Creating a protective system for a power network it is necessary to consider the following requirements regarding surge arresters:
- Surge arresters should guarantee protection from threats, to which the power supply system and devies connected to it can be subjected in this place.
- Arresters should be placed the way , so they provide surge suppresion to the values, required for the chosen categories of resistance.
- Arresters resistance to short circuits should be compared to the expected short circuit value, which may appear in the arrester's asssembly place.
- It is necessary to mind the required distances, according to the recommendations of the manufacturer between:
- arresters of different classes,
- arresters and protected devices.
- In case of problems with observation of distances, it is necessary to apply arresters of classes I/II, I/II/III or II/III with the low voltage protection level.
Applying the principles of choosing surge arresters, it is possible to create multi-stage protection schemes from lightning strikes and other overvoltages in power supply networks of the construction site.
Below you will see examples of schemes, limiting surges and impulse points in electrical networks of different construction sites.
6.1. Big construction object
Construction object requires application of lightning protection system, carrying out conditions of I protection level ( for example, banks, hospitals, computer centers, telecommunication objects).
The picked solutions should guarantee protection of the object and devices in case of lightninf current occurrence with the minimal value of up to 200 kA.
Typical devices of office applicanes will be used in the object: computer systems, telecommunication devices and systems, automation control systems, special-purpose hardware.
It is necessary to supress surges, which may appear on the clamps of the protected devices with levels lower than 1500 V and even lower than 1000 V.
We will study two main network systems TN-C-S and TN-S.
Система сети TN-C-S - TN-C-S network system
Главный РЩ – main switchboard
Тип ограничителей- arrester type
Этажный щит- switchboard on the floor
Устройство – device
Ограничитель класса I – Class I arrester
6.2. Typical construction site, equipped with external lightning protection system.
The construction object requires application of lightning protection system, carrying out conditions of III and IV protection level ( for example, residential houses, office objects).
The picked solutions should guarantee protection of the object and devices in case of lightning current occurrence with the maximal value of up to 100 kA.
Typical devices of office applicanes will be used in the object: computer systems, telecommunication devices and systems, automation control systems.
It is necessary to supress surges, which may appear on the clamps of the protected devices to the level lower than 1500 V.
We will study two main network systems TN-C-S and TN-S.
Connection scheme in TN-S system is analogous to the one given in Example 1. Below you will see a cheaper protection scheme, in which the devices of class I, that guarantee complete protection from lightning currents according to the requirements of lightning protection III, are used.
6.3. Single-family residential house, equipped with external lightning protection system.
The construction object requires application of lightning protection system, carrying out conditions of III and IV protection level.
Picking solutions, it is necessary to guarantee protection of the object and devices in case of lightning current occurrence with the maximal value of up to 100 kA.
Typical electrical and electronic devices of house applicanes will be used in the object: computer systems, telecommunication devices and systems, heating assembly with micro-processor control.
It is necessary to supress surges in TN-C-S system, which may appear on the clamps of the protected devices to the level lower than 1500 V.
6.4. Single-family residential house without external lightning protection system.
The construction object doesn't require application of lightning protection system. The only threat comes from surges of atmospheric origin or switching overvoltages from the network.
Typical electrical and electronic devices of house applicanes will be used in the object: computer systems, telecommunication devices and systems, heating assembly with micro-processor control.
It is necessary to supress surges in TN-C-S system, which may appear on the clamps of the protected devices to the level lower than 1500 V.
Ограничители класса I – Class I arresters
INNOVATION- more powerful element of class II
EnerPro C S 275V 65kA is a new element of surge protection by LEUTRON company, which succesfully meets the requirements of bump tests of class II (C).
Its high resistance to electric shocks certify about its perfect features - it is exclusive in this class of surge arresters: the rated discharge current achieves 30kA for a shock of 8/20 ms, and maximal current - up to 65 kA 8/20 ms. The device is also able to limit lightning current achieving values of 7 kA in 10/350 ms.
Such a high shock resistance was achieved thanks to the application of high-quality voltage-variable elements. That is why, the arrester can be undoubtedly used, where no arresters of type I(B) are required, but arresters of type II (C) with the standard rated resistance of 20 kA 8/20 ms ma be not sufficient. It mainly relates to the protection of buildings without lightning protection, powered by a cable line , as well as electric and electronic devices in the protection zone of lightning rods, in zone 0V.
6.5. Manufacturing plant
Фабрика- factory
Ограждение- guard
Диспетчерская-central control room
Здание № 1- Building # 1
Молниезащита- Lightning protection
Микропроцессор АПВ – microprocessor automatic re-closure
Подстанция низкого напряжения- Low voltage substation
Главный распр.щит- Main switchboard
Главный распр.щит постоянного тока – DC main switchboard
Локальный распред.щит- local switchboard
Нет молниезащиты – no lightning protection
6.6. High-rise office center
Высокий офисный объект без разделения на зоны грозовой защиты-high-rise office object without division to lightning protection zones
Кабельный ввод- cable input
локальная подстанция – local substation
щит котельной – boiler facility board
щит выделенной сети питания- dedication power supply network board
локальный щит-local board
щит серверной – equipment room board
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