Basler Electric BE1-11m - Manual (Page 79)

9424200996 Rev L 67
Inverse Overcurrent (51) Protection
Five inverse overcurrent (51) elements monitor the current applied to the BE1-11m. An element can be
configured to protect against overcurrent by monitoring a single- or three-phase system, neutral current,
positive-sequence current, negative-sequence current, ground current, or unbalanced current.
The five, identical inverse overcurrent protection elements are designated 51-1, 51-2, 51-3, 51-4, and 51-
5. Element logic connections are made on the BESTlogic
™Plus screen in BESTCOMSPlus® and element
operational settings are configured on the Inverse Overcurrent settings screen in BESTCOMSPlus. A
summary of the logic inputs and outputs and operational settings appears at the end of this chapter.
BESTCOMSPlus Navigation Path: Settings Explorer, Protection, Current, Inverse Overcurrent (51)
HMI Navigation Path: Settings Explorer, Protection, Settings Group x (where x = 0 to 3), Current
Protection, Inverse Overcurrent 51
Element Operation
Inverse overcurrent protection can be used to protect equipment from damage caused by phase failure,
forward/reverse phase sequence, or phase unbalance.
Modes of Protection
Nine modes of protection are available: IA, IB, IC, Three-Phase, 3I0, I1, I2, IG, and Unbalance.
IA, IB, or IC Mode
The inverse overcurrent protection elements include three independent comparators, one for each phase.
Mode selection determines which phase pickup is required to activate protection.
Three-Phase Mode
The inverse overcurrent protection elements include three independent comparators, one for each phase.
Protection is activated when any of the three phases increases above the Pickup setting.
3I0 Mode
3I0 mode provides neutral overcurrent protection in a three-phase system.
I1 Mode
I1 mode provides positive-sequence overcurrent protection in a three-phase system.
I2 Mode
I2 mode provides negative-sequence overcurrent protection in a three-phase system. Refer to the
Negative-Sequence Overcurrent (46) Protection chapter for more information.
IG Mode
IG mode provides ground fault protection in a three-phase system.
Unbalance Mode
Unbalance mode provides unbalanced current protection. Two methods are available to calculate
unbalanced current. The first method is based on the negative-sequence current divided by the positive-
sequence current while the second method is based on the average current. The calculation method must
be specified on the System Parameters, Sensing Transformers screen in BESTCOMSPlus. Refer to the
Configuration chapter for more information.
BE1-11m Inverse Overcurrent (51) Protection