Isolator explosion at Njala substation leaves Tshwane areas without power

What happened

On Monday 24 August 2020 an isolator between the Njala substation and the Waltloo substation exploded in the morning, leaving parts of the City of Tshwane without power. The metro said it was back-feeding supply to affected areas. Areas reported as back-fed included Mamelodi, Faerie Glen, Garsfontein, Silver Lakes, Centurion, Zwartkops, Die Hoewes and Claudius. Technicians were working to locate the fault and isolate it in all affected areas. At the time of the report the metro had not confirmed when power would be fully restored, and said it would announce an estimated restoration time once the fault had been identified.

Contributing factors

Not reported. The metro said it was still establishing where the fault was at the time of the report.

Lessons learned

1. Substation isolators that fail violently can cut supply to a wide area, so operators should inspect and maintain isolator contacts and insulation on a planned basis.
2. Networks with alternative feeds allow supply to be back-fed to unaffected areas quickly, so operators should keep switching plans and interconnections tested and documented.
3. Publishing an estimated restoration time as soon as the fault is located helps customers and local authorities plan, so operators should agree communication steps in advance of an incident.

More lessons on electrical protection and isolation, outages, backup supply and restoration, from every incident on the register.

Source

citizen.co.za