Improvement of the Ulco network voltage regulation using a phase shifting transformer

Silence Sithole, Nhlanhla Mbuli, J. H.C. Pretorius

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

4 Citations (Scopus)


In networks feeding loads that vary from low levels during low loading and extremely high levels during high loading conditions, with lines providing supply to these loads being very long, voltage regulation within the acceptable range can be a challenge. In a case where such lines to the load centers constitute parallel corridors with different impedance characteristics, and therefore different loading properties, problems of regulating voltages within acceptable limits may be experienced. The previous paper [1, 2, 3, 4] proved that by changing the phase angle of the network connected in parallel, the voltage can be regulated. These voltages can be increased or decreased depending on the angle change. The Ulco network has the described characteristic and was used as a case study to observe network voltages during different loading conditions. This network experience overvoltages during lightly loaded conditions and undervoltages during heavily loaded conditions. The phase shifting transformer is one of the devices broadly used in power systems to change the power flows by changing the phase angle. This paper provides the analyses of peak and off-peak loading of the Ulco network voltages. The phase shifting transformer is then used to mitigate against voltage limit violation.

Original languageEnglish
Title of host publicationIEEE Africon'11
Publication statusPublished - 2011
EventIEEE Africon'11 - Victoria Falls, Livingstone, Zambia
Duration: 13 Sept 201115 Sept 2011

Publication series

NameIEEE AFRICON Conference


ConferenceIEEE Africon'11
CityVictoria Falls, Livingstone


  • load forecast
  • off-peak load
  • overvoltages
  • peak load
  • phase angle
  • phase shifting transformer
  • undervoltages
  • voltage limits
  • voltage regulation

ASJC Scopus subject areas

  • Computer Science Applications
  • Electrical and Electronic Engineering


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