Connecting Neutral Grounding Reactor to Bus Duct

[Abominos]

Hello all,

I'm an intern with a local power utility this summer so let me start by apologizing for my ignorance (just finished my junior year). My supervisor asked me to check with the manufacturer of the neutral grounding reactors we use with regard to how to connect one between a substation transformer and the switchgear when they are connected using a bus duct. If I understand correctly the problem is that there is not a straightforward way to connect the reactor to the bus since the bus is entirely enclosed.

I have contacted the manufacturer and they responded with saying we just needed to make sure to place it with the required clearances but it would otherwise be fine i.e. I don't think they quite understood the problem was how to actually connect to the bus. I followed up but haven't yet heard back. I contacted but have not yet heard from the switchgear rep and will be trying again.

In the meantime I've been trying to read up on switchgear and bus ducting as well as searching to see if anyone else has posted a similar scenario which led me to this forum. I did a search here and read threads on both the NGR's and bus ducts but couldn't find anyone discussing anything similar to my situation so I thought I'd post it and see if any of you have any thoughts on a potential solution or avenue to pursue. Thank you in advance for any light you can shed on the subject.

 

[Marmite]

What voltage are we talking about? It would be unusual in my view for a utility to be running a neutral through a bus duct from a transformer to the switchgear. At anything above low voltage the switchgear is typically 3 pole.

Regards
Marmite

 

[Abominos]

Thanks for the reply! I believe this is on the low side of the transformer so if I remember correctly it's 15kV possibly 25kV, sorry I'm not at work atm so I can't check. I may have used the wrong term for the reactor. The way my supervisor explained it, the reactor is there to shunt a surge, say from a lightning strike, to the ground only instead of putting all of the current into the ground the reactor being an inductor opposes the rapid change in current and so it limits what is actually put into ground. I hope that clears up what I'm looking to do and I'll check again tomorrow with some of the other engineers (supervisor is out this week).

 

[Abominos]

I just realized after posting that I am likely mistaken about the placement of the reactor as it wouldn't make sense to be on the low side, at least I don't see that it would since it wouldn't be between the transformer and a surge at that point. I apologize as this is all new to me so I'm still trying to figure out how all the pieces go together, switchgear is still rather opaque to me. I do know that it's 115kV coming into the substation. Thanks again!

 

[LiteYear]

I think your supervisor might be confusing you. If it is indeed a neutral grounding reactor, it is connected between the secondary neutral point and ground. As Marmite says, it would be unusual for the neutral to be in the bus to the switchgear. The neutral should be available straight from the transformer.

Neutral grounding reactors are actually primarily there to deal with grounding faults on the secondary. Controlling a lightning surge is really the domain of other devices (commonly called lightning arrestors or surge arrestors).

 

[Abominos]

Thanks LiteYear and Marmite very much for your help. I have checked and it is indeed the case that the neutral is inside the bus duct going to the switchgear in this instance. One of the engineers was mentioning that they could potentially change that and run a bushing out from the transformer to get the reactor connected but what my supervisor was having me check was if anyone had ever had any experience with trying to instead connect the reactor at the throat or possibly modify, ie cut into, the duct itself or something in order to make the connection. It is a bit of a unique setup so he was just having me feel around to see if perhaps anyone had done something similar to this.

Thanks again!