Firstly, the S700’s wide range of fault detection algorithms, which allow it to capture earth faults on both effectively and non-effectively earthed systems. Secondly, it uses two novel algorithms; Waveform Similarity Co-efficient (WSC) and Transient Reactive Power (TRP). The S700 also has an independent residual current input with extra sensitivity, which will be further improved if a core-balanced CT is used. In particular, high impedance earth faults are characterised by their non-sinusoidal waveforms due to arc extinguishing near the zero crossing. S700 uses high sampling rate (128 samples per cycle) and a special algorithm (Waveform Similarity Coefficient) to recognise such waveforms, which cannot be done with traditional sensitive earth fault relays.