Power Quality & Energy Efficiency

Managing the monthly electric bill has always been an ongoing challenge. With ever increasing costs, concerns over global warming and the decline of fuel resources, it is both our corporate and personal responsibility to reduce emissions as much as possible. With the recent pressure applied on the UK Government by the implementation of the EU Performance of Buildings directive 2002/91/EC even more pressure will be applied on industry to reduce energy wastage.

How do I reduce our energy consumption?

This is often a difficult question to answer as there are many routes to a company operating more efficiently. It could be as simple as reducing site voltage levels, limiting peak demands or if commercially viable, installing energy-saving equipment. However, the simple installation of Power Factor Correction equipment often in the past over-looked, can produce a significant reduction of the electric bill for many plants.

However what must also be taken into consideration when trying to reduce energy costs is the sites harmonic levels. Harmonic currents are high frequency currents that generate heat through skin, an effect that will not only reduce the life expectancy of all equipment connected to the network but also waste energy.

Harmonic generating loads, or more commonly named non-linear loads are divided into two categories - single phase and three phase loads. Each presents a potentially unique set of problems as a result of their characteristic harmonic spectrum.

The negative effects of harmonics fall into two categories: those of current distortion related problems and those of voltage distortion problems.

A brief summary of the effects of each problem are shown below:

Effects of high current distortion:

• Overheating of conductors and insulation degradation
• Neutral overload
• Increased transformer losses (need to over-size)
• Nuisance tripping of circuit breakers
• Neutral-earth potential
• Significant voltage distortion on networks with generators
• Overheating and possible resonance with capacitors
• Lighting ballast failures
• PC monitor stroboscopic effect
• Re-injection of harmonic currents into the utility network
• Voltage Flat topping
• Caused by Third (neutral current) harmonics flowing across network impedance

Effects of high voltage distortion:

• Causes linear devices to draw non-linear current
• Torque pulsation in motors
• Capacitor dielectric failure
• Insulation breakdown
• PC monitor and power supply failure
• Electronic lighting failure

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