The short answer
IEC Standards for Controls
The IEC publishes the international standards that define programmable controllers and their languages in IEC 61131, industrial security in IEC 62443, safety instrumented systems in IEC 61511, ingress protection in IEC 60529, and a family of telemetry and substation protocols. North American practice uses them alongside NEC, UL, and ISA documents: an IEC-rated enclosure or drive is common in a UL 508A panel, a controller is programmed to IEC 61131-3, and a security program is assessed to IEC 62443. Knowing which IEC number governs what lets a practitioner read a data sheet, a specification, or a vendor claim correctly.
Key points
- IEC 61131-3 defines the five PLC programming languages; almost every controller claims some conformance.
- IEC 62443 is the industrial security series; the utility-relevant parts are 2-1, 3-2, and 3-3.
- IEC 60529 IP ratings and NEMA enclosure types describe similar things differently. They do not convert exactly.
- IEC 61511 governs safety instrumented systems; chlorine gas is the usual utility application.
- IEC standards are adopted nationally with deviations. The edition and the national version matter.
What the IEC is
The International Electrotechnical Commission is the international standards body for electrical, electronic, and related technologies, with national committees from most countries, including the United States through ANSI. IEC standards are developed by technical committees and adopted, often with national deviations, by the member countries. In North America the codes that carry legal force are national, the NEC and the UL listings, and IEC standards appear as the technical basis of products, as the reference for programming and security practice, and increasingly as the harmonized version of what UL and ISA also publish.
The standards a controls practitioner meets
| Standard | Subject | Where it appears |
|---|---|---|
| IEC 61131 | Programmable controllers: general requirements, equipment requirements and tests, programming languages (part 3), communications, functional safety | Every PLC data sheet and every program; the IEC 61131-3 page |
| IEC 62443 | Security for industrial automation and control systems | Security programs, assessments, and product certifications; the IEC 62443 page |
| IEC 61511 | Functional safety: safety instrumented systems for the process industry sector | Chlorine gas feed and scrubber systems, emergency shutdowns; the process-sector application of IEC 61508 |
| IEC 61508 | Functional safety of electrical and electronic safety-related systems | The basis for safety-rated relays, controllers, and instruments; the SIL ratings on data sheets |
| IEC 60529 | Degrees of protection provided by enclosures (IP code) | Enclosure and instrument ratings such as IP66 and IP68; compared with NEMA types on the enclosure page |
| IEC 60947 | Low-voltage switchgear and controlgear | Contactors, breakers, and starters built to IEC ratings; utilization categories such as AC-3 |
| IEC 61850 | Communication networks and systems for power utility automation | Substation and switchgear communication; occasionally at large water plants with medium voltage switchgear |
| IEC 60870-5 | Telecontrol equipment and systems | The 60870-5-101 and -104 telemetry protocols, common outside North America where DNP3 is used |
| IEC 61158 and 61784 | Industrial communication networks: fieldbus and profiles | The formal home of PROFINET, EtherNet/IP, Modbus, and the other fieldbuses |
| IEC 60079 | Explosive atmospheres | Zone-based hazardous area classification and equipment; the counterpart to the NEC division system |
| IEC 61010 | Safety requirements for electrical equipment for measurement, control, and laboratory use | The safety listing basis for many instruments and power supplies |
| IEC 62682 | Management of alarm systems for the process industries | The IEC adoption of ISA-18.2 |
IEC and North American practice
- Enclosures
- IEC 60529 IP ratings describe ingress of solids and water by two digits; NEMA and UL 50 types describe environmental suitability including corrosion, ice, and oil. An IP66 rating is roughly comparable to NEMA 4 for water ingress but says nothing about corrosion or the UL listing; the conversion tables are approximate in one direction only.
- Contactors and starters
- IEC devices rated by utilization category and AC-3 current are common in UL 508A panels when they carry a UL listing; the sizing convention differs from NEMA sizes, and an IEC contactor is selected for the specific motor rather than by a NEMA size class.
- Hazardous locations
- The NEC Class and Division system and the IEC Zone system classify the same hazards differently; the NEC permits Zone classification as an alternative, and equipment carries both markings. Water utilities in North America mostly use Divisions.
- Programming
- IEC 61131-3 is the reference for controller programming everywhere. The vendor implementations differ, and the conformance is partial; the standard is what lets a programmer read another platform.
- Security
- IEC 62443 is used directly, with ISA co-publishing it. There is no separate North American industrial security standard; NIST frameworks sit above it.
- Safety
- IEC 61511 for safety instrumented systems is used directly in North America as ISA-84, with the ISA number and the IEC number referring to the same document.
Getting them
IEC standards are purchased from the IEC webstore or from national bodies and resellers, individually or by subscription; they are not free. The IEC publishes scope statements and previews, and the ISA versions of the co-published standards are sold by ISA. The practical documents for a utility, 61131-3, the 62443 parts named above, 60529, and 61511 where chlorine gas is used, are a modest purchase against the cost of the systems they govern.
Frequently asked questions
- Does IEC 61131-3 conformance mean I can move my program to another PLC?
- No. Conformance is declared per feature and every vendor adds extensions; a structured text program moves with editing, a ladder program moves with more, and the I/O and communications are rebuilt. The standard is why the languages are recognizable across platforms, not a promise of portability.
- Is an IP68 instrument the same as NEMA 6P?
- They are comparable for submersion, and both are used for submersible level transmitters. The IP rating says how deep and how long; the NEMA type adds the environmental tests. A specification for North America usually asks for the NEMA type or a UL listing, and accepts the IP rating as supporting information.
- Where does DNP3 fit among the IEC protocols?
- DNP3 is IEEE 1815, not an IEC standard, and it is the dominant utility telemetry protocol in North America. IEC 60870-5-104 fills the same role in Europe and elsewhere. They share ancestry and concepts; a SCADA master for a North American water utility speaks DNP3.
- Which IEC 62443 parts should a small utility buy?
- The IEC 62443 page covers the series. For a utility implementing a program: 2-1 for the program, 3-2 for the risk assessment and zoning, and 3-3 for the system requirements. For a utility that only wants the vocabulary, the free summaries and this site are enough to start.
Related topics
- IEC 61131-3The standard behind PLC programming languages: the five languages, the common elements of data types, variables, and program organization units, what conformance actually means, and how the standard shows up in real platforms.
- IEC 62443The international standard series for industrial automation and control system security: how it is organized, what security levels and foundational requirements mean, and how a utility or integrator actually uses it.
- Enclosure SelectionChoosing the box: NEMA and UL 50 type ratings, materials for corrosive and outdoor sites, sizing for heat and wire bending space, and the details at the conduit entries and the door that decide whether the rating survives installation.
- ISA Standards for ControlsThe International Society of Automation standards a controls practitioner meets: ISA-5.1 symbols and tags, ISA-18.2 alarm management, ISA-101 HMI design, ISA-88 and ISA-95 for batch and enterprise integration, ISA-99 which became IEC 62443, ISA-20 specification forms, and how each is used on a water or wastewater project.
- DNP3The protocol built for utility telemetry: master and outstation, static and event data classes, unsolicited reporting, time-stamped events, and why it suits slow links that Modbus does not.
- Interlocks and PermissivesA permissive lets you start. An interlock stops you. Confusing the two produces equipment that either will not run or will not protect itself.
Direct contact
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