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The error existing in the electric energy metering device is the comprehensive error of electric energy metering, which is composed of the error of the electric energy meter, the composite error of the voltage transformer, the composite error of the current transformer, and the metering error caused by the voltage drop of the secondary wire of the voltage transformer. It can be expressed by the following formula:
ε=εw＋εTA＋εTV＋εr
Where εw—Error of electric energy meter %
εTA—Composite error of current transformer %
εTV—Composite error of voltage transformer %
εr—Metering error caused by voltage drop of secondary wire of voltage transformer %
In the electric energy metering circuits of power plants and substations, the outdoor voltage transformer is far from the electric energy meter installed on the distribution panel in the control room, generally about 200 to 400 m. The entire circuit has terminal blocks, switches, fuses, and wires, which inevitably have contact resistance, wire resistance, and distributed parameters, thus there is a certain circuit impedance, resulting in a voltage drop on the secondary circuit between the voltage transformer and the electric energy meter. The voltage drop of the secondary circuit of the voltage transformer includes the total of voltage drops of cables, terminal contact resistance, fuses, intermediate relay contacts, small air switches, etc. The error caused by the secondary voltage drop of the voltage transformer refers to the percentage of the amplitude difference between the secondary terminal voltage of the voltage transformer and the load terminal voltage relative to the actual secondary voltage, as well as the phase difference between the two voltages.
Main Technical Indicators
Environmental Conditions
——Temperature: -5?C～40?C
——Relative Humidity: <95%(25?C)
——Altitude: <2500m
——External Interference: No strong vibration, no strong electromagnetic field
Main Technical Indicators of PT Current Transformer Secondary Loop Load Tester
1). PT Secondary Load Test
——Admittance Measurement Range: 0.1ms—50.0ms
——Admittance Measurement Accuracy:
——Secondary Voltage (50V－120V)
?X=?(2%×X+2%×Y)?2 words
?Y=?(2%×X+2%×Y)?2 words
2 words——Quantization error of the instrument
Note: When the measured value is below 0.2mS, the test voltage should be kept above 50V, and at the same time, pay attention to keep the wire passing through the center of the clamp meter. At this time, the quantization error of the instrument is 5 words
2). Voltage Meter Head: 0.5%
Main Technical Indicators of CT Current Transformer Secondary Loop Load Tester
——Impedance Measurement Range: 0.1Ω—50.0Ω
——Impedance Measurement Accuracy:
?X=?(2%×X+2%×Y)?2 words
?Y=?(2%×X+2%×Y)?2 words
2 words——Quantization error of the instrument
Current Meter Head: 1%
