New Concepts in Voltage Grading JENS SEIFERT New Concepts in - PowerPoint PPT Presentation

New Concepts in Voltage Grading JENS SEIFERT

New Concepts in Voltage Grading Jens M. Seifert BU LIKE Lapp Insulators GmbH, Germany

Content • Introduction • Characteristics of Microvaristor/Epoxy Composite • Computational Verification (FEM Simulations) • Experimental Verification • Summary INMR 2015 Munich 2

Content • Introduction • Characteristics of Microvaristor/Epoxy Composite • Computational Verification (FEM Simulations) • Experimental Verification • Summary INMR 2015 Munich 3

Introduction Main Features for Bushing Improvement: • Damping of High Local Electrical Field Stresses no partial discharges proctect from accelerated material aging • Compact Design less requirement of space • Eco-Friendly Design less 𝐓𝐆 𝟕 is required • Economical Design less material cost INMR 2015 Munich 4

Concept of Design Realisation using non-linear field grading material: µVar/epoxy a) conventional bushing b) compact bushing with µVar 𝐞𝟑 ≈ 𝟏. 𝟖𝐞𝟐 INMR 2015 Munich 5

Content • Introduction • Characteristics of Microvaristor/Epoxy Composite • Computational Verification (FEM Simulations) • Experimental Verification • Summary INMR 2015 Munich 6

µVar Filled Epoxy Morphology of µVar Fillers: µVar functional particle: • each particle has the non-linear property • ZnO-particles with Sb-Bi interphase • Semiconductor with respect to field stress • Switching field stress depends on grain size of ZnO • µVar powder require a carrier matrix ZnO grain Sb-Bi interphase INMR 2015 Munich 7

µVar Filled Epoxy Electrical properties of µVar filled epoxy resin with diff. contents: 75 wt% is required INMR 2015 Munich 8

µVar Filled Epoxy Temperature influence: no significant influence of temperature thermal stable INMR 2015 Munich 9

Content • Introduction • Characteristics of Microvaristor/Epoxy Composite • Computational Verification (FEM Simulations) • Experimental Verification • Summary INMR 2015 Munich 10

Modelling Setup A Simulated 550kV Bushing: 2D FEM-Simulations: • Based on EQS (Electro-quasi- static) approximation • Both capacitive and resistive effects are considered • Allow virtual prototypical design with low cost INMR 2015 Munich 11

Simulation Results -33.3 % INMR 2015 Munich 12

Simulation Results The length of the µVar/epoxy layer should not be too short! INMR 2015 Munich 13

Simulation Results The thickness of the µVar/epoxy layer has almost no influence INMR 2015 Munich 14

Content • Introduction • Characteristics of Microvaristor/Epoxy Composite • Computational Verification (FEM Simulations) • Experimental Verification • Summary and Outlook INMR 2015 Munich 15

Experimental Setup Test Setup in HV Laboratory (Lapp Insulators GmbH) µVar/Epoxy layer INMR 2015 Munich 16

Experimental Results Partical discharge measurement (according to IEC standard 60137) Voltage (RMS) Partial Discharge Partial Discharge nominal voltage < 1pC < 1pC (318 kV) test overvoltage <5 pC <5 pC (476 kV ) test overvoltage (710 kV ) 5.5 pC-126 nC 5.5 pC-126 nC 1 min. INMR 2015 Munich 17

Experimental Results Temperature measurement (using an infrared camera) Voltage Time Temperature (RMS) Increase nominal voltage 20 min. 0.3 °C (318 kV) test overvoltage (476 kV ) 10 min. 7 °C INMR 2015 Munich 18

Experimental Results Temperature measurement (using an infrared camera) Image of temperature increase after approx. 10 mintes. start: 23 °C end: 30.2 °C INMR 2015 Munich 19

Content • Introduction • Characteristics of Microvaristor/Epoxy Composite • Computational Verification (FEM Simulations) • Experimental Verification • Summary INMR 2015 Munich 20

Summary • The first compact bushing featuring with µVar/epoxy component • Microvaristor/epoxy composite with above 75 wt% has an obvious nonlinearity • Using µVar/epoxy layers in bushing are able to reduce high electric field stress • This approach allows to design the bushing compactly (eco-friendly and economical design) • Design of compact bushing featuring µVar/epoxy via FEM has been successfully demonstrated • Design via FEM confirmed by high-voltage tests INMR 2015 Munich 21

Thank you for Listening ! INMR 2015 Munich 22