“the ability of equipment or a system to function satisfactorily in its electromagnetic environment without introducing intolerable electromagnetic disturbances to anything in that environment”
For the situations where EM interference (EMI) could lead to a safety hazard, special design and testing procedures need to be applied. For Functional Safety applications, the safety integrity level (SIL) of the equipment must be considered and if the equipment fails, it must be designed to fail safely.
Is defined as part of overall safety of system that depends upon the correct functioning of electrical and/or electronic equipment in response to its inputs. Functional safety is safety achieved by active systems e.g. Smoke detection by sensors and intelligent activation of evacuation and fire suppression systems. Basic standard that covers Functional safety is IEC 61508
The approach to achieve Functional Safety is to carefully evaluate the product design for Functional Safety failure modes in the presence of EMI. There is also a need to consider life cycle design, the operation of equipment and to test the product to ensure that its safety function is maintained or fails safely. This approach is in addition to the normal EMC design and testing practices
Functional Safety is not regulated by the EMC DirectiveThere exist a misconception across the industry that all that is needed to control EM interference for all purposes in the EU is to manufacture (or purchase) apparatus which is CE marked and declared compliant with the EMC Directive [EU 2014/30/EU]. Here are some basic reasons why this stays incorrect
- The EMC Directive does not use the word “safety” anywhere in its text
- The EMC Directive only covers normal operation and does not cover reasonably foreseeable faults, environmental extremes, operator errors, maintenance situations, or misuse – all considerations which are essential for functional safety
- The EMC standards harmonized under the EMC Directive either explicitly or implicitly exclude safety considerations
- The EMC standards harmonized under the EMC Directive (or R&TTE Directive, RED- Latest) cover a restricted number of EM disturbances, and their limits allow a finite probability of incompatibilities
- EMC Technical Construction Files (TCFs) can include significantly lower EMC performance (or lower confidence of performance) than would have been achieved had the harmonized standards been applied in full, also a Competent Body would not usually assess a TCF for safety
- Train detection systems (including track circuits and axle counters)
- Interlocking systems c) signals and point operating equipment and their controlling circuits
- Train warning and protection systems
- Telecommunications systems (including voice and data transmission, and supervisory control and data acquisition (SCADA) systems)
- Radio systems (including voice and data transmission, fixed and mobile systems).