This is the most fundamental but easily confused concept in dielectric loss testing. Every time a new person is trained, the issue of positive and negative wiring should be emphasized, because incorrect wiring not only results in inaccurate data, but may also damage the instrument or cause safety accidents.

Positive wiring (grounded at the non grounded end of the test sample)

Positive wiring is suitable for devices where the low voltage end (terminal) of the tested object can be insulated from the ground.

Wiring method: Connect the high voltage cable (red clip) to the high voltage end of the test sample, connect the CX low voltage cable (red clip) to the low voltage end of the test sample, and reliably connect the instrument grounding terminal to the ground. Measure the current flowing from the low voltage end of the test sample through the CX end into the internal sampling resistor of the instrument.

Typical applicable equipment:

Transformer winding (low voltage end can be ungrounded)

Sleeve (leading from the flange to the low-pressure end)

Independent capacitor (both ends can float)

Reverse wiring (the test sample has been grounded)

Reverse wiring is applicable to equipment where the low voltage end of the tested object has been grounded and cannot be led out.

Wiring method: Connect the high-voltage cable (red clamp) to the high-voltage end of the test sample, and do not use the CX socket (empty). Measure the current directly from the high-voltage end of the test sample into the HV end of the instrument for sampling. The instrument casing has been grounded, which is equivalent to grounding the low end of the test sample.

Typical applicable equipment:

Current Transformer (Primary End Grounding)

Sleeve (shell grounded, can only be measured from the high voltage end)

High voltage cable terminal (shielding layer grounded)

Capacitive sleeve already installed on the equipment

What happens if you make the wrong choice

The test sample has been grounded but the correct wiring has been selected: the CX low voltage end is forcibly grounded, which introduces a large grounding leakage path at the low voltage end, and the measurement results have serious deviations, usually with a large tan δ deviation.

The low-end of the test sample can float, but the reverse wiring is selected: the measurement can still be carried out, but under the positive wiring, the dielectric loss of the test sample body is measured, and under the reverse wiring, the comprehensive dielectric loss of the test sample plus the stray capacitance of the high-voltage terminal lead to ground is measured. The value will be higher and cannot reflect the true state of the test sample.

What modes does HZ-2000H support

Four measurement modes: positive wire, reverse wire, CVT dielectric loss (self-excited method), reverse wire low-voltage shielding, can be selected with one click from the drop-down menu on the touch screen. Switching modes will also change the internal signal acquisition path, without the need for rewiring (but the wiring method itself needs to be adjusted according to the mode).