Abstract

Disclosed is a three-phase earth leakage breaker for protecting against electrical shock. The three-phase earth leakage breaker comprises: firstly detecting a leakage current, and operating a circuit breaking device and breaking an electrical path when the leakage current exceeds an allowable value; and secondly detecting the leakage current at half-cycles of electrical power, calculating a leakage current change by performing vector subtraction on the two leakage currents detected before and after an interval of the half-cycle, and operating the circuit breaking device and breaking the electrical path when the leakage current change exceeds an allowable value. The former case corresponds to protection against a normal leakage current which gradually increases, and has an allowable leakage current of several hundreds of mA. The latter case is a case where the leakage current abruptly changes as in the case of electrical shock to a human body, and has an allowable leakage current of several tens of mA in order to protect the human body from the electrical shock. Accordingly, along the three-phase electrical path, the earth leakage breaker operates without malfunction with respect to a change in the normal leakage current while protecting the human body from the electrical shock.

IPC Classes  ?

• H02H 3/16 - Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection responsive to fault current to earth, frame or mass

Abstract

Disclosed is an electric leakage breaker that uses a leakage current sensor to detect a resistive leakage current flowing through an electric line as is, and to detect a capacitive leakage current (also referred to as a 'charge current') at a level reduced from the actual level, so as to reduce the occurrence of malfunctions caused by capacitive current leakage in an electric line, by reducing the detected leakage current to less than the actual capacitive leakage current in the electric line.

IPC Classes  ?

• H01H 83/06 - Protective switches, e.g. circuit-breaking switches, or protective relays operated by abnormal electrical conditions otherwise than solely by excess current operated by current falling below a predetermined value

Abstract

An instrument for measuring ground-resistive leakage current is disclosed. A leakage current detection circuit detects composite leakage current from a line under test. A current-to-voltage conversion circuit converts the composite leakage current from the leakage current detection circuit into corresponding voltage, and then outputs the resulting voltage. An amplifier amplifies an output signal from the current-to-voltage conversion circuit. A phase inverter inverts the phase of one of output signals from the amplifier. A synchronization signal generator detects voltage from the line under test and then generates synchronization signals. Two half-wave integrators receive the synchronization signals from the synchronization signal generator and alternately integrate the output signals from the amplifier for each half period. A sample/hold circuit receives the synchronization signals from the synchronization signal generator, alternately performs sampling on outputs from the half-wave integrators for each half period and then holds values corresponding to the outputs for a half period.

IPC Classes  ?

• G01R 31/02 - Testing of electric apparatus, lines, or components for short-circuits, discontinuities, leakage, or incorrect line connection