Frame Leakage Protection 

By on

Image
Frame Leakage Protection Principle
While not as popular as it once was, frame leakage protection does still have some use in some circumstances.  In essence frame leakage is an earth fault type protection.  A current transformer installed in a connection from the frame to earth monitors  any fault current and operates an instantaneous relay. 

The fault measuring connection is the only link to earth.  All other connections, including the frame of any switchgear or controlgear assemblies are insulated from earth. 

The main reason for using frame leakage to its ability to detect low levels of fault current.  An example would be a d.c. rail  traction system, where the return rail is insulated (in addition to the switchgear) and by the use of frame leakage protection it is possible to detect high impedance faults away from the switchgear.

In practice it is invariably difficult to fully insulate any item of equipment from earth.  Resistance values of 10 ohms or so would be typical. 

Tip: while insulating the entire switchgear frame,  care must also be taken to use insulating cable glands and in ensuring that no inadvertent earth connections are made.

With the inclusion of transformer neutral earthing, generators, double and sectioned bus bars implementation of frame leakage becomes more complex.  Modern numerical relays are cost effective and provide a large number of features, making them an attractive alternative to the implementation of frame leakage.



Steven McFadyen's avatar Steven McFadyen

Steven has over twenty five years experience working on some of the largest construction projects. He has a deep technical understanding of electrical engineering and is keen to share this knowledge. About the author

myElectrical Engineering

comments powered by Disqus

  1. naban's avatar naban says:
    4/18/2013 4:16 PM

    If we fix a relay to each of the feeders and one for main switchboard frame if a fault develops in any of the feeders only that feeder will trip,otherwise all feeders won't get supply/power


Comments are closed for this post:
  • have a question or need help, please use our Questions Section
  • spotted an error or have additional info that you think should be in this post, feel free to Contact Us



The ac resistance of conductors

In a previous article I looked at the dc resistance of conductors and in this article we turn our attention to ac resistance. If you have not read the...

Motor Insulation

Insulation on a motor prevents interconnection of windings and the winding to earth.  When looking at motors, it is important to understand how the insulation...

myElectrical - Cable Sizing Tool Upgrade

Our IEE cable sizing was wrote a few years ago and had become rough around the edges. I thought it was time to give the tool a service. Unfortunately when...

Post Editing Tips

If you at all familiar with programs like office and outlook, then adding and editing posts is pretty straightforward and intuitive.  However, there are...

Large Hadron Collider

The 27 km, Euro 6 billion  Collider lies on the border between France and Switzerland, took nearly 30 years to complete.  Some of the lofty goals for the...

Earth Electrode Resistance

Earthing of electrical systems is essential for the correct functioning and the protecting of life and equipment in the event of faults.  The earth electrode...

Thomas Edison

American inventor Thomas Alva Edison was born in Milan, Ohio on February 11, 1847. He was the youngest of seven children and received little formal schooling...

Are We Losing Professional Integrity

I have been thinking recently that there appears to be less professional integrity around than when I first started my career in electrical engineering...

Paternoster Lifts

These lifts were first built in 1884 by J. E. Hall and called a paternoster ("Our Father", the first two words of the Lord's Prayer in Latin) due to its...

Michael Faraday (the father of electrical engineering)

Famed English chemist and physicist Michael Faraday was born on September 22, 1791, in Newington Butts, a suburb of Surrey just south of the London Bridge...

Have some knowledge to share

If you have some expert knowledge or experience, why not consider sharing this with our community.  

By writing an electrical note, you will be educating our users and at the same time promoting your expertise within the engineering community.

To get started and understand our policy, you can read our How to Write an Electrical Note