Power supply lightning protection type selection knowledge

1. How to choose a suitable power supply arrester

In a region that chooses to protect different types of equipment, the following factors should be considered:

● Thunderstorm intensity Ng and probability of occurrence of maximum discharge current in this area P

●The protected equipment is resistant to impact levels

●The value of the protected equipment (should be based on the national economic level)

●The social importance of protected equipment

● Power supply arrester for determining different protection voltage UP and discharge current

2, the key parameters of the power supply arrester

●Maximum discharge current Imax:

The maximum discharge current that can withstand the 8/20μs wave shock arrester. It can be appropriately selected according to the local thunderstorm intensity Ng (or annual average thunderstorm day Td) and environmental factors.

●Maximum continuous withstand voltage Uc(rms):

It means that the arrester can work continuously at this voltage value without affecting its parameters as a lightning arrester. Uc is nonlinearly proportional to the protection voltage Up.

●Residual voltage Ur and protection voltage Up

Residual pressure Ur: refers to the residual pressure value at the rated discharge current In.

Protection voltage Up: The protection voltage Up is related to the Uc voltage and Ur. According to the characteristics of the zinc oxide varistor, when the Uc value of the selected varistor is high, the Up and Ur will increase accordingly, for example, the discharge current is 10kA. (8/20μs):

Uc=275VUr (10kA, 8/20μs) ≤1200V

Uc=385VUr (10kA, 8/20μs) ≤1600V

Uc=440VUr (10kA, 8/20μs) ≤ 1800V

3. Classification of power surge arresters

●Differentiated by discharge current

Withstand 10/350μs wave products: This waveform is a simulated direct lightning strike waveform with large waveform energy. Currently there are air gap type and varistor type products. Such as the EPR100 type of Yilong Company.

Tolerant to 8/20μs wave products: This waveform is an analog inductive lightning waveform and is currently used more. Common discharge current parameters are 100kA, 80kA, 65kA, 40kA, 20kA, etc., using zinc oxide varistor.

●Differentiated by protection

Single-chip: Users can freely combine according to the way of grid connection, and choose different types and types of arresters. Such as Yilong company EPP series products.

Combination type: For the convenience of user wiring, the supplier has composed a variety of modules according to different wiring systems.

Installation method: Commonly installed for 35mm rails, there are also some companies fixed for screws.

●Differentiated by shape structure

Modular: Users can freely combine according to the way of grid connection, and choose different numbers and types of arresters.

Box type: Put one or two sets of modular lightning arresters in a lightning protection box, which is suitable for the occasion where the Distribution Box or equipment cabinet space is insufficient.

â—‡ Single-level lightning protection box: A set of power lightning arresters of the same level module is installed in a lightning protection box.

â—‡ Multi-level lightning protection box: Two sets of modular lightning arresters are placed in a lightning protection box. In order to solve the two-level lightning protection in a limited space, by connecting the decoupling coil or installing the isolation transformer, both the amplification current and the residual voltage can be limited to 1kV or lower. Usually two single stages can be used. The lightning protection box has the same effect as a multi-level lightning protection box.