NZ597255A - An energy meter circuit with a metrological portion with a cut-off switch and a non-isolated current sensor to sense current transitions between reference points - Google Patents

Abstract

597255 Disclosed is an electrical energy meter for measuring a phase current Iphn and a phase voltage (V1) as consumed by a user installation from at least one phase n of an electricity distribution network. The meter is of the type including a metrological portion (2) in which a reference potential is constituted by the phase n. The metrological portion (2) includes a non-isolated current sensor in series with a conductor of phase n in order to measure the phase current Iphn. This is achieved by measuring the potential difference (Vmes) across the terminals of the sensor. A cut-off switch (RK1) is in series with the current sensor and a monitoring device suitable for delivering a measurement ? ? representative of the potential difference between the phase conductor downstream from the cut-off switch (RK1) and the phase conductor upstream from the metrological portion (2). The metrological portion (2) further includes a first voltage divider receiving as input the phase voltage (V1) and delivering a measurement of a potential difference ? between a first potential, given by the phase conductor and a second potential. The monitoring device includes both a second voltage divider connected in parallel with the series connection formed by the current sensor and the cut-off switch (RK1), and a resistor connected between the phase conductor and the second potential downstream from the cut-off switch (RK1). The user installation includes a main circuit breaker and the meter includes a processor means for acting when the cut-off switch and the main circuit breaker are both in the open position to detect a transition in the measurement ? ? between a first value equal to a1 X ? and a second value equal to a2 X ? . These values are representative respectively of the position of the main circuit breaker performing a transition between a closed state to an open state and the position of the main circuit breaker forming a transition between an open state and a closed state. a1 is a first variable for when the circuit breaker is open and a value of the first variable a1 is selected with reference to one or more relationships between two or more resistances of the meter and a load of the meter. a2 is a second variable for when the circuit breaker is closed and a value of the second variable a2 is selected with reference to one or more relationships between two or more resistances of the meter and the load.