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A New Generation of Thyristor Valves for ±800kV HVDC Projects. Dr. Norman MacLeod Dr. Jonathan Sturgess Mrs. Alison Baker Dr. Fabrice Perrot AREVA T&D, United Kingdom. IEC/CIGRE Symposium 2009, Delhi, India. 800kV Scheme Topologies. Thyristor Valve Hall. Valve Test Object.
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A New Generation of Thyristor Valves for ±800kV HVDC Projects Dr. Norman MacLeod Dr. Jonathan Sturgess Mrs. Alison Baker Dr. Fabrice Perrot AREVA T&D, United Kingdom IEC/CIGRE Symposium 2009, Delhi, India
Boundary Element Method(BEM) • BEM solves the field equations at the boundary domains of the space • Finite Element Analysis (FEA) solves the field equations over the entire space • BEM is more efficient computational process than FEA • Analysis considers 4 variables of the problem • Radii if curvature (r1, r2) of the corona shield • Separation (d1) to roof (or floor) • Separation (d2) to wall d1 r1 r2 d2
Experimental results • Distance to ground and wall varied from 3m to 7m • Doubling distance gives a 40% increase in U50% • Further increase in distance to wall/ground has a diminishing effect on flashover distance, • Electrode curvature is the most important effect
Experimental results • Distance to wall = 7m • Distance to ground varied from 2.5m to 7m • U50% figure is substantially independent of distance to ground • Electrode curvature is the most important effect
DC Voltage Test • DC voltage test • Pre-fault ionisation (streamers) • Recorded using a Ultra Violet camera • Streamers began at top curvature and move downwards • Flashover to ground occurred after 13s
Conclusions • New corona shield designs were required for ±800kV applications • New mathematical techniques were adopted to solve the 3-D electrostatic field equations • A prototype corona shield was designed and subject to extensive DC, lightning and switching impulse voltage tests to validate the field calculations • Thyristor valve design for ±800kV is now available