ABB REL650 Technical Manual page 234

Section 7
Current protection
228
Directional functions
Non-directional earth fault current protection
This function will measure the residual current without checking the phase angle.
The function will be used to detect cross-country faults. This function can serve as
alternative or backup to distance protection with phase preference logic. To assure
selectivity the distance protection can block the non-directional earth fault current
function via the input BLKNDN.
The non-directional function is using the calculated residual current, derived as
sum of the phase currents. This will give a better ability to detect cross-country
faults with high residual current, also when dedicated core balance CT for the
sensitive earth fault protection will saturate.
This variant has the possibility of choice between definite time delay and inverse
time delay (TimeChar parameter). The inverse time delay shall be according to IEC
60255-3.
For trip, the residual current 3I
Trip from this function can be blocked from the binary input BLKNDN.
When the function picks up, binary output signal STNDIN is activated. If the
output signal STNDIN remains active for the set delay tINNonDir or after the
inverse time delay the binary output signals TRIP and TRNDIN get activated.
Residual overvoltage release and protection
All the directional functions shall be released when the residual voltage gets higher
than a set level UNRel>.
In addition, there is also a separate non-directional residual over voltage protection,
with its own definite time delay tUN and set level UN>.
For trip, the residual voltage 3U
Trip from this function can be blocked from the binary input BLKUN.
When the function picks up, binary output signal STUN is activated. If the output
signal STUN is active for the set delay tUNNonDir, the binary output signals TRIP
and TRUN get activated. A simplified logical diagram of the total function is
shown in Figure 109.
shall be larger than the set level (INNonDir>).
0
shall be larger than the set level (UN>).
0
Line distance protection REL650 2.2 IEC
1MRK 506 382-UEN A
SEMOD171963-60 v4
SEMOD171963-63 v6
SEMOD171963-72 v8
Technical manual