GB/T 39462-2020 in English

Technical background and evolution of the standard

With the popularization of DC application scenarios such as photovoltaic power generation and data centers, traditional AC safety standards can no longer cover the special risks of DC systems. This standard systematically establishes a safety assessment framework for 1500V and below DC systems for the first time, filling the gap in domestic low-voltage DC safety standards.

Comparative analysis of core safety factors

Detailed explanation of key safety requirements

5.8 Special features of overvoltage protection

For DC systems, special attention should be paid to the risk of overvoltage caused by polarity reversal. It is recommended to use bidirectional suppression type SPD. According to Article 5.17.4 of the standard, PV systems should use surge protectors certified by GB/T 18802.31-2016.

5.14 Grounding system selection

The standard clearly gives priority to IT/TN-S grounding types:

• IT systems need to be equipped with insulation monitoring devices (10-30kΩ)
• TN-S systems must use DC-RCD
• TT systems are prohibited (fault identification is difficult)

Implementation suggestions

Equipment selection specifications

According to the requirements of Clause 5.17:

1. Circuit breakers should be selected as non-polarity type, with breaking capacity greater than reverse fault current
2. Fuse types should be selected according to system time constants
3. Plug-and-play devices need to have built-in arc suppression modules

Key points for installation acceptance

According to Clause 5.20:

• Cable polarity marking should comply with GB/T 4026-2019
• Capacitance to ground should be within the system allowable range
• Different voltage levels must be physically isolated