Load-shedding having 'devastating impact' on water pump stations

Just two hours of load-shedding has a “devastating impact” on a water pump station, interrupting water supply to residents. 

This is according to Rudy van Lingen, a station manager at Rand Water's Roodepoort pump station which supplies water to reservoirs in the West Rand area.

Talking on the sidelines of City Power and the Gauteng government's site visit to the station on Thursday, Van Lingen said restarting the system could take about 30 minutes when the power goes off.

This means they will run the system for an hour and 30 minutes during load-shedding instead of a full two hours.

When the load-shedding is over, they have to again restart the system for another 30 minutes.  

With three backup generators at the site, when the electricity goes off, technicians have to rack their standby circuit breaker, physically disconnecting from City Power's electrical circuit and connecting their generators.

The pumps do not work while they are racking the circuit breakers. 

“When we lose power from City Power, our pumps trip and we switch over to our breakers because we don't want to feed back into their system. We switch over our breakers and start our generators. Once our generators are up and running, we can then start one pump,” he said.

Van Lingen said their pumps have a sequence in which they need to be reset. 

“Remember now the pumps are not running, people are complaining, the reservoirs are dropping. We can then start pump No 1. We have to go through a sequence. It takes about a minute or two for a pump to go through a sequence.

“Through this process, we have already lost about 30 minutes. We start one pump, set the second pump in sequence and when it is ready we can start pumping. When the power comes back after two hours, we have to go through the whole process again,” he said.

They lose about 20% of water in reservoirs when they are not pumping and if the power is off, they continue losing water, he said.

“You keep losing capacity in the reservoirs. If you lose capacity in the reservoirs, you lose pressure in the pipelines — that's when consumers start complaining that the water pressure is either low or they are not getting water from their taps.”

They need at least two to three days of uninterrupted power supply to refill the reservoirs to at least 70-80% capacity, which can take longer during a heatwave, he said.

One solution would be to be exempted from load-shedding, but Van Lingen doesn't see that happening any time soon.

Resetting the pumps will eventually result in wear and tear, he added.

“Now valves are opening, pumps are resetting, bearings are cooling down and when you have to start everything again and go through the whole system opening up again, you start having tear and wear on that.”

Anza Mudau, GM for grid reliability at City Power, said to minimise disruption at the Roodepoort pump station they recently commissioned one of their new substations, which will be connected to the station. 

They need to get supply directly from the substation, lay fibre and install remote terminal units to enable City Power to control the terminals, he said.

“We are looking at about R45m to achieve the installation. Rand Water also proposed a battery solution which entails us putting up a 4MW power storage system. Batteries should be enough to cover at least two hours of load-shedding and avert the gap which they were talking about in terms of going to restart the motors.”

TimesLIVE