Abstract: The invention concerns a method and a system for online ferroresonance detection in a high voltage electrical distribution network. The method includes: Overflux detection (23), which acts as the start element, overflux being set if the flux is greater than a threshold for specified time duration, mode verification (26) which is to recognize the modes of the ferroresonance, a fuzzy logic method being used to discriminate the ferroresonance modes.

Abstract: The invention concerns a method and a system for online ferroresonance detection in a high voltage electrical distribution network. The method includes: Overflux detection (23), which acts as the start element, overflux being set if the flux is greater than a threshold for specified time duration, mode verification (26) which is to recognize the modes of the ferroresonance, a fuzzy logic method being used to discriminate the ferroresonance modes.

Abstract: A method of predicting transient stability of a synchronous generator and a device for implementing such a method, the device comprising measurement means and calculation means for calculating an information which indicates, before it actually happens, whether the generator slip will be greater than zero or not at the critical phase angle.

Abstract: The invention concerns a method of impedance groundfault detection for differential protection of an overhead transmission line in a three-phase high voltage electric power transmission system which comprises many lines (1,12) and many protection relays (2,4), which comprises the following steps: 1) in prefault condition: —measuring the differential current (I); —measuring the phase voltage (II) at the relay location; —measuring the phase current (III) the relay location; —calculating the differential admittance (IV), with the following equation: (formula (V)). With (VI): the positive sequence impedance of the line-protected.

Abstract: A method of initiating the load shedding within an electrical power system comprising an electricity generator with a source impedance ZS and a load impedance ZL, characterized in that the method comprises: measuring the voltage VL at the terminal of the load impedance, calculating by means of a computer a voltage operative level VOP such that: VOP=K VC, where K is a number greater than 1 and VC is a critical voltage at the terminals of the load ZL at which the ratio ZL/ZC is equal to 1, VC depending on the difference ? between the phase angle ?L of the load impedance ZL and the phase angle ?S of the source impedance ZS, and comparing the voltage VL with the voltage operative level VOP so that the load shedding is initiated as soon as VL is equal to VOP.

Abstract: A relay for current differential protection of a transmission line, comprising: a first calculator of symmetrical sequence components of currents of each phase of the transmission line at local and remote ends of the transmission line; a second calculator of phase differences ?12 and ?012 between combinations currents i12 and i012 of the symmetrical sequence currents; a fuzzy inference system which outputs a variable y whose value is calculated according to the values of the phase differences ?12 and ?012; a third calculator which outputs a tripping signal for the control of a circuit breaker arranged on the transmission line and associated with the relay, the value of the tripping signal being calculated according to the values of the variable y and the values of the currents of each phase at the local and remote ends of the protected transmission line.

Abstract: A method and a system for transient and intermittent earth fault detection and direction determination in a three-phase median voltage electric power distribution system which comprises many lines. The system comprises: sampling means wherein the residual current and residual voltage on said lines are sampled, transient direction detection means based on instantaneous power, random intermittent detection means based on intermittent change of residual current amplitude, means of integrating transient direction and random intermittent detection, and alarm means indicating maintenance personnel to check the status of one line.

Abstract: A method of monitoring voltage stability within an electrical power system comprises the steps of establishing a dynamic power system stability margin based on an operating characteristic of the power system; indicating that the power system has become unstable when the dynamic power system stability margin falls below a predetermined value; and initiating dynamic load shedding and/or restoration depending on stability margin.

Abstract: An optical sensor configuration contains an optical current sensor and/or an optical voltage sensor. The sensor configuration further contains a first and a second hollow member, preferably ring shaped profiles, which are together disposed to form a hollow section. The sensor configuration further includes an optical fiber of the current sensor disposed in an annular groove, the groove being disposed at the boundary surface between the first hollow member and the second hollow member, and/or an optical fiber of the voltage sensor is disposed in a recess of the second hollow member. The first hollow member has an annular recess into which the second hollow member is disposed whereas the first hollow member is an L-shaped or U-shaped ring with two legs and the recess is formed between the two legs.

Abstract: A method of monitoring voltage stability within an electrical power system comprises the steps of establishing a dynamic power system stability margin based on an operating characteristic of the power system; indicating that the power system has become unstable when the dynamic power system stability margin falls below a predetermined value; and initiating dynamic load shedding and/or restoration depending on stability margin.

Abstract: An optical sensor configuration contains an optical current sensor and/or an optical voltage sensor. The sensor configuration further contains a first and a second hollow member, preferably ring shaped profiles, which are together disposed to form a hollow section. The sensor configuration further includes an optical fiber of the current sensor disposed in an annular groove, the groove being disposed at the boundary surface between the first hollow member and the second hollow member, and/or an optical fiber of the voltage sensor is disposed in a recess of the second hollow member. The first hollow member has an annular recess into which the second hollow member is disposed whereas the first hollow member is an L-shaped or U-shaped ring with two legs and the recess is formed between the two legs.