calibration device for transformer

The standard device used for verification and calibration of instrument transformers.

Current transformers used in laboratories and power systems primarily serve to convert current or voltage for measuring and monitoring high voltages or large currents. The conversion ratio between current and voltage must be measured using a current transformer calibration instrument, as the accuracy of this instrument directly impacts the precision and reliability of measurement results. The HEZJ Current Transformer Calibration Instrument Comprehensive Inspection System enables holistic calibration of calibration instrument accuracy in compliance with verification regulations. Notably, this system features enhanced functionalities including S-class calibration capabilities, harmonic suppression capability assessment, and dial gauge performance evaluation for calibrated instruments. These advanced features allow the system to independently calibrate multiple current transformer calibration instruments according to specifications without requiring additional auxiliary equipment.
The HEZJ transformer calibration device differs from the conventional JZ2-type calibration apparatus. The JZ2 model, operating on a phase-shifting power supply principle, requires two calibration cycles to generate accurate measurements. This labor-intensive process, with its extended duration, hinders the liberation of electrical measurement technicians from repetitive tasks. In contrast, the HEZJ device employs an integrated electrical and electronic circuitry, displaying required parameters on a digital interface. A simple knob adjustment instantly delivers precise ratio signals. While the electrical-type transformer requires only one calibration cycle, the digital variant achieves faster results.

The panel features four terminal blocks at the top labeled Ip, Up, ΔI, and ΔU. These terminals can be configured to calibrate the PT and CT parameters of the instrument. Below the terminal blocks are three digital displays arranged from left to right, displaying the in-phase component value, voltage/current percentage, and orthogonal component value respectively. The in-phase and orthogonal component values are selected via four rotary switches beneath the displays, with polarity (positive/negative) selectable through push-button switches. The orthogonal component can also be configured in radial or minimum phase orientation.
The range selector beneath the dial indicator allows selection of operational voltage/current ranges (100V,100/√3V,100/3V,5A,1A). PT/Z and CT/Y toggle switches determine whether to output differential voltage or differential current. The multiplier function selects the same measurement range as the instrument under calibration to ensure synchronization. Note that both the in-phase and orthogonal dial plates must have set values on their first dial to enhance calibration accuracy.
Below the magnification switch is a selection switch for basic range and extended range/S level. In most cases, the basic range is sufficient to meet inspection requirements. When exceeding the basic range or during S-level inspection, select the extended range/S level (the corresponding magnification range is indicated in red). Note that voltage or current must not be increased.
The voltage regulator located at the lower right corner is used to provide the required working current and voltage. The rated capacity of the voltage regulator is 500VA, and it must not exceed this capacity during operation to avoid instrument damage.