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PV Importing Not Decreasing as expected

Aron Wyn Jones

Im an electrical supervisor at a manufacturing plant. We installed a 1MW PV system to our roof, which has been a good success in generating power.

But we noticed through the year, as weather is improving during summer our generation increase, but our imported power from the grid tends to remaim the same. We were expecting the imported power to fall as the generated power increases.

Nothing has changed at the plant. Yes, product tonnage various but not much. Our energy KPI are being affected. 

We have checked our 7 PV inverters metering against our utility class calibrated Fluke 1777 power quality analyser, and all 7 are accurate.

Our factory power set up is as follows. We receive x2 11kV feeds from the grid which is ran around our x3 switchrooms (11kV ring main). Out of the x3 switchroom, we have x7 11kV to 400V transformers, and through one of these LV boards our PV system is connected to.

Is there anything we are missing here? As i said we generating good amounts of electricity, so from Janurary commissioning to August we've generated around 900MW of power.

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  • Hi Aron,

    Without looking at the data it could be a number of things but the first question to ask is whether there's a mismatch between the load profile and the generation. E.g. You might have a uniform consumption pattern while the solar peaks at midday; while the total GWh might be the same, so net zero, you'll be importing mornings and evenings and exporting at midday.

    Could also be sub-half-hourly metering fluctations (perhaps you have a very intermittent load), grid curtailment / ANM, metering or HV network setup, performance issues and a few other things.

    I will send you a PM.

    Jam

  • in reply to Jam

    Hi Jam,

    We altered our electricity supply network to absorb more PV generation by adding more loading. So we dont export.

    Aron.

  • in reply to Aron Wyn Jones

    As in you moved the NOP so all three substations (or at least the larger load centres) are fed through the same incomer as the PV?

    For the avoidance of confusion, when you say "imported power tends to remain the same" are we talking instantaneous or peak import power (kW), or import energy (kWh) and if the latter over what timescales are you taking measurements (HH, daily etc)? Apologies if it's an obvious question, but they're often mistaken and it'll save chasing the wrong ideas.

    Is the 1MW PV system 1MWp of PV with say 7x100kW inverters? Is there a G100 export limitation scheme, ANM or other DNO control of the generation? Is the PV generating as expected (do you have meters on the generation or can you interrogate the inverters)? Are there any other generators parallel with the grid (e.g. CHP)?

    For comparison, what was the peak and average daytime demand (kW) before the PV was installed? What's the load profile like: Is your plant a 24/7 continuous operation or are your processes cyclic or irregular depending on what's being produced?

    Presumably your load power factor is reasonably close to unity.

  • in reply to Jam

    Yea, correct we moved the NOP so that x2 switchrooms is absorbing the PV generation.

    The PV are not fed through the grid incomer.

    Imported energy (kWh) stays the same. We do have access to H-H data but dont tend to use it really.

    Yes, correct its a 1MWp!

    The meters are reading correctly because we connected our utility grade power quality analyser (Fluke 1777). Results were accurate.

    No other generators in parallel with grid that i am aware of.

    Plant is 24/7 and has a relatively constant loading. Weekends might dip a bit.

    Our PF is close to unity aswell.

  • in reply to Aron Wyn Jones

    Additionally, we take monthly meter readings of the x2 incomers. And have access to H-H data. But we tend to use the monthly kWh reading in the energy supplier invoice to calculate various things such as KPIs

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  • in reply to Aron Wyn Jones

    Additionally, we take monthly meter readings of the x2 incomers. And have access to H-H data. But we tend to use the monthly kWh reading in the energy supplier invoice to calculate various things such as KPIs

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