The selection of surge protector (SPD)s in the consumer unit box should follow the following principles. First, understand the characteristics and sensitivity of the electrical equipment to be protected, including rated voltage, rated current, fault voltage tolerance, etc. Secondly, according to the environmental conditions of the electrical equipment, consider the surge voltage peak value and frequency range that it may face. Next, choose a surge protector (SPD) with a rated operating voltage greater than the rated voltage of the device you want to protect, and make sure its operating current is large enough to handle the surge current. Also, consider the response time, durability, and reliability of your surge protector (SPD). Finally, make sure that the selected surge protector (SPD) complies with international standards and relevant certification requirements to ensure its quality and performance meet the regulations. Taking these factors into consideration, choosing a suitable surge protector (SPD) can ensure that electrical equipment is effectively protected from surge voltage.