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# Enabled Fault

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

## Library

Passive Devices / Faults

## Description

The Enabled Fault models any permutation of a single-phase, two-phase, or three-phase grounded or ungrounded fault. You specify the fault activation threshold using the block Threshold parameter. An external control signal en enables the fault. The fault is active when en is greater than the threshold. The fault is inactive when en is less than or equal to the threshold.

You can set the Enabled Fault block to represent any of these:

• 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 Enabed Fault block.

You can determine the resistance in the equivalent circuit using the equations in the table.

Fault typeValue of RaValue of RbValue of RcValue of Rg

None / inactive

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

Infinity / open circuit

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}$

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

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}$

a-b-c

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

Infinity / open circuit

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.

## Dialog Box and Parameters

### Main Tab

Fault type

Select one of the following:

• None — Specifies that the fault is not active. This is the default value.

• 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)

Faulted phase-neutral resistance

Resistance between the phase connection and the neutral point when the fault is active. This parameter is visible if the Fault type parameter is set to anything other than None. The default value is 1e-3 Ω.

Faulted neutral-ground resistance

Resistance between the neutral point and the electrical reference when fault is active. This parameter is visible if the Fault type parameter is set to any fault which includes a ground connection. The default value is 1e-3 Ω.

Threshold

Threshold for activating the fault. If the input en is above the value for the Threshold parameter, then the fault is active. If the input en is equal to or less than the value for the Threshold parameter, then the fault is not active. This parameter is visible if the Fault type parameter is set to anything other than None. The default value is 0.

### Parasitics Tab

Unfaulted phase-neutral conductance

Conductance between the phase connections and the neutral point when a phase is not involved in the fault. The default value is 1e-6 Ω-1.

## Ports

The block has the following ports:

~

Expandable three-phase port for connecting the fault to the system

en

Physical signal scalar control input port for enabling the fault