Resonance calculations

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.

Electric motors resonance

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

Capacitive reactance

eq reactance L
Xc: Inductive reactance [Ω]
ω: Angular frequency [rad/s]
C: Inductance [H]
F: Frequency [Hz]
eq reactance C
Xc: Capacitive reactance [Ω]
ω: Angular frequency [rad/s]
C: Capacitance [H]
F: Frequency [Hz]
Reactance inductor EN
Reactance capacitor EN

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.

Parallel circuit EN

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.

Some cases

We have been providing Power Quality simulations for many years. Our engineers identify the problem and HyTEPS delivers the best-fit solution. Our relations are in a wide range of sectors, including industry, hospitals and offshore. We have worked out some of our cases for you. Click on the case and read more about the challenge, our solution and the results.
You can find more cases on our cases page.


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HyTEPS Engineer

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