How to reduce current in grounding wire?

[janaj1]

During thermography survey it was found that grounding conductor for single core armored cable gland was hot. Current in grounding 16 sq. mm conductor = 50 amps. Gland is made of aluminium, gland plate is made of brass. Current in power cable 300 amps.
Could you please advice how to reduce current and prevent heating of grounding conductor?

 

[charlie b]

I don't know anything about the type of cable you are describing. But if you are saying that the Equipment Grounding Conductor has any current at all, let alone so high a current, then something inside the load fed by this cable is shorted to the external metal parts of the load. The EGC is designed to carry no current at all at any time in its entire life, unless and until there is a fault within the equipment. Turn it off immediately. Take it out of service until it can be inspected and repaired.

 

[K8MHZ]

During thermography survey it was found that grounding conductor for single core armored cable gland was hot. Current in grounding 16 sq. mm conductor = 50 amps. Gland is made of aluminium, gland plate is made of brass. Current in power cable 300 amps.
Could you please advice how to reduce current and prevent heating of grounding conductor?

Are both ends of the armor grounded?

Grounding cable is made to nullify effect of inducted currents in power line. If they are grounded on both ends you will get condensator between core and shield of a cable that will create reactive currents. On short power lines you should ground only one side (for. i.e. you have power cable (10.5 KV 3 MW) leading from generator to its connection cubicle on a system you ground it on cubicle end only)that is because the re is no significant voltage drop trough core co there will be practically no voltage drops and you can consider that other end is protected with grounding also. But when you have a large power lines like in distribution networks they are grounded on both ends. The reason for it is that if you let cable running for lets say 200KM and ground it on both ends the difference in potential may brake isolation due to over voltage (as someone mentioned above). Induction of lines is calculated so it can usually nullify capacitor effect of such system because of reactive currents of induction and capacity are compensating it selves (+jD -jD = 0) if they are equal.

http://www.eng-tips.com/viewthread.cfm?qid=186838&page=10

 

[brian john]

You need to inspect all down stream distribution for the source of this current.

You did not list the voltage and if you had ground fault protection.

I would look for neutrals grounded downstream from the main neutral bond, be these intentional or accidental.

I would inspect the site generator (if you have one) to see if the neutral is bonded to ground, depending on your ATS configuration.

I would arrange an outage and megger the neutrals (with the neutral isolated from ground at the main service.

Now if this is a conductor between the utility and you main service, the current may be unavoidable due to utility rules (grounding the neutral at the transformer) and Local Codes (NEC.....) requiring ground the neutral at the service.

 

[bphgravity]

Section 250.6 - Objectionable Current, may provide some guidance for this matter...