| 摘要 |
Described herein is a system for monitoring pollution from insulators by measuring leakage current. Said system is characterised in that it comprises a base current circuit which receives a signal emitted by a resistance connected to the edge portions of a current transformer secondary winding, the signal being connected to a clipper. The output signal from the clipper is connected to a signal booster circuit which output signal is connected to a voltage rectifier circuit, the output signal from said latter circuit representing a voltage signal that is sent to a filtering circuit which output signal is sent to an amplifier circuit, the output signal from said amplifier circuit originating the base leakage current. The invention further comprising a current peak detecting circuit which receives the output signal from the voltage rectifier circuit, said signal being subsequently sent to a sample and hold circuit, and to a voltage comparator. The output signal originated from the sample and hold circuit results in the leakage current peak, which is subsequently sent to a CPU and voltage comparator, the signal from this latter element represents a break signal which is sent to a OR gate, which simultaneously receives a delete signal. The output signal of the OR gate is connected to the sample and hold circuit. The inventive system includes a CPU which receives the break signal generated by the voltage comparator through a microcontroller in order to read the peak value of the leakage current. The peak level is read by the microcontroller according to the break signal level, and subsequently compared with the thresholds preset in the EEPROM memory of the system. Peak values are classified by the CPU and counters relative to each threshold are increased. The measurements of the base leakage current, the peaks leakage current, and the counter values of a RAM memory are measured by the microcontroller according to the program stored in the EEPRON memory; the delete signal is also generated by the microcontroller, said signal being sent to the OR gate according to the levels preset in the EEPROM memory in order to detect a new peak signal. The information stored in the RAM and EEPROM memories may be sent to a PC throughout a transmitter/receiver circuit actuated by the user or when a risky leakage current level is detected by the CPU, which may be restarted by a restart system. Said CPU includes a leakage current sensor that detects the leakage current value flowing over the insulators, said current is diverted by an insulating element to a wound current transformer which output signal is connected to a resistance simultaneously connected to the edge portions of the second winding of a current transformer.
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