When the distributed photovoltaic system is designed for lightning protection, it is first necessary to consider installing lightning rods to prevent damage to the photovoltaic power station by direct lightning strikes. At the same time, it must also consider preventing lightning induction and lightning waves from invading the photovoltaic power generation system.
Main measures for lightning protection design
The distributed photovoltaic system is a three-level lightning protection building. The lightning protection and grounding design needs to involve the following aspects:
1. Set up lightning rods to prevent low-altitude direct lightning strikes
2. The solar cell array bracket is reliably grounded;
3. In the solar cell square array junction box, install lightning arresters at the input and output, and the chassis are reliably grounded;
4. Equipment room equipment needs to be reliably grounded;
5. Thunder protection isolators are installed at the entrance and exit of the control room, and lightning protection devices are installed inside to prevent inductive lightning.
Material selection for lightning protection grounding system
For lightning rods, round steel with a diameter of 12-16mm is generally used. If a lightning protection belt is used, round steel with a diameter of not less than 8mm or flat steel with a thickness of not less than 4mm is used.
The grounding body should be hot-dip galvanized steel. Its specifications are generally: steel pipe with a diameter of 50mm, wall thickness not less than 3.5mm; 50mm*50mm*5mm angle steel, length not less than 2.5m; or flat steel of 40mm*4mm, length is generally It is 2.5-4m.
It is advisable to use hot-dip galvanized round steel or flat steel for the down conductor. Round steel should be preferred, and the diameter should be no less than 8mm. If flat steel is used, the thickness should be no less than 4mm.
By installing a surge protector on the live cable to reduce the damage caused by surge and lightning overvoltage, the PV system needs to take the following protective measures:
1. Surge protection device is installed on the DC input end of the inverter and the AC output end.
2. Install a surge protector in the grid connection power distribution box (distribution cabinet) to protect against lightning waves entering the connecting cable. In order to prevent the circuit breaker from short-circuiting when the surge protector fails, a circuit breaker or fuse must be connected in series with the front end of the surge protector. The rated current of the circuit breaker (fuse) cannot be greater than the overcurrent protection recommended by the surge protector product specification. The maximum rating of the unit.