IEC 61869-5:2011

Overview

The IEC 61869-5:2011 standard, titled Instrument Transformers - Part 5: Additional Requirements for Capacitor Voltage Transformers (CVTs), is an essential international guideline developed by the International Electrotechnical Commission (IEC). This standard specifically governs the design, performance, and testing requirements of single-phase capacitor voltage transformers operating at system voltages above 72.5 kV and frequencies from 15 Hz to 100 Hz. It aims to ensure reliable supply of low voltage for measurement, control, and protective functions in electrical power systems. IEC 61869-5 replaces previous standards IEC 60044-5 and IEC-PAS 60044-5, providing updated and comprehensive requirements for capacitor voltage transformers.

This standard should be used alongside IEC 61869-1:2007, which covers general requirements applicable to instrument transformers.

Key Topics

IEC 61869-5:2011 covers multiple critical aspects for capacitor voltage transformers, including:

• Scope and ratings

  • Applicable to new single-phase capacitor voltage transformers connected between line and ground
  • Rated system voltages from 72.5 kV and above
  • Operational frequency range between 15 Hz and 100 Hz
  • Defined rated insulation levels, primary and secondary voltage ratings

• Definitions and terminology

  • Clarifications of general terms related to dielectric ratings, accuracy, and insulation
  • Index of abbreviations for ease of understanding

• Design and construction standards

  • Liquid insulation requirements with emphasis on tightness
  • Mechanical requirements ensuring durability and safety
  • Protection against internal arc faults to enhance operational safety
  • Markings and rating plate specifications for identification
  • Insulation requirements for primary and secondary terminals

• Performance requirements

  • Accuracy classes defined for measuring and protective applications
  • Thermal limiting outputs and voltage factor considerations
  • Insulation withstand capabilities including impulse and power-frequency withstand tests
  • Transient response characteristics to ensure proper operation under fault conditions
  • Ferro-resonance evaluation to reduce resonance risks in system operation

• Testing procedures

  • Comprehensive type, routine, and special tests such as temperature-rise, impulse voltage withstand, accuracy checks, and enclosure tightness
  • Multiple chopped impulse and partial discharge tests
  • Tests specific to carrier-frequency accessories integrated with CVTs

• Annexes and informative content

  • Typical circuit diagrams
  • Transient responses under fault
  • High-frequency characteristics for specialized applications

Applications

IEC 61869-5:2011 is highly relevant for:

• Power utilities and grid operators who require precise and reliable voltage measurement for system monitoring and control at high system voltages.
• Manufacturers of capacitor voltage transformers ensuring compliance with international quality, safety, and performance standards.
• Protection and control system designers who need accurate and dependable low voltage signals for relays, meters, and supervisory control devices.
• Testing laboratories and certifying bodies performing conformity assessments, type and routine testing on CVTs.

This standard supports the safe and reliable operation of electrical power systems by defining the specifications that CVTs must meet to accurately transform high voltage signals into manageable levels for instrumentation without compromising safety or performance under normal and fault conditions.

Related Standards

To fully implement IEC 61869-5:2011 requirements, users should also consider:

• IEC 61869-1:2007 - General requirements for instrument transformers, providing foundational definitions and test methods for all types of instrument transformers.
• IEC 60044-1 to 60044-4 - Older standards related to instrument transformer types and requirements that have been progressively replaced by the IEC 61869 series.
• IEC 60044-5 and IEC-PAS 60044-5 - Previous standards specific to capacitor voltage transformers, now superseded by IEC 61869-5.
• Electropedia (www.electropedia.org) - The official IEC online glossary for electrical and electronic terms offers authoritative definitions referenced in IEC standards.

Keywords: IEC 61869-5, capacitor voltage transformers, CVTs, instrument transformers, high voltage measurement, power frequency, voltage accuracy, insulation requirements, transient response, ferro-resonance, electromagnetic compatibility, electrical power systems, protective relays, electrical testing standards.