Current leakage in photovoltaic systems - identification, quantification and treatment
The issue of leakage in photovoltaic energy systems is controversial and you will find a large number of professional opinions on the subject. Some recommend completely ignoring the matter, while others do recommend monitoring the phenomenon and executing a systemic solution once every few years, and there are those who recommend treating the phenomenon as soon as possible - allocating the problematic component with the defective insulation. Who is right? Well - probably all and it really depends on the case.
The leakage phenomenon occurs in the components on the left side of the diagram: panels, connectors and converters.
Current leakage is a fairly common systemic phenomenon in photovoltaic energy installations and it shows even in new systems, although it is clear that the age of the system plays a role. As the components age the phenomenon is increasing. The leakage results from a defect in the insulation of one or more of the components in a solar system. The phenomenon can occur in the panels themselves, in the electrical connectors and believe it or not - in the inverters themselves. For the most part, this is a negligible energy loss of output of a few tenths of a percent or a few percent during the year. However, in more serious cases those leakages reduce 5-10% of system's output throughout the year and here it is already a problem that requires a solution.
Today, the monitoring and operations software solutions do not always provide a clear indication of the existence of current leaks and of course do not quantify the resulting energy loss. In SMA's Sunnyportal monitoring software, for example, it is possible to receive messages and alerts concerning the existence of the leakage, but it is not possible to know its quantitative severity, so this is not really useful; Whereas in the SolarEdge monitoring portal, we will not see any indication of leakage at the system level, but only when examining the specific innverter log. In fact, the main way to examine the severity of leakage in a solar PV system is a manual qualitative examination by a professional who might have no way to accurately determine the severity of the phenomenon. An advanced solution to allow accurate quantification of leakage severity and calculation of annual potential resulting from the phenomenon must involve performance analytics.
One such quantitative performance analytics solution is provided with the technology of Soltell Systems. Thus, it is possible to know ahead of time about the development of a current leakage process and treat the problem at the exact timing when it shows signs of worsening beyond desired cost-efficiency. Due to the complexity of dealing with insulation failures, it is clear that if during a calendar year the leakage detracts less than the cost of a technician examination, there is probably no urgent need to deal with it.
The leakage phenomenon increases during the wet months, when moisture and humidity lower the resistance in the weak points of insulation. As a result, the inverters refuse to start operation in the morning until the system resistance rises above the permissible value. The allowed value of the resistance is of course different for each innverter and here in fact hides a partial solution to the problem - correct calibration of innverter settings may reduce the phenomenon. Nevertheless, you will probably find that most of inverters are already set correctly during the system installation.
Another conventional way of treating the leakage phenomenon in a solar PV system is the replacement of all the connectors in the system, which to a large extent reduces the phenomenon. At the same time, it should be mentioned that although connectors are a weak point in terms of insulation in a photovoltaic system, they are really not the only cause of leakages. Thus, although in some cases a comprehensive replacement of all the connectors is indeed necessary - it is not a suitable solution for every system and of course it is a rather expensive solution.
Certainly, the most effective method for handling current leaks in a photovoltaic system is a professional insulation test by a qualified electrician with an appropriate measurement equipment. The insulation test makes it possible to effectively locate the cause of the leakage phenomenon in a system and neutralize it. As already stated above, in many cases these are worn connector cables that can be easily replaced. Encapsulation defects in solar panels are also a common phenomenon, and in such cases the faulty panel can be replaced or an electrical bypass can be performed. Finally, it is possible that the leakage is due to insulation wear inside the innverter itself and then the treatment may require a service call to an inverter technician.
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