Hitachi Energy Patente

A high impedance fault (HIF) may cause a section of a power line to burn open. When the fault current is in the same order of magnitude as the normal load current, the protection device that is upstream from the faulted power line will not trip, which may make it difficult to quickly identify the location of the faulted power line. Accordingly, disclosed embodiments leverage advanced metering infrastructure (AMI) data in a weighted least squares (WLS) distribution state estimation to estimate a state of the power network. The estimated states from successive WLS distribution state estimations may be used to calculate power-flow drops, which are used to define the search space for the faulted power line. From this search space, a single power line may be identified as the faulted power line, such that remedial action(s) may be performed to resolve any resulting power outages.

In one embodiment, the bi-mode insulated gate transistor (1), BiGT, comprises: - a pilot region (21) and a mixed region (22) at a bottom side (20), - a first region (31) at a top side (30) opposite the bottom side (20) and atop the pilot region (21), and a second region (32) at the top side (30) and atop the mixed region (22), wherein - the first region (31) and the second region (32) are each provided with a gate electrode (41, 42), and - the gate electrodes (41) in the first region (31) and in the second region (32) are electrically addressable independent from one another.

An electric power converter (1) comprising an enclosure (2) and a plurality of devices (3) that generate heat during operation and are located inside the enclosure (2), wherein- and enclosure (2) comprises an air inlet opening (21) and an air outlet opening (22),- the enclosure (2) is airtight except for the air inlet opening (21) and the air outlet opening (22),- the air inlet opening (21) is configured to be connected to an air mover (41) creating a positive pressure,- an air distribution manifold (51) is located inside the enclosure (2) and connected to the air inlet opening (21), and- the air distribution manifold (51) has air openings (6) directed towards the devices (3).Further, an electric appliance (10) is specified.

The present disclosure relates to a device for providing unifying control of a plurality of converters. The device comprises a central controller configured to obtain current and voltage measurements at at least one reference point, a plurality of local controllers each associated with one of a plurality of converters and each configured to obtain a current and voltage measurement of the respective converter and a plurality of unifying controllers each associated with one of the plurality of converters and configured to provide unifying control of the converters based on control signals of the central controller and/or the respective local controller. The disclosure further relates to a corresponding system, method, storage medium and computer program product.

The present disclosure relates to a protection assisting device (100) configured to communicatively connect to a first protection system (PS<A>) at a first substation (10<A>) of an electrical power network (EPN) and a second protection system (PS<B>) at a second substation (10<B>) of the electrical power network (EPN), the first substation (10<A>) and the second substation (10<B>) electrically connected to a power line (PL), the first protection system (PS<A>) and the second protection system (PS<B>) communicatively connected via a primary communication network (1001), said first protection system (PS<A>) and said second protection system (PS<B>) cooperating to provide differential protection via a respective first protection relay (R<A>) and a second protection relay (R<B>) based at least on a first power line measurement of the power line (PL) at the first substation (10<A>) and a second power line measurement of the power line (PL) at the second substation (10<B>). The protection assisting device (100) is configured to provide protection assisting information to the first protection relay and the second protection relay based on one or more predetermined protection assistance conditions determined from operational data received from the first protection system and the second protection system via a secondary communication network different from the primary communication network, which secondary communication network is a nondedicated communication network. The present disclosure also relates to a protection assisting system, an electrical power network, and a method of providing differential protection assistance.

The present disclosure relates to a system (100) for controlling communication between a first protection system (PS_A) at a first substation (10_A) of an electrical power network (EPN) and a second protection system (PS_B) at a second substation (10_B) of the electrical power network (EPN), wherein the first substation (10_A) and the second substation (10s) are each electrically connected to a power line (PL), wherein a first protection relay (R_A) of the first protection system (PS_A) and a second protection relay (R_B) of the second protection system (PS_B) provide differential protection, the system (100) comprising: a communication network (1000), the system (100) is configured to: communicate critical data and non-critical data between the first protection system and the second protection system via said plurality of communication paths, wherein said critical data comprises first source data (SD_A) representing a first power line measurement of the power line (PL) at the first substation (10_A), and/or second source data (SD_B) representing a second power line measurement of the power line (PL) at the second substation (10_B), wherein the system (100) further comprises: at least one traffic shaper configured to control at least one network parameter associated with at least one node of said communication network to provide from said plurality of communication paths at least one traffic-shaped communication path in which communication of critical data is prioritized over non-critical data. An electrical power network (EPN) comprising the system and a method of controlling differential protection communication are also disclosed.

The invention relates to a transformer assembly (2) which comprises a panel radiator (4) provided at least on one side of the transformer assembly (2), and at least one external reinforcement structure (14, 1401, 1402, 1403, 1404, 1405). The panel radiator (4) comprising a first panel (6) and a second panel (8), wherein the second panel (8) and the first panel (6) are joined along a circumferential edge area (10) of the panel radiator (4) to form an internal space (12) configured to accommodate oil for cooling the transformer assembly. The at least one external reinforcement structure (14, 1401, 1402, 1403, 1404, 1405) is to reinforce at least a portion of the circumferential edge area (10). The external reinforcement structure (14) is provided on at least a lateral region (16, 18) and/or an upper region (20) of the circumferential edge area (10).

There is disclosed herein a system and method for determining updated references converters in a multiterminal DC, MTDC, power network. The method comprises obtaining (410) information for a plurality of converter stations in the MTDC power network, providing (420) the information as input to an optimization problem, and solving (430) the optimization problem numerically to thereby obtain the updated references. The solution ensures the dispatching of power and voltage profiles across the system, minimizing deviations from pre-contingency operations and ensuring compliance with all network constraints.

There is disclosed herein an HVDC, circuit breaker arrangement (1) for an HVDC system (100) comprising a transmission line (4) connected to a converter station (2). The HVDC circuit breaker arrangement comprises a serial arrangement (10) of a first current limiting device (14), an HVDC circuit breaker (12) and a second current limiting device (16). The first current limiting device and the second current limiting device are arranged on different sides of the HVDC circuit breaker in said serial arrangement. The HVDC circuit breaker arrangement is configured to be connected in series along the transmission line of the HVDC system. The first and second current limiting devices are configured to limit a rise in current in the HVDC circuit breaker upon occurrence of a fault in the HVDC system. The present disclosure further relates to an HVDC system.

A transformer (1) comprises a tank (2) forming a housing of the transformer (1), an active part (3, 4) including electric components for transforming voltage, and a cooling fluid (5) for cooling the active part (3, 4) during operation of the transformer (1). The transformer (1) further comprises a cushion element (7) comprising an elastomer material. The active part (3, 4) is immersed in the fluid (5) inside the tank (2), and the cushion element (7) is arranged inside the tank (2) between a tank bottom (9) and the active part (3, 4) with respect to an upright longitudinal axis (L) of the transformer (1).

A cooling profile (10) for a transformer comprises an elongated shape with a predetermined length (L) along a longitudinal axis (A) and a first contact portion (11) and a second contact portion (12). Both contact portions (11, 12) are configured to be coupled to an associated first winding (1) or second winding (2) of the transformer. A middle web (18) connects the first and the second contact portions (11, 12) along a transverse axis (B) transverse to the longitudinal axis (A). The cooling profile (10) further comprises a fin structure (20) including at least one protrusion (21) arranged on the middle web (18) between the first and the second contact portion (11, 12) along the transverse axis (B) such that the fin structure (20), the first contact portion (11) and the second contact portion (12) form a plurality of cooling channels (17) opened along the longitudinal axis (A).

The present disclosure relates to a method for fault localisation on a power transmission line. The method comprises obtaining an estimated location of a fault on the power transmission line; obtaining, by an unmanned aerial vehicle (UAV) image and/or video and/or audio data of a search area of the power transmission line, wherein the search area includes the estimated fault location; and identifying, by analysis of the image and/or video and/or audio data, a fault location on the power transmission line. The disclosure also relates to a corresponding system.

The present disclosure relates to a method for fault detection and fault localisation on a power transmission line. The method comprises obtaining a fault location of a fault on the power transmission line, obtaining, by an unmanned aerial vehicle (UAV), image and/or video and/or audio data of the fault at the fault location, and identifying, by analysing the image and/or video and/or audio data, a fault condition.

The invention relates to a semiconductor switching circuit (1) and a method to control thereof. The semiconductor switching circuit (1) comprises a plurality of semiconductor switches (11) connected in parallel and each com-prising a gate (111) and a collector (112), and at least one circuit protection component (13) having a current increasable impedance, wherein the gates (111) of the plurality of semiconductor switches (11) are connect-ed in series with the at least one circuit protection component (13), and in response to a failure of at least one of the plurality of semiconductor switches (11), a driving current of the respective gate (111) connected to the at least one circuit protection component (13) increases the impedance of the at least one circuit protection component (13).

The present disclosure relates to a method for optimisation of a dynamic behaviour of one or multiple power-electronics equipment. The method comprises providing a dynamic simulation model of a power-electronics equipment, obtaining an output of a real power-electronics equipment and an output of the dynamic simulation model, comparing the outputs of the real power-electronics equipment and the dynamic simulation model and adapting, depending on the comparison, parameters of the dynamic simulation model to a target dynamic behaviour of the power-electronics equipment.

The invention relates to a Modular Multilevel Converter, MMC, comprising, for each of three phases, a plurality of Modular Multilevel Converter cells (1u, 2u, Nu, 1l, 2l, Nl) each comprising a plurality of sub cells (100, 133, 134) each comprising a positive DC bus (114, 126, 127, 128), a negative DC bus (115), a capacitor (104) connected between the positive DC bus (114, 126, 127, 128) and the negative DC bus (115), and at least one half or full bridge having at least one series connection of two switches (108, 109, 200, 201) with a midpoint (A, 123, 124, 125) and connected in parallel to the capacitor (104); a plurality of inductors (131, 130, 129) and a plurality of second switches (S2); whereby the negative DC busses (115) are connected together; the positive DC busses (114, 126, 127, 128) are each connected via one of the plurality of inductors (131, 130, 129) together (132); and the midpoints (A, 123, 124, 125) are each connected to one of the plurality of second switches (S2).

Embodiments herein provide a housing (100) for high-power converter cells. The housing (100) comprises an enclosure (110) configured to accommodate two or more compartments (120). The housing further comprises at least one compartment (120) disposed within the enclosure (110), wherein the compartment (120) encloses at least one converter cell. The housing further comprises a particulate material (130) disposed within the at least one compartment (120). The particulate material (130) is pressure and shock-absorbing, humidity resistant, arc quenching, electrically insulative, and thermally dissipative, ensuring protection of the converter cell from mechanical stresses, electrical discharges, and thermal overloads during operation.

A bushing (1) for an electrical device (100) comprises an electrical conductor (2) and an insulator (5) surrounding the electrical conductor (2), wherein the insulator (5) is of a single piece or wherein the insulator (5) comprises a first part (6) and a second part (7), wherein the first part (6) is configured to be at least partially positioned at an inner side of the electrical device (100), the second part (7) is configured to be positioned at an outer side of the electrical device (100), the first part (6) is of a single piece and an interface (10) between the first part (6) and the second part (7) is configured to be located at an outer side of the electrical device (100).

There is disclosed herein a fuse arrangement (1) for a transmission line (4) of a high voltage direct current, HVDC, grid. The fuse arrangement comprises a plurality of fuse units (10) connected in series. Each fuse unit comprises a plurality of fuse devices (20) connected in parallel to each other, and a non-linear resistor (30) connected in parallel to said plurality of fuse devices. Said plurality of fuse devices are configured to conduct at the same time. The present disclosure further relates to an HVDC grid system.

The disclosure provides a method for creating a model for predicting frequency responses in a power grid and/or for inertia estimation in the power grid, the method comprising: acquiring a plurality of node data, wherein each of the plurality of node data represents a frequency time series at a corresponding node of a plurality of nodes of the power grid in an ambient state; grouping the plurality of nodes into clusters, wherein each of the clusters comprises at least one of the plurality of nodes; creating a node data average for each of the clusters based on the node data of the nodes comprised by the corresponding cluster; and creating the model based on the node data averages.

Method for inspecting a static induction device, the method comprising: - flying autonomously an unmanned aerial vehicle to follow a path defined by at least one first marker placed in a horizontal two-dimensional plane, wherein the horizontal two-dimensional plane is parallel to a ground or is the ground and wherein the path of the UAV is displaced in a vertical direction from the horizontal two-dimensional plane - executing by the UAV, at each of a plurality of two-dimensional positions defined by a set of second markers placed in the horizontal two-dimensional plane, corresponding predefined instructions, the corresponding predefined instructions comprising creating a recording of the static induction device and comprising at least one of: moving to a predefined vertical distance in a direction perpendicular to the horizontal two-dimensional plane or rotating at an angle around an axis of the vertical direction.

A gas-filled bushing (1) for an electrical device (100), comprising an electrical conductor (2) and an insulator (5) surrounding the electrical conductor (2), wherein the insulator (5) is filled by a gas (4), wherein the insulator (5) comprises a first part (5) and a second part (7), wherein the first part (6) is configured to be positioned at an inner side of the electrical device (100) and the second part (7) is configured to be positioned at an outer side of the electrical device (100), further comprising a sealed compartment (7) for receiving gas in case of leakage from the first part (5) of the insulator (5), wherein the sealed compartment (7) encloses the first part (5).

A transformer enclosure (1) for a transformer comprises:- a wall structure (6) with one or more lateral side walls configured to laterally surround the transformer with respect to an upright longitudinal axis (L) of the transformer enclosure (1),- top structure (3) coupled to the wall structure (6) and configured to cover a top of the transformer with respect to the longitudinal axis (L), and- a cover structure (2) forming a cover above the top structure (3) on a side opposite the wall structure (6) with respect to the longitudinal axis (L), wherein the cover structure (2) is coupled to and spaced apart from the top structure (3) with a predetermined distance in between such that the cover structure (2) and the top structure (3) form a double panel structure with an air channel (12) in between for air ventilation.

According to an aspect of the present inventive concept there is provided a computer-implemented method (1000) for generating technical explanations of alarms in a supervisory control and data acquisition, SCADA, system for an electrical infrastructure, the method (1000) comprising: providing (1100) a neural network, NN, model trained to detect anomalies in data, wherein the NN model is trained on a training dataset comprising training data based on operational data retrieved by the SCADA system from the electrical infrastructure and comprising data related to a plurality of system parameters of the SCADA system, receiving (1200) run data based on operational data retrieved by the SCADA system from the electrical infrastructure, the run data comprising data related to the plurality of system parameters, detecting (1300), with the NN model, an anomaly in the run data, and generating (1400) a technical explanation of the detected anomaly by means of an interpretability model, wherein the interpretability model applies a model-agnostic interpretable technique to the run data to determine a contribution of the system parameters in the plurality of system parameters to the detection of the anomaly.

There is disclosed herein a computer-implemented method (300) for monitoring an static induction device (3), comprising obtaining time-series data (308) comprising monitoring data (307) for the static induction device (3), and decomposing the time-series data (308) into a plurality of layers (310), each layer (310) comprising a subset of the time-series data (308), wherein at least one layer (310) is configured to contain a respective contribution (420) to the monitoring data (308) from a contributor (418). The method (300) further comprises providing each layer (310), as input, to a respective predictive model (312) of a corresponding plurality of predictive models (312) configured to predict future contributions to the monitoring data (310) from the respective contributor (418), and receiving, as output from the plurality of predictive models (312), respective predictions (314) of future contributions from the contributor (418) of each layer (310). Finally, the method (300) comprises aggregating the predictions (314) from each predictive model (312) to thereby obtain predicted monitoring data (316) for the static induction device (3). In this way, the accuracy of the predictions for how the static induction device monitoring data will change is greatly enhanced, enabling a more pro-active control for a power network.

The invention relates to a system (20) for a gas-insulated switchgear (2), comprisinga housing (30) with a flange (32) to be coupled to an electrical component (3), e.g. a disconnector/earthing switch, of the gas-insulated switchgear (2);a low-power instrument transformer (40) arranged in the housing (30) and configured for conducting current and voltage measurements; anda cable end module (50) arranged in the housing (30) and configured for receiving at least one power line (100) to be electrically connected to the electrical component (3) through the flange (32).

The present disclosure relates to a power supporting system (1) comprising an energy storage system (100), ESS, comprising at least one string (S-1, S-M). Each string (S-1, S-M) comprises at least two energy storage racks electrically connected in series. Each energy storage rack comprises at least one energy storage module (ESM-1, ESM-N). Each energy storage module (ESM-1, ESM-N) comprises at least one energy storage cell (C-1, C-2, C-X), and a cell management system (xMS-1, xMS-N) configured to manage said at least one energy storage cell. The power supporting system (1) comprises at least one control device (10, 10-1, 10-M), and at least one primary communication unit (20-1, 20-M), PCU, each PCU (20-1, 20-M) configured to provide a dedicated communication channel between at least one of said at least one control device (10, 10-1, 10-M) and CMSs (xMS-1, xMS-N) of one of said strings (S-1, S-M). Said at least one control device (10, 10-1, 10-M) and said at least one PCU (20-1, 20-M) are arranged remotely relative to said ESS (100). Said at least one control device (10, 10-1, 10-M) is configured to control, by communication via said dedicated communication channels, a remote firmware loading process to update said CMSs (xMS-1, xMS-N) of said at least one string (S-1, S-M). A method of updating CMSs of a power supporting system (1) is also disclosed.

The disclosure provides a subsea electrical connection comprising: an electrical conductor extending along an axial direction of the electrical conductor; and a first flexible bellow surrounding the electrical conductor in a radial direction perpendicular to the axial direction, wherein an inner surface of the first flexible bellow is spaced apart from the electrical conductor in the radial direction.

The present disclosure relates to a control device (20) configured for grid-forming control using a voltage source converter, VSC, (10) electrically connected to a power grid (40) via a point-of-common-coupling, PCC, the control device (20) comprising: a decoupling controller (21) configured to determine a VSC virtual electromotive force (v<EMF>) of said VSC (10) based at least on a first complex signal (K; γ, δ), which first complex signal (K; γ, δ) is based at least on a complex power (S<g>; P<g>, Q<g>) being exchanged between said VSC (10) and the power grid (40), and a complex power reference (S<ref>, P<ref>, Q<ref>) for said complex power (S<g>; P<g>, Q<g>), and a current controller (22) configured to determine a VSC voltage reference (v<c,ref>) for said VSC (10) based at least on a grid voltage (v<g>) for said power grid (40) at said PCC, and a current reference (i<f,ref>) for a current (if) propagating between said VSC (10) and said PCC, a virtual admittance unit (24) configured to determine said current reference (i<f,ref>) based at least on a voltage input (v<in>) multiplied with a virtual admittance (Y<v>), wherein said voltage input (v<in>) is based at least on a voltage difference between said VSC virtual electromotive force (v<EMF>) and said grid voltage (v<g>), and said virtual admittance (Y<v>) is based at least on a virtual impedance between the VSC virtual electromotive force (v<EMF>) and said PCC, wherein the control device (20) is configured to provide said VSC voltage reference (v<c,ref>) to said VSC (10), and wherein said decoupling controller (21) comprises a phase compensation unit (211) configured to apply a phase compensation to said first complex signal (K; γ, δ), which phase compensation is selected to compensate for a phase-shift introduced by said virtual impedance. A method of grid-forming control and a power supporting system is also disclosed.

There is disclosed herein a protection enhancement device (110) for a power network (200), comprising a control module (112) configured to, in response to a detection of a fault current at a detection location in the power grid, control a power device (120) to inject an additional current to supplement the fault current in the power network to thereby cause a protection response on the power network, and/or control a protection device (120) to initiate a protection response on the power network (200). In the latter case, the detected fault current has a different value to a protection response configuration setting for the protection device at which a protection response of the protection device (120) is caused. Also disclosed herein are associated protection methods performable by devices, and a protection system comprising such devices.

The invention relates to an operating mechanism for a switching device (601), comprising a motor (1), an axially extending screw rod (701) and a spindle nut (702), whereby the screw rod (701) is connected to the motor (1) and configured for being rotated by the motor (1), the spindle nut (702) is movable engaged with the screw rod (701) and configured to move linearly along the screw rod (701) when the screw rod (701) rotates, and the screw rod (701) comprises a chamfered thread tip (706) insertable into the spindle nut (702), whereby the chamfered thread tip (706) comprises a first chamfered surface (708) extending in a first angle (α) relative to the axial extension of the screw rod (701) and a second chamfered surface (709) extending in a second angle (β) relative to the axial extension of the screw rod (701) and greater than the first angle (α).

A method of detecting a fault in a DMR line (6a-6e) or in an electrode line (13) in a bipolar HVDC system (1) comprises creating an AC current (i_harm) in the DMR line (6a-6e) or in the electrode line (13) during bipolar operation of the HVDC system (1), measuring currents (i₁, i₂) at two or more locations in the DMR line (6a-6d) or in the electrode line (13), calculating the difference (D_RMS) between the currents (i₁, i₂) and determining if the difference (D_RMS) is larger than a pre-defined threshold level (L) for detecting a fault (12) in the DMR line (6a-6e) or in the electrode line (13).

The present disclosure relates to transformer diagnosis methods for a transformer having a primary side source winding and two secondary side load windings. The method using relations based on a transformer model in which effects of magnetizing currents in the transformer core, leakage inductances and effective resistances of the primary and secondary windings are taken into account, wherein a transformer model of a three-winding transformer is used; transformer currents are measured during variations of the transformer loads wherein the power transferred through the respective windings are proportional; measurements are collected, for at least two different transformer loads, of a selection of primary side currents being indicative of the transformer load; a linear fits is performed by means of relations based on said transformer model, between equivalent load current and the primary current to estimate the value of at least one of the following transformer properties: turn ratio and magnetizing current.

There is disclosed herein an energy storage module (10) for an energy storage system (4) connected to a power grid (2). The energy storage module comprises an energy storage unit (20) having an equivalent capacitance (22). The energy storage unit has an internal resistance (24). The energy storage module further comprises a bypass circuit (30) connected in parallel to the energy storage unit. The bypass circuit comprises a bypass switch (32) and a current limiting device (34) connected in series. A resistance of the current limiting device is less than 500 % of the internal resistance of the energy storage unit. There are also disclosed herein an energy storage system and a power grid system.

The present disclosure relates to a method for monitoring a physical asset, the method comprising: receiving data associated with the physical asset from one or more data sources, wherein the data include measurements of one or more parameters of the physical asset; providing a physical model associated with the physical asset, wherein the physical model includes the one or more parameters of the physical asset; providing one or more cost functions, wherein each cost function is associated with one of a plurality of degradation scenarios; determining, based on the data, the physical model and the cost functions, a most probable degradation scenario of the degradation scenarios; and initiating a mitigation action based on the determined most probable degradation scenario indicating a potential failure.

In one embodiment, the electric system (1) comprises a static electric induction device (2) and an electrochemical impedance spectroscopy, EIS, sensor (3), wherein- the electric system (1) comprises a protective coating (4) to protect a component (21, 22, 23, 24, 25) of the electric system (1) from an exterior (A),- the EIS sensor (3) comprises a working electrode (31), a reference electrode (32) and a counter electrode (33), a test portion (40) of the protective coating (4) directly extends across the working electrode (31), the reference electrode (32) and the counter electrode (33),- the working electrode (31) is of areal fashion and is surrounded by the reference electrode (32), the latter being surrounded by the counter electrode (33), seen in top view of the test portion (40), and- the EIS sensor (3) is configured to provide information about a corrosion state of the protective coating (4).

An electric appliance (1) comprising a tank (2) and a shielding plate (2) mounted to an inner wall (21) of the tank (2) is specified, wherein the electric appliance (1) comprises a vibration damping system (4) configured to dampen a transfer of vibrations from the shielding plate (2) to the tank (2).

The invention relates to a tulip contact (10) for a gas-insulated circuit-breaker (1), comprising at least one contact section (12) having an inner contour (18) extending along a switching axis (X) between a tip (14) and a root (16), whereinthe inner contour (18) forms a contact throat at the tip (14) and exhibits a first radius (R1) in respect to the switching axis (X) that defines a narrowest cross section of the contact throat;the inner contour (18) comprises a first curved segment (C1) and, optionally, adjacent to the first curved segment (C1) a first straight segment (S1), at least one of the first curved segment (C1) and the first straight segment (S1) form the contact throat;the first curved segment (C1) exhibits a curving radius (RU) defining a convexity of first curved segment (C1) towards the switching axis (X) in a longitudinal sectional view; and1 ≤ RU/R1 and, optionally, RU/R1 ≤ 50.

Transformer (100) comprising a core (10) extending along a winding axis (A). The transformer (100) further comprises a winding (20) wound around the core (10) and extending along the winding axis (A), wherein the winding (20) terminates in a first axial end surface (21) and in a second axial end surface (22). The first axial end surface (21) is arranged opposite the second axial end surface (22) along the winding axis (A). The first axial end surface (21) and the second axial end surface (22) extend along a radial direction (R), which is perpendicular to the winding axis (A). The transformer (100) further comprises a ring element (30) arranged at the first axial end surface (21). The ring element (30) comprises ferromagnetic sheets (31), aligned along the winding axis (A). The ring element (30) further comprises an insulating shell (32) covering the ferromagnetic sheets (31).

The invention relates to a method for determining a faulted phase on a power transmission line, the method comprising obtaining a voltage signal and a current signal of the transmission line, determining a change in the magnitude of the apparent power, ΔS, for each phase based on the voltage and current signal, determining a fault voltage angle, and determining a faulted phase based on ΔS and the fault voltage angle.