PHPTOV includes both definite time ( DT) and inverse definite minimum time
( IDMT) characteristics for the delay of the trip.
The function contains a blocking functionality. It is possible to block function
outputs, timer or the function itself, if desired.
4.5.1.4
Operation principle
The function can be enabled and disabled with the
Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of PHPTOV can be described using a module diagram. All the
modules in the diagram are explained in the next sections.
Phase
selection
logic
BLOCK
OPERATE
START
Level
detector
t
Timer
t
U_A_AB
U_B_BC
U_C_CA
Blocking
logic
Figure 332: Functional module diagram
Level detector
The fundamental frequency component of the measured three-phase voltages are
compared phase-wise to the set value of the
Start value setting. If the measured
value is higher than the set value of the
Start value setting, the level detector
enables the phase selection logic module. The
Relative hysteresis setting can be
used for preventing unnecessary oscillations if the input signal slightly differs from
the
Start value setting. After leaving the hysteresis area, the start condition has
to be fulfilled again and it is not sufficient for the signal to only return to the
hysteresis area.
The
Voltage selection setting is used for selecting phase-to-earth or phase-to-
phase voltages for protection.
For the voltage IDMT operation mode, the used IDMT curve equations contain
discontinuity characteristics. The
Curve Sat relative setting is used for preventing
undesired operation.
For a more detailed description of the IDMT curves and the use of the
Curve Sat Relative setting, see
Chapter 11.3.1.3 IDMT curve saturation of
Phase selection logic
If the fault criteria are fulfilled in the level detector, the phase selection logic detects
the phase or phases in which the fault level is detected. If the number of faulty
phases match with the set
Num of start phases, the phase selection logic activates
the Timer.
1MRS757644 H
Protection functions
620 series
Technical Manual
631
