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Submitted on 1 Jan 1979
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ELECTRICAL FIELD STRENGTH ON THE POSITIVE CORONA ELECTRODE WITH THE
COUNTERFLOW OF NEGATIVE IONS
N. Bogdanova, B. Pevchev, V. Popkov
To cite this version:
N. Bogdanova, B. Pevchev, V. Popkov. ELECTRICAL FIELD STRENGTH ON THE POSITIVE
CORONA ELECTRODE WITH THE COUNTERFLOW OF NEGATIVE IONS. Journal de Physique
Colloques, 1979, 40 (C7), pp.C7-361-C7-362. �10.1051/jphyscol:19797178�. �jpa-00219155�
JOURNAL DE PHYSIQUE CoZZoque C7, suppldment au n07, Tome 40, JuiZZet 1979, page C f - 361
ELECTRICAL FIELD STRENGTH ON THE POSITIVE CORONA ELECTRODE W I M THE COUNTERFLOW OF NEGATIVE IONS
N.B. Bogdanova, B.G. Pevchev and V.I. Popkov.
Krzhizhanovsky P m r I n s t i t u t e , Moscow U. S. s.R.
Introducbion, To calculate t h e corona
electrode systems including corona l o s ~ e s i n power transmission l i n e s , one should know t h e e l e c t r i c f i e l d strength Ec on
electrode surface under corona, Recently t h i s most important c h a r a c t e r i s t i c was measured i i i r e c t l y by 3nglish as well a s Soviet s c i e n t i s t s / 1,2,3,4 /, I t ' s c l e a r from Soviet works / 3,4
/,
t h a t Ec remains constant, i.e. doesn't depend on applied voltage. I n case of unipolar d,c.corona, the e l e c t r i c f i e l d strength Ec on t h e electrode under corona i sequal t o t h e onset s t r e n g t h Eo.
Various aspects of negative ion influence on discharge processes i n a i r including corona were discussed in s c i e n t i f i c lit- erature fox a long period of time. Poss- i b i l i t y of such influence takes place f o r d.c, bipolar corona, f o r d,c. uni- polar corona on p o s i t i v e electrode with negative ion i n j e c t i o n i n t o t h e gap from
external ion source and a l s o f o r a.c.co- rona when negative ions, crea.ted i n t h e negative h a l f cycle, r e t u r n t o %he elec- trode a t the next p o s i t i v e half cycle.
Measurements of e l e c t r i c a l f i e l d strength on the p o s i t i v e corona electrode,in case of counterflow of negative ions c a r r i e d out i n t h e given work, were used t o det- ermine t h e character of influence of
negative ions on corona discharge, t o estimate t h e p o s s i b i l i t y of negative ion detachment and subsequent development of
electron avalanches, and e l e c t r i c a l f i e l d strength necessary f o r t h e detach- ment.
Measurement procedure. The measurements on d,c. and a.c. (50 Hz) corona were per- formed in coaxial electrode s y s t efns with t h e inner electrode, d i a 1 3 mm, having a probe (an e l e c t r o s t a t i c fluxmeter) in-
s e r t e d t h e r e i n and outer cylinder, d i a 100 o r 192 cm / 3,4
/.
I n t e s t s with d.c.bipolar corona three wires,dia 0,08 cm, connected e l e c t r i c a l l y with t h e external cylinder were mounted i n p a r a l l e l with t h e inner electrode (see t h e Scheme in Fig. 1). Three t h i n wires were used in-
stead of one in order t o provide t h e uni- f o m d i s t r i b u t i o n of negative charge over t h e inner electrode surface. The 2ecord- ing of the s i g n a l from fluxmeter was car- r i e d out by a n oscilloscope o r a s e l e c t - ive nanovoltmeter. The e r r o r when meas- uring Ec,by means of an oscilloscope, according t o our estimations, comprises 3%,
i n
case of t h e nanovoltmeter-
1,4%.Experimental r e s u l t s . The measur6d f i e l d strength on t h e inner electrode under d.c. bipolar corona was compared with t h a t in t h e case of unipolar corona
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797178
v&en a i r parameters and c h a r a c t e s i s t l c s of the pj:ojo j z e 1 2 3 :F:.;wL-~. !:.'he L o r a s of p o s i t i v e corona i n both rey;imes a r e d i f f - e r e n t : t h e u n i p o l a r corona i s character- i s e d by t h e appearance of streamers a t overvoltages up t o n = 1,7+1,8, f o r n 7 I , 7+1,8, t h e corona becomes u n i f o m while t h e b i p o l a r corona i s uniform
over t h e whole range of n. in example of measured f i e l d s t r e n g t h E on p o s i t i v e e l e c t r o d e v e r s u s a p p l i e d v o l t a g e U i s given bi Fig, I, T:~Y~ere, i n case of stream mer u n i p o l a r corona(n < I ,7*1,8) t h e max-
imum values of Ec a r e given. A s can be seen, t h e f i e l d s t r e n g t h Ec on t h e posi- t i v e e l e c t r o d e a t b i p o l a r corona ( f o r U 7 Uo
hip)
i s a l s o independent on U.Fig.?
20 d
P
I50
fbo&&p
a w n & 2hUKV
However, under b i p o l a r corona c o n d i t i o n t h e v a l u e of Ec i s lower t h a n t h a t under u n i p o l a r corona, The d i f f e r e n c e between Ec b i p and *c unip d o e s n ' t s i g n i f i c a n t l y exceed t h e measurement e r r o r and equals t o & 8%. The f i e l d s t r e n g t h under corona
~ E c i s equal t o t h e onset E: in both cases. The s i m i l a r decrease of t h e f i e l d s t r e n g t h on t h e p o s i t i v e corona e l e c t r o d e t a k e s p l a c e a l s o with some o t h e r methods of n e g a t i v e i o n i n j e c t i o n i n t o t h e gap and a l s o by r e t u r n i n g of n e g a t i v e i o n s
a t a.c
.
generated during a previous h a l f cycle. The l a s t is i l l u s t r a t e d ir, Fig.2.A f t e r t h e moment of corona onset i n poei-
eases .2l i;;";ltly anti
1,5
rzs l a t e r becomes s t a b l e atP E ~ C
3;- =Eo+
t h e d i f f-
erence between
E :
,
and E: unip n o t exceeding 5-7%.I n a l l c a s e s s t u d i e d t h e e x i s t e n s e of ne- g a t i v e i o n s counterflow a l i - l a p r e s u l t s i n t h e decrease of t h e f i e l d streng-ti1 on t h e e l e c t r o d e with p o s i t i v e corona. This con- f i r m s assumptions ( 5,6,7 ) on t h e d e t - achment of n e g a t i v e i o n s n e a r t h e corona e l e c t r o d e and. following formation of e l e c t r o n avalanches. Experimental r e s
-
u l t s allow t o e s t i m a t e t h e h i g h e s t poten- t i a l g r a d i e n t s when n e g a t i v e i o n s detach.
This g r a d i e n t i s equal t o o r l e s s than t h e f i e l d s t r e n g t h
ED
on t h e e l e c t r - ode s u r f a c e with p o s i t i v e corona a t b i - p o l a r regime, i .e. Edet 38 kV/cm.References 8 .-;rd.l;ers R.T., Rickard y
.x.,
S t a r k i,'/.B. Int .Spp .Hochsp .Miiich, 1972, 104. 2 .Waters H.T., Rickard T.E. , S t a r k W.B. 2nd I n t .Conf ,on Gas Disch,,London, 1972,188. 3 .Bogdanov iat. N.B. , P e v c h e ~ , B .G., Polevoy S ,V, 4 t h I n t .Conf .on Gas Disch.
London, 1 9 6 . 4 .Boddanova, N.B. ,Pevchev B.G. ,Polevoy S.V. E l e c t r i c h e s t v o , l 9 7 8 ,
