sec.of T/F or Downstream Switchgear
RE: Advantages of Surge Arrester on Sec.of T/F or Downstream Switchgear
Bahram7
www.Simtech-Intl.com
RE: Advantages of Surge Arrester on Sec.of T/F or Downstream Switchgear
In my case, the HV side of transformer has already bushing arresters. This is an industrial installation.
The sec.(13.8 KV) is fed to a switchgear. Now, what I am trying to get to basically at a theoretical level is that having either a surge arrester at switchgear bus or sec. of transformer or at both locations, which would make sense.
How this is theoretically justfied.
I understand this in case of a lightening strike, the HV bushing arrester will divert it to ground but how about the switching phenomena. How switching can impact low voltage side.
If you are aware of some literature available that can explain a theoretical basis for interaction of a switching transient and surge arrester. Please advise.
Thanks
RE: Advantages of Surge Arrester on Sec.of T/F or Downstream Switchgear
Vacuum circuit breakers can create significant switching transients due their rapid arc quenching. So the transients can originate on the low voltage side as well as the high side.
Proximity is the number one factor when applying surge arresters.
Try this:
http://se
RE: Advantages of Surge Arrester on Sec.of T/F or Downstream Switchgear
I will go through this pdf document and probably will help me getting a better picture of the whole switching mechanism.
I have another question to add here. I got this info from utility for the primary of transformer.
Base MVA-100
69 KV
I(3Ph)-4000 A
I(1Ph)-3183 A
Pos. seq. Impedance- .091+J.0325
Zero Seq.Impedance- .07+J .25
I was wondering, how come zero sequence reactance so much higher than all other parameters?
Is there any explanation to it.
Thanks
RE: Advantages of Surge Arrester on Sec.of T/F or Downstream Switchgear
RE: Advantages of Surge Arrester on Sec.of T/F or Downstream Switchgear
It is a feed from utility, and I dont know, if their system is resistance grounded or not. But mostof the utility substations are solidly grounded and I dont know why utilities ground them in this fashion might be a trend thing I guess.
Do you think, is there any other reason for zero sequence impedance to be higher than positive sequence impedance ?
RE: Advantages of Surge Arrester on Sec.of T/F or Downstream Switchgear
Do you think the zero sequence you got from the utility is of the primary of the transformer or could it be the Thevenin equivalent of the impendence seen by the primary of the tranformer? If the latter then that could explain it.
RE: Advantages of Surge Arrester on Sec.of T/F or Downstream Switchgear
Thanks. I wonder, why these small things could be so complicated at times.
Utility normally provides:
3 Ph( SC)
1Ph (SC)
and
Z(+ve)where Z(-ve) will be same as z(+ve)
Z(zero Sequence)
This line this is coming to our installatin is certainly from a sec. of a 115 kv/69 KV transformer.
AS our input is 69 KV.
I guess that means this sec. of utility transformer is resistance or reactance grounded. This is the only way to justify.
Anyways,
How utilities decided that they will have transformers solidly grounded or resistance grounded ?
I understand this issue in industrial and commercial installations but how this works in case of
utilities ?
Thanks