690.8 A.2 Photovoltaic Source Circuit Currents

can anyone help me to learn how to calucate "The calculated maximum current value shall be
based on the highest 3-hour current average resulting
from the simulated local irradiance on the PV array
accounting for elevation and orientation."  how to use SAM to do calculation?

For PV systems with a generating capacity of 100 kW or
greater, a documented and stamped PV system design,
using an industry standard method and provided by a
licensed professional electrical engineer, shall be permitted.
The calculated maximum current value shall be
based on the highest 3-hour current average resulting
from the simulated local irradiance on the PV array
accounting for elevation and orientation. The current
value used by this method shall not be less than
70 percent of the value calculated using 690.8(A)(1)(1).
Informational Note: One industry standard method for calculating
maximum current of a PV system is available from Sandia
National Laboratories, reference SAND 2004-3535, Photovoltaic
Array Performance Model. This model is used by the System Advisor
Model simulation program provided by the National Renewable
Energy Laboratory.

Hi Xingguang Yu,

This guidance from the National Electric Code is a vague on how to use the Sandia Photovoltaic Array Performance Model for this purpose. There are several online articles on this subject that might be helpful, and this informative webinar recording from Terrabase Energy: www.terabase.energy/post/webinar-recording-increasing-string-length-using-advanced-voltage-modeling-techniques

We are working to update SAM's System Sizing macro (click Macros under the Simulate button to see a list of macros) to follow these guidelines. The current version is based on older string sizing approaches.

Note that SAM does not report the array operating current, but it does report the array DC power (Subarray x DC power gross) and both the operating voltage (Subarray x Operating DC voltage) and open circuit voltage (Subarray x Open circuit DC voltage), so you can calculate the current from those values.

Best regards,
Paul.

Best regards,
Paul.