ETS-Lindgren HI-3604 ELF Survey Meter - Manual (Page 27)

HI-3604 Manual Page -- 19
4.0 POWER FREQUENCY FIELDS
The HI-3604 finds application in numerous circumstances
involving 60-Hz fields. A prime example of the HI-3604's utility
is evaluation of electric and magnetic fields in the vicinity of
electric power lines. In this case, the electromagnetic field
environment surrounding a typical power transmission line can
be visualized through Figure 4-1. This figure illustrates a single-
circuit, three phase power line consisting of three separate
electrical conductors, each having an impressed voltage which
is 120 degrees out of phase with its neighboring conductors.
A shield wire may be present above the three phases of the line;
this wire, which is grounded, acts as a preferred point for
lightning strikes which could, if unprotected, strike the current
carrying conductors, potentially damaging and removing the line
from service for repairs. A double circuit line would consist of
two sets of the three phase conductors.
Figure 4-1