ABB RELION REX640 Technical Manual page 530

Protection functions
WPWDE measures the earth-fault power 3UoIoCosφ and gives an operating signal
when the residual current Io, residual voltage Uo and the earth-fault power exceed
the set limits and the angle (φ) between the residual current and the residual
voltage is inside the set operating sector, that is, forward or backward sector. The
operating time characteristic can be selected to be either definite time (DT) or a
special wattmetric-type inverse definite minimum type (wattmetric type IDMT).
The wattmetric-based earth-fault protection is very sensitive to current transformer
errors and it is recommended that a core balance CT is used for measuring the
residual current.
WPWDE contains a blocking functionality. It is possible to block function outputs,
timers or the function itself.
4.2.7.4 Analog channel configuration
WPWDE has two analog group inputs which must be properly configured.
Table 593: Analog inputs
Input
IRES
URES
There are a few special conditions which must be noted with the configuration.
Table 594: Special conditions
Condition
URES calculated
Improper analog channel configuration causes a validation error if the analog
channels are not completely configured or they do not match with certain settings.
For troubleshooting, check the contents of this chapter and also the preprocessing
blocks in this document. The configuration can be written to the protection relay
once the mismatch is corrected.
4.2.7.5 Operation principle
The function can be enabled and disabled with the
corresponding parameter values are "On" and "Off".
530
See the preprocessing function blocks in this document for the possible
signal sources.
For WPWDE, certain notations and definitions are used.
Residual voltage Uo = (UA+UB+UC)/3 = U
voltage
Residual current Io = -(IA+IB+IC) = 3×- I
current
Description
Residual current (measured or calculated)
Residual voltage (measured or calculated)
Description
The function requires that all three voltage
channels are connected for calculating the re-
VT connection must
sidual voltage. Setting
be "Wye" in that particular UTVTR.
Operation setting. The
, where U
0 0
, where I = zero-sequence
0 0
1MRS759142 F
= zero-sequence
REX640
Technical Manual