Transformer explosion cuts power across parts of Centurion

What happened

On 20 May 2025, at around 05:50, Transformer 1A at the Zwartkop Substation in the Tshwane metro exploded, causing a power outage across multiple areas. The source reports fire damage to the Lyttelton/Kwagga Overhead Line 1 and does not say whether the transformer itself caught fire. The explosion also tripped the Lyttelton Line 1 at Njala, which initially cut supply to the Wingate, Aries and De Hoewes substations. Supply to those three areas was later restored.

Residents in Zwartkop, Valhalla, parts of Claudius, Clubview, the military base in Thaba Tshwane and Zwartkop Airbase remained without electricity while the metro's Energy and Electricity Department carried out restoration work. The fire-damaged Lyttelton/Kwagga Overhead Line 1 was due for repair, and the source gives the start of those repairs as 20 May.

Contributing factors

The source reports that the destruction of 630mm high-tension cables and essential substation control cables significantly complicated repairs. It also reports that cables for Transformer 2B had been stolen and had to be replaced. The source does not state the cause of the explosion.

Lessons learned

1. Substation control and protection cabling should be physically secured, because cable theft can extend restoration times after an incident.
2. After a transformer fault, oil sample analysis and full protection grading tests should be completed before the unit is re-energised.
3. Operators should hold spare high-voltage cable and control cable stock so that repairs are not delayed by long procurement.
4. Restoration updates should be published on a fixed schedule, so that affected customers know when to expect the next information.

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

Source

citizen.co.za