Stray Currents on HRG?

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What can be causing currents to measured at ~10A on ground system that is on a High Resistance Grounding System (HRG) grid that limits the fault current to 3 Amps?

The currents measured by the HRG are ~3A, but when using an ammeter clamp on the ground elsewhere in the system, the current reading varies up ~10Amps.

Could this be caused by stray currents in the earth from buried pipes or conducting material that came in contact with the grounding grid?

Why would the "stray" current be larger than allowed by the HRG if there is only one grounding sytem grid?
 
UWEE said:
What can be causing currents to measured at ~10A on ground system that is on a High Resistance Grounding System (HRG) grid that limits the fault current to 3 Amps?

The currents measured by the HRG are ~3A, but when using an ammeter clamp on the ground elsewhere in the system, the current reading varies up ~10Amps.

Could this be caused by stray currents in the earth from buried pipes or conducting material that came in contact with the grounding grid?

Why would the "stray" current be larger than allowed by the HRG if there is only one grounding sytem grid?
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One could be harmonic components due to nonlinear power devices, such as ASD's and other retifierd front end devices. If your HRG does have harmonic restriction and your clamp on does not a difference would be shown.

The other could be equalizing currents flowing between areas with different potentials. That could be to a host of different reasons.
 
1. Is your clamp on True RMS?
2. What is the system voltage and configuration?
3. Is there a possibility of down stream ground issues possibly through a load, such as a heater element.
4. Is this a fixed resistor or adjustable?
5. Is the meter calibrated? is the meter on the resistor unit calibrated?
6. Do you have another meter for comparison readings?
 
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