HARMONIC SURVEYS


Work in harmony with your harmonics, with an EDC harmonic survey.

harmonic survey from edc harmonic surveys from edc

Harmonic distortion: difficult to diagnose, but easy to resolve, is caused by items of non-linear plant connected to the power supply network. Harmonics can present in a number of ways: if you're experiencing any, or all of the problems below, the cause is most likely harmonics.

Motors running hot / slow Fuses blowing Breakers tripping
Equipment overheating Harmonic resonance Lighting flickering
Insulation issues Motor torque pulses Electromagnetic load failures

 

The result? Unexpected down-time, shortened equipment life & loss of production.

But why did it happen? Possibly because you were being energy efficient. Variable speed drives save money and the environment (without them processes can't be controlled efficiently and motors have a shorter life span due to the high start-up current). They can also cause harmonic distortion due to the relationship between voltage & current as non-linear loads 'chop' & 'pulse' the current in order to control frequency, causing 'spikes' in the power distribution system. Fluorescent lamp controllers and computer power supplies can also contribute to the creation of harmonic distortion.

an EDC engineer conducting a harmonic surveyHow do you fix it? Using ABB low harmonic drives is one way (they are designed to reduce the harmonics to a negligible amount), but there are other solutions, including active filters - PQFs - (designed to cancel out harmonics). As ABB advises:
"All harmonic problems have a cure, but the solution varies with the conditions on site and it is important to apply the measures that will work where you are. There is no universal remedy that will solve all harmonics issues".
The solution can be one of three approaches: Reduction, Cancellation and Diversion. But first, you need to establish the level of harmonic distortion, which is where a harmonic survey comes in. An EDC engineer will attend site to establish the point of common coupling, investigate the supply transformers, and connect our test equipment. This will run unobtrusively for seven days, collecting data on your harmonics. Total site time is often less than 4 hours. The report is based on the utility industries recognized engineering recommendation G54:1, (this standard is generally higher that the EU requirement) but other standards can also be catered for. Possible savings can then be identified from the detailed analysis we will provide you with.

These savings can often be in the form of:

1) Improving the power factor on the system, by hardware modification, such as the use of chokes or active rectifiers and power quality filters (which cancel out your unwanted harmonics).

2) Reducing the harmonic noise from the system by hardware modification, thereby reducing the economic penalty for “noisy” load and general “heat” losses within the electrical system.

3) Or, in some cases, replacing ageing equipment within your system with low harmonic variable speed drives.

If you believe you have harmonic distortion in your system, speak to variable speed drive experts. Harmonic distortion can be identified and corrected by a harmonic survey, but it is also possible to embark upon a course of incorrect remedial action, which can prove both costly and ineffective.

Contact EDC today for your comprehensive harmonic survey, and start smoothing out the spikes in your supply. Read more on harmonic surveys in our blog spot.

You can also compute your network harmonics by using ABB's Drivesize programme, which is designed to assist you in selecting the optimal motor, drive and transformer for your application. 

Or view ABB's video on managing & controlling harmonics.