1. ASPECTS RELATED TO DESIGN AND TESTING OF UHV INSULATOR STRINGS WITH CAP AND PIN INSULATORS A. PIGINI N. V. RAMKUMAR Consultant W.S. Industries Limited Consultant W.S. Industries Limited ItalyIndia ItalyIndia

2.  INTRODUCTION  HIGH RATING INSULATOR DESIGN  INSULATOR TESTING

3. INTRODUCTION 320 kN and 420 kN insulators for UHV are considered 320 kN and 420 kN insulators for UHV are considered

4. DESIGN of insulator unit Systematic calculations to evaluate the mechanical and electric stresses inside the insulator units

5. DESIGN insulator string length UHV AC 1050 kV

6. DESIGN insulator string length

7. UHV DC 800 kV

8. DESIGN RIV insulator string UHV AC 1050 kV

9. DESIGN RIV insulator string UHV AC 1050 kV UHV DC??

10. TESTING  SI

11. TESTING  LI

12. TESTING POLLUTION  ACDC RIV, POWER ARC……

13. CONCLUSIONS DESIGN  Design of high rating single unit insulators: mechanically and electrically.  Need of standardisation of dimensions of high ratings  Insulator strings to be designed for mechanical stresses, overvoltages, pollution, RIV  Particularly critical pollution in DC  Optimisation easier if insulators with a wide range of CF are available

14. CONCLUSIONS TESTING UHV  Problematic to represent actual field conditions for UHV  Some tests not feasible according to present Standards (e.g. rain tests)  Qualification can be based on: –Qualification of single units (as for EHV) –Evaluation supported by tests in outdoor plants (SI) –Rain tests –Extrapolation of results on shorter units (LI, POLLUTION, POWER ARC) –Combination of calculations and experiments for RIV

15. CONCLUSIONS TESTING UHV (not only insulators)  Standards many time can not be strictly followed for UHV: the solution has been often to find subjective derogations and short cuts  Adaptation of the standards is necessary: –Reducing the tests to the really necessary ones: testing is costly especially in the UHV range –Recognising that some tests are not feasible (e.g. rain tests) even if their verification is necessary –Relaxing the procedure, if necessary, assuring the necessary sufficient severity. –After Standard modifications assessing the full compliance with the standards, as it should always be