ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Top Posters(30 Days)
Potseal 11
Recent Posts
600 KW 120/208 3 Phase Y protection
by SteveFehr. 07/23/17 09:46 AM
1913 American Electrician's Handbook
by gfretwell. 07/20/17 01:08 PM
Green House wiring
by ghost307. 07/20/17 09:10 AM
Permit Snafus...AHJs and Contractors Jump in
by HotLine1. 07/18/17 08:06 PM
New in the Gallery:
SE cable question
Popular Topics(Views)
239,260 Are you busy
174,689 Re: Forum
167,090 Need opinion
Who's Online Now
0 registered members (), 62 guests, and 11 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#129419 - 02/28/05 04:58 PM what really is an ungrounded system?  
unsaint32  Offline
Member
Joined: Aug 2004
Posts: 15
eden prairie, MN, USA
Q 1) What is the purpose of ungrounded system. Is it not to trip the circuit breaker when

the first fault occurs? (for more controlled deactivation?)

Q 2) In a grounded system, having one conductor connected to earth provides the reference

for steady voltages supplied to loads. How is stable voltage accomplished in an ungrounded

system?

Q 3) Actually, there is no such thing as an ungrounded system, right? (Because an ungrounded

system is capacitively grounded.. whatever that means)


Thanks for your answers

Sung


Tools for Electricians:

#129420 - 03/01/05 06:00 AM Re: what really is an ungrounded system?  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,217
SI,New Zealand
Sung,
Welcome to ECN, [Linked Image]
Most Electrical systems throughout the world have a reference to Earth.
This is mainly for Safety reasons.
It is so that there is a limit on the Line to Ground voltage.


Let's face it, these days if you're not young, you're old - Red Green grin

#129421 - 03/01/05 08:20 AM Re: what really is an ungrounded system?  
pdh  Offline
Member
Joined: Jan 2005
Posts: 354
I wouldn't trust an ungrounded system where the primary has a higher voltage than the secondary to be very stable. Impedance grounding is generally adequate for a one fault tolerant system. And you'd need that grounding point to set an alarm to know where there is a fault.

I wouldn't even trust an article 411 system (411.5(A) requiring it to be ungrounded) unless it is isolated with a grounded electrostatic shield between primary and secondary, or has 2 transformers with an intermediate grounded loop at the final secondary voltage.



Member Spotlight
electure
electure
Fullerton, CA USA
Posts: 4,260
Joined: December 2000
Show All Member Profiles 
Featured:

2017 NEC and Related
2017 NEC
Now Available!

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.010s Queries: 14 (0.002s) Memory: 0.7520 MB (Peak: 0.8777 MB) Zlib enabled. Server Time: 2017-07-24 00:53:56 UTC