Protection

Please describe the installation. Several sentences would be a good thing. They let the forum know what the problem is that requires solution.

Generally, in Delta-Star Transformers, the Star side earth fault current (whether restricted or unrestricted) will not be reflected on the Delta Side. In Star-Star Transformers, if the Ground Differential Current is more than the bias setting made in the differential relay, thenit would definitely trip. But, the problem is, in impedance earthed systems and with in-zone faults close to the neutral, the fault current will be less than the bias setting made in the differential relay.