# Fault (Three-Phase)

Signal-enabled or time-based, single-phase, two-phase, or three-phase, grounded or ungrounded fault

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• Simscape / Electrical / Utilities

## Description

The Fault (Three-Phase) models any permutation of a single-phase, two-phase, or three-phase grounded or ungrounded fault. The block can impose both time- and event-based faults. The block can impose one or both type of faults, consecutively, at the same time, or for an overlapping time period.

For a time-based or temporal fault, specify the fault activation time using the block Fault start time parameter. The fault becomes inactive when the fault duration that you specify elapses.

For an event-based fault, specify the fault activation threshold using the block Threshold parameter. An external control signal F enables the fault. The fault is active when F is greater than the threshold. The fault is inactive when F is less than or equal to the threshold.

The block can represent these permutations:

• Single-phase-to-ground fault (a-g, b-g, or c-g)

• Two-phase fault (a-b, b-c, or c-a)

• Two-phase-to-ground fault (a-b-g, b-c-g, or c-a-g)

• Three-phase fault (a-b-c)

• Three-phase-to-ground fault (a-b-c-g)

The figure shows the equivalent circuit diagram for the block.

To determine the resistance in the equivalent circuit, apply the relevant equations from the table.

Fault Type Value of R a Value of R b Value of R c Value of R g

None / inactive

$\frac{1}{{G}_{pn}}$ $\frac{1}{{G}_{pn}}$ $\frac{1}{{G}_{pn}}$

Infinity / open circuit

Single phase to ground

a-g

${R}_{pn}$ $\frac{1}{{G}_{pn}}$ $\frac{1}{{G}_{pn}}$ ${R}_{ng}$

b-g

$\frac{1}{{G}_{pn}}$ ${R}_{pn}$ $\frac{1}{{G}_{pn}}$ ${R}_{ng}$

c-g

$\frac{1}{{G}_{pn}}$ $\frac{1}{{G}_{pn}}$ ${R}_{pn}$ ${R}_{ng}$
Two phase

a-b

${R}_{pn}$ ${R}_{pn}$ $\frac{1}{{G}_{pn}}$

Infinity / open circuit

b-c

$\frac{1}{{G}_{pn}}$ ${R}_{pn}$ ${R}_{pn}$

Infinity / open circuit

c-a

${R}_{pn}$ $\frac{1}{{G}_{pn}}$ ${R}_{pn}$

Infinity / open circuit

Two phase to ground

a-b-g

${R}_{pn}$ ${R}_{pn}$ $\frac{1}{{G}_{pn}}$ ${R}_{ng}$

b-c-g

$\frac{1}{{G}_{pn}}$ ${R}_{pn}$ ${R}_{pn}$ ${R}_{ng}$

c-a-g

${R}_{pn}$ $\frac{1}{{G}_{pn}}$ ${R}_{pn}$ ${R}_{ng}$
Three phase

a-b-c

${R}_{pn}$ ${R}_{pn}$ ${R}_{pn}$

Infinity / open circuit

Three phase to ground

a-b-c-g

${R}_{pn}$ ${R}_{pn}$ ${R}_{pn}$ ${R}_{ng}$

where:

• Ra is the resistance between the a-phase and the neutral point of a wye connection.

• Rb is the resistance between the b-phase and the neutral point of a wye connection.

• Rc is the resistance between the c-phase and the neutral point of a wye connection.

• Rg is the resistance between the neutral point of a wye connection and electrical reference.

• Rpn is the value of the Faulted phase-neutral resistance parameter.

• Rng is the value of the Faulted neutral-ground resistance parameter.

• Gpn is the value of the Unfaulted phase-neutral conductance parameter.

## Ports

### Conserving

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Expandable electrical conserving three-phase port for connecting the fault to the system.

### Input

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Physical signal scalar control input port for enabling an externally triggered fault.

#### Dependencies

To enable this port, on the External Trigger settings, set the Enable external fault trigger parameter to Yes.

### Output

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Physical signal scalar output port for reporting the fault state:

• 1 — Faulted

• 0 — Unfaulted

#### Dependencies

To enable this port, on the Main settings, set the State port parameter to Visible.

## Parameters

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### Main

Type of fault to model. The visibility of related parameters depends on the fault model. Options are:

• None — Specifies that the fault is not active.

• Single-phase to ground (a-g)

• Single-phase to ground (b-g)

• Single-phase to ground (c-g)

• Two-phase (a-b)

• Two-phase (b-c)

• Two-phase (c-a)

• Two-phase to ground (a-b-g)

• Two-phase to ground (b-c-g)

• Two-phase to ground (c-a-g)

• Three-phase (a-b-c)

• Three-phase to ground (a-b-c-g)

Resistance between the phase connection and the neutral point when the fault is active.

#### Dependencies

To enable this parameter set the Fault type parameter to:

• Single-phase to ground (a-g)

• Single-phase to ground (b-g)

• Single-phase to ground (c-g)

• Two-phase (a-b)

• Two-phase (b-c)

• Two-phase (c-a)

• Two-phase to ground (a-b-g)

• Two-phase to ground (b-c-g)

• Two-phase to ground (c-a-g)

• Three-phase (a-b-c)

• Three-phase to ground (a-b-c-g)

Resistance between the neutral point and the electrical reference when fault is active.

#### Dependencies

To enable this parameter set the Fault type parameter to:

• Single-phase to ground (a-g)

• Single-phase to ground (b-g)

• Single-phase to ground (c-g)

• Two-phase to ground (a-b-g)

• Two-phase to ground (b-c-g)

• Two-phase to ground (c-a-g)

• Three-phase to ground (a-b-c-g)

Option to hide or expose port x, a physical signal output port that reports the fault state:

• Hidden — Port x is not visible if you select this option.

• Visible — Port x is visible only if you select this option.

### External Trigger

External fault model. Choose between

• No — Do not model an external fault. Physical signal input port F is not visible if you select this option.

• Yes — Model an external fault. Related parameters and physical signal input port F are visible only if you select this option.

The threshold value that triggers the fault when the external signal crosses it in the direction, specified by the fault condition. This parameter is visible only if the Enable external fault trigger parameter is set to Yes. The default value is 0.5.

#### Dependencies

To enable this parameter, set the Enable external fault trigger parameter to Yes.

Choose the fault condition:

• Faulted if F >= Fault threshold — The fault occurs when the external signal value becomes greater than, or equal to, the Fault threshold parameter value.

• Faulted if F <= Fault threshold — The fault occurs when the external signal value becomes less than, or equal to, the Fault threshold parameter value.

#### Dependencies

To enable this parameter, set the Enable external fault trigger parameter to Yes.

Select Yes to have the fault reset when the trigger signal reverts. The default value is No.

#### Dependencies

To enable this parameter, set the Enable external fault trigger parameter to Yes.

### Temporal Trigger

Temporal fault model. Choose between

• No — Do not model a temporal fault.

• Yes — Model a temporal fault. Related parameters are visible only if you select this option.

Simulation time that the block enters the fault state.

#### Dependencies

To enable this parameter, set the Enable temporal fault trigger parameter to Yes.

Simulation duration time for the fault. The block exits the fault state when the duration time is over.

#### Dependencies

To enable this parameter, set the Enable temporal fault trigger parameter to Yes.

### Parasitics

Conductance between the phase connections and the neutral point when a phase is not involved in the fault.