- For solar plant operators, the challenge is to find the perfect balance between achieving the highest possible energy yield at the lowest cost without compromising safety, reliability and efficiency.
- Photovoltaic modules degrade over time. Their output must therefore be monitored closely to gauge their viability.
- To best understand PV degradation, DC performance must be measured to remove the effect of inverter efficiency from the data.
Understanding degradation effects and contributors
Photovoltaic (PV) array degradation is an important aspect to consider for system design and installation. Over time, factors such as weather and UV exposure contribute to solar cell performance decline. By better understanding degradation effects and contributors, safeguards and technology enhancements can potentially be considered for performance improvements.
A key component to monitor, tied to effectively understanding degradation, is DC input voltage to the inverters. This must be measured for two reasons. First, understanding the DC performance allows the effect of inverter efficiency to be removed from the degradation data. Second, the inverter technology itself can be better evaluated, as the DC measurements allow for the characterization and understanding of inverter efficiency, key to overall system performance.
Electrical measurement solutions from Knick Interface, such as the P29000 voltage transducer series, are good solutions to consider for monitoring of DC input voltage to PV inverters. They have proven to bring value, many times over, in PV applications globally.
The P29000 measures DC voltage to 1000 V. A typical PV system of 30kW could see voltage signals fluctuate between 0 and 500 VDC, with a level such as 320 VDC seen during normal operation. This makes the input range of the P29000 more than capable of handling the demands of the application. Its measurement error of no more than 0.2% ensures that accuracy of the PV input voltage data is maintained. This accuracy exceeds the requirement set by IEC 61724-1:2017, which defines standards for PV monitoring systems. (Class A precision per IEC 61724-1:2017 calls for an uncertainty in measurement of <= 1% to be maintained.) In addition to satisfying the IEC standard, the P29000 is also UL listed, which is typically a requirement PV system builders and owners need or prefer to maintain with integral components.
Integration into control & data capture systems
With its flexibility and options associated with output selection, the P29000 makes it easy to integrate into existing control or data acquisition systems. Voltage input ranges, in addition to desired outputs such as 4-20 mA and 0-10 VDC, are selectable via dip switches on the device. Additional flexibility is provided by its onboard 20 – 253 VAC/DC universal power supply, and din-rail mountable 17.5 mm housing.
Electrical system safety is also present with the P 29000, through complete galvanic isolation at this same 1000 V level. This means the input, output, and power supply channels are all electrically isolated by way of transformers. By having this isolation in place, equipment protection concerns associated with voltage spikes can be minimized. Often, this brings peace of mind to PV array installations.
Return on Investment
- High operational safety and accuracy through measurement and electrical isolation up to 1000 V AC/DC
- Satisfies important requirements of the solar industry, including UL product certification and Class A precision per IEC 61724-1:2017
- Value shown through flexibility with calibrated range selection, onboard universal power supply, and din-rail mountable 17.5 mm housing.
Knick Interface author:
General Manager at Knick Interface LLC, USA
Phone: +1 888 62 KNICK