Autotransformer Module

The Autotransformer Module in SARA enables engineers to apply their protection philosophy to set relay settings for relays on both the high side and low side of transformers. Similar to the T-Line module, the user can create a template containing fault information, variables, equations, and study parameters before applying the template to their short-circuit model.

 

Creating a Relay Settings Template (.stl) and Relay Settings Template Application sections contain the complete details for defining and applying a template in SARA – the following section will focus only on the aspects that are unique to the Autotransformer module.

 

Fault Studies are specified in terms of High Side, Low Side, and Tertiary Side for the Fault and Current Location(s)

 

 

Protection Equations may include the following dictionary variables – unique to the Autotransformer module:

• MVA1
• MVA2
• MVA3
• HighSideKV
• LowSideKV
• TertiaryKV

 

Note that these values will be automatically calculated and shown on the Calculated Variables tab on run-time.

 

 

Settings Calibration

The Settings Calibration tab displays the Time Overcurrent curves for each of the winding elements defined in the template. The user must define the pickup setting, time dial, and curve for the chart to appear. The curves are responsive and update if the user overrides the values in the settings cards.

 

 

Coordination Time Intervals

 

 

The Coordination Time Intervals tab in the Autotransformer tab displays the time overcurrent charts for the primary and backup relays. The left chart represents the high side of the transformer, and the chart on the right represents the low side. Additional overcurrent curves may be added by selecting the blue box representing the relay on the visual and then the graph icon, or by checking the relay in the Plot Relays selection box on the right side.

 

 

Time and current data is shown for each Relay and Element. Selecting the arrows will toggle through each fault and contingency.