SCADA,System,Grounding-,Factor technology SCADA System Grounding- 3 Factors You Really Must Consider

Active shredder safety technology for the small office. Shreds 15sheets per pass into 5/32" x 1-1/2" cross-cut particles (Security Level3). Patented SafeSense® Technology stops shredding when hands touch thepaper opening. Designated shredde The electronic cigarette is not new. People who buy electronic cigarette knows that this product has been in the market for years now. Despite some sectors apparently trying to shoot the product down from the shelves, the popularity of elect

Normal 0 false false false EN-CA X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable{mso-style-name:"Table Normal";mso-tstyle-rowband-size:0;mso-tstyle-colband-size:0;mso-style-noshow:yes;mso-style-priority:99;mso-style-qformat:yes;mso-style-parent:"";mso-padding-alt:0cm 5.4pt 0cm 5.4pt;mso-para-margin-top:0cm;mso-para-margin-right:0cm;mso-para-margin-bottom:10.0pt;mso-para-margin-left:0cm;line-height:115%;mso-pagination:widow-orphan;font-size:11.0pt;font-family:"Calibri","sans-serif";mso-ascii-font-family:Calibri;mso-ascii-theme-font:minor-latin;mso-hansi-font-family:Calibri;mso-hansi-theme-font:minor-latin;mso-fareast-language:EN-US;}The entire concept of lightning protection is to control anddirect the lightning surge energy so it does the least amount of harm ordamage.  When it comes to grounding SCADAsystems, there are a good many opinions on the matter, at least half of whichhave been influenced by apocryphal tales from the field.  For a typical SCADA application, there arethree main points to consider: (1) tower/mast height; (2) antenna type; (3)surge suppressor type. The principal intention of providing a common ground is tominimize any difference in electric potential between the antenna, tower,transmission cable, communications equipment and terra firma (ground).   Thesurge arrestor, which is intended to be installed at or very near the cablepoint-of-entry, is intended to reduce the potential harm to radio equipment fordc pulse electrical spikes (surges).  A cable ground kit, installed about midway between the top andthe bottom of a transmission line, utilizes the guy wire paths to ground, butis usually only considered for use on cable runs in excess of 150 feet. (Thisis based on a calculation of distribution of current on a guyed tower usingmesh current network analysis.)In-line surge arrestorWhen considering options for lightning protection, keep in mindthat lightning arrestors with dc continuity, such as simple gas tubes and ¼wave shorted stubs, may not be the best choice, no matter how attractive theprice may seem, since the gas tube arrestor would not turn on in time and the ¼wave stub would ‘share’ surge current with the equipment. The most effective type of lightning arrestor is “dc blocked”. That’sbecause there is no center conductor continuity from connector pin to pin. Theinternal coupling prevents the sharing of low-frequency surge current with theequipment.  It also allows the dc blockedgas tube type ‘impulse suppressor’ to fire as the voltage reaches the turn-onthreshold. When a surge arrestor successfully protects an individual sitefrom surge damage, the unit itself may be compromised, which is certainlybetter than having the radio equipment damaged. However, the link may very wellnot function thereafter, due to the nature of the protective device.  This situation may require that the surgedevice be replaced...a small price to pay when compared to the cost of theradio itself.DC ground antennaThere are a number of yagi antennas that utilize a folded dipoledesign for the active element. With this design, the center conductor isessentially grounded to the antenna frame.  If one checked resistance with an ohm meteracross the shield and center conductor, it would read as a dead short.  Ofcourse, to a radio it looks like a 50 ohm load!Electrically, it will shunt to ground. That attribute should benoted on the antenna data sheet, usually under the heading “lightningprotection”, as DC ground.  Thepath to ground is through the mounting structure, which, as a matter of course,should be electrically grounded.Cable ground kit-do we need it?“Weground the mast and use a name brandlightning arrestor.  Recently, the question of grounding the antennacables has come up.  Is that a practice that you recommend, and why or whynot?”   Many system integrators have been asked this question, and asyou can expect, few are undecided on the matter; they are often quite firm intheir beliefs, one way or the other. Only a few operators have elected to specify a cable groundingkit as part of the system ground. This typically involves cutting away a smallportion of the jacket in order to fix a ground lug directly to the braid. On towers that are less than 150 feet, this additional groundingtechnique adds only an incremental bit of transmission line ground.  For most SCADA applications, the end resultis not worth the additional time, equipment, and labour to install it. Empirical evidence suggests that the majority of SCADA users, particularlyin the Oil & Gas industry, findthat using a surge arrestor at one end of the transmission line and installing aDC ground antenna at the other has proven to be quite sufficient and cost-effective.   Be sure to err on the side of caution when dealing withgrounding issues.  Surge suppressormanufacturers are a very good resource, especially when the site is not asimple installation.Grounding of communications equipment can be quite complex andinvolved, particularly with high towers and/or multiple antenna systems.   For 98% of SCADA applications, the grounding methods outlinedabove are sufficient and safe. Good SCADA automation can become GREATusing optimum antenna technology incorporated into the design from the start.Visit us to learn more and see what great antenna options Wavelink AntennaSystems offers. Gary Tootle advises and supports wireless communications professionalsthroughout USA and Canada  contact Wavelink Antenna