R&M RP categories – standardized PoE cabling

R&M RP categories – standardized PoE cabling

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Welcome, ladies and gentlemen. Delivering remote power over data cabling, what we call Power over Ethernet (PoE) today has become the most important technology development in LAN in recent years. It allows Ethernet or IP to reach out into new application fields previously reserved for other technologies. The standardization bodies recognize the importance of PoE with the creation of new remote power categories for the LAN cabling. These new RP categories require additional efforts from installers and planners to show conformance with generic cabling standards.

I'm Mathias Gerber, Market Manager at R&M for LAN cabling. The power of PoE increased over the past 20 years from humble beginnings at 13 watts up to a remarkable 90 watts nowadays with the latest standards. When initially with PoE we used one pair to feed power into a device and another pair to return to power to the power source. We have with PoE Plus, Type two PoE, which increased the individual current per pair. With PoE Plus we are now at 600 mA per pair.

In the new 4pair PoE applications however, we use all four pairs of the of the cabling in order to transmit the power. So, two pairs are used to feed power into the device, the other two pairs to return it. And obviously, if we just use double the number of pairs to feed power, we can increase the overall power, or double the overall power, just by adding two extra pairs. In Type 4 however, we have increased the power again up to 1 Ampere per pair and this is quite the significant amount for data cabling. Now, not only the amount of power increased over time, also the usage conditions of applications changed a bit.

When we had in the early days mostly devices that may use some increased power now and then, like a camera that may use the extra power to zoom in or move around, but the overall average of the power was quite low. We now see applications emerging that would need the maximum power that's allowed over the whole time, so 24/7. For example, intelligent lights with PoE control would use the complete 90 watts all the time and that is an additional change of conditions for the cabling.

This slide shows the overview on PoE requirements. The PoE wheel that we have here is actually showing the major components that we have to control to ensure 4PPoE. On the one side, we have the temperature increase in the installation cable that we have to control, in order to get attenuation of the whole link into control. Because hotter cables have more attenuation. The second part, we have to control is un-mating under load: spark erosion that occurs, if we unplug a connection while under load.

Here, we have to make sure that the damage that's caused by the spark is not affecting the quality of the connection between plug and jack. And finally, we have to make sure that the wire termination has a reliable long-term contact resistance, which is low enough not to heat up in PoE. We at R&M actually created this Power Safe logo to indicate products that using the much more reliable IDC contacts, which will give you a low resistance contact for many, many years to come. Now, introducing the remote power categories: the installation standards ISO/IEC 14763-2 and EN 50174-2 specify new RP categories and define that these categories have to be use in order to comply to the standards.

An RP category in essence defines the average current that's allowed in a bundle of cables. We have 3 RP-categories, one, two and three, and the RP1 allows currents up to 212 mA in the bundle, where the RP3 is allowing up to 500 mA overall. For all applications, the maximum power is defined as 500 mA per wire. Here we have to keep in mind, that we talked before on slide 2 about the current per pair.

Here we are talking about current per wire, so obviously one wire is one halve of a pair. And 500 mA here for RP3 is the same as the 1 A that we have for 4PPoE. The way the RP1 was defined at 212 mA is actually the level of current that is considered to be allowed to without having any impact on the cabling.

So, up to 212 mA in average in the bundle is considered not to increase temperature to an extent, that you would have to calculate with it and to consider it in the overall planning. The RP3 on the other hand is obviously the maximum value that the Type 4 PoE is allowing and generating and an RP3 installation is obviously then allowing all cables in a bundle to be powered with Type 4 PoE. If you look at the implications of that here, we see that in the RP1 you don't have anything to do in the planning stage. So basically, every cable conforming to standard is a RP1 cable.

However, later on in operations you would have to maintain and document the amount of applications that you put into a bundle. So you have to make sure every time before you plug in a device, that your average power is still below 212 mA. On the other hand, with a RP3, you have to make the planning in such a way that your installation is allowing to attach Type 4 PoE on every cable. But on the other hand, during operation of the installation, you don't have to do anything anymore because it's already planned for the worst case. Overall, the RP-category is a new dimension of characterization for the cabling. In this way it is similar to transmission performance classes or to fire certification, but it is independent of it.

So it is completely separate from this other 2 dimensions, that we have on here. Meaning, it is a new thing and you can have every combination of RP-categories with existing performance classes. Now how we do we implement the RP categories. RP categories have to be used. So, there is no choice in here. The generic cabling standards require you to follow the installation standard.

So, you see that here in this conformance statement in one of the standards: you have to follow the installation standards. And in the installation standards, the RP-categories are defined. So, there is no choice, you have to follow it. One of the most obvious things that you have to do, apart from just declaring what category you are, you have to attach labels to the spaces, where you can attach a PoE switch or a power source into the cabling.

Meaning, in your floor distributor you would have to add labels indicating what RP-category your cabling is. And if it's RP1 or RP2, you also have to add a qualifier that you are not allowed to add PoE equipment in addition, to what you have in there, without calculating first, that your average power is still below the level that you have agreed to. On the RP3, on the other side, obviously you just have to mention that it is RP3, because you can attach every kind of device that you want without any further documentation or administration. The standards themselves behave a little bit different from each other.

The EN 50173 requires you to have to specify what kind of RP-category you have, but it's not making any mandates for a certain category. It recommends using RP3, but you can choose to have RP1 a well. On the other side, if you go for ISO/IEC 11801 is actually require you to go for our RP3. And if you're not going to that, you're not according to 11801 anymore. This table here, actually shows the interrelationship between the PoE types and the RP-categories.

We have on the top here the different types showing the different classes of PoE, which represent the different power levels that you can transmit in PoE. What we see in here for example, for Type 2, a PoE Plus, is that the individual current per wire is 300 mA, which equals to 600 mA per pair. So, we have 300 mA, but we are only using two pairs out of four in the cable. So, if we are averaging out the current to all pairs, we would end up with 212, which is exactly the value that RP1 is giving you. RP1 is supporting PoE plus or Type 2 PoE on all cables, so that is the consequence. However, if we go to higher types of PoE, for example the Type 4 which we'll give you 500 mA per wire or 1 A per pair, we are already using all four pairs, hence the name 4PPoE.

So, the average in the cable is also 500 mA which is what RP3 would allow to be used. So, the RP3 is allowing you to use Type 4 PoE on all links of the installation. Now obviously, in a bundle you could have different applications and there are different ways how you can do that. And the standard allows and gives you ways how to calculate for it.

One way how you can do it is with this kind of table, where you have the relationship between, for example here a PoE Plus and the Type 4 PoE. On the horizontal axis you would have the number, the percentage of cables in the bundle with PoE Plus. For example, here with two thirds, 66% of the cables, being used for PoE Plus. And that would allow you to be still just within a RP1 environment. It would allow you to have about 7% of 4PPoE Type 4. So, that means the rest of the cables or 27% of the cables would be without PoE and you can't use that.

But that would still be an RP1 installation, even though you have 7% or 7 out of 100, of the cables used for Type 4 installation. So obviously that's one way to how you could work it out and there are probably installation where it would make sense to use this kind of calculation. However, typically it is not really practical. I think typically you would go for a RP3 installation and be done with it and make sure that you can attach whatever you want in the future. Because yes, you have to think about 20 years into the future on what applications you would have then. R&M actually updated the PoE calculator that we had for about ten years to the 3. generation calculator.

The Calculator is still using the same formulas in the background, but what we actually changed is the way on how you input data into the calculator. This was aligned with the terminology of the RP standardization, so that you can input your data directly with the terminology that you know from the standards. We also made it a little bit easier to simulate your installation in here, making more possibilities for the different segments, and also introducing the possibility to simulate your patch cord part of the channel. Overall, the PoE calculator gives you a way how you can manipulate and simulate your environment.

And because it is an automatic spreadsheet you can just do it easier and quicker. And one of the big benefits of the tool is, that you can document whatever you're planning was. And with that documentation you can prove to your customers or to a system provider that you did a planning and the what the parameters were. How we at R&M deal with the RP categorie is really that we introduced them into the RP Freenet warranty system.

So, from March 2022 onwards, we will have the RP categories in addition to the performance class as part of our warranty certificates. And we can do that because we would use the PoE calculator here in addition to the test data that we got anyway, if we go to a warranty system. And together we can actually check whether the installation as a whole performs to a certain RP category. So basically, what it means is you would have a Freenet certificate that is having the performance class and the RP category on it. RP1 is the default value. So, if you don't do anything with planning, you would end up with a RP1 installation.

But if you do a planning for RP3 and you submit this PoE calculator as documentation of your planning, we will upgrade this RP category here in the certificate from 1 to 3. Or to 2, if you choose to do so. R&M clearly recomments to upgrade to RP3 completely. I mean, this is necessary for ISO/IEC 11801 anyway and it's really the most practical thing to do, because probably RP1 is a fallback solution if you don't do anything to start with, you would just transfer responsibility to the operators later on. So, either you do nothing or if you do something then you upgrade to RP3 directly.

RP2 is kind of: you tried for RP3, but didn't quite manage to achieve it. So, it's kind of something in between. and not recommended here. That is what I wanted to show in the short video on RP categories. There is a lot of more information on the R&M website on PoE and a whole documentation with a white paper as a download from the website available.

Thank you very much for listening in, have a good day.

2022-03-03 21:24

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