15KV Underground distribution and S & C PMH-6 switches for Reliability

[power2engineer]

I am looking at a project to provide reliable power to a compus facility from 2 15KV feeders as source to multiple buildings S & C PMH-6 switch is quite expensive for automatic transfer any alternate solution to reduce number of switches or other vendor's switches which could be cheaper?

 

[Zogzog]

I would look to the main sub for a better solution, adding an auto transfer scheme to the M-T-M breakers in the main sub would eliminate the need for auto transfer at each switch and be a huge cost savings.

 

[racobb]

However if the feeder is the problem, you will need the multiple feeders and local transfer. You can also look at G&W and Trayer for the equipment.

Alan

Democracy is two wolves and a sheep deciding what to have for dinner. Liberty is a well armed sheep!
Ben Franklin

 

[Zogzog]

Good point Alan, redundancy may be needed for the cables. Another question would be is auto transfer a requirement?

 

[alehman]

We recently did a large campus project and used loop circuits with two utility service points and PMH-9's. Operation is manual. One switch in each loop is always open (except with utility company intervention). Fault indicators at each switch help maintenance staff quickly isolate faulted segments.

Alan
----
"It’s always fun to do the impossible." - Walt Disney

 

[trosepe]

Have you looked at the S&C Vista line. We have used them on a dozen college campus 12 and 21KV loop systems. They are low profile (37" high) and have self powered SEL relays on each fault interrupter way. You can get up to seven inerrupters in a unit. They are available in 12.5 or 25 KAIC. They have visible open contacts and grounding positions. The interrupters are in stainless steel SF6 filled tank so they can go anywhere and require little or no maintenance. The campus electricians love them. As indicated above, we also install SEL fault indicators on the loop positions.

 

[power2engineer]

Zogzog, Alan, alehman, Trosepe all thanks a bunch for sharing your expereince and ideas. There is M-T-M transfer at the switchgear but if the feeder is faulted that want help. Atomatic transfer is not a must but would be a nice to have feature.

I will defintely check out vista line and other ideas shared here. Thanks a bunch.

 

[EEJaime]

All the above is very good advice. G & W has a similar line of these SF6 filled switches. That will give you an alternate source and competitive bidding. We have used both up to 34.5 kV and they are reliable, quality gear.