This study presents a new earth-fault detection algorithm for both unearthed and compensated neutral medium-voltage networks. The proposed algorithm is based on the transient estimation of the earth capacitance of the...
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This study presents a new earth-fault detection algorithm for both unearthed and compensated neutral medium-voltage networks. The proposed algorithm is based on the transient estimation of the earth capacitance of the background network during the first one-eighth of the power frequency period. The effects of feeder impedances and the Petersen coil (in compensated networks) are compensated using proposed compensation factors. The estimated capacitance accurately indicates if the feeder is faulted or not. The capacitance can be estimated with a maximum error of +/- 10 %. The algorithm is not reliant on the fault resistance and the faulted feeder parameters;it mainly depends on the background network. The network is simulated using the ATP/EMTP program. Different fault conditions are covered in the simulation process, including different fault inception angles and high fault resistances.
An approach to numerical modelling of temperature distributions around buried power cables using finite element analysis is presented in this paper.-The finite element algorithms are based on time-dependent heat sourc...
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An approach to numerical modelling of temperature distributions around buried power cables using finite element analysis is presented in this paper.-The finite element algorithms are based on time-dependent heat sources of the environment and temperature-dependent material properties of the cables. The nonlinear steady-state and transient heat transfer algorithms are applied to the problem of controlling thermal environment in an actual hot spot of a 110kV cable line installed in Belgrade, Republic of Serbia. Moreover, this paper outlines the influence of an underground heating pipeline on ampacities of the cable line, and two retrofitting procedures for optimising the thermal properties of cable environment. Two suggested procedures for thermal optimisation of the actual hot spot are: the use of a new-mixed corrective backfill and the use of quartz sand. Finally, actual test cases using the measured data indicate the possibilities of using the proposed algorithms. Copyright (C) 2006 John Wiley & Sons, Ltd.
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