ABB RELION REX640 Technical Manual page 840

Section 4
Protection functions
834
The calculated average voltage can be reset by the RESET binary input. The
calculated average voltage can also be reset using PHVPTOV1 Reset mean on the
Clear menu.
When the INITIALIZE input is activated, the average voltage measurement value is
initialized with the 10/12-cycle RMS voltage. The average voltage measurement
value can also be initialized using PHVPTOV1 Ini mean on the Clear menu.
Level detector
The calculated average voltage for all three voltages is compared phase-wise to the set
Start value setting. If the calculated voltage value is higher than the set value of the
Start value setting, 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.
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
matches with the set Num of start phases, the phase selection logic activates the Timer
module.
Timer
Once activated, the timer activates the START output. The operate delay time is not
settable directly but it depends on the Operate delay Mult setting and refresh timer
T . The operate delay time is calculated as:
refresh
Operate delay time in s
GUID-8FFDAB36-C914-4C8A-A601-ADD95CD08E3A V1 EN
When the operation timer has reached the value equal to Operate delay time, the
OPERATE output is activated if the overvoltage condition persists. If the average
voltage value normalizes before the module operates, the reset timer is activated.
The timer calculates the start duration value START_DUR, which indicates the
percentage ratio of the start situation and the set operating time. The value is available
in the monitored data view.
When the relay has tripped due to variation overvoltage protection,
check that operation is safe before closing the breaker. Clear the
average voltage value by using PHVPTOV1 Reset mean on the Clear
menu to prevent immediate retripping of breaker by PHVPTOV.
Considering the slow dynamic of the measurement, the protection
may remain in the START status for a long time. If the measured
voltage returns to a value lower than Start value, the function does not
Operate delay Mult T
= ⋅
1MRS759142 C
refresh
Technical Manual
(Equation 214)
REX640