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DD CLC TS 60034 — Rotating Electrical Machines Technical Specifications
Rotating Electrical Machines — Technical Specifications (CLC/TS 60034, 2011 edition)
⚙️ The DD CLC/TS 60034 series is a CENELEC Technical Specification issued in the UK as a “Draft for Development (DD)”, corresponding to relevant parts of IEC/TS 60034, and focused on evaluation tests for rotating machine insulation systems and online condition diagnosis. With the widespread use of variable frequency drives (VFD), machine insulation faces new failure modes under compound stresses such as steep voltage fronts, partial discharge, and bearing currents; “how to evaluate, how to qualify, and how to diagnose” has become a key question for motor engineers. BSI Technical Committee PEL/2 (Rotating electrical machinery) is responsible for UK participation, classified under ICS 29.080.30 / 29.160.01. This article presents the series as a whole: its structure and technical points.
💡 Variable frequency supply has fundamentally changed the insulation failure mechanism of rotating machines: not only thermal ageing but also voltage impulses and partial discharge. The DD CLC/TS 60034 parts provide operable test methods for insulation evaluation and on-site diagnosis under these “new duty” conditions.
1. Series Overview 📌
The four parts of the DD CLC/TS 60034 series in this batch (all 2011 editions, identical to the corresponding IEC/TS 60034 parts):
| Part | Edition | Subject | Main Content |
|---|---|---|---|
| DD CLC/TS 60034-18-33 | 2011 | Part 18-33: Multifactor evaluation of form-wound winding insulation | Specifies functional evaluation test procedures for form-wound winding insulation systems under simultaneous thermal and electrical (multifactor) endurance stress. |
| DD CLC/TS 60034-18-42 | 2011 | Part 18-42: Qualification of PD-resistant insulation (Type II) | Specifies qualification and acceptance tests for partial discharge resistant insulation systems (Type II) in rotating machines fed from voltage converters. |
| DD CLC/TS 60034-24 | 2011 | Part 24: Online detection and diagnosis — application guide | Provides an application guide for online detection and diagnosis of potential failures in active parts and of bearing currents. |
| DD CLC/TS 60034-27 | 2011 | Part 27: Off-line partial discharge measurements on stator winding insulation | Specifies off-line partial discharge measurement methods for stator winding insulation (scan version; written from public domain knowledge). |
⚠️ Part 27 (60034-27:2011) is a scan-only file in the source material; its content is summarised from public domain knowledge. Always refer to the official BSI published version.
2. Insulation System Evaluation Tests 🔬
Part 18-33 addresses form-wound windings and specifies a multifactor endurance evaluation procedure where insulation systems are stressed by thermal and electrical stress simultaneously. Unlike single-stress accelerated ageing, the procedure emphasises the synergistic effect of combined thermal–electrical stress on insulation degradation. By combining specified temperature and voltage levels, it evaluates the life characteristics of insulation systems, providing a basis for design material selection and life prediction. Relative to the earlier TR, the 2011 edition: abandons the requirement to investigate the nature of interactions between thermal and electrical stresses; removes the use of single-stress acceleration factors; and updates test procedure details.
Part 18-42 addresses voltage-converter-fed machines and specifies qualification and acceptance tests for partial discharge (PD) resistant insulation systems (Type II). The steep repetitive voltage edges from converters induce partial discharge in windings that ordinary insulation cannot withstand. By specifying test voltage waveforms, discharge tests, and life qualification procedures, this part helps manufacturers and users verify long-term reliability under repetitive pulse voltage.
| Test Object | Stress Type | Key Determination |
|---|---|---|
| Form-wound winding insulation system | Thermal + electrical (simultaneous) | Endurance life, discharge inception and degradation rate |
| PD-resistant insulation (Type II) | Repetitive pulse voltage (VFD) | PD inception voltage, PD endurance life, acceptance criteria |
| Stator winding (off-line) | PD under applied voltage | Discharge magnitude, discharge patterns, insulation state interpretation |
3. Online Diagnostics and Bearing Currents 🔧
Part 24 is an application guide covering online detection and diagnosis of potential failures in the active parts of rotating machines and of bearing currents. It covers fault characteristics and symptoms, sensors and monitoring parameters (e.g., vibration, partial discharge, current/voltage waveforms, shaft voltage and shaft current), design and implementation of online monitoring systems, and diagnostic procedures and criteria. For VFD-driven machines, shaft voltage and bearing current are important causes of bearing electrical erosion and premature failure; the guide explains how to measure and analyse them and how to suppress them through insulated bearings, grounding brushes, and similar measures.
Part 27 provides off-line partial discharge measurement methods for insulation state assessment during maintenance outages, complementing the online methods of Part 24.
🚨 Bearing current in VFD machines must not be ignored: high-frequency common-mode voltage discharges through parasitic capacitance in bearings, producing “electrical fluting” on raceways that shortens bearing life or causes early failure. Assess shaft voltage at design and operation stages and adopt insulated bearings or grounding devices.
4. Engineering Practice 🛠️
- 🔍 Selection and acceptance: when selecting motors for VFD duty, confirm the insulation system has passed Type II qualification per Part 18-42 and agree on acceptance test items.
- 📋 Ageing evaluation: perform thermal–electrical combined endurance evaluation on large machine insulation systems per Part 18-33 to support life management and life extension decisions.
- 📈 Condition monitoring: build a “vibration + partial discharge + shaft current” online monitoring combination per Part 24 for early warning and planned maintenance.
- 🔧 Maintenance testing: perform off-line PD measurement per Part 27 during major overhauls to establish insulation baselines and compare with historical data.
5. Frequently Asked Questions ❓
❓ Q: How does the status of DD CLC/TS differ from a formal BS EN standard?
A: The DD (Draft for Development, now often published as PD) series are UK provisional publications intended to gather application experience before a formal standard is formed; they rank below BS EN, and procurement and contractual work should prioritise formal standards.
A: The DD (Draft for Development, now often published as PD) series are UK provisional publications intended to gather application experience before a formal standard is formed; they rank below BS EN, and procurement and contractual work should prioritise formal standards.
❓ Q: Why do VFD-fed machine insulation need a dedicated standard (18-42)?
A: Converters output steep-edged repetitive pulse voltages that induce high-frequency oscillations and partial discharge in winding turns and insulation, with degradation mechanisms different from sinusoidal mains. Part 18-42 is precisely the qualification for insulation under this “repetitive pulse + partial discharge” duty.
A: Converters output steep-edged repetitive pulse voltages that induce high-frequency oscillations and partial discharge in winding turns and insulation, with degradation mechanisms different from sinusoidal mains. Part 18-42 is precisely the qualification for insulation under this “repetitive pulse + partial discharge” duty.
❓ Q: What is the main harm of bearing current and how is it suppressed?
A: When shaft voltage exceeds the oil-film breakdown threshold, discharge in the bearing erodes raceway surfaces, causing premature bearing failure. Mitigations include insulated/ceramic bearings, grounding brushes, common-mode filtering, and optimised cable shielding and grounding.
A: When shaft voltage exceeds the oil-film breakdown threshold, discharge in the bearing erodes raceway surfaces, causing premature bearing failure. Mitigations include insulated/ceramic bearings, grounding brushes, common-mode filtering, and optimised cable shielding and grounding.
❓ Q: How should online and offline PD measurement be used together?
A: Off-line measurement (Part 27) is performed during outages — clean conditions, good repeatability, suitable for baselines; online measurement (Part 24) monitors continuously during operation, capturing developing defects. Combining them gives “periodic check-up + continuous monitoring”.
A: Off-line measurement (Part 27) is performed during outages — clean conditions, good repeatability, suitable for baselines; online measurement (Part 24) monitors continuously during operation, capturing developing defects. Combining them gives “periodic check-up + continuous monitoring”.