Voltage Sensors; Figure 37: Example Of A Voltage Sensor Label; Figure 38: Example Of Setting The Correction Factors For Voltage Sensor In Pcm600 - ABB UniGear Series Engineering Manual

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3.1.2

Voltage sensors

Correction factors
The amplitude and phase error of a voltage sensor is, in practice, constant and independent
on the primary voltage. This means it is an inherent and constant property of each sensor
and it is not considered to be unpredictable and bound to influences. Hence, it can be easily
rectified in the protection relay by using appropriate correction factors, specified separately
for every sensor. Values of correction factors for the amplitude and phase error of a voltage
sensor are entered on the sensor label and as well as in the sensor´s routine test report. To
achieve the required accuracy classes, it is recommended to use both correction factors
(Cfs), that is, the amplitude correction factor (aU) and the phase error correction factor (pU)
of the voltage sensor.
Figure 37 : Example of a voltage sensor label
Due to linear characteristics of the sensor measurement error caused by manufacturing tol-
erances can be compensated for by using correction factors entered in the protection relay.
The correction factors are entered via parameter setting in PCM600
Configuration / Analog inputs / Voltage (3U, VT))

Figure 38: Example of setting the correction factors for voltage sensor in PCM600

Amplitude correction factors of sensors also affect the scaling of SMV frames. Thus, it is
sufficient to configure these correction factors in the sender only. On the other hand, phase
error correction factors affect only the phasor of fundamental frequency and need to be set
both in the SMV senders and the receivers.
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