2 Days Training Programme on Protection of Electronics, Earthing, LV Electrical Safety & Lightning Protection Report
Workshop on EMI/EMC Control Techniques for Railway Signalling Installations held on 25 & 26 May, 2005 at IRISET/SC
With the induction of Electrical / Electronic Signalling Equipment and more recently Software Embedded Electronic Systems on Indian Railways, the need for EMI/EMC Control is required to be acknowledged and appreciated by Signal Engineers.
On the instructions of Adviser/ Signal, Railway Board vide letter No. 2013/Sig/IRISET dated 27/28.04.2015 and with coordination with RDSO/LKO, a two-day workshop on 'EMI/EMC Control Techniques for Railway Signalling Installations' had been organized on 25 & 26.05.2015 at IRISET / SC.
The eminent and renowned speakers from the industry Shri S.Gopa Kumar, MD, M/s OBO Bettermann India Pvt. Ltd., Chennai, Shri Rangaswamy Ganesan, MD, M/s LP Consultants International Pvt. Ltd and Shri K. V. Varadharajan, Director, M/s LP Consultants International Pvt. Ltd., Chennai were invited for the Workshop to deliver the presentation.
All Zonal Railways, Metro Railway, CORE, RDSO and Railway Board had been requested to delegate CSEs or senior officers to participate in the Workshop.
22 participants from various Zonal Railways which includes 10 CSEs, 1 CWM, 1 CSTE/W, 1 CSTE/Project, 5 Dy CSTEs, 2 Joint Directors/Signal, RDSO and ASTE, RDSO from all Zonal railways, except NFR and CORE, had attended the workshop.
Shri P. Venkata Ramana, Senior Professor/ Signal welcomed the participants from various railways and introduced the visiting speakers. He presented a brief regarding the purpose, relevance of EMI/EMC, day-day sessions and the topics.
Shri Satyender Kumar, Director addressed the participants and expressed his concern about influence of EMI/EMC in present day context as signalling has been graduated from mechanical to electro-mechanical, to electrical and to electronics. He emphasised that effects of EMI/EMC needs to be percolated to grass root level. There were instances where EI systems had been decommissioned in NCR, SECR and SCR on account of lack of understanding of EMI/EMC requirements such as proper shielding and proper earthing to the systems. He quoted an example where AZD Praha EI System used to fail frequently for lack of proper earthing at the station. He suggested that EMI filter is required for AFTCs to overcome such effects of RE area. He expressed that there is a mismatch between Lab setups and field installations and therefore, OEMs have to come down to work at field level. In Railway environment, noise has been generated by various agents such as 25KV traction, Diesel and Electrical Loco, Power Electronics, Switching transformers which are interfering with modern signalling systems such as AFTC, AXC, EI systems etc., He expressed that knowledge base should developed by RDSO and IRISET. He advised the participants that as EMI/EMC, which is an area of concern now for signalling engineers, they should learn by taking advantage of this opportunity by interacting positively and effectively so that the knowledge can be proliferated to people working down below.
Shri Mansukani, Director, RDSO informed that Railways does not have an EMI/EMC test setup at present. He mentioned that they are utilising the setup at ECIL, Hyderabad for studying EMI/EMC effects.
Shri Ganesan suggested that setting up of EMI/EMC laboratory may cost about Rs. 50C which is a meagre amount when compared the signal outlay for the S&T works. He suggested that a simple low cost Spectrum Analyzer, Antenna and RF Current Probes & Power Quality Meter would help giving demonstration of EMI/EMC characteristics and effects. He recommended to have and to follow the technical books on the subject
|Introduction to EMC||– Clayton Paul (John Wiley);|
|EMC Engineering||– Henry W (John Wiley);|
|EMC for Product Designers||– Tim Williams (Newens);|
|Introduction to EMC||– Clayton Paul (John Wiley);|
|IEEE STANDARD 1100-2005||– IEEE Recommended Practice for Powering & Grounding Electronic Equipment|
III TECHNICAL SESSIONS
The Workshop has been conducted for 2 days with two sessions on each day covered the following topics broadly:
- General Principles in Railway System : EMC Perspective
- EMI/EMC Standards : EC Directives
- Mitigation Techniques: Grounding, Bonding Cabling Filtering, Shielding
- Mitigation Techniques: Transient Protection
- Various Practices of Earthing
- Best Practices of Lightning protection as per 62305
- Best Practices of SPD as per IEC 62305
Subtopics covered: EMI/ EMC:Definition, Simple model of EMI - three elements of EMI situation, Classification of EMC - Emission and Susceptibility, External Sources of Disturbances, Coupling Channels and Modes, EMC Receptors Susceptibility, Radiation, Common mode & Differential Mode modeling, Electrical Parameters - Wavelength, Frequency, Rise/Fall time, EM noise - internal and external, Sources of Emissions, EMC Management in Railways, EMC EC Directives, EMC Standards, Regulations.
Mitigation Measures:- (1) Safety Grounding, Signal Grounding, Equipment & System Grounding, Ground Loop Problems, Eliminating Ground Loops, Cable - EM/E/H field Coupling, Shielded Cable Grounding Technique, Cable - Characteristics, Layout, Termination (2) Filtering - EMI Filter Topology & Characteristics, Powerline Filter (3) High RF Immunity by Shielding- Magnetic/EM fields, Effectiveness of Shielding, Enclosure Design (4) Transients - Origin, Effects on Devices, SPD Classification & Characteristics, Application of SPD
Lightning Protection:IEC Standards, Lightning Protection System (LPS), Class of LPS, Risk Analysis and Management, Design of LPS; External LPS - Air Termination, Protective Angle, Rolling Sphere, Mesh, Down Conductor, Earth Termination System, Dimensions & Materials; Internal LPS - Lightning Equipotential bonding, Design Examples
Surge Protection: Protection of LV Electrical & Electronic Systems - Protective Measures against Voltage Surges - Setting up of Protection Zones, Equipotential bonding, Shielding measures, Arrestors at Zone Interfaces, Selection of Surge Arresters, Required Design Impulse Voltage for Equipment (IEC 60364-4-443/1995), Main Equipotential bonding for Lightning System, Connecting Equipotential bondings, Arrestor Technologies, Structures to be protected, Installation Guidance/TN-C-S, TT, TN-S Networks, Connecting Wires and Examples, Combined Arresters, Surge Protection Concept, Application of SPD, EPB, Coupling of Systems, Voltage Surges in Cables, Coupling Impedance and Shielding, Surge Protection in Data & Communication networks, Choice of SPDs, Tips for Installation, Protection of CCTV Cameras
Shri R Ganesan, Shri Varadarajan and Shri Gopa kumar delivered the presentations on above topics.
In addition to above, Shri R.K.Jain, CSE, West Central Railway presented a paper on "Ground Shielding Lightning Protection Technique" which was developed and implemented successfully for mitigating the problem of ELDYNE DCs in the field.
Measurement of Soil Resistivity with Fluke Earth Meter had been organised. Assessment of required grid configuration for achieving desirable Earth Resistance with the help of software package had been done. Risk Assessment software based on IEC 62305-2, Ed 2, 2010 had been demonstrated which evolves the calculated risk for a given installation for lightning as against tolerable risk. Software considers various parameters Structures dimensions, attributes, protection, occupancy, environmental influences, human loss, loss of essential public services, economic losses. It takes into consideration no. of thunderstorm days as given in IS 2309 as per locality.
V POINTS TO PONDER
- Class A Lightning Protection devices based on Early Streamer Emission technology will not be of much utility and simple Franklin Rods will do the same job. However, such installation shall satisfy IS IEC 62305 standards.
- 1-Ohm resistance is not practicable to achieve at many stations. As such it is clarified by the speaker that no standard stresses for such resistance value. It is only mentioned in the standards that the intrinsic value of the connecting conductor from the equipment to main earth bus bar has to be less than1 Ohm or less, but not the earth resistance itself. More ever, minimum value of earth resistance required is 10 OHMS for Lightning Protection.
- Initial structural designing of building to IEC 62305 LPMS will eliminate the necessity for ring earth or running separate down conductor for lightning protection. This needs to be implemented in all new constructions.
- Stainless steel is better than Copper, Galvanised Iron or Aluminium for connectivity as it gels well with other metals and does not form bi-metal contact. Aluminium can be used as Air termination and Down conductor for buildings which is economical. For usage inside earth / concrete, stainless steel or copper coated materials can be used. Proper Bimetallic connectors need to be used while connecting different material together
- Grounding is required from chip level to ship level. To make a proper earthing system it is better to do a survey and record the soil resistivity of places where major signalling installations are being done. The Soil resistivity values can be used as a base for designing proper earthing system.
- To ensure the EMI Emission and Immunity of railway equipments are satisfying the requirements, it is highly recommended to implement respective EMI/EMC testing standards for all electrical and electronic equipments working in Indian Railways.
- 'CE' marking on the equipment does not assure of its quality but it conveys that equipment is EM Compatible.