DD IEC TS — IEC Technical Specifications Single-File Series Overview (17 Standards)

📘 DD IEC TS is the prefix under which BSI publishes IEC Technical Specifications (IEC/TS) as Drafts for Development (DD). An IEC Technical Specification is developed by the International Electrotechnical Commission (IEC) for subjects still under technical development that are not yet ready to become full international standards. BSI reproduces such documents verbatim, or as the UK implementation, under the DD series so that practical application experience can be gathered during a transitional period, after which the responsible committee decides whether to promote the document to a formal British Standard, extend its life, or withdraw it. This batch collects 17 DD IEC TS documents covering rotating electrical machines, electroacoustics and ultrasonics, wind-turbine availability, process-control function blocks, insulation-system evaluation, power-system information security, sound-intensity instrumentation, radiation thermometers, marine energy, and thermal management of electronic equipment.

1. Series Overview and Document Inventory 📌

The 17 documents under this prefix are all single-file series, i.e. each standard number corresponds to one DD IEC/TS document. They follow the numbering of the IEC technical committees and span ICS categories such as 17.140.50 (electroacoustics), 29.160.30 (rotating machines), 27.180 (wind energy), 33.200 (power-system information exchange) and 29.080.30 (electrical insulation). The table below lists the complete inventory of this batch.

2. Representative Standard (1): DD IEC TS 61400-26-1 Wind-Turbine Time-Based Availability ⚙️

Wind energy is a core domain of the IEC 61400 series. DD IEC TS 61400-26-1:2011, as Part 26-1 of the series, defines time-based availability of wind turbine generating systems. It classifies the operating states of a wind turbine into available, partially available and unavailable categories, and establishes the time-basis for each state so that availability figures are comparable across wind farms and manufacturers. Availability is a key metric in wind-farm economics and power purchase agreements (PPAs); by harmonising the definitions of “available time” the standard removes statistical bias caused by differing downtime attributions.

In practice, owners and OEMs typically specify an annual availability target (e.g. ≥97%) in the supply contract and verify it against this standard. The crux is the boundary between “available” and “unavailable”: whether downtime caused by insufficient wind or grid curtailment is counted must be categorised per the standard so that the inherent reliability of the machine is fairly reflected.

3. Representative Standard (2): DD IEC TS 60034-20-1 Stepping Motors and Control Motors 🔩

DD IEC TS 60034-20-1:2002 belongs to the IEC 60034 (rotating electrical machines) series and addresses stepping motors, a type of control motor, defining terminology, construction types, ratings and test methods. A stepping motor converts digital pulses into discrete angular steps and is widely used in printers, robots, numerically controlled machine tools and instrument drives. The standard defines step angle, holding torque, stall/step-loss behaviour, resonance zones and excitation modes (one/two-phase), giving a uniform basis for selection and acceptance.

Unlike ordinary induction or synchronous machines, stepping-motor evaluation must balance static holding torque and dynamic response; the standard provides the corresponding test conditions and data processing. The document was the responsibility of BSI committee PEL/2 (Rotating electrical machinery) and traces back to the withdrawn BS 5000-60:1982 — a classic case of an old British Standard being superseded by an IEC Technical Specification.

4. Representative Standards (3): DD IEC TS 61934 and DD IEC TS 62332-1 Insulation Evaluation ⚡

DD IEC TS 61934:2011 specifies methods for the electrical measurement of partial discharges (PD) in electrical insulating materials and systems under short-rise-time, repetitive voltage impulses — the regime produced by power-electronic converters. Modern variable-speed drives output PWM pulses with extremely steep edges, so winding end-turn insulation is prone to PD and accelerated ageing; this Technical Specification therefore provides a key test means for validating the insulation of inverter-fed machines. It is the responsibility of GEL/112 (Evaluation and qualification of electrical insulating materials and systems) and supersedes the 2006 first edition.

DD IEC TS 62332-1:2011 addresses the thermal evaluation of combined liquid and solid insulation systems (EIS), defining thermal-ageing evaluation procedures and general requirements for liquid-solid combinations used in transformers, motors and other equipment. It extends the thermal-ageing test philosophy of IEC 60216 to liquid-solid composite systems and provides a route for determining the temperature class (e.g. 105, 130, 155 or 180). Together the two documents constitute the standardised evaluation tools for the two dominant insulation failure mechanisms — electrical and thermal stress.

5. Representative Standard (4): DD IEC TS 62351-8 Power-System Information Security 🔐

Power systems are moving from closed proprietary networks to open IEC 61850/61968 information architectures, making information security a critical issue. DD IEC TS 62351-8:2011, Part 8 of the IEC 62351 (power systems management and associated information exchange — data and communications security) series, specifies the application of role-based access control (RBAC) within power-system information exchange. It defines the interaction of roles, permissions, sessions and user authentication so that substation automation and distribution-management systems can apply fine-grained authorisation to operators, maintainers and monitors, preventing unauthorised operations and malicious tampering.

The document works together with other parts of IEC 62351 (e.g. TLS transport security, digital signatures) to form an overall defence for power information security. In practice, SCADA/EMS systems connected to dispatch data networks should configure user roles and access policies in accordance with this standard.

6. Representative Standard (5): DD IEC TS 62492-1 Radiation Thermometers 🌡️

DD IEC TS 62492-1:2008 specifies the technical data of industrial radiation thermometers (infrared thermometers) used in process control, covering measurement range, spectral response, optical resolution, emissivity setting, response time, repeatability, and the classification and presentation of these parameters. Radiation thermometry is non-contact and suits high temperatures, corrosive media or moving targets. The document harmonises manufacturer data sheets, eases comparison and selection, and provides a basis for calibration and field application.

The document was prepared by GEL/65 (Measurement and control), subcommittee GEL/65/2 (Elements of systems). When selecting a radiation thermometer, particular attention should be paid to target size and distance ratio (D:S), emissivity correction and ambient-temperature compensation — parameters whose expression is standardised by this document.

7. Remaining Standards at a Glance 📋

In addition to the representative documents above, the batch includes several DD IEC TS documents related to measurement, acoustics, structures and marine energy, all with clear engineering value:

• Electroacoustics group: DD IEC TS 60318-7 specifies the head and torso simulator (HATS) for hearing-aid measurement; DD IEC TS 61094-7 gives free-field vs pressure sensitivity differences for laboratory standard microphones; DD IEC TS 62370 specifies EMC/ESD requirements for sound-intensity instruments.
• Process and systems group: DD IEC TS 61804-1 establishes the system framework for process-control function blocks (FB); DD IEC TS 61968-2 provides the glossary for distribution-management interfaces; DD IEC TS 62091 specifies controllers for stationary fire-pump drivers.
• Structures and electrical equipment group: DD IEC TS 62143 proposes a safety lifecycle methodology for aerodrome ground lighting; DD IEC TS 62433-1 establishes the general modelling framework for IC EMC; DD IEC TS 62610-2 gives a design guide for forced air-cooling of cabinets; DD IEC TS 62558 specifies the ultrasonic phantom and VDR distribution test method; DD IEC TS 62600-1 provides unified terminology for marine energy converters.

8. Frequently Asked Questions ❓