Saha Sprague Limited - Harmonic Distorion Solutions

Power Quality: Harmonics

Harmonics Distortion Audit and Solution Provider
For Technical Specifications: Automatic Harmonic Filters, UNIPAK Filters

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, derated 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.

What are the consequences of high harmonic distortion levels ?
Just as high blood pressure can create stress and serious problems in the human body, high levels of harmonic distortion can create stress and resultant problems for the utility’s distribution system, the plant’s distribution system, as well as all of the equipment that is serviced by that distribution system. The result may be the plant engineer’s worst fear - the shutting down of important plant equipment ranging from a single machine to an entire line or process.

Equipment shutdown can be caused by a number of events. As an example, the higher voltage peaks that are created by harmonic distortion put extra stress on motor and wire insulation which ultimately can result in insulation breakdown and failure. In addition, harmonics increase RMS current resulting in increased operating temperatures for many pieces of equipment resulting in greatly reduced equipment life.

Harmonic distortion disrupts plants. Of greatest importance is the loss of productivity, throughout and possibly sales. These occur because of process shutdowns due to the unexpected failure of motors, drives, power supplies or just the spurious tripping of breakers. Plant engineers realise how costly downtime can be and pride themselves in maintenance and repair budgets can be severely stretched. For example, every 10^oC rise in the operating temperatures of motors or capacitors can cut equipment life by 50%.

Equipment		Consequences
Current Harmonic Distortion Problems
Capacitors	Blown fuses,
	Reduced capacitor life
Motors	Reduced motor life
	Inability to fully load motor
Fuses/Breakers	False/spurious operation
	Damaged components
Transformers	Increased copper losses, reduced capacity
Utility meters	Measurement errors/higher billings
Telephones	Interference (low frequency hum, noise)
Voltage Harmonic Distortion Problems
Drives/Power Supplies	Miss-operation due to multiple zero crossings
Transformers	Increased noise, possible insulation failure
Motors	Mechanical fatigue

The Neutral Current Problem
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 through the use of Automatic Harmonic Filters, 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.



For further information on checking out the quality of power in your facility, contact:

For further information on checking out how efficiently you are using energy in your facility, contact:

Saha Sprague Limited

No. S-915, South Block,9th Floor, Manipal centre,47, Dickenson Rd, Bangalore – 560042Tel: 080 – 2509 2274,2509 2275

Email: contact@saha.net