DC Leakage Current Measurement Comparison between SF6 and Fluoronitrile/CO2 Gas Mixture
One of the possible SF6 alternatives that emerged in recent times is a fluoronitrile (FN), NovecTM 4710, based mixture.
Production of Graphite During the Extinguishing Arc with New SF6 Alternative Gases
Using Gibbs free energy method, a theoretical study has been conducted on SF6 replacement candidates listed above.
Effective Permeability of Multi Air Gap Ferrite Core 3-Phase Medium Frequency Transformer in Isolated DC-DC Converters
This article presents the measurements of the equivalent B(H) and the equivalent magnetic permeability of two three-phase MFT prototypes.
Compliance of a cable-based protection strategy for OHL grids: Analysis and remediation
This paper points out the challenges to overcome when applying a protection strategy based on a non-selective fault clearing philosophy without DC reactors to an overhead line based multi-terminal DC grid.
A novel single-ended fault identification algorithm for full selective protection strategy
We propose a parametric single-ended fault identification algorithm to be used in full selective protection strategy.
Characterization of Partial Discharges Initiated by Protrusion in HVDC Coaxial Geometry
This paper aims at the detection and characterization of partial discharges (PD) in GIS under HVDC constraints in the presence of a protrusion/metallic particle on the high voltage conductor.
Partial Discharge Behavior of Protrusion on High Voltage Conductor in GIS/GIL under High Voltage Direct Current: Comparison of SF6 and SF6 Alternative Gases
Recent studies have demonstrated that fluoronitrile (FN) NovecTM 4710 and fluoroketone (FK) NovecTM 5110 show higher dielectric strength than SF6. These gases can be mixed with a buffer gas such as CO2 and technical air to have suitable dielectric properties for high voltage insulation applications.
Design and validation tests of 320kV HVDC GIL/GIS
This paper gives an overview of electrical DC phenomena in GIL/GIS, the influence of insulating properties of SF6 and filled epoxy resin, and design of new support insulator for 320kV HVDC GIL/GIS. The busbar system including the insulator was designed not only to satisfy all standard requirements such as mechanical, temperature rise, heating cycle performance but also particular requirements for HVDC applications such as superimposed impulse tests. Finally and for the first time at actual scale, type test according to CIGRE JWG D1/B3.57 was conducted in EDF R&D Les Renardières laboratory to verify the design and insulating performance of the 320kV HVDC GIL/GIS system. The satisfactory results allow to confirm the high technology readiness level of HVDC GIL/GIS.
NPC assessment in insulated DC/DC converter topologies using SiC MOSFETs for Power Electronic Traction Transformer
Power electronic traction transformers (PETT) are multilevel AC/DC on-board converters, studied for railway applications to replace traditional solution with low frequency transformers. This paper focuses on the insulated DC/DC converter in a PETT. Three variants of resonant single active bridges (R-SAB) with 3-level NPC primaries are optimised to maximise the efficiency, under mass and dimension constraints. They are sized and compared for a 2 MW PETT on a 15 kV/16.7 Hz railway infrastructure, using 3.3 kV SiC MOSFETs and nanocrystalline C-core transformers with cast resin insulation and forced air cooling. The highest efficiency at nominal power, 99.17 %, is reached for a configuration with a 3-level full bridge NPC primary, a 2-level full bridge secondary, and a 32.1 L/49.1 kg transformer operating at 6 kHz.
Electric field computation for HVDC GIS/GIL spacer under superimposed impulse conditions
This paper evidences the influence of different parameters on the electric field on DC spacers in GIS/GIL and thus their dielectric withstand under S/IMP tests. A notable difference in term of electric field can be observed in function of impulse polarity, load condition (with/without heating current) and insulating material’s properties. For example, an overstress of 0.3pu was obtained on spacer’s surface in case of superimposed impulse test with opposite impulse polarity, high load condition and high leakage current in gas. Contrary to AC system where the simple LI tests were enough, S/IMP tests with both impulse polarity, ZL and HL conditions are mandatory to verify the insulating performance of HVDC GIS/GIL spacer. This paper gives a better understanding of the electric field distribution in HVDC GIS/GIL and helps for the design and tests
