Load Group Models

In many cases, load characteristic model are created to allocate the behavior of a load between various components (static model and or dynamic models) by percentage. For example, the model MOTORW model allocates a percentage of various loads to a dynamic motor model while the remaining portion of the load remain a static model. In many cases, there may be 100s or 1000s of loads for which you want to use the same load model.

To handle this, Simulator's Transient Stability tool has always allowed you to assign load models to an aggregation object such as the entire system, an Area, a Zone, an Owner, or a Bus to make this data management easier. However, frequently the load behavior does not break down in the system based on the definitions of Areas, Zones, Owners, or Buses. In order to make the assignment of load model easier to manage, a new aggregation object called a Load Model Group may be created.

A Load Model Group is a very simple object which essentially has only a Name and then a list of various Load Characteristic Models (such as MOTORW, WSCC, IEEL, CMPLDW_NF, etc.) assigned to it in the same way that load characteristics are assign to an Area, Zone, etc. A Load Model Group may represent the behavior of "High Desert" loads or "Coastal Loads" for example.

Once Load Model Groups are created, then each Load Record may optionally be assigned to a specific Load Model Group. When determining which Transient Stability Model to use for a particular load, the following logic is applied. This general hierarchy has always existed in Simulator, with only the Load Model Group part newly added.

• If a load-specific model exist, this will be used
• Else if the Load is assigned to a Load Model Group which has a model, this will be used
• Else if a bus-specific model exists at the terminal bus, this will be used
• Else if an owner-specific model exists for the load's owner, this will be used
• Else if an zone-specific model exists for the load's zone, this will be used
• Else if an area-specific model exists for the area's zone, this will be used
• Else if an system-specific model exists for the power system, this will be used
• Else the Load Modeling option specified on the Transient Stability Dialog's Option\Power System Model section will be used. (For relays the default will be to not use a relay model at all)

Load Model Groups are now included in the hierarchy of Load Characteristics in the Model Explorer as depicted in the following image.