Breathing New Life Into Legacy PV Installation

Breathing New Life Into Legacy Utility-Scale PV Installations. Most legacy utility-scale PV installations, as well as a good number of new installations, do not monitor PV currents at the string level. Current data is often only available starting at the inverter, and this is after several PV strings have been joined together at one or more combiner boxes. As a result, an owner-operator has poor visibility at the string level. This makes it challenging to remotely diagnose a reduction in combined PV string output at the inverter level. As a result, a crew must be dispatched to identify the PV string (or strings) causing the reduction, diagnose the cause(s), and then make the appropriate repairs. These costly O&M “truck rolls” negatively affect the ROI for the owner-operator. New technologies have emerged to improve the ability to identify faulty PV strings. One is to utilize drones which are equipped with cameras specifically chosen to detect PV activity. The plus side of this is a large PV installation can be quickly scanned by one operator to find hot spots, dead strings, and so forth. The downside of this is that it is reactive rather than proactive. This means the operator is already experiencing downtime in some of their PV strings, which adds up over time. Another available technology is to actively monitor each PV string current in real time and watch for changes over time. This method requires up-front work in SCADA, but once in place will allow the operator to proactively watch their PV strings and then take appropriate action when changes are first detected. It also diagnoses which string(s) are involved, which can be relayed to the O&M team heading out to do the service call. This reduces the amount of time diagnosing the issue, thus reducing the cost of the service call. It is important to choose solutions which are robust and can hold up in the demanding environment of PV installations. An example solution will be presented, which will demonstrate how to add current monitoring to each PV string, aggregate the strings into useable data, and then transmit the data back to a home office where it can be analyzed via SCADA.