23-02-2010, 06:39 AM
send me details of above topic
23-02-2010, 06:39 AM
send me details of above topic
07-03-2010, 05:37 PM
07-03-2010, 05:37 PM
08-03-2010, 06:11 PM
OVERVOLTAGE PROTECTION DEVICES
Technologies involved: In the voltage switching category comes the Spark Gaps(SG) and Gas Discharge Tube(GDT) technology. In the Voltage limiting category comes the metal oxide varistor technology(MOV) and the siicon avalanche diode(SAD) technologies. 1)AIR TERMINATIONS To protect the volume from direct lightning strikes and to avoid uncontrolled strikes air termination are used . Air termination is comprised by air-termination rods and air-termination wires. The location of air terminations is usually defined by the ˜rolling sphere˜ method 2) BUILDING AND ROOM SHIELDS Extended metal components, like metal roofs and facades etc form an effective effective electromagnetic shield by their meshed interconnection are especially important for shielding magnetic fields. They are also important for creation of lightning protection zones. In principle, a steel reinforcement and the metal window and door frames can form an electromagnetic cage. 3)SHIELDS FOR CABLES IN BUILDINGS Cables shall be run near the equipotential bonding lines. These are parts of the steel construction, reinforced walls, cable supporting structures, cable trays or other electrically conductive parts which are connected to the equipotential bonding system at least at both ends. Pair-twisted signal cables are to be preferred. 4)EQUIPOTENTIAL BONDING Lightning protection equipotential bonding of a protected volume includes all incoming metal installations. In the case of extended telecommunication systems, a duly shaped lightning protection equipotential bonding bar installed at ground level inside the building also functions as an earth bus and is usually installed as an earth ring bus inside the building. The earth ring bus, a ring equipotential bonding bar, is a copper bar having a minimum cross section of 50mm2 for surface mounting. 5)ARRESTERS surge protection devices are classified as: lightning current arresters and surge arresters.Lightning current arresters must be able to discharge lightning currents or considerable parts of them non-destructively. Surge arresters only serve limiting overvoltages at relatively low-energy surge currents. 6)Instrument Solutions Remote instruments and analyzers: The most susceptible instruments in a typical process facility tend to fall into one of three general categories “ analyzers, remote mounted instrumentation, and load/weight cells which employ highly sensitive microprocessors, ICs, or strain gage sensors and are often mounted on tall/isolated structures or the upper decks of process plants. DCS or PLC control system:: This is where the control element, the brains of the system, resides. The DCS/PLC manufacturers offer only minimal surge protection devices. The common element to both ends of the system is the signal and power wiring. These are the metallic power and information highways previously discussed. Once the surge couples onto this highway, at typically up to 7,500 Volts/15 Amperes for switching transients and up to 100 Million Volts/300,000 Amperes for a near lightning, it travels at 2/3 the speed of light in both directions on the conductor seeking low resistance pathways to ground.the most effective defense is a combination of Automatic Isolation systems, normal mode Surge Protection Devices installed at both ends of the loop and on every metallic conductor associated with the system, and a true low-impedance grounding system. MODERN SPARK GAP TECHNOLOGY FOR LIGHTNING AND SURGE PROTECTION The suge protection is normally based on Metal Oxide Varistor (MOV) tech- nology; sometimes combined with Gas Discharge Tubes (GDT) and/or Silicon Avalanche Diodes (SAD). SPARK GAPS IN RADAX-FLOW TECHNOLOGY AND WITH ENERGY FLOW CONTROL after the spark gap has been fired and the lightning cur- rent has been discharged to ground, the power supply is feeding the arc. Now, to interrupt the arc far before the zero cross- ing, it™s necessary to increase the arc voltage (counter voltage) to the level of the power supply. The internal insulation material used in the spark gap heats up after the arc is gener- ated, providing an internal gas flow which lengthens the arc and reduces the arc™s diameter which consequently increases the impedance and the voltage drop report: Modern-surge protection -Technologies.pdf (Size: 908.57 KB / Downloads: 207) Surge Protection Of modern electronic devices.pdf (Size: 368.08 KB / Downloads: 324) overvoltage protection devices.pdf (Size: 80.54 KB / Downloads: 146) check out this pdf too: www.eeel.nist.gov/817/pubs/spd.../files/Protect%20techniques.pdf For surge protection using superconductors, visit: https://seminarproject.net/Thread-surge-...ull-report
18-02-2012, 01:07 PM
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