×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

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!

*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

LRG Vs Solid Grounded system

LRG Vs Solid Grounded system

LRG Vs Solid Grounded system

(OP)
I hear my colleague saying Low resistance grounding is selected only because where High resistance system cannot be used (charging current 3Ic is >10A) and there is no great advantage of using it, rather use solid grounded system.

Any comments!

I believe it also provides easy ground fault relaying and lower Arc flash hazard exposure.

RE: LRG Vs Solid Grounded system

I assume you're talking about medium-voltage. Low resistance grounding for low voltage systems <1000 V is generally never done for safety reasons.

Low-resistance grounding at medium voltage allows for selective coordination of ground fault while still greatly limiting ground fault damage compared to solid-grounding.

High-resistance grounding further limits ground fault damage, but it is difficult to coordinate - so when a ground fault is detected the entire system is generally shut down. On HRG systems, ground faults are normally detected based on the voltage instead of current. It works well for limited systems such a generators with a unit step-up transformer. It's less common in industrial systems with extensive medium-voltage distribution. Hybrid sytsems are sometimes used whereby grounding is switched between high and low resistance grounding depending on the fault location.

Dave

RE: LRG Vs Solid Grounded system

High resistance grounding is not suitable for MV distribution systems where there could be extensive cabling. The cabling increases the capacitive leakage currents and thus the earth fault current cannot be limited to 10A or even 25A. IEEE Red book defines High resistance earthing to limit the earth fault current to 25A.
It is popular to limit the earth fault currents to around 300A and this is to limit the possibility of damage to the iron core laminations in motors when the fault happens to be in the stator winding slots.
It is an economical and practical possibility to rewind a motor affected by winding fault but the core damage means expensive repair or rebuilding of core.
IEEE Red book has good discussion on the earthing options for MV systems.

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! Already a Member? Login


Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close