×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Long Feeder Cables + Switchgear Line Side Protection

Long Feeder Cables + Switchgear Line Side Protection

Long Feeder Cables + Switchgear Line Side Protection

(OP)
hey folks,

i have a 2000ft cable that feeds a 4.16kV switchgear lineup. the cable has a 1200A breaker at the source end, so it will protect the cable adequately.

my question is this: does my 4.16kV switchgear lineup require a protection device on the line side (breaker/fuse)? are there any references to NEC/CEC that may provide a guideline?
client is suggesting using a load break switch only.

the reason i ask is because i figure the 1200A breaker will do an adequate job of protecting the cable, but what if there is a fault at the switchgear. wouldn't you want a fuse/breaker on the line side of the switchgear to quickly clear any faults and prevent damage to the cable?

RE: Long Feeder Cables + Switchgear Line Side Protection

Why would a fault in the switchgear damage the cable if the upstream breaker is set to protect the cable?

Why couldn't you come up with settings for the upstream breaker that protects both the cables and switchgear?

RE: Long Feeder Cables + Switchgear Line Side Protection

As long as the upstream breaker is coordinated (graded) with the switchgear outgoing breakers, technically the switchgear incomer can be a load break disconnector.

Now a days, breaker panel and disconnector panel costs may not be substantially different. You should go for breaker. If you don't want to provide protection, fine.

RE: Long Feeder Cables + Switchgear Line Side Protection

(OP)
i guess what i meant was, wouldn't you rather have a line side protection device on the switchgear to quickly clear any bus faults on the gear?

in my mind, if i wait for the upstream breaker to operate, won't it take slightly longer? longer clearing times = higher incident energies for arc flash?

RE: Long Feeder Cables + Switchgear Line Side Protection

The only good reason to make the switchgear breaker more sensitive than the upstream breaker is to save a 2000 ft walk to the guy who will have to reset the power, if a fault occurred at the switchgear. On a protection coordination point of vue, both breakers open the same circuit. They may have the same amp rating and possibly the same settings.

RE: Long Feeder Cables + Switchgear Line Side Protection

The current is the same everywhere in the circuit when a fault occurs. Put the same protection setup at both ends of the supply cables and they will both trip in the same time.

RE: Long Feeder Cables + Switchgear Line Side Protection

Having a breaker at the switchgear will allow you to use fast bus protection like bus differential or zone selective interlock. This could significantly reduce arc incident energy.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources