A spike of power hit the building where we completed an installation. The system did not have proper surge protection. The inverters were fried and we are now replacing them. Before we complete the installation, I want to measure the panels and make sure they were not effected by the surge prior to doing the work of installing them.
My question is how do I measure the voltage, current and resistance of the panels before I hook it up to the system? When I do, what should the readings show?
Thanks-
Submitted
12 years 9 months ago
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Jeff- This is a very good question, that gets ask all the time.
The easiest way to measure a panels voltage, current and resistance before you install it is to use a mulitmeter. A multimeter or multitester also know as a VOM (Volt-Ohm meter) will measure all of these electrical measurements in one devise. The multimeter is available in many different types but you really don't need to pay more than $40 for a basic unit and can pay as little as $15.
To use the devise, simply point the panel into the sun and touch the needle to the terminal on each of the leads coming out of the panel. If everything is working correctly you should measure readings that are relatively close to the specification on the datasheet of the panel. Remember, the specs on the data sheet are taken at STC.
Sorry to hear about the spike that caused these problems. Surges can also be caused by a lightning strike. You might want to review a recent article on surge protection from lightening strikes.
Usually, a voltage spike from the grid, which can turn an inverter into a smoking hulk, won't reach the connected modules. Lightning, on the other hand, can damage the diodes in a module or their wires, but that damage might not show up with a multimeter voltage test.
The only way to check a module is to connect it to an IV Curve tracer, such as a Daystar. These are very expensive, but if you Google around, you might find a rental unit.
SF_Solar-
Another tool that you can use is the Solmetric PVA-600 PV Analyzer
The Solmetric PV Analyzer is a complete electrical testing tool for verifying photovoltaic array performance. For each string, the analyzer measures current and power as a function of voltage. Measured results are compared to the performance predicted by advanced built-in models. It is a great full solution to testing the modules.