Requirement
The project consists in the construction of a 52MW PV power station in the near future in Israel. This PV power station will be connected to the 161kV HV electrical grid of the country.
In this context, CAPSIM was chosen in order to perform the following analyses on the future PV station :
- Verification of the harmonic levels produced by the PV + inverters at the connection point in the different possible network configurations of the future installation
- Observation of the impact of the capacitor bank switching (in terms of overvoltage and switching current) on the future PV installation and on the equipment
- Study of TRVs (transient recovery voltage) across the circuit breakers during normal operations and following faults such as short-circuits
Realization
CAPSIM built a numerical model of the future PV electrical network on Powerfactory software. Hence, both static type calculations (such as harmonic calculations) and transient type calculations (capacitor bank switching for example) were performed with this software.
Once completed and validated (via load-flow analysis) the model was used to perform the following analyses :
- Harmonic study : this helped evaluate the various current and voltage harmonics at the 161kV connection point and compare these values to the acceptable limits by the electrical network operators. With the presence of capacitor banks, the various different network configurations were taken into account in the calculations in order to analyse the anti resonance risks
- Analysis of capacitor bank switching : the impact of the capacitor bank switching phenomenon on the network was quantified. The specific case of back-to-back switching was particularly monitored (energizing of a capacitor bank with another one already connected) as this scenario is the one where the inrush currents are the highest. The possibility of controlled switching was also studied and validated via simulations. Finally, the equipment capacities towards the worst case overvoltages were checked and validated (via IEC 60071 standards).
- TRV calculations : here, the TRVs across the circuit breakers were calculated in order to check if they can be opened during normal operations or following faults such as short-circuits (via IEC 62271 standards).
Currents through the circuit breaker during the engagement of a capacitor
Results
This study helped the client tot :
- Know the maximum current and voltage harmonics of the PV installation at the 161kV connection point
- Install a precisely sized anti-harmonic inductance in series with the capacitors in order to drastically reduce harmonic contributions to the 161kV connection point and thus bring them to acceptable limits
- Suggest settings for the protections in order to not trip during capacitor switching phenomena
- Validate the installation’s equipment against overvoltages (IEC 60071- overvoltages due to capacitor switching) and against TRV (IEC 62271 – TRVs produced across circuit breakers during normal operations or following a fault in the PV station’s electrical network).
Power factory numerical model of the future PV power station
