Overview
IEC TS 62749:2015 - Assessment of power quality - Characteristics of electricity supplied by public networks defines the expected characteristics of electricity delivered at the supply terminals of public low, medium and high voltage networks operating at 50 Hz or 60 Hz. Published as an IEC Technical Specification (TC 8), it provides recommended values for power quality indices and practical methods for assessing power quality at both site and system levels.
Key topics
The Technical Specification organizes power quality into measurable phenomena and provides guidance on assessment and interpretation. Major technical topics include:
- Frequency deviation - expected behaviour and assessment approach.
- Supply voltage deviation - recommended limits for LV, MV and HV systems.
- Voltage unbalance - detection and significance.
- Flicker - severity assessment and recommended P values.
- Harmonics and interharmonics - recommended individual harmonic levels and total harmonic distortion guidance for LV, MV and HV supply terminals.
- Voltage dips (sags), swells and interruptions - characterization and reporting.
- Mains signalling, rapid voltage changes and transient overvoltages - definitions and monitoring expectations.
- Assessment methods - clause on objectives, measurement strategies for continuous phenomena and single events, site vs system aspect evaluation, and example reporting formats.
- Informative annexes - example PQ profiles for various countries/regions, impacts of poor power quality, issues related to distributed generation and micro-grids, and methods to maintain or improve power quality.
Practical applications
IEC TS 62749:2015 is intended to be a practical reference for:
- Distribution and transmission utilities setting or verifying supply quality at customer terminals.
- Regulators and policy makers establishing power quality expectations and service-level profiles.
- Power system engineers and consultants performing power quality audits, specifying monitoring campaigns, or interpreting measurement results.
- Manufacturers and integrators of power equipment, UPS, inverters and filters assessing compatibility with public network characteristics.
- Industrial and commercial consumers defining supply contracts or assessing vulnerability to dips, harmonics or flicker.
Typical uses include defining contractual supply quality, planning monitoring and mitigation, assessing the impact of distributed generation, and guiding corrective measures (filters, voltage regulation, grounding, etc.).
Related standards
IEC TS 62749 complements other IEC documents addressing power quality measurement, electromagnetic compatibility (EMC) and mitigation. It is best used together with established IEC measurement and EMC guidance for comprehensive specification and compliance work.
Keywords: IEC TS 62749:2015, power quality, supply terminals, public networks, harmonics, flicker, voltage dip, frequency deviation, LV MV HV, power quality assessment.