Surge protection is of great importance in terms of securing electrical installations, but remember that its effectiveness depends on correct selection and installation. Mistakes made at this stage can be very serious, leading to serious failures, equipment damage, and even threats to people's safety. One of the problems is the lack of consideration of the level of exposure to lightning and surge hazards, which results in the incorrect selection of protective devices. Another drawback may be the inappropriate level of surges at the boundaries of protection zones, which significantly weakens the effectiveness of protection. Other errors also include the incorrect arrangement of arresters of different classes and the inappropriate length of cables used to connect them. It is these issues that we will deal with in this article.
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Failure to take into account the degree of exposure to lightning and surge hazards
As mentioned in the introduction, one of the most serious mistakes when selecting surge protection is an insufficient analysis of the level of lightning and surge hazards to which a given facility is exposed. This is because each building has different protection needs, which depend on various factors, such as location, height, and type of construction.
Weather conditions are also of no small importance here - the frequency of storms in a specific area. It is natural that tall buildings and facilities located in open spaces, especially away from other buildings, are more susceptible to lightning strikes. Therefore, they require higher classes of lightning protection.
Without this analysis, it is difficult to match surge arresters of the appropriate value and effectiveness. This may result in improper protection. Consequently, when strong lightning strikes or a sudden increase in voltage occurs, the installation and the devices connected to it are seriously exposed to damage. A properly matched surge arrester is therefore of great importance here.
Inappropriate level of overvoltage at the border of protected zones
Another very serious mistake when designing surge protection is the improper adjustment of the surge level at the transitions between the internal and external protection zones. The principle of protection grading requires the use of different classes of surge arresters - class B, C, D, in appropriate places. This is to protect equipment located in zones with different levels of risk.
For example, a Type 1 B surge arrester is installed at the beginning of the system, so its task is to protect the installation from the direct effects of a lightning strike. In the case of surge arresters of classes C and D, it is different. They are used deeper in the installation to effectively reduce smaller surges.
It is therefore extremely important to adhere to this principle, because omitting a class can lead to a dangerous situation when the surge energy is not suppressed, but passes to the next stages of the installation. This is a serious threat to devices and components. So let's remember that this is the protection of the entire system.
Incorrect placement of limiters of different classes
The issue of selecting the right surge arrester is also extremely important in other cases, especially if we incorrectly arrange arresters of different classes. This is a serious mistake that negatively affects the entire installation. As we mentioned in the previous paragraph - each arrester has a different task, which is why they must be where they belong. Otherwise, we can expect major problems with surges. Taking this into account, let's always remember to select a surge arrester according to their purpose.
Class B solutions must be placed at the main entrance to the building installation, which will protect the installation from direct lightning strikes. In this way, they neutralize the highest surges. The next ones - from class C, are placed closer to devices in intermediate zones. In this way, they protect against surges transmitted further in the installation. Class D arresters are dedicated to final protection, installed directly next to the most delicate devices, such as electronic equipment. Very often, they are generally referred to as DC surge arresters .
Inadequate length of cables used to connect surge arresters
An extremely significant drawback is also the improper length of the cables used to connect surge arresters. If it is bad, the arresters will not work effectively. Often, cables that are too long are used, which increases resistance and inductance while reducing the effectiveness of the arresters. Remember that the length should be as short as possible, which ensures faster discharge of surges to ground, thus minimizing the time of their impact on the installation.
The recommendations state that the total length of the connecting cables should not exceed several meters. Ideally, it should be as close as possible to the protected devices themselves, although it is known that in many cases this is difficult to achieve. Equally important, the cables should be routed in such a way as to enable direct connection to the arresters, where there is a minimum number of bends and twists. This limits the effects of inductance.
If these errors are eliminated, we can be sure that the surge protection will function properly without any dangerous symptoms.