The power flow analysis can be configured to work with seasonal or temperature based limits when specifying ratings for power transformers and conductors. For these types of devices, the upper limit that the device can be pushed to is heavily dependent on the ambient air temperature (in general, these devices can be pushed harder when the temperature is cooler since natural cooling can occur). Both the seasonal and temperature based approaches represent a mechanism to specify what the ambient air temperature is doing — with the temperature based approach providing much more possibility for granularity. Both approaches are global in nature so a project cannot specify one type of configuration for one area of the model and another approach for a different area. Any ratings provided for switches will have the standard concept of normal, short term emergency, and long term emergency limits.

For seasonal based limits, projects will pre-configure a set of date ranges that define seasons applicable to the geographic region. The quantity of seasons and dates associated with each season is configurable so, for example, if only two seasons were needed, a project could set up Winter and Summer seasons. When providing limit data to use for conductors and power transformers, values need be provided for each season in the Power Flow Engineering Data workbook. In the real-time power flow analysis, the date for which the solution is conducted will determine which set of seasonal limits is used; for example, if a date falls within the Winter season, all seasonal limits associated with Winter would be used in the analysis. While running power flow analysis in study mode, you have the option to choose whichever season you wish to use for the what if analysis.

One of the shortcomings of the seasonal method (versus the temperature based approach) is when there are areas in the network that experience different weather conditions. For example, some areas might be experiencing weather typical of summer while others areas are experiencing weather typical of fall; in this scenario, the analysis would use the season that includes the date despite the different conditions.

For temperature based limits, transformers and conductors can be grouped to the same set of Weather Zones that are used for driving Distributed Energy Resource forecasts. Each of these weather zones will have a temperature forecast that is provided via a real-time weather feed. Pre-defined limits will be provided in the Power Flow Engineering Data workbook for various temperature bands and the weather forecast will drive which of these is applied for the real-time loading and future forecasts. So, for example, the configuration may be set up such that conductors and transformers will have a limit defined for each 20°F range of temperature. The limit used for each power flow solution will be based on the forecast temperature for the date and time the solution is for and weather zone the device is in. Therefore, while looking at forecast power flow solutions for a device, it may be possible to see the upper limit changing as the temperature changes throughout the day. This is the one big differentiator between seasonal based limits and temperature based limits: with the temperature based limits, the limit used has the possibility to change hour by hour as temperature changes, whereas with seasonal limits, the same limit will be used for a larger date range.