Overview
IEC TS 60871-3:2015 is a Technical Specification that gives guidance on the protection of shunt capacitors and shunt capacitor banks for AC power systems with a rated voltage above 1 000 V. It applies to capacitors manufactured in accordance with IEC 60871-1 and provides practical protection guidance for installation, operation and safety. This second edition (2015) cancels and replaces the previous edition and includes updated references, clearer energy-limitation formulas for expulsion fuses and a new clause on synchronized switching.
Key topics and technical requirements
The specification addresses protection principles and component requirements, including:
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Fuse protection
- Internal and external fuse selection and characteristics (rated current, discharge capability, disconnecting capability, voltage withstand after operation).
- Fuse types covered: expulsion, current-limiting, and combination fuses.
- Guidance on energy limitation for expulsion fuses and coordination with capacitor case rupture curves.
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Unbalance detection and protection
- Methods and relay settings for detecting phase or neutral unbalance (neutral current, neutral voltage, phase voltage unbalance, differential measurements).
- Use of current and voltage transformers and sensitivity considerations.
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Overload and voltage protection
- Protection against overload currents, overvoltage and undervoltage conditions; reclosing behaviour.
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Transient and switching issues
- Use of surge arresters, damping devices and measures for limiting lightning and switching transients.
- New guidance on synchronized switching to reduce switching transients and inrush effects.
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Safety and auxiliary protection
- Requirements for discharging devices (internal resistors, external discharge devices), discharge after disconnection, and protection of dead metallic parts.
Applications
IEC TS 60871-3 is intended for practical use where reliable operation of reactive power equipment is critical:
- Design and protection of shunt capacitor banks in substations and industrial plants
- Selection and coordination of fuses and protective relays for high-voltage capacitor installations
- Mitigating switching and lightning transients affecting capacitor life
- Safety procedure development for maintenance (discharge and earthing)
Who should use this standard
- Power utilities and substation protection engineers
- Capacitor and capacitor-bank manufacturers
- Protection relay and fuse designers
- Network planners, consultants and testing laboratories
Related standards
- IEC 60871-1 (capacitor general requirements) - primary normative reference
- Other IEC publications on surge protection, switchgear and protection relays for system coordination
This Technical Specification provides focused, practical guidance to improve reliability, safety and coordination of shunt capacitors and shunt capacitor banks in high-voltage AC systems. For implementation, obtain the full document and applicable normative references from the IEC webstore.