The 125 MVA power transformer is transmission-class equipment for bulk supply, generation step-up and utility substation service. It is supplied with radiator banks, high-voltage bushings and the gauges, relays and protection specified for the application. At 125 MVA this is transmission-class equipment supplied through contract manufacture. Lead times are long and every unit is engineered to the specific application.
Specifications
| Rating | 125 MVA |
|---|---|
| Phase | Three phase |
| Primary voltage class | 115kV / 138kV / 161kV / 230kV / 46kV / 69kV |
| Secondary voltage class | 24940V / 34500V |
| Basic insulation level (BIL) | 550 kV / 650 kV / 750 kV / 900 kV / 250 kV / 350 kV |
| Frequency | 60 Hz |
| Temperature rise | 65 °C |
| Winding material | Aluminum |
| Insulating fluid | Mineral oil, Type I |
| Cooling class | ONAN |
| Taps | Plus/minus 2 x 2.5% full-capacity below and above nominal |
| Enclosure | Munsell Green 7GY3.29/1.5, tamper-resistant |
| Feed configuration | Per application |
| Standards | ANSI/IEEE C57.12, NEMA, DOE 2016 efficiency |
| Lead time | As little as 10 weeks |
Available voltage configurations
The 125 MVA is offered in 12 primary and secondary voltage combinations. Price is set by voltage class, so every voltage within a class carries the same price – a 12470Y/7200 primary and a 13200Y/7620 primary are both 15 kV class and cost the same.
Primary voltages available:
- 115kV class — 115000 GrdY
- 138kV class — 138000 GrdY
- 161kV class — 161000 GrdY
- 230kV class — 230000 GrdY
- 46kV class — 46000 Delta
- 69kV class — 69000 Delta
Secondary voltages available:
- 24940V class — 24940Y/14400
- 34500V class — 34500Y/19920
Full-load current
Rated secondary current for a 125 MVA unit at each available secondary voltage. Use these figures for conductor, breaker and bus sizing.
| Secondary voltage | Full-load current |
|---|---|
| 24940Y/14400 | 2,894 A |
| 34500Y/19920 | 2,092 A |
Rated primary current at each available primary voltage:
| Primary voltage | Full-load current |
|---|---|
| 115000 GrdY | 628 A |
| 138000 GrdY | 523 A |
| 161000 GrdY | 448 A |
| 230000 GrdY | 314 A |
| 46000 Delta | 1,569 A |
| 69000 Delta | 1,046 A |
Typical applications
- Interconnection of large generation assets
- Transmission substation service
- Generation step-up for utility-scale plants
- Bulk power supply
Construction
Standard construction is aluminum windings in a sealed tank with mineral oil, ONAN cooled, 65 °C rise. The tank is welded and finished in Munsell Green 7GY3.29/1.5. A four-position no-load tap changer provides plus and minus two 2.5% full-capacity taps. Copper windings and natural ester fluid, including STRATA X3, are available on request.
Standards and compliance
- Built to ANSI/IEEE C57.12 and applicable NEMA standards
- Meets DOE 2016 efficiency requirements
- Factory test report supplied with every unit
- Manufactured and supported by Bear Power Solutions, Brandon, Mississippi
Frequently asked questions
What voltages is the 125 MVA available in?
The 125 MVA is available with 115kV / 138kV / 161kV / 230kV / 46kV / 69kV primary and 24940V / 34500V secondary. That is 12 configurations in total. Every voltage inside a class carries the same price and the same basic insulation level.
What is the lead time on a 125 MVA?
Lead times start at 10 weeks from order confirmation, depending on configuration and current factory loading. Non-standard voltages, accessories, custom enclosure work and non-standard fluid or winding material extend that. Confirm the delivery date with Bear Power Solutions before committing to a project schedule.
How is a power transformer of this size delivered and installed?
Units at this rating ship by specialized heavy haul, frequently with radiators, conservator and bushings removed and shipped separately. Site assembly, oil processing and field testing are required before energization. Delivery logistics should be planned alongside the order.
Can the 125 MVA be supplied with copper windings or natural ester fluid?
Standard catalog construction is aluminum windings with mineral oil. Copper windings and natural ester fluid – including STRATA X3, Bear Power Solutions’ own Type II natural ester – are available on request. Both affect price and lead time, so request a quotation for a non-standard build.
What standards does the 125 MVA meet?
Units are built to ANSI/IEEE C57.12 and applicable NEMA standards, and meet DOE 2016 efficiency requirements. Factory test reports are provided with every unit.
Sizing the 125 MVA
At its lowest available secondary voltage the 125 MVA draws 2,894 A at full load; at its highest it draws 2,092 A. That spread is what makes secondary voltage selection an installation-cost decision as much as an electrical one – the higher voltage cuts conductor size for the same delivered power.
Secondary current at this rating is high enough that parallel conductor runs or busway are normally required on the low-voltage side. Confirm the secondary termination arrangement and available bus space before ordering.
Choosing between 125 MVA and adjacent ratings
Bear Power Solutions also builds the 100 MVA below it and the 150 MVA above it in this family. If your calculated connected load sits within about 20 percent of the 125 MVA rating, the 150 MVA is usually the better specification – transformers run most efficiently loaded well below nameplate, and the headroom costs less now than a replacement does later. If your load is comfortably under the 125 MVA figure, the 100 MVA carries lower no-load losses and a lower purchase price. Request a quote below with your actual load data and Bear Power Solutions will recommend a rating.
Request a quote
For a firm price on a 125 MVA in a specific voltage configuration, or for a non-standard build with copper windings, natural ester fluid or custom accessories, send the details below and Bear Power Solutions will respond with a written quotation.
