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NOTE
When using potential transformers, the input voltage scale is defined in the instrument by
the PT RATIO parameter, which is the relation of the PT primary rated voltage to the
secondary rated voltage. For example, using a PT with the ratings of 165 kV : 110 V, the
PT RATIO would be 165,000/110 = 1500. The PT RATIO must be specified correctly for
the instrument to provide accurate voltage readings.
2.5.2 120V Input
The instrument with the 120V input option is intended to be wired via potential
transformers with secondary line-to-line voltage up to 120V + 20%.
F
To ensure accurate readings, the measured voltage between terminals
2-11, 5-11 and 8-11 should not exceed RMS value 144 VAC and
amplitude value 226V.
2.6 Current Input Connections
The PM295 is designed to measure phase currents via external current transformers
(CTs) with either 1 A or 5 A secondaries. The current input ratings are factory
installed. All current inputs are galvanically isolated using internal current
transformers.
Using 3-wire connections , only two current transformers are required. It is also
possible to use three current transformers (see Figure 2-7). If necessary, the return
side of the current transformers (terminals 3, 6 and 9) may be grounded.
F
To ensure accurate readings, the input current should not exceed: for
the 1A secondaries - RMS value 1.2A and amplitude value 1.76A, and
for the 5A secondaries - RMS value 6A and amplitude value 8.8A. At
least one of the L1 or L3 phase voltages must be connected to provide
correct measurements of the current.
F
The CTs must be connected in the correct order and with the correct
polarity as shown in the wiring diagrams for the instrument to operate
properly. If the instrument displays a power factor of zero or close to
it, or if power readings show unreasonable values, the polarity of the
CT connections might be reversed.
For the line current inputs overload, see technical specifications in Chapter 6.
NOTE
The phase current input scale is defined in the instrument by the CT PRIMARY CURRENT
parameter. It is equal to the primary rating of the current transformer.
16
Installation
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