Function Block; Functionality; Operation Principle - ABB RELION 620 Series Technical Manual

1MAC504801-IB E
4.1.5.2
4.1.5.3
4.1.5.4
620 series ANSI
Technical Manual

Function block

67/51N
I0/IG/I2
TRIP
V0/VG/V2 PICKUP
BLOCK
ENA_MULT
RCA_CTL
A070433-ANSI V1 EN
Figure 87: Function block

Functionality

The earth-fault function 67/51N and 67/50N is used as directional earth-fault protection.
There are three different polarization signals - measured zero sequence voltage, calculated
zero sequence voltage and negative sequence voltage. The function picks up and trips
when the zero sequence current (I
and the angle between them is inside the set operating sector. The function also picks up
and trips when the negative sequence current (I
exceed the set limits and the angle between them is inside the set operating sector. The trip
time characteristic for low stage (67/51N and 67/50N-1) and high stage (67/50N-2) 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 directional earth-fault protection can be described using a module
diagram. All the modules in the diagram are explained in the next sections.
67/50N-1
TRIP
I0/IG/I2
V0/VG/V2 PICKUP
BLOCK
ENA_MULT
RCA_CTL
) and zero sequence voltage (-V
0
) and negative sequence voltage (-V
2
Section 4
Protection functions
67/50N-2
TRIP
I0/IG/I2
PICKUP
V0/VG/V2
BLOCK
ENA_MULT
RCA_CTL
) exceed the set limits
0
)
2
199