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
Description
IRES
Residual current (measured or calculated)
URES
Residual voltage (measured or calculated)
See the preprocessing function blocks in this document for the possible
signal sources.
There are a few special conditions which must be noted with the configuration.
Table 594: Special conditions
Condition
Description
URES calculated
The function requires that all three voltage
channels are connected for calculating the re-
sidual voltage. Setting
VT connection
must
be "Wye" in that particular UTVTR.
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
Operation setting. The
corresponding parameter values are "On" and "Off".
For WPWDE, certain notations and definitions are used.
Residual voltage Uo = (UA+UB+UC)/3 = U
0
, where U
0
= zero-sequence
voltage
Residual current Io = -(IA+IB+IC) = 3×- I
0
, where I
0
= zero-sequence
current
Protection functions
1MRS759142 F
530
REX640
Technical Manual