Search

Declining extraction costs and process efficiencies have incented the revival of the oil and gas sector postrecession. The application of drilling rigs has been done more efficiently. These loads are very large, temporary in nature, and mobile. The drilling of each well can be done as quickly as a few hours and typically not more than a few days. These massive loads are complex to own, maintain, and operate, as a result few specialized drillers share the market. Because of the requirements for variable speed and control, drilling rigs are driven by variable frequency drives (VFDs), which are in their clear majority of older technologies such as six-pulse thyristor bridge or SCR-driven motors. These technologies are known to impose steep ramp rates (up and down) as well as rich harmonic content and variable, typically low, power factor. Furthermore, the locations of drilling rigs are typically remote, where distribution systems, if present, are weak, which lead to large background voltage distortions when such loads are present. This paper presents measurements, simulations, and analytical assessments of the characteristics and effects of harmonics and interharmonics (IHs) generated by top-drive and mud-pump VFDs in a large drilling rig operated in Alberta, Canada. Measurement results reveal very high harmonic and IH generation. To further refine the impact assessment of these harmonic emissions, the harmonic attenuation effect of the VFDs is quantified to avoid overestimating the harmonic generation of the loads. The thermal impact of the current harmonics on the coupling transformer is also quantified. [ABSTRACT FROM AUTHOR]

The Alberta Interconnected Electric System (AlES) forms a single integrated transmission network serving the Province of Alberta, Canada. A number of large critical industrial loads are served by the AlES. These loads operate 24 h a day and seven days a week. This paper deals with a critical industrial load which is normally supplied by the Alberta provincial grid through two 72-ky lines. This load also maintains a backup generation system consisting of a set of gas turbines to meet its operating demands in the case of Alberta grid failure. The basic objective of this paper is to derive the optimal number of gas turbines that this critical load should maintain in order to satisfy the plant's reliability criteria in the case of grid failure for continuity of its operation. A Monte Carlo simulation model is developed to assess the adequacy of the backup gas turbine system, and the results of a series of case studies performed using the developed model are presented in this paper. [ABSTRACT FROM AUTHOR]

Provides information on a study which presented a probabilistic Monte Carlo simulation model for determining generation equivalence to a transmission facility for use in transmission system planning studies in the electric power industry. Information on the supply network of the Alberta Power System; Local area reliability assessment methodology; Input data and assumptions used to assess the reliability improvements; Results and conclusions.