Common electrical problems in photovoltaic systems and how to deal with them

Problem 1: Hot spots on components

The main causes of hot spots are: module quality problems (excessive internal resistance), cracks and partial surface shadows.

Hot spots can cause serious damage to PV modules or systems and can lead to fires, but they are difficult to detect by visual inspection alone, so it is best to use an infrared camera to detect them.

Problem 2: Failure to meet expected electricity production

Solar resources are measured in terms of peak sunshine hours, i.e. the number of hours in a day when 1,000 watts per square metre of solar module output can be achieved.

The number of hours of peak sunlight can be influenced by many factors, in particular the time of day, the season and weather conditions. Therefore, the location and angle of the solar module plays a crucial role in the amount of electricity generated.

After installing the system, the electrical parameters and the actual power output of the components are measured to ensure that they work as designed. The IV curve of the power output is calculated using a combination of a solar irradiance meter and a multifunctional tester.

Even when installed correctly, a PV system may not achieve the expected power output. In order for the PV system to achieve the desired output, it is important to ensure that the system is able to receive the correct amount of irradiated energy. It is necessary to test the irradiance of the current module position using a solar irradiance meter and repeatedly adjust the angle until the position with the highest irradiance is found.

Issue 3: Electrical faults in PV systems

The most common PV system problems are usually related to panels, loads, earthing and inverters.

-PV panel faults.

Before checking, the input voltage and current levels of the inverter need to be recorded and the following problems may be encountered.

The whole PV system shuts down/does not generate power - probably a problem with the inverter;

PV system output is lower than expected - may be a module or module problem.

It is recommended to start along the line from the current sink, using a current clamp meter will greatly improve the efficiency of the investigation.

The types of faults that can occur are

-Dirt, wiring problems and loose connections (especially the connection nuts between components);

-Shadows or dust on the module (which can lead to reduced output)

-Photovoltaic load faults.

1. Check that the correct voltage is present at the load connection. If the voltage is too low, it may be necessary to reduce the circuit load or use a larger wire.

2. Check the fuse and circuit breaker and replace the faulty fuse/breaker if there is a problem.

3. If the load is an electric motor, the internal thermal circuit breaker may have tripped or the winding in the motor may be open. Another load needs to be replaced and then checked for proper operation.

-PV ground faults.

DC ground faults are a common type of fault in PV systems and are usually caused by poor current flow through the equipment ground conductor due to damaged ground conductor insulation, improper installation, pinched conductors and water ingress.

DC earth faults are particularly dangerous in large PV systems as they are not easily detected and are extremely hazardous. Ground fault protection (GFP) equipment cannot detect small current leaks (< 1A) in ground faults, so this is known as a "blind spot". In the event of a fault, not only does this cause a safety problem, but it also creates a fire hazard.

If there is no earth fault, the voltage measured from any of the conductor terminals should be 0V.

If there is an earth voltage on any of the conductors, check each connection point (DC disconnect, busbar) all the way back to the component. Replace the conductors as soon as a fault is found and keep a record of the test and replacement.

-PV inverter faults.

If the inverter is not producing the correct output, the output voltage current and power of the inverter needs to be checked with a clamp meter at AC measurement and compared with the values recorded during the last check. As the load on the inverter may require too much current, the load can be reduced or a larger converter can be installed.

In addition, any voltage problems with the power company may cause the inverter to shut down.