This is the current Chinese designation for the standard that sets performance requirements and test methods for low voltage surge protective devices connected to power distribution systems, and it is the number that appears in Chinese approvals and in the specifications of switchgear and installation manufacturers today, the compulsory designation of the same requirement having lapsed. In Chinese practice the device standard is read alongside the national code for lightning protection design of structures, which determines where protective devices must be installed and what protection level is required at each position, so the selection of a device for a project begins with the code rather than with the product standard. Devices are not subject to compulsory certification but are commonly submitted to voluntary certification, and the test report against this standard together with the manufacturer's declaration of the protection level is what a Chinese designer will ask for.