Caravan park with 3 phase power supply, our B phase amps are overloading and tripping the circuit breaker

Question

We have had the phases balanced, and the problem is still occurring. We initially added a 60 kVA generator taking out our amenities block, and this helped during peak power times of day. It is no longer solving the problem, and the B phase is again rising and blowing circuit breakers. We have now added a second generator to another area of the park and managing to keep current below the trip point. The park is not at peak capacity, and this has never previously been a problem, even when the park has been full. Why would this be happening? We have had multiple electricians in to assess the problem with no outcome. All are perplexed as to why this is happening. Can someone provide ideas or suggestions?

Answer 1

In Australia they use Europe style 230V phase-ground and 400V phase-phase, with virtually all loads being single-phase-to-ground loads.

It would be virtually impossible to balance a caravan park, because it's going to matter very much which spots are occupied. For instance if you have a cluster of larger spaces for larger RVs and they're all on the same phase... or if the spaces that tend to be taken first are all on the same phase... you could totally defeat phase balancing.

So the first thing I would do is map the entire park and clearly mark each power stand to indicate which phase it is on. I'd even have a colored site map with colored dots for each phase or section. Then I would look at your site layout on days you are having problems.

Electric service calculations for caravan (RV) parks presume a "diversity of loads" - any given caravan isn't at maximum power for very long, and so when you have a group of caravans, it's very unlikely for them to all be max'd out at once. This is factored into service sizing to caravan parks. Note also that electric vehicles are a big "monkey wrench". In North America at least, every EV comes with the kit needed to charge at caravan parks, as this is a "last resort" if DC fast chargers can't be found on the road. RV parks are happy to help, but they draw the maximum allowed continuously. So a group of EVs can be a real problem, and extra attention must be paid to phase balancing there.

Answer 2

Ask one of the electricians to come back and install a logging device recording voltage/power for each phase to try to get more data and see if your installation needs upgrading or if there perhaps is something wrong somewhere else, eg: voltage sag, defective breaker. Of that you are exceeding the circuits capacity.
You may even want live metering installed permanently to keep track of power on your site since the energy prices keep going up.

From what you describe though, it sounds like the original planning of the electrical network may not have taken into account the higher loads of today. The simultaneity factor needs to be reviewed.

You could inquire one of the electricians again. This time not for fault finding but for mapping, advising and possible upgrading the installation.

Answer 3

You need more information about the electric power consumption of the caravan park. At least there should be current meters for all three phases. For instance if you have 100 A max current for each phase and you see 20 A first phase, 30 A second phase and 80 A third phase, then it would be better to shift some of the load from third phase to the two other phases. If you see 45 A, 50 A and 55 A the load distribution is much better.

A current clamp meter may be used by a carefully instructed person at a place without any blank metallic surfaces at 230 V. This person should know: what is a current clamp, how is a measurement done, how to select the current range, where a clamp meter may be used and where not. Only at cables with 230 or 400 V but not at 10 kV or higher.

I would try this: prepare and actualize a list of the number of caravans connected to each phase. If a new caravan arrives place it at the phase with the lowest number of caravans. If a caravan leaves don't forget to decrement the number of caravans for the phase used by the leaving one. If all caravans assigned to the same phase leave together, it might be better to shift some caravans from the two other phases to the phase without caravans at the moment.

The arriving caravans may chose a place they like but only at the phase with the lowest load. If a caravan wants to move from one place to another don't forget to check the list.