Overview
IEC TS 60034-27-6:2026 is an international technical specification published by the International Electrotechnical Commission (IEC), focusing on the on-line electrical detection and monitoring of partial discharges (PD) in rotating electrical machines. This document applies to motors and generators equipped with rotor or stator windings supplied by converters, covering both type I and type II insulation systems for AC windings rated at 300 V and above. The standard is highly relevant for asset managers, manufacturers, electrical engineers, and maintenance professionals aiming to enhance the reliability and lifespan of machines operating with variable frequency drives or converter-fed supplies.
On-line PD monitoring is a vital diagnostic technique for identifying insulation degradation in high-voltage rotating machines, enabling condition-based maintenance, reducing unplanned downtime, and supporting predictive maintenance frameworks. This technical specification provides guidance on measurement procedures, sensor selection, data interpretation, and the challenges unique to converter-fed windings.
Key Topics
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Scope and Applicability
- Covers on-line electrical PD detection for motors and generators with converter-fed windings.
- Applicable to both type I (PD-free under rated conditions) and type II (PD-resistant) insulation systems.
- Addresses AC windings at 300 V and higher.
- Excludes non-electrical PD detection methods (e.g., optical, acoustic) and windings supplied via slip rings.
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Insulation System Considerations
- Type I insulation: Should experience minimal to no PD; frequent PD signals a critical fault.
- Type II insulation: Designed to withstand and tolerate PD without premature failure.
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Measurement Challenges
- Converter-fed machines introduce noise and voltage impulses, complicating PD detection.
- Need for synchronization with variable AC frequencies and identification of interference from converter switching.
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Sensor Selection and Frequency Ranges
- Recommends use of electrical and electromagnetic sensors such as high-voltage capacitors, antennas, and high-frequency current transformers (HFCT).
- VHF (30 MHz – 300 MHz) and UHF (300 MHz – 3 GHz) frequency ranges help suppress converter noise and improve PD detection accuracy.
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Instrumentation and Data Analysis
- Requires specialized instruments capable of distinguishing PD from converter-generated disturbances.
- Utilizes phase-resolved partial discharge (PRPD) plots and hybrid test approaches for more reliable assessment.
Applications
Related Standards
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IEC 60034-27-2
Rotating electrical machines - Part 27-2: On-line partial discharge measurements on the stator winding insulation. Focuses on machines directly connected to the grid.
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IEC TS 60034-27-5
Rotating electrical machines - Part 27-5: Off-line measurement of partial discharge inception voltage under repetitive impulse voltage.
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IEC 60034-18-41 / IEC 60034-18-42
Specify qualification and quality control tests for insulation systems (Type I and Type II) used in converter-fed machines.
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IEC TS 60034-25
Provides application guides for AC electrical machines used in power drive systems.
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IEC 60270
Sets out charge-based methods for partial discharge measurements.
IEC TS 60034-27-6:2026 establishes a practical, internationally accepted framework for on-line PD monitoring in converter-supplied rotating machines. By adopting standardized measurement procedures and interpreting results in accordance with the latest techniques, stakeholders can significantly improve machine reliability and performance, and reduce the risk of insulation-related failures in critical applications.