GB/T 39750-2021Technology requirements of DC arc-fault circuit protection for photovoltaic power system (English PDF)

3.1 arc-fault detector; AFD

Device used for detecting arc-fault on the DC side of a photovoltaic power system and issuing fault alarm signals.

3.2 arc-fault interrupter; AFI

Device - installed on the DC side of a photovoltaic power system - that receives arc detection signals and implements arc extinguishing functions by means of disconnecting, short-circuiting, or switching.

3.3 4 Basic regulations

The action signal can be continuously issued by the controller or inverter. The arc detection signal channel and the photovoltaic string structure are shown in Appendix A.

When the protection equipment does not receive an action signal within 15 seconds, the protection action shall be triggered, and the requirements are as follows:

a) In a photovoltaic power system operating in grid connected mode, when the inverter is accidentally disconnected or the main grid voltage is lost, the external action signal shall be interrupted. The external action signal can also be manually interrupted by other switches or monitoring devices (such as fire alarm systems).

b) In a photovoltaic power system operating in isolated mode or temporary island state, when the system is shut down, the external action signal shall be interrupted.

6.5 Applicable scenarios of protection methods

The applicable scenarios of protection methods are shown in Appendix C, and they shall be selected reasonably.

7.1 Protection test equipment

7.1.1 General requirements

The test system for testing DC arc-fault circuit protection equipment shall include DC power supply, decoupling network, linear impedance network, arc generator, arc protector and other test equipment. The circuit structure diagram is shown in Appendix D. For inverter solutions that require an external DC combiner box, arc tests shall be carried out before and after the combiner box.

7.1.2 DC power supply

7.1.2.1 General requirements

The test system shall have a DC power supply, which can be a constant voltage power supply or a photovoltaic array simulation power supply.

7.1.2.2 Constant voltage power supply

The constant voltage power supply shall include an additional resistor. The constant voltage power supply is adjusted according to the maximum power point, and the requirements are as follows:

a) The constant voltage power supply shall be adjusted according to the open circuit voltage value corresponding to the arc test condition in 7.2;

b) The upper limit of the maximum current shall be set to 1.1 times the maximum working current value corresponding to the arc test condition in 7.2;

c) The total resistance value and relationship corresponding to the arc test condition in 7.2 are shown in Formula (1).

Where: Total resistance