IEC 61869-20:2025

Overview

IEC 61869-20:2025 is an international standard published by the International Electrotechnical Commission (IEC) that specifies safety requirements for instrument transformers used in high voltage (HV) applications. This Part 20 of IEC 61869 focuses exclusively on instrument transformers with the highest voltage for equipment exceeding 1 kV AC or 1.5 kV DC. It excludes low power instrument transformers, which may be covered by separate or future standards.

This standard addresses the safe design, operation, and testing conditions to ensure protection against electrical, thermal, chemical, and mechanical hazards often encountered in high voltage environments. The document provides essential guidelines for manufacturers, engineers, and safety inspectors to reduce risks related to electric shock, fire, and mechanical failure.

Key Topics

1. Scope and Definitions

• Applies to instrument transformers operating above 1 kV AC or 1.5 kV DC.
• Excludes low-power instrument transformers.
• Defines key terminology like high voltage instrument transformer (HV IT) and conventional voltage limits for low voltage (LV) and high voltage (HV).

2. Protection Against Electric Shock

• Safeguards for both primary and secondary circuits.
• Clear requirements on earthing (grounding): Each secondary circuit must be earthed at only one point to avoid safety and operational issues.
• Specific instructions related to earthing of high voltage current transformers (HV CTs) and voltage transformers (HV VTs), including examples and typical earthing schemes.
• Measures to eliminate risks from open or shorted secondary terminals.

3. Thermal and Chemical Hazard Protection

• Address risks associated with fire hazards derived from thermal overloads or faults.
• Recommendations to minimize the risk of internal arcing within the transformer.
• Preventing the leakage of insulating oil or the release of hazardous gases.

4. Mechanical Safety

• Requirements to protect users and equipment from mechanical hazards during normal operation and installation/dismantling.
• Guidelines to ensure the mechanical impact resistance of instrument transformers, especially indoor and outdoor models.

Applications

IEC 61869-20:2025 plays a critical role in various sectors where safe measurement and monitoring of high voltage parameters are essential, including:

• Power Generation: Ensuring safe measurement devices in high voltage power plants.
• Transmission and Distribution Networks: Instrument transformers compliant with this standard provide accurate current and voltage data while maintaining safety in substations and along transmission lines.
• Industrial Facilities: Protecting both personnel and equipment where high voltage electrical measurements are necessary.
• Utility Safety Management: Enabling utilities to meet strict safety regulations and maintain standards in electrical metering and protective relaying infrastructure.

Using these safety guidelines helps in mitigating dangers related to electrical shock, fire, and mechanical failure, translating to safer, more reliable electrical grid operations.

Related Standards

IEC 61869-20:2025 complements and refers to several essential IEC standards, including:

• IEC 60529: Degrees of protection provided by enclosures (IP Code) – Defines enclosure ratings for protection against dust, water, and other environmental effects.
• IEC 61869-1: General requirements for instrument transformers – Establishes foundational principles applicable across all types of instrument transformers.
• IEC 61869-99: Glossary of terms for instrument transformers – Provides definitions essential for understanding Part 20.
• IEC 62262: Degrees of protection against mechanical impact (IK Code) – Specifies mechanical resilience needed for electrical equipment enclosures.
• IEC TS 60815-1: Guidelines for high-voltage insulators in polluted conditions – Relevant where instrument transformers are installed in harsh environments.

Together, these standards create a framework ensuring not only functional accuracy of instrument transformers but also stringent safety and durability requirements.

Keywords: IEC 61869-20, instrument transformers, high voltage safety, HV CT, HV VT, electrical safety standard, earthing requirements, instrument transformer testing, protection against electric shock, mechanical impact resistance, high voltage applications, IEC standards for instrument transformers.