# BEST 250 MVA 380/154/34.5 kV Tertiary-Winding Compensation Autotransformer

> BEST 250 MVA 380/154/34.5 kV Tertiary-Winding Compensation 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-BST-AUT-TER-250M-380 | Brand: BEST Transformatör | Category: Power & Energy Equipment / Transformers / High-Voltage & Transmission Power Transformers / Interconnection & Transmission Autotransformers (345-380 kV)

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

## Overview

BEST 250 MVA 380/154/34.5 kV Tertiary-Winding Compensation 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%. Construction: Copper (Cu-Cu); cooling: ONAN/ONAF; 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% |
| No-load loss P0 | 72.00 kW |
| Load loss Pk | 450.0 kW |
| Calculated efficiency (power factor = 1) | 99.7916% at 100% load; 99.8526% at 50% load |
| Loss class | TEİAŞ 380 kV İletim Standardı |
| Windings | Copper (Cu-Cu) - cooling: ONAN/ONAF - insulation: Class A |
| Temperature rise | 65 K - sound pressure: 68 dB(A) |
| Mass and dimensions | 185000 kg - 9200×5100×6800 mm |
| Enclosure | IP55 - wheel gauge: 2000 mm |
| LI / AC withstand | 1425 kV peak / 630 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 family/application source. BEST Transformatör 380/154/34.5 kV tersiyer sargılı enterkonnekte iletim oto-transformatörü; 34.5 kV delta sargısına şönt reaktör veya STATCOM bağlanarak iletim hattı reaktif güç dengesini sağlar. Exact order code, guaranteed losses, dimensions, insulation level, cooling stage, winding material and project options must be confirmed with the OEM 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-BST-AUT-TER-250M-380","quantity":1}]}
```

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