This paper discusses cable modeling for long highvoltage ac underground cables. In investigating the possibility of using long cables instead of overhead lines, the simulation results must be trustworthy. Therefore, model validation is of great importance. This paper gives a benchmark case for measurements on a 400-kV cable system with cross-bonded sheaths. This paper describes in detail the modeling procedure for the cable system and compares simulation results with the transient field test results. It is shown that although the main characteristics of the waveforms are well reproduced in the initial transient, there are significant deviations between the simulation and measurement results. An analysis indicates that the main cause for the deviation is inadequate representation of the current distribution on conductors since the modeling approach does not take proximity effects into account. The measurement results can be received by contacting the first author of this paper.
Abstract--This paper is concerned with the development of a fast computational methodology for dynamical estimation of the temperature in transmission cables solely based on current measurements and an enhanced version of the lumped parameters model, also denoted thermo electric equivalents (TEE). It is found that the calculated temperature estimations are fairly accurate -within 1.5 o C of the finite element method (FEM) simulation to which it is compared -both when looking at the temperature profile (time dependent) and the temperature distribution (geometric dependent). The methodology moreover enables real time emergency ratings, such that the transmission system operator can make well-founded decisions during faults. Hereunder is included the capability of producing high resolution loadability vs. time schedules within few minutes, such that the TSO can safely control the system.
IndexTerms--Cables, transmission lines, dynamic temperature control, finite element methods, temperature prediction methods.
With the increasing use of high-voltage AC cables at transmission levels, phenomena such as current zero-missing start to appear more often in transmission systems. Zero-missing phenomenon can occur when energizing cable lines with shunt reactors. This may considerably delay the opening of the circuit breaker, leaving the system unprotected and vulnerable to failures. Methods to prevent zero-missing phenomenon are still being studied and compared in order to identify effective countermeasures. This paper contributes to these efforts, by presenting several countermeasures that can be applied to reduce the hazards of zero-missing phenomenon. The authors discovered that this phenomenon can be eliminated, merely by using an extra circuit breaker or a preinsertion resistor.
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