The effect of the van Staden wind farm on the power quality of the rural distribution network
- Authors: Venter, Clement
- Date: 2018
- Subjects: Electric transformers , Wind power Electric power production
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/36761 , vital:34051
- Description: Connection of wind farms to weak networks with a typically low X/R and short circuit ratio could result in a larger variation of voltage for corresponding variation in wind farm generation output. This variation in voltage could negatively affect the quality of electrical power in the vicinity of the connected wind farm. The analysis was based on actual on-site measurement data at individual consumers’ point of supply and the effect of the Van Stadens Wind Farm integration as seen by the consumers can be determined. It was found through statistical and correlative analysis that the voltage quality measured at the test sites were not negatively affected by the presence of generation at the Metrowind Van Stadens Wind Farm. The voltage was found to be more negatively affected by the load current drawn by the consumer at the test site and that it is foremost when the loading current was higher. No definitive evidence of an increase in voltage harmonics due to generation output or loading current was found. At two sites it was however found that the 7th order harmonic is eliminated or reduced by an increase in the generation of the wind farm above approximately 20% of maximum output. Power Factory simulations, using the Quasi Dynamic simulation tool, was performed to validate the voltage findings of the on-site power quality measurements and two things were clear from the simulations. Firstly the voltage at the point of connection has a strong negative correlation with the consumer loading current and means that the voltage will usually decrease with an increase in the loading current and vice versa. Secondly, as with the analysis of the on-site measurement results, it can be said that when current is low, then the generation output of the wind farm will have a proportional effect on the voltage. From the findings of the on-site measurements it was concluded that the wind farm did not have a negative effect on the test site consumers in the vicinity and the Power factory simulations confirmed the conclusions on the voltage analysis. It was also concluded that the local consumer load current has a larger effect on the local measured voltage than the generation output of the wind farm.
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- Date Issued: 2018
Transient analysis of erroneous tripping at grassridge static VAr compensator
- Authors: Taberer, Marcel Wayne
- Date: 2013
- Subjects: Transients (Electricity) , Electric transformers
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9603 , http://hdl.handle.net/10948/d1020918
- Description: The research work conducted and presented forward in this document is the evaluation of real time values obtained using three recording devices at two independent locations and implementing them as recorder devices in Eskom’s power system. The research work conducted was presented at an IEEE International Conference (ICIT2013) and Appendix A shows the accepted paper presented. A derived model within a simulation software package known as DIgSILENT PowerFactory is created and Electromagnetic Transient (EMT) studies are performed and then compared to the real time values obtained using the OMICRON CMC 356’s. Transformers are normally energised via a circuit breaker which is controlled by an auxiliary closing contact. By applying system voltage at a random instant in time on the transformer windings may result in a large transient magnetizing inrush current which causes high orders of 2nd harmonic currents to flow under no load conditions. A philosophy known to mitigate these currents is to energise the transformer by controlling each individual phase 120 degrees apart with the first pole closing at the peak on the voltage waveform. Transients produced due to 500MVA transformers been introduced into the power system at a certain space in time can cause nuisance tripping’s at the particular location where the respective transformer is energised. OMICRON EnerLyzer is the software tool used for the Comtrade recordings at both locations. Four independent case studies are generated within EnerLyzer software and the relevant Comtrade files are extracted for the four independent case studies relative to Transformer1 and Transformer2 switching’s. TOP software, which is a mathematical tool used to analyse Comtrade files, is then used to analyse and investigate the four case studies. Results from DIgSILENT PowerFactory are then generated according to the derived model. The results extracted depict three scenarios, indicating a power system that is weak, strong and specifically a power system that correlates to the actual tripping of a Static VAr Compensator (SVC). The results are all formulated and then evaluated in order to produce a conclusion and bring forward recommendations to Eskom in order to effectively ensure the Dedisa/Grassridge power system is reliable once again.
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- Date Issued: 2013