Necessary check points & testing for quality screening of - PowerPoint PPT Presentation

Necessary check points & testing for quality screening of insulators J.M. GEORGE INMR 2017 Barcelona, Spain 1 ¡

Summary 1. Current standards 2. Material aspects § Cement § Purity of glass § Molding and toughening 3. Type and sample tests § Residual strength test § Steep front wave § RIV 4. Recommendations 2 ¡

Summary 1. Current standards 2. Material aspects § Cement § Purity of glass § Molding and toughening 3. Type and sample tests § Residual strength test § Steep front wave § RIV 4. Recommendations 3 ¡

Type tests 4 ¡

Sample and routine tests 5 ¡

Summary 1. Current standards 2. Material aspects § Cement § Purity of glass § Molding and toughening 3. Type and sample tests § Residual strength test § Steep front wave § RIV 4. Recommendations 6 ¡

Cement Typical chemistries of cements. Mortars which are being used with these cements mixed with other additives have approximately 40% of CaO for Portland and at least 30% of Al2O3 for Aluminous cement assemblies 7 ¡

Conversion process Cold cured aluminous cement generates unstable hydrates while the conversion is done during the curing process if it takes place in hot water 8 ¡

Purity of glass Impurities in glass have different origins among which but not only particles from the refractories of the furnace. Numerous other origins have been identified by Sediver in extensive research which started in the early 1980s 9 ¡

Toughening and moulding of glass Toughening is a precise operation in the process. « More is better » is a wrong statement leading to improper toughening 10 ¡

Summary 1. Current standards 2. Material aspects § Cement § Purity of glass § Molding and toughening 3. Type and sample tests § Residual strength test § Steep front wave § RIV 4. Recommendations 11 ¡

Residual strenght test Residual strength test is a critical evaluation process. It needs to be done with thermal preconditioning cycles having a hot temperature around 85°C. This will help pointing out low performance of cold cured aluminous cement 12 ¡

Steep front wave test CSA type test protocol includes a thermo-mechanical preconditionong prior to steep front test 13 ¡

RIV Before and after 20h at 10g/l of salt fog: the RIV coating is gone and RIV performance is degraded. Some manufacturers apply coatings on the cement to improve artifically their RIV performance. After several hours in an environment where dry band arcing exist the performance is severely degraded. 14 ¡

Cap gap Very low quality cap contact on the dielectric can lead to corona and generate corrosion new Low quality insulators are using a plastic ring at the base of the cap which typically will be destroyed ovr time and service conditions Flock application at the base of After some time in the cap is the preffered solution service conditions 15 ¡

Summary 1. Current standards 2. Material aspects § Cement § Purity of glass § Molding and toughening 3. Type and sample tests § Residual strength test § Steep front wave § RIV 4. Recommendations 16 ¡

Additions and changes to current standards More tests in sample tests. Necessity to do sample tests with random selection. New opportunities for new tests to be developped 17 ¡