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Terms and definitions 1 0
For the purposes of this document, the terms and definitions of IEC 61 326-1 and IEC 60050-1 61 and the following apply
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
• IEC Electropedia: available at http://www.electropedia.org
• ISO Online browing platform: available at http://www.iso.org/obp
Additional definitions essential for applying various tests, which are not found in IEC 60050-1 61 or this standard, can be found in the basic EMC publications of the IEC 61000 series.
A dangerous failure occurs when an element, subsystem, or system essential for executing a safety function either fails to operate when needed (demand mode) or malfunctions during continuous operation, leading to the equipment under control (EUC) being in a hazardous or potentially hazardous state Additionally, such failures reduce the likelihood of the safety function performing correctly when necessary.
3.1 2 equipment subsystems, apparatus, appliances and other assemblies of products
EUC equipment, machinery, apparatus or plant used for manufacturing, process, transportation, medical or other activities
Note 1 to entry: The EUC control system is separate and distinct from the EUC
Functional safety is a critical aspect of overall safety concerning the Equipment Under Control (EUC) and its control system It relies on the proper operation of electrical, electronic, and programmable electronic safety-related systems, along with other measures aimed at risk reduction.
3.1 5 harm physical injury or damage to the health of people, or damage to property or the environment [SOURCE: ISO/IEC Guide 51 :201 4, 3.1 , modifed – "physical" has been added ]
3.1 6 hazard potential source of harm
The term encompasses both immediate threats, like those posed by fire or explosion, and long-term health impacts resulting from the release of toxic substances.
[SOURCE: ISO/IEC Guide 51 :201 4, 3.2, modified – the note to entry has been added]
Safe failure refers to the failure of an element, subsystem, or system involved in executing a safety function This type of failure can either lead to the unintended activation of the safety function, which ensures that the equipment under control (EUC) is placed into or remains in a safe state, or it can heighten the likelihood of such unintended activation occurring.
The safety function is a critical component of an E/E/PE safety-related system or other risk reduction measures, designed to achieve or maintain a safe state for the equipment under control (EUC) in response to specific hazardous events.
EXAMPLE Examples of safety functions include:
– functions that are required to be carried out as positive actions to avoid hazardous situations (for example switching off a motor); and
– functions that prevent actions being taken (for example preventing a motor starting)
PE based on computer technology which may be comprised of hardware, software and of input and/or output units
EXAMPLE The following are all programmable electronic devices:
– application specific integrated circuits (ASICs);
– other computer-based devices (for example smart sensors, transmitters, actuators)
Note 1 to entry: This term covers microelectronic devices based on one or more central processing units (CPUs) together with associated memories, etc
E/E/PE based on electrical (E) and/or electronic (E) and/or programmable electronic (PE) technology
EXAMPLE Electrical/electronic/programmable electronic devices include
– solid-state non-programmable electronic devices (electronic);
– electronic devices based on computer technology (programmable electronic); see 3.2.5 (of IEC 61 326-1 : 201 2)
Note 1 to entry: The term is intended to cover any and all devices or systems operating on electrical principles
[SOURCE:IEC 61 508-4:201 0, 3.2.1 3, modified – the reference in the last dash is modified]
DC distribution network local DC electricity supply network in the infrastructure of a certain site or building intended for connection of any type of equipment
Note 1 to entry: Connection to a local or remote battery is not regarded as a DC distribution network if such a link comprises the power supply for only a single equipment
3.1 1 2 safety-related system designated system that both
• implements the required safety functions necessary to achieve or maintain a safe state for the EUC; and
• is intended to achieve, on its own or with other E/E/PE safety-related systems and other risk reduction measures, the necessary safety integrity for the required safety functions
A safety-related system encompasses all essential hardware, software, and supporting services, such as power supplies, required to perform a designated safety function This includes components like sensors, input devices, actuators, and other output devices integral to the system's operation.
[SOURCE: IEC 61 508-4:201 0, 3.4.1 , modified – notes 1 , 2, 3, 4, 5 and 7 have been removed]
EUT the equipment (devices, appliances and systems) subjected to immunity tests
AE equipment necessary to provide the equipment under test (EUT) with the signals required for normal operation and equipment to verify the performance of the EUT
SSRS specification containing the requirements for the safety functions and their associated safety integrity levels
The Safety Integrity Level (SIL) system consists of four discrete levels, with each level representing a range of safety integrity values Among these, Safety Integrity Level 4 signifies the highest degree of safety integrity.
Note 1 to entry: The target failure measures for the four safety integrity levels are specified in Tables 2 and 3 of IEC 61 508-1 :201 0
Note 2 to entry: Safety integrity levels are used for specifying the safety integrity requirements of the safety functions to be allocated to the E/E/PE safety-related systems
A safety integrity level (SIL) is not an inherent characteristic of a system, subsystem, element, or component Instead, the term “SIL n safety-related system” (where n can be 1, 2, 3, or 4) indicates that the system has the potential to support safety functions with a safety integrity level of up to n.
[SOURCE: IEC 61 508-4:201 0, 3.5.8, modified – the reference to 3.5.1 7 of IEC 61 508-1 has been removed and its date of publication added]
Abbreviations 1 3
E/E/PE electrical/electronic/programmable electronic
ISM industrial, scientific and medical
SSRS system safety requirements specification
This standard outlines specific requirements for systems and equipment used in industrial applications within a defined electromagnetic environment, focusing on safety functions as per the IEC 61 508 series It is important to note that these requirements are not applicable to the normal, non-safety-related functions of the equipment and systems.
The design process and essential features for ensuring the functional safety of electrical and electronic systems are outlined in IEC 61508 This standard specifies requirements for design elements that enhance the system's tolerance to electromagnetic disturbances, as detailed in IEC 61508-2:2010, section 7.4.7.1.
The immunity standards outlined in IEC 61 326-1 are designed to provide sufficient protection for equipment utilized in non-safety-related applications However, these standards do not account for rare extreme scenarios that could potentially arise in any environment.
To prevent dangerous failures caused by electromagnetic phenomena, it is essential to control the environment by establishing installation requirements and limiting the use of mobile transmitters As a systematic measure, increasing immunity test levels is crucial, eliminating the need to consider the impact of electromagnetic phenomena when quantifying hardware safety integrity, such as the probability of failure on demand Enhanced immunity test levels are implemented as needed.
In addition to the immunity requirements of IEC 61 326-1 , the experience with this type of electromagnetic environment is used to specify adequate levels of immunity and adequate performance criteria
Data on fault occurrences have been collected and analyzed to determine adequate performance criteria Annually, over 20,000 units in safety applications are evaluated for failure occurrences, demonstrating that their failure rates comply with SIL requirements Additionally, these units meet the specified EMC requirements necessary for their normal functions within the process industry.
The requirements for a safety-related system designed to implement a specified function and comply with the Safety System Requirements Specification (SSRS) are outlined in IEC 61508 This standard details all pertinent requirements for the intended application, ensuring that equipment used within the system meets the relevant criteria derived from the SSRS.
General 1 3
An EMC test plan shall be established prior to testing It shall contain as a minimum the elements given in 5.2 to 5.6
If any tests are deemed unnecessary to prove compliance with this standard, the rationale for not performing those tests shall be documented in the EMC test plan.
Instruction for testing 1 4
The testing instructions for safety-function immunity must be clear and detailed Therefore, the test plan should comprehensively outline all relevant aspects of the immunity tests At a minimum, the test plan must include essential information regarding the testing process.
• input and output ports relevant for immunity testing,
• configuration of the EUT including any necessary auxiliary and monitoring equipment,
• operation mode of safety functions,
• levels for the immunity test,
• specified performance criteria including the defined state(s),
• monitoring of the behaviour of the EUT,
• assessment of the reaction of the EUT against the manufacturers’ specified performance criteria.
Configuration of EUT during testing 1 4
General 1 4
Measurement, control, and laboratory equipment typically feature systems with flexible configurations, where the types, quantities, and arrangements of various subassemblies can differ significantly between systems.
To accurately simulate EMC conditions, the equipment assembly must reflect a standard installation as outlined by the manufacturer These tests should be conducted as type tests under the manufacturer's specified normal conditions.
In some cases, auxiliary set-ups are necessary to monitor the proper operation of the safety function when electromagnetic disturbances act on the EUT.
Composition of EUT 1 4
All devices, racks, modules, and boards relevant to electromagnetic compatibility (EMC) that are part of the equipment under test (EUT) must be thoroughly documented Additionally, the reasoning behind the selection of the EUT for testing should be clearly outlined in the EMC test plan.
Assembly of EUT 1 4
When an EUT has various internal and external configurations, type tests must be conducted using the most susceptible configuration as anticipated by the manufacturer Each module type should undergo testing at least once, with the rationale for the selected configuration documented in the EMC test plan Additionally, potential electromagnetic interactions between equipment items must be considered when determining the most susceptible configuration, and this rationale should also be included in the EMC test plan.
I/O ports 1 4
When multiple I/O ports of the same type and function are available, connecting a cable to only one port is adequate, as long as it is demonstrated that additional cables do not significantly impact the results This rationale must be documented in the EMC test plan.
Auxiliary equipment (AE) 1 5
To accurately simulate actual operating conditions for the Equipment Under Test (EUT), at least one item from each type of AE must be selected Additionally, any software utilized by AE must be thoroughly documented to ensure that the testing process can be replicated.
It is essential to use an AE that is resistant to electromagnetic disturbances, such as those caused by mechanical equipment, to facilitate the detection and evaluation of the EUT's response.
Cabling and earthing (grounding) 1 5
The cables and earth (ground) shall be connected to the EUT in accordance with the manufacturer's specifications There shall be no additional earth connections.
Operation conditions of EUT during testing 1 5
Operation modes 1 5
A selection of representative operation modes will be made, focusing on the most typical functions of the equipment for testing The worst-case operating modes, as defined within the equipment's specifications for the intended application, will be chosen for evaluation.
NOTE The worst-case operating modes are those most susceptible to electromagnetic phenomena.
Environmental conditions 1 5
Tests must be conducted within the manufacturer's specified environmental operating range, including factors such as ambient temperature, humidity, and atmospheric pressure, as well as within the rated supply voltage and frequency ranges, unless otherwise specified in the test requirements.
EUT software during test 1 5
The software used for exercising the selected modes of operation shall be documented sufficiently to allow repeating the test.
Specification of performance criteria 1 5
Performance criteria for each port and test shall be specified, where possible, as quantitative values.
Test description 1 5
The EMC test plan must specify each test to be conducted, detailing the tests, methods, characteristics, and set-ups as outlined in the basic standards listed in Table 1 While the test plan does not need to replicate the contents of these standards, it should include any additional information necessary for practical test implementation In certain instances, the EMC test plan must provide a detailed specification of the application.
NOTE Not all known disturbance phenomena have been specified for testing purposes in this standard, but only those that are considered as most critical For further information, see Annex B
General 1 6
Performance criteria are used to describe and to assess the reaction of the equipment under test when being exposed to electromagnetic phenomena.
Performance criteria A, B and C 1 6
Performance criterion A is defined in IEC 61 326-1 and is as follows:
The equipment must function as designed during and after testing, with no acceptable degradation in performance or loss of function below the manufacturer's specified performance level when used correctly If the manufacturer does not specify a minimum performance level or permissible performance loss, these can be inferred from the product description and documentation, as well as the user's reasonable expectations for intended use.
Performance criteria B and C are not appropriate for functional safety.
Performance criterion DS 1 6
Definition of performance criterion DS 1 6
For functional safety purposes, the performance criterion DS must be applied, which pertains to the functions of the Equipment Under Test (EUT) that are intended for use in safety applications.
1 ) are not affected outside their specification, or
2) may be affected temporarily or permanently (even by destruction of components), if the EUT reacts to a disturbance in a way that a detectable and defined state(s) of the EUT is (are) i) maintained, or ii) achieved within a stated time b) The functions not intended for use in safety applications may be disturbed temporarily or permanently
NOTE 1 It is possible for the defined state to be outside normal operating limits
NOTE 2 Edition 1 of this standard used the abbreviation FS for that performance criterion According to the basic standard IEC 61 000-1 -2 and generic standard IEC 61 000-6-7, the abbreviation DS is used now without having changed the technical content.
Application of the performance criterion DS 1 6
The performance criterion DS is specifically designed for functions of the EUT that are intended for safety applications It applies to all phenomena without distinction, encompassing both continuous and transient electromagnetic phenomena.
Safety equipment must operate according to defined performance criteria to ensure safe conditions for both the equipment and its controlled systems It is essential that the behavior of these safety-related systems is predictable under all anticipated conditions.
In systems where equipment serves both safety and non-safety functions, the requirements for functional safety are applicable solely to the safety functions.
Assessing safety functions based on the performance criterion DS requires precise monitoring of the Equipment Under Test (EUT) It is essential to clearly define the performance criterion DS Often, specific auxiliary equipment is needed to accurately identify and monitor the proper operation of the safety function Additionally, it is crucial to ensure that this auxiliary equipment does not interfere with the EUT's behavior during immunity tests.
Aspects to be considered during application of performance criterion DS 1 7
To ensure that an EUT consistently reaches the defined state in response to a disturbance, it is essential to verify that this behavior is reproducible rather than a one-time occurrence The reproducibility must be confirmed by applying the performance criteria outlined in Table 1.
Table 1 – Reaction of EUT during test
Test Reaction of EUT during test How to continue with testing
Transient a The EUT goes to a defined state and an interaction of the user is needed to continue operation
The Equipment Under Test (EUT) must be restored to normal operation, and the test should be repeated three times at the same test level and polarity, ensuring that the EUT consistently meets the performance criterion DS If the EUT complies, the testing will proceed to the next test level or polarity as outlined in the basic standard.
The Equipment Under Test (EUT) may reach a defined state of permanent damage, necessitating its replacement or repair The testing process must then be repeated three times at the same test level and polarity, ensuring that the EUT consistently meets the performance criterion DS If successful, the testing will proceed to the next test level or polarity as outlined in the basic standard.
Continuous b The EUT goes to a defined state at a certain test frequency as described under a) 2) in 6 3.1
The EUT shall be re-tested 3 times at that frequency and the EUT shall react in a way that complies with performance criterion DS each time
If the EUT reacts each time in the same way, the subsequent frequencies may be tested only one time per frequency a Tests according IEC 61 000-4-2, IEC 61 000-4-4, IEC 61 000-4-5, IEC 61 000-4-1 1 , IEC 61 000-4-29,
IEC 61 000-4-34 b Tests according IEC 61 000-4-3, IEC 61 000-4-6, IEC 61 000-4-8, IEC 61 000-4-1 6
Table 2 to Table 7 list the immunity test requirements
Some test values in Tables 2 to 7 are less stringent than those specified in the generic EMC standard IEC 61000-6-7 According to IEC Guide 107, if a product family or product EMC standard sets less stringent test values or only partially addresses a phenomenon, a justification or reference to another EMC standard must be provided This reference may include IEC 61326-3-2:2008, from which the requirements of this standard were derived and validated in practice.
Table 2 – Immunity test requirements – Enclosure port
Phenomenon Basic standard Tests for functions intended for safety applications
(ESD) IEC 61 000-4-2 ± 6 kV contact discharge a ± 8 kV air discharge a
1 2 Electromagnetic field IEC 61 000-4-3 1 0 V/m (80 MHz to 1 GHz, 1 kHz (80 % AM))
1 0 V/m (1 ,4 GHz to 2 GHz, 1 kHz (80 % AM))
3 V/m (2,0 GHz to 2, 7 GHz, 1 kHz (80 % AM))
3 V/m (2,7 GHz to 6, 0 GHz, 1 kHz (80 % AM)) b
The rated power frequency magnetic field, as specified in IEC 61000-4-8, is set at 100 A/m These values must be applied according to the environmental conditions outlined in IEC 61000-4-2, particularly for parts accessible to individuals other than trained staff managing ESD control procedures Testing within this frequency range is necessary only if mandated by the specific application and is relevant solely for equipment that includes devices sensitive to magnetic fields.
Table 3 – Immunity test requirements – Input and output AC power ports
Phenomenon Basic standard Tests for functions intended for safety applications
2.1 Burst IEC 61 000-4-4 2 kV (5/50 ns, 5 kHz) A
2.2 Surge IEC 61 000-4-5 1 kV (line to line)
2.3 Conducted RF IEC 61 000-4-6 1 0 V (1 50 kHz to 80 MHz, 1 kHz (80 % AM)) A 2.4 Voltage dips IEC 61 000-4-1 1 or IEC 61 000-4-34
2.5 Short interruptions IEC 61 000-4-1 1 or IEC 61 000-4-34
2.6 Conducted common mode voltage IEC 61 000-4-1 6 1 0 V (1 0 kHz to 1 50 kHz) A a “1 0/1 2 cycles” means “1 0 cycles for 50 Hz test” and “1 2 cycles for 60 Hz test” (and similarly for 25/30 cycles and 250/300 cycles)
Table 4 – Immunity test requirements – Input and output DC power ports
Phenomenon Basic standard Tests for functions intended for safety applications
3.1 Burst IEC 61 000-4-4 2 kV (5/50 ns, 5 kHz) A
3.2 Surge IEC 61 000-4-5 0,5 kV (line to line)
3.3 Conducted RF IEC 61 000-4-6 1 0 V (1 50 kHz to 80 MHz, 1 kHz (80 % AM)) A
3.4 Conducted common mode voltage IEC 61 000-4-1 6 1 0 V (1 0 kHz to 1 50 kHz) A
3.5 Voltage dips IEC 61 000-4-29 40 % U T for 1 000 ms
3.6 Short interruptions IEC 61 000-4-29 0 % U T for 20 ms A
DC connections between parts of equipment/system which are not connected to a DC distribution network are treated as I/O signal/control ports (see Tables 5 or 6)
Phenomenon Basic standard Tests for functions intended for safety applications
4.1 Burst IEC 61 000-4-4 1 kV (5/50 ns, 5 kHz) a A
4.2 Surge IEC 61 000-4-5 1 kV (line to ground) b DS
4.3 Conducted RF IEC 61 000-4-6 1 0 V (1 50 kHz to 80 MHz, 1 kHz (80 % AM)) a A
4.4 Conducted common mode voltage IEC 61 000-4-1 6 1 0 V (1 0 kHz to 1 50 kHz) a A a Only in case of lines > 3 m b Only in case of long distance lines (see 3.1 0 of IEC 61 326-1 : 201 2)
Table 6 – Immunity test requirements – I/O signal/control ports connected directly to power supply networks
Phenomenon Basic standard Tests for functions intended for safety applications
5.1 Burst IEC 61 000-4-4 2 kV (5/50 ns, 5 kHz) A
5.2 Surge IEC 61 000-4-5 1 kV (line to line)
5.3 Conducted RF IEC 61 000-4-6 1 0 V (1 50 kHz to 80 MHz, 1 kHz (80 % AM)) A 5.4 Conducted common mode voltage IEC 61 000-4-1 6 1 0 V (1 0 kHz to 1 50 kHz) A
Table 7 – Immunity test requirements – Functional earth port
Phenomenon Basic standard Tests for functions intended for safety applications
6.1 Burst IEC 61 000-4-4 2 kV (5/50 ns, 5 kHz) a A
6.2 Surge IEC 61 000-4-5 1 kV (line to ground) b DS
6.3 Conducted RF IEC 61 000-4-6 1 0 V (1 50 kHz to 80 MHz, 1 kHz (80 % AM)) A
6.4 Conducted common mode voltage IEC 61 000-4-1 6 1 0 V (1 0 kHz to 1 50 kHz) A a Only in case lines > 3 m b Only in case of long distance lines (see 3.1 0 of IEC 61 326-1 : 201 2)
8 Test set-up and test philosophy for EUT with functions intended for safety applications
Testing of safety-related systems and equipment intended to be used in safety-related systems
Safety-related systems can involve intricate and extensive installations with diverse physical configurations Conducting immunity testing on these systems is challenging and often impractical when relying solely on the basic standards outlined in Tables 2.
7 Hence, corresponding immunity tests shall be carried out preferably on equipment level as it is described in 8.2
For compact safety-related systems, immunity tests can be conducted on the complete system as outlined in section 8.3 If a different testing approach is adopted, it must be detailed in the EMC test plan along with a justification for its implementation.
Test philosophy for equipment intended for use in safety-related systems
Functional safety necessitates the proper operation of the entire system, which includes sensors, logic solvers, and actuators; however, individual devices can be tested separately Each device intended for use in a safety-related system must be thoroughly specified, detailing its intended function and permissible behavior in the event of a failure The goal of immunity testing is to demonstrate that the specifications are met concerning the relevant electromagnetic phenomena.
The potential danger of a disturbed function remains uncertain, as it relies on its future use in a safety-related system Consequently, testing must reveal the behavior of the Equipment Under Test (EUT) Any deviations from normal functions must be identifiable and documented in the test report.
The DS performance criterion imposes extra requirements on equipment designed for safety-related applications, necessitating compliance with both standard performance criteria and the DS performance criterion within their specified limits.
NOTE The general approach of applying performance criteria for the different types of functions is shown in Table 1 0 of IEC 61 326-3-1 : 2
2 Under preparation Stage at the time of publication: IEC/DIS 61 326-3-1 :201 6
Test philosophy for safety-related systems
The EUT will be monitored throughout the testing process to ensure its functionality meets the required standards, and this monitoring system must remain unaffected by any electromagnetic disturbances during the tests.
In safety-related systems, the intended functions and potential safe states are clearly defined The purpose of immunity tests is to verify that the system operates according to the manufacturer's specifications and meets the performance criterion DS outlined in Clause 6.
The performance criteria for functional safety place additional requirements on the equipment that is intended for use in safety-related applications.
Test configuration and test performance
Figure 1 illustrates a standard test setup for equipment designed for safety-related systems, whether tested as standalone units or as part of an entire system In this configuration, the immunity tests focus solely on the equipment under test (EUT), ensuring that other devices used during the testing process are shielded from electromagnetic interference This setup is also applicable when evaluating a safety-related system in its entirety.
Figure 2 illustrates a standard test setup for equipment designed for safety-related systems, ensuring that the immunity tests focus on the equipment under evaluation In this configuration, additional devices operating the Equipment Under Test (EUT) are isolated from any electromagnetic interference.
If the Equipment Under Test (EUT) does not constitute a complete safety-related system, its ports must be linked to additional components that replicate the safety system, such as sensors, logic elements, actuators, or other loads that mimic the properties of real elements.
The EUT must work in conjunction with safety system devices essential for its operation and for executing its designated safety functions.
For equipment combinations utilizing safety logic solver software in accordance with IEC 61508, immunity tests must be conducted on at least one representative combination Proof of immunity for other combinations can be established through suitable analytical evidence.
The essential AE required for the EUT's functionality and safety applications must be installed in a secure electromagnetic environment It is crucial that these AE remain unaffected by electromagnetic disturbances during testing.
The relevant I/O ports of the Equipment Under Test (EUT) must be connected to the corresponding ports of the safety-related system devices This connection is essential for the EUT's functionality and for executing safety application functions.
Cables and I/O ports of the EUT that are not used shall be terminated as specified by the manufacturer
Only cables specified by the manufacturer of the EUT or the safety system shall be used in the test set-up
Standardized testing methods for communication links utilized in safety functions are highly recommended For instance, refer to IEC 61784-3 for field bus communications.
The safety functions of the safety-related system must be tested sequentially and in designated combinations Immunity tests are conducted while the safety function is in a static state, meaning the safety function is activated prior to performing the test.
Immunity tests are optional during the activation or deactivation of safety functions, although manufacturers may choose to include them in their testing plans.
Monitoring
The monitoring system must not impact the behavior of the Equipment Under Test (EUT) If it is unavoidable, the degree of influence must be clearly documented Importantly, the safety-related functions of the EUT must remain unaffected by the monitoring system at all times.
The monitoring system shall observe, if applicable,
• the data communication between the EUT and the devices, which are necessary for the function of the EUT and for performing the function intended for safety application; and
• the status of the safety outputs whose functions are intended for safety applications
9 Test results and test report
The test results shall be documented in a comprehensive test report with sufficient detail to provide for test repeatability
The test report shall contain the following minimum information:
– the items specified in the test plan;
– test equipment and set-up;
– the behaviour observed during the test
A EUT: safety related system under test
C grounding point for shielded cable(s) (if required by the manufacturer)
D decoupling network(s) at the interface between the EUT and the electromagnetically decoupled environment
E EUT grounding point (if required by the manufacturer)
P shielded monitoring cable(s) (any necessary, and all safety-related functions)
T EUT port terminations (grounded if required by the manufacturer)
U unshielded monitoring cable(s) (any necessary, and all safety-related functions)
Figure 1 – Typical test set-up for equipment intended for use in safety-related system, tested as stand-alone equipment or entire system
A EUT: part of the safety-related system under test
B part of the safety-related system not under test, and auxiliary devices
C grounding point for shielded cable (if required by the manufacturer)
D decoupling network(s) at the interface between the EUT and the electromagnetically decoupled environment
E EUT grounding point (if required by the manufacturer)
P shielded monitoring cable(s) (any necessary, and all safety-related functions)
S safety-related system output – monitored
T EUT port terminations (grounded if required by the manufacturer)
U unshielded monitoring cables (any necessary, and all safety-related functions)
Figure 2 – Typical test set-up for equipment intended for use in a safety-related system integrated into a representative safety-related system during test
Annex A (informative) Approaches on how to apply IEC 61 326-3 series
There are two primary approaches to addressing electromagnetic environments and determining immunity requirements The first approach involves assessing a general electromagnetic environment, such as an industrial setting, by considering all potential electromagnetic phenomena and their maximum amplitudes to establish appropriate immunity levels This method has led to higher immunity levels for certain phenomena compared to those derived without considering functional safety The second approach focuses on controlling the electromagnetic environment through specific installation and mitigation practices, limiting the occurrence and amplitude of electromagnetic phenomena The immunity levels derived from this controlled environment may not be higher than those established without functional safety considerations, as measures are in place to ensure that higher amplitudes are not typically expected This document adopts the latter approach.
Applying approach (b) establishes a defined electromagnetic environment through strict adherence to specific installation and mitigation practices It is essential to possess adequate knowledge of electromagnetic phenomena and the expected amplitude levels within this environment This understanding is derived from analyzing statistical data on faults in safety applications within the process industry, where over 20,000 units are evaluated annually for failure occurrences The findings indicate that the failure rates align with the safety integrity level (SIL) requirements, ensuring compliance with the electromagnetic compatibility (EMC) standards of the process industry.
IEC 61 326-3-2 outlines specific electromagnetic immunity requirements for safety-related systems and equipment used in safety applications These requirements enhance those found in IEC 61 326-1 and align with comparable EMC standards in the process industry The selected electromagnetic phenomena and defined immunity test levels are designed to correspond with the environmental conditions of the specified industrial applications as detailed in the standard's scope.
The correlation between the standards IEC 61 326-1 , IEC 61 326-2-X, IEC 61 326-3-1 and IEC 61 326-3-2 is described in Figure A.1
This document outlines test levels based on the maximum expected conditions in industrial environments, specifically addressing the electromagnetic environment These levels cannot be analytically linked to the Safety Integrity Level (SIL) of safety-related systems, as no proven relationship exists between test levels and failure probabilities Electromagnetic phenomena are viewed as systematic effects that frequently lead to common cause events.
The design features of equipment must consider the necessary Safety Integrity Level (SIL) and be structured to prevent dangerous systematic failures To ensure adequate immunity against electromagnetic disturbances, it is essential to implement design, mitigation, and construction techniques that address electromagnetic factors, although these aspects are beyond the scope of this document.
To achieve the necessary Safety Integrity Level (SIL), it is advisable to adopt specific design features while also implementing suitable test performance parameters This dual approach will enhance confidence in the test results.
NOTE This flowchart is not intended to give requirements about the sequence of test
Figure A.1 – Correlation between the standards IEC 61 326-1 , IEC 61 326-2-x, IEC 61 326-3-1 and IEC 61 326-3-2
Test functions against performance criteria under electromagnetic test values according to IEC 61 326-1 and/or IEC 61 326-2-x
Is intended for use in a safety-related application ? See Clause 1
Suitable for its intended application and environment
Is intended for use in a specified electromagnetic environment ?
Approach (A) Test safety functions against performance criteria, under electromagnetic test values according to IEC 61 326-3-1
NOT suitable for its intended application
Suitable for its intended safety-related application in general industrial environments
Approach (B) Test safety functions against performance criteria, under electromagnetic test values according to IEC 61 326-3-2 (and IEC 61 326-3-1 Table 1 0)
Suitable for its intended safety-related application in specified industrial electromagnetic environments
NOT suitable for its intended application
Annex B (informative) Evaluation of electromagnetic phenomena
The relationship between electromagnetic compatibility (EMC) and safety is critical, as safety failures can have severe consequences Establishing EMC requirements for safety-related equipment and systems necessitates thorough discussions among all stakeholders Relevant IEC standards, such as IEC 61508 and IEC 61000-1-2, address EMC and functional safety, with both referencing IEC TR 61000-2-5 for further guidance.
The test levels outlined in this standard are derived from statistical evaluations conducted by NAMUR, the user association for automation in the process industry, which analyzed over 23,000 units used in safety instrument applications as of 2003 This evaluation confirms that the devices fulfill the requirements for Safety Integrity Level (SIL) 2.
3 safety instrument applications The corresponding test levels are given in Annex C
The article presents a proposal for deriving immunity levels that incorporates expert knowledge on electromagnetic compatibility and various electromagnetic phenomena, as detailed in Table B.1 It also includes a comparison of these proposed immunity levels with those established in IEC 61 326-1 for industrial applications.
Table B.1 – General considerations for the application of electromagnetic phenomena for functional safety in industrial applications with specified electromagnetic environment (examples)
No Phenomena Basic standard Increased level a Comments
1 Electrostatic discharge (ESD) IEC 61 000-4-2 Yes next level of IEC
Levels must be implemented based on the environmental conditions outlined in IEC 61000-4-2 for areas that may be accessed by individuals other than personnel following established ESD control procedures.
Access to equipment is limited to appropriately trained personnel only
2 Electromagnetic field IEC 61 000-4-3 Yes, depending on frequency range
Increased frequency levels will be implemented for mobile transmitters, unless effective measures are in place to prevent the use of such equipment in close proximity It is essential to consider ISM frequencies on a case-by-case basis.
3 Burst IEC 61 000-4-4 No Because of use of dedicated cables for power, I/O and communication and the separation of this cable this phenomena is limited to normal levels
Surge protection in accordance with IEC 61000-4-5 is essential to mitigate the effects of overvoltage and lightning Implementing appropriate measures, such as utilizing a metal building structure or installing protective devices, helps to maintain these phenomena within normal levels.
5 Conducted RF IEC 61 000-4-6 Yes, with expanded frequency range
With the increasing prevalence of frequency-driven motors and switching-mode power supplies that generate low-frequency disturbances, there is a pressing need for elevated testing levels and a broader frequency range.
6 Power frequency magnetic field IEC 61 000-4-8 Yes According to the use of high currents produced by (pipe) heating systems driven by AC mains a higher test level is needed
9 Conducted common mode voltages IEC 61 000-4-1 6 No
1 0 Voltage dips IEC 61 000-4-29 Yes According to the use of DC power distribution networks in the process industry, tests are needed
1 1 Short interruptions IEC 61 000-4-29 Yes According to the use of DC power distribution networks in the process industry, tests are needed
1 3 Short interruptions IEC 61 000-4-34 No a “Increased level” compared to the test levels of IEC 61 326-1 for industrial applications
Annex C (normative) Specified electromagnetic environment
General
To ensure compliance with this standard, it is essential to control the electromagnetic environment at the industrial installation site Implementing specific mitigation measures, as outlined in Annex C, is necessary to achieve the defined electromagnetic environment All relevant measures detailed in Annex C must be applied to meet the requirements of the specified environment.
The mitigation measures outlined in this article are derived from NAMUR Recommendation 98, which focuses on installation requirements for achieving electromagnetic compatibility (EMC) in production environments NAMUR, the user association for automation in process industries, emphasizes the importance of these guidelines for users of process control technology, while excluding manufacturers of related hardware and software from membership For more information, visit www.namur.de.
Industrial area with limited access
Access to the industrial plant will be regulated to ensure safety, with all employees and visitors informed about access restrictions, the use of mobile transmitters, and essential rules to safeguard the environment from electromagnetic phenomena.
Limited use of mobile transmitters
Mobile transmitters in sensitive areas are subject to access restrictions determined by the calculation of minimum protective distances for sensitive equipment However, for low power devices operating at frequencies above 2 GHz, typically below 100 mW ERP, access limitations are not required.
The protective distances, assuming to have field strength levels below 1 0 V/m, are typically:
• for GSM telephones approx 1 ,0 m (max P ERP = 2 W)
• for DECT telephones approx 0,35 m ( P ERP = 0,25 W)
• for mobile radio devices approx 1 ,6 m (P ERP = 5 W)
To calculate these distances, the following expression is used: d
E = 30 ⋅ G a ⋅ where d is the distance from the transmission antenna in m;
P is the input power (ERP) to the transmitting antenna in W;
E is the electric field strength in V/m under far field conditions
G a is the absolute gain of the antenna; for a half-wavelength dipole antenna the gain G a is 1 ,64 (2,1 5 dB)
The calculation is done assuming a half-wavelength dipole antenna Reflective and absorbent objects in the near vicinity can amplify or weaken the electromagnetic field by a factor of 2
More detailed information for determination of field strengths in near field and far field can be found in Annex B of IEC TR 61 000-2-5:201 1
Dedicated cables for power supply and control, signal or communication
With regard to their potential in emitting or receiving disturbances, cable connections are divided into three different categories
Signal cables for PLC/PCS, including measurement signal cables for 4 mA to 20 mA, communication cables, and cables for field bus/system bus, are essential for effective data transmission For low-level signals, it is advisable to utilize pairs of twisted wires to minimize interference and ensure signal integrity.
• Low-voltage (LV) power cables (up to 1 kV)
DC power cables (even < 1 1 0 V) and low-voltage power cables (for example, for lighting systems, sockets, motors, magnetic valves, heat tracing systems)
• High-voltage (HV) power cables ( > 1 kV)
Power cables and other cables carrying medium or high voltage
These cable categories shall be physically separated, see Clause C.5.
Separation between power supply and control, signal or communication
Different categories of cable shall be laid separately The separation distance is a minimum of
30 cm, or a metallic separating septum is used in the cable duct/tray Particularly high-voltage power cables shall not be laid together with other cable categories
To minimize the coupling of symmetric signals, it is essential to group functionally related wire pairs within the same cable Additionally, cables designated for auxiliary power supplies should be installed separately from control cables.
Control cables shall be separated from bus bars and power transformers
Figure C.1 shows the recommended cable layouts for different categories
1 signal cable A different categories of cables separated by metallic separation web
2 low-voltage power cable B different categories of cables separated by distance between them
3 earth connection C different categories of cables separated by using different metallic cable trays or by distance if not metallic
Figure C.1 – Recommended cable layouts for different categories
Factory building mostly consisting of metal construction
The buildings of the factory consist of reinforced concrete or metal construction
Metal construction and reinforcement of concrete shall be welded or bonded together to improve the equipotential bonding effect.
Overvoltage/lightning protection by appropriate measures
A comprehensive overvoltage and lightning protection strategy is essential for factories and plants, which may include metal building structures or specialized protection devices The implemented overvoltage/lightning protection system must effectively mitigate overvoltages resulting from lightning strikes or switching actions, ensuring that all conductors maintain a safe voltage level relative to ground potential.
The EMC-orientated lighting protection concept divides the building system into lightning protection zones in direct relation to the interference sensitivity of individual system areas:
• Zone 1 /Class B, lightning conductor (formerly rough protection),
• Zone 2/Class C, overvoltage protector (formerly medium protection),
• Zone 3/Class D, overvoltage protector (formerly fine protection)
External lightning protection includes interception devices, conductors, and an earthing system, while internal lightning protection features equipotential bonding, surge arrestors, cable shielding, and potential equalization or signal balancing.
A low-impedance connection must be established between the lightning protection system and the building's electrical system earth electrode, as well as with nearby building earths, metallic structures, pipe bridges, pipelines, and rail systems This connection is usually made using copper shield braiding of at least 16 mm², grounding cables ranging from 70 mm² to 300 mm², or steel strips.
Pipe heating systems driven by AC mains
Pipe heating systems are present in many parts of the factory These heating systems which are driven by AC mains generate high magnetic fields.
No high-voltage substations close to sensitive areas
High-voltage substations shall be located outside sensitive areas to prevent extreme high magnetic fields or electric fields
C.1 0 Presence of low-power devices using ISM frequencies according to
326-3-1 and 326-3-2
Electrical equipment for measurement, control and laboratory use – EMC requirements –
Part 3-2: Immunity requirements for safety-related systems and for equipment intended to perform safety-related functions (functional safety) – Industrial applications with specified electromagnetic environment
Matériel électrique de mesure, de commande et de laboratoire – Exigences relatives à la CEM –
Partie 3-2: Exigences d'immunité pour les systèmes relatifs à la sécurité et pour les matériels destinés à réaliser des fonctions relatives à la sécurité
(sécurité fonctionnelle) – Applications industrielles dont l’environnement électromagnétique est spécifié
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Electrical equipment for measurement, control and laboratory use – EMC requirements –
Part 3-2: Immunity requirements for safety-related systems and for equipment intended to perform safety-related functions (functional safety) – Industrial applications with specified electromagnetic environment
Matériel électrique de mesure, de commande et de laboratoire – Exigences relatives à la CEM –
Partie 3-2: Exigences d'immunité pour les systèmes relatifs à la sécurité et pour les matériels destinés à réaliser des fonctions relatives à la sécurité
(sécurité fonctionnelle) – Applications industrielles dont l’environnement électromagnétique est spécifié
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5.3 Configuration of EUT during testing 1 4
5.4 Operation conditions of EUT during testing 1 5
6.3.1 Definition of performance criterion DS 1 6
6.3.2 Application of the performance criterion DS 1 6
6.3.3 Aspects to be considered during application of performance criterion DS 1 7
8 Test set-up and test philosophy for EUT with functions intended for safety applications 20
8.1 Testing of safety-related systems and equipment intended to be used in safety-related systems 20
8.2 Test philosophy for equipment intended for use in safety-related systems 20
8.3 Test philosophy for safety-related systems 21
8.4 Test configuration and test performance 21
9 Test results and test report 22
Annex A (informative) Approaches on how to apply IEC 61 326-3 series 25
Annex B (informative) Evaluation of electromagnetic phenomena 27
Annex C (normative) Specified electromagnetic environment 29
C.2 Industrial area with limited access 29
C.3 Limited use of mobile transmitters 29
C.4 Dedicated cables for power supply and control, signal or communication lines 30
C.5 Separation between power supply and control, signal or communication cables 30
C.6 Factory building mostly consisting of metal construction 31
C.7 Overvoltage/lightning protection by appropriate measures 31
C.8 Pipe heating systems driven by AC mains 32
C.9 No high-voltage substations close to sensitive areas 32
C.1 0 Presence of low-power devices using ISM frequencies according to
C.1 2 Periodic maintenance of equipment and systems 32
C.1 3 Installation guidelines for equipment and systems 32
Annex D (informative) Example of immunity levels in the process industry 33
Figure 1 – Typical test set-up for equipment intended for use in safety-related system, tested as stand-alone equipment or entire system 23
Figure 2 – Typical test set-up for equipment intended for use in a safety-related system integrated into a representative safety-related system during test 24
Figure A.1 – Correlation between the standards IEC 61 326-1 , IEC 61 326-2-x,
Figure C.1 – Recommended cable layouts for different categories 31
Table 1 – Reaction of EUT during test 1 7
Table 2 – Immunity test requirements – Enclosure port 1 8
Table 3 – Immunity test requirements – Input and output AC power ports 1 8
Table 4 – Immunity test requirements – Input and output DC power ports 1 9
Table 5 – Immunity test requirements – I/O signal/control ports 1 9
Table 6 – Immunity test requirements – I/O signal/control ports connected directly to power supply networks 1 9
Table 7 – Immunity test requirements – Functional earth port 20
Table B.1 – General considerations for the application of electromagnetic phenomena for functional safety in industrial applications with specified electromagnetic environment (examples) 28
Table D.1 – Immunity test requirements for equipment intended for use in industrial locations with a specified electromagnetic environment according to NE 21 34
Part 3-2: Immunity requirements for safety-related systems and for equipment intended to perform safety-related functions (functional safety) – Industrial applications with specified electromagnetic environment
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International Standard IEC 61 326-3-2 has been prepared by subcommittee 65A: System aspects, of IEC technical committee 65: Industrial-process measurement, control and automation