This thesis describes numerical methods for the evaluation of the series impedance matrix and shunt admittance matrix of underground cable systems. In the series impedance matrix, the terms most difficult to compute are the internal impedances of tubular conductors and the earth return impedance. The various formulae for the internal impedance of tubular conductors and for the earth return impedance are, therefore, investigated in detail. Also, a more accurate way of evaluating the elements of the admittance matrix with frequency dependence of the complex permittivity is proposed. Various formulae have been developed for the earth return impedance of buried cables. Using the Pollaczek's formulae as the standard for comparison, the formula of Ametani and approximations proposed by other authors are studied. Mutual impedance between an underground cable and an overhead conductor is studied as well. The internal impedance of a laminated tubular conductor is different from that of a homogeneous tubular conductor. Equations have been derived to evaluate the internal impedances of such laminated tubular conductors. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

This thesis presents a new model to simulate the behaviour of underground cable systems under transient conditions. The new cable model belongs to the class of time-domain, frequency-dependent models, and it is directly compatible with the solution algorithm of the EMTP (Electromagnetic Transients Program). The most important feature of the new model is that it takes into account the frequency dependence of the modal transformation matrices and cable parameters, thus overcoming the main limitation of currently-used transmission line and cable models, which assume that the modal transformation matrices are constant Conceptually, the new model is relatively simple. The system parameters which define the behaviour of an underground cable (namely the modal characteristic admittance matrix, the modal propagation matrix, and the modal transformation matrix), are expressed in closed form by approximating them with rational functions in the frequency domain. Therefore, in the time domain, all numerical convolutions can be expressed recursively. The host transients program (to which the model is interfaced) sees the new model as a constant, real admittance matrix, in parallel with a continuously-updated vector current source. The accurate approximation by rational functions of the modal transformation matrix is possible when its elements are continuous and smooth functions of frequency. Standard eigenvalue/eigenvector algorithms are not well suited for this purpose. Therefore, a new procedure to generate eigenvalues and eigenvectors has been developed. This procedure is based on the Jacobi method, and it produces the desired smooth functions of frequency. This manuscript presents a number of simulations where the performance of the new cable model is compared with exact analytical solutions. These simulations show an excellent agreement between analytical and numerical answers. The effects of not taking into account the frequency dependence of the modal transformation matrices is illustrated with the simulation of a line-to-ground fault on a three-phase cable. The response of the new cable model is also compared with results measured in a field test The new cable model is numerically stable. Its computational speed is comparable to that of frequency-dependent line models with constant transformation matrices. The new cable model is general. Its extension to the simulation of multiple-circuit overhead transmission lines should also be of considerable practical importance. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

No description available.

This thesis was prompted by the belief that local residential streets could be better used and serviced if a common underground structure were provided for all utilities. Such a structure could not only get wiring underground, a desirable aim in itself, but also gather all of the utilities together in a narrow portion of the street. This would free the remainder of the street from the restrictions imposed by the utilities, and allow designers to create more interesting and pleasant environments. It was further believed that such structures might be feasible if the designing and servicing of local streets were considered comprehensively. These beliefs have been investigated by formulating and testing the general hypotheses that installing utilities in specially designed underground structures in local residential streets would: a) permit better use and design of such streets than is possible by current servicing practices; b) be feasible (from functional, physical, social, staging, administrative, political, financial, and economic points of view) if comprehensively designed. The scope of this investigation has been limited to future local streets in single-family residential districts of Metropolitan Vancouver for these reasons. Future streets would allow maximum flexibility in design and savings in servicing costs by proposed practices. Local streets generally have simpler and smaller-sized facilities which are most widely spread. Single-family residential districts are and will be the largest land use and hence, have the most increase in streets. Metropolitan Vancouver has been studied because of its proximity and familiarity to the investigator and its variety of servicing practices. Street use is the use made of streets including such ones as playing not currently facilitated. The 'servicement' is that part of the physical environment created by property service facilities in the streets. Property services are those public services providing service to property as distinct from people. Current practice is the ways of designing and installing facilities followed at the present time. The term 'better' in the first hypothesis is interpreted in terms of elements of the public interest. These include public health, safety, convenience, amenity, welfare, and economy. Criteria of feasibility have been established for the evaluation of the proposed practices. These include functional, physical, social staging, administrative, political, functional, and economic feasibility. They are essentially different ways of looking at a complex problem. [ ... ] / Applied Science, Faculty of / Community and Regional Planning (SCARP), School of / Graduate

Thesis (M. Sc.(Eng.))--University of Hong Kong, 1969. / Mimeographed.

No description available.

Thesis (M.S.)--Ohio University, August, 1989. / Title from PDF t.p.

In this thesis, the finite element method (FEM) is applied to the calculation of frequency-dependent series impedances and shunt capacitances of underground power cables. The principal equations describing the quasi-magnetic fields and static electric fields are solved with FEM based on the Galerkin technique. The Js method and the loss-energy method are derived to calculate the impedances of a multiconductor system from its field solution, and the energy method and the surface charge method are derived to calculate the capacitances. With a single-core (SC) coaxial cable, the suitability of quadratic isoparametric elements and high-order simplex elements are studied, and a suitable division scheme is suggested for the auto-mesh program. The conventional FEM with a field truncation boundary is applied to the impedance calculation of buried SC cables. Suitable locations for the field truncation boundary and division schemes in the earth are studied. The results show that rb ≥ 12[symbol omitted] is required to obtain accurate impedances of shallowly buried cables with the conventional FEM. This requires a large solution region in the earth at low frequencies. A new technique based on the perturbation concept is proposed to reduce the solution region in the earth. Comparisons between the results from the conventional FEM and from the proposed technique with a significantly reduced solution region in the earth show good agreement. In the case studies, the FEM is applied to the parameter calculation of multiphase SC cables, PT cables, sector-shaped cables, and stranded conductors. The numerical results are compared with those from analytical formulas. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

In areas supplied by underground transmission systems load division among several parallel connected cables may not be satisfactory. Phase-angle-connected TCUL transformers may be used to provide the phase shift necessary to equalize the cable loading and to provide voltage regulation at the load. A means for automating the TCUL adjustments to provide satisfactory current balance and voltage regulation was sought. This problem was attacked by first expressing the system performance (the unbalance of cable currents and load voltage magnitude) in terms of a system performance function. An optimal policy of control is defined as the selection of the particular TCUL transformer which provides the greatest improvement in the system performance. A negative gradient optimization routine is used to determine the required adjustment. A derivation of the adjoint network relationships for a phase-angle-connected transformer is given. These relationships provide a means for readily determining the gradient of the performance function. This approach is developed to provide a means for continuously monitoring and automatically controlling the system performance. A discussion of two ways in which this approach might be implemented physically is given. The optimally adjusted TCUL controller was incorporated in a digital computer model of a small underground power system. Simulated operation of the system under widely varying load conditions demonstrated the ability of the controller to maintain very small cable current unbalance while simultaneously holding voltage variations to +2.9 percent of nominal. A significant advantage of this approach is that the optimal sequence of adjustments required to restore the system to a satisfactory level of performance may be obtained and verified without making any actual adjustments to the TCUL transformers. This is important from a maintenance point of view. A possible disadvantage of the method is that an accurate model of the system must be available. / Ph. D.

published_or_final_version / Electrical Engineering / Master / Master of Science in Engineering