4160 volt transformer terminations
Can anyone explain the advantages or disadvanatage of:
1. live front transformer used with stress relief cable terminations vs.
2. dead front transformer used with elbow connections.
I'm not that familiar with 4160 volt terminations.
With the "load break" elbows you can disconnect the transformer w/o removing the power by using a "hot stick" to remove the elbows. Personally, I have provided pad mount (also refered to a underground transformers because they sit on a concrete pad and both the HV and LV are underground and enter and exit the transformer from beneath entering in to air teminal chambers) and the majority that I supplied were with "bushing well which provides provisions for LB elbows, the actual elbows themselves being supplied by the customer, thats up to 200a. Above that NEMA 2 or 4 hole terminations were supplied on the HV side. I never supplied none load break elbows in 20 years. Maybe it was just by chance that I never got the opportunity to do so.
Originally Posted by steve66
But, this is a fairly good explaintion that I dug up on the WEB:
"A load break when used with a hot stick can be connected or disconnected under load, but can only be used with up to a 250kcmil cable. Think about it…if you had a critical application where power disruptions were extremely costly and maintenance was required on up-stream equipment in, let’s say a non critical area, this product would be great. You could disconnect the load without disturbing the critical portions, perform the maintenance and then reconnect it. Just make sure to take safety precautions, making and breaking electrical connections under load is very dangerous.
The load break elbow is typically not used in man-holes, because it does not allow expansion like the dead break elbow. The construction of the load break elbow does not allow it to be connected to other elbows, but the dead break does."
"A dead break or “hammerhead” can only be disconnected when not under load, this is because you need to actually unscrew a pin to detach it. It would be pretty tough to unscrew the pin with a hot stick and the arc from the disconnected load, if under load, would be pretty substantial.
A dead break allows an increased current rating (up to 600A) and can be used on basically all cable types.
A dead break still provides flexibility during maintenance it just requires a brief outage to allow the splice to be broken. This outage could be scheduled at an off-peak time or after ensuring that all back-up systems were already running and/or transferred to another source such as a generator. I wouldn’t trust a UPS alone in this case unless it was connected to a second source of power like a generator. The amount of time to disconnect the splice and coordinate the outage would cut it real close.
Deadbreak elbows are fairly large, so make sure to check the space restraints of the location you are installing them. If you do run into a space problem, their are various other seperable splices on the market that may be suitable, check with the manufacturers."
The 600 and 900 amp non load break connectors are rather large. The 15 and 25 kv nonload break are much smaller, and are held in place with a bail hold. The explanation of loadbreak from the web sounded kinda perfect world. The 200 amp loadbreaks are great for loop feed applications where some maintanience needs to be done to one transformer, or for doing maint. without switching off the entire line.
Originally Posted by templdl
Anytime you can spec dead front it is a plus for the system. Don't know anyone that wants to open a PMT to see 4160 exposed just a foot or two from their face.
I always try the lead the customer to dead front if they are specific.
Originally Posted by Hv&Lv