×
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

145kV ferroresonance

145kV ferroresonance

145kV ferroresonance

(OP)
What is meant by ferroresonance on 145 kV air break disconnectors and what is done to limit it? Also what is meant by busbar switching capability on the same thing?

RE: 145kV ferroresonance

I don't know about the ferroresonance part.

Re busbar switching: especially in double busbar stations, one can transfer from one bus to another without opening the breaker, i.e.

to on-load transfer from BB1 to BB2 when the breaker is closed:
close BB2 disconnect switch
open BB1 disconnect switch

as you see, switches need to have a switching capability.

RE: 145kV ferroresonance

Ferroresonance is a condition that could occur in power distribution (even transmission, I guess) system when the long line or cable capacitance coincides with inductance of transformers such that when the 3 phase transformers are single phased while lightly loaded, could cause severe over voltages (that could set off the surge or lightening arresters and blow fuses /operate OCPD).

According to Standard Handbook for Electrical Engineers (McGraw Hill), this is phenomena, which is rare, is not well understood but it seems to be resolvable by making sure that all 3 phases close at the same time. The air break isolator switches that may not close all phases simultaneously could cause problems.

A disclaimer: I am not expert in HV transmission, but the above statement is technically correct. I have come across and resolved one such situation in MV distribution system once.

RE: 145kV ferroresonance

Martechman,

Could you please clarify the term “air break disconnector” or describe this device?

The reason of my question is because typical air disconnect switches are designed only for isolation after open the system with current breaker devices (i.e. Circ Bkr, Circ Switcher, load breaker device).

Standard disconnect switches do not have interrupting capacity no even to open a short line or withstand the inrush current of a transformer without the help of additional power device. However, for substation busbars without load, disconnect switches could be used for some isolation or transfer bus operation since there is not significant charging current accumulated in the system.

Ferroresonance, Ferranti effect or other type of severe overvoltages in disconnect switch could lead to catastrophic effect.

Even though the enclose information is not for 145 kV, this enclose video provide a view of the arching current created in a disconnect switch.

http://images.google.com/imgres?imgurl=http://www....


RE: 145kV ferroresonance

 
IEEE C57.105-1978 §7.1 — Ferroresonance is a phenomenon usually characterized by over-voltages and very irregular wave shapes and is associated with the excitation of one or more saturable inductors through capacitance in series with the inductor.  Intentional and unintentional single-pole switching may often be the initiator of ferroresonant incidents.  Anecdotally, ferroresonance at subtransmission and transmission voltages seems to be able to effortlessly launch local-bus VTs half way to the moon.  
  

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