Video: HZJD-2Z

Video transcript

How the HZJD-2Z measures the dielectric losses, the permittivity and the resistivity of insulating oil, automatically, what it measures and why it matters, how the test cell works, how it is connected, and how a test runs from start to finish. As insulating oil ages or gets contaminated, it fills with polar products, moisture and particles. Its dielectric losses go up and its resistivity goes down, long before the breakdown voltage tells you anything.

That is why the dissipation factor and the resistivity are among the most sensitive checks of oil condition. Everything is in one instrument. The three-electrode test cell, the induction heater with its temperature control, the dielectric loss bridge with its AC source and a gas-filled standard capacitor, and the high-resistance meter with its DC high-voltage source. The reference capacitor does not drift with temperature or humidity, and the AC supply is regenerated inside,

so mains fluctuations never reach the result. measures the dissipation factor from 0.00001 to 100, the relative permittivity from 1 to 30, and the DC resistivity up to 20 TΩ·m. It tests at 500 to 2,000 volts AC and up to 500 volts DC, from 0 to 125 degrees. With the lid open, the test cell sits in the heating well, with the test cable and the temperature probe plugged in. Opening the lid interrupts the heating and the high voltage.

On the right, the color touchscreen and the built-in printer. test cell is the heart of the measurement. It has three electrodes, the outer high-voltage electrode, the inner measuring electrode, and a guard electrode that keeps leakage and stray capacitance out of the result. The gap is 2 millimeters, and the cell holds about 40 milliliters of oil. Oil properties change strongly with temperature, so the sample is tested at a set temperature.

The cell is heated by medium frequency induction, with no contact between the cell and the heater, an a PID loop holds it within half a degree. A limit relay stops the heating above 120 degrees. How is it different from the TAND220A? That one measures conductivity with a low-voltage square wave, and also goes to the field. The HZJD-2Z is a laboratory instrument.

It tests at power frequency up to 2,000 volts, adds DC resistivity, and heats the sample itself. In the box, the test cell, the test cable, and the temperature probe cable, an oil tube, a measuring cylinder, the power cable, spare fuses, thermal paper, and two Allen keys. Connection, Earth first. The Earth post on the back goes to the side Earth. Then the power cable, 220 volts. On top, the dedicated test cable goes from the measuring socket to the cell,

and the temperature probe from its socket into the inner electrode. The drain outlet goes to a waste container. A test follows six steps. Load the clean cell and connect it. Set the temperature and the voltages. Calibrate with the cell empty. Fill about 40 milliliters of oil and let the bubbles settle for over 15 minutes. Start the automatic test.

It heats, raises the voltage, and measures. Then store, print, and drain. The report gives the capacitance of the cell with the sample, the dissipation factor, the relative permittivity, and the DC resistivity. Each result is stored with its temperature, test voltage, date, and time. Up to 100 records can be recalled and printed later. Oil is very sensitive to the slightest contamination, so the cell must be clean. Between similar samples, rinse two or three times

with the next sample, using the drain button. For a full cleaning, dismantle the cell, wash it, rinse with distilled water, and dry it in an oven at 105 to 110 degrees. During a test, there is high voltage and high temperature in the cell. The instrument must be reliably earthed before use, and nothing is touched while it is energized. It cuts the voltage and warns on over-voltage, over-current or a short circuit, and on a temperature sensor fault.

Never use it in damp or explosive surroundings. In figures, dissipation factor accuracy of plus or minus 1% of reading plus 0 .0001. Resistivity within 10%, 220 volts supply, and 100 watts, and 22 kilograms. Insulating oil testing from Amperis.