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Three-Phase Fault

Implement programmable phase-to-phase and phase-to-ground fault breaker system

Library

Elements

Description

The Three-Phase Fault 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 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.

The ground resistance Rg is automatically set to 106 ohms when the ground fault option is not programmed. For example, to program a fault between the phases A and B you need to select the Phase A and Phase B block parameters only. To program a fault between the phase A and the ground, you need to select the Phase A and Ground parameters and specify a small value for the ground resistance.

If the Three-Phase Fault block is set in external control mode, a control input appears in the block icon. The control signal connected to the fourth input must be either 0 or 1, 0 to open the breakers, 1 to close them. If the Three-Phase Fault block is set in internal control mode, the switching times and status are specified in the dialog box of the block.

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

Dialog Box and Parameters

Initial status

The initial status of the fault breaker is usually 0 (open). However, you can start the simulation in steady state with the fault initially applied on the system.

Phase A

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

Phase B

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

Phase C

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

Ground

If selected, 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 and Ground parameters are selected, a fault to the ground is applied to the phase C. The ground resistance is set internally to 1e6 ohms when the Ground parameter is not selected.

Switching times (s)

Specify the vector of switching times when using the Three-Phase Breaker block in internal control mode. At each transition time the selected fault breakers opens or closes depending to the initial status. The Switching times (s) parameter is not available if the External parameter is selected.

External

If selected, adds a fourth input port to the Three-Phase Fault block for an external control of the switching times of the fault breakers. The switching times are defined by a Simulink signal (0 or 1) connected to the fourth input port of the block.

Fault resistances Ron

The internal resistance, in ohms (Ω), of the phase fault breakers. The Fault resistances Ron parameter cannot be set to 0.

Ground resistance Rg

The Ground resistance Rg parameter is available only if the Ground parameter is selected. The ground resistance, in ohms (Ω). The Ground resistance Rg parameter cannot be set to 0.

Snubbers resistance Rs

The snubber resistances, in ohms (Ω). Set the Snubbers resistance Rs parameter to inf to eliminate the snubbers from the model.

Snubbers capacitance Cs

The snubber capacitances, in farads (F). Set the Snubbers capacitance Cs parameter to 0 to eliminate the snubbers, or to inf to get resistive snubbers.

Measurements

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

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

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 are identified by a label followed by the block name and the phase:

Measurement

Label

Fault voltages

Ub <block name> /Fault A: Ub <block name> /Fault B: Ub <block name> /Fault C.

Fault currents

Ib <block name> /Fault A: Ib <block name> /Fault B: Ib <block name> /Fault C.

Inputs and Outputs

The three fault breakers are connected in wye between terminals A, B and C and the internal ground resistor. If the Three-Phase Fault block is set to external control mode, a Simulink input is added to the block to control the opening and closing of the three internal breakers.

Example

See the power_3phseriescomppower_3phseriescomp example for a circuit using the Three-Phase Fault block.

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