Webinar «Surge protection of low-current lines, part 1», page 4

The 4th webinar about Surge Protection

Webinar text. Page 4

Quick slide navigation:

— Here we see an example of cable point protection. We have already shown it, I just want to remind you that this is a signal protection with a coaxial cable. Here are the BNC terminals and protection with power supply, since we installed this protection in zone 0B, we do not expect a partial lightning current to flow through our elements.

— In large objects, for example, at the customs point where there is a large number of cameras, we have to build large boards. Now the signal has changed to the signal standard, these are IP cameras, not BNC, a little different systems, but still there are some. Here we see the camera control protection, power protection.

— When we install such elements outside, we must remember that low-current systems do not withstand partial lightning currents. We must always install the elements of these systems in a zone protected from direct lightning strike. In this case there is this column that will take the lightning strike first. Then the camera will respond only to induced currents or grounding potentials. Here we install one protection circuit on two cables, as you saw in the previous figure. There always must be local grounding. We cannot allow surge current to flow through the yellow-green core for kilometers, because the surge on this inductance can be enormous.

— We see that every such device has installation manual. We just have to use our knowledge. Let’s suppose that our cabinet with overvoltage protection at the cable entry to the object is located near the outer wall in the basement under the ground. Then it is obvious that the cable to it will come from the top of the cabinet on this side. And the question is: where to install overvoltage protection? If we install it at the bottom of the cabinet, then all the energy form overvoltage will pass along the protected cabinet. Here the elements will limit it and send it back to earth with a ground conductor. And it is expensive to emit unnecessary energy to our cabinet. In this case you should simply install this SPD at the top. Then our energy will come to our protection and return the shortest way, without radiating over a large length of the protected device. If our cabinet is on the first floor and the cable comes to it from the bottom, then install SPD just at the bottom, the opposite to the way it was installed in the basement.

— As a result, we get different types of cabinets with video signal protection, control and power supply.

— We have already mentioned this, the issue of large objects, large geometric dimensions, for example, sports facilities, where the length of cables will always be large due to their size, and it reaches hundreds of meters, as, for example, in this case.

— Outriggers of the loudspeakers are there so that crowd could hear what the speaker is saying. Please, look, an SPD is installed here, and even for this case it is connected with a yellow-green wire. Here the tape goes around the stadium grounded to it. The shortest way is not 0.5 meters, it was not possible here, it is connected to the ground by the shortest way, where we divert the energy of the overvoltage. If we look at these points, see? I can see the speaker points and the camera points on the crown. It is clear that due to the large size, it is very likely for the lightning to strike the stadium. If it does, it is obvious that it will strike the highest points. And the highest points are our loudspeakers and our camera points.

Useful materials for designers:

• Webinars with leading industry experts
• Everything for calculations of grounding and lightning protection
• Useful materials: articles, recommendations, examples