Applying Surge Protection to LAN

SPD can only be effective if properly installed, and here are some basic guidelines. You may be disappointed that you cannot follow all the guidelines due to practical constraints such as having to re-wire your network. However, even partial protection of your system is much better than no protection at all.

First, even if the building has lightning protection or can ignore direct lightning strikes, if a LAN cable connects one building to another, handle it as follows.

LAN cables that pass between buildings should be laid close to the power distribution board that has the grounding for the building's power.

u Install SPDs for the network on the LAN near the distribution board in each building. The problem is the potential difference between the two buildings, so treat each building in the same way.

Ground the SPD to the distribution board with the shortest possible cable. The best way to do this is to install the SPD on a grounded sheet metal.

As long as there is no direct lightning strike to the building, installing only one SPD for LAN in a building can protect all LANs in the building.

What if you can't install LAN cables as described above due to practical or economical reasons? In this case, you can't apply an integrated SPD for LAN and power that can reliably protect the entire network. Therefore, you can sufficiently protect individual H/W, but the rest of the parts can't be protected much. I'm not saying that you shouldn't attach SPDs to every item on the network, but realistically, it's a good idea to attach SPDs to the most strategically important equipment, such as file servers or application servers. Figure 9 shows an explanation of this method.

Figure 9. How to protect individual items among LAN equipment

Why does this method not sufficiently protect the system? The reason is shown in Figure 10.

Figure 10. Inductive surges appearing in a partially protected LAN system.

When a surge enters the LAN, the SPD operates to protect the equipment on which it is installed. However, due to the layout of the line, the current pulse generates an inductive surge, which is enough to destroy the insulation of other equipment in the vicinity. At this time, the energy of this surge varies depending on the line impedance and the maximum current, and since this energy is much lower than the energy of the original surge, even if it is partially applied, the entire network receives great help.

This method can also be applied to networks between buildings. Select the most strategically important items among network equipment and install SPDs on those items.

8. SPD for LAN protection

Here is how to select our SPDs to protect your network. This is a simple guideline, so you should refer to the product description for details. Although we have not compared the SPDs with those offered by other companies, readers should keep in mind that the SPDs supplied by our company ( SurgeFree ) as well as other well-known companies are designed and manufactured to survive repeated large surges. The cheap LAN protection devices on the market may protect, but they cannot withstand even a moderate surge and will fail. This is economically wrong. The reason is that if the SPD fails, the network will stop functioning, and it will take a lot of effort and time to find and repair the fault.

Here are the main LAN types and their corresponding SPDs. It should be emphasized again that to properly protect a LAN from surges, SPDs must be installed on power lines, telephone lines, and data lines.

1) Newer, faster LAN

Some computer systems, such as real-time video, need to transmit a lot of data over the network, especially when image data is included. As traffic increases, network speed slows down. Therefore, a lot of work is being done to increase the capacity of the network. One of them is to increase the data transmission speed. Fast systems of 100 Mbps or more are being installed, and the data transmission speed of these systems is more than 10 times that of standard Ethernet. Several years ago, the Fiber Distributed Data Interface (FDDI), which supports communication distances of more than 1 km using optical cables, appeared, solving the problem of data transmission speed and making all systems reliable.

It was expected to be recommended, but it was frustrated because the H/W cost and installation cost were too high, and new systems using copper wires were developed.

There are several systems that are commonly used, including ATM, variants of 100Mbps Ethernet, and CDDI (the Copper version of FDDI). For UTP cable systems above 100Mbps, our HAKELNET is suitable. This model can protect standard 4-pair cables, including Category 5. HAKELNET 1.2RJ/RJ is a single unit that protects one cable, and HAKELNET 8.4RJ/RJ is a rack-mount unit that can protect 24 cables.

Other products that can be applied include HAKELTEL and PSK */100M 5cat, DTB */100M 5cat, etc.

2) Twisted pair Ethernet 10Base-T

u Data transfer speed: 10 Mbps

u Applicable cables: UTP, STP. Even if the cable is 4-pair, only 2-pair is used.

u Cable characteristic impedance: 100 ohm

u Connector: RJ45

The cables used here are relatively inexpensive and flexible. If you move a computer in an office, you can plug a new cable of a different length into a hub and reconnect it to the network without disturbing other new users. In a coaxial Ethernet system, the cable must be installed close to each computer. Therefore, if you change the office layout, you will have to re-install the cable, which is expensive. Also, if the coaxial trunk cable breaks, the network will lose its functionality.

Our HAKELNET is suitable for token ring networks.

References

Surge protection for Local Area Networks,

MTL Surge Technologies