Abstract: A method of measuring a characteristic of an electrical insulation system of a high voltage device connectable to an electrical network, the method comprising the following steps: disconnecting the high voltage device from the electrical network and connecting a measuring equipment to the electrical insulation system, thereby providing a test system, connecting an inductor to the test system, determining a reference frequency, determining a measuring frequency of the measuring operation, measuring at least one of capacitance and loss at the measuring frequency and at the reference frequency, providing at least one correction factor according to formulas, and applying the at least one correction factor on measurement results at the measuring frequency to obtain corrected measurements results corresponding to the reference frequency. A device using the method is also provided.

Abstract: A method of measuring a characteristic of an electrical insulation system of a high voltage device connectable to an electrical network, the method comprising the following steps: disconnecting the high voltage device from the electrical network and connecting a measuring equipment to the electrical insulation system, thereby providing a test system, connecting an inductor to the test system, determining a reference frequency, determining a measuring frequency of the measuring operation, measuring at least one of capacitance and loss at the measuring frequency and at the reference frequency, providing at least one correction factor according to formulas, and applying the at least one correction factor on measurement results at the measuring frequency to obtain corrected measurements results corresponding to the reference frequency. A device using the method is also provided.

Abstract: An analog accessory for use in a system for testing protection relays is provided, comprising inputs connectable to the current outputs of a test-set for protection relays and voltage outputs connectable to a protection relay to be tested. By providing an electric circuit adapted to convert current provided by the test-set into a voltage signal on the voltage outputs that simulates an output of a Rogowski sensor, A system and a method for testing protection relays are also provided.

Abstract: A method for determining a dielectric parameter of an electrical insulation of a power system component comprises the following steps: determining the activation energy of the electrical insulation, determining the actual temperature (T1) of the electrical insulation and the temperature (T2) to which the measurement is to be corrected, calculating a correction factor (Axy) by means of the Arrhenius equation, stimulating the electrical insulation with a DC voltage stimulation signal; determining a response for the power system to the DC voltage stimulation signal at the actual temperature, and determining the parameter of the electrical insulation at the temperature to which the measurement is to be corrected based on the response modified by means of the correction factor. Thereby, the individual characteristics of the power system apparatus insulation is taken into account. A device for determining a dielectric parameter of an electrical insulation of a power system component is also provided.

Abstract: A method of measuring the characteristics of a transformer comprises the steps of determining the transformer turns ratio, switching the load tap changer from the current tap position to a subsequent tap position while determining a primary current and measuring the secondary voltage across the secondary side, determining the primary voltage across the primary side, and determining the characteristics of the transformer based on the determined transformer turns ratio, the determined primary current and the measured secondary voltage. Thereby, the static and dynamic characteristics of the transformer including a load tap changer can be determined.