Contactor Model

The contactor model supplied with the Dynamic Stability Engine performs in a simplistic manner with only two data items needed (under-voltage threshold and time to trip). The contactor simply responds to an under-voltage condition, and if subjected to a level below the under-voltage threshold for the time to trip, will cause the switching device it is associated with to switch open in the simulation.

Contactors can be found within fused switch and low voltage breaker equipment dialog boxes, under the Stability tab. They are both enabled and specified in that tab.

You must own EasyPower Power Protector to have the contactor model feature in the Dynamic Stability Engine.

Here are a few more application notes regarding contactors:

• If the switching device a contactor is associated with is already open, and the contactor says to open, then no action is taken.
• Contactors will auto-trip off at the beginning of a simulation where the contactor is located in an isolated (and thus disconnected) part of your system. The model is responding to its initial voltage being zero, which is below its trip threshold. Since the initial power flow represents steady-state, then by definition these contactors must be off.
• Care must be taken to make sure that a protective upstream device is included in your simulation when using a contactor that is exposed to a fault current condition. If this is not done, then a contactor (sensing an under-voltage condition from a fault on its load side), will interrupt the fault. In the simulation, this will happen cleanly, and without mishap. However in real life, due to contactors not being rated to interrupt SC current, the contactor would most likely explode into a mass of molten metal.
• If the voltage at the contactor goes above the under-voltage threshold before the time to trip is satisfied, the contactor will perform an instantaneous reset.

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