Surge Protector Uc Value Selection - Click Spd Selection Guide To Get
Recently, a customer asked us if we have a surge protector that meets the system voltage of 1140V in the TT system. Although we recommended a surge protector with a Uc of 1000V, the customer thought that the selected Uc value was too small and advocated the use of a Uc value higher than 1140V. This article aims to resolve this concern and guide everyone on how to correctly select the Uc value of the surge protector.
1. Correct understanding of Uc First, we need to correctly understand the Uc of the surge protector. Uc stands for "maximum continuous working voltage", which means that the surge protector can work stably at this voltage without affecting its performance.
2. Uc required in the national standard document
According to Article 5.4.3 of the national standard document "GB 50343-2012 Technical Specifications for Lightning Protection of Building Electronic Information Systems", the minimum Uc value of the surge protector installed in the power system can be obtained
3. Calculation method of Uc First, according to the calculation method specified in the standard, two factors need to be considered to determine the minimum requirement for the Uc value: the grounding system and the phase voltage U0. Taking the customer system voltage of 1140V as an example, according to the formula of the TT system in the table, the phase voltage U0 = line voltage / √3 = 1140V / √3 = 658V, then Uc = 1.15 * 658 = 757V. Therefore, in the power system with a system voltage of 1140V, the Uc value of the surge protector should be at least greater than 757V.
4. Principles for selecting the Uc value Secondly, after calculating the minimum required Uc value, select a voltage greater than the calculated minimum Uc value from the preferred values of the AC effective or DC maximum continuous working voltage Uc in Article 5.5 of GB 18802.1-2011 Standard Specification for New Energy Requirements and Test Methods for Surge Protectors in Low Voltage Distribution Systems
The editor believes that an excessively large Uc value should not be blindly selected from the preferred values of Uc. Although the larger the Uc, the longer the service life of the surge protector may be, it is not necessarily the larger the better. A larger Uc value will directly increase the Up value of the surge protector, thereby reducing its protective effect on the back-end equipment. At the same time, a high Uc value will also lead to an increase in the price of the surge protector. Therefore, performance and cost should be reasonably considered when selecting the Uc value. Therefore, for a system voltage of 1140V, a surge protector with a Uc value of 1000V is recommended, taking into account its service life and cost.
Through rational selection of the Uc value of the surge protector, it can ensure that the surge protector plays the best role in the system and achieve effective power system protection.
