ABB 615 series Technical Manual page 601

1MAC059074-MB A
615 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 the negative and positive-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 value of Min phase current, 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 operation 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 operation 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
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.
Section 4
Protection functions
595