.Dynawo.Examples.IEEE14.TestCases.IEEE14CLA

The purpose of the current limit automatons is to disconnect the monitored component when the current is higher than a predefined threshold during a certain amount of time.

For LineB1B2 and LineB2B5, the current is now higher than IMax. The controller CLAB2B5 will react after tLagBeforeActing = 20 s to disconnect the LineB2B5 before any reaction from the controller CLAB1B2 that has a tLagBeforeActing = 30 s.

The disconnection of Lineb2B5 decreases the current on LineB1B2 which is now below IMax = 1.55 pu. The current of LineB1B5 stays below IMax = 2 pu.

The final steady state is reached after the restoration of the loads.

Another scenario will occur if we change tLagBeforeActing for CLAB1B2 to 20 s and tLagBeforeActing for CLAB2B5 to 30 s.

After the increase of Load5.PRefPu, the current will increase on all the lines. However, here CLAB1B2 will react after 20 s before CLAB2B5 to disconnect LineB1B2.

The current of LineB2B5 is now below IMax but the current of LineB1B5 increases and it is now higher than IMax = 2 pu. 

CLAB1B5 will react after 50s, at t = 120 s to disconnect LineB1B5. This event disconnects generator 1 and all the generated power now comes from generator 2. The simulation fails and stops at t = 120s.

These two scenarios show that a time-domain approach for steady-state calculation gives results closer to system's behavior that can not be described with a static load flow. It is important to consider the dynamics of the system that can influence the final steady-state result.