Residents of many of Johannesburg’s suburbs have recently experienced lengthy interruptions in their electricity supply. City Power, Johannesburg’s electricity utility, has offered various reasons for the outages, from cable theft to equipment failure. The question, however, is when will the city’s residents be able to depend on a reliable supply of electricity?
In trying to explain what was going on, City Power blamed faults at its substations, unexpected additional load and its inability to meet that load. The solution was to “rotate” the supply, the power utility said. This means that while some areas will have power, others will not. Thus, the available power was being shared out among the suburbs against a time-based schedule.
However, residents have claimed that the rotation does not follow the schedule on City Power’s website. In one case, a woman in Kensington said that she cannot bake to order since she cannot be sure whether she will have power for her oven. Of course, she could buy a gas-fired oven, but why should she?
The outages have impacted at least 32 suburbs, from Melrose in the northwest to Kew in the northeast; and from Kew in the northeast to Kensington in the southeast, affecting tens of thousands of residents.
City Power’s spokesperson, Sydney Mphahlele, as quoted by EWN, said that the utility had lost power from the Sebenza substation near Kempton Park and that technicians had been sent to the site to restore power.
According to Member of the Mayoral Committee (MMC) for environment and infrastructure services in the City of Johannesburg, Councillor Nico de Jager, as quoted by the Sandton Chronicle, the backlog in infrastructure maintenance in the city is enormous, and things will probably only get worse before they get better. He apologised to the public, saying that communication between the power utility and the public needs to be improved.
In his attempt to improve communication, De Jager is quoted as saying that Sebenza is one of those substations which is “well overdue for an upgrade and as a result we have these outages”. While it’s true that much of Johannesburg’s infrastructure needs upgrading, Sebenza substation does not. He may be unaware of the fact that the Sebenza substation underwent a massive upgrade programme just six months ago. The site was modernised with new equipment being installed.
Having visited the site myself in November 2017 as a guest of the company contracted by City Power to undertake the upgrade, I am convinced that the Sebenza substation is not “overdue for an upgrade”. Following that visit I wrote “Largest substation in a decade: Within budget and ahead of schedule”, which was published in the January 2018 edition of Energize.
The real cause of the recent outages in Johannesburg’s eastern suburbs was a failure at the Prospect substation’s 88 kV line on 28 June. City Power later confirmed this, although no reason as to why Prospect failed has been given. City Power’s communications spokesperson refused to answer questions when I phoned him about the problem, saying he was too busy to speak to me. Prospect did not fail because it was overdue for upgrading either – it had been upgraded in 2015.
When Prospect tripped, the utility apparently decided that the quickest way to restore power was to transfer the load onto Sebenza. According to the contractor, the additional load caused the transformer and its oil to heat up, a gasket gave way and oil started leaking from the transformer. The automatic protection circuit at Sebenza substation operated and isolated the transformer, thereby removing power.
Sebenza is designed to have three 315 MVA, 275/88/22 kV transformers, making the total output of the substation almost 1000 MVA. However, according to the contractor, City Power had insisted on the substation being energised before the second transformer was installed. Had the second transformer been installed prior to the failure at Prospect substation, Sebenza would have carried the load and supplied the eastern suburbs with power, says the contractor.
The transformer at Sebenza has been repaired and reenergised, additional power is being sourced from the Kelvin Power Station (up from 45 to 150 MW), and yet supply rotation is still (at the time of writing) going on. Sebenza is apparently supplying 250 MVA to Johannesburg.
In attempting to improve communication between City Power and the residents of Johannesburg’s eastern suburbs, both the MMC and the City Power made statements which have not had the desired effect. Rather, it is disconcerting to hear that things will probably only get worse before they get better.
The arrival of a cold front in the first week of July will have increased the load on the City’s electrical system, which it seems City Power cannot serve. Certainly, the residents of Johannesburg have every right to be fed up with their electricity service provider’s inability to meet their needs.
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Source: EE plublishers