Three-Phase Breaker

Implement three-phase circuit breaker opening at current zero crossing

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Description

The Three-Phase Breaker block implements a three-phase circuit breaker where the opening and closing times can be controlled either from an external Simulink^® signal (external control mode), or from an internal control timer (internal control mode).

The Three-Phase Breaker block uses three Breaker blocks connected between the inputs and the outputs of the block. You can use this block in series with the three-phase element you want to switch. The arc extinction process of the Three-Phase Fault block is the same as for the Breaker block. See the Breaker block reference pages for details on the modeling of the single-phase breakers.

If the Three-Phase Breaker block is set in external control mode, a control input appears in the block icon. The control signal connected to the Simulink input must be either 0, which opens the breakers, or any positive value, which closes the breakers. For clarity, a 1 signal is commonly used to close the breakers. If the Three-Phase Breaker block is set in internal control mode, the switching times are specified in the dialog box of the block. The three individual breakers are controlled with the same signal.

Series Rs-Cs snubber circuit are included in the model. They can be optionally connected to the three individual breakers. If the Three-Phase Breaker block happens to be in series with an inductive circuit, an open circuit or a current source, you must use the snubbers.

Parameters

Initial status

The initial status of the breakers. The initial status is the same for the three breakers. Depending on the initial status, the icon shows a closed contact or an open contact. Choices are open (default) or closed.

Switching of: Phase A

If selected, the switching of phase A is activated. If not selected, the breaker of phase A stays in its initial status specified in the Initial status parameter. Default is selected.

Switching of: Phase B

If selected, the switching of phase B is activated. If not selected, the breaker of phase B stays in its initial status specified in the Initial status parameter. Default is selected.

Switching of: Phase C

If selected, the switching of phase C is activated. If not selected, the breaker of phase C stays in its initial status specified in the Initial status parameter. Default is selected.

Switching times (s)

This parameter is available only if the External check box is cleared.

Specify the vector of switching times when using the Three-Phase Breaker block in internal control mode. At each transition time the selected breakers opens or closes depending to their initial state. Default is [1/60 5/60].

External

If selected, adds a fourth input port to the Three-Phase Breaker block for an external control of the switching times of the breakers. The switching times are defined by a Simulink signal (0-1 sequence). Default is cleared.

Breakers resistance Ron

The internal breaker resistances, in ohms (Ω). The Breaker resistance Ron parameter cannot be set to 0. Default is 0.01.

Snubbers resistance Rs

The snubber resistances, in ohms (Ω). Set this parameter to inf to eliminate the snubbers from the model. Default is 1e6.

Snubbers capacitance Cs

The snubber capacitances, in farads (F). Set this parameter to 0 to eliminate the snubbers, or to inf to get resistive snubbers. Default is inf.

Measurements

Select Breaker voltages to measure the voltage across the three internal breaker terminals.

Select Breaker currents to measure the current flowing through the three internal breakers. If the snubber devices are connected, the measured currents are the ones flowing through the breakers contacts only.

Select Breaker voltages and currents to measure the breaker voltages and the breaker currents.

Default is None.

Place a Multimeter block in your model to display the selected measurements during the simulation. In the Available Measurements list box of the Multimeter block, the measurements is identified by a label followed by the block name and the phase:

Measurement	Label
Breaker voltages	`Ub <block_name> /Breaker A:`
Breaker currents	`Ib <block_name> /Breaker A:`

Inputs and Outputs

If the Three-Phase Breaker block is set in external control mode, a Simulink input is added to the block to control the opening and closing of the three internal breakers.