Symmetric fault

Symmetric fault

In power engineering, specifically three-phase power, a symmetric, symmetrical or balanced fault is a fault which affects each of the three-phases equally. In transmission line faults, roughly 5% are symmetric. This is in contrast to an asymmetric fault, where the three phases are not affected equally. In practice, most faults in power systems are unbalanced. With this in mind, symmetric faults can be viewed as somewhat of an abstraction; however, as asymmetric faults are difficult to analyze, analysis of asymmetric faults is built up from a thorough understanding of symmetric faults.


Symmetric faults can be analyzed via the same methods as any other phenomena in power systems, and in fact many software tools exist to accomplish this type of analysis automatically (see power flow study). However, there is another method which is as accurate and is usually more instructive.

First, some simplifying assumptions are made. It is assumed that all electrical generators in the system are in phase, and operating at the nominal voltage of the system. Electric motors can also be considered to be generators, because when a fault occurs, they usually supply rather than draw power. The voltages and currents are then calculated for this "base case".

Next, the location of the fault is considered to be supplied with a negative voltage source, equal to the voltage at that location in the base case, while all other sources are set to zero. This method makes use of the principle of superposition.

To obtain a more accurate result, these calculations should be performed separately for three separate time ranges:
* "subtransient" is first, and is associated with the largest currents
* "transient" comes between subtransient and steady-state
* "steady-state" occurs after all the transients have had time to settle

See also

* Asymmetric fault

Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Fault — may refer to:*Fault (geology), planar rock fractures which show evidence of relative movement *Fault (technology), an abnormal condition or defect at the component, equipment, or sub system level which may lead to a failure *An asymmetric fault… …   Wikipedia

  • Fault (technology) — In document ISO/CD 10303 226, a fault is defined as an abnormal condition or defect at the component, equipment, or sub system level which may lead to a failure. According to the Federal Standard 1037C of the United States, the term fault has the …   Wikipedia

  • Asymmetric fault — In power engineering, specifically three phase power, an asymmetric or unbalanced fault is a fault which does not affect each of the three phases equally. This is in contrast to a symmetric fault, where each of the phases is affected equally. In… …   Wikipedia

  • Differential fault analysis — is a type of side channel attack in the field of cryptography, specifically cryptanalysis. The principle is to induce faults unexpected environmental conditions into cryptographic implementations, to reveal their internal states. For example, a… …   Wikipedia

  • SFT — Students for a Free Tibet (Academic & Science » Universities) ** System Fault Tolerance (Computing » General) * System File Table (Computing » Networking) * Seal Forward Technology (Business » General) * Simon Fisher Turner (Community » Famous) * …   Abbreviations dictionary

  • Detachment fold — A detachment fold occurs as layer parallel thrusting along a detachment fault develops without upward propagation of a fault; the accommodation of the strain produced by thrusting results in the folding of the overlying rock units. As a visual… …   Wikipedia

  • List of file systems — The following lists identify, characterize and link to more thorough information on computer file systems.Many older operating systems support only their one native file system, which does not bear any name apart from the name of the operating… …   Wikipedia

  • Windows 2000 — Part of the Microsoft Windows family Screenshot of Windows 2000 Professional …   Wikipedia

  • Хандшух, Хелен — Хелен Хандшух (англ. Helena Handschuh)  криптограф. Наиболее известная разработка  симметричный блочный криптоалгоритм SHACAL. Помимо этого принимала участие в создании блочного шифра Universal Encryption Standard. С 2009 года… …   Википедия

  • Storage virtualization — refers to the process of abstracting logical storage from physical storage. The term is today used to describe this abstraction at any layer in the storage software and hardware stack.Key conceptsAddress space remappingVirtualization of storage… …   Wikipedia