In photovoltaic systems, it mainly includes photovoltaic arrays, inverters and monitoring systems, photovoltaic supports and AC power distribution cabinets.
Wiring of the PV array, we can no longer be familiar, as long as the positive and negative poles are connected, and then connected with the photovoltaic DC dedicated line to the inverter. However, the design of the DC loop is a neglected aspect. In many cases, the DC loop is also various shapes for convenience of wiring and cost saving. The overall is divided into the following two forms:
The area of the current flow loop is small, and the area of the DC loop of Figure 2 is large.
What are the main impacts of the area of the DC loop on the PV system?
In thunderstorm weather, when a negatively charged cloud layer is over an object, due to the capacitive effect, the ground object will accumulate a corresponding opposite charge (positive charge) toward the surface of the cloud layer. When the charge of the cloud layer discharges with other objects or clouds (that is, lightning and lightning strikes), the negative charge in the cloud layer disappears rapidly, and the capacitive effect disappears immediately. The positive charge accumulated on the surface of the object also flows to the earth immediately. A large voltage is generated on the path of the flow due to the resistance, which is the induced lightning overvoltage. This overvoltage may discharge to a nearby metal object and cause an induced lightning strike; for a photovoltaic system, it may be transmitted to the inverter through an electrical circuit, causing the electrical appliance to induce overvoltage discharge and damage.
The overvoltage generated by lightning strike is proportional to the area of the loop. The energy of the lightning strike is generally compared. The overvoltage is generally above 2000v. The maximum voltage of the inverter is mainly 550v, 1000v, 1100v and 1500v, which easily causes the internal power of the inverter. Electronic components were broken down and burned. Therefore, when laying the cable, the loop area of the photovoltaic array should be reduced as much as possible, as shown in Fig. 1, and the protection and shielding should be formed by using the bracket rail and the metal pipe as much as possible.
Post time: Sep-16-2019