FUNCTIONS
Phase overcurrent protection (51)
To ensure protection against polyphase failures, the device RGDAT-A70 has a phase overcurrent
protection, in tripolar configuration, with a single threshold. The device acquires the measurement of
phase currents by combined sensors and provides a fault signal when the current of one or more
phases exceeds the threshold value.
The threshold value of phase overcurrent protection is programmable from 20 A to 900 A, in steps of
10 A. The threshold has a trip delay, whose value can be set from 0.05 to 5 s, in steps of 0.01 s.
Signaling protection intervention is provided by relay TS51A, whose contacts are connected to
terminal block MB and acquired by remote control system. An orange LED on the front of device turns
on when a trip occurs.
Earth fault overcurrent protection (51N)
To ensure protection against double phase to ground failures, the device RGDAT-A70 has an earth
fault overcurrent protection, with a single threshold. The device calculates the earth current using the
measurements of the phase currents and provides a fault signal when the earth current exceeds the
threshold value.
The threshold value of earth fault overcurrent protection is programmable from 10 A to 200 A, in steps
of 2 A. The threshold has a trip delay, whose value can be set from 0.05 to 5 s, in steps of 0.01 s.
Signaling protection intervention is provided by relay TS51A, whose contacts are connected to
terminal block MB and acquired by remote control system. An orange LED on the front of the device
turns on when a trip occurs.
Directional earth fault protection (67N)
To ensure protection against earth faults, both in isolated neutral networks and in compensated
neutral networks, the device has a directional earth fault protection, with two thresholds (67NS1 and
67NS2); each threshold can be enabled independently from the other. The two thresholds have a
different set of angular sector of intervention (60÷255° for 67NS1, 60÷120° for 67NS2).
Through the use of an external signal coming from the remote control system, it is possible to control
the surveillance direction of the protection when power is supplied from the opposite side of the
network (surveillance direction at busbar side of Secondary Substation). In this operation mode, the
angular sector of intervention of the thresholds are: 240÷75° for 67NS1, 240÷300° for 67NS2.
The following figure illustrates, for example, the angular sector of intervention of threshold 67NS1 in
the two different operating modes.
P515D851 Rev. E
November 2019
Pag. 8 of 45