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Solar PV - Impact on rating of supply cables and transformer

We are in the process of getting some quotes for a solar PV installation on the roof of a large warehouse. The solar PV is probably going to be around 200kW

At the moment we are not connected to the grid and are waiting for new substation to be completed and cabling and transformers to be installed. 

One of the solar PV suppliers has said that we would need to add 200kW to our maximum demand figures when informing the DNO of our requirements which would probably take us to next size of transformer.

Can somebody point me in the right direction to read up about this or explain why the power from the solar PV generated  is added to the  max demand figures.

Thanks

Parents
  • In most circumstances, you wont need to add the 200kva solar production to the load. If the load is say 250kva, and solar production is at the full 200 kva, then the net load is the difference between the two, or 50 kva.

    Calculate for the worst case which is probably maximum load at 16-00 on a winter evening with no solar, or it might be maximum solar production on a sunny bank holiday, with very little energy being consumed.

    If the installed load is say 1,000 kva, then the worst case is full load and no solar power, as might reasonably occur on a winter evening.

    If the installed load is small in comparison to the solar power production, then the worst case is minimum load outside of working hours in bright sun.

    If the transformer is on site or adjacent, it might be desirable to have it set to a slightly  lower voltage such as 415 volts rather then the widely used 433 volts, no need to allow for voltage drop in lengthy LV mains if there aren't any.

    Caveats, if solar production might exceed the load, make certain that the transformer wont trip on reverse power.

Reply
  • In most circumstances, you wont need to add the 200kva solar production to the load. If the load is say 250kva, and solar production is at the full 200 kva, then the net load is the difference between the two, or 50 kva.

    Calculate for the worst case which is probably maximum load at 16-00 on a winter evening with no solar, or it might be maximum solar production on a sunny bank holiday, with very little energy being consumed.

    If the installed load is say 1,000 kva, then the worst case is full load and no solar power, as might reasonably occur on a winter evening.

    If the installed load is small in comparison to the solar power production, then the worst case is minimum load outside of working hours in bright sun.

    If the transformer is on site or adjacent, it might be desirable to have it set to a slightly  lower voltage such as 415 volts rather then the widely used 433 volts, no need to allow for voltage drop in lengthy LV mains if there aren't any.

    Caveats, if solar production might exceed the load, make certain that the transformer wont trip on reverse power.

Children
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