69/66 kV Three-Phase Oil-Immersed Transformer Manual: Price, Configuration & Installation Guide
Time：2025-11-24 Auther：ZTelec-www.ztelectransformer.com
This 2024 buyer guide covers everything you need to specify, budget and install a 69/66 kV three-phase oil-immersed power transformer for utility, industrial or solar/wind projects. Typical price range USD 50 000 – 120 000 for 30 MVA unit, delivery 8-12 weeks ex-works China.
Quick Selection Table
10 MVA 69/66 kV Z% 12 % ONAN 55 000 $ | 20 MVA 69/66 kV Z% 13 % ONAF 68 000 $ | 30 MVA 69/66 kV Z% 14 % ONAF 85 000 $ | 40 MVA 69/66 kV Z% 15 % ONAF 105 000 $ | 60 MVA 69/66 kV Z% 15 % ONAF 120 000 $
Core Technical Data
Voltage ratio: 69 kV ±8×1.25 % / 66 kV / 33 kV / 20 kV / 10.5 kV (other on request)
Capacity: 10 – 60 MVA, 50 Hz or 60 Hz
Vector group: YNd11 or YNyn0+d
Cooling: ONAN (up to 20 MVA) / ONAF (30 MVA+) / OFAF optional
Impedance: 12 % – 15 % IEC 60076
Insulation: Class A, 105 °C rise; optional 65 °C low-noise design
Tapping: On-load tap-changer 30 A – 400 A rated through current
Protection: IP54 steel tank, Buchholz relay, pressure-relief device, oil temperature & winding temperature RTD Pt100
Price Drivers
Copper conductor grade (99.97 % purity) adds ~4 % cost versus aluminium; silicone oil FR3 increases price 8 % but raises fire point to 350 °C; on-load tap-changer adds 6 000 – 10 000 $; stainless-steel tank 1 200 $/ton premium; spot market copper & steel volatility ±7 % monthly.
Installation & Commissioning Workflow
1. Foundation: reinforced concrete 5 T/m², 200 mm high, oil containment pit 110 % tank volume, cable trenches sloped 1:10.
2. Transport: nitrogen filled <0.3 bar, shock recorder 3 g max; unload with 120 T mobile crane.
3. Vacuum oil filling: 66 kV requires <2 mbar, 8 hours; oil dielectric strength ≥60 kV/2.5 mm.
4. Mandatory tests: turns ratio ±0.5 %, insulation resistance >5 000 MΩ @ 2.5 kV, partial discharge <10 pC @ 1.5 Um, load & no-load losses per IEC 60076-1, oil moisture <15 ppm.
5. Energisation checklist: oil level 15 °C mark, cooling fans auto-start 80 °C, MV breaker protection settings injected, earth grid <1 Ω.
Typical Applications
Utility: 220/66 kV regional substation upgrade, 66 kV urban ring main.
Industry: 66 kV incoming supply for 30 MVA arc furnace, 40 MVA cement grinding mill.
Renewables: 33 kV collector stepped up to 66 kV for 150 MW wind farm, 250 MW solar PV.
Infrastructure: dedicated 66 kV/6 kV substation for international airport, data-centre campus 99.99 % availability.
FAQs
Q: Standard lead time?
A: 8-12 weeks for 30 MVA ONAN; 16-20 weeks if 60 MVA OFAF with spare parts kit.
Q: Can oil-immersed replace dry-type?
A: Oil units excel outdoor & high-capacity; dry-type mandatory indoor fire-restricted sites (subway, high-rise). Fire-protection oil containment and nitrogen injection available for oil option.
Q: How to cut life-cycle cost?
A: Select amorphous core (30 % no-load loss saving), choose 65 °C rise design, negotiate copper discount via forward contract, implement on-line DGA monitoring to extend oil life from 10 to 20 years.
Request a detailed 66 kV transformer quotation, test certificate or foundation drawing today—reply within 12 hours, worldwide on-site technical support available.
