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Loose particles and discharges inside the ducts of a gas-insulated substation (GIS) are considered hazardous to the insulation system. These irregularities or flaws can be detected by using acoustic sensors placed on the enclosure. An elementary review of sound propagation in a GIS together with...

Conventional 50/60 Hz induction heaters for aluminum billets have very large losses. By replacing the copper windings with windings of high-temperature superconducting (HTS) tapes, there is a substantial potential for efficiency improvements, especially if low AC loss HTS tapes become available. To...

In an induction heater for heating of aluminum billets, the main reason for using high-temperature superconducting (HTS) tapes instead of conventional copper conductors is to reduce the large power losses in the induction coil. In this work we present how to calculate the different loss...

Air has been considered a good alternative to SF₆ as arc quenching medium for load break switchgear at medium voltage ratings. In this work, the air flow characteristics and influence from the electric arc have been studied for typical currents and over-pressures. The cooling air velocity is...

Failure frequencies for circuit breakers (CBs) (only single pressure ${rm SF}_{6}$), disconnectors and earthing switches, instrument transformers, and gas-insulated switchgear (GIS) have been determined through a comprehensive worldwide utility survey. For CBs and GIS, where comparable results from...

One type test requirement for medium voltage load break switches is to interrupt 100 consecutive "mainly active loads". A puffer-type switch with axial-blown arc has been tested according to the 630 A/24 kV ratings. The nozzle and contact wear were measured regularly to investigate design...

...is presented in detail. The induction heater consists of two magnets in separate cryostats and the billet to be heated is rotated between the cryostats. Short distance between the magnet and cryostat wall, large forces between the magnets, and the need to rotate the billet create application specific...

Sixteen different commercial bolted connectors for 50 and 240 mm2 stranded aluminum cable conductors have been examined in order to identify and clarify the correlations between the quality of a connector and its design characteristics, material usage, assembly procedures, bolt numbers and...

Near an electric arc some polymers, known as ablation materials, change the properties of the arcing medium in a beneficial manner. The interruption capability for current interruption improves by increasing the pressure and the heat dissipation from the arc. The present paper studies medium voltage...

The MgB2 superconductor is an attractive choice for many high-current DC applications, particularly for its low cost compared to e.g. YBCO, and the higher operating temperature than the low-temperature superconductors. To extend the operating range to include also AC applications, the AC losses need...

A simple gas blow switch consisting of an axisymmetric tulip/pin contact and a cylindrical polytetrafluoroethylene (PTFE) nozzle has been used for empirical studies of medium voltage load current interruption in air. Only the thermal phase of the interruption is considered. Based on the results of...

A 420 kV gapped-core five-legged variable shunt reactor is modeled in the frequency range 5 Hz-10 MHz based on frequency sweep measurements and curve fitting. Comparison with time domain measurements at reduced voltage shows that the model can accurately predict the transient behavior of the shunt...

Replacing SF₆ with air as the arc quenching medium in switching equipment is favorable from an environmental point of view, but may be technically difficult for compact devices. Medium-voltage load break switches have modest current and voltage ratings, typically 630 A/24 kV, and are thus expected...

During lightning impulse type testing of medium voltage switchgears up to two spark-overs are accepted. Consequently, when selecting conducting composites for use in screens and shields of such equipment it is important that their surfaces not degrade after a spark-over, as this normally will reduce...

This paper shows the result of a failure survey including the entire population of gas-insulated substations in the Norwegian power transmission system. The survey comprises the complete service experience up to now—nearly 12$thinspace$