Abstract: The present invention is concerned with a method of distance protection of parallel transmission lines applicable both to series compensated and uncompensated electric power lines, using a distance relay. The method is characterized in that a pair of flags (ff1, ff2) are calculated for indication faulted and healthy circuits in parallel lines and in the same time a flag (Internal_Fault) for indication internal or external fault in parallel lines is calculated independently. Next gathering all calculated flags (ff1, ff2, Internal_Fault) an analyze of the value of these flags are performed and depending on the values of flags (ff1, ff2, Internal_Fault) and on their reciprocal relationship, a trip permission signal from the protection relay (4) is released and sent to the alarms devices or to the line breakers, or a block signal from the protection relay (4) is generated and sent to protect parallel lines before damage.

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: The present invention is concerned with a method of distance protection of parallel transmission lines applicable both to series compensated and uncompensated electric power lines, using a distance relay. The method is characterized in that a pair of flags (ff1, ff2) are calculated for indication faulted and healthy circuits in parallel lines and in the same time a flag (Internal_Fault) for indication internal or external fault in parallel lines is calculated independently. Next gathering all calculated flags (ff1, ff2, Internal_Fault) an analyze of the value of these flags are performed and depending on the values of flags (ff1, ff2, Internal_Fault) and on their reciprocal relationship, a trip permission signal from the protection relay (4) is released and sent to the alarms devices or to the line breakers, or a block signal from the protection relay (4) is generated and sent to protect parallel lines before damage.

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: The subject of the invention is a method of subsynchronous resonance detection in electrical power systems with series capacitors. Voltage signals are measured on line and by using finding zero crossing points of discrete signal of measured voltage, positive and negative half cycles of the wave form of discrete signal of voltage are calculated in a computer device to which constant parameters are delivered by the user.

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: 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.