6.6.1 Voltage or Ratio Error in Voltage Transformer
According to IEC 60044-2 standard
Rated Transformation Ratio
The ratio of the rated primary voltage to the rated secondary voltage
Voltage Error (Ratio Error)
The error which a transformer introduces into the measurement of a voltage and which arises when
the actual transformation ratio is not equal to the rated transformation ratio
[IEV 321-01-21 modified]
The voltage error expressed in per cent is given by the formula:
where
K
n
is the rated transformation ratio
U
p
is the actual primary voltage
U
s
is the actual secondary voltage when U
p
is applied under the conditions of measurement
Phase Displacement
The difference in phase between the primary voltage and the secondary voltage vectors, the direction
of the vectors being so chosen that the angle is zero for a perfect transformer
[IEV 321-01-21 modified]
The phase displacement is said to be positive when the secondary voltage vector leads the primary
voltage vector. It is usually expressed in minutes or centiradians.
NOTE: The definition is strictly correct for sinusoidal voltages only.
6.6.2 Current or Ratio Error in Current Transformer
According to IEC 60044-1 standard
Rated Transformation Ratio
The ratio of the rated primary current to the rated secondary current
Current Error (Ratio Error)
The error which a transformer introduces into the measurement of a current and which arises from the
fact that the actual transformation ratio is not equal to the rated transformation ratio
[IEV 321-01-21 modified]
The current error expressed in per cent is given by the formula:
where
K
n
is the rated transformation ratio
I
p
is the actual primary current
I
s
is the actual secondary current when I
p
is flowing, under the conditions of measurement
Phase Displacement
The difference in phase between the primary and secondary current vectors, the direction of the
vectors being so chosen the angle is zero for a perfect transformer
[IEV 321-01-21 modified]
The phase displacement is said to be positive when the secondary current vector leads the primary
current vector. It is usually expressed in minutes or centiradians.
NOTE: The definition is strictly correct for sinusoidal currents only.
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