Resonance calculations prevent catastrophes

The response of conductors and capacitors changes in accordance with frequency. A combination of inductive and capacitive loads exists in every installation. A small harmonic current injection at a particular frequency can result in a vast increase in harmonic distortion voltage, as well as other undesirable events. These can result in equipment breakdowns and errors. In turn, this leads to loss of production, with all associated costs.

Advantages of Resonance simulations

  • Solve issues such as unexplainable component failure
  • Prevent damage to distribution boards
  • Cost-effective prevention of issues

Simulations: planning and forecasting resonance problems

Resonance problems in new installations can be avoided by performing resonance and harmonic simulations during the design stage. This means the phenomenon can be predicted and consequently a solution can be implemented before the problem actually occurs.

If resonance problems are already occurring in an installation, a simulation is performed to find out exactly which frequency these are associated with, and under which operation conditions. Based on this, a solution is also modelled, using Power System Software (PSS) analysis to shift the resonance frequency of the installation to higher harmonic orders.

What is resonance?

Resonance is a phenomenon whereby the voltage becomes unstable and rises uncontrollably. This voltage spike damages equipment and leads to preliminary failures and production loss. Capacitors and inductors store energy for a short time. This storing of energy is the main cause of reactive power. Resonance occurs when these energy-storing elements release and absorb the energy from the grid at the ‘wrong’ moments. Capacitors in particular are highly sensitive to higher frequency signals such as harmonics.

Causes of resonance?

Resonance occurs when a specific number of inductive loads, such as motors, and a specific number of capacitive loads, such as IT equipment, are connected at the same time. Moreover, the number of capacitors and inductors in an electrical installation not only on depends on which loads are operating, but also on the dynamic characteristics of the public electric network and/or the amount of electric generators being used. Design with resonance in mind requires thinking about cable impedance and load placement, along with consideration of the physical location.

Passive components: Inductors and capacitors

Inductors and capacitors can store in an electric field (capacitor) or a magnetic field (inductor).

Their impedance is mostly imaginary as it is related to reactive power, meaning they will do not produce real work, as resistive components do. This reactance is dependent on the electrical frequency as seen below.

Inductive reactance

impedance of an inductor equation
  • Xc: Inductive reactance [Ω]
  • ω: Angular frequency [rad/s]
  • C: Inductance [H]
  • F: Frequency [Hz]
graph of the impedance of an inductor over frequency

Capacitive reactance

impedance of a capacitor equation
  • Xc: Capacitive reactance [Ω]
  • ω: Angular frequency [rad/s]
  • C: Capacitance [H]
  • F: Frequency [Hz]
graph of the impedance of a capacitor over frequency

In the electrical grid, inductive and capacitive components are connected in parallel - for instance, motors (L) and a capacitor bank (C), to provide reactive power. When a wrong combination is made, small harmonic currents can cause large harmonic voltages, damaging all components in the installation.

circuit diagram of a parallel R-L-C Circuit

Take action before it is too late!

As soon as resonance is observed, you are too late - damage is often instant and extensive. Equipment failure can have catastrophic consequences, such as missed deadlines, sending staff home because production is not possible, and reputation loss as a result of inability to deliver. All of this can be prevented with Resonance simulations.

HyTEPS Solves resonance problems


Throughout the last 14 years, HyTEPS has been identifying, modelling and solving a wide variety of resonance problems in Low, Medium and High Voltage (LV, MV, HV) installations for customers ranging from Distribution System Operators (DSOs), large industries and solar parks to yacht builders and industrial offshore installations.
A solution is proposed based on simulations and commissioned by a HyTEPS technical engineer. A measurement afterwards shows how the resonant frequency has indeed shifted to harmonic orders where no current harmonics are injected.