Hitachi Energy RESIBLOC

Hitachi Energy RESIBLOC cast-resin dry-type to 63 MVA, with fiberglass-reinforced windings rated to -60 C

Hitachi Energy RESIBLOC is one of 32 data center transformers tracked in the SecondWatt catalogue, each with specifications, lead times and indicative secondary-market pricing.

Hitachi Energy RESIBLOC dossier: cast-resin dry-type to 63 MVA and 36 kV, PD under 10 pC, -60 C rating, lead times, inspection checklist, failure points.

RESIBLOC is Hitachi Energy's flagship cast-resin dry-type transformer line, in continuous production since 1974 and past its 50th anniversary with more than 70,000 units installed in over 120 countries. The differentiator is the winding: fiberglass rovings are wound into the epoxy during coil production rather than mold-cast around it, giving crack resistance under extreme thermal cycling and a rated operating ambient down to -60 C. The main factory is Brilon, Germany. Current specifications run to 63 MVA with high voltage to 36 kV standard and low voltage to 24 kV, at 50, 60, or 16.7 Hz. Cooling options span AN through AFWF, insulation is class F with partial discharge below 10 pC, and class ratings reach E4, C4, and F1. The line complies with EU Ecodesign Regulation 548/2014. Hitachi-Energy-badged used units have not yet reached the secondary market in volume because the nameplate only dates to October 2021; used supply carries ABB badges (see abb-resibloc, the same product line). New-unit demand rides the data center boom, with dry-type lead times of 20-32 weeks the shortest in the transformer complex.

Why it matters

Dry-type is the fastest-moving corner of a constrained market: 20-32 week leads against 128 weeks for oil-filled power class. RESIBLOC's 50-year record and 70,000-unit fleet make it the benchmark cast-resin line, and its crack-resistant winding addresses the failure mode that retires most cast-resin units early. For indoor data hall distribution it removes oil containment, suppression, and spill permitting entirely.

Who buys it

Data center operators placing transformers inside electrical rooms, offshore wind and marine integrators, mining operators, and cold-climate utilities specify RESIBLOC for its fire class and -60 C rating. Engineering firms specify it where FM Global fire separation for oil units is impractical. Buyers of used units should expect ABB-era nameplates for years to come.

Role in the data center

MV/LV distribution transformer inside the data hall electrical room, feeding LV switchboards and busway; increasingly specified at 3-5 MVA per unit for high-density halls.

Key specifications

Technical summary

Power range: up to 63 MVA HV: up to 36 kV standard; LV up to 24 kV Frequency: 50 / 60 / 16.7 Hz Cooling: AN, ANAN, ANAF, AFWF Insulation class F; PD below 10 pC Classes: E2-E4 environmental, C2-C4 climatic, F1 fire Enclosures: IP00 to IP54 Ambient: rated operation to -60 C Compliance: EU Ecodesign Regulation 548/2014 Traction variant: RESIBLOC Rail for rolling stock Factory: Brilon, Germany; line launched 1974

Pricing and availability

Trend: up Lead time, new: 20-32 weeks (dry-type class). Lead time, used or refurbished: 2-12 weeks. Warranty, used: 3-year typical from major US rebuilders.

Lifecycle and maintenance

Cast-resin and VPI dry-type transformers typically serve 25-30+ years with minimal maintenance: periodic cleaning, PD testing on critical units, fan service on AF designs, and torque checks. There is no oil system to sample, so temperature and PD are the condition indicators. Rebuild options are limited compared with liquid units; failed coils are usually replaced rather than repaired, which makes pre-purchase PD and visual inspection decisive for used units.

Common failure points

• Partial discharge — PD in resin voids degrading insulation toward failure
• Resin cracking — Cracks from thermal cycling or mechanical shock
• Contamination — Dust and conductive debris enabling surface tracking
• Cooling fans — Failed AF fans derating capacity
• Connections — Loose terminations overheating under load
• Overheating under harmonics — Excess temperature on non-linear loads beyond K-rating

Inspection checklist

Partial discharge — PD test per IEC 60270 practice; readings above 10 pC warrant investigation on cast-resin coils Resin condition — inspect all coils per IEC 60076-11 practice for cracks and crazing from thermal cycling; any through-crack fails Insulation resistance — megger HV/LV/ground; polarization index of 2.0 or higher passes Turns ratio — TTR on all tap positions; deviation beyond 0.5% from nameplate fails Winding resistance — three-phase balance within 2% between phases Contamination — inspect for dust and conductive debris between coils; contamination is a leading dry-type failure driver Cooling fans (AF units) — run-test all fans and verify temperature controller setpoints Temperature sensors — verify RTD or thermocouple channels read within 5 C of a reference at ambient Connections — torque-check HV and LV terminations; thermal-scan at first energization and re-check within 12 months Clearances — verify electrical clearances and enclosure IP rating match the installation environment Class verification — confirm fire/environmental/climatic classes (F1, E2/E3, C2/C3) against nameplate Harmonic suitability — verify K-factor rating (K-4/K-13) against the intended non-linear load profile Core and frame — inspect for shipping damage and loose core bolts; verify single core ground Energization test — verify secondary voltage within 5% on all phases and no abnormal sound level Records — factory test certificate, PD test data, and service history; missing PD data reprices the unit