Common electrical problems and solutions of photovoltaic systems

Problem 1 Hot spots appear on components

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

Hot spots can seriously damage photovoltaic modules or systems, and even cause fire accidents, but it is difficult to find them by visual inspection alone, so it is best to use an infrared thermal imager to check.

Recommended tool: Fluke VT06/VT08 Portable Thermal Imager

Small size, powerful function; hot spot is instant, fast and accurate; dustproof, waterproof and anti-drop, no fear of harsh environment

Problem 2: The expected power generation cannot be achieved

Solar resources are measured in peak sunshine hours, which are the hours per day that can produce 1,000 watts per square meter of solar modules. Peak sunshine hours can be changed by many factors, especially time, season and weather conditions. Therefore, the installation position and angle of solar modules play a crucial role in generating electricity.

After the system is installed, it is ensured that its performance meets the design requirements by measuring its electrical parameters and the actual power output of the components. Using the combination of a solar irradiance meter and a multi-function tester, calculate the IV curve of the power output.

Even when installed correctly, PV systems may not produce the expected power output. In order for the PV system to achieve the expected output, it is important to ensure that the system can receive the correct amount of irradiance energy. It is necessary to use a solar irradiance meter to test the irradiance of the current module position and adjust the angle repeatedly until the position which has the maximum irradiance is found.

Recommended tool: Fluke IRR1-SOL Solar Radiometer

Can support measurement of instantaneous irradiance of 1400 W/m2; support measurement of ambient temperature and panel temperature; built-in compass to measure direction and component tilt angle

Problem 3 Electrical faults in photovoltaic systems

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

PV panel failure:

Before inspection, it is necessary to record the input voltage and current level of the inverter, and the following problems may be encountered:

Entire PV system shuts down/doesn't generate electricity - possible inverter problem; PV system output lower than expected - possible component or module problem.

It is recommended to start the investigation along the line from the combiner box. Using a current clamp meter will greatly improve the investigation efficiency. Possible types of failures are:

 Dirt, wiring problems, and loose connections (especially connecting nuts between components); shadows or dust on components (which can easily reduce output)

 PV load failure:

 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 larger wires; check the fuses and circuit breakers, and replace the faulty fuse/breaker if there is a problem; if the load is a motor, the internal thermal circuit breaker may have tripped, or the windings in the motor may be open. Need to replace another load and see if it works.

Photovoltaic ground breakdown:

DC ground breakdown are a common type of fault in photovoltaic 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 ground breakdown are especially dangerous in large PV systems because they are not easily detected and can be extremely harmful. Ground breakdown protection (GFP) devices cannot detect small current leakage (< 1A) in a ground breakdown, so this is called a "blind spot". Once a malfunction occurs, it will not only cause safety problems, but also create a fire hazard.

Troubleshooting steps:

1. Use a multimeter for continuity test to check whether the fuse of the circuit breaker is blown;

2. Use an insulation resistance tester to check the insulation performance of the wire;

3. Identify the source of the ground breakdown

1) Remove the positive and negative wires to ensure that the inverter is isolated from the array;

2) Close the DC disconnecting device and apply voltage to the wire;

3) Measure the voltage between the positive and negative conductors to determine the open circuit voltage of the component;

4) Use a ground resistance tester to measure the positive grounding and negative grounding respectively.

If there is no ground breakdown, the voltage measured from either conductor to ground should be 0V.

If ground voltage is present on either wire, check each connection point (DC disconnect, combiner box) all the way back to the assembly. Once a breakdown is found, replace the wire immediately and keep a record of the test and replacement.

PV inverter failure:

If the inverter is not producing the correct output, check the output voltage, current and power of the inverter with an AC clamp meter and compare it with the values recorded during the last inspection. Because the load on the inverter may require too much current, reduce the load or install a larger converter.

If the problem persists, continue to check for possible faults with the clamp meter:

• blown fuse

• circuit breaker tripped

• disconnection

In the event of a power failure, all ground breakdown need to be checked and repaired before starting the drive again.

Also, any voltage problems with the power company can cause the inverter to shut down.

Recommended tool: Fluke 393FC photovoltaic clamp meter

DC voltage range of 1500V, ultra-thin jaw, specially designed for photovoltaics; integrated power measurement function, more with less effort; CAT III 1500V safety level, support real-time data transmission

Ground Insulation Test Tool

Fluke 1555 High Voltage Insulation Resistance Tester

10000V test voltage, professional insulation test; CAT III 1000V safety level, wireless control

Fluke 1625-2 KIT Ground Resistance Tester

Support multiple methods, professional grounding test; soil resistivity test function