ABB UniGear Series, Engineering Manual

Page: 38 / 112

26 1VLG5 00007 E
3 Engineering
3.1 Sensors
3.1.1 Current sensors
Correction factors
The amplitude and phase error of a current sensor is, in practice, constant and independent
on the primary current. 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 recti-
fied 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 current
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 (aI) and the phase error correction factor (pI) of
the current sensor.
Figure 29: Example of a current sensor label
Due to linear characteristics of the sensor measurement error caused by manufacturing
tolerances can be compensated for by using correction factors entered in the protection
relay. The correction factors are entered via parameter setting in PCM600
(IED Configuration
/ Configuration / Analog inputs / Current (3I, CT))
Figure 30: Example of setting the correction factors for current sensor in PCM600