Distribution transformer failure
Hi, my apartment building had a power outage recently and I started learning a bit about power distribution and I have some questions.
The building is located in North America (British Columbia). I think there are distribution lines 3-phase 7.2kV in the back alleys. On the pole behind my building there are three transformers, I think one for each phase. (See photo)
Recent there was a power outage to the whole building (50 apartments) and no other buildings in the area. Someone in the building said that earlier in the day (evening) the hot water stopped being hot. This might be unreliable information. There is no water tank in the apartment so I assume it is central but I don’t know if it’s gas or electric. Then at 9pm the lights went out to the whole building. I went outside, there was an electrician utility van, he said the “transformers failed and need to be replaced, they are bringing new transformers from the warehouse”. Notice in the photos the wires burned out.
It was a hot day that day, it is possible many people were using their AC that day, not sure.
About 4 hours later the power came back.
Here’s my questions:
- How could all three transformers burn out at the same time? Wouldn’t it be more likely to lose one at a time?
- Could losing one phase explain the water going cold? Maybe the water heater is on one phase and the lights on a different phase that continued running?
- Is it possible only one transformer burned but the technicians turned off power to the others on purpose for maintenance?
- What are common reasons for transformers burning out this way?
Thanks in advance!