Woodward HighPROtec MCDLV4, Manual, Page: 647 / 1275

Protective Elements
IdG
–
Restricted Ground Fault Differential Protection [87N, 64REF]
Available elements:
IdG
The ground differential protective element can be used to provide:
Detection of ground faults on the line to be protected
Detection of internal faults on the neutral side of a solidly or low-impedance grounded transformer (in case of an
In-Zone transformer).
Description
This protection principle is based on a restricted ground fault scheme that only can be used in systems with an
earthed neutral. The ground differential current is the vector sum of the measured earth current and the calculated
zero sequence current from three measured phase currents. Similarly to the phase restrained differential protection,
the ground restraining current is the vector difference of the measured earth current and the calculated zero
sequence current from three measured phase currents. The trip characteristic is very much similar to the phase
restrained differential protection; however, it lacks the temporary restraining.
Protection Principle of Ground Current Differential Protection
The trip commands generated by the protective function restricted ground fault
IdG have to be assigned within the Breaker Manager.
Please be aware that the protective function Restricted Ground Fault IdG solely
can be applied to the winding end which builds the earthed neutral point.
647 MCDLV4 DOK-HB-MCDLV4-2E
Protection communication
interface
Protective Device
87L
87N
L1
Protective Device
87L
L2
L3
IL2
IL3
IL1
L1
L2
L3
IL2
IL3
IL1
Id
e/
Z0
1