Capacitance and Tan Delta Tester: Catch Insulation Aging Before It Fails

Most high-voltage equipment doesn't fail without warning — it fails after months of slow insulation degradation that nobody measured in time. A capacitance and tan delta tester (also called a dissipation factor or power factor tester) is how field engineers catch that drift early, by tracking the dielectric loss and capacitance of transformers, bushings, CTs, PTs, capacitors, and surge arresters before a small defect turns into an outage.

Our capacitance and tan delta tester replaces the old manual bridge method entirely. It uses variable-frequency power supply technology with single-chip microprocessor control to handle frequency conversion, A/D conversion, and data calculation automatically. The result is a measurement you can trust even in a live substation: by outputting 45 Hz and 55 Hz pure sine waves and filtering out 50 Hz field interference through Fourier-transform digital filtering, it holds its rated accuracy even under 200% interference. That's the difference between a usable reading and noise when you're working next to energized busbars.

What it measures and how accurately:

• Tan Delta (tgδ) with no upper range limit, resolution 0.001%, accuracy ±(reading × 1% + 0.0004)
• Capacitance from 3 pF to 1.5 µF, accuracy ±(reading × 1% + 1 pF), resolution down to 0.001 pF
• Built-in 10 kV high-voltage source and standard capacitor in one integrated case — no separate reference, far less field wiring
• Automatic recognition of capacitive, inductive, and resistive characteristics

A few things that matter on real jobs: the reverse-wiring low-voltage shielding lets you run a 10 kV measurement on the C11 of a 220 kV CVT bus without disconnecting leads. The CVT self-excitation function tests C1, C2, and total capacitance with four high/low voltage-current protection limits. It also accepts an external 40–70 Hz source or series-resonant supply for large-capacity, high-voltage dielectric loss work, and can even handle AC withstand tests on PT/CT secondaries and 400 V systems.

Safety is built into the workflow, not bolted on. The unit won't output high voltage if grounding is missing or poor, trips on overcurrent during breakdown, and cuts HV instantly if an operator makes accidental contact. A thermal printer, calendar clock, and large memory log every result, and the computer interface lets one PC control up to 32 units inside a comprehensive HV test vehicle.

At 28 kg in a 430 × 330 × 350 mm case, it's portable enough for the field yet precise enough for oil dielectric loss work with the right oil cup. For transformer insulation diagnostics, substation commissioning, and routine preventive testing, request the full datasheet or a quote.