Intrinsic safety
The intrinsic safety (Engl. Intrinsic safety) is a technical feature of a device or system that ensures due to specific design principles that even in the event of a fault , no unsafe condition occurs. This can be achieved through predetermined breaking points, special power sources or other measures so that a dangerous situation cannot arise. The error case describes situations for which there is a risk. For example, the possibility of sparks forming when an electrical circuit is closed is only fraught with risk within potentially explosive areas.
Type of protection intrinsic safety "i" (intrinsic safety)
In potentially explosive areas, electrical and electronic devices in the intrinsic safety type of protection (abbreviated to EEx-i until 12/2004, since then only Ex-i, English: intrinsic safety) are used for measurement and control technology tasks . In these devices, the current strength and the voltage are limited to values that do not allow the ignition of explosive fuel-air mixtures either by sparks or by heating. Intrinsic safety must be ensured in normal operation, e.g. B. when connecting and disconnecting components, as well as in the event of a malfunction, z. B. in the event of a wire break or a short circuit.
Intrinsic safety is achieved by the fact that only those sparks are allowed that do not cause an ignition of explosive mixtures. In the simplest case, this can be achieved by limiting the current and / or voltage using a resistor. Other solutions are the limitation of the voltage with Zener barriers or the use of electronic current limiting devices. This z. B. for the gas group IIC active powers of approx. 2 W can be implemented in the device. In contrast to these statically functioning solutions mentioned, modern systems evaluate dynamic parameters (rate of increase in current, voltage jump, etc.). Such solutions, such as B. the Pseudo Linear System (PLS), Dynamic Arc Recognition and Termination (DART) or Power-i sometimes achieve significantly higher active powers of well over 20 W.
Energy-limiting barriers as associated equipment are not usually located in the potentially explosive area themselves, but are considered safety devices in the sense of ATEX Directive 2014/34 / EU and are therefore subject to it.
In such circuits, energy storage devices such as B. Capacitors are only permitted within certain limits. This also applies to parasitic capacitances such as those that can arise from long cable lengths. The relevant device data sheet (Ex certificate) therefore also provides information about the maximum permissible cable length. The cables used must, if they are color-coded, have a light blue jacket as an identifier.
Intrinsic safety is important wherever ignitable mixtures of substances can occur, for example in the chemical and petrochemical industry or in engine measurement technology. The general requirements for electrical devices (equipment) that are used in potentially explosive areas are described in IEC / EN 60079-0. The specific requirements for the intrinsic safety type of protection are in the standards IEC / EN 60079-11 - Part 11: Device protection by intrinsic safety "i" and IEC / EN 60079-25 - Part 25 for specific requirements for the construction and testing of intrinsically safe electrical systems Are defined. For systems that contain intrinsically safe devices, the standard IEC / EN 60079-14 - Part 14: Project planning, selection and installation of electrical systems can be used.
The advantages of intrinsically safe devices are that there is no need for complex housing constructions, maintenance work can also be carried out during operation and, because of the low voltages and currents, it is safe to work, e.g. B. in troubleshooting, is possible.
Intrinsic safety is a secondary explosion protection .
Intrinsic safety was first included in the standards as an ignition protection type in 1965. However, category "i" was only introduced with EN 50020 in 1977.
Intrinsic safety of collector systems
In the case of solar collector systems , intrinsic safety means that no faults may occur under normal operating conditions. According to DIN 4757, overheating of the system and pump standstill are common modes of operation in which the safety valve must not respond.
HV intrinsic safety
According to DGUV information 200-005 (formerly BGI / GUV-I 8686), HV intrinsic safety is a safety concept for electric vehicles with a high-voltage system , in which technical measures provide the user with complete protection against accidental contact and arcing against the high-voltage electrical system is guaranteed.
Intrinsic safety and image processing
In industrial image processing , systems are designed to be intrinsically safe by declaring all parts that have passed through as bad parts when functions fail .
Normative documents
Harmonized standards
- IEC / EN 60079-0: Explosive atmospheres - Part 0: Equipment - General requirements
- IEC / EN 60079-11: Explosive atmospheres - Part 11: Equipment protection by intrinsic safety "i"
- IEC / EN 60079-25: Explosive atmospheres - Part 25: Intrinsically safe systems
- IEC 60079-39 / TS /: Explosive atmospheres - Part 39: Intrinsically Safe Systems with electronically controlled spark duration limitation (Draft)
- IEC / EN 60079-14 Explosive atmospheres - Part 14: Project planning, selection and construction of electrical systems
See also
Web links
Individual evidence
- ↑ Udo Gerlach, Thomas Uehlken: Energieversorgung al pls In: P&A March 2007, pp. 69–71 ( PDF; 447 kB ).
- ↑ Udo Gerlach, Ulrich Johannsmeyer: Intrinsically safe "Power-i" technology on the advance internationally , 2015, doi : 10.7795 / 610.20150112u .
- ↑ Directive 2014/34 / EU of the European Parliament and of the Council of February 26, 2014
- ↑ Wolf Dill, Helmut Schacke, Peter Völker: 40 years of explosion protection as reflected in the Ex magazine. (No longer available online.) R. Stahl, 2014, archived from the original on December 10, 2016 ; Retrieved December 9, 2016 .