User manual 09/2009 - Schneider Electric

The Metering Function3-Pole Circuit Breaker, 4-Pole Circuit BreakerThe calculation algorithm depends on the presence or absence of voltage metering on the neutralconductor.4-Pole or 3-Pole with ENVT: 3 Wattmeter Method3-Pole without ENVT: 2 Wattmeter MethodI1 V1N I2 V2N I3 V3N I1 U12 I2 I3 U32W1W2When there is voltage metering on the neutral (4-pole or 3-pole circuit breaker with ENVT option), the Micrologic E tripunit measures the power by taking account of 3 singlephaseloads downstream.When there is no voltage metering on the neutral (3-pole circuit breaker), the Micrologic E trip unitmeasures the power:• Using the current from two phases (I1 and I3) andcomposite voltages from each of these two phasesin relation to the third (V12 and V32)• supposing (by definition) that the current in theneutral conductor is zero:The calculated power Ptot equals:The calculated power Ptot equals PW1 + PW2:The table below lists the metering options:Method3-Pole CircuitBreaker, Non-Distributed Neutral3-Pole CircuitBreaker,Distributed Neutral3-Pole Circuit Breaker,distributed neutral(ENVT option)2 wattmeters X X (1) — —3 wattmeters — — X X(1) The measurement is incorrect once there is current circulating in the neutral.4-Pole CircuitBreaker3-Pole Circuit Breaker, Distributed NeutralThe ENVT option must be declared using the RSU software (see Metering Setup, page 123) and actuallyused.NOTE: Declaration of the ENCT option alone does not result in correct calculation of the powers. It isabsolutely essential to connect the wire from the ENVT option to the neutral conductor.LV434104 09/2009 81