Recently, a customer asked us if we have a surge protector with a system voltage of 1140V in the TT system. Although we recommended a surge protector with a UC of 1000V, the customer felt that the UC value was smaller and advocated a higher UC value than 1140V. The purpose of this article is to solve this doubt and guide you on how to correctly choose the UC value of a surge protector.
1. Correct understanding of UC
First of all, we need to properly understand the UC of the surge protector, UC stands for "Maximum Continuous Operating Voltage", which means that the surge protector can operate stably at this voltage without affecting its performance.
Second, the UC required in the national standard document
According to the national standard document "GB 50343-2012 Building Electronic Information System Lightning Protection Technical Specification" Article 54.3 can obtain the minimum UC value of the surge protector installed in the power system, and the specification details are as follows:
3. Calculation method of UC.
First of all, according to the calculation method specified in the standard, two factors need to be taken into account to determine the minimum requirements for the UC value: the grounding system and the phase voltage U0. Taking the customer's system voltage of 1140V as an example, calculated according to the formula of the TT system in the table, the phase voltage U0 = line voltage 3 = 1140V 3 = 658V, then UC = 115*658=757v。Therefore, in a power system with a system voltage of 1140V, the UC value of the surge protector should be at least greater than 757V.
Fourth, the selection principle of UC value.
Secondly, after calculating the minimum required UC value, in GB 188021-2011 Standard Specification for New Energy Requirements and Test Methods for Surge Protective Devices for Low-Voltage Distribution Systems No. 5Among the 5 optimum values of the maximum continuous working voltage UC of AC or DC, the voltage greater than the calculated minimum UC value is selected, and the specific preferred values are as follows:
When selecting UC values, one should not blindly select excessively large UC values from preferred values. Although the larger the UC, the longer the life of the surge protector, bigger is not always better. A large UC value will directly lead to an increase in the UP value of the surge protector, thereby reducing its protection effect on the back-end equipment. At the same time, a high UC value will also lead to an increase in the number of surge protectors. Therefore, when choosing a UC value, performance and cost should be reasonably considered. For systems with a system voltage of 1140V, we recommend a surge protector with an UC value of 1000V, which can take into account both service life and cost.
Through rational UC value selection, it can ensure that the surge protector can play the best role in the system and achieve effective power system protection.
Editor in charge: Yi Zao.