Second-stage Voltage Dropper Tester

Introduction to the Double Pressure Drop Tester 

The overall measurement error of electrical energy meters is composed of the error of electrical energy meters, the composite error of voltage transformers, the composite error of current transformers, and the measurement error caused by the voltage drop of the secondary winding of voltage transformers, which can be expressed by the following formula:

    ε=εw＋εTA＋εTV＋εr

In Equation    εw—Meter Error%

εTA—Current Transformer Synthetic Error%

εTV—Synthetic Error of Voltage Transformer%

εr—Voltage Transformer Secondary Winding Voltage Drop Caused Measurement Error%

In power plants and substation electrical energy metering loops, the outdoor voltage transformers are located at a considerable distance from the electrical meters installed on the control room distribution board. Generally,200～400 mLeft and right, the entire circuit includes terminal blocks, switches, fuses, and conductors, which necessarily have contact resistance, conductor resistance, and distributed parameters. Consequently, there is a certain circuit impedance, leading to voltage drops in the secondary circuit between the voltage transformer and the electricity meter.The total voltage drop in the secondary circuit of a voltage transformer includes the sum of voltage drops across cables, terminal contact resistances, fuse wires, intermediate relay contacts, and small air switches. The error caused by the voltage drop of the secondary voltage of the voltage transformer refers to the percentage difference in amplitude between the secondary terminal and the load terminal voltage relative to the actual secondary voltage, as well as the total phase difference between the two voltages.

"Code for Technical Management of Electric Energy Metering Equipment"DL／T448－2000The regulation states, voltage transformer secondary circuit voltage drop, for...IClass metering devices should not exceed the rated secondary voltage.0．2Please provide the Chinese content that needs to be translated into American English.0．2 VThe allowable voltage drop for a three-phase four-wire circuit0.2/V）;Other measuring devices should not exceed the rated secondary voltage.0．5Unfortunately, the provided text does not contain any Chinese content to translate. Please provide the Chinese text you would like translated into American English.0．5 VThree-phase four-wire circuit voltage drop allowable value0．5／VPeriodic testing of the voltage transformer secondary circuit voltage drop in operation is necessary to calculate the electrical energy measurement error caused by it. This is of great significance for technical improvement, reducing the comprehensive electrical energy measurement error, and lowering billing losses.

The voltage transformer secondary circuit voltage drop measurement methods typically include indirect measurement and direct measurement (wireless measurement falls under indirect measurement). Due to the lower accuracy of indirect measurement methods, which does not meet the measurement requirements, this method is generally not used. In contrast, the direct measurement method (calibrator measurement method) utilizes the principle of measurement difference, boasts high accuracy, and is reliable, thus widely employed in actual measurements.