PROFINET network qualification Peter Thomas - oct 2015

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Like its predecessor PROFIBUS, PROFINET is a diagnostic-rich protocol allowing your support team to quickly identify the source of device-related problems. This however is of limited use if the underlying performance of your network is poor. PROFINET networks are often seen as the plug and play solution for industrial networks, giving you the impression that successful completion of your application-specific testing is a guarantee that your network is working efficiently and without errors. This is fundamentally wrong and needs to be considered at the design stage as well as the acceptance stage of a project. This presentation will discuss the issues, how to address them and give typical examples of the equipment required.

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PROFINET network qualification Peter Thomas - oct 2015

  1. 1. PROFINET Network Qualification October 2015 Peter Thomas (Control Specialists Ltd) Chairman of the PROFINET & PROFIBUS International Training Centres (PITC‘s)
  2. 2. PROFINET - Overview 2 PROFINET is a member of a family providing industrial communications over Ethernet. PROFINET is: completely standard Ethernet (IEEE802.3). High speed, operating at 100Mbit/s or faster over copper or fibre-optic cables, makes use of existing IT standards. But, is “real-time” and deterministic, PROFINET is very well thought out to incorporate all the requirements of automation and control systems. PROFINET is totally compatible with PROFIBUS but is NOT PROFIBUS over Ethernet.
  3. 3. PROFINET – Flexible, Open and backward compatible 3 PROFINET
  4. 4. PROFIBUS v PROFINET 4 Feature PROFIBUS DP PROFINET Network size 126 devices max. Effectively unlimited Data Rate Up to 12M bit/s 100 Mbit/s Update rate and prioritisation All devices have same update rate and priority Different update rates and priorities Controlling Station Class 1 Master IO Controller IO Equipment Slave IO Device Diagnostic / Configuration Tool Class 2 Master IO Supervisor Protocols DPV1, DPV2, DPV3 PROFINET RT, ARP, DCP, SNMP, LLDP, TCP/IP, HTTP, MRP IT services Not possible Integrated in devices Real-Time Yes Yes
  5. 5. PROFIBUS v PROFINET 5 Feature PROFIBUS DP PROFINET Topology Typically linear bus but tree and ring possible Linear, star, tree and ring Redundancy Possible but manufacturer specific Simple and standardised Engineering access Changes possible but needs network restart Possible without disrupting operation Standard Diagnostics Yes Yes Alarms Only on DPV1 Yes, with priority Addressing By switch or over bus Over network Network Devices Repeaters, Hubs, OLM’s Switches Termination Switch-selectable Built into connector Cable 2 core shielded twisted pair 4 core shielded twisted pair
  6. 6. PROFINET – Real-time v TCP/P 6
  7. 7. PROFINET – In operation 7 PROFINET HTTP SNMP Socket IP TCP / UDP Sensor system PROFINET PLC PC SNMP/OPC server PROFINET Field devices PC Internet Explorer Real-Time RT IRT Ethernet PROFINET allows for different data rates for different applications within the same network.
  8. 8. PROFINET - Topology 8 PROFINET wiring is quite different to PROFIBUS PROFIBUS: Uses multi-drop segments with many devices on one cable. Segments are separated by repeaters. Two-core screened twisted pair cable. Termination is in the hands of the user – many problems arise because of this. PROFINET : Multi-drop connection is not used; all cables connect just two devices together. Switches are used for branching to devices. Four-core screened twisted pair cable. Termination is provided within every Ethernet device; no longer in the hands of the user – should eliminate termination problems.
  9. 9. PROFINET – Physical Layer 9 Ethernet defines the physical layer and data link layer. Modern Ethernet is defined by the IEEE802.3 standard. PROFINET uses 100Mbit/s switched full duplex communication over copper or fibre optic cable. 100 BASE-TX copper cabling 100BASE-FX fibre optic cabling
  10. 10. PROFINET – Physical Layer (Cable) 10 4-core shielded twisted pair cable. Link Class D - Cat5 or Cat5e cable for use at up to 100MBit/s. Characteristic impedance 100Ω. Cable length up to 100m maximum TD+ yellow TD- orange RD+ white RD- blue
  11. 11. PROFINET – Physical Layer (Connectors) 11 PROFINET connectors are available for: • “Inside use” – Within control rooms or cabinets – RJ45 pattern – Generally at least IP20 rated. • “Outside use” – Exposed to the environment (field mounted) – RJ45 pattern or – M12 – Generally IP 65 to 67 rated
  12. 12. PROFINET – IO Devices 12 Ethernet IO-Controller Configuration Control/monitoring Alarms DiagnosisDiagnosis Status/Control ParametersIO-Device PROFINET Supervisor E.g. PLC running application program. E.g. PC or laptop running engineering tool application. E.g. Field device with inputs/outputs (Compare with PROFIBUS Class-1 master) (Compare with PROFIBUS Class-2 master) (Compare with PROFIBUS Slave device)
  13. 13. PROFINET – Commissioning Guideline 13 • This is one of several free-to-download guidelines documents from PNO (PROFIBUS and PROFINET User Organisation). • It provides guidance on how to verify the installation aspects of the network as well as how to commission the live system. • These tests are additional to the application-specific, System Acceptance Testing that would usually be performed. Failure to follow these guidelines puts you at risk of having your application tests pass without a detailed knowledge of the underlying performance of your network !
  14. 14. PROFINET – Installation Acceptance 14 These are associated with the cabling of the installation and include: • Visual Checking of the cabling. • Point-to-Point electrical testing of the cabling using a simple line tester. • Point-to-point acceptance testing of the cabling using an Ethernet Function tester. Installation Acceptance tests should ideally be performed by individuals who have Certified PROFINET Installer accreditation. This is a one day course accredited by PI and delivered by organisations that have PI-certified Training Centre accreditation. There are two such organisations in the UK.
  15. 15. PROFINET – Installation Acceptance – Visual Checks 15 • The guideline lists 23 individual checks that should be performed on each cable. Examples are • Cable laid according to plan? • Maximum length of 100m observed? • Cable screen earthed at both ends to a previously proven earthing system. • Cable separation rules followed?
  16. 16. PROFINET – Installation Acceptance – Line Checks 16 The main criteria for the simple electrical testing of PROFINET cables are: • There are no short-circuits between any wires. • There are no short-circuits between any wire and the screen • There are no wire breaks. • The shield is connected at both ends. • The wire pairing has been observed correctly.
  17. 17. PROFINET – Installation Acceptance – Function Testing 17 • Simple line testers are designed to test the electrical aspects of the cable. • The more advanced function and acceptance testers establish the ability of that cable to successfully transmit predefined data packages as well as determine cable length, attenuation and cross-talk. • Such tests are very useful as a baseline in the event of needing to perform such tests at a later date.
  18. 18. PROFINET – Commissioning 18 These are associated with the operational aspects of the installation and should only be performed on completion of the Installation Acceptance tests. • Checking that the addressing and naming of all IO devices are in conformance with the design specification. • Determining other device-related information such as MAC addresses, Firmware versions etc. • Establishing that the topology is in conformance with the design specification. • Establishing the absence of discarded and error telegrams. • Establishing operational characteristics – IO Device Cycle time, Net load, Jitter, Broadcast. Installation Acceptance tests should ideally be performed by individuals who have Certified PROFINET Engineer accreditation. This is a three day course accredited by PI and delivered by organisations that have PI-certified Training Centre accreditation.
  19. 19. PROFINET – IO Device Identification 19 • Every PROFINET device has a world-wide unique MAC address assigned by the manufacturer. • The MAC address is unique to that particular device and will change if the device is replaced with a spare. • Before a device can take part in communications with an IO Controller, it must have been configured with a PROFINET Device Name. This is usually done with the configuration software of the IO Controller (e.g. Siemens TIA Portal) but can also be done using readily available PROFINET tools. • When the IO Controller initialises communication with the IO Device, it will allocate an IP address to it. • Every IO device will also have manufacturer-specific hardware and/or firmware versions. • Note - All real-time communications takes place using MAC addresses. MAC Address: 00: 0E:CF:04:68:7A Device Name: MySensorName123 IP Address: 192.168.1.23 HW Version: 1.0 FW Version: 1.24
  20. 20. PROFINET – Topology 20 Line Tree Star Ring PROFINET is very flexible when it comes to laying out the network. However, each of the four shown come with advantages and disadvantages that need to be considered at the design phase. It is important o ensure that the actual topology is in conformance with that described in the design specification.
  21. 21. PROFINET – Topology – Line Depth 21 • Line depth is the number of forwarding switches between an IO Controller and an IO Device. • The line depth will affect the cycle time that the device can be polled at. • The choice of switch (store & forward / cut-through) also affects this (see next slide).
  22. 22. PROFINET – Topology – Switching technology 22 STORE & FORWARD CUT-THROUGH
  23. 23. PROFINET – Test for “Discarded Packets” 23 • A switch may discard packets due to transmission problems or internal queue overflows at high network loads. • This should be evaluated over a period of 60s at high network loads. • During this period, there should be no discarded packets. Missing Packets at high Load
  24. 24. PROFINET – Test for “Net load” 24 • This is defined as the % of bandwidth used by the real-time communications. • It should be checked at every IO Controller. • The ideal value is <20%. • Values in the range 20% to 50% - further investigation required. • Values > 50% require actions to reduce the net load Testing for Net Load
  25. 25. PROFINET – Test for “Broadcasts and Multicasts” 25 • Occasionally, broadcast and multicast telegrams will appear on the network. • These are telegrams that all devices on the network will respond to. Typical examples include: • ARP broadcasts – Address Resolution Protocol telegrams are used during entire scans of the network and initiated by engineering systems, diagnostic tools and IT systems. Values > 0 and for entire IP ranges should be investigated. • DCP multicasts – Device & Configuration Protocol telegrams are generated by an IO Controller on start-up to search for devices with a given device name prior to allocating an IP address. Values > 10 are considered high should be investigated, those > 20 are considered too high for trouble-free operation. • MRP multicasts – Media Redundancy Protocol telegrams are used to determine data flow direction in ring topologies. Values > 0 should be investigated. Note – these values can be checked at any point on the network, including a spare port on a switch.
  26. 26. PROFINET – Test for “Jitter” 26 The organisation of PROFINET timing ensures that real-time communication with a particular device is achieved with a regular update time. However, it is possible that delays within switches and devices can cause the transmission time to vary from cycle to cycle. Such variable delays can give rise to “jitter”. Jitter is something that should be evaluated. Update time Time Jitter Jitter
  27. 27. PROFINET – EMC Criteria 27 • EMC (Electromagnetic Compatibility) and Protective Earth (PE) issues are acknowledged as being the cause of a significant number of problems on Fieldbuses and Industrial networks like PROFIBUS and PROFINET. • This is because of the ever-increasing frequencies that such systems operate at. • Simply ensuring that the cable screen is connected to earth at both ends serves no purpose if the earth loop impedance at “typical” frequencies is too high. • The screen impedance of all PROFINET cables should < 0.6 and the current >0mA AND < 40mA. • The impedance of the Functional Earth at “typical” frequencies should be <0.3 . • Any values outside of this range should be investigated.
  28. 28. PROFINET – Monitoring Tools - Operational Qualification 28 TO PROFINET NETWORK Internet Explorer This permanent monitoring solution can be used during qualification and on- going support. It has no effect on the PROFINET network which will continue to operate even if power to the monitor is removed. 24v Volt-Free Contact to PLC
  29. 29. PROFINET – Acceptance Specification 29 • This document acts as a formal record of the installation and operational qualification tests. • It should clearly define roles and responsibilities. • Define the type of tools required to perform the tests and typical specifications. • Each test should cross-reference back to the appropriate section in the relevant design specification. • Have clear descriptions of the tests and unambiguous acceptance criteria. • There should be space available for the tester to sign/date each test and make notes.
  30. 30. Peter Thomas (Control Specialists Ltd) Chairman of the PROFINET & PROFIBUS International Training Centres (PITC‘s) Peter Thomas Control Specialists Ltd PROFINET – Questions?

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