Probabilistic low voltage distribution network design for aggregated light industrial loads
- Authors: Van Rhyn, Pierre
- Date: 2015-02-25
- Subjects: Electric power systems - Load dispatching , Electric power-plants - Load , Low voltage integrated circuits , Low voltage integrated circuits - Design and construction
- Type: Thesis
- Identifier: uj:13347 , http://hdl.handle.net/10210/13361
- Description: D.Ing. , This thesis initially reviews current empirical and probabilistic electrical load models available to distribution design engineers today to calculate voltage regulation levels in low voltage residential, commercial and light industrial consumer networks. Although both empirical and probabilistic techniques have extensively been used for residential consumers in recent years, it has been concluded that commercial and light industrial consumer loads have not been a focus area of probabilistic load study for purposes of low voltage feeder design. However, traditional empirical techniques, which include adjustments for diversity to accommodate non-coincidental electrical loading conditions, have generally been found to be applied using in-house design directives with only a few international publications attempting to address the problem. This work defines the light industrial group of consumers in accordance with its international Standard Industrial Classification (SIC) and presents case studies on a small group of three different types of light industrial sub-classes, It is proposed and proved that the electrical load models can satisfactorily be described as beta-distributed load current models at the instant of group or individual maximum power demand on typical characteristic 24-hour load cycles. Characteristic mean load profiles were obtained by recording repetitive daily loading of different sub-classes, ensuring adequate sample size at all times. Probabilistic modelling of light industrial loads using beta-distributed load current at maximum demand is a new innovation in the modelling of light industrial loads. This work is further -complemented by the development of a new probabilistic summation algorithm in spreadsheet format. This algorithm adds any selected number of characteristic load current profiles, adjusted for scale, power factor, and load current imbalance, and identifies the combined instant of group or system maximum demand. This spreadsheet also calculates the characteristic beta pdf parameters per phase describing the spread and profile of the combined system loading at maximum demand. These parameters are then conveniently used as input values to existing probabilistic voltage regulation algorithms to calculate voltage regulation in single-, bi- and three-phase low voltage distribution networks.
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Some cost implications of electric power factor correction and load management
- Authors: Visser, Hercules
- Date: 2012-08-13
- Subjects: Electric utilities - Costs , Electric power systems - Load dispatching , Electric power-plants - Load , Eskom (Firm)
- Type: Thesis
- Identifier: uj:8989 , http://hdl.handle.net/10210/5458
- Description: M. Phil. , Presently, ESKOM is rated as the fifth largest utility in the world that generates and distributes electricity power to their consumers at the lowest price per kilowatt-hour (kW.h). As a utility, ESKOM is the largest supplier of electrical energy in South Africa and is currently generating and distributing on demand to approximately 3000 consumers. This represents 92% of the South African market. ESKOM was selected as the utility supplying electrical energy for the purpose of this study. ESKOM's objective is to provide the means and systems by which the consumer can be satisfied with electricity at the most cost-effective manner. In order to integrate the consumers into these objectives, ESKOM took a decision in 1994 to change the supply tariff from active power (kW) to apparent power (kVA) for a number of reasons: To establish a structure whereby the utility and the consumer can control the utilisation of electrical power supply to the consumer. To utilise demand and control through power factor correction and implementation of load management systems. To identify some cost implications of electrical power factor correction and load management. Consumers with kW maximum demand tariff options had little or no financial incentives to improve their low power factor (PF) by reducing their reactive current supply. Switching to (kVA) maximum demand will involve steps to be taken to ensure that the reactive component is kept to a minimum with maximum power factor. ESKOM has structured various tariff rates and charges with unique features that would accommodate the consumers in their demand side management and load cost requirements, which, when applied, will result in an efficient and cost effective load profile. These tariffs are designed to guide consumers automatically into an efficient way of using electrical power, as it is designed to recover both the capital investment and the operating cost within two to three years after installation of power factor correction equipment. ESKOM's concept of Time-of-use (TOU) periods for peak, standard and off-peak times during week, Saturday and Sunday periods is discussed as load management. Interruptible loads can be scheduled or shed to suit lower tariff rates and to avoid maximum demand charge. The concept of load management will change the operation pattern of the consumer's electricity demand whereby the consumer will have immediate technical and financial benefits. In the last chapter of this dissertation, a hypothetical case study addresses and concludes on some of the technical and cost implications of electrical power factor correction and load management as a successful and profitable solution to optimize electrical power supply to the consumer. By implementing the above, ESKOM ensures that the consumer utilizes the electrical power supply to its optimum level at the lowest cost per kilowatthour (kW.h) generated.
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Electric load forecasting for holiday periods
- Authors: Godden, Kieran Richard
- Date: 2012-08-22
- Subjects: Electric power-plants - Load , Electric power systems - Load dispatching , Forecasting - Statistical methods , Electric power supplies to apparatus
- Type: Mini-Dissertation
- Identifier: uj:3015 , http://hdl.handle.net/10210/6437
- Description: M.Sc. , The Christmas and Easter holiday periods have a large influence on electricity load. Forecasting the load for these periods is difficult since the changes in the load patterns are sudden and substantial. Furthermore, the effects of these periods on the load patterns are dependent on the timing of Easter and the weekday composition of Christmas, which change from year to year. A strategy is presented to forecast the hourly electricity load for these holiday periods as well as the periods shortly afterward. This strategy is based on a general fixed structure ARIMA model developed to forecast the hourly load for periods with no unusual load activity. The general model is supplemented by information on the two holiday periods, extracted from the corresponding periods in historical years by means of growth independent scale factors. A model for forecasting the total weekly load is also presented. This model makes use of intervention techniques to account for the changes in the load due to the Christmas and Easter holiday periods. The forecasting methodologies are all geared towards practical application and are suitable for on-line implementation.
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