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 (e) Make external connections to meter as shown in manufacturer's
instructions. The connections should be made by working from right to left.
This ensures complete connection of meter to its LOAD circuit before LINE
voltage is applied. Disconnection of meter should be made in reverse order.
(f) For connections of pulse initiators, refer to manufacturer's
instructions for particular type of end device being operated by the pulse
initiator.
2. COMMON ELECTRICITY METERING PROBLEMS. Problems often encountered in the
field while metering electricity fall into four categories: wrong meter,
meter incorrectly wired, multipliers not calculated correctly, or the meter is
not calibrated.
l
2.1 Wrong Meter. This problem occurs when the meter is incorrectly specified
for the circuit. A common example of this is when a two stator meter is
specified for a four wire wye circuit. The meter is often wired as if the
circuit is a delta circuit. However, if the phases are even minimally
unbalanced, the current flowing through the neutral wire will not be metered
and the readings inaccurate. SOLUTION: Consult the manufacturers literature
and specify the proper meter for the circuit.
2.2 Incorrect Wiring. It is estimated that between 5 to 10% of the
electricity meters on navy bases are incorrectly wired. There are several
ways the wiring can be wrong.
2.2.1 Current leads, potential leads , or instrument transformers could be
reversed or out of rotation or phase. The phase angle between the current and
the voltage for each phase to be wrong, resulting in erroneous readings by the
meter. SOLUTION: Ensure meter IS wired correctly. Determine the nature of
the load being metered and estimate its power factor. Then use a power factor
meter on the incoming potential and current wires to determine if the meter is
reading the estimated power factor.
2.2.2 Blown Potential Fuses. If fuses protecting potential transformers
(PTs) are blown, the meter could be missing one or more phases of the load and
running at 1/3 or 2/3 of normal speed. SOLUTION: Ensure that fuses for PTs
are not blown. On most panel mounted meters, each PT circuit has a small
light that, when lit, indicates that the circuit is operating properly.
2.3 Incorrect Multipliers. The multipliers have been incorrectly calculated,
resulting in the register readings being multiplied by the wrong numbers.
This often occurs when meters have been switched to a new location with
different sized CTs or PTs, or when a meter has been repaired and the register
changed. SOLUTION: Ensure that the values for the CT and PT ratios, Kh,
Rr, and Gr are correct. Recalculate Kr, the register multiplier, to
ensure it is correct.
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