Parallel Resonance in Power System

In summary, installing a passive filter to filter the 5th harmonic creates a parallel circuit resonant at the 7th harmonic. This will not impede the flow of 7th harmonic currents in the line, but the 5th harmonic will be bypassed. The fundamental and other harmonic currents can still flow between points A and B.
  • #1
LagCompensator
24
1
Hi,
imagine we have the following circuit shown in the figure below. There are installed a passive filter to filter the 5th harmonic. Now, after installation this creates a parallel path with a generator connected, let's say that this parallel circuit has a resonance frequency at the 7th harmonic. Then it turns out that some load further away causes 7th harmonic currents to flow and thus exciting the parallel resonance circuit.

  1. Would this cause Z to go to infinity in theory assuming ideal components and thus stop the flow of 7th harmonic currents from A to B shown in the figure below?
  2. Would fundamental currents and other harmonic currents except for the 7th be able to flow between A and B?
parallel resonance.png
 

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  • #2
LagCompensator said:
Hi,
imagine we have the following circuit shown in the figure below. There are installed a passive filter to filter the 5th harmonic. Now, after installation this creates a parallel path with a generator connected, let's say that this parallel circuit has a resonance frequency at the 7th harmonic. Then it turns out that some load further away causes 7th harmonic currents to flow and thus exciting the parallel resonance circuit.

  1. Would this cause Z to go to infinity in theory assuming ideal components and thus stop the flow of 7th harmonic currents from A to B shown in the figure below?
  2. Would fundamental currents and other harmonic currents except for the 7th be able to flow between A and B?
View attachment 109704
1) If the line is shunted by a parallel circuit resonant at the 7th harmonic, it will not impede the flow of 7th harmonic currents in the line. It is invisible at this frequency.
2) The 5th harmonic will be bypassed by the parallel circuit resonant at its frequency but the fundamental and all other frequencies can freely pass between A and B.
 
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  • #3
tech99 said:
1) If the line is shunted by a parallel circuit resonant at the 7th harmonic, it will not impede the flow of 7th harmonic currents in the line. It is invisible at this frequency.
2) The 5th harmonic will be bypassed by the parallel circuit resonant at its frequency but the fundamental and all other frequencies can freely pass between A and B.
Correction:
2) The 5th harmonic will be bypassed by the SERIES! circuit resonant at its frequency but the fundamental and all other frequencies can freely pass between A and B.
 

FAQ: Parallel Resonance in Power System

What is parallel resonance in power systems?

Parallel resonance in power systems is a phenomenon that occurs when the inductive reactance and capacitive reactance in a circuit cancel each other out, resulting in a very high current flow. This can cause significant voltage fluctuations and can potentially damage equipment in the circuit.

What causes parallel resonance in power systems?

Parallel resonance is caused by the interaction between inductance and capacitance in a circuit. When the inductive reactance and capacitive reactance are equal, they cancel each other out, resulting in a high current flow. This can be caused by mismatched equipment, improper circuit design, or external factors such as lightning strikes.

What are the effects of parallel resonance in power systems?

The effects of parallel resonance can include voltage fluctuations, excessive current flow, and potential damage to equipment in the circuit. It can also cause power losses and disruptions in the power supply. In extreme cases, it can lead to power outages and equipment failure.

How can parallel resonance be prevented in power systems?

Parallel resonance can be prevented by proper circuit design and matching of equipment with similar inductive and capacitive reactance values. In some cases, adding additional capacitors or inductors to the circuit can also help balance the reactance and prevent resonance. Regular maintenance and monitoring of power systems can also help identify and address potential resonance issues.

What are the consequences of ignoring parallel resonance in power systems?

Ignoring parallel resonance in power systems can lead to serious consequences, including equipment damage and potential power outages. It can also result in financial losses due to equipment repair or replacement, as well as the cost of lost productivity during power disruptions. In extreme cases, it can also pose a safety risk to individuals working with or near the affected power system.

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