Standards for PLC Engineers: Programming, Machine Safety, Electrical Design, Networks and Security
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PLC projects sit at the meeting point of software, electrical engineering, machine safety and IT security, so several families of standards apply at once. Engineers do not need to know every clause, but they must know which standard governs which decision and which ones their customer, market or regulator makes mandatory. This page maps the main standards to PLC tasks. Always check current editions and local legal requirements.
Controllers and programming
| Standard | Scope |
|---|---|
| IEC 61131-1 | General information and definitions for programmable controllers |
| IEC 61131-2 | Equipment requirements and tests (environmental, electrical) |
| IEC 61131-3 | Programming languages: LD, FBD, ST, SFC (IL deprecated in 2013); see PLC Programming Languages |
| IEC 61131-6 | Functional safety for programmable controllers |
| IEC 61499 | Event-driven function blocks for distributed, portable control applications |
| PLCopen | Specifications built on IEC 61131-3: motion control function blocks, safety function blocks, coding guidelines, XML exchange, OPC UA information model |
Machine safety
| Standard | Scope |
|---|---|
| ISO 12100 | General principles for machine design, risk assessment and risk reduction |
| ISO 13849-1 / -2 | Safety-related parts of control systems: performance levels (PL a to e), categories, validation |
| IEC 62061 | Functional safety of machinery control systems using SIL |
| IEC 60204-1 | Electrical equipment of machines, including emergency stop and control circuit requirements |
| NFPA 79 | Electrical standard for industrial machinery (United States) |
| Machinery Directive 2006/42/EC → Machinery Regulation (EU) 2023/1230 | EU legal requirements for machinery; the Regulation applies from 20 January 2027 |
A safety function (for example stopping a machine when a guard opens) is designed with ISO 13849-1 or IEC 62061, implemented with safety-rated devices and safety PLCs, and validated before use. See Functional Safety.
Process safety
| Standard | Scope |
|---|---|
| IEC 61508 | Generic functional safety standard for electrical, electronic and programmable systems |
| IEC 61511 | Safety instrumented systems in the process industry |
PLCs used as safety logic solvers in process plants must be certified for the required SIL and applied according to the vendor’s safety manual.
Panels and electrical installation
| Standard | Scope |
|---|---|
| IEC 61439 | Low-voltage switchgear and controlgear assemblies (control panels in many regions) |
| UL 508A | Industrial control panels (North America) |
| IEC 60947 series | Low-voltage switchgear: contactors, circuit breakers, control devices |
| IEC 61000 series | Electromagnetic compatibility |
| NFPA 70E | Workplace electrical safety (United States), relevant when working on live panels |
| IEC 60079 series | Equipment in explosive atmospheres |
See Instrumentation and Electrical Best Practices and Grounding and Earthing.
Networks and communication
| Standard | Scope |
|---|---|
| IEC 61158 / IEC 61784 | Fieldbus and industrial Ethernet protocols and profiles (PROFINET, EtherNet/IP, EtherCAT and others) |
| IEC 62541 | OPC UA |
| Modbus specification | Modbus application protocol (Modbus Organization) |
See Industrial Communication Protocols.
Cybersecurity
ISA/IEC 62443 covers security programmes for asset owners (62443-2-1), system design with zones and conduits (62443-3-2, 3-3), secure product development (62443-4-1) and component requirements (62443-4-2). Several PLC families are certified to parts of it. See PLC Security and ISA/IEC 62443.
Integration and batch
| Standard | Scope |
|---|---|
| ISA-88 / IEC 61512 | Batch control models and recipes; see ISA-88 |
| ISA-95 / IEC 62264 | Integration of control with MES and ERP; see ISA-95 |
| OMAC PackML (ISA-TR88.00.02) | Standard machine states and modes for packaging machines |
Standards by project phase
| Phase | Typical standards |
|---|---|
| Requirements and risk | ISO 12100, customer standards, IEC 62443 risk assessment |
| Safety design | ISO 13849-1, IEC 62061 or IEC 61511 |
| Electrical design | IEC 60204-1 or NFPA 79, IEC 61439 or UL 508A, IEC 61000 |
| Programming | IEC 61131-3, PLCopen, company coding standard, PackML where required |
| Testing | ISO 13849-2 validation, FAT/SAT per contract |
| Operation | IEC 62443 security maintenance, management of change |
See PLC Project Process.
Frequently asked questions
What is the main standard for PLCs?
IEC 61131, especially part 3, which defines the programming languages. Other standards cover safety, electrical design, networks and security.
Which standards apply to PLC safety functions on machines?
ISO 12100 for risk assessment, ISO 13849-1 or IEC 62061 for the design of safety functions, IEC 60204-1 or NFPA 79 for electrical equipment, and the Machinery Directive or Regulation in the EU.
What is PackML?
A standard set of machine states and modes (for example idle, starting, execute, held, stopped, aborted) for packaging and similar machines, published as ISA-TR88.00.02, which makes machines from different suppliers behave consistently.
Key takeaways
- IEC 61131-3 governs PLC languages; PLCopen extends it for motion, safety and exchange.
- Machine safety follows ISO 12100, ISO 13849-1 or IEC 62061, and IEC 60204-1 or NFPA 79.
- Panels, EMC, networks and security have their own standards.
- Map standards to project phases and name them in specifications.
Related tutorials
Before you apply this in a plant: this article is for education. Always check the current edition of the relevant standards, the manufacturer's documentation for your exact product and version, and your site's procedures. Safety-related work needs qualified personnel. See our editorial policy.