An application of the new approach of atmospheric correction factors to tests performed on post insulators

Abstract

A. P e r e i r a , C E P E L C O P E L IEE-USPT h e t e s t s m a d e in o r d e r t o s u b s i d i s e the r e v i s i o n o f I E C f 0 . 1 / 1 9 7 3 1 1 1 , for s t u d y i n g t h e a t m o s p h e r i c co.rrect'ion parameters, w e r e done on s e v e r a l t y p e s o f a i r g a p s 1 2 , 3 , 4 , 5 1 . T o verify t h e n e w c o r r e c t i o n factors, s e v e r a l dielectric tests'were d o n e o n s t a t i o n post glass i n s u l a t o r s , w i t h d i f f e r e n t a t m o s p h e r i c conditions. T h e r e s u l t s o b t a i n e d w e r e correctted u s i n g t h e I E C 6 0 . 1 / 1 9 7 3 , t h e R e v i s i o n dated f r o m d e c e m b e r o f 1 9 8 7 and t h e n e w e x p o e n t c u r v e s s u g g e s t e d by P i g i n i and plotted a s d i s r u p t i v e v o l t a g e (USOX) v e r s u s t h e r a t i o b e t w e e n t h e ' a b s o l u t e h u m i d i t y and r e l a t i v e a i r d e n s i t y (H/RAD). T h e g r a p h i c s o b t a i n e d c a n be used t o v e r i f y if t h e -c o r r e c t i b n f a c t o r s a r e w e l l dimensioned. W h e n it occurs, t h e s t r a i g h t line o b t a i n e d by t h e a p p l i c a t i o n o f l i n e a r .regression m u s t be p a r a l l e l t o t h e a x i s o f H / R A D v a r i a t i o n (that is t o s a y , t h e v a l u e o f t h e i n c l i n a t i o n is e q u a l t o z e r o ) and t h e r'ange o f U o ( t h e v a l u e of U502 w h e n H / R A D ise q u a l to 1 1 g/m') m u s t h a v e t h e s m a l l e r wi'dth possible. Objekt under test T h e t e s t s a r e m a d e o n s t a t i o n post g l a s s insulators, 2 3 0 kV and B I L equa,l t o 9 0 0 k.V. T h e m e a s u r e d c h a r a c t e r i s t i c s c a n b e s e e n o n F i g u r e 1. --____--________ T h e tests w e r e d o n e in o r d e r t o o b t a i n t h e v a l u e o f t h e d i s r u p t i v e v o l t a g e w i t h 50% o f d i s c h a r g e p r o b a b i l i t y (USOX). T h e f o l l o w i n g d i e l e c t r i c t e s t s w e r e apllied: lightning i m p u l s e , w i t h b o t h p o l a r i t i e s ; --s w i t c h i n g i m p u l s e , w i t h b o t h p o l a r i t i e s ;power frequency. F o r t h e i m p u l s e tests, w a s u c i l i z e d t h e u p and d o w n test m e t h o d , w i t h 40 v o l t a g e a p p l i c a t i o n s a n d , for power f r e q u e n c y t e s t s , w a s c a l c u l a t e d t h e m e d i u m v a l u e o f 1 0 d i s r u p t i v e v o l t a g e applications. Ambient c o n d i t i o n s d u r i n g t h e t e s t s T h e r a n g e .of t h e a t m o s p h e r i c c o n d i t i o n s , noted d u r i n g t h e t e s t s m a d e at the t h r e e l a b o r a t o r i e s involved with. t h e t e s t s w a s plotted o n a g r a p h i c s a s c a n b e s e e n onF i g u r e 2. It a l s o m u s t b e noted-t h e a l t i t u d e o f t h e three.laboratories: CEPEL: s e a level COPEL: 9 0 5 m IEE-USP: 7 6 0 m . I l27 a27 Fig. 1 -I n s u l a t o r u n d e r test ( d i m e n s i o n s i n mm) d r y \arc distance: 1 9 6 0 mm i . z r 1 c. ; , I I i I ! 6 ti la...