Harmonics and Power Quality
Power quality is important for everyone
Power Quality relates to the amplitude, frequency and distortion of the supply system.While the amplitude and frequency of the supply is largely controlled by the utility, the distortion of the wave (voltage or current) is attributed to the user (of the power) or the loads. Linear loads like an induction motor, an incandescent bulb, resistive heating or a capacitor bank draw a sinusoidal current which follows the wave shape of the supplied voltage. On the other hand, most of the common loads nowadays are non-linear, like VSDs (Variable Speed Drives), rectifiers, UPS-systems, computers,TV sets, energy efficient (fluorescent) lamps, photocopiers etc.These loads draw a current from the source which does not follow the voltage wave shape and hence introduce distortion.
The distortion is introduced by harmonics generated by the non-linear devices. These harmonics are a growing problem for both electricity suppliers and users.
Harmonics can lead to serious problems:
• reduced energy efficiency when harmonics are in the network
• overheating of cables, motors and transformers
• damage to sensitive equipment
• tripping of circuit breakers
• blowing of fuses
• premature ageing of the installation
• capacitor overloading and failures
• high current in neutral conductors
• excitation of network resonance
• no connection permit from the utility if harmonic levels are too high
Typical VSD supply current
COMPANIES MUST TAKE ACTION !
1. Ensure the operational reliability of all systems
2. Ensure compliance with standards
3. Better use of existing networks
