"Optimal Design Of Coal-Mine Power Systems." by Mir Masood-Ul Hassan

Date of Graduation

1979

Document Type

Dissertation

Degree Type

PhD

Abstract

Many accidents and fatalities in underground coal mines are caused by inadequately designed electrical power systems. These incidents can be significantly reduced if coal-mine power systems are designed strictly according to IEEE, NEMA, and ANSI standards.

The objective of this research is to develop techniques and comprehensive computer software for the optimal design of coal-mine power systems. This aims to achieve the highest degree of safety, reliability, and performance at minimal capital cost.

It was found that mine power systems are generally voltage drop-limited, and the primary distribution cables need to be underrated by various factors to achieve the desired voltage drop. Based on this, a procedure for the optimal selection of primary distribution voltage is presented. The voltage levels considered include 4160 V, 7200 V, and 12470 V.

Once the voltage levels are determined, the network components (cables, transformers, etc.) are selected based on mining requirements. Methods are developed to select trailing cables for cyclically varying loads (such as a continuous miner) using a steady-state thermal model. Additionally, the design of the DC track haulage system is analyzed in detail. The economics of using power-factor correction capacitors is also discussed.

After selecting all major system components, it is logical to analyze them as a system to ensure that all operating constraints are satisfied. To achieve this, an algorithm for the load-flow analysis of AC/DC distribution systems is developed. This includes adequate modeling of the rectifier, formation of suitable equations for the AC and DC systems along with appropriate boundary conditions, and development of a solution technique for the resulting nonlinear problem.

The same nonlinear rectifier model is used for analyzing faults on the DC system, considering both bolted and arcing faults. A program is also developed to achieve time-current coordination of various protective devices such as relays and fuses.

Finally, different network topologies (e.g., expanded radial, primary loop, etc.) are compared based on their reliability, availability, and applicability for coal-mine power distribution.

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