1, three-phase four-wire active energy meter check
(1) Check wiring: Mainly check whether the polarity of the current transformer matches the current input and output line of the electric energy meter, whether the phase sequence of the voltage is positive phase sequence, whether the voltage and current are in phase, and whether the joint contact is good.
(2) Current short circuit and voltage disconnection method: short the A, B, C phase current in and out or disconnect A, B, C phase voltage, see the speed of the energy meter turntable, if the load is stable and balanced Then, short-circuit one-phase current or disconnect one-phase voltage, the speed of the electric energy meter is 2/3 of normal. If the deviation is large, the metering is abnormal. It can also be checked by simultaneously sending the voltage and current of the same phase. At this time, the speed of the electric energy meter should be 1/3 of normal.
(3) Check the error of the electric energy meter: the voltage of the field calibrator is taken from the end button box of the electric energy meter, and the current clamps the current from the secondary side of the current transformer with the clamp-type current transformer. The relevant parameters on the display of the instrument (if there is a calibrator with a clamp-type transformer can also easily measure the ratio error of the current transformer), it is helpful to determine whether the wiring, current and voltage are normal, if the energy meter If the error is large, the verification is required.
2. Inspection of three-phase three-wire active meter
(1) Measuring line voltage: Use a multimeter to measure the line voltage between the voltage terminals of the energy meter: Uab=Ubc=Uca=100V when normal (the actual primary voltage is higher than the rated voltage, and the secondary voltage is slightly higher than 100V) The measured result is Uab=0, Ubc=Uca=100V, which means that the phase A voltage is disconnected, Uab=Ubc=50V, Uca=100V, then the phase B voltage is disconnected, Uab=Uca=100V, Ubc=0 , the C phase voltage is disconnected.
(2) Determine the B-phase voltage: Use the voltmeter to measure the voltage of each voltage terminal of the electric energy meter to the ground. If it is 100/1.732V, it is the voltage terminal of A or C phase, and it is the voltage of B phase of 0V.
(3) Ua, Uc pair adjustment method: If Ua, Uc are adjusted, the electric energy meter can still rotate, indicating that the wiring is definitely wrong, and vice versa.
(4) Disconnect the B-phase voltage method: When the load is stable and the wiring is correct, the B-phase voltage of the electric energy meter is disconnected. At this time, the voltage of the electric energy meter voltage coil is half of the rated voltage, so the electric energy meter is still rotating and rotating. Slow down half, if the B-phase voltage is disconnected, the energy meter is not slowed down by half, indicating that the wiring is definitely wrong, and vice versa.
(5) Correct the wiring: After checking the wrong wiring, the wiring should be changed to the normal phase sequence of the normal wiring, that is, the B-phase voltage is changed to the middle voltage terminal of the electric energy meter, and the A-phase component is added with the line voltage Uab and the current Ia, C phase. The component adds line voltage Ucb and current Ic.
(6) Error detection of electric energy meter: The error detection is basically the same as that of the three-phase four-wire electric energy meter. In the approximation method, if the secondary circuit is directly connected, Ki is calculated as 1: if the current and voltage are displayed according to the power distribution screen Once the current and voltage are used, they need to be converted to the secondary current and voltage calculation. When using the calibration method to calibrate the energy meter, if there is a current test terminal, it is better to use the calibrator current loop directly into the secondary current loop. If the clamp current transformer is used, the error will be slightly larger, and the calibration error will be You can use the vector diagram to check the wiring.
3, power failure check
(1) Measuring DC resistance: If power failure is allowed in the field, it can also be judged by measuring the current resistance of the electric energy meter and the DC resistance of the voltage coil: the DC resistance of the voltage coil of the general 220V single-phase electric energy meter is about 0.4-1.2kΩ, 3×380 The DC coil of the /220 active energy meter has a DC resistance of 0.4 to 0.8 kΩ, and the DC resistance of the voltage coil of the 3×100 active energy meter is 70-150 Ω, and their current coil DC resistances are both about 0 Ω.
(2) Measuring loop resistance: In the case of power failure, the point of arbitrarily disconnecting the current loop is measured by a multimeter to measure the DC resistance of the loop. When normal, the resistance is approximately zero. If the resistance is large, it may be a second fault or short circuit. : When measuring the voltage loop, disconnect at the terminal of the voltage transformer and measure the DC resistance of Uab, Ubc and Uca respectively. This value should be large. If it is close to zero or large, it may be short circuit or open circuit, then it must be segmented. Find to narrow the scope of the inspection.
(3) Determine the current transformer change: When the current transformer ratio is measured in the field, if the ratio of the standard current transformer is f0 and the measured error is δ, the mutual inductance can be determined by the formula f=f0(1+δ). The actual change of the device, such as the difference of the transformer measured by 150/5 standard transformer is -25%, then f = f0 (1 + δ) = 150 / 5 (1-0.25) = 200 / 5, then the current The actual ratio of the transformer is 200/5, and the voltage transformer ratio can also be determined by the same method.