FACILITY MONITORING LEAKAGE CURRENT Russian patent published in 2003 - IPC

FIELD: electric measurement technology. SUBSTANCE: invention can be employed to monitor leakage current from objects connected to electric voltage source, for instance, to measure leakage current through body of trolley bus to ground. Signals from generator 17 switch in step keys 8, 12, 13, key 8 connects and disconnects resistor 7 with resistance R_Д placed between body and ground. At same time voltage across body 4 is measured by means of meter 2 incorporating divider-limiter 6, rectifier 9 from which signals go to filters-converters 11, 14, 15 through keys 12, 13 and separating element 10. As result signals are fed to inputs of multiplier-divider 16 proportional to U_b - voltage on body 4 while key 8 is open; U_b-ΔU - voltage on body while key 8 is closed ( ΔU is drop of voltage U_b when resistor 7 with resistance R_Д is connected to body ); ΔU•R_Д - difference voltage between U_b and ( (U_b-ΔU) ) with due account of proportionality factor changing in line with R_Д. Voltage is formed across output of multiplier- divider 16 where B is constant coefficient which value is chosen for reasons of convenient level of signals in elements of amplifier 2. Voltage U₁₆ shows in certain scale total leakage current from body to ground through indicator 5. EFFECT: reduced error in measurement of leakage current achieved thanks to indirect measurement of resistance between body of trolley bus and ground inaccessible for direct measurement, measurement of voltage between body and ground and computation of current according to Ohm's law. 4 dwg