C27 - Troubleshooting Solar Plant Failures Through Impedance Testing; How It Works and Why It’s Better

Troubleshooting solar plant issues can be a complex task for O&M providers, but it doesn’t need to be. Emazys has discovered that the impedance of a photovoltaic array is key information to evaluate lifetime faults and safety hazards. This data can be used to not only detect plant faults and failures, but also pinpoint the exact location of ground faults within the array, in less than five minutes. This poster presentation will explain how impedance spectroscopy works, how it can be used for reactive and preventative maintenance, and the advantages when compared to traditional troubleshooting methods.
Regardless of how well a solar PV plant is planned and constructed, it will experience issues and malfunctions at some point throughout the lifetime of the array. These issues are complex in nature and vary from system to system, but one common issue is ground faults on the DC side of the PV array. It is estimated that 50% of all PV ground faults go undetected. Not only do ground faults have a negative financial impact on the solar array, but they are also a safety hazard. Ground faults normally do not occur spontaneously, but rather they manifest over time as the electrical insulation of the PV array degrades. Through the Emazys technology, it is possible to locate and mitigate the faults, before they manifest in the PV system and impact the return on investment.

Ground faults are short circuit faults that lead to electrical current flow in the grounding gear connecting the DC power generation and the System Power Components. The electrical isolation resistance Riso can vary over time when insulation materials degrade. The portable, battery-powered Emazys Z200 performs impedance spectroscopy between connected string terminals, and measures the terminal voltages and currents flowing under various DC loads introduced by the instrument. Unique to impedance measurements, the position of the ground fault can be accurately determined at Riso < 3M. This is well before the inverter shuts down production and it avoids even larger leakage currents.

When it comes to traditional troubleshooting methods, the challenge is that most known methods measure Riso with "voltage pulse" testing. This type of testing is not adequate for pinpointing faults in the early stages. Several factors like the real-life fluctuating values of Riso, the intermittent nature of faults, and the internal resistance of voltage testers make it complex to troubleshoot faults in an accurate and consistent way. Plus, "voltage pulse" testing may cause damage to the PV equipment by ionizing metal parts and thin conductors in the system. Impedance testing however is gentle on the PV array.

The goal in troubleshooting solar PV plants is smooth operation and limited impact of system failures on energy production. Impedance spectroscopy is a superior method to reduce solar plant downtime and stop it before it occurs.