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Table 415: Special conditions
Condition
Description
U3P connected to real measurements
The function can work with any two phase
voltage channels connected but it is recom-
mended to connect all three voltage chan-
nels.
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.
4.1.3.5
Operation principle
The function can be enabled and disabled with the
Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of PHPVOC can be described by using a module diagram. All the
modules in the diagram are explained in the next sections.
ENA_LOW_LIM
BLOCK
OPERATE
START
Timer
Level
detector
ENA_MULT
Effective
start value
calculator
t
t
Phase
selection
logic
I3P
I_A
I_B
I_C
U_AB
U_BC
U3P
U_CA
Figure 221: Functional module diagram
Effective start value calculator
The normal starting current above which the overcurrent protection starts is set
through the
Start value setting. The Effective start value of the current may need
to be changed during certain conditions like magnetizing inrush or when the
terminal voltages drop due to a fault. Hence, the effective start value calculator
module dynamically calculates the effective start value above which the overcurrent
protection starts.
Four methods of calculating the effective start value are provided in PHPVOC. These
can be chosen with the
Control mode setting to be either "Voltage control", "Input
control", "Volt & Input Ctrl" or "No Volt dependency".
The calculated effective start value per phase,
EFF_ST_VAL_A
,
EFF_ST_VAL_B
,
EFF_ST_VAL_C
, is available in the Monitored data view and is used by the Level
detector module.
All three phase-to-phase voltages should be available for the function to
operate properly.
Protection functions
1MRS759142 F
370
REX640
Technical Manual