Method and means for complex, universal earth fault protection in power high and medium voltage system
AssigneeABB Schweiz AG
InventorsEmil Kalina, Vaclav Prokop
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Abstract
A method and apparatus for earth fault in power high and/or medium voltage system may enhance a protection system for special technical task, which is to measure residual current, the invention is, that for earth fault protection in power system or a part of power system, for example, but not limited to, cable connectors, wherein residual current is determined indirectly by the calculation from the phase current values, obtained from the output signals of Rogowski-coil based current sensors.
Claims12
A method for universal earth fault protection in a high and/or medium voltage electrical system application using Rogowski coils as current sensors, the method comprising:
- determining, for earth fault protection in the electrical system, a residual current value indirectly as a sum of phase currents determined from the output of a Rogowski coil based current sensor;
- transforming, using the sensor, the phase currents to voltage signals;
- connecting voltage outputs of the sensor to a protection relay (IED) which digitizes voltage values;
- conditioning and then transforming the voltage values to the measured current value, together with the actual phase of the current values;
- and
- determining the residual current value in a protection relay (IED) as a vector sum of the phase currents.
An earth fault protection system for cable connectors in high and/or medium voltage switchgears, the system comprising:
- a coreless Rogowski coil for each path of a three-phase current path, the coreless Rogowski coils being configured for current sensing,
- wherein the coreless Rogowski coils are combined with protection relays such that residual current of feeders of the switchgear can be calculated, and, when a residual current value reaches a preset level, earth fault protection is activated,
- wherein each coreless Rogowski coil is applied in a thin ringshaped sensor housing, and
- wherein the sensor housing includes concentric outer ribs, allowing the sensor housing to enlarge a creepage path along a diameter of a sensor housing ring.
A method for universal earth fault protection in a high and/or medium voltage electrical system application using Rogowski coils as current sensors, the method comprising:
- determining, for earth fault protection in the electrical system, a residual current value indirectly as a sum of phase currents determined from the output of a Rogowski coil based current sensor;
- and
- implementing a calculation algorithm for determining the residual current value as an exchangeable software-program-product,
- wherein parameters of the exchangeable software-program-product are adjusted or adjustable to a specific use in a switchgear of other applications, such that (i) the calculation algorithm is transferable into a steering electronic via a data medium, or (ii) a data file sent via browser.
Dependencies are inferred from the claim text.