The SPD combination modes include nP, nP+N, and nP+1. 3P+1 mode is used to raise the voltage (for example, the JLSP-GA750/100/3P+1 in the photovoltaic series is used to raise the voltage).The N in 3P+N refers to the addition of a gas discharge tube (under the action of this electric field, the gas inside the gas discharge tube begins to be ionized. When the external voltage increases to make the inter-electrode field strength exceed the insulating strength of the gas, the gap between the two electrodes will discharge and break down, and the original insulating state will be converted into a conductive state. After conduction, the voltage between the two electrodes of the discharge tube is maintained at the residual voltage level determined by the discharge arc. This residual voltage is generally very low, thereby protecting the electronic equipment connected in parallel with the discharge tube from damage by overvoltage).