# BEST Transformer 250 MVA 380/154/34.5 kV Three-Winding Interconnection Autotransformer

> BEST Transformer 250 MVA 380/154/34.5 kV Three-Winding Interconnection Autotransformer belongs to the Interconnection & Transmission Autotransformers (345-380 kV) category and is rated at 250 MVA with 380/154 kV primary/secondary voltage. Application: TEİAŞ 380 kV National Grid Backbone Main Interconnection Substation. Final ratings must be verified against the manufacturer datasheet.

> SKU: VF-BEST-AUTO-250M-380K | Brand: BEST Trafo (Balıkesir Elektromekanik) | Category: Power & Energy Equipment / Transformers / High-Voltage & Transmission Power Transformers / Interconnection & Transmission Autotransformers (345-380 kV)

**Voltformer canonical:** https://voltformer.com/product/best-transformer-250-mva-380-154-34-5-kv-three-winding-interconnection-autotransformer - markdown version: https://voltformer.com/product/best-transformer-250-mva-380-154-34-5-kv-three-winding-interconnection-autotransformer.md

## Overview

BEST Transformer 250 MVA 380/154/34.5 kV Three-Winding Interconnection Autotransformer is intended for TEİAŞ 380 kV National Grid Backbone Main Interconnection Substation. Configured electrical data: 250 MVA, 380/154 kV primary/secondary voltage, 50 Hz, 3-phase, vector group YNa0d11 and short-circuit impedance 12.5%. Construction: Copper (Cu-Cu); cooling: ONAN/ONAF/OFAF; loss class: TEİAŞ 380 kV İletim Standardı. These values support preliminary engineering selection; verify insulation levels, thermal limits, short-circuit duty, installation conditions and applicable standards against the manufacturer datasheet and the site study.

- **Application:** TEİAŞ 380 kV National Grid Backbone Main Interconnection Substation
- **Target industries:** National Transmission Grids, Mega Power Station Switchyards
- **Brand:** [BEST Trafo (Balıkesir Elektromekanik)](https://voltformer.com/brand/best-trafo.md) - Turkey's most established transformer manufacturer since 1966; BEST Trafo is the choice for global EPC projects with high-voltage power transformers up to 1000 MVA 525 kV, arc furnace transformers, TE
- **Category:** [Power & Energy Equipment](https://voltformer.com/catalog.md) / **Transformers** / [High-Voltage & Transmission Power Transformers](https://voltformer.com/category/power-transmission-transformers.md): 5 MVA–1000 MVA 110 kV, 154 kV, 380 kV, 500 kV and 1000 kV UHV AC/DC transmission and interconnection power transformers. / [Interconnection & Transmission Autotransformers (345-380 kV)](https://voltformer.com/category/power-transmission-transformers/interconnected-grid-autotransformers.md)

## Technical Specifications

| Property | Value |
|---|---|
| Rated power | 250 MVA |
| Primary / secondary voltage | 380 kV / 154 kV (±12 x 1.25% OLTC) |
| Frequency / phases | 50 Hz / 3-phase - YNa0d11 |
| Short-circuit impedance (Uk) | 12.5% |
| No-load loss P0 | 68.00 kW |
| Load loss Pk | 360.0 kW |
| Calculated efficiency (power factor = 1) | 99.83% at 100% load; 99.87% at 50% load |
| Loss class | TEİAŞ 380 kV İletim Standardı |
| Windings | Copper (Cu-Cu) - cooling: ONAN/ONAF/OFAF - insulation: Class A |
| Temperature rise | 65 K - sound pressure: 68 dB(A) |
| Mass and dimensions | 185000 kg - 8500×4800×7500 mm |
| Enclosure | IP55 - wheel gauge: 2000 mm |
| LI / AC withstand | 1425 kV peak / 560 kV rms - partial discharge: 5 pC |
| Environment | -25°C / +40°C; altitude ≤ 1000 m |
| Core steel | CRGO Laser-Treated Grain-Oriented Silicon Steel (23ZDMH85 / Baosteel B23R085) |
| Bushings / terminals | Direct Copper Busbar Terminals (Busbar Integrated / IP00-IP31) |

## Standards

- TEİAŞ technical specification
- IEC 60076
- TS EN 60076

## Accessories

**Included:** Reinhausen Vacuum OLTC, Online DGA 9-Gas Analyzer, Buchholz Relay
**Optional:** Fiber Optic Direct Winding Temperature Sensor

## Official sources

- https://www.besttransformer.com/

- **Source scope:** manufacturer-family
- **Last reviewed:** 2026-09-13

Manufacturer portfolio/family source. Confirm the exact order code, guaranteed ratings and project-specific options against the current OEM datasheet before procurement or an SLD study.

## Pricing & Logistics

- Pricing type: RFQ (Project Engineering) - Indicative range: $1,100,000 – $1,350,000 USD
- Delivery time: 2–8 weeks (may vary depending on technical configuration, factory capacity and destination) - Warranty: 48 months
- Compliance candidates: TEİAŞ technical specification, IEC 60076, TS EN 60076. Verify applicability and conformity against the exact offered model and project jurisdiction.

## RFQ

Request a formal factory quotation via Voltformer RFQ:

```json
POST https://voltformer.com/api/v1/rfq
{"companyName":"Example Energy","email":"procurement@example.com","items":[{"skuOrId":"VF-BEST-AUTO-250M-380K","quantity":1}]}
```

Full catalog JSON: https://voltformer.com/agent-catalog.json - OpenAPI: https://voltformer.com/openapi.json