I.O. Habiballah

Underground cable magnetic field simulation and management using new design configurations

This paper addresses one of the most important sources of magnetic fields: underground power cables. New design configurations for one, two, three and four cables per phase are presented from a magnetic field perspective. Different management techniques are studied in detail. Judicious placement of cable phases in multiconductor lines to reduce the field effect is implemented by computer modeling and simulations. The state-of-the-art magnetic field simulation package PCFIELD developed by EPRI is used to quantify and present the tool used to manage the field values. The new design configuration cases are very useful from a magnetic field point of view and have low cost schemes that can be easily implemented.

Implementation of shielding principles for magnetic field management of power cables

Adverse health effects due to magnetic fields is a matter of great concern and has been widely debated in recent years. Managing these fields is a challenge to researchers. One of the important sources of magnetic fields is power cables. Different management techniques have been studied. In this paper, passive shielding schemes are implemented to manage the magnetic fields of power cables. The various shielding schemes can be separated into two broad categories: shielding subject and shielding source. Both schemes are implemented in this paper. Passive shielding schemes are found to be the most powerful technique as the reductions obtained are sometimes as high as 97-98%. This scheme is a costly one, should be used only in assigned locations, and as such, there has to be a trade-off between the cost and the level for reduction desired and the health desired and the health hazards.

Magnetic field management techniques in transmission underground cables

Magnetic field management is concerned with the minimization of the effects of such fields on the public health, without sacrificing the effectiveness or reliability of the power system. The essential management techniques used for the underground transmission cables comprise geometry manipulation phase placement, and source shielding. In this paper, the simulation results of the standard recommended stack, triangular and flat configurations are presented. The simulations have been carried out for single and three phase cables. The resulting fields for different depths have been evaluated and compared. The results led to the conclusion that judicious placement of phases is a very powerful management technique to reduce the magnetic field as cost has not been changed. The appropriate phase placements corresponding to minimal field values are obtained.

Multipartitioning of power system state estimation networks using simulated annealing

This paper presents the development of an algorithm to multipartition an observable power system state estimation (PSSE) network into two or more observable subnetworks. The partitioning algorithm is based on using the simulated annealing principle which has a theoretical basis in combinatorial optimization, rather than a heuristic derivation. Computational examples, using several power networks, are given to illustrate the properties of the proposed algorithm.

Markov chains for multipartitioning large power system state estimation networks

This paper presents a new and efficient algorithm for multipartitioning an observable power system state estimation network into observable subnetworks. The partitioning algorithm, which uses the spanning tree of an observable network, is based on Markov chains and has a stochastic basis, rather than a heuristic derivation. This algorithm is faster and provides all the possible optimal partitions of a spanning tree. Once the spanning tree is optimally partitioned into full rank subspanning trees, the interconnected lines between the partitioned subnetworks can be obtained directly from the original network. Computational examples using large power networks are given, to illustrate the properties of the proposed algorithm.

Exact-decoupled rectangular-coordinates state estimation with efficient data structure management

The authors deal with the solution of power system estimate problems using node voltages in rectangular coordinates. The Jacobian matrix is diagonalized, and the mismatching vector is modified following the ideas proposed by other investigators for decoupling the Jacobian matrix when using polar coordinates. The proposed method decouples the Jacobian matrix into real and reactive-power submatrices, which are evaluated only once at the beginning of the process. An efficient data structure management technique is presented to improve the computational process. The performances of these techniques are evaluated using several power system networks. The proposed rectangular-coordinate technique is compared with the Newton-Raphson method and a polar coordinate method. The proposed data-storing method is compared with a standard technique. >

ELF Electric and Magnetic Fields Exposure Assessment of Live-Line Workers for 132 kV Transmission Line of SEC

This paper presents an exposure assessment study for live-line workers exposed to transmission line power frequency electric and magnetic fields. A double circuit transmission line is selected. Practical exposure scenarios which represent actual working conditions for live-line workers have been identified. The charge simulation method has been adopted to compute the external electric field around the selected 132 kV transmission line. A method based on Ampere law has been chosen to compute the external magnetic field around the transmission line. Both methods are numerically solved using the EPRFs EMF Workstation software. A comparison between the values of external electric and magnetic fields, with the allowable exposure limits set by the international standards has been conducted. The paper concluded that the levels of workers exposures to extremely low frequency electric and magnetic fields are below the recommended international standards limits for the scenarios considered in this work

Efficient treatment of parameter errors in power system state estimation

This paper presents efficient data structure management algorithms to reduce the amount of CPU time required during the recomputational process of updating the Jacobian matrix and mismatching vector for power system state estimation. This updating is required after the identification of bad data, such as a parameter error of a line in a power network, in order to remove their influence on the state estimation process. The performance of the proposed algorithms is evaluated using several large power system networks. A considerable reduction in the CPU time is obtained with the proposed algorithms

Identification and Verification of Hierarchy of DFIG Converter Controls for Power System Damping

Abstract This article employs two decomposition techniques and the residue principles to determine the order of the converter controls of a doubly fed induction generator (DFIG) in terms of providing system damping. The dynamic model of the various components of the DFIG system—the wind turbine, induction generator, converter system, the load and transmission network are derived and 4 converter controls identified. The hierarchy analysis demonstrates that out of 4 converter controls the magnitude of the rotor applied voltage is the most effective one. The finding was verified by simulating the system through both lead-lag as well as proportional-integral (PI) controller designs, the controller parameters being found through the residue principle. Simulation studies on the doubly fed generator system show that both the controller designs provide good damping to the system, the PI control being slightly superior. The controlled rotor voltage was observed to be able to avert voltage collapse in the system arising in the event of severe disturbance conditions.

Organ Dosimetry for a Worker Standing Under a 132 kV Power Line

This paper investigates the induced electric fields and currents in a human body tissues and organs of a live-line worker standing right under the maximum sag-point (mid span) of a double circuit 132 kV transmission line located in Riyadh, Saudi Arabia. The main purpose of this study is to determine, if the electric fields and current densities induced inside the critical tissues of a human body such as brain and heart are within the exposure limits of the IEEE Standards C95.6 - 2002. The double circuit 132-kV, 60 Hz transmission line has a power rating of 293 MVA, a maximum recorded peak load current of 603 A. Charge simulation method and the Biot-Savart law have been adopted for computation of external electric and magnetic fields. Finite Difference Time Difference (FTDT) technique and anatomical human body model with more than 40 different tissues with 3 mm voxel sizes have been utilized to calculate organs internal induced electric field and circulating currents. Simulation indicates that, at 1.75 meter above the ground level and under the maximum sag-point of the 132 kV transmission line, the computed external electric field is 1689 V/m and the external magnetic field is 92 mG. These values are below the limits set by the IEEE Standards for external exposure for the live-line workers. The maximum induced electric fields in the brain and heart are 29.5 and 6.3 mV/m respectively. These values are below the IEEE Standard recommended limits of 53 mV/m for the brain and 943 mV/m for the heart. The maximum induced electric fields for all human tissues, excluding the skin, was at the bone marrow of the feet and is 1.86 V/m. This value is lower than the IEEE Standard limit of 2.1 V/m for extremities. Consequently, a worker standing under the maximum sagpoint of a 132 kV transmission line during the peak loading condition is safe from the short term effects of EMF exposure on human body tissues.