In this post, we discuss the topic Ferreresonance, which is a common phenomenon shown by electrical transformers in the electrical system.

Ferreresonance meaning

The Ferreresonance is a non-linear resonance phenomenon that is affected at the transformer.

  • It is caused by the non-linear inductance and capacitance of the electrical system.
  • This will leads to transmission and distribution equipment failure.

Ferreresonance in transformers

The Ferreresonance property will occur mainly at the transformers when the primary coil of the transformer is connected line to ground in an ungrounded circuit.

  • Common transformers are designed to operate on the linear portion of the magnetization curve.
  • So there are no methods to control the output against changing input voltage at it.
  • But the Ferroresonant transformers will be used to regulate the Ferreresonance effect.

Ferreresonance in power quality

An unusual variation that happened on the transformer will affect the power quality badly.

  • The change in power rating at the system due to Ferreresonance at harmonic, steady-state, over-voltage, over-current will de-energized transformer or load.
  • And also cause damages to the overall electrical equipment or electrical system.

Ferreresonance damping resistor calculation

In most cases, damping resistors are used at the transformers to reduce the effect of Ferreresonance.

  • At transformers, a fixed value of the damping resistor will be connected to the secondary of each transformer.
  • The damping resistors continually absorb the power as soon as the transformer is energized.
  • The damping resistor value will be calculated with the formula

                                     R = Us2/Kpt-pm, PR = Us 2/R

US= Rated secondary voltage (V)

Pt = transformer rated output

Pm = Power required for measurement (VA)

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