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08 May 2019

Harmonics: Power Quality Article by Chauvin Arnoux

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Harmonics - A Power Quality Article by Julian Grant – General Manager at Chauvin Arnoux UK

Harmonics issues within an electrical installation frequently go overlooked due to a lack of understanding or awareness of them. Often resulting in facility managers experiencing problems within their installations and focus is given to the symptoms, rather than the underlying cause of those problems.

Within the last 30 years there has been a big increase in the number of non-linear loads connected to the electrical network, including computers and associated IT equipment, uninterruptable power supplies, variable speed motor drives, electronic lighting ballasts, and LED lighting, to name just a few. The growing use of such equipment and the application of electronics in nearly all electrical loads are beginning to have some worrying effects on the electricity supply. It is estimated that today over 95% of the harmonic interference within an installation is generated by equipment within that installation.  The Chauvin Arnoux PEL 103 Power Energy Logger tests harmonics to the 50th order.

The current waveform can become quite complex, depending on the type of load and its interaction with other components in the installation. These non-linear loads increase current, and in severe cases voltage, distortion in the electrical supply, which can lead to significant energy losses, shortened equipment lifespans, and reduced efficiency of devices. The Chauvin Arnoux PEL 103 Power Energy Logger will give a true picture of the currect consumption on the electrical network.

Harmonic currents have negative effects on almost all items on the electrical system by upsetting sensitive electronic devices and causing dielectric thermal and mechanical stresses.  The most significant of these include computer and other IT equipment crashes and lockouts, flickering lights, electronic card failures in process control equipment, power factor correction equipment failure, high load switching failure, neutral conductor overheating, unexpected circuit breaker operation and inaccurate metering.

Some of the most troublesome harmonics are the 3rd, and odd multiples of the 3rd, i.e. the 9th, 15th etc. These harmonics are called “triplens”. The triplen harmonics on each phase are all in phase with each other which will cause them to add rather than cancel in the neutral conductor of a three phase four wire system. This can overload the neutral if it is not sized to handle this type of load.

Investing in a PEL 103 Power Energy Logger will allow you to investigate individual harmonics, if you are going to invest in this type of instrument make sure it does more than just total harmonic distortion (THD).