SIST EN 50708-2-5:2021

Overview

SIST EN 50708-2-5:2021 is a key European standard published by CLC that defines additional requirements specifically for liquid immersed single-phase medium power transformers. This standard supplements the general principles laid out in EN 50708-1-1:2020, focusing on the energy performance and efficiency of these transformers. Approved by CENELEC in July 2021, EN 50708-2-5 aims to harmonize energy efficiency specifications, minimizing losses and ensuring consistent performance across European markets.

The document targets medium power transformers used in electrical distribution networks where single-phase transformers are applied, despite representing a smaller proportion of network transformers compared to three-phase units. By defining minimum requirements such as Peak Efficiency Index (PEI) values, the standard provides a guideline to optimize energy consumption and support sustainability goals in power distribution systems.

Key Topics

• Scope and Applicability
  EN 50708-2-5 addresses the energy performance of liquid immersed single-phase medium power transformers, adhering to the broader EN 50708 series. It incorporates additional requirements that refine or modify general clauses in EN 50708-1-1:2020.

• Energy Performance and Peak Efficiency Index (PEI)
  One of the central elements of the standard is the specification of PEI values, which quantify the minimum efficiency levels required for transformers of varying rated power (kVA). This ensures lower energy losses during operation:

  • PEI classes apply uniformly across voltage levels.
  • Defines Tier 1 and Tier 2 PEI values for transformers with rated powers ranging from 16 kVA to 3150 kVA.
  • PEI guides manufacturers and utilities toward more energy-efficient transformer designs.

• Service and Testing Conditions
  Service conditions follow EN 60076-1, while factory acceptance tests require verification that PEI values meet or exceed the minimum thresholds. Test reports must document PEI and related loss metrics.

• Standardized Requirements
  The document aligns with complementary parts of the EN 50708 series and related IEC standards, ensuring a cohesive framework for transformer ratings, tolerances, capitalizing losses, and overhauls.

Applications

• Power Distribution Systems
  The standard is essential for manufacturers, utilities, and distributors involved in designing, producing, and deploying liquid immersed single-phase medium power transformers. These transformers are typically deployed in:

  • Rural and urban distribution grids.
  • Renewable energy integration where single-phase outputs are required.
  • Industrial and commercial facilities needing reliable medium power supply.

• Energy Efficiency Programs
  EN 50708-2-5 supports European regulations and voluntary energy efficiency initiatives by setting measurable energy performance benchmarks. Adoption leads to reduced electricity losses, operational cost savings, and a lower carbon footprint.

• Transformer Specification and Procurement
  Utilities and developers can use this standard as a reference during tendering and procurement, ensuring the purchased transformers comply with recognized energy performance criteria. This facilitates harmonization of transformer quality across European countries.

Related Standards

• EN 50708-1-1:2020 - Power transformers - Additional European requirements - Part 1-1: Common part - General requirements
  Provides the foundation for general transformer requirements applied across the series.

• EN 50708-2-1 - Medium power transformer - General requirements
  Covers general conditions and specifications for medium power transformers relevant to this subpart.

• EN 60076-1 (IEC 60076-1) - Power transformers - General
  International standard defining fundamental service and testing conditions.

• EN IEC 60076-22-7 - Power transformer and reactor fittings - Accessories and fittings
  Related to components and fitting standards for power transformers.

• EN 50708-3-1 - Large power transformer - General requirements
  Another segment in the EN 50708 series focusing on large power transformers, offering context for medium power requirements.

Practical Value

Compliance with SIST EN 50708-2-5:2021 enables manufacturers to design liquid immersed single-phase medium power transformers that meet stringent European energy efficiency goals. Utilities benefit from lower operational losses and easier regulatory adherence, while end users experience more reliable and sustainable power delivery. Standardization according to EN 50708-2-5 supports a competitive, transparent market for transformers optimized for performance and environmental impact.

Keywords: EN 50708-2-5, medium power transformer, single phase transformer, liquid immersed transformer, Peak Efficiency Index, PEI, energy performance transformer, European transformer standard, power transformer requirements, CLC, CENELEC, power transformer efficiency, transformer testing, power distribution standards.