What is Fault current: Definition and 12 Discussions

In an electric power system, a fault or fault current is any abnormal electric current. For example, a short circuit is a fault in which a Live wire touches a Neutral or Earth wire. An open-circuit fault occurs if a circuit is interrupted by cut on any of wires (Phase or Neutral) or blown Fuse. In three-phase systems, a fault may involve one or more phases and ground, or may occur only between phases. In a "ground fault" or "earth fault", current flows into the earth. The prospective short-circuit current of a predictable fault can be calculated for most situations. In power systems, protective devices can detect fault conditions and operate circuit breakers and other devices to limit the loss of service due to a failure.
In a polyphase system, a fault may affect all phases equally which is a "symmetric fault". If only some phases are affected, the resulting "asymmetric fault" becomes more complicated to analyse. The analysis of these types of faults is often simplified by using methods such as symmetrical components.
The design of systems to detect and interrupt power system faults is the main objective of power-system protection.

View More On Wikipedia.org
  1. T

    Maximum power from a transformer

    Hi, I was having a discussion with a colleague today now I'm second guessing myself. My understanding of nameplate kVA is that it is based on 'ambient temperature, temperature rise, heat transfer, thermal mass, thermal time constant, materials used, and expected transformer life'. However...
  2. U

    Help with magnetic force from fault current on overhead wire

    I'm trying to resolve an issue I'm experiencing with some overhead power distribution lines, was wondering if anyone can help me out. Here is the scenario: three phase, 4 wire, wye connected 13.4kV power distribution system. 556.5kcmil bare ACRS wire is mounted on a crossarm 24" apart over a...
  3. A

    Star/delta transformer - single phase fault on secondary

    Homework Statement A three-phase distribution transformer is configured as follows: -primary side = star with solidly grounded neutral -secondary side = delta, grounded via zigzag earthing transformer A single phase-earth fault occurs on the secondary (delta) side of the circuit...
  4. A

    Troubleshooting Fault Current Limiter Simulation in Ansoft Maxwell 14

    Hi, I'm trying to simulate a fault current limiter at ansoft maxwell 14 and i have a problem when i put the stranded option on winding, the current that appears is always positive, with the axis above zero. Anyone can answer me what's happening and how can i fix this? Some date: Transient...
  5. K

    Fault current time 1, 3 or 5 sec

    Any idea how can we decide on the fault current time 1, 3 or 5 sec. for grounding cable sizing? Also, what is the related temperature to the selected timing?
  6. H

    Three winding transformer fault current study

    Hello all! I am carrying out the theoretical (that is, by calculation means) unsymmetrical fault calculations for three winding transformer. It is to my understanding that for the zero sequence impedance for a three winding transformer depends on the winding connections of the generator and...
  7. C

    Can a second earthing conductor drive the fault current back?

    i have a TT earthing system and to decrease the resistance of the system I'm connecting the rods in parallel. i have the earthing conductor connected but as a mean of security, I'm thinking of connecting a second earthing conductor from the rod to the main Earth bar. Does this cause a any...
  8. D

    How can you accurately calculate fault current on a finite bus by hand?

    so calculating FC on an infinite bus is easy but how do you calculate it by hand for a finite bus? here is the concept i am having an issue understanding: let say i have a transformer that is 225KVA with 5%z and 3 phase 480 to 208. with infinite bus i have 12491A available on the...
  9. F

    Max Fault Current XFMR- quickly if possible

    Hi, I have a power systems protection assignment and I wanted to get some simple calcs verified. XFMR - 30MVA, 132kV:22kV; Star/Delta respectively. star neutral is floating, not that it matters for this part. reactance is 8% and resistance is 0.5% on the 30MVA base. Basically I am...
  10. K

    Circuit breaker, clearing a fault current

    hi could someone please explain the attached circuit to me in detail. From what i understand: the open circuit caused by the opened switch in series with the resistance causes a fault current in the system. This higher than normal current across the 200 ohm resistor causes a high...
  11. I_am_learning

    What is the fault current calculation for a broken line touching a pole?

    Last time I was talking about Isolated Voltage, and some of you people were really helping me about, but I posted (did) something stupid and got the thread deleted. I am sorry for that. Now, I want to talk about my confusion in a different (safe) way. The above figure shows a...
  12. S

    3 Phase System Line to Ground fault Fault current calculation

    Six, 6.6kV ,3phase, alternators are connected to a common set of bus bars. Each has positive negative and zero sequence reactances of 0.90 ohm, 0.72 ohm, 0.30 ohms respectively . An Earth fault occurs on one bus bar . Determine the value of fault current if all alternator neutrals are solidly...