The level of disturbance depends on the voltage variations (dv/dt) and the value of the coupling capacitance between the “disturber cable” and the “victim cable”. Line reactors are a simple and inexpensive way to increase the impedance of an isolated load source (as a variable frequency command, in the case of inverters). Figure 12 b – Example of capacitive coupling effect. One mislabeled or unlabeled wire could cause a great deal of confusion when you are rewiring the system. Shield loops must be grounded on a single point on the potential equalization conductor. Ground the shield on more than one point may be problematic. Always verify the shield continuity until the last PA segment in the segment, with due analysis of the connection and finishing, as it should not be grounded on the equipment housing. The purpose of grounding is to avoid occurring unsafe voltages on the classified area. This capacitor will work as an interference suppressor. checking the radio frequency shielding effectivity of an enclosure with an rf transmitter connected to enclosure surfaces and rf receiver to sense surface current at leakage points filed oct. 5, 1967 2 sheets-sheet 1 radio frequency transmitter fig. The grounded steel structure is enough to shield the buses and apparatus below it when there are no objects to protect above the substation’s top. A shielding device is disclosed for use in the under-vessel area from radiation emanating above the lower terminus of a control rod drive of a power generating nuclear reactor of the boiling water type. The level of disturbance depends on the current variations (di/dt) and the mutual coupling inductance. Radio frequency coupling is reduced by adequate grounding and shielding techniques. These standards vary according to the area and are being constantly updated. Reduce the “h” height and the cable length. Each of the system ground points is then connected to the tree ground bus with a single insulated conductor. Figure 2 shows a cross-section of this volume. This is very common in industries and factories, where EMI is fairly frequent in function of the larger use of machines such as welding instruments, motors (MCCs) and in digital networks and computers in the vicinity of these areas. Shielding must be connected to the ground or the structure compliant to ABNT NBR IEC 60079-14 standard. Figure 5 – Example of how important are grounding and equipotentialization and their influence on the signal. Do not be neglectful, imprudent, irresponsibly inexpert or incompetent on technical problems. To summarize, here is a list of their basic functions: The neutral conductor is normally insulated and the power source system must be the TN-S (T: directly grounded point; N: masses directly connected to the grounded power source point; S: different conductor for neutral and protection). For grounding, group circuits and equipment with similar noise characteristics in serial distribution and connect these points on a parallel reference and also ground ducts and boxes. All motors activated by inverters must be powered preferably by shielded cables grounded on both ends. The inductive coupling increases with: Figure 17 a – Inductive coupling between conductors, Figure 18 – Inductive coupling between cable and field, Figure 19 – Inductive coupling between cable and ground  loop, Cables with and without shield: 60Vdc ou 5Vac e < 400Vac, Cables with and without shield: 60Vdc ou 25Vac e< 400Vac. OSTI.GOV Journal Article: Shielding of the Final Focusing System in the Robust Point Design EMI (Electromagnetic Interference) is a process by which disruptive electromagnetic energy is transmitted from one electronic device to another via radiated or conducted paths, or both. Check if the inverters need common mode capacitors on the DC bus. Whenever possible locate the cable near the metal surface. Shielding of the Final Focusing System in the HIF Point Design* by Jeff Latkowski and Wayne Meier ARIES Projct Meeting January 8-9, 2003 *Work performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under Contract W-7405-Eng-48. Voltage lines with 0 Volts must be connected to ground and galvanically insulated from the fieldbus bus. Grounding and Shielding of Amplifier, Bridgesensor and Voltsensor Input Leads Noise can couple into low-level signals in a variety of ways. There was a points system, which ranked vulnerability from zero to three based on certain medication. 4 Classification System for “X” Designator Shielding Gases .....5. Inadequate shielding and bad grounding are often blamed when measurements are inaccurate, especially in high-impedance applications. The coexistence of equipment of different technologies and the inadequacy of the installations favors the emission of electro-magnetic energy and often causes problems of electro-magnetic compatibility. Some cables are constructed with double shielding, much more efficient for EMI protection. This type of grounding is not a zero-resistance type and its potential may vary. Grounding & Shielding Safety, system protection and performance are the three main reasons to earth a system. However, other operational problems may be caused by inefficient grounding: The grounding system must be single and must satisfy different purposes: The result is that equipment with metal housing is subject to noise on the power source and lightning grounding loops. This type of parallel grounding eliminates the common impedance problem, although detrimental to the use of a pile of wiring. Figure 14 shows the interference between cables whose capacitive coupling induces voltage transients, such as electrostatic pickups. Never connect a shielding on the common side of a logic circuit, as this will cause noise on the circuit. Ground connectors must be classified according to the maximum capacity of the inverter current. Figure 23 – Profibus-DP and the ground loops. The IEC 61158-2 recommends the complete insulation. Remember that each plant and system has its own safety details. The functional equipotentialization equalizes the grounding and guarantees that the signal circuits and the electromagnetic compatibility work well. The rolling sphere method applies equally to flat surfaces, sharp points, edges, and corners. An important concept is that the shielding system design assumes a strike current of magnitude I1. The resultant shielding might not protect the objects for strike currents I2 < I1 with a shorter striking distance, but will likely guard the items for strike currents I3 > I1 with a more considerable striking distance. If you don't have a login, click here to register In order to minimize the risk of potential problems related to safety, comply with the safety standards and those of the local classified areas regulating the equipment installation and operation. Consequently, the voltage reference becomes unstable and the noise appears on the signals. Keep each group conductor on the same package. The coexistence of equipment of different technologies and the inadequacy of the installations favors the emission of electro-magnetic energy and often causes problems of electro-magnetic compatibility. This article provides information and tips on grounding but in case of doubt the local regulations always prevail. In addition, this discontinuity may help ease the difference of potential between each duct segment, and, in the event of current surge generated by an atmosphere discharge or a short circuit, the lack of continuity will not allow the current to circulate along the aluminum duct and consequently will not protect the Profibus cable. Capacitive coupling (interaction of electric fields between conductors); Inductive coupling (accompanied by a magnetic field. MILLIONS more Brits will be plunged into Tier 3 from Saturday, Matt Hancock revealed today. EMI is the energy that causes undesirable response to any equipment and may be generated by sparking on the motor brushes, tension circuits switching, activation of inductive and resistive loads, activation of switches, circuit breakers, fluorescent bulbs, heaters, automotive ignitions, atmospheric discharges an… eur-lex.europa.eu. Whenever possible, refer to the EN50170 for the physical regulations and safetry practices of each area. Forgot your password? H. Issard, in Safe and Secure Transport and Storage of Radioactive Materials, 2015. When there are multiple segments keep them connected, ensuring the same reference potential, according to figure 26. In high frequencies these effects are absorbed by the cable shield. Scope This specification prescribes requirements for the ... termine the purity and dew point of the shielding gas. The structures located within the protective zone are significantly safe from lightning strikes. In this method, a sphere is rolled over the protecting structure, and the areas which the sphere cannot touch are within the protective zone. César Cassiolato In these cases, the use of metal ducts is recommended. When referring to shield and grounding, in practice there are other ways of handling this subject, one with much controversy, as for example, the shield grounding can be made in each station with the sub D 9-pin connector (figure 34), where the connector housing  makes contact with the shield and is grounded when connecting with the station. One of the main goals of a project is to keep all common signal return points on the same potential. When having TE and PE terminals, ground them separately at the closest panel point using a twisted loop. Another additional manner is to ground the equipment junction boxes and housings on a ground equipotential line on the non-safe side. The rolling sphere method allows us to determine the protective cone and the equivalent protective angle of a mast or rod. Cuprotect also provides a number of wireless shielding systems for wireless routers and access points. Never install a device that has been previously used without an intrinsically safe barrier on an intrinsically safe system, as the protection zener may be burned and will not work in instrinsically safe areas. It typically functions as the Faraday cage and protects against lightning. In this instance, the shield is insulated on all grounds, with exception to the negative ground point of the power source or the intrinsic safety barrier on the safe side. Control electromagnetic interference, both internal (capacitive, inductive and common impedance coupling) and external to the system (environmental); Operational safety, with the equipment housings connected to the earth, when any signal directly or indirectly grounded or referenced to the housing or the panel  is automatically referenced to the power source grounding; Protection against lightning, when the descending conductor of the Atmospheric Discharges Protection System must be connected to the power source gronding, metal piping etc., while the “circuitry earth” remains connected to the “lightning rod earth” via the electrode structure or system. In case of discrepancies, the norms, standards, profiles, technical guides and manufacturer manuals will prevail. In this case, we say that there is a protective cone around the mast or rod. Shielding vs. Grounding Effect at Two Points. A non-technical dictionary defines the word as a point in contact with the ground, a common return in an electric circuit and a arbitrary point of zero voltage potential. Quite often the reliability of a control system is jeopardized by its poor installations. Normally higher than 300V. CONTRIBUTOR. This capacitance effect between two bodies with electric loads separated by a dielectric is called mutual capacitance effect. GPs demand clarity on 'trigger point' for return of COVID-19 shielding. The device may be comprised of a plurality of individually mountable shell-like housings which are joined in mating contiguous relation to surround the lower terminus of a control rod drive. It is extremely important that every person involved is aware and conscious and moreover committed with the plant operational reliability and personal safety. Choose toroid inverters or add toroids (common mode chokes) on the inverter output. The world environment and terrorist activities more than signals the need for EMP shielding for military and civilian applications. It is worth noting that this ground is too noisy and may present high impedance. Figure 6 shows a tall structure and a rolling sphere of radius S. All points touched by the sphere are unprotected, which shows us that the roof and sections of the walls require shielding. The country has moved back to a tiered system of local restrictions. Grounding and shielding are mandatory requirements to guarantee the integrity of a plant data. The shield must cover entirely the electric circuits through the connectors, couplings, splices and junction and distribution boxes. The equipment housings are grounded individually on the non-safe side. The capacitive coupling is represented by the interaction of electric fields between conductors. the grounding resistance value must not be too modified throughout time; the components must resist to thermal, thermo-mechanical and electronic conditions; the  components must be robust or mechanically protected to meet external influence conditions; avoid damages to electrodes and other metal parts from electrolysis. Any industrial environment has electric noises in sources, including AC power lines, radio signals, machines and stations etc. One neutron with energy of 1 Mev in steel travels an average distance of 4 cm between two collisions. Masters every challenge. The protection of a substation against direct lightning strikes consists of providing secure conducting paths to carry the lightning currents to the ground without damaging equipment and jeopardizing personnel. Make sure that all cables of different zones are routed in separated ducts. Figure 3 shows the JT-60 building shielded by the 2,000 mm thick ordinary concrete on the ceiling by the shielding materials composed on the ceiling of concrete pa-nels of 500 mm, polyethylene of 150 mm and the concrete of 150 mm thicknesses. An intrinsically safe circuit must float or be connected to the equipotantial system associated with the classified area on only one point. Inside the panel create distinct zones and even use separating plates that served as shield. CODING LANGUAGE AND COMPUTER. One of these methods is the rolling sphere. Figure 7 shows the same sphere with a lower structure. Shielding effectiveness is the ratio of impinging energy to the residual energy. Traduction de 'shielding' dans le dictionnaire anglais-français gratuit et beaucoup d'autres traductions françaises dans le dictionnaire bab.la. Figure 30 – Shield and Ground  Ideal Combination. Watch the cable insulation. Marketing, Quality, Project and Services Engineering Director Substation Shielding Methods for Lightning Strikes, lightning strikes to transmission lines or substations, ReliOn Fuel Cells Complete NEBS Level 3 Compliance Testing, Micropelt Introduces Thermoharvester-Driven Wireless Sensor Node, Increased Power Density and Performance with 3D Embedded Substrate Technologies, Developing Next Generation Energy Management: An Interview with Huw Davies of Trameto, Improving Efficiency with an Active Switch on an AC Bridge, Transformers (power, current, and potential), Auxiliary equipment (such as carrier-current capacitors). Marketing, Quality, Project and Services Engineering Director, © Copyright 2020 | NOVA SMAR S/A - All Rights Reserved, http://www.smar.com/brasil2/artigostecnicos/, http://www.electrical-installation.org/wiki/Coupling_mechanisms_and_counter-measures, http://www.procobre.org/pr/pdf/pdf_pr/03_aterrame.pdf, http://www.lpm.fee.unicamp.br/~carlos_reis/interferencias.pdf, http://penta.ufrgs.br/rc952/Cristina/utpatual.html, http://www.chasqueweb.ufrgs.br/~valner.brusamarello/eleinst/ufrgs5.pdf, http://www.vnovaes.com.br/attachments/058_Aterramento-Marin%20Paginado.pdf, http://www.mecatronicaatual.com.br/secoes/leitura/690. In classified areas, if the equalization potential between the safe and the hazardous areas is not possible, the shield must be connected directly to ground (Equipotential Bonding System) only at the hazardous area side. Most lightning currents go through the wires and grounding electrodes close to the impact point. Good layout practice in panels allows the noise current to float between the output and input ducts and stay out of the route of the communication signals and the controllers. Arrange the conductors in a way to minimize the inducted current between the sets and and balance them. Significant damages may be caused to active equipment when the ground potential difference between both ends goes beyond 1 V (rms). Setting the design strike current by considering what the system insulation can withstand ensures that the substation will be protected when impacted by strikes with the lower current. Figure 28 - Grounding effect vs two-point grounding. Differential Mode Common Mode Source Victim, Figure 13 – Differential mode and common mode – Capacitive coupling. The ideal is to incorporate an input inductor and a RFI/EMC filter to work as additional protection for the equipment and a as harmonic filter for the electric network, where the equipment is connected. Keep in mind that in high frequencies the cables work as a transmission system with crossed and confused lines, reflect and scatter energy from one circuit to another. Figure 16 – Capacitive coupling between conductors at a D distance. You have cover all the topics related with this important knowledge area of the Power Substations Design with the highest professional level proper of an experienced Electrical Engineer like you. Source removal is the most effective way but not always possible. The mesh provides multiple ways for the lightning current to flow to the ground. The minimum and maximum gauges depend on the nominal inverter current and the physical limitation of the terminal blocks. These provide protection to peak currents and offer a deviation path of low impedance for the ground point. The gas blender is another cost-effective point-of-supply system for high-pressure compressed-gas cylinders. The ground wires, masts, and rods must be connected to the substation’s grounding electrode and the overhead lines’ counterpoise system if any. There are situations where earthing wires may be separated, however with precautions. The neutral conductor works basically as a means of conducting system return currents. HEMP shielding and IEMI shielding, along with Faraday Cage considerations, are outlined in this informative blog from MAJR Products. Following is the use of metal ducts to minimize Foucault currents. The main function of the RFI input filter is to reduce the emissions conducted by readiofrequency to the principal lines of distribution and the ground. Figure 12 shows that, according to the rolling sphere method, lightning can strike the building with the mesh resting directly on the roof. Up to this point, the shielding methods discussed for gamma rays and neutrons are approximate, semi-empirical techniques, which rely largely for their effectiveness on experimentally derived parameters, or parameters derived from more rigorous theoretical methods. When an electromagnetic wave pass through a shield, absorption and reflection takes place. Use control cables with the lowest possible transference impedance values. Many different problems may be generated by EMI on electronic equipment as communication failures between devices of the same equipment network and/or computers, alarms produced without explanation, action on relays that do not follow logic, without being commanded, in addition to the burning of electronic components and circuits etc. Within each system, the individual subsystems are single-point grounded. Use isolated and shielded cables (4 paths) between the inverter and the motor and between the inverter power supply along the inverter. Figure 8 – Inadequate multipoint grounding, Figure 9 – Inadequate single-point grounding. Currently, the rolling sphere method is widely accepted. The ground wires of the incoming and outgoing overhead lines should terminate at the top of the substation’s steel structure — this might require steel columns extending above the main structure. The ground wires run over the substation so that all equipment lies in the protected zone. The required insulation level (except on one point) must be designed to stand 500 V at the insulation test according to standard 6.4.12 of IEC 60079-11. Figure 15 shows an example of protection against transients. Can we connect signal ground to chassis? Remember that the cable between the inverter and the motor presents impedance to the inverter output pulse (called surge impedance). Any shielding through which noise flows must not include the signal path. Whenever possible, use grounded separation plates. “signal ground” for more sensitive circuits; “noise ground” for commands (relays), high potency circuits (MCCs, for example). An extra caution should be taken against excessive termination. Up to a few kHz: the inductive reactance is neglectable and the current will circulate by the way of less resistance. The key to magnetic shielding is to reduce the loop area. Later on (around 1976), its use was broadened to include substations. Whenever possible, connect the cable boxes on the equipotential line system. Above kHz: the inductive reactance predominates and this will make the current circulate by the way of less inductance. Single-point ground bus system using a common bus. Do not bring the network cable close to the power source and output cables of the inverters, to avoid the common-mode current. The reduction effect by using twisted wires is efficient for cancelling the flow, called Rt (in dB): Rt = -20 log{(1/( 2nl +1 ))*[1+2nlsen(/nλ)]} dB . Likewise, Figure 3 shows a cross-section of the protective zone for a mast or rod of height = y. Figure 33 presents wiring, shield and grounding details on multiple areas. For applications of AC variable frequency inverters that must comply with EMC standards use the same type as the shielded cable specified for the AC motors to be used between the inverter and the transformer. Typical Value Employed for Protective Ratio and Angle. For those on the Scottish shielding list, the new Scottish tier system includes new guidance. Leaders, the protective angle and protective zone concept is that the signal cables assumes strike! Drained by the same potential, Quality, project and Services engineering SMAR. Distinct zones and even use separating plates that served as shield absorption and reflection takes place,... The EN50170 for the shield should be physically separated ( > 30cm ) often does not occur simultaneously cesarcass! Product or system is more than one point may be described as an interaction between particles and matter collisions! The intended article wrap the conductor should be sufficient to cover the entire substation, including apparatus. Make protection more accurate only one point separated duct or use box.... Described as an interaction between particles and matter through collisions and capture by atoms shields for. Rd-6® is designed to be in contact with the lowest level is and. Terms of wiring use the twisted pair of wires with 100 % of the frequencies, because they the. Conductors does not match that of the duct compliant to ABNT NBR 60079-14., in common and differential modes circuits through the adjacent return frequency the... Joints are made with the following wiring rules: path, which vulnerability... 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