Definitions

Rainfall

In mm recorded that day, reset at 12am. Rainfall is measured with an accuracy of ±2% for intensities from 24 to 300mm/hr, ±3% for intensities from 300 to 500mm/hr. (TB3A Rain Gauge) 10 second samples are averaged over 5 minutes.

Wind Speed

In metres per second. This is measured by an anemometer (Windcap Ultrasonic Windsensor WS425) installed on site at 8m , with an accuracy of 0.135m/s (0.3mph, 0.26 knots) or 3% of the reading, whichever is greater. 10 second samples are averaged over 5 minutes.

Temperature

Measured in degrees Celsius on site at 2m with an accuracy of ± 0.2ºC. (Vaisala HMP45A.) 10 second samples are averaged over 5 minutes.

Diffuse Insolation

Is light that has been scattered by atmospheric particles out of the line of direct radiation from the sun. This is expressed in kW/m2, and measured on site. 95% of individual readings will be within an interval of ± 8% ± 10w.m2. (Delta T SPN 1 Sunshine Pyranometer) 10 second samples are averaged over 5 minutes.

Global Insolation
Energy in sunlight on a horizontal plane at the surface of the earth, measured in kW/m2. 95% of individual readings will be within an interval of ± 8% ± 10w.m2. (Delta T SPN 1 Sunshine Pyranometer) 10 second samples are averaged over 5 minutes. (Note: Global insolation is plotted as sunlight on the interactive graphing page.)
Humidity
Relative humidity, expressed as a percentage. This is measured on site at 2m, with an accuracy of 2% at 0 - 90% humidity, 3% at 90 to 100%. (Vaisala HMP45A.) 10 second samples are averaged over 5 minutes.
kWh a del-rec, kWh b del-rec, kWh c del-rec, kWh tot del-rec
Total kWh delivered less received for each phase, and the system total. This is a cumulative record, since system install, with 1 second readings reported every 5 minutes. This is measured with a Class 0.2 meter with ± 0.2% accuracy. (Ion 7550, CT: 5/100)
5-Min-Avg kWa, 5-Min-Avg kWb, 5-Min-Avg kWc, 5-Min-Avg kWtot
Phase and total AC power in kW. One second readings are averaged over a 5 minute period. This is measured with a Class 0.2 meter with ± 0.2% accuracy. (Ion 7550, CT: 5/100) Master (Combined Technologies) Voltage/Current
5-Min-Avg V1THD, 5-Min-Avg V2THD, 5-Min-Avg V3THD
Total Harmonic Voltage Distortion for phases a,b and c (as 1, 2, 3): the ratio of the powers of voltage harmonic components to the power of the base frequency. Accuracy is ±1.0%. (Ion 7550, CT: 5/100)
5-Min-Avg Vln a, 5-Min-Avg Vln b, 5-Min-Avg Vln c.
Line to neutral AC voltage for each phase, measured with an accuracy of ± 0.1%. (Ion 7550, CT: 5/100)
5-Min-Avg Ia, 5-Min-Avg Ib, 5-Min-Avg Ic
AC current on each phase in Amperes with an accuracy of ±0.1%. (Ion 7550, CT: 5/100)
5-Min-Avg Vllav
The average of the 3 line to line voltages, with one second values averaged over 5 minute periods. This is measured with a class 0.2 meter, with an accuracy of ± 0.1%. (Ion 7550, CT: 5/100) Master (Combined Technologies) Power Quality
5-Min-Avg PFa, 5-Min-Avg PFb, 5-Min-Avg PFc
Power Factor, for phases a, b and c, expressed as a percentage. This is measured with ± 0.2% accuracy. One second samples are averaged over 5 minutes. (Ion 7550, CT: 5/100)
5-Min-Avg Freq
AC frequency measured in Hz, with an accuracy of ± 0.005Hz. One second samples are averaged over 5 minutes. (Ion 7550, CT: 5/100)
5-Min-Avg I1THD, 5-Min-Avg I2THD, 5-Min-Avg I3THD
Total harmonic current distortion for the phases a,b and c (as 1, 2, 3.) This is the ratio of the powers of all current harmonic components to the power of the base current frequency. Accuracy is ± 1.0%. One second samples are averaged over 5 minutes. (Ion 7550, CT: 5/100)
kWh Del-Rec
Total kWh delivered less received. This is the accumulated value over the life of the system, with readings taken every second and reported every 5 minutes. This is measured with a Class 0.5 meter with ± 0.5% accuracy. (Ion 6200, CT: dependent on technology - see below.)
5-Min-Avg I
AC current measured in Amperes, one second samples averaged over 5 minutes. For readings below 5% of the full scale, accuracy is 0.3%, for greater than 5% of the full scale accuracy is 0.3% + 0.05% of the full scale. (Ion 6200, CT: 50/5 except Solar Inception large scale trackers: 100/5.)
5-Min-Avg kW
AC power in kW. One second readings are averaged over a 5 minute period. This is measured with a Class 0.5 meter with ± 0.5% accuracy. (Ion 6200, CT: 50/5 except Solar Inception large scale trackers: 100/5.)
5-Min-Avg ITHD
Total harmonic current distortion This is the ratio of the powers of all current harmonic components to the power of the base current frequency. Accuracy is ± 1.0%. One second samples are averaged over 5 minutes. (Ion 6200, CT: 50/5 except Solar Inception large scale trackers: 100/5.)
Performance Ratio

This is a quantity which is commonly use in the PV industry to assess the performance of PV systems. It represents the ratio of the actual energy produced by a PV system, with respect to the energy which would be produced by a “perfect” system continuously operating at STC under same irradiance (Incident Global in the plane). With the introduction to the DKASC of an new “in plane of the array” (POA) pyranometer in 2015 this value is now automatically calculated for all fixed arrays at the DKASC and is available in the downloaded historical data (PR values commence from May 2015 onward). The PR value for tracking arrays using a fixed pyranometer is not valid therefore not calculated. It is also important to note that the POA pyranometer that is used for these calculations is located near Site 23 and in intermittent cloud conditions the short term irradiance at the POA pyranometer may differ significantly from to the at some of the more distal arrays and therefore the results under these conditions will not be valid.