Abstract: The present invention relates to an AC or DC power transmission system. The system comprises a first electrical conductor, a second electrical conductor and an insulating space there between. The system further comprises an electric field measurement device comprising the following components being mounted in optical continuation: a first optical fiber being connected to a light source, a first optical lens, a circular polarization filter, a crystal rod having electro-optical properties, a linear polarization filter, a second optical lens, and a second optical fiber being connected to a light detection unit. The electric field measurement device is located adjacent the first electrical conductor and defines a first minimum distance between the crystal rod and the first electrical conductor and a second minimum distance between the crystal rod and the second electrical conductor. The second minimum distance is at least 10 times larger than the first minimum distance.

Abstract: A monitoring system for detecting earth faults in an electrical power supply grid providing a power signal includes a plurality of monitoring devices, each of the monitoring devices including a detector for detecting the level of harmonics in the power signal, wherein the level of harmonics is detected in a specific frequency range. Each of the monitoring devices further includes a memory for storing a harmonics reference value, a processor for comparing the detected level of harmonics with the reference level, and a communication device for transmitting an alarm if the detected level of harmonics is above the reference level for a specific period of time. Each of the detectors includes an optical sensor for detecting the harmonics by use of the Faraday effect.

Abstract: A monitoring system for detecting earth faults in an electrical power supply grid providing a power signal includes a plurality of monitoring devices, each of the monitoring devices including a detector for detecting the level of harmonics in the power signal, wherein the level of harmonics is detected in a specific frequency range. Each of the monitoring devices further includes a memory for storing a harmonics reference value, a processor for comparing the detected level of harmonics with the reference level, and a communication device for transmitting an alarm if the detected level of harmonics is above the reference level for a specific period of time. Each of the detectors includes an optical sensor for detecting the harmonics by use of the Faraday effect.

Abstract: A monitoring system for detecting earth faults in an electrical power supply grid providing a power signal includes a plurality of monitoring devices, each of the monitoring devices including a detector for detecting the level of harmonics in the power signal, wherein the level of harmonics is detected in a specific frequency range. Each of the monitoring devices further includes a memory for storing a harmonics reference value, a processor for comparing the detected level of harmonics with the reference level, and a communication device for transmitting an alarm if the detected level of harmonics is above the reference level for a specific period of time. Each of the detectors includes an optical sensor for detecting the harmonics by use of the Faraday effect.

Abstract: The present invention relates to a Faraday sensor assembly comprising a first light guiding element adapted to guide electromagnetic radiation along a first propagation direction, and a second light guiding element adapted to guide electromagnetic radiation along a second propagation direction, the second propagation direction being essentially oppositely arranged relative to the first propagation direction. The Faraday sensor assembly further comprises a measurement region arranged between the first and second light guiding elements, the measurement region being adapted to receive an electrically conducting element having, in the measurement region, its primary extension direction in a direction being essentially perpendicular to the first and second propagation directions. The present invention further relates to methods and systems for stabilizing output signal from the sensors, and to methods and systems for processing signals from the sensor assembly.

Abstract: The present invention relates to an AC or DC power transmission system. The system comprises a first electrical conductor, a second electrical conductor and an insulating space there between. The system further comprises an electric field measurement device comprising the following components being mounted in optical continuation: a first optical fibre being connected to a light source, a first optical lens, a circular polarization filter, a crystal rod having electro-optical properties, a linear polarization filter, a second optical lens, and a second optical fibre being connected to a light detection unit. The electric field measurement device is located adjacent the first electrical conductor and defines a first minimum distance between the crystal rod and the first electrical conductor and a second minimum distance between the crystal rod and the second electrical conductor. The second minimum distance is at least 10 times larger than the first minimum distance.

Abstract: A method and a system are provided for fixing a Faraday optical current sensor in a suitable measurement position for measuring the current in a 3-phase cable that includes 3 individual section-shaped phase conductors insulated in relation to one another and encapsulated inside an insulator. The method includes providing a Faraday optical current sensor arrangement having 3 Faraday optical current sensors, each of which is fixed in a specific position outside the insulator; and providing a processing unit for calculating a current value from a magnetic field value. The method is performed by measuring 3 magnetic field values using each of the 3 sensors and calculating the current in each of the section-shaped phase conductors using the processing unit and the 3 magnetic field values.

Abstract: A Faraday optical current sensor arrangement for measuring the current through a power line comprises a Faraday optical current sensor (38) having an elongated and substantially cylindrical shape defining a first end and a second end opposite the first end. The Faraday optical current sensor has a first optical conduit (48) extending from the first end and a second optical conduit (48) extending from the second end. Furthermore, the Faraday optical current sensor arrangement comprises a hollow housing (12,14) enveloping the Faraday optical current sensor and fixating the Faraday optical current sensor in a specific measurement position relative to the hollow housing. The hollow housing defines a channel for accommodating the Faraday optical current sensor and the first and second optical conduits and an opening (15) for communicating with the channel.

Abstract: A monitoring system for detecting earth faults in an electrical power supply grid providing a power signal includes a plurality of monitoring devices, each of the monitoring devices including a detector for detecting the level of harmonics in the power signal, wherein the level of harmonics is detected in a specific frequency range. Each of the monitoring devices further includes a memory for storing a harmonics reference value, a processor for comparing the detected level of harmonics with the reference level, and a communication device for transmitting an alarm if the detected level of harmonics is above the reference level for a specific period of time. Each of the detectors includes an optical sensor for detecting the harmonics by use of the Faraday effect.

Abstract: An electric current measurement device includes a housing defining first and second open ends sealed by first and second sealing means, respectively: a first optical fiber received in an aperture in the first sealing means and in optical communication with a first optical lens in the housing; a first polarization filter in the housing in optical communication with the first lens; a magneto-optical rod within the housing in optical communication with the first polarization filter; a second polarization filter in the housing in optical communication with the rod; and a second optical lens in the housing in optical communication with the second polarization filter. The second sealing means has an aperture for receiving a second optical fiber fixed to the second lens. First and second lids, attachable to the first and second housing ends, respectively include apertures for receiving the first and second optical fibers, respectively.

Abstract: An electric current measurement device includes a housing defining first and second open ends sealed by first and second sealing means, respectively; a first optical fibre received in an aperture in the first sealing means and in optical communication with a first optical lens in the housing; a first polarisation filter in the housing in optical communication with the first lens; a magneto-optical rod within the housing in optical communication with the first polarisation filter; a second polarisation filter in the housing in optical communication with the rod; and a second optical lens in the housing in optical communication with the second polarisation filter. The second sealing means has an aperture for receiving a second optical fibre fixed to the second lens. First and second lids, attachable to the first and second housing ends, respectively, include apertures for receiving the first and second optical fibres, respectively.