H | ELECTRICITY |
02 | GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER |
H | EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS |
3 | Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection |
26 | responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents |
28 | involving comparison of the voltage or current values at two spaced portions of a single system, e.g. at opposite ends of one line, at input and output of apparatus |
30 | using pilot wires or other signalling channel |
305 | involving current comparison |