ABB RELION REX640 - 4.5.7.5 Operation principle

Condition Description
to Phase selection “1”, “2” or “3”) if Voltage
selection is set to "phase-to-phase".
The function requires that all three voltage
channels are connected if Voltage selection is
set to "pos sequence".
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.
4.5.7.5 Operation principle
The function can be enabled and disabled with the Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of OEPVPH can be described using a module diagram. All the
modules in the diagram are explained in the next sections.
Level
detector
BLOCK
OPERATE
BLK_RESTART
t
Timer
t
START
COOL_ACTIVE
U3P
I3P
U/f
calculation
I_A
I_B
I_C
I
1
U_A_AB
U_B_BC
U_C_CA
U
1
F
Blocking
logic
Figure 495: Functional module diagram
U/f calculation
This module calculates the U/f ratio, that is, the excitation level from the internal
induced voltage (E) and frequency. The actual measured voltage (U
m
) deviates
from the internal induced voltage (E), a value the equipment has to withstand. This
voltage compensation is based on the load current (I
L
) and the leakage reactance (X
leak
) of the equipment. The leakage reactance of the transformer or generator is set
through the
Leakage React setting in percentage of the Z base.
The internal induced voltage (E) is calculated from the measured voltage. The
settings Voltage selection and Phase supervision determine which voltages and
currents are to be used. If the Voltage selection setting is set to "phase-to-earth"
or "phase-to-phase", the Phase supervision setting is used for determining which
phases or phase-to-phase voltages ("A or AB", "B or BC" and "C or CA") and currents
are to be used for the calculation of the induced voltage.
Protection functions
1MRS759142 F
886 REX640
Technical Manual