Previous in Forum: Soft-Starting Solenoid Coils   Next in Forum: Automatic Voltage Regulator (AVR)
Close

Comments Format:






Change Mode
Close

Subscribe to Discussion:

CR4 allows you to "subscribe" to a discussion
so that you can be notified of new comments to
the discussion via email.

Close

Rating Vote:







Add Vote
9 comments
Rate Comments: Nested
Gigabolt
Associate

Join Date: Jan 2009
Posts: 26

Gen Set Neutral Connection

08/09/2009 12:45 PM

Hi all

i am actually in a project to install two 415Vac genset at plant. 4pole ACB is suggested to be used at the genset switch gear. I was wondering that what will be the consequence if more than 1 neutral is connected to the load when the genset is in synchronized mode? (Normally i only operate two syn genset with 1 neutral from the master).

What is the solution, should i use neutral earth resistor? or can i just install the neutral connection from genset directly to the earth main terminal.

need some help here...
Register to Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Good Answers:

These comments received enough positive votes to make them "good answers".
3
harry potter
Power-User

Join Date: Nov 2008
Location: India
Posts: 333
Good Answers: 6
#1

Re: gen-set neutral connection

08/09/2009 1:02 PM

Hi!

Yes , you are right - 2 neutrals should not be used in parallel. Connecting 2 neutrals in parallel shall crfeate the circulating currents between the 2 gen set windings, undedr earth faults or short circuit conditions, or under unbalanced loads. This may cause the burning of the widings.

If possible, Normally , contactors are used for switching on or off the neutral . Only one contactor shall be ON - master DG 's neutral shall be earthed. While neutral of 2nd DG set shall be floating. so, even though 4 pole ACBs are used in DG panel, in the synchronising panel, neutral contactors may be used.

__________________
 Exploring the Science of Electricity
Register to Reply Good Answer (Score 3)
No more Good Answers.
shrekf
Member

Join Date: Feb 2010
Posts: 5
#9
In reply to #1

Re: gen-set neutral connection

05/08/2010 2:07 AM

Hi,

Yes , you are right - 2 neutrals should not be used in parallel. Connecting 2 neutrals in parallel shall crfeate the circulating currents between the 2 gen set windings, undedr earth faults or short circuit conditions, or under unbalanced loads. This may cause the burning of the widings.

Thats was last year thread...

Just wonder what is the neutral tripping characteristic when circulating current happen... Thks
Register to Reply
sb
Guru

Join Date: Mar 2007
Posts: 2550
Good Answers: 103
#2

Re: Gen Set Neutral Connection

08/10/2009 12:12 AM

As HP said don't connect the two neutrals directly.

http://www.geindustrial.com/Newsletter/spring05multiple.pdf

http://www.cumminspower.com/www/literature/technicalpapers/PT-6006-GroundingAC-2-en.pdf

http://cr4.globalspec.com/thread/35491/Neutral-Ground-Connection

__________________
 Fantastic ideas for a Fantastic World, I make the illogical logical.They put me in cars,they put me in yer tv.They put me in stereos and those little radios you stick in your ears.They even put me in watches, they have teeny gremlins for your watches
Register to Reply Off Topic (Score 5)
A. Choudhary
Participant

Join Date: Aug 2009
Posts: 4
#3

Re: Gen Set Neutral Connection

08/10/2009 2:15 AM

Preferably should neautral of each Gen set be earthed separately to work s floating earths.

Thanks
Register to Reply
Gigabolt
Associate

Join Date: Jan 2009
Posts: 26
#4

Re: Gen Set Neutral Connection

08/10/2009 2:54 AM

Thanks for the goos answer Mr. Harry potter,

may i ask in what circumstances that we need to use restricted neutral earth resistor?
Register to Reply
harry potter
Power-User

Join Date: Nov 2008
Location: India
Posts: 333
Good Answers: 6
#5
In reply to #4

Re: Gen Set Neutral Connection

08/10/2009 3:35 PM

Hi !

it seems you have combined 2 parameters -

restricted - meant for restricted earth fault relay

neutral resistance - meant for neutral grounding resistor

Normally, neutral grounding resistor is used for installations above 5 MVA to reduce the level of earth fault currents.

restricted earth fault relays are useful for parallel operations of DG sets - as they are directional relays. & the fault in the specific dg is located by the restricted earth fault relays.

__________________
 Exploring the Science of Electricity
Register to Reply
Gigabolt
Associate

Join Date: Jan 2009
Posts: 26
#6
In reply to #5

Re: Gen Set Neutral Connection

08/18/2009 8:46 AM

thanks again Harry potter.
Register to Reply
Gigabolt
Associate

Join Date: Jan 2009
Posts: 26
#7
In reply to #5

Re: Gen Set Neutral Connection

08/18/2009 8:53 AM

Hi Harry Potter

Another question for enlightenment:

how do we connect the restricted earth fault relay to each dg? should i connect before or after the neutral contactor in neutral terminal.

i believe it has 4 pole: 3 pole for each phase and 1 pole for neutral.
Register to Reply
Anonymous Poster
#8
In reply to #7

Re: Gen Set Neutral Connection

08/18/2009 11:33 AM

dear,

According to me, best position of the semnsing CT would be at the just out going terminal of the alternator neutral lead. since, this relay is for protection of the alternator, & under all logics - operations, this ct position shall sense the fault correctly.
Register to Reply
Register to Reply
Have a Different Question?
9 comments

Good Answers:

These comments received enough positive votes to make them "good answers".
Copy to Clipboard

Users who posted comments:

A. Choudhary (1); Anonymous Poster (1); Gigabolt (3); harry potter (2); sb (1); shrekf (1)

Previous in Forum: Soft-Starting Solenoid Coils   Next in Forum: Automatic Voltage Regulator (AVR)
You might be interested in: Neutral Density Filters, Receptacle Testers, UV Filters

Advertisement

Got Something to Say?
Ask a Question
Start a Discussion

Search this Forum
Electrical Engineering:
Go

CR4 Sections
Aerospace
BioMech & BioMed
Chemical & Material Science
Civil Engineering
Communications & Electronics
Education and Engineering Careers
Electrical Engineering
General Discussion
Instrumentation
Manufacturing
Mechanical Engineering
New Technologies & Research
Software & Programming
Sustainable Engineering
Transportation

Site Directories
Forum Directory
Blog Directory
User Group Directory
RSS Feeds

CR4 Rules of Conduct
CR4 FAQ
Site Glossary

Who's Online (74 right now)
Show Members
Advertisement