Switch and Breaker.

In Caspoc power systems library there are several switches, breakers and a three phase fault modeled. The breakers single and three phase are displayed below in the first row. The breakers open only after the first zero crossing of the current through them, thus enabling a soft turn off.

The switches are available as single phase and three phase, where in the seperate control three phase model each switch can also be controlled individually. The switches are displayed in the second row in the figure below.

A three phase fault is modeled in a single block where the inter-phase faults as well as grounding faults can be simulated. The fault is shwon in the last row in the figure below.

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Switches

The Switch block does not correspond to a particular physical device. When used with appropriate switching logic, it can be used to model a simplified semiconductor devices such as a GTO or a MOSFET, or even a power circuit breaker with current chopping. The switch is simulated as a resistor Ron in series with a switch controlled by a logical gate signal Gate.

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The Ideal Switch block is fully controlled by the gate signal(Gate > 0 or Gate = 0). It has the following characteristics:

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The Ideal Switch block turns on when a positive signal is present at the gate input (Gate > 0). It turns off when the gate signal equals 0 (Gate = 0).

The Ideal Switch block also contains no snubber circuit. It can be modeled in parallel with the ideal switch by inserting circuit compoents like R, L, C and diode selected from the components/circuit.

Parameters switch

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On resistance Ron The on resistance of the switch device, in ohms (Ω). The Internal resistance Ron parameter cannot be set to 0. Off resistance Roff The off resistance of the switch device, in ohms (Ω). The off resistance Roff parameter cannot be set to 0.

Control Inputs

Control signal Gate to control the opening and closing of the switch. Connect this input to a control output from the block diagram.

Assumptions and Limitations

The Ideal Switch block is modeled as a resistor that has either a high value (Roff) or a low value (Ron). It can be connected in series with an inductor, a current source, or an open circuit, even without a snubber circuit.


Breaker

The breaker block is a circuit breaker which is opening at current zero crossing. The Breaker block implements a circuit breaker where the opening and closing is controlled by an external control signal.

The arc extinction process is simulated by opening the breaker device when the current passes through zero (first current zero-crossing following the transition of the control input from 1 to 0).

When the breaker is closed it behaves as a resistive circuit. It is represented by a resistance Ron. The Ron value can be set as small as necessary in order to be negligible compared with external components (typical value is 10m). When the breaker is open it has a high resistance, default set to 1e6 ohm.

The Breaker block is controlled from a control input. The control signal connected to this second input must be either 0 or 1, 0 to open the breaker, 1 to close it.

A series Rs-Cs snubber circuit is not included in the model. It can be optionally connected to the circuit breaker.

Breaker Parameters

<br>Click to close the image On resistance Ron The on resistance of the breaker device, in ohms (Ω). The Internal resistance Ron parameter cannot be set to 0. Off resistance Roff The off resistance of the breaker device, in ohms (Ω). The off resistance Roff parameter cannot be set to 0.

Faults

The Three-Phase Fault block implements a three-phase circuit breaker where the opening and closing is controlled from an external control signal.

The Three-Phase Fault block uses three Breaker blocks that can be individually switched on and off to program phase-to-phase faults, phase-to-ground faults, or a combination of phase-to-phase and ground faults. <br>Click to close the image

The control signals connected to the bottom inputs control the turn on and turn off of the switches in the fault. The control signals must be either 0 or 1, 0 to open the breakers, 1 to close them.

Fault Parameters

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Fault resistances Rfault The internal fault resistance, in ohms, of the phase fault breakers. The fault resistances Rfault parameter cannot be set to 0. Fault switch on resistances Ron The internal switch on resistance, in ohms, of the phase fault breakers. The fault switch resistances Ron parameter cannot be set to 0. Fault switch off resistances Roff The internal switch off resistance, in ohms, of the phase fault breakers. The fault switch resistances Roff parameter cannot be set to 0. Ground resistance Rg The ground resistance, in ohms. The Ground resistance Rg (ohms) parameter cannot be set to 0.

Fault Inputs

Phase A Fault

If the first input is >0 , the fault switching of phase A is activated. If the input is <0 , the switch of phase A stays in its off status. The initial status of the phase A switch is directly defined by the value of the controlling input. Phase B Fault If the second input is >0 , the fault switching of phase B is activated. If the input is <0 , the switch of phase B stays in its off status. The initial status of the phase B switch is directly defined by the value of the controlling input. Phase C Fault If the third input is >0 , the fault switching of phase C is activated. If the input is <0 , the switch of phase C stays in its off status. The initial status of the phase C switch is directly defined by the value of the controlling input. Ground Fault If the ground resistance has alow value, the fault switching to the ground is activated. A fault to the ground can be programed for the activated phases. For example, if the Phase C Fault input is high and the Ground Fault resistance has a low value, a fault to the ground is applied to phase C. The ground resistance is set internally to 1e6 ohms when the Ground Fault parameter is not selected.

Note!

Please note that using the switch model and single resistors from components/circuit, any fault combination can be created. The here presented fault block merely services as a simple and easy to use block.

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