Gompre$$Bd Gn$ Gtpaultor$ M ICAFIL LTD" ZU RI CH G 3428 E
Gompre$$Bd Gn$Gtpaultor$
M ICAFIL LTD"
ZU RI CH
G 3428 E
The insulalion of lhe eleclrical equipmenl is an arl requiring shrewd seleclion of malerials and pro-
cessing. Lack of uniformify o{ lhe insulalion slrenglh of malerials, when used in lhe praclical Jormsand lhicknesses which are required by the dif{erenl equipmenfs, has impelled lhe developmenl of
various lesls and tesfing devices, amongsl which lhe Shering Bridge plays a very imporlanl parf.
The Compressed Gas Capacilors belong, as inlegraling parl lo lhese bridges and allow {or lhe
conneclion of lhe laller lo very high vollage sources, The Air Capacilors, which were inil ially used,
are now rapidly being discarded due lo lhe unconslancy of fheir ca.pacilance and lo their loo
large sizes. Micali l manufaclures lhree lypes of Compressed Gas Capacilors. All of lhem have a
capaci lance of 100 pF and have proved lheir re l iabi l i fy on many occasions.
Appl icat ions
Compressed Gas Capaci lors are pr imari ly used
as reference capaci lance for measur ing the di-
eleclr ic losses of lhe insu la l ion maier ia ls, o{power facfor capaci lors, c€rbles, bushings andstack insulalors. They can also be used {or f ie ld
corona losses measurernenfs and, used in con*necl ion wi th secondary capaci fors, can serve
as part of pofenl ia l devices for lhe measuremenl
of the t ransformaf ion rat io of potent ia l andpower t ransformers. Peak vol tage measurementscan also be ef fecfed.
Advantages
The ski l fu l design al lows for smal l s ize uni ls
which can be placed at a l l desired spols of ahigh vol tage f est ing laboralory. The absolute
slabi l i ty of the capaci tance which remains in-sensi t ive to changes of a i r pressure, of a i rdampness and of ambient lemperalure can bement ioned as a special advanfage, The accur-ate values are given in the fo l lowing table,
Raled vol tage Un (50 c/s)
Max. service vol lage Ub
Rated capaci lance Cn
Accuracy ofcapdci tance value (Cn)
(Bo -= 20oCi po:pbif i l l ing gas Nz
ACnChange of capaci lance -G
({ i l l ing gas N:) :
1. As f uncl ion of pressure(r9o : : - 20 o C, po: pbr Ap-+lafm.gauge
2. As funct ion o{ femperalure(r9o == 20 o C,
Po:Pb,Ar9o:+1oC)
3. As funcl ion of temperalure,wi lh consta nl f i l l ing(,9o-_ 20oC,
po:=pbo Ar9.-+1oC)
Change of pressure wi fhconstanl f i l l ing
273 * BxPX: Po 2n + sa
Loss angle fand (Cn)
Max, service pt" tsr t . pb
Slray capaci tances (given asa guide) Ca
C,CoCr",
lnsu la l ion resis lance: ( a, t s1 to
Fi l l ing volume:
CompressedOi l jackef
Residual f i l l ingcyl inder when
Acf ing vol lagecoarse {useglow fuse
9as
Nz in pressured ispatched
of
Admissible lemperalure range
Weighf, net
Tesf valueslesf pressure of pressurecyl i nder(50 c/s, I min,76A/20/11)a) belween eleclrodes
H-(M,A,5,E)b) befween electro.des
M-A-(S,E)
H High vol fage
M Measur ing eleclrode
A Inner screening
S Ouler screening
E Service ground
Cn Slandard capaci lance
Cun Cr, Cn, Cn Slray capaci iances
KVKVpF
o/os
x l0-a
x10-
x10-
alm.
9au9
pFpFpFpF
MQ
li l resl i t res
alm.
gduge
Vd.c.Vd.c.
oc
lbs
af m.gaug
KV
KV
Descpipt ion for circuit of principle, equivalent circuit and dimension
drawing on page 4
t,
5,3
Typ PGI
150
150
100+7
t 0,3
- (0,1
< 10-s12
165
c.., 130cr, 200
560r:, 0
> 2AO
,:
0,2
I 40070
0<E<40
315
22
1,5
300
300
100 + 5
t 0,3
5,6
- (0,5 0,9)
< 10-s16
n, 400c.., 1 000
550Ca.-, 0
> 200
'?o0,2
1 4007A
l}<40
840
26
330
2
I High vol lage eleclrode
2 Measur ing eleclrode
3 Screen eleclrode
4 Glow fuse
5 Coarse fuse
6 Plug
7 Pressure gauge
I Gas oul let f i l t ing
9 Gas in le l f i t t ing
I
Typ PG3 | tru PGs
s00500+3100
t 0,3
- (1 ,3 " ." 1,7)
< 10-5
18
\r 430N, 1000
:60*;0
> 200
13s9s
0,2
I 4007A
0 <" ql 1qA
1060 + 90
30
550
2
The execul ion is represenled in fhe pic lures on page 2 and 3, The acl ive par l consis ls ol two concenlr ic
and carelul ly pol ished melal e leclrodes which are assembled in lhe in ler ior o l a special varnished paper
wqund and gast ight cyl inder. This insulal ing cyl inder is l i l led wi lh sui table lop and bol fom armalures
which increase lhe mechanical s labi l i ly and ensure lhe necessary l ighfness. In lhe lool f i l l ing are localed
lhe gas- in le l bal l valve, lhe pressure gauge, lhe c i rcui l prolecl ion fuses as wel l as lhe screened plug.
The ouler eleclrode is faslened lo lhe lop { i l l , ing and is normal ly connecfed lo lhe source of h igh
vol lage. The inner eleclrode is connecled by means o{ a rugged cont l ruct ion lo lhe fool f i f l ing, lhus
render ing special precaul ions for ra i lways tronspor la l ion unnecessary. This. secondary eleclrode is con-
necled by means of a screened cable lo lhe lerminal M whereby lhe screen i lsel f is connecled lo lhe
lerminal A, These lwo lerminals are insulaled from each olher and l rom fhe fool l i f i ing ' A special screen
eleclrode is provided for avoiding corona ef lecls al lhe infer ior edge of the high vol lage eleclrode. This
eleclrode is galvanical ly connecled lo lhe base l i l l ing and lhus lo ground. The lwo separale lerminals M
and A permi l measuremenls in connecl ion wi lh lhe Wagner Auxi l iary Circui l or wi fh Polenl ia l Adiusl-
menf, The ferminal M is connected lo lhe c i r -
cui t of ihe galvanometer * f f i 'ereas
the term-
inal A should be connected fo the screen
circui t of the br idge, receiv ing al the same
l ime the auxi l iary polenl ia l f or the galvano-
mefer" The background circui l on the f ronl
page i l luslrales the required connect ions wi ih
accuracy. The layoul of the PG-Type Com-
pressed Gas Capaci lors renders impossible any
inf luence of the high vol fage on the br idge
by means of s l ray currents" When working
wi lhoul auxi l iary c i rcui f , both ferminals A and E
are lo be grounded.
Glow'fuses are provided for prolect ing the
instrumenfs connected fo lhe Compressed Gas
Capaci tor againsf overvol lages" These f uses
are inser led in the c i rcui f between ferminals
M and A and ground.
A special Si l icagel f i l ter is del ivered with each
capaci lor for c leaning and drying lhe f i l l ing
gds. The capaci fors are always del ivered wif h-
out gas and musf be f i l ted on the spof wi th
ni l rogen (Nr) 99,5 olo pure or wi th carbonic
acid (COz). The guaranteed lechnical data in
the table refer lo ni t rogen, which shows fhe
fewest anomal ies. l f lhese gasses are nof avai l -
able, a i r can also be used. Each uni t under-
goes severe lesl ing be{ore leaving lhe factory
and owing to i ts care{ul seal ing, f ur lher f i l -
l ing is rarely necessary.
9 4,5
Dese r ipt ion of d imension drawing: v ide page 3
(Sizes given in mi l l imeters)