Abstract: 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 (1) around which there is located a magnetic core (2) provided with a gap (3) in which a magnetic field sensor (4) with insulated terminals (5) is located and it comprises a shorted compensating winding (6) or (9) which is made in the form of a single turn coil placed on the core (2).

Abstract: 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 calculating the maximum of the value of all fault type indicators (Fflt), determining the fault type, which determines the fault type on the basis that the index (flt) means the specific type of fault indicated by the value of flt; and presenting the real fault type indicator (Fmax).

Abstract: 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 dA to 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 dB to the fault from station B. The synchronization angle ej?A is determined in subroutine I, and the synchronization angle ej?B is determined in subroutine II. Then, the distance to fault dA or dB is determined. Finally, an equivalent impedance of compensating banks at fault stage ZSC1—phSUB—A and ZSC1—phSUB—B, and pre-fault stage ZSC1—pre is calculated in order to determine whether distance dA or dB is the final result.

Abstract: 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 (1) around which there is located a magnetic core (2) provided with a gap (3) in which a magnetic field sensor (4) with insulated terminals (5) is located and it comprises a shorted compensating winding (6) or (9) which is made in the form of a single turn coil placed on the core (2).

Abstract: 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 (VA1, VB1) measured at the ends (A) and (B), respectively, obtaining the phasor of the positive sequence currents (IA1, IB1) 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.

Abstract: 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 calculating the maximum of the value of all fault type indicators (Fflt) determining the fault type, which determines the fault type on the basis that the index (flt) means the specific type of fault indicated by the value of flt; and presenting the real fault type indicator (Fmax).

Abstract: 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.

Abstract: The present invention is concerned with a method for fault location in series compensated power transmission lines with two-end unsynchronized measurement, finding an application in the electrical power sector and for overhead uncompensated and series-compensated transmission lines.

Abstract: 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 (VA1, VB1) measured at the ends (A) and (B), respectively, obtaining the phasor of the positive sequence currents (IA1, IB1) 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: The subject of the invention is a method of identification of weak and/or strong branches of an electric power transmission system.

Abstract: The subject of the invention is a method for the identification of weak and/or strong nodes of an electric power transmission system.