Presentation. Lightning Protection practices in Bangladesh :An overview

Transcription

1 Presentation on Lightning Protection practices in Bangladesh :An overview Abidur Rahaman Dept. of Applied Physics and Electronics University of Dhaka, Bangladesh

2 Outline Lightning and lightning protection systems Current practices and measures in Bangladesh

3 Haunting Memoirs in Bangladesh

4 Haunting Memoirs in Bangladesh Lightning strikes kill 9 in Bangladesh (21 Mar 2008, Asia World News) Five killed by lightning (28 May 2007, DPA) 6 killed in lightning in Bangladesh's southern districts (08 August 2006, UNI) Lightning Kills 5 in Bangladesh (12 September 2006, The Indian Express) Lightning bolt killed nine and injured 23 in northeastern Bangladesh, 16 February people were killed and 40 people were injured at Chapainawabgonj, on the 12th July 2005.

5 LIGHTNING FACTS Globally 44,000 thunderstorms/day and 100 lightning strokes /sec Duration of one stroke of lightning, 1/5 th of second. Voltages 1,00,000 kv and peak current 30 ka. Total energy released 40 GJ. Temperatures rises 50,000 degrees Celsius Lightning strokes ranges from 100 m 8 km length. Lightning can travel at speeds of 60,000 m/sec Lightning heats nearby air to about 10,000 C.

6 Real captured image of lightning strike

7 Some examples of damage by Lightning and surge current The microscopic runs on a processor chip are extremely susceptible to surge related heat stress. The surges meets resistance, converts to heat and causes a blister on the run. Cumulative Catastrophic Installation in Bangladesh Surge Protective Device (SPD) As the repetitive surges continue to hit the spot over time, the blister grows until it effectively blocks the power or data flow on that circuit.

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9 World s Thunderstorm days per year Bangladesh has 80 to 120 days/year

10 Annual flash rate: NASA satellite report, Bangladesh has flash per square kilometer

11 WHAT IS LIGHTNING LIGHTNING is a SPARK Lightning a Gigantic Electrical Spark Traveling between Cloud to Cloud or Cloud to Earth Containing an average charge of 30 to 50 lakhs Volts and a current of 30 Kilo amperes with a speed of 220 km per hour.

12 A Complete LIGHTNING PROTECTION system Air Terminals Down Conductors Ground Terminals Interconnecting Conductors Surge Protective Devices, and Other Connectors or fittings required to complete the system.

13 Lightning Protection System Capturing system: Franklin rod system Meshed Conductor by Faraday cage Early Streamer Emission

14 FRANKLIN RODS Based on the Benjamin Franklin s (1752) original design which uses points effects. Charges around a conductor accumulate on the sharpest ends and easily overcome air resistance. Rp H The protected area is limited and depends directly on the height at which the point is placed and on the required protection level.

15 MESHED CONDUCTORS Commonly known as Faraday Cages In use since 1884 when Melsens proposed this practice for buildings protection. Fundamentals: inside a perfect continuous conductive cage there is no risk and no electrical field variation appears when an electrical current is flowing over its surface. In practice, this is possible with costly and most of the times unaesthetic arrangements.

16 EARLY STREAMER EMISSION AIR TERMINAL : ESE Bigger protection area (min 32 meter radius) Right moment trigerring (15-45 micro second) Easy installation Air terminal with a triggering device which ionizes the end point of the rod, controlling the generation. This control leads an early streamer emission before any Franklin rod does ( t) and in the right moment, achieving a bigger protection area. Rp 2 H Rp 1

17 LIGHTNING PROTECTION SYSTEM (LPS) ESE METHOD WITH SIMPLE AND COST EFFECTIVE INSTALLATION WORKS Installation in Bangladesh DAT CONTROLER PLUS ❶ Protecting very costly And sensitive equipment At the tower and beneath its control room from direct Lightning strike ❹ ❷ ❸

18 Lightning Protection: Implementation Franklin method Radius of influence : 3m Height of lightning rod: 1m Cost per 32 meter radius protected area: 3Million BDT Faraday case method Cost per 32 metre radius protected area: 5 million BDT ESE method Cost per 32 meter radius protected area: 0.3 Million BDT With imported ESE lightning rod

19 Continuous Effort in Bangladesh Bangladesh National Building Code (BNBC) first proposed in 1993 and legally binding in 2006 gives clear regulations for setting up Lightning Arrestor in buildings more than 33m high. Fire Service and Civil Defense department and Public Works Dept. (PWD) of Bangladesh government are working relentlessly in lightning awareness and protection in common people. It is obligatory to take the NOC (No Objection Certificate) for all realtors which comply with BNBC code. Border Guards Bangladesh (BGB) completed a survey on lightning and surge protection in September 2008 in the country s hilly southeast portion signaling sites and camps. Barapukuria coal mining company started for setting up modernized lightning protection device from 29 th September 2008

20 Continuous Effort in Bangladesh More than Base Station Subsystem (BSS) sites by six cellular operators all over the country. Two WiMAX operators & Radio-TV broadcast stations tower only increases this number. These are all structures built on plain fields or rooftops. The average height ranging of these tower are meters. All of these tower and high rise structures are more prone to get a lightning strike. As these sites are backed up by Batteries, IPS and auto start diesel driven generator, the probable occurrence of lightning and subsequent firing damage is a looming threat. In 2006, mobile operator Teletalk Bangladesh Ltd. completed setting up modern lightning protector to their 150 BTS. Their estimated budget for lightning protection is 110 million BDT. A Dhaka based organisation named TARA(Technological Assistance for Rural Advancement) working on lightning awareness program to mass people that achieved notable attention.

21 Preventive Measures For safety and protection the following measures are essential: Proper installation of ESE Type Lightning Protection System (LPS) Proper installation of Surge Protective Devices (SPD) Installation of Residual Current Circuit Breaker (RCCB) or Residual Current Device Installation of Miniature Circuit Breaker (MCB or MCCB) Very low resistance Grounding / Earthing as per international standard.

22 Thank You