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This paper describes a prototype expert system to determine a viable power system voltage stability control scheme. A new model for generator buses reaching their limits of reactive power output is presented. This expert system is designed to assist the power system operator in taking the most appropriate VAr control action in a timely fashion. Sensitivity of a fast voltage stability indicator is used to correct power system voltage stability limit violations. Results of tests conducted on the AEP57 bus and 118 bus IEEE test systems, are presented and discussed.

Transmission congestions limit market activities, cause reliability and security problems. To increase the transfer capacity of a corridor, the conventional approach has been to compensate the corridor to the extent possible and to support the voltage through the use of appropriately positioned reactive or VAr compensation. Achieving full control of the power flow on the power grid requires that the impedance of the power lines or the phase angle of the voltage across individual power lines be made variable and controllable. The paper investigates smart alternatives to this problem.

The objective of this paper is to investigate the asymmetric approach for increasing the transfer capacity of a corridor affected by single-phase faults. The paper consists of a comparative study of symmetric and asymmetric operations for a corridor with N parallel lines. The basis of the comparison is the reactive compensation required to restore the initial power flow following one or several contingencies. An economic analysis is presented for each case analyzed. The paper also aims at determining the operating conditions and criteria of analysis favorable to the asymmetric operation.

Microcystic meningiomas are defined by large vacuolated and stellate shaped cells. We recently examined a microcystic meningioma mimicking a malignant tumor on computed tomography (CT). The aim of the current study was to compare the radiological features of microcystic meningiomas with their histological patterns.We have diagnosed 7 intracranial microcystic meningiomas among 204 meningiomas registered in the files of our Department of Pathology from 1994 to 2001. All CT scans performed before surgery were reviewed.Three of the microcystic meningiomas appeared as entirely microcystic tumors. Two of them were homogeneously hypodense or isodense on CT scan. The third mening was heterogeneous, containing some blood. The histologic pattern of the 4 other meningiomas showed microcystic tumor cells associated with meningothelial or fibrous tumor cells. These meningiomas were heterogeneous on CT scan. All meningiomas seemed to be connected to the dura mater. Three tumors were strongly and homogeneously enhanced after contrast media injection while 3 others were heterogeneously enhanced. No enhanced CT scan was available for 1 case. Astrocytomas were incorrectly diagnosed by CT scan in the 3 heterogeneously enhanced tumors. Meningiomas were correctly diagnosed in the 3 strongly enhanced tumors.The presence of microcystic tumour cells in meningiomas often results in erroneous diagnosis on CT scan, particularly for those which are heterogeneously enhanced. In these cases, a diagnosis of astrocytoma is often made.

This paper presents an integrated intelligent power system global controller. The developed system consists of three different knowledge bases. The tasks are voltage regulation, transmission line overload alleviation, and correction for steady state voltage stability. The base of the correction for the entire global controller is the analysis and use of the sensitivities of the power system variables to the existing VAr control tools. Results of tests conducted on a 6 bus test system and on a 118 bus IEEE test system have shown fast responses and effective corrective actions for the three paths.