SCADA System Grounding – 3 Elements You Actually Should Take into account

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The whole idea of lightning safety is to manage and direct the lightning surge power so it does the least quantity of hurt or harm. In relation to grounding SCADA techniques, there are a great many opinions on the matter, not less than half of which have been influenced by apocryphal tales from the sphere. For a typical SCADA utility, there are three details to contemplate: (1) tower/mast peak; (2) antenna sort; (3) surge suppressor sort.

The principal intention of offering a typical floor is to reduce any distinction in electrical potential between the antenna, tower, transmission cable, communications gear and terra firma (floor). The surge arrestor, which is meant to be put in at or very close to the cable point-of-entry, is meant to scale back the potential hurt to radio gear for dc pulse electrical spikes (surges).

A cable floor equipment, put in about halfway between the highest and the underside of a transmission line, makes use of the man wire paths to floor, however is normally solely thought of to be used on cable runs in extra of 150 toes. (That is based mostly on a calculation of distribution of present on a guyed tower utilizing mesh present community evaluation.)

In-line surge arrestor When contemplating choices for lightning safety, take into account that lightning arrestors with dc continuity, corresponding to easy gasoline tubes and ¼ wave shorted stubs, is probably not your best option, irrespective of how enticing the worth could seem, because the gasoline tube arrestor wouldn’t activate in time and the ¼ wave stub would ‘share’ surge present with the gear.

The best sort of lightning arrestor is “dc blocked”. That is as a result of there isn’t any middle conductor continuity from connector pin to pin. The inner coupling prevents the sharing of low-frequency surge present with the gear. It additionally permits the dc blocked gasoline tube sort ‘impulse suppressor’ to fireside because the voltage reaches the turn-on threshold.

When a surge arrestor efficiently protects a person web site from surge harm, the unit itself could also be compromised, which is definitely higher than having the radio gear broken. Nevertheless, the hyperlink might very nicely not perform thereafter, because of the nature of the protecting system. This case might require that the surge system get replaced…a small worth to pay when in comparison with the price of the radio itself.

DC floor antenna There are a selection of yagi antennas that make the most of a folded dipole design for the lively aspect. With this design, the middle conductor is basically grounded to the antenna body. If one checked resistance with an ohm meter throughout the defend and middle conductor, it could learn as a lifeless brief. In fact, to a radio it seems to be like a 50 ohm load!

Electrically, it is going to shunt to floor. That attribute needs to be famous on the antenna knowledge sheet, normally below the heading “lightning protection”, as DC floor. The trail to floor is thru the mounting construction, which, as a matter after all, needs to be electrically grounded.

Cable floor kit-do we want it? “We ground the mast and use a name brand lightning arrestor. Recently, the question of grounding the antenna cables has come up. Is that a practice that you recommend, and why or why not?”

Many system integrators have been requested this query, and as you’ll be able to anticipate, few are undecided on the matter; they’re typically fairly agency of their beliefs, in some way.

Just a few operators have elected to specify a cable grounding equipment as a part of the system floor. This sometimes entails slicing away a small portion of the jacket as a way to repair a floor lug on to the braid.

On towers which can be lower than 150 toes, this extra grounding approach provides solely an incremental little bit of transmission line floor. For many SCADA purposes, the tip end result will not be well worth the further time, gear, and labour to put in it.

Empirical proof suggests that almost all of SCADA customers, notably within the Oil & Gasoline business, discover that utilizing a surge arrestor at one finish of the transmission line and putting in a DC floor antenna on the different has confirmed to be fairly adequate and cost-effective.

Remember to err on the aspect of warning when coping with grounding points. Surge suppressor producers are an excellent useful resource, particularly when the location will not be a easy set up.

Grounding of communications gear could be fairly advanced and concerned, notably with excessive towers and/or a number of antenna techniques.

For 98% of SCADA purposes, the grounding strategies outlined above are adequate and protected.

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BY by GAHZLY
El Sewedy wire costs 2022

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