Selection Of Solar Photovoltaic Surge Protector

Since photovoltaic equipment is exposed to the outdoors for a long time and the electronic components of the inverter are very sensitive, effective lightning and surge protection is essential to ensure its service life. The main reasons for surges in photovoltaic equipment are: inductive or capacitive coupling voltage caused by lightning discharge and switching operation of the upstream power system. Surges caused by lightning can damage photovoltaic modules and inverters, causing serious consequences for the operation of the equipment. The following article introduces the selection of photovoltaic surge protectors from two aspects.

1. Selection of SPD on the AC side

According to GB/T 18802.32, the SPD used to protect the AC measurement of the photovoltaic system should follow the provisions of Chapter 534 of IEC 60364-5-53:2015. It is specially marked that the voltage between the AC conductor and the ground depends on the inverter technology and is not always a standard sinusoidal AC voltage. When selecting SPD on the AC side, it is advisable to consider voltage waveform distortion, such as expected obvious spikes, which is usually called harmonic interference. Therefore, when selecting SPD, not only should the applicable parameters be selected, but also SPD with anti-harmonic function should be selected.

2. Selection of SPD on DC side

According to GB/T18802.32, due to the specific UI characteristics of photovoltaic systems, only SPDs explicitly designated for photovoltaic DC side can be installed, and these SPDs should comply with the requirements of IEC 61643-31.

When selecting, in addition to conventional parameters, two parameters should be noted: Ucpv and Iscpv.

Ucpv: The maximum continuous operating voltage Ucpv of all SPD protection modes (positive/negative, positive/ground and negative/ground) should be greater than or equal to the maximum open circuit voltage Uoc max of the photovoltaic array under all conditions of use.

Iscpv: When the battery is connected to the DC circuit, additional requirements must be met because the short-circuit current provided by the battery may be much higher than the current that the photovoltaic array can provide.

Depending on whether the DC side of the photovoltaic system is grounded, different internal connection methods of the SPD are selected:

The connection methods of the SPD on the DC side of the grounded photovoltaic system can be divided into two types: I type and L type

The connection methods of the SPD on the DC side of the ungrounded photovoltaic system can be divided into three types: Y type, triangle type, and U type. Usually, photovoltaic systems often use ungrounded systems.