초록 ▼

A non-ferrous current sensor is used to continuously measure the charging current magnitude in step-graded foil and paper insulation systems and capacitive insulation systems used on high voltage measurement and control apparatus such as instrument transformers and on the condenser bushings of power

A non-ferrous current sensor is used to continuously measure the charging current magnitude in step-graded foil and paper insulation systems and capacitive insulation systems used on high voltage measurement and control apparatus such as instrument transformers and on the condenser bushings of power transformers and circuit breakers. The low voltage measured signal is conditioned by an electronic circuit that modulates a DC signal in a system current control loop to provide continuous remote monitoring and alarm functions. Remote power is supplied to the sensor and conversion circuits through the current loop. The sensor detects changes in the charging current through the insulation ground conductor, indicating the degradation of the dielectric properties between the foil layers. The sensor and associated electronic circuitry are enclosed in a housing adaptable to be used with a capacitance tap common to high voltage measurement and control apparatus. A test tap allows a calibration control module to inject various current levels through the sensing circuits that allow for calibrating the overall system to a specific high voltage apparatus.

대표청구항 ▼

An insulation monitoring system for a high voltage apparatus having a capacitance tap coupled to an insulation system between a high voltage conductor and earth ground of said high voltage apparatus, said insulation monitoring system comprising: a. a transmitter module including an AC current sensor

An insulation monitoring system for a high voltage apparatus having a capacitance tap coupled to an insulation system between a high voltage conductor and earth ground of said high voltage apparatus, said insulation monitoring system comprising: a. a transmitter module including an AC current sensor for measuring and converting a charging current flowing in said insulation system between said high voltage conductor and earth ground to a first voltage signal proportional to said charging current and an electronic circuit means for converting said first voltage signal to a DC current and modulating a first current signal by said DC current for transmission over said transmission network, said modulated first current signal proportional to said charging current, said transmitter module further including means for coupling a simulated charging current signal through said AC current sensor; b. an adapter for coupling said transmitter module to said capacitance tap; c. a transmission network coupled to said transmitter module; d. a controller coupled to said transmitter by said transmission network to receive said modulated first current signal, said controller for demodulating said modulated first current signal to extract said DC current, converting said DC current to a voltage proportionally to said charging current, comparing said proportional voltage with a preset voltage level, and generating an alarm signal when said proportional voltage exceeds said preset voltage level; and e. a control unit for injecting said simulated charging current signal to said coupling means through said AC current sensor, said control unit for calibrating said insulation monitoring system.