IEC 60076-24:2020

Overview

IEC 60076-24:2020 sets out the specification for voltage regulating distribution transformers (VRDT), published by the International Electrotechnical Commission (IEC). This international standard applies to medium-power transformers with ratings from 25 kVA up to 3 150 kVA and intended for use in networks with equipment voltages up to 36 kV (medium voltage) or in low voltage (LV) networks up to 1.1 kV, provided they are equipped with voltage regulating devices.

Voltage Regulating Distribution Transformers (VRDT) are specifically designed to allow on-load voltage regulation, meaning they can control and adjust primary or secondary voltage while in operation. This capability is vital to maintaining stable voltage levels within distribution networks, particularly to avoid violations of limits defined by international or local standards.

VRDTs must be able to efficiently operate in both step-down and step-up modes. Products designed under IEC 60076-24:2020 align with the broader IEC 60076 series as well as relevant European standards such as EN 50160 and EN 50588-1.

Key Topics

• Scope and Application

  • Applies to transformers from 25 kVA to 3 150 kVA
  • For equipment up to 36 kV or LV networks up to 1.1 kV
  • Requires presence of voltage regulating devices

• Purpose of Installation

  • Regulates LV network voltage (commonly 400 V)
  • Ensures compliance with voltage limits specified by international and local standards

• Operational Capabilities

  • Supports both step-down and step-up voltage operation
  • On-load voltage regulation for operational flexibility
  • Number of regulation steps: typically 3 to 11 on-load steps
  • Voltage steps are between 1.0% and 3.0%, within a regulation range of ±5% to ±10% of rated voltage, unless specified otherwise

• Environmental and Electrical Requirements

  • Service conditions must adhere to IEC 60076-1 and IEC 60076-11
  • Loss and sound levels must comply with local and international standards (e.g., EN 50708)
  • Safety and electromagnetic compatibility (EMC) requirements according to IEC 61010-1, IEC 61000-6-2, IEC 61000-6-4, and IEC 61000-6-5

• Testing and Quality Assurance

  • Routine, functional, type, and special tests outlined for transformer and control units
  • Degree of protection provided by enclosures to meet at least IP30 (IEC 60529)
  • Clearly specified rating plate, including the marking "VRDT"

Applications

• Utility Distribution Networks

  • Ensures stable voltage supply to end-users in low-voltage distribution grids
  • Helps utilities avoid violations of voltage limits set out in EN 50160, improving service quality

• Renewable Energy Integration

  • Maintains voltage quality where distributed generation (solar, wind) can cause voltage fluctuations

• Industrial and Commercial Premises

  • Maintains operational voltage levels in sensitive installations or high-load environments

• Smart Grid and Automation

  • VRDTs play an increasingly important role in digitalized, automated grid operations requiring adaptive on-load voltage regulation

Related Standards

• IEC 60076 Series: General requirements for power transformers, including parts on temperature rise (IEC 60076-2), sound levels (IEC 60076-10), and dry-type transformers (IEC 60076-11)
• EN 50160: Defines voltage characteristics of electricity supplied by public electricity networks in Europe
• EN 50588-1: Specifies requirements for eco-design of power transformers
• IEC 60529: Specifies IP codes for enclosure protection
• IEC 61000 Series: Addresses electromagnetic compatibility requirements

Practical Value

Adopting IEC 60076-24:2020 helps manufacturers and operators ensure their voltage regulating distribution transformers meet modern requirements for safe, reliable, and efficient voltage control. Utilities, industrial sites, and grid operators rely on VRDTs to optimize voltage profiles, comply with voltage quality standards, and support the integration of distributed energy resources. Compliance also simplifies international trade and procurement thanks to harmonized specifications and test procedures.