Appendix
A.2 Protection against electromagnetic interference
Appendix A.2 Protection against electromagnetic interference
A.2.9 Outdoor routing of cables
Rules for EMC-compliant cable routing The same EMC-compliant rules apply both to indoor and outdoor routing of cables. The following also applies:
- Running cables on metal cable trays.
- Electrical connection of the joints of cable trays/ducts.
- Ground the cable carriers.
- If necessary, provide adequate equipotential bonding between connected devices.
- Take the necessary (internal and external) lightning protection and grounding measures in as far as they are applicable to your particular application.
Rules for lightning protection outside buildings Run your cables either:
- in metal conduits grounded at both ends, or
- in concrete cable ducts with continuous end-to-end armoring.
Overvoltage protection equipment An individual appraisal of the entire plant is necessary before any lightning protection measures are taken.
277
Appendix A.3 Lightning and surge voltage protection
A.3 Lightning and surge voltage protection
A.3.1 Overview
Introduction One of the most common causes of failure is overvoltage caused by:
- Atmospheric discharges
- Electrostatic discharges
- Switching overvoltages
The concepts or measures for protection from overvoltages is based on the lightning protection zone concept.
The rules to be complied with for the transitions between the individual lightning protection zones are presented here.
Note This section can only provide you with the general guide on protecting the S7-300 from overvoltage.
Complete protection from overvoltage is only guaranteed if the entire system design is based on the lightning protection zone concept. Comprehensive consideration must be given to this when planning construction of facilities.
We therefore recommend that you contact your Siemens representative or a company specialized in lightning and overvoltage protection if you require more detailed information about overvoltage.
From now on, we refer to the overvoltage protection device using the normative terminology, that is, according to the degree of hazard expected (pulse shape 8/20 µs or pulse shape 10/350 µs), divided into surge arresters for pulse shape 8/20 µs and lightning current arresters for pulse shape 10/350 µs.
Additional references The following information is based on the lightning protection zone concept described in the IEC standard 62305-4 - "Protection against LEMP".
278
Appendix A.3 Lightning and surge voltage protection
A.3.2 Lightning protection zone concept
Principle of the lightning protection zone concept according to IEC 62305-4, DIN EN 62305-4, VDE 0185-305-4
The principle behind the lightning protection zone concept is the division of the volume to be protected from overvoltages (e.g. a control room) into lightning protection zones based on EMC considerations (see figure A-2).
The various lightning protection zones (LPZ: Lightning Protection Zone) are delimited spatially as follows and not necessarily by physical boundaries, such as walls, floors, etc.
\begin{tabular}{|l|l|} \hline Lightning protection zones (LPZ: Lightning Protection Zone) & \ \hline Outside areas of a building with risk of a direct strike & Lightning protection zone LPZ 0_A \ \hline Outside areas of a building that are not at risk of a direct strike & Lightning protection zone LPZ 0_B \ \hline Inside areas of a building that follow lightning protection zone 0_B & Lightning protection zone LPZ 1 \ \hline Inside areas of a building that normally represent separate EMC-reducing rooms and are in lightning protection zone 1 & Lightning protection zone LPZ 2 \ \hline Electrical equipment (with shielding properties) in lightning protection zone 2 & Lightning protection zone LPZ 3 \ \hline \end{tabular}
Effects of the Lightning Strike
Direct lightning strikes occur in lightning protection zone 0_A. Effects of the lightning strike are high-energy lightning currents and strong electromagnetic fields. Effects must be reduced from one lightning protection zone to the next through suitable lightning current or surge arresters/shielding measures.
Overvoltage
Electromagnetic fields of the lightning channel can be reduced with appropriate shielding measures. Overvoltages due to inductions can be reduced to an non-dangerous level starting in lightning protection zone 0_B using surge arresters.
279
Appendix
A.3 Lightning and surge voltage protection
Diagram of the lightning protection zones
The following schematic diagram shows the implementation of the lightning protection zone concept for a building with outside lightning protection.
Figure A-2 Lightning protection zones of a building with outside lightning protection
Principle of interfaces between the lighting protection zones
Measures must be taken to reduce the peak current load and the magnetic fields at the interfaces between the lightning protection zones.
Each zone-penetrating metallic/electrical system must be incorporated into the equipotential bonding at the zone transition.
Note
Metal systems include ducts, structural parts, pipes (water, gas and heat), etc.
Electrical systems include power and IT cables and wires (e.g. line voltage, bus cable, ...).
Appendix A.3 Lightning and surge voltage protection
A.3.3 Rules for the interface between the lightning protection zones 0 and 1
Rules for the interface 0$_{A}$ to 1 (lightning protection equipotential bonding)
For lightning protection equipotential bonding at the interface of lightning protection zone 0$_{A}$ to 1, the following applies:
- Use of lightning current suppressors prevents introduction of lightning partial currents into buildings.
- Creation of a local equipotential bonding at the transition of lightning protection zones, with incorporation of metal supply systems (pipes, air ducts, cable ducts, cable channels etc.).
Components for the lightning protection equipotential bonding
Table A-7 Components for the lightning protection equipotential bonding
\begin{tabular}{|l|p{4cm}|p{5cm}|l|} \hline Seq. No. & Cables for ... & Connection at the interface 0${A}$ to 1 with: & Item number \ \hline 1 & 3-phase TN-C system & DEHNventil® DV M TNC 255 \newline DEHNventil® DV M TNC 255 FM * & 951 300 \newline 951 305 * \ \hline 2 & 3-phase TN-S system & DEHNventil® DV M TNS 255 \newline DEHNventil® DV M TNS 255 FM * & 951 400 \newline 951 405 * \ \hline 3 & 3-phase TT system & DEHNventil® DV M TT 255 \newline DEHNventil® DV M TT 255 FM * & 951 310 \newline 951 315 * \ \hline 4 & AC TN-S system & DEHNventil® DV M TN 255 \newline DEHNventil® DV M TN 255 FM * & 951 200 \newline 951 205 * \ \hline 5 & AC TT system & DEHNventil® DV M TT 2P 255 \newline DEHNventil® DV M TT 2P 255 FM * & 951 110 \newline 951 115 * \ \hline 6 & Supply U${N} = 24 VDC & BLITZDUCTOR® XT, basic unit BXT BAS \newline BLITZDUCTOR® XT, module BXT ML2 B 180 \newline (I_{L}$ = 1.2 A) (2-wire) & 920 300 \newline 920 211 \ \hline 7 & Supply U${N}$ = 24 VDC & DEHNbloc® M, DB M 1 150 \newline DEHNbloc® M, DB M 1 150 FM * \newline (2 ea. required) & 961 110 \newline 961 115 * \ \hline 8 & MPI bus cable, RS485, RS 232 (V.24) & BLITZDUCTOR® XT, basic unit BXT BAS \newline BLITZDUCTOR® XT, Module BXT ML2 B 180 \newline (2-wire) & 920 300 \newline 920 211 \ \hline 9 & Inputs/outputs of digital modules U${N} = 24 VDC & BLITZDUCTOR® XT, basic unit BXT BAS \newline BLITZDUCTOR® XT, Module BXT ML4 B 180 \newline (I_{L}$ = 1.2 A) (4-wire) & 920 300 \newline 920 310 \ \hline 10 & Inputs/outputs of digital modules U$_{N}$ = 230 VAC & DEHNbloc® M, DB M 1 255 \newline DEHNbloc® M, DB M 1 255 * \newline (2 ea. required) & 961 120 \newline 961 125 * \ \hline \end{tabular}
281
Appendix
A.3 Lightning and surge voltage protection
| Seq. No. | Cables for ... | Connection at the interface 0A to 1 with: | Item number |
|---|---|---|---|
| 11 | Inputs/outputs of analog modules (for example, 4-20 mA, 1-10 V) | BLITZDUCTOR® XT, basic unit BXT BASBLITZDUCTOR® XT, module BXT ML4 B 180(IL = 1.2 A) (4-wire) | 920 300920 310 |
- Version: With remote indication contact
Components of the series BLITZDUCTOR® XT can be remotely monitored with the appropriate accessories. Additional information under (http://www.dehn.de)
Direct order of components via:
DEHN+SÖHNE GMBH+CO.KG.
Hans-Dehn-Str. 1
D-92318 Neumarkt
Tel. +49 (0)9181-906-730
Rules for the interface 0B to 1 (strong electromagnetic coupling)
For overvoltage protection at the interface of lightning protection zone 0B to 1, the following applies:
- Use of power cables with peak current-capable cable shields (e.g., NYCWY) or twisted-pair IT cables (for example, A2Y(K)Y).
- Laying cables and lines
- In continuous, peak current-capable metal pipes that are grounded at both ends
- In reinforced concrete channels in which the reinforcement is grounded at both ends
- On closed metal cable racks that are grounded at the beginning and end
- Use of fiber-optic cables without a metal shield if such a transmission is intended
- Creation of a local equipotential bonding at the transition of lightning protection zones, with incorporation of metal supply systems (pipes, air ducts, cable ducts, cable channels etc.).
Additional measures
If the actions listed above cannot be performed, protection by means of surge arresters must be provided. The following table contains overvoltage suppressors that may be used to protect facilities.
Overvoltage protection of 24 VDC power supply
Always use the BLITZDUCTOR VT, type AD 24 V for the 24 VDC power supply of the S7-300. All other surge arresters do not meet the tolerance range (19.2 - 28.8 V) of the S7-300.
General information on use of surge arresters
If, taking into account the tolerance range, the voltages that occur in the system exceed the specified maximum limits of the surge arresters used, surge arresters of the next highest rated voltage series are to be used.
Components for the overvoltage protection
Table A-8 Components for the overvoltage protection
| Seq. No. | Cables for ... | Connection at the interface 0B to 1 with: | Item number |
|---|---|---|---|
| 1 | 3-phase TN-C system | DEHNguard® DG M TNC 275DEHNguard® DG M TNC 275 FM * | 952 300952 305 * |
| 2 | 3-phase TN-S system | DEHNguard® DG M TNS 275DEHNguard® DG M TNS 275 FM * | 952 400952 405 * |
| 3 | 3-phase TT system | DEHNguard® DG M TT 275DEHNguard® DG M TT 275 FM * | 952 310952 315 * |
| 4 | AC TN-S system | DEHNguard® DG M TN 275DEHNguard® DG M TN 275 FM * | 952 200952 205 * |
| 5 | AC TT system | DEHNguard® DG M TT 2P 275DEHNguard® DG M TT 2P 275 FM * | 952 110952 115 * |
| 6 | Supply UN = 24 VDC | BLITZDUCTOR® VT, BVT AD 24 | 918 402 |
| 7 | MPI/DP RS 485 bus cable | BLITZDUCTOR® XT, basic unit BXT BASBLITZDUCTOR® XT, Module BXT ML2 BD HFS 5 | 920 300920 271 |
| 8 | RS 232 (V.24) bus cable | BLITZDUCTOR® XT, basic unit BXT BASBLITZDUCTOR® XT, Module BXT ML2 BE S 12 | 920 300920 222 |
| 9 | Industrial Ethernet | DEHNpatch DPA M CLE RJ45B 48 | 929 121 |
| 10 | Inputs of digital modules UN = 24 VDC | DEHNconnect RK, DCO RK ME 24 (IL = 0.5 A) | 919 921 |
| 11 | Outputs of digital modules UN = 24 VDC | DEHNconnect RK, DCO RK D 5 24 (IL = 10.0 A) | 919 986 |
| 12 | Inputs/outputs of digital modules UN = 230 VAC | DEHNguard® DG S 275DEHNguard® DG S 275 FM *N-PE arrester in the TT systemDEHNgap C S, DGP C SDEHNgap C S, DGP C S FM * | 952 070952 090 *952 030952 035 * |
| 13 | Inputs/outputs of analog modules (e.g. 4-20 mA, 1-10 V) | DEHNconnect RK, DCO RK ME 24 (IL = 0.5 A) | 919 921 |
- Version: With remote indication contact
Components of the series BLITZDUCTOR® XT can be remotely monitored with the appropriate accessories. Additional information under (http://www.dehn.de)
Direct order of components via:
DEHN+SÖHNE GMBH+CO.KG.
Hans-Dehn-Str. 1
D-92318 Neumarkt
Tel. +49 (0)9181-906-730
283
Appendix A.3 Lightning and surge voltage protection
A.3.4 Rules for the interface between the lightning protection zones 1 and 2
Rules for the interface 1 to 2 (strong electromagnetic coupling)
For overvoltage protection at the interface 1 to 2, the following applies:
- Use of power cables with peak current-capable cable shields (e.g., NYCWY) or twisted-pair IT cables (for example, A2Y(K)Y).
- Laying cables and lines – In continuous, peak current-capable metal pipes that are grounded at both ends, or – In reinforced concrete channels in which the reinforcement is grounded at both ends, or – On closed metal cable racks that are grounded at the beginning and end
- Use of fiber-optic cables without a metal shield if such a transmission is intended
- Creation of a local equipotential bonding at the transition of lightning protection zones, with incorporation of metal supply systems (pipes, air ducts, cable ducts, cable channels etc.).
Additional measures
If the actions listed above cannot be performed, protection by means of surge arresters must be provided. The following table contains surge arresters that may be used to protect facilities.
Overvoltage protection of 24 VDC power supply
Always use the BLITZDUCTOR VT, type AD 24 V for the 24 VDC power supply of the S7-300. All other surge arrestors do not meet the tolerance range (19.2 - 28.8 V) of the S7-300.
General information on use of surge arresters
If, taking into account the tolerance range, the voltages that occur in the system exceed the specified maximum limits of the surge arresters used, surge arrestors of the next highest rated voltage series are to be used.
284
Components for the overvoltage protection
Table A-9 Components for the overvoltage protection
| Seq. no. | Cables for ... | Connection at the interface 1 to 2 with: | Item number |
|---|---|---|---|
| 1 | 3-phase TN-C system | DEHNguard® DG M TNC 275DEHNguard® DG M TNC 275 FM * | 952 300952 305 * |
| 2 | 3-phase TN-S system | DEHNguard® DG M TNS 275DEHNguard® DG M TNS 275 FM * | 952 400952 405 * |
| 3 | 3-phase TT system | DEHNguard® DG M TT 275DEHNguard® DG M TT 275 FM * | 952 310952 315 * |
| 4 | AC TN-S system | DEHNguard® DG M TN 275DEHNguard® DG M TN 275 FM * | 952 200952 205 * |
| 5 | AC TT system | DEHNguard® DG M TT 2P 275DEHNguard® DG M TT 2P 275 FM * | 952 110952 115 * |
| 6 | Supply UN = 24 VDC | BLITZDUCTOR® VT, BVT AD 24 | 918 402 |
| 7 | MPI/DP RS 485 bus cable | BLITZDUCTOR® XT, basic unit BXT BASBLITZDUCTOR® XT, Module BXT ML2 BD HFS 5 | 920 300920 271 |
| 8 | RS 232 (V.24) bus cable | BLITZDUCTOR® XT, basic unit BXT BASBLITZDUCTOR® XT, Module BXT ML2 BE S 12 | 920 300920 222 |
| 9 | Industrial Ethernet | DEHNpatch DPA M CLE RJ45B 48 | 929 121 |
| 10 | Inputs of digital modules UN = 24 VDC | DEHNconnect RK, DCO RK ME 24(IL = 0.5 A) | 919 921 |
| 11 | Outputs of digital modules UN = 24 VDC | DEHNconnect RK, DCO RK D 5 24(IL = 10.0 A) | 919 986 |
| 12 | Inputs/outputs of digital modules UN = 230 VAC | DEHNguard® DG S 275DEHNguard® DG S 275 FM *N-PE arrester in the TT systemDEHNgap DGP C SDEHNgap DGP C S FM * | 952 070952 090 *952 030952 035 * |
| 13 | Inputs/outputs of analog modules (e.g. 4-20 mA, 1-10 V) | DEHNconnect RK, DCO RK ME 24(IL = 0.5 A) | 919 921 |
- Version: With remote indication contact
Components of the series BLITZDUCTOR® XT can be remotely monitored with the appropriate accessories. Additional information under (http://www.dehn.de)
Direct order of components via:
DEHN+SÖHNE GMBH+CO.KG.
Hans-Dehn-Str. 1
D-92318 Neumarkt
Tel. +49 (0)9181-906-730
285
Appendix A.3 Lightning and surge voltage protection
A.3.5 Rules for the interface between the lightning protection zones 2 and 3
Rules for the interface 2 to 3 (electromagnetic coupling)
For overvoltage protection at the interface 2 to 3, the following applies:
- Use of power cables with peak current-capable cable shields (e.g., NYCWY) or twisted-pair IT cables (for example, A2Y(K)Y).
- Laying cables and lines – In continuous, peak current-capable metal pipes that are grounded at both ends, or – In reinforced concrete channels in which the reinforcement is grounded at both ends, or – On closed metal cable racks that are grounded at the beginning and end
- Use of fiber-optic cables without a metal shield if such a transmission is intended
- Creation of a local equipotential bonding at the transition of lightning protection zones, with incorporation of metal supply systems (pipes, air ducts, cable ducts, cable channels etc.).
Additional measures
If the actions listed above cannot be performed, protection by means of surge arresters must be provided. The following table contains surge arresters that may be used to protect facilities.
Overvoltage protection of 24 VDC power supply
Always use the BLITZDUCTOR VT, type AD 24 V for the 24 VDC power supply of the S7-300. All other surge arrestors do not meet the tolerance range (19.2 - 28.8 V) of the S7-300.
General information on the use of surge arresters
If, taking into account the tolerance range, the voltages that occur in the system exceed the specified maximum limits of the surge arresters used, surge arrestors of the next highest rated voltage series are to be used.
286
Components for the overvoltage protection
Table A-10 Components for the overvoltage protection
| Seq. no. | Cables for ... | Connection at the interface 2 to 3 with: | Item number |
|---|---|---|---|
| 1 | 3-phase TN-S, TT system | DEHNrail® DR M 4P 255DEHNrail® DR M 4P 255 FM *(IL = 25.0 A) | 953 400953 405 * |
| 2 | AC TN-S, TT system | DEHNrail® DR M 2P 255DEHNrail® DR M 2P 255 FM *(IL = 25.0 A) | 953 200953 205 * |
| 3 | Supply UN = 24 VDC | BLITZDUCTOR® VT, BVT AD 24 | 918 402 |
| 4 | MPI/DP RS 485 bus cable | BLITZDUCTOR® XT, basic unit BXT BASBLITZDUCTOR® XT, module BXT ML2 BD HFS 5 | 920 300920 271 |
| 5 | RS 232 (V.24) bus cable | BLITZDUCTOR® XT, basic unit BXT BASBLITZDUCTOR® XT, module BXT ML2 BE S 12 | 920 300920 222 |
| 6 | Industrial Ethernet | DEHNpatch DPA M CLE RJ45B 48 | 929 121 |
| 7 | Inputs of digital modules UN = 24 VDC | DEHNconnect RK, DCO RK ME 24(IL = 0.5 A) | 919 921 |
| 8 | Outputs of digital modules UN = 24 VDC | DEHNconnect RK, DCO RK D 5 24(IL = 10.0 A) | 919 986 |
| 9 | Inputs/outputs of digital modules UN = 230 VAC | DEHNguard® DG S 275DEHNguard® DG S 275 FM *N-PE arrester in the TT systemDEHNgap C S, DGP C SDEHNgap C S, DGP C S FM * | 952070952 090 *952 030952 035 * |
| 10 | Inputs/outputs of analog modules (e.g. 4-20 mA, 1-10 V) | DEHNconnect RK, DCO RK ME 24(IL = 0.5 A) | 919 921 |
- Version with remote indication contact
Components of the series BLITZDUCTOR® XT can be remotely monitored with the appropriate accessories. Additional information under (http://www.dehn.de)
Direct order of components via: DEHN+SÖHNE GMBH+CO.KG. Hans-Dehn-Str. 1 D-92318 Neumarkt Tel. +49 (0)9181-906-730
287
Appendix A.3 Lightning and surge voltage protection
A.3.6 Example: Surge protection circuit for networked S7-300 CPUs
The figure shows the required measures for the protection of two networked S7-300 against lightning strikes and overvoltage.
Figure A-3 Source: DEHN+Söhne
288
Components of the application example
The following table explains the components of the application example:
| Seq. no. | Component | Meaning |
|---|---|---|
| ① | Combination arrester 230/400 VAC supply, DEHNventil® DV M TNC 255Item no. 951 300DEHNventil® DV M TNC 255 FM *Part no. 951 305 *DEHNventil® DV M TNS 255Part no. 951 400DEHNventil® DV M TNS 255 FM *Part no. 951 405 * | Protection against indirect effects of lightning and overvoltages at zone transition 0A →1 and 0A → 2 |
| ② | Surge arrester, 230/400 VAC supply, DEHNguard® DG M TNC 275Item no. 952 300DEHNguard® DG M TNC 275 FM *Part no. 952 305 *DEHNguard® DG M TNS 275Part no. 952 400DEHNguard® DG M TNS 275 FM *Part No. 952 405 * | Protection against indirect effects of lightning and overvoltages at zone transition 1 -> 2 |
| ③ | Surge arrester, 230 VAC supply, DEHNrail DR M 2P 255Item no. 953 200DEHNrail DR M 2P 255 FM *Part no. 953 205 *(IL = 25.0 A) | Protection against indirect effects of lightning and overvoltages at zone transition 2 → 3 |
| ④ | Surge arrester, BLITZDUCTOR® VT, BVT AD 24, 24 VDC supplyItem no. 918 402 | Protection against indirect effects of lightning and overvoltages at zone transition 2 → 3 |
| ⑤ | Surge arrester, RS 485 interfaceBLITZDUCTOR® XT Basic unit BXT BAS,Part no. 920 300BLITZDUCTOR® XT Module BXT ML2 BD HFS 5,Part no. 920 271(2-wire) | Protection against indirect effects of lightning and overvoltages at zone transition 2 → 3 |
| ⑥ | Surge arrester, digital inputs of modulesDEHNconnect RK, DCO RK ME 24Part no. 919 921(IL = 0.5 A)(2-wire) | Protection against indirect effects of lightning and overvoltages at zone transition 2 → 3 |
| ⑦ | Surge arrester, digital outputs of modulesDEHNconnect RK, DCO RK D 5 24Part no. 919 986(IL = 10.0 A)(2-wire) | Protection against indirect effects of lightning and overvoltages at zone transition 2 → 3 |
289
Appendix A.3 Lightning and surge voltage protection
| Seq. no. | Component | Meaning |
|---|---|---|
| ⑧ | Surge arrester, inputs/outputs of the modules BLITZDUCTOR® XT Basic unit BXT BAS, Part no. 920 300 BLITZDUCTOR® XT, Module BXT ML2 B 180, Part no. 920 211 (IL = 1.2 A) (2-wire) | Protection against indirect effects of lightning and overvoltages at zone transition 0A → 1 |
| ⑨ | 2 EMC spring terminals for the basic unit of the BLITZDUCTOR® XT Part no. 920 395 | Direct or indirect shield grounding |
| ⑩ | Protective equipotential bonding line ≥ 6 mm² Cu | Protective equipotential bonding |
- Version: With remote indication contact Components of the series BLITZDUCTOR® XT can be remotely monitored with the appropriate accessories. Additional information under (http://www.dehn.de) Direct order of components via: DEHN+SÖHNE GMBH+CO.KG. Hans-Dehn-Str. 1 D-92318 Neumarkt Tel. +49 (0)9181-906-730
A.3.7 How to protect digital output modules against overvoltages caused by inductance
Inductive overvoltage
Overvoltage occurs, for example, when inductance is deactivated. Examples are relay coils and contactors.
Integrated surge arrester
S7-300 digital output modules are equipped with an integrated surge arrester.
Additional overvoltage protection
Inductive devices require additional surge arresters only in following cases:
- If these can be switched off by additional contacts (e.g. relay contacts).
- If the inductance cannot be controlled by SIMATIC modules, but the overvoltages that occur can nevertheless have a negative effect on SIMATIC.
Note: Request information on relevant surge protection rating from the supplier of inductive devices.
Appendix A.3 Lightning and surge voltage protection
Example: EMERGENCY-OFF relay contact in the output circuit
The figures illustrates an output circuit requiring additional overvoltage protectors.
Refer also to the rest of the information in this section.
Circuit for coils operated with DC voltage
The figure below shows DC-operated coils equipped with diodes or Zener diode circuits.
with diode with Zener diode
Diode/Zener diode circuits have the following characteristics:
- Switching overvoltages can be avoided. The Zener diode has a higher switch-off voltage capacity.
- High switch-off delay (6 to 9 times higher than without protective circuit). The Zener diode switches off faster than a diode circuit.
291
Appendix A.4 Functional safety of electronic control equipment
Circuit for coils operated with AC voltage
The figure shows coils operated with AC voltage and varistor or RC circuit.
Properties of a protective circuit with varistor:
- The amplitude of the opening surge is limited rather than attenuated.
- The surge rise-ratio remains the same.
- Short off-delay.
Properties of a protective circuit with RC elements:
- Amplitude and steepness of the opening surge are reduced.
- Short off-delay.
A.4 Functional safety of electronic control equipment
Reliability through basic measures
SIMATIC devices and components are extremely reliable thanks to extensive measures in development and production.
The basic measures include:
- Selection of high-quality components and strategic cooperation with high-performance suppliers
- Measures to prevent static discharge when handling MOS circuits
- Checks and monitoring of the production processes using statistical methods and visual inspections at various production stages
- Heat endurance run at higher ambient temperature as monitoring run-in
- Thorough computer-controlled final inspection and testing of all modules
- Statistical evaluation of all returned systems and components and analysis of service requests to enable the immediate initiation of suitable corrective measures
- Comprehensive computer-aided acquisition of the quality data in the production in order to ensure all the adopted measures
292
Appendix A.4 Functional safety of electronic control equipment
Increased safety measures In all cases where the occurrence of failures can result in material damage or injury to persons, special measures must be taken to enhance the safety of the entire installation. For these there exist special plant-specific regulations that also have to be taken into consideration by the owner-operator when structuring the control system. For electronic control equipment with a safety function, the measures that have to be taken to prevent or rectify faults are based on the risks involved in the installation. As of a certain degree of hazard the basic measures mentioned above are no longer sufficient. The owner-operator has to ensure that additional measures are realized for the plant, for example by using SIMATIC S7-F fail-safe control systems.
Important note The instructions in the operating manual must be followed exactly. Incorrect handling can render measures intended to prevent dangerous faults ineffective, or generate additional sources of danger.
Fail-safe systems in SIMATIC S7 Two fail-safe systems are available for the integration of the safety technology in the SIMATIC S7 automation systems:
- The fail-safe S7 Distributed Safety automation system – For the implementation of safety concepts in the field of machine and person protection, for example EMERGENCY-OFF facilities for the operation of machine tools/processing machines. – In the process industry, for example, for carrying out protection functions for instrumentation-and-control protective systems and burners.
- The fail-safe and optionally fault-tolerant S7 F/FH systems automation system for plants in process technology and the oil industry, for example.
Fail-safe and redundant system S7 F/FH systems To increase the availability of the automation system and thereby avoid process interruption in the case of errors, it is possible to build in fail-safe systems as optionally redundant S7 F/FH systems. The increased availability is achieved through the redundancy of the following components: Power supply, CPU module, communications and IO devices.
Attainable safety requirements S7 Distributed Safety F systems and S7 F/FH systems can meet the following safety requirements:
- Safety Integrity Level SIL1 to SIL3 to IEC 61508
- Categories 2 to 4 according to EN 954-1.
Reference You can find additional information in the Safety Engineering in SIMATIC S7 system description (A5E00109528-05).
293
Appendix A.4 Functional safety of electronic control equipment
294