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Quality of Supply

Good Electrical Power Quality is extremely important to modern equipment and industrial processes. Modern electronic equipment is highly sensitive to supply voltage distortion and short term under-voltages (voltage dips or sags), resulting in equipment malfunction/failure and production losses.
 
Voltage Dips
The centralised power generation in RSA requires long transmission lines to the load centres. These transmission lines are subject to lightning, bird activity, trees, bush/cane fires, insulation pollution, equipment failures etc.All these factors result in a large number of unavoidable faults, with consequent voltage dips until the faults are cleared. The voltage dips cause equipment malfunction/failure with subsequent production loss and/or impact on human safety.
 
Rainbow Technologies has over 35 years of experience in Measuring, Analysing, Modelling and designing Solutions to voltage dip problems. We have patented the Dip Doctor (successfully implemented in several industrial installations) which provides significant dip ride-through capability for large (ie >10MW) plants.
 
We also have extensive experience in "soft" and "low cost" voltage dip ride-through improvement, including:

 Slugging motor contactors
 Dip proofing variable speed drives (VSD's)
 UPS support of SCADA and control systems
 Unique designs of low cost dip-detectors and flying restart technology
 
A short summary of major studies is listed below:
 
voltage dips
 
Harmonics
The proliferation of VSD's combined with low fault levels has created heightened levels of harmonics. Added to this is the inexperienced installation of Power Factor Correction capacitor banks resulting in harmonic amplification due to system resonances.

South Africa has promulgated a national specification (NRS048) which limits the maximum harmonic levels at each busbar. This ensures equipment tolerance as well as compliance with the electrical supply authority.
Rainbow Technologies has extensive experience in harmonic problems from:

 Measurements and audits
 Modelling for existing and greenfields installations
 Design of harmonic filters
 Procurement, Engineering, Project Management and Commissioning of installations
 
A short summary of selected studies/investigations is listed below:
 
harmonics
 
Voltage Unbalance and Flicker
Voltage unbalance causes overheating and failure of 3 phase induction motors, as well as control malfunction of VSD's.
Flicker causes human annoyance and onset of convulsions with epileptic.
 
Voltage unbalance is mainly caused by unbalanced loading of a 3 phase network and/or untransposed transmission lines.
 
Flicker is caused mainly by open arc electric furnaces. Solutions involve:
 
 Measurement and identification of source
 Modelling of system
 Balancing of loads
 Improving fault levels
 Installation of Static VAr Compensators (SVC's)
 Correct specification of motors and associated protection
 
A summary of relevant studies is given below;
 
unbalance
 
voltageImpulses/Spikes
Impulses are propagated through the electrical networks due to lightning and switching transients.
Equipment has to be correctly specified (BIL) and adequately protected (correctly applied and specified surge arrestors).
Additionally the electrical system must be adequately earthed and bonded.
 
Rainbow Technologies provides:
 
 Measurement and identification of problems
 Modelling of system
 Correct design of earthing, busbars and surge arrestors
 
 
A list of selected experience is given below:
 
impulses
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  • ECSA
  • SAIEE
  • UKZN
  • Millenium Power