Abstract:
A fault protection device (103) for a high voltage direct current (HVDC) double-breaker busbar unit (100) is provided. The busbar unit (100) comprises a first busbar (101), a second busbar (102), and at least three switchgear bays (110, 120, 130), each switchgear bay comprising a pair of direct current (DC) circuit breakers (112, 113, 122, 123, 132, 133) being arranged for connecting a DC circuit (111, 121, 131) to the busbars (101, 2). The device is arranged for tripping, during maintenance of any of the circuit breakers (112, 122, 132) connected to the first busbar (101), in 10 response to detecting a fault on a DC circuit (121) connected to the circuit breaker (122) under maintenance, all circuit breakers (113, 133) connected to the second busbar (102) except the circuit breaker (123) connected to the faulty DC circuit (121). An embodiment of the invention is advantageous in that the fault induced current which is to be interrupted is shared by at least two circuit breakers (113, 133). Further, a fault protection method of an HVDC double-breaker busbar unit is provided.
Abstract:
The present invention relates to an HVDC switchyard arranged to interconnect a first part of a DC grid with a second part of the DC grid. By means of the invention, a first part of the DC grid is connected to the busbars of the HVDC switchyard via a fast DC breaker, while further part(s) of the DC grid are connected to the busbars of the HVDC switchyard by means of switchyard DC breakers of lower breaking speed. By use of the inventive HVDC switchyard arrangement, the cost for the HVDC switchyard can be considerably reduced, while adequate protection can be provided. In one embodiment, the fast DC breaker is an HVDC station DC breaker forming part of an HVDC station. In another embodiment, the fast DC breaker is a switchyard DC breaker.
Abstract:
The invention provides a method, device and computer program product for providing improved control of power or voltage oscillation damping in a power transmission system. The device comprises a magnitude obtaining element (30) configured to obtain an instantaneous magnitude of a signal ( I ΔP I ) representing a deviating oscillation in at least one element (12) of the power transmission system, a slope investigating element (58) configured to determine the rate of change of the signal, and a first processing block (34) comprising an integrating element (38) configured to integrate the instantaneous magnitudes with an integrating factor (Ki) that is based on the determined rate of change. The first processing block is further configured to form a phase compensation angle (ϕ c ) based on the integrated instantaneous magnitude for use in a damping control signal generating unit in order to provide power or voltage oscillation damping of the system.
Abstract:
A method for controlling the power flow in an ac transmission line comprises prompt handling of voltage recovery and only thereafter thermal constraints.
Abstract:
Apparatus for controlling the power flow in a high voltage network, comprising a phase shifting transformer (PST) (1) having tap changing means.
Abstract:
The device according to the invention is adapted to protect, in an electric power plant, objects (1, 7, 27) against fault-related over-currents, said objects being connected to an electric power network (3) or another equipment in the electric power plant. An over-current reducing arrangement (5) is connected to a line (2), which interconnects the network/equipment (3) and the object (1, 7, 27), said arrangement being actuatable for over-current reduction with the assistance of an over-current condition detecting arrangement.
Abstract:
This invention is related to a device and a method for protection, in an electric power plant, of an object (1) against over-currents from a network (3) or another equipment included in the high voltage plant, the device comprising a switching device (4) in a line (2) between the object and the network/equipment. The line (2) between the object and the network/equipment is connected to an arrangement (5) reducing over-currents towards the object (1), said arrangement (5) being activatable for over-current reduction with the assistance of an arrangement (11-13) detecting over-current conditions within a time period substantially shorter than the breaktime of the switching device (4).
Abstract:
In a method for reducing the influence of third harmonic voltages upon direct connection of alternating current machines (1) to a three-phase power network (5), wherein at least one winding of the machine is Y-connected and the neutral point (2) of the winding is available, a suppression filter (14) is connected between the neutral point (2) and the ground point (4) of the power network. The characteristic of the filter alters in the event of risk of the filter getting into third-harmonic resonance with the network and the machine. In such a device, altering means (20, 21) are provided to alter the characteristic of the filter (14).
Abstract:
A high voltage direct current (HVDC) switchyard(300)is provided. The switchyard is arranged for interconnecting three or more sections(310, 320, 330)of an HVDC power network, such as transmission lines, converters, or any other type of HVDC equipment. The switchyard comprises at least one main circuit breaker (301) and at least four transfer switches(302–305). The at least one main circuit breaker and the at least four transfer switches are arranged so as to enable to individually disconnect any one of the at least three sections of the HVDC power distribution network. In an embodiment of the invention, the transfer switches which usually are comprised in direct current (DC) hybrid circuit breakers are used as selector switches,thereby reducing the number of main breakers in the switchyard.
Abstract:
The invention relates to a method (80) for controlling power flow within a DC power flow within a DC power transmission network (1) comprising two or more interconnected converter stations (10 a , 10 b , 10 c , 10 d , 10 e ). The method (80) comprises the steps of: establishing a common feedback signal (U d,common , Ũ d'common ) to the converter stations, the common feedback signal (U d,common , Ũ d',common ) being based on an overall voltage level in the DC transmission, power network (1); providing, in the converter stations, a control signal (S 1 , S 2 , S 3 , S 4 ) based on the common feedback signal (U d,common ) and a drooped error signal (P e, droop , U e, droop ); and controlling the power flow within the DC power transmission network (1) towards set operating points ( U d ref , PCC ref by using the control signal (S 1 , S 2 , S 3 , S 4 ). The invention also relates to a control device ( 18 a , 18 b , 18 c , 18 d , 18 e ) and computer program products.