Areva MiCOM P225, Technical Manual

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P225/EN FT/B11 User Guide
Page 32/52 MiCOM P225
Examples:
Case n°1: Case n°2:
The stopping of the motor takes place
before the end of the “Tbetw 2 start” time
delay period.
A start inhibit signal “Tbetw 2 start” is
generated during the “Tbetw 2 start”
period. The stopping of the motor takes place
after the end of the “Tbetw 2 start” time
delay period, no start inhibit signal is
generated.
I
start
t
T
betw 2 start
I
N motor
T betw 2 start
P0202ENa
I
start
I
N motor
T
betw 2 start
t
T betw 2 start (logic state at 0)
P0203ENa
4.11.3 The REACCEL AUTHORIZ submenu: Re-acceleration/load shedding authorisation
A fall in voltage from the electrical network causes a reduction in rotor speed. When the
voltage is restored, the rotor starts on a re-acceleration phase in order to regain its nominal
speed. This re-acceleration manifests itself as an intake of current of approximately the
same value as that of the locked rotor current, its duration being relative to the magnitude of
the fall in voltage and the duration of the fall in voltage.
The MiCOM P225 relay can detect and measure the duration of a voltage drop. By
comparing how long this voltage reduction lasts with an adjustable time delay T
reacc
, the relay
will authorise or prevent the motor’s re-acceleration.
A settable undervoltage threshold "Detection V Dip" makes it possible to detect a voltage
drop.
A settable overvoltage threshold "Restoration V Dip" makes it possible to detect a restoration
of the voltage.
The user adjusts a time delay T
reacc
This time delay corresponds to the maximum duration of
a voltage sag for which the motor re-acceleration is to be authorised.
Upon detection of a voltage drop, the P225 relay initiates a time-delay, T
reacc
.
Three circumstances are possible:
•
Before the end of the time-delay T
reacc
(duration of the voltage sag shorter than T
reacc
),
the voltage is back (voltage greater than "Restoration V Dip") and within 5 seconds
after this restoration, the current absorbed by the motor crosses the
I
stall
threshold
(function [51LR/50S] BLOCK ROTOR), then:
−
the P225 goes into monitoring of a start-up sequence (initiation of the t
I
start
time
delay, EXCES LONG START function) and it deactivates the “ stalled rotor whilst
running ” function.
−
at the end of the t
I
start
delay allowed for a start, the relay P225 reactivates the
“ stalled rotor whilst running ” function.