Auxiliary (Control) Power Supply; Potential Transformers And Current Transformers; Ct Wiring Considerations - GE Multilin EPM 2000 Series Instruction Manual

5.1. Auxiliary (Control) Power Supply

The EPM 2000 requires a Single-phase AC / DC Auxiliary (Control) Power Supply to supply
power to its internal electronic circuitry. The
only the Auxiliary Supply connected.
External surge suppressors are necessary in the Auxiliary Supply Circuit for proper operation,
for extreme surge conditions, were the Voltage surges exceed the Auxiliary Supply limits (Eg
Rural areas and outlying areas prone to lightning strikes.
•
Standard: 80 to 270VAC 45 – 65Hz or 100 to 270VDC.
•
Optional: 44 to 300V ac dc
•
Burden (load) < 3VA(Auxiliary)
NOTE 1: The Auxiliary Power Supply may be derived from the voltage signals.
NOTE 2: If you have a 440 v Three-Wire Delta system and a reliable Neutral is not available, a 440v :
240v Supply transformer should be used to provide the standard 240v Auxiliary Supply.
DANGER : Do not feed the EPM 2000's auxiliary power supply
terminals with a voltage greater than the rating marked on the label. The
EPM 2000 will be permanently damaged and GE's Warranty shall be
void.

5.2. Potential Transformers and Current Transformers

Large electrical installations have high voltages and currents which may exceed the direct
connection rating of the meter. In this case, Potential and Current Transformers are used to
precisely "step down" or reduce the voltage and current level to suit the meter rating.
Potential Transformers usually have a full-scale output of 110v ac rms line-line and Current
Transformers, a full scale output of 5A or sometimes 1A.
The PTs (Potential Transformers) and CTs (Current Transformers) must be planned, installed
and tested by a qualified electrical contractor before wiring the meter. The accuracy of the
measurement is determined by the accuracy and phase - shift of the PTs and CTs. Instrument
Class 1 or better PTs and CTs are recommended. Do not use Protection Class (10P10, etc.)
CTs to feed the EPM2000; they have poor accuracy and phase characteristics.
Ensure that the CT Primary rating has been selected so that your normal load variation lies
between 40% and 80% of its full scale. If your CT is over-rated, say if the load is always less
than 10% of the CT Primary rating, accuracy suffers. On the other hand, if the CT is under-
rated, then you may exceed its full-scale and burn out both the CT and the EPM 2000.
5.2.1. PT, CT Wiring Considerations
The PTs and CTs must have adequate VA rating to support the burden (loading) on the
secondaries. You may want to support the Auxiliary supply burden from one of the PTs. CT
wiring can impose additional burden (loading) on the CT. For example, if the CT has a 5 Amp
secondary and the wire resistance is 1.0 Ohm, then the CT has to support an additional burden
of 5VA. If the wiring distance from the CT secondary is greater than stated in Table 3.1, then
the CT could get over-burdened and give large errors. Choosing a 1 Amp CT secondary can
reduce this error. The CT Secondary value must be user programmed into the meter.
The EPM 2000 should be conveniently located for easy connections of voltage (PT) and
Current (CT) signals, the auxiliary (control) supply.
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Setup procedure must first be completed, with
Auxiliary Supply Range:
Sub Meters
.
GE Multilin