V. Gerez

Development of a Monte Carlo based aggregate model for residential electric water heater loads

A model for a residential electric water heater load is developed using an energy flow analysis of the water heater tank. An aggregate model for residential electric water heater loads is then developed using a rejection type Monte Carlo simulation technique. The resultant aggregate model is then used to assess the effectiveness of several demand-side management strategies using the water heater load profile presented in a previous analysis.

Simplified equations for mesh and step voltages in an AC substation

A large number of grounding grids in substations have shapes other than a square or a rectangle, whereas the simplified formulas for mesh and step voltages available in the literature are derived for square or rectangular grids. Improvements in the simplified equations for determining mesh and step voltages are presented. With the modified simple equations, mesh and step voltages at a substation of any practical shape can be estimated with reasonable accuracy. The results obtained with the improved equations have been compared with accurate results obtained via computer. The error in the values obtained with the derived equations is within 16% for mesh voltage and less than 30% for step voltage. >

Evaluation of ground resistance of a grounding grid of any shape

A large number of grounding grids in substations have shapes other than a square or a rectangle, whereas the formulas and graphs for the ground resistance of a grounding grid available in the literature are applicable only to nearly square or rectangular grids. A new simple equation for the estimation of ground resistance applicable to any practical shape of the grid is presented. The results obtained with this equation have been compared with accurate results obtained via computer and with the results of analog model tests. The value of ground resistance obtained with the proposed method closely approximates that obtained from elaborate and time-consuming computer methods. >

Development and validation of a physically-based computer model for predicting winter electric heating loads

This paper presents the development and validation of a physically-based computer model for predicting electric heating loads on distribution feeders. A practical method of obtaining model parameter values is given. Simulation results are given and compared with actual electric utility data from a distribution feeder in a residential area. The proposed model has been found to be useful for predicting the magnitude of the utility line currents associated with the cold load pickup of heating loads as well as for load management and load forecasting purposes. >

Ground resistance of the foot in substation yards

Equations and graphs given in IEEE Std 80 to determine ground resistance are not accurate and give conservative results. More accurate equations and graphs for determining the ground resistance of the human foot in a substation with a thin surface layer of gravel are given. An analysis has been made for models of the foot. In one model the foot is represented by an equivalent circular plate and in the other by an equivalent rectangular plate. Results obtained with these two models and with the IEEE Std 80 method are compared. >

Reduction factor for the ground resistance of the foot in substation yards

Limited thickness of the surface layer of gravel in a substation yard decreases the ground resistance of the foot from its value for the infinite thickness of the surface layer, by reduction factor C. The foot is usually represented by an equivalent circular plate of radius 8 cm. This paper presents method and equations to accurately determine the reduction factor for the circular plate. The equations are valid for any depth of the upper layer. The data is presented in the form of graphs. A simple empirical equation for determining the value of C is also presented. >

Equivalent resistivity of non-uniform soil for grounding grid design

This paper develops a method to determine the equivalent resistivity of heterogeneous soils to be used in the available expressions for uniform soils employed to calculate the ground resistance, mesh and step voltages of substation grounding grids. The results obtained with the proposed equivalent resistivity are compared with the results obtained from the two layer and the multilayer models of the soil and with the results from a computer program, developed by the authors, directly based on the potential produced by a point source in heterogeneous soil. >

Effective ground resistance of the human feet in high voltage switchyards

The ground resistance of the feet, which is an important factor that determines the current flow in the body of a person exposed to dangerous touch voltage in a high-voltage switchyard, is modified by the proximity of the two feet and the presence of the energized grounding grid below the feet. Based on the Thevenin approach, a general method for determining the effective ground resistance of the feet that takes into account the modifying factors is presented. The method is verified with the help of analog model study. Results show that in most practical situations the effect of the modifying factors can be ignored. The situations in which it is necessary to consider these factors are identified. >

Finite expression and models for footing resistance in substations

Footing resistance in a substation is affected by the limited crushed rock layer usually spread on the surface of the soil. A finite expression for calculation of the footing resistance is given. Two simple and fairly accurate models for determining the footing resistance are developed. The results obtained from the finite expression and the models are compared with the accurate results obtained from the infinite summation series. A method to calculate the decrease in footing resistance because of the accumulation of dirt at the lower portion of the crushed rock layer in old substations is also presented. >

Power engineering program at Montana State University: planning, financing, promotion and implementation

An approach to update Montana State Universitys power engineering program is reported. The assessment of the need for such a program, the criteria under which it was developed, and the updated program are described. An affiliation plan to share power engineerings cost with industry and guarantee affiliates well-trained professionals, is presented. The program is structured to guarantee close working relations with industry and to offer solutions to specific power problems by faculty and students. The promotion and implementation of this program are described. >