Ferroresonance or nonlinear resonance is a type of
resonance
Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied periodic force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscillatin ...
in
electric circuits which occurs when a circuit containing a nonlinear
inductance
Inductance is the tendency of an electrical conductor to oppose a change in the electric current flowing through it. The flow of electric current creates a magnetic field around the conductor. The field strength depends on the magnitude of the ...
is fed from a source that has series
capacitance
Capacitance is the capability of a material object or device to store electric charge. It is measured by the change in charge in response to a difference in electric potential, expressed as the ratio of those quantities. Commonly recognized are ...
, and the circuit is subjected to a disturbance such as opening of a switch.
[Roger C. Dugan et al, ''Electrical Power Systems Quality Second Edition'',McGraw-Hill 2002, , chapter 4 page 120] It can cause overvoltages and overcurrents in an electrical power system and can pose a risk to
transmission
Transmission may refer to:
Medicine, science and technology
* Power transmission
** Electric power transmission
** Propulsion transmission, technology allowing controlled application of power
*** Automatic transmission
*** Manual transmission
*** ...
and
distribution Distribution may refer to:
Mathematics
*Distribution (mathematics), generalized functions used to formulate solutions of partial differential equations
* Probability distribution, the probability of a particular value or value range of a vari ...
equipment and to operational personnel.
Ferroresonance is different from linear resonance that occurs when inductive and capacitive reactances of a circuit are equal. In linear resonance the current and voltage are linearly related in a manner that is frequency dependent. In the case of ferroresonance it is characterised by a sudden jump of voltage or current from one stable operating state to another one. The relationship between voltage and current is dependent not only on frequency but also on other factors, such as the system voltage magnitude, initial
magnetic flux
In physics, specifically electromagnetism, the magnetic flux through a surface is the surface integral of the normal component of the magnetic field B over that surface. It is usually denoted or . The SI unit of magnetic flux is the weber ( ...
condition of transformer iron core, the total loss in the ferroresonant circuit, and the point on wave of initial switching.
[
Ferroresonant effects were first described in a 1907 paper by ]Joseph Bethenod
Joseph Bethenod (27 April 1883 – 21 February 1944) was a French electrical engineer and inventor best known for his inventions in the field of radio transmission, but interested in a wide variety of topics including electric motors and automobil ...
.[ The term ''ferroresonance'' was apparently coined by French engineer ]Paul Boucherot
Paul Boucherot (1869–1943) was an engineer with the Chemins de Fer du Nord (Northern Railway of France). He studied at the elite École supérieure de physique et de chimie industrielles de la ville de Paris (ESPCI) where he later also taught e ...
in a 1920 paper, in which he analysed the phenomenon of two stable fundamental frequency operating points coexisting in a series circuit containing a resistor, nonlinear inductor and a capacitor.
Conditions
Ferroresonance can occur when an unloaded 3-phase
Three-phase electric power (abbreviated 3φ) is a common type of alternating current used in electricity generation, transmission, and distribution. It is a type of polyphase system employing three wires (or four including an optional neutral r ...
system consisting mainly of inductive and capacitive components is interrupted by single phase means.[Dugan, R. C.]
''Examples of Ferroresonance in Distribution Systems''
accessed 2011-09-06[Ferracci, Ph.]
''Cahier technique n° 190: Ferroresonance''
Groupe Schneider, accessed 2011-09-06 In the electrical distribution field this typically occurs on a medium voltage electrical distribution network of transformer
A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer' ...
s (inductive component) and power cables (capacitive component). If such a network has little or no resistive load
Load or LOAD may refer to:
Aeronautics and transportation
*Load factor (aeronautics), the ratio of the lift of an aircraft to its weight
*Passenger load factor, the ratio of revenue passenger miles to available seat miles of a particular transpo ...
connected and one phase of the applied voltage is then interrupted, ferroresonance can occur. If the remaining phases are not quickly interrupted and the phenomenon continues, overvoltage can lead to the breakdown of insulation
Insulation may refer to:
Thermal
* Thermal insulation, use of materials to reduce rates of heat transfer
** List of insulation materials
** Building insulation, thermal insulation added to buildings for comfort and energy efficiency
*** Insulated ...
in the connected components resulting in their failure.
The phenomenon can be avoided by connecting a minimal resistive load on the transformer secondaries or by interrupting the applied voltage by a 3-phase interrupting device such as a ganged (3-pole) circuit breaker
A circuit breaker is an electrical safety device designed to protect an electrical circuit from damage caused by an overcurrent or short circuit. Its basic function is to interrupt current flow to protect equipment and to prevent the risk ...
.[
]
See also
* Constant-voltage transformer
References
{{reflist
Electric power distribution