ABB RELION 620 Series Technical Manual page 330

Section 4
Protection functions
324
Operation mode
Freq> OR df/dt
The module calculates the pickup duration value PICKUP_DUR which indicates the
percentage ratio of the pickup situation and set trip time DT. The pickup duration is
available according to the selected value of the Operation mode setting.
Table 264: Pickup duration value
Operation mode in use
Freq<
Freq>
df/dt
The combined pickup duration PICKUP_DUR indicates the maximum percentage ratio of
the active protection modes. The values are available via the Monitored data view.
If there is a sharp frequency change in the waveform it can result in a
prolonged operate time. The reason is that the frequency algorithm does
not see it as a change in frequency, but as a loss of mains situation. In this
case frequency protection is delayed with 160 ms to give room for vector
shift protection to operate.
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
Description
A parallel operation between the protection methods
is enabled. The PICKUP output is activated when
either of the measured values of the protection
module exceeds its set value. Detailed information
about the active module is available at the
PICKUP_OFRQ and PICKUP_FRG outputs. The
shortest trip delay time from the set
Trip Tm df/dt is dominant regarding the TRIP output.
The time characteristic is according to DT. The
characteristic that activates the TRIP output can be
seen from the TRIP_OFRQ or TRIP_FRG output. If
the frequency gradient restores before the module
trips, the reset timer is activated. If the timer reaches
the value set by the Reset delay Tm df/dt setting, the
trip timer resets and the PICKUP_FRG output is
deactivated. If the frequency restores before the
module trips, the reset timer is activated. If the timer
Reset delay Tm Freq
reaches the value set by the
setting, the trip timer resets and the PICKUP_UFRQ
output is deactivated.
Available pickup duration value
ST_DUR_UFRQ
ST_DUR_OFRQ
ST_DUR_FRG
1MAC504801-IB E
Trip Tm Freq or
620 series ANSI
Technical Manual