Is it simple to connect photovoltaic modules in a solar installation or plant? Is there a right way? In this article, we will analyze the correct way to wire between solar panels.
It is important to pay attention to the correct way to make electrical connections between photovoltaic system modules. You can't just plug one module into another.
Some aspects must be observed both to guarantee the correct functioning of the system and to reduce cable consumption.
The most common mistake made by installers, and even by many designers, is connecting modules in series as shown in the figure below. This would be the simplest and most obvious way to connect things in series.
The positive pole of one module is connected to the negative pole of the other and so on. The modules in the top row are connected to those in the bottom row and so on, until reaching the end of the string (set of modules in series). There are two terminals at both ends (one positive and one negative), as seen in the figure below.
Electromagnetic induction in circuits
What is the problem with the connection in the previous figure? The modules are all connected and that's all that matters, right? Wrong!
A good photovoltaic cabling design must take into account the danger of electromagnetic induction caused by atmosferic discharges. When an atmospheric discharge (commonly known as lightning) falls near a photovoltaic installation, a strong magnetic field is generated.
This magnetic field, when passing between the cables of the photovoltaic circuit, can induce dangerous voltages. These induced voltages, characterized as a voltage surge (short-term, high-intensity peak) can burn the components of the photovoltaic system. The most sensitive component, which suffers most from the occurrence of atmospheric discharges, is the DC-AC inverter.
In the figure above, we see the correct way to carry out the same photovoltaic installation shown in the initial figure. The modules are the same and are all in series – apparently nothing has changed. What is the difference?
The change is in the way connections are made. In the figure above we see that the green circuit (unlike the red circuit) forms a much smaller loop area. In practice, what must be done is to always pass the positive and negative cables of the circuits in parallel, keeping them close by tying them with cable ties.
The reason for the concern with minimizing the loop area of the photovoltaic module connection circuits can be understood in the figure above. The magnetic field induced by the atmospheric discharge produces an induced voltage proportional to the area of the loop. The smaller the space between the conductors, the less chance there will be of a voltage surge causing damage to the photovoltaic installation.
Photovoltaic project standard
In addition to being a good electrical installation practice, the reduction of the areas of loops formed by photovoltaic module circuits is provided for in Section 6.2.6.2 of the draft standard ABNT NBR 16690 (Low voltage electrical installations – Photovoltaic arrays), based on the international standard IEC 62548 (Photovoltaic (PV) arrays – Design requirements).
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