Protection Systems for Multi-Terminal HVDC Grids

Abstract

Nowadays the protection of Voltage Sourced Converters (VSC-HVDC) is still a challenge as the high fault currents can damage seriously the converters. Nevertheless, the protection of HVDC grids is more complicated than point-topoint links, because of the specific requirements of HVDC grids. The protection system must detect and clear the faults within a demanding time. Moreover, HVDC circuit breakers are still not available, complicating the selective protection of the grid. Accordingly, since the protection of HVDC grids is so demanding, this issue is one of the biggest obstacles to develop HVDC grids. In this paper the protection system for HVDC grids is presented, including the measurement technology, fault detection and location algorithms and HVDC circuit breaker technology.

Measurement Uncertainty Analysis of Optical Current Sensors Used in Power Systems

“…Electromagnetic induction current transformers (CTs) are measuring equipment of significant importance in power systems, being used for the most diverse purposes, through the measurement of high voltage electric current. Optical current sensors (OCSs) have many advantages over conventional CTs, such as: reduced weight and dimensions, facilitating installation, maintenance and use in remote or difficult-to-access areas; operational safety, as they constructed with dielectric materials and potential catastrophic events will not cause explosions as in the case of conventional oil-filled transformers -in addition to that there will be no critical situations of opening the secondary of the current transformers; linearity throughout its dynamic range; relative lower prices; wide bandwidth; absence of magnetic saturation effects; electromagnetic immunity (as they are nonelectric sensors); AC and DC measurements; and low power consumption [1][2][3].…”