Using net-metering and time-of-use tariffs with small scale embedded generation

  The publication by NERSA of a study document on small embedded renewable generators covering a proposed simplified net-metering (NM) system [1] has been greeted with enthusiasm by the industry, giving a measure of certainty to the way forward. However, the announcement by the City of Johannesburg (CoJ) that it will introduce time-of-use metering on […]

Applying vacuum switchgear at transmission voltages

  Vacuum switchgear has been in extensive use in distribution systems for 30 years for the making and breaking of (fault) current and the switching of loads of all possible nature. The reliability and performance records of the vacuum switching technology are outstanding in the medium voltage range (up to 52 kV), having led to […]

High temperature low sag power line conductors

  The increasing need to expand the capacity of transmission networks, and limits on servitudes available, has lead to the development of methods to increase the capacity of existing routes. This has resulted in a new breed of overhead conductor which can remain within physical limits at higher currents and higher operating temperatures. One of […]

Open-core power voltage transformers: Concept, properties, and application

  The power voltage transformer, which is a single-phase unit used for direct conversion of power from high to low voltages, is becoming more and more relevant for substation applications. This article aims to present the properties and advantages of the open-core design concept, which has been functioning very well for a number of years […]

Implementing protection and control of future HVDC grids

  In a grid topology using HVDC circuit breakers able to provide fast clearance of a DC fault, two main contrasting, yet complementary, solutions appear possible. One would be to apply the same protection philosophy and principles used in AC systems. The second could be the “Open Grid” concept. The principle, philosophy and scheme for […]

Electrical transient interaction between transformers and the power system

  Transformers are constantly exposed to different types of transient events during their daily operation, which often imposes high stresses on their insulation structure. Field experience has shown that even when good insulation coordination studies and well-known insulation design practices are applied, a significant number of transformers suffer dielectric failures. Such failures may be caused […]

Understanding boundary conditions for reliable electrical simulations

  Understanding partial differential equations (PDEs), which form the basic language with which physicists describe many natural phenomena, such as electric and magnetic fields, acoustics, fluid flow, and heat conduction, is useful in electrical simulations. The PDEs that describe the physics inside a spatial domain of interest – so-called bulk equations – are the key […]

Power transformer fleet condition assessment and risk management

  One of the most difficult aspects of fleet management is how to deal with the unknown. When dealing with hundreds, if not thousands, of assets, the unknown must be managed, and when possible, assessed such that it becomes known. Being proactive, and planning not just for tomorrow, but for the day after tomorrow, is […]