Using Clamp on meter to measure 4.16kV current

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broadgage

Senior Member
Location
London, England
If the MV/HV conductor is insulated such that it may be touched safely, then I see no harm or danger in useing a clamp on ammeter to measure the current in said conductor.
It would be foolhardy with a bare conductor, and wont work with a shielded conductor.
The meter measures the magnetic field around the conductor to determine the current, it does not "know" what the voltage is in the circuit.

I believe that the 600 volt ratting of the instrument refers to voltage measurements, or to current measurments on bare conductors.

I have certainly measured the current in insulated 11KV conductors useing a standard meter, neither I nor the meter suffered any harm, and I would not consider my actions to have been in any way foolish or dangerous.
 

mcclary's electrical

Senior Member
Location
VA
If the MV/HV conductor is insulated such that it may be touched safely, then I see no harm or danger in useing a clamp on ammeter to measure the current in said conductor.
It would be foolhardy with a bare conductor, and wont work with a shielded conductor.
The meter measures the magnetic field around the conductor to determine the current, it does not "know" what the voltage is in the circuit.

I believe that the 600 volt ratting of the instrument refers to voltage measurements, or to current measurments on bare conductors.

I have certainly measured the current in insulated 11KV conductors useing a standard meter, neither I nor the meter suffered any harm, and I would not consider my actions to have been in any way foolish or dangerous.



I beg to differ, you got lucky
 

WastefulMiser

Senior Member
Location
ANSI World
Can a typical clamp on meter rated for 600V usage be used to measure current on an 4.16kV MV circuit. Obviously you would never want to try to measure 4.16kV voltage with this 600V meter, however can you use it to measure current since you are only looking at the magnetic field from the current?

Standard practice for MV (5-38KV) switchgear to use 600V CT's.
 

mxslick

Senior Member
Location
SE Idaho
No one said bare conductors and I really doubt anyone was planning on getting that close to a bare conductor.




Hmm, how are you measuring that?

The higher the load you try to place on that 'induced voltage' the lower it will fall.


No one said insulated conductors either so who knows? :grin:

As for the voltage around an energized "kv class" conductor, insulated or not, there are several references to flashover distances, vertical electrical fields for various lines (example at 69kv under a transmission line, near-ground vertical fields range from 1-1.5 kv/m) and safe apporach distances. Many of which have complex equations that I have no idea how to transfer in proper format to a post here.

All references from the "Standard Handbook For Electrical Engineers", 13th ed. Donald G. Fink and H. Wayne Beaty. A great (but expensive) book that goes into great detail on many subjects including properties of insulators and conductors.

Finally, there are rules regarding safe approach distances for energized MV/HV conductors, insulated or not. If there was no safety issue, why the rules?

Sometimes common sense has to take charge over hard and fast scientific analysis of a situation. :grin:

There is equipment out there rated for use at the MV/HV levels...if it's not necessary then why is it made and in use by most POCOs?

I do agree with the higher load/lower voltage part.
 

mxslick

Senior Member
Location
SE Idaho
If the MV/HV conductor is insulated such that it may be touched safely, then I see no harm or danger in useing a clamp on ammeter to measure the current in said conductor.
It would be foolhardy with a bare conductor, and wont work with a shielded conductor.
The meter measures the magnetic field around the conductor to determine the current, it does not "know" what the voltage is in the circuit.

I believe that the 600 volt ratting of the instrument refers to voltage measurements, or to current measurments on bare conductors.

I have certainly measured the current in insulated 11KV conductors useing a standard meter, neither I nor the meter suffered any harm, and I would not consider my actions to have been in any way foolish or dangerous.


I don't care how well insulated a conductor may be, at MV/HV levels all it would take is one microscopic pinhole or cut in that insulation to jump enough voltage and current to kill you. And I know of NO rules that would allow you to touch even an insulated MV/HV conductor without full PPE including voltage-rated gloves with liners.

But let's put safety issues aside, and if you're using a meter rated to 600v, how do you KNOW the current measurement at 11kV is even accurate? Ever consider that the higher potential could saturate the core of the current sensor and affect the accuracy? How about the electrostatic field around all MV/HV conductors? How do you KNOW that those fields aren't somehow affecting the accuracy of the meter?

Like I said in my post above, there are instruments DESIGNED for measuring current and voltage on MV/HV. There is IMHO NO EXCUSE to use anything else when the proper gear is available. If your company can't afford to buy it, then they should rent it, contract out to have someone who has it, or stay away from the MV/HV stuff.

Zog has it right on in his post (#14) Read it and heed it!! :grin:

Edited to add: As for the belief that the voltage ratings apply only to measuring voltage (true) or current around bare conductors (assumption on your part) I wonder what the meter's manufacturers (Fluke for example) would say about all this?
 
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kwired

Electron manager
Location
NE Nebraska
Can a typical clamp on meter rated for 600V usage be used to measure current on an 4.16kV MV circuit. Obviously you would never want to try to measure 4.16kV voltage with this 600V meter, however can you use it to measure current since you are only looking at the magnetic field from the current?

Nobody has answered the OP question of whether this meter will measure the current. The OP has stated that you obviously would not want to try it but was wondering if the meter would read the current - assumed he wanted to know if the reading would be fairly accurate I know I want to know just out of curiosity.

Most people have only talked about how dangerous this practice would be. If a trained lineman that knows how to work on energized bare overhead lines, is properly insulated, and he were to clamp one of these meters around a line will it display a fairly accurate reading of the current in the conductor?

I don't think the meter will smoke or blow up in his hand, where is the other point of voltage potential needed for this to happen? Same reason why birds can land on the line and nothing happens to them - they are isolated from other points of different voltage potential.
 

realolman

Senior Member
Nobody has answered the OP question of whether this meter will measure the current. The OP has stated that you obviously would not want to try it but was wondering if the meter would read the current - assumed he wanted to know if the reading would be fairly accurate I know I want to know just out of curiosity.

Most people have only talked about how dangerous this practice would be. If a trained lineman that knows how to work on energized bare overhead lines, is properly insulated, and he were to clamp one of these meters around a line will it display a fairly accurate reading of the current in the conductor?

I don't think the meter will smoke or blow up in his hand, where is the other point of voltage potential needed for this to happen? Same reason why birds can land on the line and nothing happens to them - they are isolated from other points of different voltage potential.


I think that the clamp on works similarly to a transformer, only the laminated core is hinged so it can be opened and closed... and the conductor is a one turn winding. The lines of flux surrounding the conductor cut across the core and induce a current on the "secondary" of the meter, causing a reading.

I think the lines of flux around the conductor caused by the current woud be the same regardless of the voltage.
 

kwired

Electron manager
Location
NE Nebraska
I think that the clamp on works similarly to a transformer, only the laminated core is hinged so it can be opened and closed... and the conductor is a one turn winding. The lines of flux surrounding the conductor cut across the core and induce a current on the "secondary" of the meter, causing a reading.

I think the lines of flux around the conductor caused by the current woud be the same regardless of the voltage.


Kind of my line of thinking also. Any meter designed to measure this is probably the same basic principle and the differences are insulation to protect the user and not necessarily the meter.
 
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