What are the options available for breaker/switch close actions in RMS and EMT simulation?
In dynamic simulations, a breaker/switch can be closed via the Switch Event (EvtSwitch). The Switch Event can be parameterised in order to configure the closing process. Furthermore, the breaker itself may be modelled in detail via the available options within the Breaker Type (TypSwitch). For EMT-simulation type, the breaker close action can be further parameterised via the Scatter times (type parameters) - refer to below details. The switch event can be configured to close a given selection of the phases of a breaker e.g. if a three phase breaker is targeted, then either all, one or a combination of the phases can be configured for closing.
Within RMS-Simulation, the breaker closing is largely idealised/simplified: the momentary value of the voltage waveform on either of the phases cannot be observed within an RMS simulation, neither can the electro-magnetic transients created by the event. Therefore, the breaker closing occurs exactly at the moment of triggering the breaker close event. All poles that have been configured to close in the Switch Event will close immediately. If, for example, all three phases of a three phase circuit breaker have been configured to close, then they will close immediately - with no time delay in between. This is, surely, a simplification with respect to an actual closing of a three phase breaker. If, due to any reason, the closing sequence of the breaker poles needs to be simulated, then three individual switch events should be defined - one for each phase. In such a situation, an accurate representation of the positive/negative/zero sequence system can be obtained during the opening period of each phase within the breaker. Note, that an unbalanced RMS-simulation is required in order to represent unbalanced systems and events.
Within EMT-Simulation, the closing of the breaker poles can be done using the following options:
- Execution time (immediate application of close event on all targeted poles)
- Voltage zero crossing (triggering of close events on all/individual target poles at voltage zero crossing)
- Voltage threshold (triggering of close events on all/individual target poles at voltage threshold crossing)
- Voltage maximum (triggering of close events on all/individual target poles when reaching voltage maximum)
Furthermore, the individual phase scatter times can be selected in the EMT-Simulation page of the Breaker type which is assigned to the target breaker/switch (if any). The scatter times are relevant only in the event of a breaker closing and can be used to represent the difference between the breaker close command (per pole) and the actual closing of the breaker pole (as a delayed action, by “x” ms). By default, the scatter parameters for each phase/neutral are set to zero, meaning that no delay between the close command and close action exists.
Moreover, the Breaker/Switch can hold additional settings relevant for EMT simulation which may influence the behaviour of a close event:
- Non-linear characteristics for DC breakers (type parameters)
- Additional passive components of a detailed breaker (type parameters)