What is the Difference Between Fault Current and Short Circuit Current?

what is the difference between fault current and short circuit current whatisdiffer

Failure to cut off power to the circuit before working on it might result in short circuits as well as fault current. The quantity of current that will flow when there is a short-circuit condition is referred to by the words short circuit and fault current.

The difference between fault current and short circuit current is that a short circuit has higher resistance than a fault current.

Let’s understand the basic difference between fault current and short circuit current below:

What is Fault Current?

what is fault current

The electrical current that passes through a circuit when an electrical defect is known as the fault current. When two or more electrical conductors short to one another or ground, a fault condition is produced.

A fault current often has a magnitude multiple times greater than the regular current that passes through the circuit when there isn’t a malfunction. 

It typically refers to a current flow that is more than what is generally estimated in an electrical circuit.

Example of Fault Current

For instance, your electrical supply breaker panel may contain a 20 amp circuit breaker. The circuit breaker trips if the current flow exceeds 20 amps. 

Given that the current flow surpassed the 20 amp limit, this is an error. It could also be overloaded if the circuit only receives 30 amps.

Signs of Fault Current

signs of fault current

The signs of fault current are:

1. A Buzzing Noise

The humming or buzzing sound that we typically associate with electricity may be familiar to you but in most circumstances, it can be a sign that something is wrong.

2. Smells

The first few times a new appliance is used, it may emit a weird new fragrance that you are not accustomed to; this is a symptom of a fault current.

Causes of Fault Current

The main causes of fault current are:

  • Switch surges that cause overvoltage.
  • Drastic lightning strikes.
  • Snowfall, rain, and strong winds.
  • Trees that have fallen on the transmission line.
  • Excessive pressures on the conductors from the inside and outside.
  • High atmospheric temperature variations.
  • Birds leaning back on the lines can cause fault current.
  • Chemical toxicity.

Avoidance from Fault Current

By using current and voltage transformers to identify the defect, the protective relays are designed to selectively isolate the malfunctioning component from the rest of the system by tripping the necessary number of circuit breakers.

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What is Short Circuit?

what is short circuit whatisdiffer

A short circuit occurs when two points in a circuit that have different voltage levels come into contact through an unexpected path with an extremely low or null resistance.

A short circuit happens when the insulation between live and line conductors contact one other.

When a “hot” wire and a “neutral” wire come into contact with one another, a short circuit happens. When this occurs, a lot of current flows, which can trip a circuit breaker or blow a fuse in addition to producing sparks and pop that is typically accompanied by some smoke.

Example of Short Circuit

Imagine a circuit where current is supposed to flow from a battery’s positive terminal to a wire attached to a bulb, then back to the battery’s negative terminal. 

However, if you directly connect the positive terminal to the negative terminal, you reduce the current route, and the battery bursts. We refer to this as short-circuiting.

Causes of Short Circuit

The leading cause of short circuits are:

  • Long-term overloading.
  • Machine jamming.
  • Loose joints are eroding insulation on wires and cables.
  • Failure or degradation of insulation; dirt, moisture, or dust on switches or terminations.
  • The unintentional dropping of conducting objects.
  • Poor maintenance; and, in rare cases, use of conductors or wires that need to be appropriately rated.

Signs of Short Circuits

signs of short circuits

1. Outlets Emitting a Burning Odor or Burn Marks

A short circuit may have occurred if the outlet exhibits burn marks or smells like something is burning. This frequently results from an overloaded circuit and could be dangerous for fire.

2. Sparks that the Circuit Emits

Sparks emerging from an outlet are another indication of an electrical short circuit. Sparks signify a potentially dangerously high current flow across the circuit.

Avoidance Techniques for an Electrical Short Circuit

  1. Avoid overloading any one plug or using many plugs at once because doing so could result in a fire or a short circuit.
  2. To prevent harm from high current flow, fuses are utilized. It consists of a metal strip or wire that melts when a strong current flows through it, interrupting the circuit.
  3. A circuit breaker is a piece of switching hardware that prevents an abnormal current flow in a circuit. It uses an internal system of springs to detect any changes in the current flow. The circuit will be “broken” open, and the current flow will be stopped.

Available Fault Current

The highest amount of current accessible during a fault is referred to as available fault current (AFC). The most current can be given to the electrical equipment while it is breaking. The short circuit current is another name for the available fault current. 

Difference Between Fault Current and Short Circuit Current

difference between fault current and short circuit current

The main difference between fault current and short circuit current is given below:

The primary difference between fault current and short circuit current is that a fault current has a resistance that drains current, whereas a short circuit has zero resistance between two wires.

Another difference between fault current and short circuit current is that a short circuit defect occurs when two conductors that are carrying current come into contact. 

However, a fault current occurs when one or more conductors contact an earthed body such as a machine’s frame. Any of these problems cause a strong inrush of current that feeds into the fault. To reduce/avoid damage, this fault current must be constrained.

A short circuit can cause a fault current, but the wire may still be able to supply current to the load due to its impedance. 

The protection mechanism is activated when the current is greater than the circuit breaker’s rating due to the load current plus the fault current.

Short Circuit vs. Ground Fault: What’s the Difference?

Highlighting the main difference between fault current and short circuit current in the following table:

Fault CurrentShort Circuit
Voltage in fault current can reach infinite levels, but the network’s defective point’s current is nil.When there is a short circuit, the voltage at the fault point drops to zero and abnormally high current flows via the network’s fault.
Resistance is high in fault current.Resistance is zero in the short circuit.
It happens when a live wire or neutral current breaks.It happens when the neutral and live wires come into contact.


The difference between fault current and short circuit current is that the fault current will be greater than the equipment’s current rating, for example, a motor rated at 14A. On the other hand, the maximum current that can run through a short-circuited piece of equipment and still allow it to function is known as the short circuit current.

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