ABB RELION 620 Series Technical Manual page 247

1MAC504801-IB E
620 series ANSI
Technical Manual
I /I
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The I /I module calculates the ratio of the negative and positive sequence current. It
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reports the calculated value to the level detector.
Level detector
The level detector compares the calculated ratio of negative and positive phase sequence
currents to the set Pickup value. If the calculated value exceeds the set Pickup value and
the min current check module has exceeded the minimum phase current limit, the level
detector reports the exceeding of the value to the timer.
Min current check
The min current check module checks whether the measured phase currents are above the
set Min phase current. At least one of the phase currents needs to be above the set limit to
enable the level detector module.
Timer
Once activated, the timer activates the PICKUP output. The time characteristic is
according to DT. When the trip timer has reached the value set by Trip delay time, the
TRIP output is activated. If the fault disappears 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.
Section 4
Protection functions
241