Section 2(9) in The Central Electricity Authority (Technical Standards for Connectivity to the Grid) Regulations, 2007
(9)"Earth Fault Factor" at a location in a three-phase system means the ratio of 'the highest root mean square (r.m.s.) phase-to-earth power frequency voltage on a sound phase during a fault to earth (affecting one or more phases)' to 'the r.m.s. phase-to-earth power frequency voltage which would be obtained at the selected location without the fault';
