| 摘要 |
PURPOSE:To detect an insulation deterioration of electric power system with high sensitivity by obtaining admittances against ground of each phase in a section to be monitored and deciding the insulation deterioration of power system in the section to be monitored in accordance with these calculated values. CONSTITUTION:At first, outputs of zero-phase-sequence current sensors 15a, 16a, 17a are fetched and time system data for the zero-phase-sequence currents I0 at the output side of an electricity distributing and transforming station 1 are fetched to a computer 11, and amounts and directions of the current I0 of each feeder 12, 13, 14 are compared to decide whether the directions of currents I0 are different from a normal value and also the amounts are increased beyond a set level or not. When the detected values of current I0 do not exceed the set value, the process is continued, and if they exceed, held signals are outputted through each communication terminal 27, then the contents of memories 26 in each section are held and transferred to the computer 11 through the terminals 27 and a communication circuit 28. By the computer 11, a spectrum analysis for frequency is made for the transferred time series data to perform a processing to obtain the absolute values and the phases for every frequency. The processing for obtaining insulation resistances against ground and electrostatic capacitances against ground are performed in accordance with the above results. |
