Abb Research Ltd.

Abb Technology Ag

Marek Fulczyk

Przemyslaw Balcerek

Murari Mohan Saha

Eugeniusz Rosolowski

Jan Izykowski

Joachim Bertsch

Marian Sobierajski

Tord Bengtsson

Wojciech Piasecki

Stefan G Johansson

Filip Grecki

Sture Lindahl

Magdalena Ostrogorska

Gabriel Olguin

Piotr Pierz

Marcin Szewczyk

Murari Saha

The invention relates to a device for measuring the direct component of alternating current, applicable in current measuring systems where a low direct component of alternating current and a high amplitude of the alternating component of alternating current occur. The device for measuring the direct component of alternating current comprises a current-carrying wire () around which there is located a magnetic core () provided with a gap () in which a magnetic field sensor () with insulated terminals () is located and it comprises a shorted compensating winding () or () which is made in the form of a single turn coil placed on the core ().

Device for measuring the direct component of alternating current

The present invention is concerned with a method for faulted phase selection and fault type determination in electric power lines applicable both to series compensated and uncompensated power lines. The method comprising a fault inception detection and an estimation of fault phase current signals, pre-fault current signals and zero-sequence current in order to receive the absolute value of incremental current signals and their maximum value from which real value indicators for phase to phase faults, real value indicators for 3-phase fault and a real value indicator for ground fault are determined. The method further comprises

Method of fault phase selection and fault type determination

A method for fault location in series compensated power transmission lines using two-end unsynchronized voltage and current measurements in stations A and B. The method includes performing a subroutine I for determining whether the fault occurred in a line section LA between the station A and a SC&MOV and the distance dto the fault from station A. Subroutine II determines whether the fault occurred in a line section LB between the station B and the SC&MOV and the distance dto the fault from station B. The synchronization angle eis determined in subroutine I, and the synchronization angle eis determined in subroutine II. Then, the distance to fault dor dis determined. Finally, an equivalent impedance of compensating banks at fault stageand, and pre-fault stageis calculated in order to determine whether distance dor dis the final result.

Method for fault location on series compensated power transmission lines with two-end unsynchronized measurement

A method is provided for fault location in uncompensated power lines with two-end unsynchronized measurement, finding an application in the power industry and for overhead and overhead-cable transmission or distribution lines. The method according to the invention includes measuring the voltage and currents at both ends (A) and (B) of the section, obtaining the phasor of the positive sequence voltages (V, V) measured at the ends (A) and (B), respectively, obtaining the phasor of the positive sequence currents (I, I) measured at the ends (A) and (B), respectively, determining whether there is a three-phase balanced fault, and using either a first subroutine or a second subroutine (depending on whether or not there is a fault), determining a distance (d) to the fault.

Method for fault location in uncompensated power lines with two-end unsynchronized measurement

A method for locating faults in three-terminal and multi-terminal power lines, applicable in electric power systems for overhead and underground cable transmission and distribution lines. The inventive method is characterized in that it measures current for fault and pre-fault conditions and in one terminal station of the system line phase voltage for fault and pre-fault conditions is measured, a hypothetical fault location is assumed, the distances to the hypothetical fault locations are calculated and fault resistance is calculated, the actual fault point is selected by first comparing the numerical values concerning the distances to the hypothetical fault locations and rejecting those results whose numerical values are negative or bigger than one in relative units, and then by analysing the values of the calculated fault resistances for the fault locations and rejecting those results of the calculations for which the value of fault resistance is negative, and if there is still more than one calculation result remains not rejected then performing selection of the valid result by analysing the values of the calculated respective equivalent source impedances.

Method for fault location in electric power lines

The present invention relates to a ground fault detection arrangement for a synchronous three-phase electrical machine, and an electrical system comprising a ground fault detection arrangement and a synchronous three-phase electrical machine. The ground fault detection arrangement injects an off-nominal frequency voltage between a neutral point of the synchronous three-phase electrical machine and ground and measure resultant currents to detect a ground fault.

Ground fault detection

A method is disclosed for the identification of weak and/or strong nodes of an electric power transmission system. Electric parameters characterizing nodes and branches of an electric power transmission system are subject to computational treatment to obtain equations of power flow in all nodes of the system at assumed 100 percent system load value. Using earth as the reference point, nodal impedance values are computed for all nodes, and used to construct a P-Q curve which presents the functional relation between the system's reactive and active load. The nodal coefficient of voltage stability is determined as the relative distance between the base load point of that node and the critical point on the P-Q curve situated most closely to the base point. The coefficient is compared with a threshold value considered to be a safe margin to maintain voltage stability for a given node.

Method of the identification of weak and/or strong nodes of an electric power system

The subject of the invention is a method of identification of weak and/or strong branches of an electric power transmission system. In the inventive method electrical parameters characterizing the nodes and branches of an electric power transmission system are subjected to computational treatment in order to obtain equations of power flow in all nodes of the system at assumed 100 percent system load value. Then an electric model of a branch is assumed and a curve P-Q is constructed which shows the functional relation between active and reactive load in the system. For the assumed branch model a branch voltage stability coefficient is determined. Then the analysed system is overloaded by increasing the total system load up to 120% base load and the branch voltage stability coefficient is determined again. The numerical values of the appropriately determined coefficients are compared with threshold values considered to be a safe margin for the maintenance of voltage stability for the given branch.

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Kedzierzyn-Kozle, Poland

Marek Fulczyk