×
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

Difference between Primary protection and Secondary protection

Difference between Primary protection and Secondary protection

Difference between Primary protection and Secondary protection

(OP)
Hi Guys

Friend and I are having a bit of a disagreement on the difference between Primary protection and secondary protection.

He thinks it refers to the difference between primary protection (i.e. feeder breakers) and secondary protection (i.e. transformer backup protection). It could also refer to primary as transmission and secondary as distribution?

Any thoughts? Cheers

RE: Difference between Primary protection and Secondary protection

It probably depends on who you're talking to.

Some people will install fully redundant protection relays, and call one "Primary" and the other "Secondary", with little difference in terms of function or speed of clearing faults.

Some people consider "Primary" to be the fast-acting main protection (e.g., transformer or generator differential) and "Secondary" to be the slower backup protection (e.g., timed overcurrent on the same equipment).

I've not heard primary as being transmission and secondary as being distribution, but wouldn't be surprised if it was used this way somewhere.

RE: Difference between Primary protection and Secondary protection

Over here duplicate systems are frequently referred to as 1st main and 2nd main.

I would suggest you get hold of the single line diagram and have a look at the relay functions associated with primary and secondary protections. That way you don't rely on our speculation.

RE: Difference between Primary protection and Secondary protection

As others have said you can have a number of answers to this.

To give an example, in some of the older subs in our network, the primary protection means the Busbar protection that operates the no.1 trip coil, the secondary operates the number 2 (from a separate battery and CTs). The two schemes are identical in every other way. On the feeders and transformers we call the schemes #1 and #2. It is only Busbar protection that gets this distinction.

The idea was to not get bus section nos and prot scheme numbers mixed up, but most people these days think it makes everything more confusing so it is no longer used.

When a new person joins us and we visit one of these subs, I normally ask what they think primary and secondary means on these panels. Not surprisingly nobody has guessed correctly!

In saying that, most answers given make perfect sense.

The moral of this long winded post is you are probably both right, and you probably won't get anything definitive to help your argument from this forum !

RE: Difference between Primary protection and Secondary protection

(OP)
Thanks guys

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