### Browsing by Author "Atkinson-Hope, Gary"

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- ItemOpen AccessDecision theory process for making a mitigation decision on harmonic resonance in power systems(2003) Atkinson-Hope, Gary; Folly, Komla ADecision analysis is a scientific tool that is traditionally applied in business and not to electrical engineering decisions. The reason for this research is to show how to use decision analysis to make a decision on the size of a power factor correction capacitor to be installed in an end-user plant in an electrical power system, that has the potential for harmonic resonance. How to make a decision as to whether or not mitigation is needed is also researched. The two-stage decision theory process, developed by management scientists, to assist decision makers on making a decision when uncertainty, risk and certainty situations-exist, is reviewed in this thesis. To understand the application of decision theory, worked examples are included to improve understanding and to provide a foundation for the new work introduced. The addition of capacitors to a harmonic carrying system can result in resonance. Harmonic levels can be magnified well above accepted limits and this can cause damage to system components, especially capacitors. Recognizing and correcting a harmonic resonance problem before disastrous consequences arise is essential for system designers. Traditionally, when considering harmonic resonance, power factor correction capacitors are sized heuristically and a power factor of 0.95 is taken as a starting point. Usually, a harmonic analysis software package is used and a frequency scan study is conducted to generate a resonance curve. Resonant points are then compared to the harmonics in the system. If there is coincidence, the technique of de-tuning is applied to overcome overlapping and to choose the capacitor size. For utilities to maintain system efficiencies at acceptable levels, they encourage end-users to use a capacitor size so that the power factor has a value greater than 0.9 and as a rule of thumb, correction is not done to unity. This traditional technique is subjective and lacks decision structure. A new three-stage decision theory process for making a harmonic resonance mitigation decision in an end-user plant is developed. Two new indices are developed to assist in making the decision. The first index assesses the severity of resonance and the second is used to make a mitigation decision. In Stage 1, a quantitative model is developed to structure and represent the decision problem with the harmonic resonance severity index as the objective function. The model uses a fixed capacitor based on full load rating as this represents the worst case. In Stage 2, Utility Theory is used as the decision criterion to select the most desirable capacitor size. In Stage 3, the mitigation index is applied to assess if mitigation is needed or not for the chosen capacitor. Three case studies, based on deterministic models are conducted and they demonstrate the effectiveness of this newly developed decision theory process.
- ItemOpen AccessPower system harmonic field measurements PC simulations and standards(1996) Atkinson-Hope, Gary; Petroianu, AlexanderThe research covered three main objectives: Application of PC based harmonic penetration packages and a comparison of their simulation results. Investigation and comparison of the IEEE, IEC and ESKOM power system harmonic standards. Measurement of harmonics in two industrial networks and the application of the results to the regulatory limits provided by the standards. The research makes use of two packages and uses parameters from an industrial network. Case studies were conducted using the same parameters so that the results obtained from each package could be compared. The standards have been individually investigated to determine each method for controlling harmonic distortion. The three standards have also been compared. Harmonic field measurements were conducted in industrial networks so that the limits imposed by the standards could be compared with real life operating conditions.