The Model 4046 is a frequency adjustable switch mode
current injection source that is used to drive the primary of
a multi tapped coupling transformer to induce variable
voltage and current magnitudes into an earth or passive
load loop at maximum power continuously if required.
Typically the earth test loop / circuit consists of the earth grid
under test connected to a remote earth grid through an earth
path in the ground. To complete the loop, a return connecting
path isolated from earth, usually an ‘out of service’ feeder or
separate injection line is also used. The test current is driven
around the loop by the secondary winding of the Model 4047C
Coupling Transformer which is inserted into the loop.
Frequencies from 40Hz to 70Hz can be selectively generated
by the 4046 to avoid interference with background line
frequency. Voltage drops generated by the injected current
around the earth loop are measured with a frequency
selective multimeter fixed to the current injection test
Measureable results over the test landscape can be profiled with the 4025E or 4031 frequency selective
multimeter. Both the 4025E or 4031 and the 4046 Injection system have a GPS function which is used
for position location and phase synchronization which frees up the need for phase reference cabling
during current split measurements and also provides relative positioning information so that the operator
may choose the best line of potential measurement during EPR tests to avoid mutual coupling/induction.