Hello, in this video,
I will explain how photovoltaic production
impacts electrical calculations.
And I will illustrate it with a concrete example.
With photovoltaic production for self-consumption,
there are 2 specific points to consider
when making electrical installation calculations:
Calculations should be done for each operating mode
And photovoltaic inverters should be considered as current sources,
for short-circuit current calculations.
Let's start with the first point:
calculations should be done for each operating mode.
An electrical installation supplied by the grid,
and without local production, has only one operating mode.
When adding photovoltaic production for self-consumption,
the installation now has 2 operating modes:
supplied by the grid and the photovoltaic system, in parallel
or supplied only by the grid
when the photovoltaic system does not produce energy.
Consequently, a calculation should be done for each operating mode,
because calculations can result in significantly different power and current values,
from one operating mode to another.
Now, let's look at the second point of consideration:
the photovoltaic contribution to the short-circuit currents calculation.
The figure here presents the characteristics of a photovoltaic inverter.
In normal operating conditions,
the inverter delivers a maximum power output.
Its voltage and current values correspond to point A.
In a short circuit situation, the inverter output corresponds to point B.
Compared to normal operating conditions, the voltage is lower,
and the current is not much higher,
due to inverter electronic limitation.
No matter the short-circuit impedance, the inverter behaves as a constant current source.
Thus, when making short-circuit current calculations,
the photovoltaic system should not be represented by impedances,
as typically done for all other components of the electrical installation.
You have to add the short circuit contribution of inverters,
provided by the manufacturer,
to have the total short-circuit current value of the installation.
Let's illustrate the potential variations
when adding a photovoltaic system for self-consumption.
When the installation is only powered by the grid,
the current flowing through the main busbar
corresponds to the loads consumption
200 Amps.
When it is powered by both sources,
the photovoltaic system supplies its maximum output capacity
of 300 Amps:
200 are used to feed the load,
and the extra 100 are injected to the grid.
Therefore, in this example,
the main busbar should be sized for 300 Amps.
Now, the short-circuit current calculation.
When considering only the grid contribution,
the calculated short-circuit current value
at the main busbar is 5 kAmps.
When adding photovoltaic production,
the photovoltaic contribution to the fault current is 300 Amps.
This value is provided by the inverter manufacturer.
Therefore, the short circuit at the main busbar
is raised to 5.3 kAmps.
To sum up,
when adding photovoltaic production,
2 impacts on electrical calculations:
Calculate power and current flow for each operating mode,
in order to size correctly the equipment,
and to setup the right protection plan
And calculate short-circuit currents by adding the photovoltaic contribution
provided by the inverter manufacturer.
Now that you know how to calculate electrical installations
with photovoltaic self-consumption,
learn more about how to size, protect and manage them.
I will cover each of these topics in our next videos.
Thank you for your attention and see you soon!