Functionality - ABB 615 series Technical Manual

Section 4
Protection functions
4.4.1.3
4.4.1.4
588

Functionality

The negative-sequence overcurrent protection function 46 is used for increasing
sensitivity to detect single-phase and phase-to-phase faults or unbalanced loads due to, for
example, broken conductors or unsymmetrical feeder voltages.
46 can also be used for detecting broken conductors.
The function is based on the measurement of the negative sequence current. In a fault
situation, the function picks up when the negative sequence current exceeds the set limit.
The trip time characteristics can be selected to be either definite time (DT) or inverse
definite minimum time (IDMT). In the DT mode, the function trips after a predefined trip
time and resets when the fault current disappears. The IDMT mode provides current-
dependent timer characteristics.
The function contains a blocking functionality. It is possible to block function outputs,
timers or the function itself, if desired.
Operation principle
The function can be enabled and disabled with the Operation setting. The corresponding
parameter values are "Enable" and "Disable".
The operation of 46 can be described using a module diagram. All the modules in the
diagram are explained in the next sections.
A070660-ANSI V1 EN
Figure 298: Functional module diagram
Level detector
The measured negative sequence current is compared to the set Pickup value. If the
measured value exceeds the set Pickup value, the level detector activates the timer
module. If the ENA_MULT input is active, the set Pickup value is multiplied by the set
Pickup value Mult.
1MAC059074-MB A
615 series ANSI
Technical Manual