With a proper setting in the setup program you can modify the angular sector of intervention for the
threshold 67NS1 to 60÷245° (default direction) and 240÷65° (inverted direction).
The device calculates the earth current using the measurements of the phase currents, calculates the
homopolar voltage using the measurement of the phase voltages and computes the phase angle
between the homopolar voltage and the earth current.
The directional earth fault protection requires the setting of the following parameters:
• residual voltage threshold (Threshold 67 Vo) adjustable range 1÷40% En, in step of 1%
• earth fault current threshold (Threshold 67 Io) adjustable range 1÷40 A, in step of 0.5 A
The directional protection detects an earth fault if all the following conditions occur simultaneously:
• residual voltage greater than the threshold 67Vo
• earth fault current greater than the threshold 67Io
• the phase angle between the residual voltage and the earth fault current is inside of angular sector
of intervention of the threshold (phase angle Io compared with Vo in lag clockwise and with reverse
signal absent)
This threshold has a trip delay, whose value can be set from 0.11 to 5 s, in steps of 0.01 s.
Signaling intervention of threshold 67NS1 is provided by relay TS67AV; in case of intervention of
threshold 67NS2, the relays TS67AV and TS51A activate simultaneously. The contacts of relays are
connected to terminal block MB and acquired by remote control system. A red LED on the front of the
device turns on when a trip occurs.
With an appropriate configuration, you can use as reference the negative sequence voltage instead of
the zero sequence voltage. In this operation mode, the thresholds 67NS1 and 67NS2 described
above are disabled and a directional threshold is activated with the following configuration
parameters:
• negative voltage threshold, adjustable range 1÷40% En, in step of 1%
• earth fault current threshold, adjustable range 1÷200 A, in step of 0.5 A
The angular relationship between the negative sequence voltage (Vi) and the residual current that
determines the intervention of the threshold is shown in the following figure:
P515D851 Rev. E November 2019 Pag. 9 of 45
To Next Page
Loading...
Need help?
General