ETS-Lindgren HI-3627, User Manual

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Example Applications of the HI-
3627
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Residential Ground Currents
A phenomenon, which recently received attention in regard to
residential magnetic fields, is the flow of earth currents via plumbing
lines or telephone cables buried beneath the home. In some cases, it
has been noted that 60 Hz magnetic fields exist within a home, even
when the home is not using any electrical power (the circuit breakers
have all been turned off at the main electrical service box of the home).
This observation has, in some cases, been related to the flow of
currents beneath the home on pipes or cables. It is not unusual for
currents related to other neighbors' use of electricity to flow back to the
electrical supply via low resistance paths. These are formed by metal
plumbing pipes or wires used for telephones as opposed to the
electrical system neutral wire. In such cases, it is possible to measure
magnetic flux densities within the home even though the power to the
home has been shut off.
Ground Faults
As mentioned earlier, current can exist in pipes and heating ducts or
anything metal in the house. This gives rise to an interesting
application for the HI-3627; detecting leakage currents from
appliances. For example it was noted that the fields around a water
pipe leading from a dishwasher changed dramatically when the
dishwasher was run. It was later found that the dishwasher was
defective and allowed excessive ground currents to flow. The same
principles apply to industrial and power distribution situations.
Pipe Inspections
It was noted that the buried pipes leading to fire hydrants tended to
concentrate the currents flowing in the ground from power distribution
leakages. The field from this current could be detected and measured.
It was also noted that the field would vary uniformly as the operator
walked along the pipe. The field would, however, exhibit significant
variations at points on the pipe where there was a break or a large