IEC 61660-2:1997

Overview

IEC 61660-2:1997 is an international standard published by the International Electrotechnical Commission (IEC) that addresses the calculation of mechanical and thermal effects caused by short-circuit currents in direct current (d.c.) auxiliary installations within power plants and substations. This standard is part two of a broader series concerning short-circuit currents in these critical electrical systems and focuses specifically on the methods for calculating the impact of these short-circuits on rigid conductors.

The document provides a robust and practical calculation method based on substitute functions that approximate the maximum mechanical stresses and forces on conductor supports due to electromagnetic forces during a short circuit. By employing this method, engineers and designers can ensure safety, reliability, and compliance in power plant and substation auxiliary d.c. installations.

Key Topics

• Mechanical Effects Calculation
  The standard outlines procedures to compute the electromagnetic forces exerted on rigid conductors during a short circuit, including the resultant stresses on conductors and the forces transmitted to their supports. These calculations are essential for verifying conductor strength and the integrity of supporting structures.

• Thermal Effects Calculation
  IEC 61660-2 provides methods for determining the temperature rise in bare conductors and electrical equipment due to the heating effect of short-circuit currents. This helps ensure materials and components can withstand thermal stresses without damage.

• Scope of Application
  The standard applies exclusively to d.c. auxiliary installations, covering equipment such as:

  • Three-phase AC to DC rectifiers with 50 Hz bridge connections
  • Lead-acid stationary batteries
  • Smoothing capacitors
  • Independently excited DC motors

• Calculation Methodology
  The calculation approach relies on substitute functions designed to replicate the electromagnetic force effects closely, facilitating practical applications with sufficient accuracy for engineering decision-making.

• Related Installations and Equipment
  While focusing on rigid conductors, the standard advises referencing IEC 60949 and IEC 60986 for guidance on cables and insulated conductors.

• Integration with Other Standards
  IEC 61660-2 works in conjunction with IEC 61660-1, which covers the calculation of short-circuit currents themselves, ensuring a comprehensive analysis framework from current calculation through effect determination.

• Design Considerations
  The standard emphasizes the importance of considering operational loads such as dead weight, mechanical forces from switching, and seismic activity alongside short-circuit induced stresses for robust infrastructure design.

Applications

IEC 61660-2:1997 is highly relevant for:

• Power Plant Design Engineers
  Calculating the forces and heating caused by short-circuits helps optimize conductor and support design to maintain system integrity under fault conditions.

• Substation Equipment Manufacturers
  Ensuring product designs can withstand short-circuit stresses as per international standards improves performance reliability and market acceptance.

• Electrical Safety Analysts
  Assessing clearances, thermal ratings, and mechanical loading during faults supports effective maintenance and risk mitigation strategies.

• Installation and Maintenance Personnel
  Understanding the potential impacts of short-circuits enables better planning for inspections, retentions, and potential upgrades.

• Standardization and Regulatory Bodies
  Employing IEC 61660-2 as a reference ensures uniformity in safety and design approaches for d.c. auxiliary networks across the global electric power industry.

Related Standards

• IEC 61660-1: Calculation of short-circuit currents in d.c. auxiliary installations, providing fundamental current values used in effect calculations.
• IEC 60949: Calculation methods for short-circuit currents in three-phase systems, applicable for cables and insulated conductors.
• IEC 60986: Guidance for insulation coordination in direct current systems, relevant for understanding thermal and dielectric stresses.
• IEC 60050 (International Electrotechnical Vocabulary): Provides terminology and definitions crucial for maintaining consistency and clarity in technical communication related to electrotechnical standards.

By aligning engineering practices with IEC 61660-2 requirements, professionals ensure safety, durability, and operational reliability of d.c. auxiliary installations, crucial to the robust functioning of modern power plants and substations.

Keywords: IEC 61660-2, short-circuit currents, DC auxiliary installations, power plants, substations, electromagnetic forces, thermal effects, rigid conductors, fault current calculations, electrical standards, IEC standard, mechanical stress calculation, conductor temperature rise.