Introduction

Generally, electrical systems nowadays are increasingly flooded with non-linear load Variable Frequency Drives, Electronic Power Supplies etc. These devices in the end products cause Harmonic currents to flow into the electrical systems, which in turn leads to heating losses and unwarranted electrical consumption. Reducing the harmonic distortions to an acceptable level can result in savings of approximately 2 to 2.5% in electrical energy cost and the net savings by way of reduced down-times of equipment, de-rated electrical switchgears, cables and accessories may amount upto 30%.

 

What is Harmonics?

Any periodic wave can be described mathematically as a series of sinusoids (sine waves) summed together. This is known as the Fourier series. The sinusoids are integer multiples of the frequency represented by the periodic cycles. Each term in the series is referred to as a "harmonic" of the fundamental frequency (50 Hertz). The term having the same frequency as the fundamental is the first harmonic, and is sometime simply referred to as the "fundamental". The term having twice the fundamental frequency is the second harmonic (100Hz) and so on.

 

The key installations where harmonic related problems can be found are in Variable Speed Drive rich environments; Personal Computers rich environments., Telephone exchanges, Hospitals with large number of electronic equipment, and circuits to which large photocopiers are attached to. In order to determine whether your facilities require Harmonic Filtering, consider answering the questionnaire for submission to Saha Sprague Limited. For low voltage heavy duty applications, Saha Sprague Limited offers its  

UNIPAK Filters.

 

The Neutral Current Problem (applicable to Personal Computer Rich Environments)

This is a typical problem, where these currents may be 173% larger than the phase conductor currents and are caused by the presence of Triplen harmonics (3rd, 6th, 9th....) and are zero sequence. This means that they have the same relationship in each conductor of a three phase circuit. Unlike balanced frequency currents, which cancel in the neutral, balanced Triplen currents add arithmetically in the neutral. This can create a hazardous situation, especially in wiring systems with undersized neutral conductors. In the US, the national Electrical Code no longer allows derating of neutral conductors in circuits serving electronic loads.

 

These neutral currents can cause unwanted MCB (Miniature Circuit Breaker) tripping in the power system; data corruption in computer systems; and unwarranted breakdowns in critical sectors such as hospitals equipment and telecom equipment power systems. The right solution to overcome these problems is to conduct Harmonic Analysis and Audit at these sites, and install Third Harmonic Filters at each of the major loads producing harmonics. Saha Sprague Limited specializes in conducting such audits and specifying, manufacturing and installing such harmonic filters wherever necessary.

 

Harmonics and Power Factor Correction

In Industrial environments, the addition of Power factor Correction Capacitors in systems present with harmonic generating equipment causes the harmonic current to resonate and grow larger, resulting in major breakdowns of equipment. We believe that our knowledge in solving Harmonics related problems is unmatched in the Industry, and this gives Saha Sprague Limited a technological advantage when specifying the inclusion of Power Factor Correction Systems, as it always conducts an audit to ensure that harmonic distortions are filtered out, and that the Power Factor Correction Systems provide the savings promised, and not magnify the bad quality of power present in the system, which so commonly occurs.

Technical Specifications: AUTOMATIC Harmonic Filters, UNIPAK Filters