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 Fault and Phase B Fault block parameters only. To program a fault between the phase A and the ground, you need to select the Phase A Fault and Ground Fault 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 Rp-Cp 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

Phase A Fault

If selected, the fault switching of phase A is activated. If not selected, the breaker of phase A stays in its initial status. The initial status of the phase A breaker corresponds to the complement of the first value specified in the vector of Transition status. The initial status of the fault breaker is usually 0 (open). However, it is possible to start a simulation in steady state with the fault initially applied on the system. For example, if the first value in the Transition status vector is 0, the phase A breaker is initially closed. It opens at the first time specified in the Transition time(s) vector.

Phase B Fault

If selected, the fault switching of phase B is activated. If not selected, the breaker of phase B stays in its initial status. The initial status of the phase B breaker corresponds to the complement of the first value specified in the vector of Transition status.

Phase C Fault

If selected, the fault switching of phase C is activated. If not selected, the breaker of phase C stays in its initial status. The initial status of the phase C breaker corresponds to the complement of the first value specified in the vector of Transition status.

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 Fault

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 Fault and Ground Fault 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 Fault parameter is not selected.

Ground resistance Rg

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

External control of fault timing

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.

Transition status

Specify the vector of switching status when using the Three-Phase Breaker block in internal control mode. The selected fault breakers open (0) or close (1) at each transition time according to the Transition status parameter values.

The initial status of the breakers corresponds to the complement of the first value specified in the vector of switching status.

Transition 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 state. The Transition times (s) parameter is not visible in the dialog box if the External control of switching times parameter is selected.

Snubbers resistance Rp

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

Snubbers capacitance Cp

The snubber capacitances, in farads (F). Set the Snubbers capacitance Cp 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_3phseriescomp demo for a circuit using the Three-Phase Fault block.