Polymeric Insulator Materials for HVDC: Important Properties, Test Methods & Challenges for Standardization JENS SEIFERT
Mini Conference 9 Polymeric Insulator Materials for HVDC: Important Properties, Test Methods & Challenges for Standardization Jens M. Seifert Lapp Insulators, BU LIKE GERMANY The fascination of solutions lappinsulators.com
Results of D1.27 Brochure No. 611 “DC Tracking & Erosion Test” Idea: Development Approach based on IEC 60587 “Inclined Plane Test” DC vs. AC Test Voltage The fascination of solutions lappinsulators.com
Development Approach based on IEC 60587 “Inclined Plane Test”” mass loss, erosion depth, erosion length The fascination of solutions lappinsulators.com
Development Approach based on IEC 60587 “Inclined Plane Test”” Investigation of Electrode Shape and Quality: The fascination of solutions lappinsulators.com
Development Approach based on IEC 60587 “Inclined Plane Test” Investigation of Electrolyte Flow Rate: The fascination of solutions lappinsulators.com
Development Approach based on IEC 60587 “Inclined Plane Test” Investigation of Corrosion Effects (Electrodes): 0.05 g dissolved Fe2+ by 180 C charge ( Coulomb‘s law) simulated by adding to the eletrcolyte: The fascination of solutions lappinsulators.com
Development Approach based on IEC 60587 “Inclined Plane Test” Round Robin Test (Specification): The fascination of solutions lappinsulators.com
Development Approach based on IEC 60587 “Inclined Plane Test” Round Robin Test Results „PASS/FAIL“: The fascination of solutions lappinsulators.com
Development Approach based on IEC 60587 “Inclined Plane Test” RRT Results: „EROSION DEPTH“ The fascination of solutions lappinsulators.com
Comparison of „TEST SEVERITY“: The fascination of solutions lappinsulators.com
CONCLUSIONS: DC-IPT as investigated can not be recommended for the base of an IEC standard The fascination of solutions lappinsulators.com
Retention of Hydrophobicity – Why is this property important? HC=1 HC=6 HC=1 The fascination of solutions lappinsulators.com
Retention of Hydrophobicity - “Dynamic Drop Test (DDT)” (Electra 272/03)" The fascination of solutions lappinsulators.com
Retention of Hydrophobicity - “Dynamic Drop Test (DDT)” (Electra 272/03) Investifation of surface topology: Target: Explore and define a surface topology and roughness in order to achieve reasonable time to loss of HY with good reproducibility Specification for RRT: R Z = 5µm by means of special moulds and sandblasting The fascination of solutions lappinsulators.com
Retention of Hydrophobicity - “Dynamic Drop Test (DDT)” (Electra 272/03) Weibull 63% Quantilles and 95% CI Results of „explorative“ RRT for AC and DC stress: High Scatter! The fascination of solutions lappinsulators.com
Conclusion and further recommendations: • DDT is a promising test method for evaluating the retention of HY • Different materials and their performances can be distinguished • Reasonable test parameters for „ short time test “ have been defined • Surface roughness R Z shall be 5 µm by means of sandblasting of moulds • High scatter in time to failure is still a weak point • Additional (larger) RRTs shall be conducted with different kinds of materials and 5-10 labs • The work is continued in D1.58 in order to improve the test specification and test setup The fascination of solutions lappinsulators.com
Applicability and Reference to HVDC Composite Insulators: Composite Insulators • Comparison of Laboratory Tests and Field Ageing • Design and Service Performance Reviews (Case Studies) • Design & Standardisation Approaches for HVDC (IEC 60815-4) The fascination of solutions lappinsulators.com
Applicability and Reference to HVDC Composite Insulators: Typical Design of Generation III Composite Insulator In DC applications 250-600 kV for more than 36 years The fascination of solutions lappinsulators.com
1000h Salt Fog Testing (CN Std.) D/L T 864 -2004 The fascination of solutions lappinsulators.com
1000h Salt Fog Testing (CN Std.) D/L T 864 -2004 Well selected materials and designs pass the CN 1000 h std. test The fascination of solutions lappinsulators.com
5000h DC Multi-Stress Test The fascination of solutions lappinsulators.com
Design Approach AC and DC CIGRE Technical Brochure No. 518 The fascination of solutions lappinsulators.com
Design Rules DC CIGRE Technical Brochure No. 518 Why? Different electro-dynamical Characteristics of partial arcs AC: small p, small s, small s/p DC: large p, large s limited s/p 1.0 Normal distance p1 and p2 Large distance p1 and p2 The fascination of solutions lappinsulators.com
Design Rules DC AC DC AC: small p, small s, low s/p DC large p, large s limited s/p Normal distance between p1 and p2 larger distance between p1 and p2 CIGRE Technical Brochure No. 518 NEW IEC 60815-4: Prague 2015 TC 36 WG11 The fascination of solutions lappinsulators.com
Case #1: 500 kV Pacific Intertie (USA) Dual pole 36 years very positive experience with HTV Silicone Rubber Composites The fascination of solutions lappinsulators.com
Case #1: 500 kV Pacific Intertie (USA) - Design Review Design Pacific Intertie CD`=25.7 mm/kV The fascination of solutions lappinsulators.com
Case #2: 533 kV Cabora Bassa - Apollo (SA) - Design Review 38 years very positive experience with HTV Silicone Composites 2 Mono Poles The fascination of solutions lappinsulators.com
Case #2: 533 kV Cabora Bassa - Apollo (SA) - Statistical Design Approach Re-Insulation 2013: 6800 glass disk strings were exchanged by composites, The fascination of solutions with CD`=35 mm/kV @ 4700 mm connection length lappinsulators.com
Pollution Performance Curves DC Silicone Composites AC ? DC The fascination of solutions lappinsulators.com
IEC 60815 Statistical Method based on Pollution Performance Curves 400 kV HVDC Design for New Lines in Germany DC Silicone Composites AC ? DC High design efficiency, optimum CD` and length selection! The fascination of solutions lappinsulators.com
IEC 60815-4 (New) – Emprical Method Non- „HTM“ „HTM“ Based on best practice and correction factors (longer insulators) The fascination of solutions lappinsulators.com
Conclusions on DC Material Tests • Tracking & Erosion Resistance (T&E) and Retention of Hydrophobicity under DC voltage stress were recognized by CIGRE as important properties for further standardisation • With the results of a RRT („ Feasibility Study“) performed by CIGRE WG D1.27 it is not recommended to develop a DC T&E test based on the „ Inclined Plane Test Method “ • The Dynamic Drop Test (DDT) has been evaluated positively in order to assess the Retention of Hydrophobicity of polymeric materials • The DDT method will be further investigated and developed by CIGRE WG D1.58 • Hydrophobicity is a very important property for the performance of DC Insulators The fascination of solutions lappinsulators.com
Conclusions on DC Composite Insulators • No Tracking & Erosion failures have been reported under DC voltage stress in service. Justification of a T&E DC test is not given from relevance point of view. The results of this material test are not reflecting the positive experiences made in service • Artifificial Ageing tests (1000 h, 5000 h, wheel test) under DC voltage stress are passed by composite insulators with good design and well selected materials • The hydrophobicity has a very positive impact on the life-time and performance of DC composite insulators • Very positive long-term service experiences exist with HTV silicone material (>30 years) • Standardisation of housing profile and CD selection process is almost completed (IEC 60815-4): Empirical and Statistical Method The fascination of solutions lappinsulators.com
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