program. The influence of the BLOCK signal activation is preselected with the global
setting
Blocking mode
.
The
Blocking mode
setting has three blocking methods. In the “Freeze timers”
mode, the operation timer is frozen to the prevailing value. In the “Block all” mode,
the whole function is blocked and the timers are reset. In the “Block OPERATE
output” mode, COLPTOC is executed normally but the OPR_OVLOD and OPR_UN_I
outputs are not allowed to activate.
The BLOCK input does not block the BLK_CLOSE signal.
4.12.1.5 Application
The application area for three-phase overload protection function of shunt
capacitor bank is the protection of power capacitor banks intended for reactive
power compensation and filtering of the harmonics. Shunt capacitor banks provide
a low-impedance path to harmonic currents and hence attract harmonic currents
flowing in the system. Increased harmonic currents result in excessive voltage
stress across the capacitor bank. According to the standards, a high-voltage
capacitor shall be able to withstand 10% overload. Loading beyond that can cause
damage to the capacitor bank and in turn to the system. Hence, COLPTOC is
specially designed for the protection against overloads produced by harmonic
currents and overvoltage.
Undercurrent protection is used to disconnect the capacitor bank from the rest
of the power system when the voltage at the capacitor bank terminals is too
low for too long a period of time. To avoid an undercurrent trip operation when
the capacitor bank is disconnected from the power system, the undercurrent
functionality is blocked by using the capacitor bank circuit breaker status signal.
Furthermore, the reclosing inhibition feature provides protection against the
reconnection of a charged capacitor to a live network. Whenever the capacitor
bank circuit breaker is opened, the reclosing is inhibited for the duration of
the discharge time of the capacitor. The reclosing inhibition functionality can be
disabled manually or automatically. In the manual mode, the inhibition reclosing
has to be manually reset and in automatic mode, the reclosing inhibitionl resets
automatically after the set time.
4.12.1.6 Signals
Table 739: COLPTOC Input signals
Name Type Default Description
I_A SIGNAL 0 Phase A current
I_B SIGNAL 0 Phase B current
I_C SIGNAL 0 Phase C current
Table continues on the next page
1MRS757644 H Protection functions
620 series
Technical Manual
779
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