SYSTEM TESTING INSULATION OF HIGH-VOLTAGE BUSHINGS Russian patent published in 2000 - IPC

FIELD: electric equipment for diagnostics of high-voltage machinery. SUBSTANCE: system testing insulation of high-voltage bushings is based on combination of two methods ( non-equilibrium-compensation and bridge ). By contrast to traditional non-equilibrium-compensation method this approach sums not phase currents with definite balancing coefficients but complex conductances which are primary characteristics of insulation of bushings. Additional phase shifts of -120 and - 240 deg are introduced with the aid of hardware to maintain relative phase shift of 120 deg for phases B and C. Balancing coefficients are determined at moment of start of test when bushings are healthy on condition that complex summary conductance is equal to zero. So task of test is reduced to periodic check of equality of complex summary conductance to zero. Deterioration of insulation of key zone of bushing- increased losses causes growth of active component of current which is unambiguously represented on vector diagram by rise of module and clockwise turn with reference to symmetry position of corresponding vector. Signal of phase A goes directly to proper input A of low-pass filter 8 and signals and of phases B and C go to inputs B and C of low-pass filters 8 correspondingly through phase inverters 6 and 7 to determine phase complex conductances from outputs of instrument current transformers 3. Simultaneously signals of three phases A, B and C proportional to voltages through voltage transformer 4 and instrument voltage transformers 5 go to inputs of second three low-pass filters 8. Signals and from outputs of low-pass filters 8 go through multiplexer 9 to input of analog-to- digital converter 10 where they are converted to digital code. From output of analog- to-digital converter 10 signal in the form of digital code is fed into microprocessor 11. So signal proportional to currents and voltages goes in the form of digital codes into microprocessor 11 where it is processed by program in agreement with principle stated above which makes it possible to determine faulty phase. EFFECT: enhanced operational reliability of system, reduced labor input to adjustment of system mounted on object. 3 dwg