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Question

Grid interconnection study for Solar PV system?

Paneendra Kumar BL's picture
Senior Consultant Vidyuth Kanti Engineering Services

Research, Training, Development and Consultancy in Power system. Having expertise in Design of Oil and Gas, Onshore, Offshore, Refinery, Power Plants, Substations and Industrial Plants Electrical...

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  • Mar 23, 2020
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We are carrying out a grid interconnection study for a solar PV system connected to a substation having 11kV/66kV transformer, which is connected to the larger 220kV grid . We are carrying out the following studies. Do suggest if you are doing any other studies other than this

1) Load flow 2) Short circuit study 3) Relay coordination study 4) Reactive power flow study/Voltage stability for sizing of Capacitor banks 5) Transient Stability study /determine the requirement of additional short duration energy storage device 6) Grounding Studies 7) SSR (sub sequence resonance not required 8) Harmonic load flow ( may or may not be required) 9) Insulation coordination/ surge protection study ( may or may not be required)

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the type of studies are usually a function of at least two things: the size of the plant and the voltage level at which it is connected (so-called Point of Interconnection). Take short-circuit analysis for an example, I would be more concern about computing short-circuit currents to evaluate the change in them due to the plant for a 10 MW plant than a 1 MW plant (in any case this one is a simple calculation and the custom is to do it anyway). Grounding studies are normally performed inside the plant. Stability analysis again depends on the size of your plant, I would say a good rule of thumb is than for any plant larger than 10 MW analyze the response of the system to at least three-phase normal clearing and single-line-to-ground with delayed clearing. Regarding harmonics, converters  are much more improved regarding generation of harmonics, but in any case I would ask the manufacturer the Total harmonic Distortion. The issue here is mostly resonance and I would perform a simple frequency scan to verify there is no resonance for the harmonic with the highest magnitude. Reactive power analysis is a must, specially if your system is in need of voltage support. Calculating the power factor at the POI will also give you an idea of the adequacy of reactive power. In general, this is demanded from the manufacturer but consider that a PV plant will be about 10% larger (in MVA) if you need to support voltage.

Paneendra Kumar BL's picture
Paneendra Kumar BL on Apr 2, 2020

thanks for your suggesions

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