What are the PV array measurement equipments on the market?
PV Array Measurement Equipments are available in the market, and each one serves a purpose. Any electrical or electronic system can be characterized by measuring the voltage and current relationship at its terminals at different current levels. Moreover, a plot of voltage against current is known as the V-I curve, and the slope of the V-I curve will give the output or series resistance, often written Rs, of the system-in this case the panel or array of panels. In addition, the output resistance plays a very important role in determining the power available from the panel. The other important figures are the open circuit voltage, and the short circuit current, which are derivable from the VI curve, which can also give a quick estimate of the series resistance. It is to be remembered that we should expect the VI curve to be different at different illumination levels.
Solar Analyzer, I-V Curve tracer
Among the most known PV array measurement equipments, the most comprehensive array measurements are normally provided by a good Solar Analyzer. This instrument does not analyze the solar insolence, as the name suggests. Actually it analyzes mainly the photo voltaic panels and the system tie up. It treats the solar panel as an electrical device, and measures its parameters, mainly open circuit voltage, short circuit current and the V-I relations at various current levels. These three things are good indicators of the health of a panel as a whole. It is able to plot the VI curve data, which gives a wealth of information about the panel.
Furthermore, the analyzer can treat a whole array as a system and test it, after which a faulty panel can be isolated. Once a panel is found to be below par, you may decide to isolate the faulty cells, or contacts and see if a replacement or repair is possible.
IR Imaging Camera
The IR imaging camera can show a temperature map of the system in view. Any hot spots and any cold spots can be noted against a normal picture. Loose connections will show as hot spots. Any dead element may show colder than normal. Defective cells in a panel could be indicated by a temperature different from the rest. A feel with a hand can also be useful. But the best way to locate such cells is IR imaging, where different cell temperatures will stand out in the picture.
Voltmeters, Ammeters and Power meters
These meters are required to monitor the system, for fault isolation and rectification. The current capability will be according to capacity of the installation. For DC meters the voltage can be up to 30 volt. Meters can be fixed or portable. Clamp meters are useful for measuring current without breaking a circuit.