Transformer Monitoring

Choosing a transformer monitoring package

Seven systems cover the failure modes that decide whether an oil-immersed power transformer stays in service: dissolved gas, partial discharge, hot-spot temperature, core and clamp earth currents, bushing insulation, vibration and physical intrusion. They are installed systems that report continuously while the transformer stays energised — not portable instruments carried from site to site.

What each system measures

• Dissolved gas analysis — the HF-T-602 transformer DGA online monitoring system measures nine dissolved gases plus moisture by photoacoustic spectroscopy: H₂ 0–5000 ppm, C₂H₂ 0–5000 ppm, CH₄/C₂H₆/C₂H₄/CO/CO₂ 0–10000 ppm and moisture 0–100 ppm, in an IP66 wall-mounted cabinet rated −40 °C to +70 °C on 100–240 V AC, with IEC 61850, Modbus, Ethernet and RS485 outputs.
• Partial discharge — the HF-T-603 transformer partial discharge online monitoring device has six independent channels that combine three detection methods: ultrasonic 20 kHz–200 kHz, high frequency 100 kHz–100 MHz with a measurable discharge lower limit of ≤1 pC, and UHF 300 MHz–2 GHz at ≤2 V/m sensitivity.
• Winding temperature — the HF-T-604 winding temperature monitoring system serves 10 kV–500 kV oil-immersed and dry-type transformers from −40 °C to +260 °C, at ±0.5 °C with Pt100 probes or ±0.3 °C with fluorescent fibre, 0.1 °C resolution, expandable from 3 to 64 channels.
• Core and clamp earth current — the HF-T-605 core clamp earth current monitoring device reads 1 mA–10 A at ±(2 % + 2 digits) with four adjustable compensation levels, the measurement that exposes multiple earthing and core short circuits early.
• Bushing insulation — the HF-T-608 transformer bushing monitoring system tracks the active component of leakage current, the dielectric loss factor (tanδ) and equivalent capacitance, the three parameters that show screen damage, ageing and moisture ingress.
• Vibration and physical intrusion — the HF-T-609 transformer vibration monitoring unit (11.2 mV/Pa at 250 Hz, 20 Hz–20 kHz) and the HF-T-601 smart transformer anti-theft monitoring device for unattended rural, pole-mounted and construction-site units.

What decides the choice

Three questions settle most specifications: which parameter list you have to trend (which gas set, how many PD channels, how many temperature channels), the environment the cabinet must survive, and how the data leaves the site — RS485 is standard across the range, with 4G, Wi-Fi and 4–20 mA available. Monitoring systems are usually bought together with the transformer or the retrofit project, so the transformer rating, cooling type and the existing SCADA or substation platform are the first details we ask for when quoting.

Related reading

• Dissolved gas: how to choose an online DGA monitoring system, which gases should be monitored and online DGA versus laboratory testing.
• Partial discharge: how to choose a PD monitoring device and UHF, HFCT and ultrasonic methods compared.
• Security: how a transformer anti-theft monitoring system works.

All monitoring systems in this section are sourced from qualified partner factories in China, verified and tested against their datasheets before shipment and delivered with test documentation. Houfeng is a trading company and supplier, not a manufacturer.