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Fault Current(LLF) Formula

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The fault current is the electrical current which flows through a circuit during an electrical fault condition. Check FAQs

I f = \frac{\sqrt{3} \cdot E a}{Z 1 + Z 2}

I_f - Fault Current?E_a - A Phase EMF?Z₁ - Positive Sequence Impedance?Z₂ - Negative Sequence Impedance?

Fault Current(LLF) Example

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Here is how the Fault Current(LLF) equation looks like with Values.

Here is how the Fault Current(LLF) equation looks like with Units.

Here is how the Fault Current(LLF) equation looks like.

-1.3881 = \frac{\sqrt{3} \cdot 29.38}{7.94 + -44.6}

-1.3881A = \frac{\sqrt{3} \cdot 29.38V}{7.94Ω + -44.6Ω}

-1.3881 = \frac{\sqrt{3} \cdot 29.38}{7.94 + -44.6}

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Fault Current(LLF) Solution

Follow our step by step solution on how to calculate Fault Current(LLF)?

FIRST Step Consider the formula

I f = \frac{\sqrt{3} \cdot E a}{Z 1 + Z 2}

Next Step Substitute values of Variables

∴

I f = \frac{\sqrt{3} \cdot 29.38V}{7.94Ω + -44.6Ω}

Next Step Prepare to Evaluate

∴

I f = \frac{\sqrt{3} \cdot 29.38}{7.94 + -44.6}

Next Step Evaluate

∴

I f = -1.38809745571123A

LAST Step Rounding Answer

∴

I f = -1.3881A

Fault Current(LLF) Formula Elements

Variables

Functions

Fault Current

The fault current is the electrical current which flows through a circuit during an electrical fault condition.

Symbol: I_f

Measurement: Electric CurrentUnit: A

Note: Value can be positive or negative.

Formulas to find Fault Current

A Phase EMF

A phase EMF is defined as the electromagnetic force of the a-phase in open conductor fault.

Symbol: E_a

Measurement: Electric PotentialUnit: V

Note: Value can be positive or negative.

Formulas to find A Phase EMF

Positive Sequence Impedance

Positive Sequence Impedance consists of balanced three-phase voltage and current phasors which are exactly at 120 degrees apart rotating counterclockwise in ABC rotation.

Symbol: Z₁

Measurement: Electric ResistanceUnit: Ω

Note: Value should be greater than 0.

Formulas to find Positive Sequence Impedance

Negative Sequence Impedance

Negative Sequence Impedance consists of balanced three-phase impedance phasors which are exactly at 120 degrees apart rotating counterclockwise in ACB rotation.

Symbol: Z₂

Measurement: Electric ResistanceUnit: Ω

Note: Value can be positive or negative.

Formulas to find Negative Sequence Impedance

sqrt

A square root function is a function that takes a non-negative number as an input and returns the square root of the given input number.

Syntax: sqrt(Number)

Other formulas in Current category

Go B-Phase Current (LLF)

I b = (- 1) \cdot I c

Go C-Phase Current(LLF)

I c = (- 1) \cdot I b

Go Positive Sequence Current (LLF)

I 1 = (- 1) \cdot I 2

Go Negative Sequence Current(LLF)

I 2 = (- 1) \cdot I 1

How to Evaluate Fault Current(LLF)?

Fault Current(LLF) evaluator uses Fault Current = (sqrt(3)*A Phase EMF)/(Positive Sequence Impedance+Negative Sequence Impedance) to evaluate the Fault Current, The Fault Current(LLF) formula is defined as the high level of electrical current that flows in a power system when a fault occurs. Fault Current is denoted by I_f symbol.

How to evaluate Fault Current(LLF) using this online evaluator? To use this online evaluator for Fault Current(LLF), enter A Phase EMF (E_a), Positive Sequence Impedance (Z₁) & Negative Sequence Impedance (Z₂) and hit the calculate button.

FAQs on Fault Current(LLF)

What is the formula to find Fault Current(LLF)?

The formula of Fault Current(LLF) is expressed as Fault Current = (sqrt(3)*A Phase EMF)/(Positive Sequence Impedance+Negative Sequence Impedance). Here is an example- 0.968551 = (sqrt(3)*29.38)/(7.94+(-44.6)).

How to calculate Fault Current(LLF)?

With A Phase EMF (E_a), Positive Sequence Impedance (Z₁) & Negative Sequence Impedance (Z₂) we can find Fault Current(LLF) using the formula - Fault Current = (sqrt(3)*A Phase EMF)/(Positive Sequence Impedance+Negative Sequence Impedance). This formula also uses Square Root (sqrt) function(s).

Can the Fault Current(LLF) be negative?

Yes, the Fault Current(LLF), measured in Electric Current can be negative.

Which unit is used to measure Fault Current(LLF)?

Fault Current(LLF) is usually measured using the Ampere[A] for Electric Current. Milliampere[A], Microampere[A], Centiampere[A] are the few other units in which Fault Current(LLF) can be measured.

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Fault Current(LLF) Formula

Fault Current(LLF) Example

Fault Current(LLF) Solution

Fault Current(LLF) Formula Elements

Other formulas in Current category

How to Evaluate Fault Current(LLF)?

FAQs on Fault Current(LLF)

Variable Name