Patents by Inventor Zoran Gajic

Zoran Gajic has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Publication number: 20100202092
    Abstract: A differential protection method in a power network for determining type of fault occurring within the power network. The power network includes a protected object having two or more ends, and a current differential protection device and a current transformer are arranged at each end. The method includes the steps obtaining, at a first end of the protected object, measured values from a second end of the protected object; comparing, at the first end, changes in measured values taken at the first end with changes in the measured values obtained from the second end; and determining, upon the step of comparing changes in measured values showing differing results, type of fault occurring within the power network.
    Type: Application
    Filed: April 20, 2010
    Publication date: August 12, 2010
    Inventors: Zoran Gajic, Bertil Lundqvist
  • Patent number: 7710698
    Abstract: A protective relay for an electrical power distribution system and a method. The protective relay includes first and second current transformers arranged to sense a respective current flowing into a power line, and a voltage sensing device arranged to sense the voltage of the power line. The protective relay further includes a first and a second device for determining the direction of a fault within the system based on a current signal from the first and second current transformers and a voltage signal from the voltage sensing means. The protective relay further includes a third device for determining the fault direction based on a sum of the current signals from the first and second current transformers and a voltage signal from said voltage sensing means. A controller determines whether a fault is internal or external based on the fault directions determined by the first, second and third devices.
    Type: Grant
    Filed: June 29, 2007
    Date of Patent: May 4, 2010
    Assignee: ABB Technology Ltd.
    Inventors: Zoran Gajic, Torbjörn Einarsson, Sethuraman Ganesan
  • Publication number: 20090059447
    Abstract: A method and a device for fault detection in an n-winding, three-phase power transformer. For each of the windings (Wi) the three phase currents (IL1—Wi; IL2—Wi; IL3—Wi) are measured. For each of the windings (Wi) deciding if a zero sequence current (I0—Wi) reduction is to be performed depending on at least one user setting (kWi) and if so, deducting the zero sequence current (I0—Wi) from each of the three phase currents (IL1—Wi; IL2—Wi; IL3—Wi). For each of the windings (Wi) generating normalized currents by performing a magnitude compensation and a phase angle shift compensation on the results of the previous step. For each of the three phases (Lx) comparing the normalized current of a single winding with the normalized currents of all other windings. For each phase (Lx) generating a fault signal, if a difference between the single winding (W1) and all other windings (W2, . . . , Wn) exceeds a predefined level.
    Type: Application
    Filed: August 24, 2006
    Publication date: March 5, 2009
    Applicant: ABB TECHNOLOGY LTD
    Inventor: Zoran Gajic
  • Publication number: 20080130179
    Abstract: A method for fault detection in a power transformer/autotransformer and/or interconnected power lines, which are within the zone protected by the differential protection, and particularly suitable for detecting turn-to-turn faults in power transformer/autotransformer windings. All individual instantaneous phase currents of the protected object are measured, individual phase currents as fundamental frequency phasors are calculated, the contributions of the individual protected object sides negative sequence currents to the total negative sequence differential current are calculated by compensating for the phase shift of an eventual power transformer within the protected zone, the relative positions of the compensated individual sides negative sequence currents in the complex plane are compared, in order to determine whether the source of the negative sequence currents, i.e.
    Type: Application
    Filed: December 22, 2004
    Publication date: June 5, 2008
    Applicant: ABB AB
    Inventors: Zoran Gajic, Ivo Brncic
  • Publication number: 20080036559
    Abstract: A protective relay for an electrical power distribution system and a method. The protective relay includes first and second current transformers arranged to sense a respective current flowing into a power line, and a voltage sensing device arranged to sense the voltage of the power line. The protective relay further includes a first and a second device for determining the direction of a fault within the system based on a current signal from the first and second current transformers and a voltage signal from the voltage sensing means. The protective relay further includes a third device for determining the fault direction based on a sum of the current signals from the first and second current transformers and a voltage signal from said voltage sensing means. A controller determines whether a fault is internal or external based on the fault directions determined by the first, second and third devices.
    Type: Application
    Filed: June 29, 2007
    Publication date: February 14, 2008
    Applicant: ABB Technology Ltd.
    Inventors: Zoran Gajic, Torbjorn Einarsson, Sethuraman Ganesan
  • Patent number: 7002784
    Abstract: The present invention relates to a method for current compensation of a protection system for protecting a zone in a power system, which zone comprises a number of transmission lines connected to power sources and a number of transmission lines connected to a number of loads where the power sources and the loads are arranged outside the zone and a number of current transformers (CT) arranged to the transmission lines, wherein the method comprises the steps of continuously measuring all the incoming currents (Iin) to the zone, continuously measuring all the outgoing currents (Iout) from the zone, continuously calculating the differential current (Id) according to Id=Iin?Iout, continuously calculating q=Iout/Iin, continuously comparing q with set values and continuously comparing Iout with a set value Set1.
    Type: Grant
    Filed: July 11, 2001
    Date of Patent: February 21, 2006
    Assignee: ABB AB
    Inventors: Jianping Wang, Zoran Gajic, Mikael Goransson
  • Publication number: 20050239489
    Abstract: The present invention relates to a method and system for closed loop power control in a mobile communication system. Error is determined between a target signal-to-interference (SIR) and a received SIR. A power control scheme at a power controller of a base station determines a power change that is proportional to the error. Gain of the power controller is selected to achieve minimum error at a subsequent time instant.
    Type: Application
    Filed: February 11, 2005
    Publication date: October 27, 2005
    Inventors: Lijun Qian, Zoran Gajic
  • Patent number: 6944470
    Abstract: A system for closed loop power control in a mobile communication system comprises error determination process for determining an error between a target SIR and a received SIR (12, 14) and a power control scheme for determining a power change associated with error (18). As a result, the system controls the gain of power transmission (19) in order to achieve minimum error at a subsequent time instant.
    Type: Grant
    Filed: April 6, 2001
    Date of Patent: September 13, 2005
    Inventors: Lijun Qian, Zoran Gajic
  • Publication number: 20040090728
    Abstract: The present invention relates to a method for current compensation of a protection system for protecting a zone in a power system, which zone comprises a number of transmission lines connected to power sources and a number of transmission lines connected to a number of loads where the power sources and the loads are arranged outside the zone and a number of current transformers (CT) arranged to the transmission lines, wherein the method comprises the steps of continuously measuring all the incoming currents (Iin) to the zone, continuously measuring all the outgoing currents (Iout) from the zone, continuously calculating the differential current (Id) according to Id=Iin−Iout, continuously calculating q=Iout/Iin, continuously comparing q with set values and continuously comparing Iout with a set value Set1.
    Type: Application
    Filed: June 26, 2003
    Publication date: May 13, 2004
    Inventors: Jianping Wang, Zoran Gajic, Mikael Goransson
  • Publication number: 20030166407
    Abstract: A system for closed loop power control in a mobile communication system comprises error determination process for determining an error between a target SIR and a received SIR (12, 14) and a power control scheme for determining a power change associated with error (18). As a result, the system controls the gain of power transmission (19) in order to achieve minimum error at a subsequent time instant.
    Type: Application
    Filed: March 7, 2003
    Publication date: September 4, 2003
    Inventors: Lijun Qian, Zoran Gajic
  • Publication number: 20030107381
    Abstract: The present invention relates to a method for protecting a zone in a power system, which zone comprises a number of transmission lines connected to power sources and a number of transmission lines connected to a number of loads where the power sources and the loads are arranged outside the zone, wherein the method comprises the steps of: continuously measuring all the incoming currents (Iin) to the zone, continuously measuring all the outgoing currents (Iout) from the zone, and continuously calculating the differential current (Id) according to Id=Iin−Iout. The method is characterised in continuously integrating Iin, Iout and Id according to Formula (I), where T is the fundamental frequency cycle, whereby changes of the continuously integrated values I?IN?, IOUT and ID constitute indications of whether faults on the power system occur within or outside the zone. The present invention also relates to a device and computer program product for performing the method.
    Type: Application
    Filed: October 15, 2002
    Publication date: June 12, 2003
    Inventors: Jianping Wang, Zoran Gajic, Mikael Goransson