Application - ABB RELION 620 Series Technical Manual

Section 4
Protection functions
4.4.5.5
370
Timer 1
Once activated, the Timer 1 activates the PICKUP output. The timer characteristic is
according to DT. When the trip timer has reached the value set by Pickup delay time in the
DT mode, the TRIP output is activated. If a drop-off situation occurs, that is, a power
factor improves and exceeds the Pickup reset value in the direction as defined by Dir
pickup reset value before the trip delay is exceeded or either magnitude of all three phase
current or voltages goes below Current block value and Voltage block value respectively,
the timer reset state is activated. The reset timer depends on the Reset delay time setting.
The Timer 1 calculates the start duration value PICKUP_DUR, which indicates the
percentage ratio of the start situation and the set operating time. The value is available in
the Monitored data view.
Timer 2
Once activated, the Timer 2 activates the alarm timer. The timer characteristic is according
to DT. When the alarm timer has reached the value set by Alarm delay time in the DT
mode, the ALARM output is activated. If a drop-off situation occurs, that is, a power factor
improves and exceeds the Alarm reset value in the direction as defined by Dir alarm reset
value before the alarm delay is exceeded or either magnitude of all three phase current or
voltages goes below Current block value and Voltage block value respectively, the timer
reset state is activated. The reset timer depends on the Reset delay time setting.
Blocking logic
There are three operation modes in the blocking function. The operation modes are
controlled by the BLOCK input and the global setting in Configuration/System/Blocking
mode which selects the blocking mode. The BLOCK input can be controlled by a binary
input, a horizontal communication input or an internal signal of the protection relay's
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, but the TRIP output is not deactivated
when blocking is activated. In the "Block all" mode, the whole function is blocked and the
timers are reset. In the "Block TRIP output" mode, the function operates normally but the
TRIP output is not activated.

Application

The 55 function can be used to detect loss of excitation or for power factor correction.
Synchronous motors are mostly operated at leading power factor and its operation as
lagging power for extended period can be used an indication of an out-of-step condition
possibly caused by under or loss of excitation. To detect such a situation, the relay is
1MAC504801-IB E
620 series ANSI
Technical Manual