Protecting IEDs with deviation of power frequency

  The deviation of power frequency component (DPFC) is a fundamental principle employed in many protection IEDs. This principle is based on the concept of superposition, where the pre-fault load current and voltage can be subtracted from the whole fault current and voltage to obtain the pure fault components. Download the PDF

Extending the effective life of a transformer

  Power transformers are key components in any electrical network and to ensure the safe, reliable and optimum working life of the transformer, care is required to limit insulation moisture as one of the most important parameters that cause insulation degradation and reduction in service life [1]. There are also safe limits of moisture content […]

Live-line techniques in high voltage overhead transmission line repair

  by Patrick O’Halloran, City Power This short paper covers how live-line (energised) techniques can be utilised to restore supply as quickly as possible in the event that high voltage transmission towers have collapsed. Download the PDF

Electromagnetic environment around HVDC transmission lines

by Matthew Sibanda and Robert van Zyl, Cape Peninsula University of Technology and Nishanth Parus, Eskom The purpose of this paper is twofold. Firstly, an overview of the interaction between high voltage direct current (HVDC) transmission lines and the environment they are operated in is presented. Secondly, the equipment required to characterise this environment is […]

Protecting pole mounted MV transformers

by M du Preez and WJD van Schalkwyk, Eskom Unplanned outages often occur as a result of transformers, drop-out fuses and surge arresters which fail during lightning storms. MV drop-out fuses with upstream feeder protection need to be properly graded to ensure correct protection during both lightning and power frequency faults. Download the PDF

The influence of HVDC transmission on AC networks

Information from Cigré The use of HVDC links between regions within an AC network is becoming increasing important because of the growing challenge of network development. The lack of public acceptance of new overhead lines delays the process. Therefore, more and more underground connections are considered inside AC networks to replace traditional overhead lines, operating […]