Campbell CR-PVS1, Руководство по эксплуатации продукта

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CR-PVS1 PV Soiling Loss Index RTU
6
TABLE 6-2. 110PV Wire Colo u r, Function, and CR-PVS1 Connections
Sensor Wire Colo u r Function CR-PVS1 Terminal
REF
Black Power
VX1
Red Signal SE1
Violet Ground
G
Clear Shield G
TEST
Black Power VX2
Red Signal SE2
Violet Ground
G
Clear Shield G
The CR-PVS1 has a Modbus RTU output. For the complete Modbus Register
Map, see Appendix B ,
Modbus Register Map
(p. B-1)
.
7. Operation
7.1 Measurement
To estimate soiling loss index (SLI), the CR-PVS1 system compares the
outputs and temperatures of two identical PV panels mounted side by side: one
clean, and the other soiled naturally.
Current measurements and back-of-panel temperature measurements are made
every 30 seconds. To make the current measurements, both panels are short-
circuited for 5 seconds using a solid-state relay. Short-circuit current is
measured with a precision current-sensing shunt. To help minimize PV panel
degradation, the panel is maintained in an open-circuit hold state between
measurements.
From short-circuit current and back-of-panel temperature, the effective
irradiance of each panel is calculated in accordance with IEC 60904, and the
SLI is calculated according to equation 7-2 .
A daily average SLI is calculated, available for SCADA (supervisory control
and data acquisition), and stored in onboard memory. For immediate feedback,
a real-time index and quality factor are available. Raw measured data are stored
and available for analysis or independent post-processing. Available values are
shown in Appendix A , Glossary of Variable Names
(p. A-1)
.
In accordance with IEC 60904, the CR-PVS1 calculates the daily soiling loss
index during the hour before and the hour after solar noon and only includes
the values showing effective irradiance greater than 500 W/m
2
to minimize the
effects from the zenith angle of the sun, PV panel current dependence on
irradiance level, and air mass density. The CR-PVS1 also filters out data that is
classified as unstable (IEC 60904), such as data during cloud cover. A variable,
Stable_Data_Count
, increments when all criteria are met.
FIGURES 7-1 through 7-5 show the importance of filtering data based on
stability of irradiance as well as back of module temperature in accordance
with IEC 60904-2. FIGURES 7-1 and 7-2 show effective irradiance calculated