Application - ABB RELION 620 Series Technical Manual

Section 4
Protection functions
4.2.4.5
288
Timer
Once activated, the timer activates the PICKUP output. The time characteristic is
according to DT. When the operation timer has reached the value set by Trip delay time,
the TRIP output is activated if the overvoltage condition persists. If the negative-
sequence voltage normalizes before the module trips, the reset timer is activated. If the
reset timer reaches the value set by Reset delay time, the trip timer resets and the PICKUP
output is deactivated.
The timer calculates the pickup duration value PICKUP_DUR, which indicates the ratio
of the pickup situation and the set trip time. The value is available in the monitored data
view.
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
trip 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

A continuous or temporary voltage unbalance can appear in the network for various
reasons. The voltage unbalance mainly occurs due to broken conductors or asymmetrical
loads and is characterized by the appearance of a negative-sequence component of the
voltage. In rotating machines, the voltage unbalance results in a current unbalance, which
heats the rotors of the machines. The rotating machines, therefore, do not tolerate a
continuous negative-sequence voltage higher than typically 1-2 percent x V
The negative-sequence component current I
synchronous machine, is linearly proportional to the negative-sequence component
voltage V . When V is P% of V
2 2
The negative-sequence overcurrent 46 blocks are used to accomplish a selective
protection against the voltage and current unbalance for each machine separately.
Alternatively, the protection can be implemented with the 47 function, monitoring the
voltage unbalance of the busbar.
, drawn by an asynchronous or a
2
, I is typically about 5 x P% x I
n 2
1MAC504801-IB E
.
n
.
n
620 series ANSI
Technical Manual