Previous in Forum: VAR Flow Control   Next in Forum: Question About VFD/VSD AC Drives Input
Close
Close
Close
18 comments
Rate Comments: Nested
Active Contributor

Join Date: Feb 2014
Posts: 10

Steady State Current Of NGR

08/14/2014 5:59 AM

What is steady state current of NGR and what is use of it in NGR ?

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

Join Date: Mar 2007
Location: by the beach in Florida
Posts: 33392
Good Answers: 1817
#1

Re: Steady state current of NGR

08/14/2014 6:45 AM
__________________
All living things seek to control their own destiny....this is the purpose of life
Register to Reply
Guru
United Kingdom - Member - New Member

Join Date: Aug 2010
Location: Resting under the Major Oak
Posts: 4347
Good Answers: 181
#2

Re: Steady state current of NGR

08/14/2014 7:31 AM

There shouldn't be a steady state current.

This sounds very like homework.

__________________
The reports of my death are greatly exaggerated.
Register to Reply
Guru
Engineering Fields - Electrical Engineering - Been there, done that. Engineering Fields - Control Engineering - New Member

Join Date: Dec 2008
Location: Long Island NY
Posts: 15600
Good Answers: 981
#3

Re: Steady State Current Of NGR

08/14/2014 8:44 AM

A Natural Gamma Ray (NGR) is a very high energy, massless, neutrally charged particle. Without a charge there will not be any electric current regardless of the flux density until this ionizing radiation interacts with some detecting media (gas). Then it depends on the detecting media and which region [ion chamber, proportional counter or Geiger-Muller] the bias field imposes on the media.

__________________
"Don't disturb my circles." translation of Archimedes last words
Register to Reply
Guru
India - Member - New Member

Join Date: Sep 2009
Location: Temporarily at Ashburn, VA
Posts: 2744
Good Answers: 164
#4

Re: Steady State Current Of NGR

08/14/2014 10:03 AM

A neutral-grounding -resistor (i assume you mean this) i thought, carries current for a short time. This is an adiabatic process, and is quite different from the steady-state rating. So, in my mind, the two ratings can't be related linearly or in some simple way. i am curious to learn from other experts here.

__________________
Nothing worthwhile can ever be taught, it can only be learnt.
Register to Reply
Guru
Engineering Fields - Electrical Engineering - Been there, done that. Engineering Fields - Control Engineering - New Member

Join Date: Dec 2008
Location: Long Island NY
Posts: 15600
Good Answers: 981
#6
In reply to #4

Re: Steady State Current Of NGR

08/14/2014 10:46 AM

If we are talking about a neutral grounding resistor (I hate undefined acronyms) then the steady state current will neither be steady or zero. Assuming (another word I hate) that a power distribution fault is not happening, the current flowing through this resistor will be from two possible sources.

One of these sources will be a ground loop from the circuit path. This is impossible to determine due to the lack of information given by the OP and I just do not feel like dealing with Maxwell's equations today.

The other source will be the thermal current production known as the Johnson-Nyquist noise. As the name implies, this will be a chaotic current that every resistor produces. Due to the chaotic nature of this current a measurement bandwidth of frequencies must be selected to calculate this value.

__________________
"Don't disturb my circles." translation of Archimedes last words
Register to Reply
Power-User

Join Date: May 2010
Posts: 146
Good Answers: 2
#5

Re: Steady State Current Of NGR

08/14/2014 10:44 AM

As per standards steady state rating NGR is meant for the temperature rise. Neutral Grounded Resistor shall operate under ground fault condition for more than of 90 days per year and /or it to keep the temperature rise below 385 degree. Current rating will be different for low resistance and High resistance NGRs

Register to Reply
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 32175
Good Answers: 839
#8
In reply to #5

Re: Steady State Current Of NGR

08/14/2014 12:29 PM

<...operate under ground fault condition for more than of 90 days per year...>

That would be one dangerous installation!

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Power-User

Join Date: May 2010
Posts: 146
Good Answers: 2
#12
In reply to #8

Re: Steady State Current Of NGR

08/15/2014 12:42 PM

Yes it is dangerous. But NGR should capable for withstanding that.

Register to Reply
Guru
United Kingdom - Member - New Member

Join Date: Aug 2010
Location: Resting under the Major Oak
Posts: 4347
Good Answers: 181
#9
In reply to #5

Re: Steady State Current Of NGR

08/14/2014 8:20 PM

What standards would they be?

__________________
The reports of my death are greatly exaggerated.
Register to Reply
Power-User

Join Date: May 2010
Posts: 146
Good Answers: 2
#13
In reply to #9

Re: Steady State Current Of NGR

08/15/2014 12:43 PM

Please refer IEEE 32

Register to Reply
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 32175
Good Answers: 839
#7

Re: Steady State Current Of NGR

08/14/2014 12:26 PM

A1) Zero

A2) It doesn't have one.

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Power-User

Join Date: Jan 2010
Location: Hyderabad
Posts: 343
Good Answers: 22
#10

Re: Steady State Current Of NGR

08/15/2014 8:10 AM

An NGR will have to deal with the third harmonic currents circulating in the system due to generator or transformer magnetising currents or triplen harmonics due to VFDs / Thyristor panels in the system or simple stray currents circulating in the system through the system neutral.

These are steady state currents and cause heating in the NGR. That's how the NGR will have steady state rating (needless to say much much less in magnitude) as well apart from short time rating.

__________________
Raghunath
Register to Reply
Guru

Join Date: Jul 2007
Location: Commissariat de Police, Nouvions, occupied France, 1942.
Posts: 2599
Good Answers: 77
#11
In reply to #10

Re: Steady State Current Of NGR

08/15/2014 12:28 PM

So why don't those currents stay in the neutral, Boss? Why do they pass through the NGR if there isn't a fault?

__________________
Good moaning!
Register to Reply
Guru
India - Member - New Member

Join Date: Sep 2009
Location: Temporarily at Ashburn, VA
Posts: 2744
Good Answers: 164
#14

Re: Steady State Current Of NGR

08/16/2014 12:21 PM

Some views here have left me shaken. i have always thought that any current flowing to earth is undesirable, and steps must be taken to quickly isolate the faulty circuit so that the cause of such a fault is located and eliminated. Now to think that a steady-state current can flow for what can only be an unproductive purpose, is incomprehensible to me.

Dumb maybe, but would like some elementary clarification.

__________________
Nothing worthwhile can ever be taught, it can only be learnt.
Register to Reply
Power-User

Join Date: May 2010
Posts: 146
Good Answers: 2
#15
In reply to #14

Re: Steady State Current Of NGR

08/17/2014 5:15 AM

If you read IEEE 32, it will be clarified.

Register to Reply
Guru
India - Member - New Member

Join Date: Sep 2009
Location: Temporarily at Ashburn, VA
Posts: 2744
Good Answers: 164
#16
In reply to #15

Re: Steady State Current Of NGR

08/17/2014 7:24 AM

Regettably, i have no access to a copy. So i will have to wait for someone to explain to me. Perhaps you can summarise for me?

__________________
Nothing worthwhile can ever be taught, it can only be learnt.
Register to Reply
Guru
India - Member - New Member

Join Date: Sep 2009
Location: Temporarily at Ashburn, VA
Posts: 2744
Good Answers: 164
#17
In reply to #16

Re: Steady State Current Of NGR

08/17/2014 8:49 AM

Wow, here is what one page from a Google search shows

i still can't believe this ! Thank God this is not my field

__________________
Nothing worthwhile can ever be taught, it can only be learnt.
Register to Reply
Guru
Engineering Fields - Electrical Engineering - Been there, done that. Engineering Fields - Control Engineering - New Member

Join Date: Dec 2008
Location: Long Island NY
Posts: 15600
Good Answers: 981
#18
In reply to #17

Re: Steady State Current Of NGR

08/17/2014 9:49 AM

This is why I hate to answer power distribution questions. Only people properly trained and authorized should ever touch power distribution equipment. Those people authorized and risking their lives to do this work, rely on a proper design that will not kill them. CR4 provides neither training nor authority to work on power distribution equipment. As stated in our FAQ, CR4 is not a homework cheat site. It is likely the OP is too lazy to do their own homework (not all homework is scholastic) to answer their curiosity because Google and other search engines can obviously find this information.

__________________
"Don't disturb my circles." translation of Archimedes last words
Register to Reply
Register to Reply 18 comments
Copy to Clipboard

Users who posted comments:

Alanvaderi (4); Crabtree (1); kvsridhar (4); PWSlack (2); raghun (1); redfred (3); SolarEagle (1); TonyS (2)

Previous in Forum: VAR Flow Control   Next in Forum: Question About VFD/VSD AC Drives Input

Advertisement