Cewe Prometer 100 - Transformer Compensation Calculations

Page 64 of 72
Prometer 100 User Manual
BGX501-943-R01
Transformer Compensations
Instrument transformer compensations
Instrument transformer compensations are specified as error in percent for amplitude, and as error in minutes
(one-sixtieth of a degree) for phase angle. These errors can be specified separately for all voltages and
currents.
AmpErr
Amplitude error as percent
PhaseErr
Phase angle error in minutes
meas
u
Measured voltage
u
Compensated voltage
Amplitude compensation
)1/( AmpErruu
meas
+=
Phase angle compensation
PhaseErrupup
meas
−=
In 3-element meters, phase voltages are compensated and in 2-element meters, phase to phase voltages. The
same calculation is used for all currents and voltages.
Power transformer losses
Power transformer losses consist of copper and iron losses. They are expressed as percentages of nominal
power. One value is specified for active loss and one for reactive.
Iron loss
FeLoss
Active iron loss as percent of nominal power.
meas
P1
Measured power.
1P
Compensated power.
Nom
Nominal power per phase
NomFeLossPP
meas
⋅+= 11
Copper loss
CuLoss
Active copper loss as percent of nominal power.
i
Phase current.
nom
i
Nominal current.
NomCuLossi
iPP
nommeas
⋅⋅+=
2
)/(11
Corresponding calculations made for active and reactive power.
Definition of phase order
Correct phase order (123) corresponds to phase position:
pU
1
Phase position for U1