AC phasors and fault detection

How to use this resource

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Below are a series of interactives which support the resource. Each interactive can be launched by clicking on its image, or through links in the PDF itself.

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Topic areas

Electrical and electronic engineering

  • AC theory
  • Resistance, reactance and impedance


  • Phasors
  • Vector addition
  • Pythagoras’ theorem
  • Trigonometry



Problem statement

When AC power is distributed and used in an electrical power application there will usually be a monitoring system in place to detect any faults that will inevitably develop through prolonged, long-term use.

How can engineers use the characteristics of an AC circuit to detect when a fault condition has occurred?


Click the image to load Phasor 1. 

AC phasors

The above interactive allows you to change the frequency of the generator, along with the amount of capacitance and inductance applied, thereby allowing you to see the effects of voltage against current.

Click the image to load LCR Series 1. 

The above interactive allows you to change the frequency, resistance, inductance or capacitance, and displays the appropriate impedance effect or supply voltage needed.

Supported by

  • Royal Academy of Engineering
  • Motorola Solutions Foundation