GET-1008L Distribution Data Book
Transcript of GET-1008L Distribution Data Book
-
8/20/2019 GET-1008L Distribution Data Book
1/35lo·n
nOMI
DISTRIBUTION DATA BOOK
A col l
ectio
n of fundamental data pe rtain ing to the elements o f and the
loads on distr ibuti on syste
ms
In working on problems involving distribution
circuits and equipmenl our engineers often lind
il convenient to refer to basic data that have been
compiled from various sources
by
our Power
Distribution Systems Engineering Operation.
Since this material
is
equally useful to distribution
engineers in the electric utility industry we are
printing it under one cover and presenting it as
a Distribution Data Book.
GENER L ELECTRIC
GET l
P n
led
in u
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TABLE
OF CONTENTS
SECTION
PAGE
I
Circuit Characteristics . . . . . . . . . . . . . . . . 5
A. Resistance
and
Reactance
of
Overhead Lines 5
B Resistance and Reactance of Cables. . . . . 5
C
Underground Cables 5
D Aeri al Cables. . . . . . . . . . . . . . . . . 11
E Tran
sformer
Characte ri stics .
11
II Underground
Distr
i
bu t
ion Systems
fo
r
Residential Areas . . . . . . . . . . 13
A Primary System 13
B Secondary System . . . 3
C
Transformers 13
O. Separable Insulated
Connector
~ u
~ 14
1
Modules vailable
14
2
Selection
•
. • . . . 14
II I Transformer Connections • 15
A Transformer Polarity 15
B Single-phase Paralleling . . . . . . . . . . . . . 15
C Small Three-phase Step-down Banks 15
1 Delta-delta Banks
. . . . . . . . . . .
. . 15
2 Wye-delta Banks 16
3. Delta·wye Banks . 16
4 Open-wye Open·del
ta
Banks 16
5 Open-delta Open-delta Banks . 16
6 Wye-wye Banks
. 16
7
Caution
. 16
D
Autot
ransformers .
•
.
16
IV. Sh
or t
-circuit Calculations . 17
A Line Impeda nce . . 17
B Transformer Imp edance . . . 17
C Impedance
of
Lines
wit
h Different
Vol
tages.
. . . . . . . . . . . . . . . . . . . . 17
D. Effect of Offset. . . . . . . . . . . . . . . . . . 17
E Per Unit 18
F. Allowable Short -circuit Currents for
Insulated Cond uctors . 19
1
Temperature Limits 19
2 Conductor Heating. . . . . . . 19
3. Characteristics of Short Circuits 19
4 Application Procedure
20
5 Exa
mples of Data
Use . . . . . . .
. .
20
V. Voltage Calcu l
ations
. 22
A Voltage Drop . 22
B
Tables for Est imating Vo ltage
Drop.
. . . . 22
1 Three·phase Problems . . . . . . .
22
2
Single-phase Problems
. . . . . . . . . .
23
VI. Voltage Regulating Equipment . . . . . . . 26
A Selection of Regulator . 26
1
Type
. . . . . . . . . . . . . . .
26
2 Location and Size . . .
26
3. Choice for Three·phase Circuits 28
SECTION
P GE
B Regulator Control Settings . . . . 28
1
Regulator Bandwidth
28
2 Time Delay . . . . . . . . . . . . . . . . . 30
3
Voltage Level 30
4 Line-drop Compensator Setting
Chart . . . . . . . . . . . . . . . . . . . 30
C Light Flicker. . . . . . . . . . . . . . . . . . . . 31
D. Lamp Operating Voltage. . . . . . . . . . . .
32
E
R
educ
tion
of
Light Flicker by
Banking Secondaries. . . . . . . . . . . . . 32
VII. Application of Shunt Cap
ac
it
ors
. . .
33
A Basic Considerations in Applying
Shunt Capacitors . . 33
1 Released Capacity 33
2 Voltage Rise . . . . . . . . . . . . . 34
3. Reduction
of
Losses . . . . . . . . .
. .
34
4 Protection 36
5
Additional Benefits . . . .
36
VII I Lightning Protec tion
of
Di stribution
Systems 39
A. Primary Dist r
ibution
Systems. . . . . . . . . 39
1
Impulse Withstand
Le
vel to
be Protected 39
2 Selection
of Arrester
. . . . . . . 39
3. Effective Location of Arresters 41
4 Special Applications . . . . . . . . . . . 42
5
Lightning Protection of
UD
Systems . 43
6
Overhead Line Protection
. .
43
B Second ary Distribution Systems. . . . . . . 44
IX
Overcurrent
Protection of Distribution
Systems . . . . . . . . . . . . . . .
46
A Primary Circuits . 46
1 Calculating Short-circuit Currents . . 46
2 Selection of Overcurrenr Protective
Equipment
. .
. . 47
3 Coordination Requirements
. . . . . . 49
B.
Seconda
ry
Circuits.
. . . . . . . . . . . . .
. . 50
X. System Design - Loading Data . 51
A. Estimating L
oad
51
B L
oad Factor
51
C
Coincidence of Diversity Factor . . . . . . . 52
D. Distribution Transformer Size 52
E
Th
ermal Loading of
Un
derground
Cables.. 55
F Design of the Secondary System 55
G Monitor ing Transformer Loading 56
XI. Losses and Economic Data . . . . . . . . . . . . 57
A Line Loss . . . . . . . . . . . . . . . . . . . . . . 57
B.
Tr
ansforme r Losses . . . . . . . 57
C. Evaluation of Energy Losses . . .. .
57
D Increased Revenue from Increased
Voltage . . . . . . . . 59
E Pr
esent Va
lue
of 1.00 59
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T BLES
P
Table 1. Physical and e lectrical characteristics of open
-w
ire distribution line conductors . . . . . . .
Table 2.
DC
resis
tance
and correction factors for
AC
resistance
. .
Table 3. Conductor sizes, insulation th ickness and jacket thickness
Part A. Crosslinked -polyethylene-i nsulated cab le
s .
. . . . . . . . . . . • . . . . . . . • . . . .
Part B. Rubber-insulated
cables.
. . . • . _ . _ .• . • • _ . . . • . . . . .
Part C. Paper -insulated cables .
•
.
. .
. . .
•
_ . _
. .
Ta
bl
e 4.
Approximate
distribu tion
transformer
imped
ances.
. . . . . . . . . . . . . . . . . . • . . . . • . . .
. .
Table 5. Full-load curr
ent
of
transformers in amperes • •
Table
6.
Typical data fo r single-
conductor
concentric neutral cable, crosslinked-
po l
yethylene
-insu la
ted . .
.
Table 7. Typical data for si ngle-phase trip lexed 600.., service cable, crosslinked-
jX)lyethylene-insulated . . . _ . . . . . . . . .
Table 8 . Trans
former
imba lance .
Tab le 9. Circuit breakers, circu it reclosers, dist ri bution expulsion ar resters and fuses
Table 10. Max imum short-circuit temper
at
ures for types of insul
at
ion. . . . •
Table 11. Natu ral si nes , tangents and angl es corresponding to cosine values of 1.
00
to
0.00
. . . . . . . .
. .
Table 12. Voltage drops
of
open -wi re lines in volts per 100,000 ampere feet . • . _ .
Table 13. Voltage drops
of
underground cables in volts per 100,000 ampere feet . . . . . . . . . . . . . . .
. .
Table 14. Function
perfo
rmed by regulators and capacitors . . •
Table 15. l oad bonus regulation .
. .
.
Table 16. Power-
factor
co rrection fa
ctors.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. .
Table 17. Applicat ion guide for
group
-
fu
sing ca
pacitor
banks wit h General Electric universal
ca
ble-
type
and oil cut
out
fuse link ratings N ,
OI L
, K , and
T types
(G
ro tmd ed-wye
and
de lta co nnections; 25-,
50
- and 100-kVar units)
. .
Table 18 . Application guide fo r
group
-fusing
capacitor
banks with General Electr ic universal
cab le-type and oil cutou t fuse link ratings N , O i l , K , and T types
(Floating-wye
con
n
ection;
25-,
50
- and 100-kVar units) _
Table 19. Applicat ion gu ide for
group
-fusing capacitor
banks
wit h General Electric universal
cable-
type
and o l cu tout fuse link
rat
in
gs
N , Oil , K , and T types
(Grounded-wye and delta
connect
ions; 150-,2
00
-, and
300
-kVar un its) .
Table 20. Application guide for group-fu sing capacitor banks with General
El
ec tric universal
ca ble-ty pe and o il
cutout
fu se link r
at
in
gs N , O IL
,
UK ,
and T ty pes
(Float ing-wye connections; 150
-,
20 0-, and 300-kVar units) . . . . . . . . . . . . . . . . . .
. .
Table 21. Bas ic impulse insula
tion
leve ls (B lls) and withstand tests .
Table 22. Arrester ratings
vs
maximum overvoltages . .
Table 23. P
erformance
characte
ri
stics
of
General Electric
distribution
arresters
Table 24.
Di
electri c tests for dry-
type
transformers and dry -
type
sh
unt
reactors _• . . • . _ . . _ . .
Table 25. UD transformer-arreste r protection .
. _• • . . • _ . . _
Table 26. T ime-current curves for HR rec losers
. .
Table 27. Distri
bution
transformer losses .
Table 28. Distribution transformer losses
at othe
r than rated voltages . . .
Table 29. Losses for distribution transformers operating
at other
than rated voltages .
Table 30. Prese
nt
values (Vn) of 1 .
00
in vestments
to
be made in years (n) from now, based
on certain rates
of
interest (i)
. .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. .
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I - CIRCUIT CHARACTERISTICS
A.
Res istance and Reactance
of
Overhead Lines
Resistance depends primarily
on
the
conductor
size and
type
of
conductor
used. Reactance depends not
only
on the
conductor size but also on the equivalent delta spacing be tween
the conductors. Accordingly, Table 1 gives the physical and
electrical characteristics for commonly used overhead conductor
sizes and types of conductors.
The
conductor
reactance may be separated into
two
parts -
the internal reactance
of
the condu
ctor
including the area
around the conductor of one foot radius and the external
reactance
of
the
conductor
beyond the one· foot radius. Hence,
the total reactance X) per
conductor is
equal
to
the sum of the
two parts, or:
X • Xl X
2
in
ohms
per
1000
feet
Xl
;: reactance of conductor at one foot
X
2
= reactance of
conductor
beyond one foot
Table 1 gives the values for
Xl
for the various
conductor
types and sizes. Fig.
1
gives the va lues of
X
2
for various
equivalent spacings between conductors as may be used in
practice.
For ordinary single· phase circuits. the equivalent spacing is
the distance between conductors. For ordinary three-phase
circuits, the equivalent spacing
is
expressed by
the
formula:
~
x
B
x C where A, B and C are the di stances, center·to·
center.
of
the con ductors.
as
follows:
The reactances of three-conductor or triplexed cables may be
obtained by usi ng t he upper scales of thickness of insulation and
jacket in Fig. 3. For cables not in direct contact with each
other, use
the bott
o m scale (abscissa)
of
Fig. 3.
Example showing me
th
o of us ing Tables)
Given: A triplexed
50
0
MCM.
aluminum, 15 kV grounded
neutral , shielded and jacketed cross-l inked polye
th
ylene cable,
9OC.
From Table 2. D-C resistance at 25C
=
0.03538 ohms
per
1000
228
90
feet. At 9OC, the resistance would
be 0.03538
x 253 ..
0.04447 ohms per
1000
feet. The a·c correction factor
is
1.
06,
50 the a·c resistanct at 9OC 0.0447 x 1.06 =
0.04714 ohms
per
1000 feet.
From Table 3, Part A. The insulation thickness
is
175 mils. The
jacket thickness is 80 mi ls. An additional 100 mils shou ld be
added for semicon layers and shielding. (See
pa
ragraph C. w
hi
ch
follows.)
The
total thickness of insulation and sheath system
is
1
75
80 100
355
m
s.
From Fig.
3.
At the
in
tersection of 500
MCM
and
355
mils
(interpole between 350 and 400 mils), read 0.036 ohms per
1000 feet.
Underground Cables
To
assist
in
obtaining the spacings. a few typical arrange. C.
ments wit h their equivalent spacings are shown in F
ig.
2. The
arrangements used in practice wi ll vary from system to system,
For three·conductor cables, the insulation thicknesses
ordinar
ily
used can be obtained from Table 3, Parts A,
Band C,
and then the reactance can be
obta
ined directly from Fi
g.
3 at
the intersection
of
the cable si
ze
and insulation thickness lines.
On th ree-conductor cables an i
dentify
ing
tape is
frequently
applied over the insulation of t
he
individual conductors. Th is
tape
usually adds approximately 30 mils to the diameter of the
ooncluctor and consequently 15 mils snould
be
added to the
insulation thickness to find the correct value of reactance. For
inner semi·con tapes,
outer
semi·co n tapes and shield add 100
mils when this shielding system
is
used. Metallic tape insulation
shields generally add 10 to 30 mils to cable diameter. For sector
cables use a corresponding round
conduc
tor diameter.
but because of space limitat ions only these few are shown.
8.
Re
sistance
an
d Reactance
of
Cables
Cable resistances are given in Table
2,
and cable reactances in
Fig. 3. The reactance data
that
follow are based
on
the formula:
X ..
0.023
(loge K
X
=
Reactance in
ohms
per
1000
feet at 60 hertz.
S • Spacing of conductors (center·to·center) in inches.
D
=
Diameter of conductor in inches.
K - A coefficient dependent on the ratio of the inside
diameter of a con
ductor to
the outside diameter of the
cond uctor. For cable of standard·strand construct ion, K
equals 0 .25.
These reactance curves are co rr
ect
for shielded or non,
shielded cable without a magnetic bin der.
To obtain the reactance for three single condu
cto
r cab les
with random spacing in a conduit , multiply the reactance for
three
co
ndu ctor cable spacing (Fig. 3) by 1.20 for non·magnetic
oond uit or by 1.50 for magnetic conduit.
Reference on cab le ampacities are given
in
Section X under
Thermal Loading of Underground
Cab les
5
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Table 1. Physical and el
ect
ri
ca
l characterist i
cs
of open
-w
ire distribution line conductors
Size
I I
Diamele
L
o..
Aw,
Str ands) MCM
In I n.
1000 Fl .
Copper - Hilrd Drawn
,
111
16.51
0.1285
50
6
111
26.25 0.162
80
4
(3)
41
.7
4
0.254
.
2
(7)
66.37 0.292
205
•
(7)
83.69
0.328
258
1/0
(7)
105.5 0.368
326
2/0
(7)
133.1
0.414
4
11
3/0
(7)
167
.8
0.464
518
4/0
(7)
211.6 0.522
653
19)
250
0.574 772
119)
300
0.629 926
(1 9)
350
0.679
OS
AUSt
ee
l
ACSR
6
6/ 1 26.25
0.198
36.2
4
6/1
41.74 0.250
57.6
2
6/1
66:37
0.316
91.6
1/0
611
105.54 0,398
145.6
2/0 8/1
133. 1
0.447 183.7
3/0 6/1
167.8 0.502 231.6
410
6/1
211.6 0.563
192.1
2617
266.8
0.642 366.8
26/7
336.4
0.721
462.4
26/7
397 .5
0.783
546.4
26/7
477.0 0.858
655.7
26/7
556.5 0.927
765.0
26
/7
795.0
1.108 1093.0
(S l
rlnds)
AU Aluminum - Ha
rd
Drewn
4
(7) 0.232 390
2
(7)
0.292
62.0
1/0
(7)
0.368
98.5
2/0
(7)
0.41 4
124.3
3/0
(7)
0.
46
4
156.7
410
{7) 0.522
197.6
(7) 266.8
0.586
249.1
(191
336.4
0.666
315.7
19)
397.5 0.724
373.0
( 1
9)
477.0
0.793
447.6
(19
1
556 .5
0.856 522.0
37)
795.0
1.
026
N6.0
Copperwetd _ Copper
8A
0.199
74.3
6A
0.230
101.6
4A
0.290
161.5
2A
0.366
256.8
' Conducror af 80 C. 40
C
AMBIENT, emissivity
-0 .
5 for copper. 0.2 forlliuminum.
LOWl r
current
Vlllues correspond to
srill
air.
Higher
current
vlllues corres
pond
ro
air moving
it
two
feel
pilr
second.
o Resisfimce of
conoocror
in ohms/fOOD
f l, 60
hertz. C remp(Jrllture
-X reactance of
conduc
to r out tJ one foot III ohms per 1000 ft. 60 hertz.
Approx. Amp_
Cap ac
i ty
50 80
70 110
110 161
\45
2
0
170 245
200 285
240 335
280 390
330 450
375 510
425 575
475 635
55
85
75 120
110 165
50
225
175
260
210
305
245
355
290
410
340
480
380 535
430
605
480 670
620
850
75
115
105
60
.45 215
170 250
200 290
240
340
280
400
330
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300
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thickness of Insula ion
0.0
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250
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CHARACTERISTICS
Table 3. Conductor sizes,
in
sulation thickness and jacket thi ckne
ss
Part
B.
Rubber insulated cables *
Insula
tion
Thickness
Single-conduct or Jacket Th ickn llS
100
Percent 133
Percent
100 Porcent
133
Per
cen
t
Insul ati on Insul ati on
Insul
atio
n
Insulation
Circu it Co
ndu
c
tor Level t
Le
ve
l'
Co
nd uctor
Level t
Con ductor Lavel
age
Size,
(Grounded
(Ungrounded
Size,
IGr
ou
nd
ed
Size,
(
Un
gr
ou
nd
ed
o ·Phase,
A WG or
Neutral
Neu
tr
all
AWGo.
N ....tr aJ)
AWGo
. Neutra l)
s
MCM m
il
s
mm mit s
mm
MCM
mils
mm
MCM
ml S
I
mm
0·600 1
8·16
30 0.76 30
0.76 18·16 .. .
.. .
.
..
.. .
1
4-9
45 1.14 45 1.14
14
·9
15 0.38 15
0.38
8·2
60
1.52
60 1.52 8·2 30
0.76 30 0.76
1-4/0
80 2.03 80 2.03
1-4/0
45 1.14 45
1.14
225·500
95 2 .41 95
2.4 1 225·500
65 1.65
65 1.
65
525· 1
000 110
2.79
110 2.79
500·1000
65 1.65
65
1.65
Over-IOOD
125 3.18 125
3.18
Over.1
0ClO
95
2041
95
2.41
14
·8
60 1.52 60
1.52
7·2
80 2.03 80
2.03
1
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Table 5. Fu ll-load currents o f transforme
rs
in am peres
Single-ph. sl Circu lls
Circ uil ~ t O
'VA
1
20
24
0 480
2400 4160
4800
7200 762
0 12,000
5
41.7
20.8
I DA
2.08
1.20
1.04
0.69
0.66
0.42
10 83 .3
41.7 20.8 4.17
2.40
2.08
1.39
1.31
0.83
15
125
62.5 31.3 6.25
3.61 3.13
2.08
1.97
1.25
25 208 104
52.1
ID
6.01
5.21
3.48 3,28 208
37,5
3 3
156
78. 1 15.6 9.01
7.8 1 5.21 4.92 3.12
50
417
208
104
20.8
12.0 10.4
6.94
6.56
4.17
75 625 313 156
31.3
18.0
15.6 10.4
9.84
6.25
1
00
833
417
208
41.7 24.0 20.8
13.9
13. 1
8.33
167
1392
696 348
69,6 40.2
34.8 23.2 21.9 13.9
250
2083 1042 521
104 60.1 52.1
34.7
32.8
20,8
333 2775
1388 694 139 SO.O
69.4 46.3
43.7 27.8
500
4167
2083 1
0
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DISTRIBUTION SYSTEMS FOR RESIDENTIAL AREAS
Table 7. Ty
pi
cal dat a for single-phase triplexed 600V service cable, crosslinked polyethy lene
in
sulated
Overall
I
mpeda
n
ce -
Ohm s
Size_AWG Cable
per Condu ctor
% Volt age
Reg ul
ation
or MCM Diamel&r
per
1000
h .
p r 10,000 a mp.h .
Ampa
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8/20/2019 GET-1008L Distribution Data Book
10/35
Wy
e-delta Banks
I
t
the high-voltage neutral of the transformer bank is
to the
circuit
neutral, the transformer bank may burn
theJoliowing
reasons:
1. It will cafry circulating current in the delta in an attempt
to
balance any unbalanced load connected
to
the primary
line beyond it.
2. It will
act as a grounding bank and
will
supply
fault
current to any fault on the circui l
to
Which
it is
connected.
3. It provides a delta in which triple harmonic currents will
circulate.
All of these effects cause the bank
to
carry current in
to its normal load current, and often this combination
sufficient to cause roast-out of the bank.
When this transformer connection is used, and the high .
neutral of the transformer is not connected to the
neutral,
an
open conductor in the primary results in a
phase input
and
output
of the bank.
If
the transformer
motor
load, a harmful overcurrent
is
produced
in
each
motor circuit. An equal current flows in two
nductors of the motor branch circuit. and the
sum
of the two
flow in the
third
conductor.
The usual overload protection in
motor
circuits consists of a
device in only two
of
the conductors.
If
the highest
the three currents happens to be in the unprotected circuit,
will very likely occur.
If a th ird overload device is installed in each motor circui t.
t
he
likelihood
of
motor failure from this
cause is
is
he probability of an open primary line to the
Such a probability is effected by the kind of
and protective arrangements used in that part of the
Dclta -wye Banks
T
he
comments about
motor
pro tcction in regard to wye·
.
Open·wye, Open-delt a Banks
Distribution lines in rural
areas
often consist of two phase
and one neutral wire. In urban distribution it
is
sometimes
rable
to have multi
·phase, where only single-phase primary
is
b
le
and the second
phase
wire
is
installed. These lines
nate from three-
phase.
four·wire, ground·neutral systems
are known commonly as V' ·phase lines. T
he
major
of
the load laken
from
these
V ·phase
lines
is
but
occasionally it
is
necessary to supply three·
motor
loads from
these
lines. in addi tion
to
a single·phase,
/240·volt connection.
Since both transformers carry the three·phase load, and one
the single·phase load in addition, the latter transformer
be
the larger unit. It must carry the vectorial sum
of
the
of the three·phase load, while
e smaller transformer must carry
only
58 percent
of
the
For example, i f i t is desired to carry a
·phase load of seven kVA and a three.phase load of f ive
kVA.
where the loads have the
same power factor
transformer
sizes are arrived at as follows:
La rge
Smll il
Transformer Trans
fo:mer
Singl
e·
phase 1000
7 kV A
Three-phase load
(0.58 )
51
2.9
2.9
9.9
kVA
2.9
kVA
Required transf
ormer
size
lQkVA
3 kVA
These sizes are based on the assumption that the loads are
continuous, steady·state loads. In actual practice. this is seldom
the
case.
Some judgment can
be
exercised, depending upon the
knowledge of actual load conditions. as in the selection of
transformers for any other application.
5. Open-delta , O
pe
n·de
lt
a
Ba
nks
This connection is similar to open·wye, open·delta except
that the transformers are connected phase·to·phase instead
of
phase·lo·neutral. Selection
of
large and small transformer ratings
can
be made the same way.
6. Wye·wye Banks
A bank of wye·wye transformers should
not
be used unless
the system is four·wi
re.
It is important to remember that the
primary neutral of the transformer bank should be tied
firmly
to the system neutral.
If
this
is not
done, excessi
ve
voltages may
develop on the secondary side.
7. Caution
Single·phase, self·protected transformers should Jot be used
to supply three·phase, four·wire, closed·del ta circuits serving
combined three·phase power and single'phase lighting loads.
If
the secondary breaker in the lighting phase opens, the lighting
phase is
still supplied with 240 volts. With the breaker open,
however, there is nothing to hold the low·voltage neutral at the
midpoint between the 240 volts. The voltage betweef) each
phase
to
ne
u tral will depend on the relative impedance of the
loads connected
on
either side
of
the 120/240·vol t circuit. Since
lhese
are
rarely equal. the lam
ps
on one
side
will probably burn
out from overvoltage.
D. Autotransformers
A considerable saving in cost may often
be
effected by using
autotransformers instead of
two
·winding transformers.
When
it
is
desired to effect a comparatively small voltage change. or
where both voltages are
low
, an autotransformer can usually be
used as successfully as a two·winding transformer.
Autotransformers should not. except under special con·
ditions.
be used
where the difference between the high ·vol
tage
and low
-voltage ratings
is
great.
because
the occurrence
of
g ounds at certain points w ill sllbject the insulation on the
low·voltage circuit to the same stress as the high-voltage circuit.
Auto transformers are rated on the
basis
of their kVA output
rather than the transformer kV A . Efficiencies. regulation and
other electrical characteristics are also
based
on output rating.
IV
- SHO RT-CIRCUIT CALCULATIONS
A. Line Impedance
When the resistance AL and the reactance
XL
have been
determined, the impedance, ZL' of a circuit
can
be obtained
from the relation ZL .. JAL 2 + XL 2.11 limited only
by
a circuit
impedance, the short·circuit current is as follows:
Three ·phase fault = m p r s in each phase.
v3 Z
L
line-Io.neutral fault : -,;=,E--_ amperes, assuming that the
v32ZL
impedance of the phase conductor and the neutral conductor
are
equal and that the phase conductors are arranged like the
points of
an
equilateral triangle with the neutral conductor
an
equal distan
ce
from all
phase
conductors.
l ine
· o· ine fault = am
peres
L
wher
e:
E
=
line·to·line voltage
Zl '
line to neutral impedance in ohms. or the impedance
of
one conductor to the point of fault.
B. Transformer Impedance
It is frequently necessary to take
into
account the effect of
step
·up or step·down transformer banks. The impedance
of
delta·wye, wye·delta. and delta·delta transformer banks should
be
combined directly
with
conductor impedances in calculating
short·circuit currents. The transformer impedance, which is
usually given in percent, will have to be converted to ohms
before it
is
combined wi th the line impedance. This can
be
done
with the relation:
n
10E2
Z - _ '' ' '_
lI - kVA
where:
ZT n ' transformer impedance in ohms
ZT% • transformer impedance in percent
E - line·to·line voltage in kV
kVA = rating of the three· phase transformer bank
The short·circuit currents
for
the combination of line and
transformer
are:
Three·phase fault Vi E amperes in each
phase.
3(Zl
+
ZTn'
Line·to·neutral fault
= ..Jj(
E amperes wi th the
3(2Z
L
+ ZTn'
same assumptions as given under line impedance.
Line·to·line fault ' 2 (Zl .; ZTn amperes.
-In
the case of a multi·grounded
neutral system the
impedance of
the
neutral is
somewhat
less
thao that
of a phase
conductor
of equat
s i ~ e 10
f
igu
ring the impedance of a multi·
grounded
oeutr&1 conduc
tor
, a faCIOr
of 2 3 is sugge ted. because of
the
multiple
path
for
the return
current.
C. Impedance of lines with Different Voltag
When it is necessary to c ombine a line and
impedance with the impedances of another line
of
voltage, the impedance
of
the new line must be
put
o
voltage base as the or iginal line. This
can
be done by
the impedance of the new line
by
the ratio of the sq
line·to ·line voltages of the transformer connectin
together. It must
be
remembered that the ohms
var
ies directly as the voltage squared. Therefore, in
g
l
ow
voltage
to
a higher vottage, the impedance
will
in
vice·versa. The transformer line·to·Hne voltages sq
must
be
taken so that this will be the case.
D. Effect of Offs
et
The magnit ude of the short·circuit current, as
from voltage and impedance values, does not
represent the rms value of the current
for
the first
because of
the fact that the current wave may b
unsymmet r ical
with
respect to its zero axis. The rm
the first half-cycle increases
as
the amount
of
offse
For constant reactance circuits the maximum value
rms
of
the offset current wave
can
attain
with
respec
of the symmetrical current wave is a funct ion. a
things, of the reactance / resistance ratio of the circu
point
of
fault .
tn the Transactions
of
the American Institute
o
Engineers (Vol. 67, 1948) paper entitled
Simplifie
rion of Fault Currents are the various multiplying
be used
with
the currents calculated by the form
These
are t
he basis
of the values shown in Table 9.
When applying circuit breakers, circuit reclosers,
expulsion arresters and fuses. the formulae for the t
which
will
give the highest value
of
rms symmetr
should be used. Then the multiplying factor in Tab
be
applied to determine the rms current which
compared with the rating of the device.
The relationship shown by the curve in Fig. 7
give
that
can be used
in calculating the maximum rms
first half-cycle of fault current. This curve can be u
of Table 9 for checking the suitability of the interrU
of fuse cutouts and reclosers when the circuit con
particular installation
are kno
wn.
Ratio of for Sl,lbstation tr llnsformer plus primary ci
R
exceeds
4 and ts
usually 1
to
3.
Fig. 7. Mult iplying factot
for
det&rmining short ·circ uit
rlll ·ampete·rated devices, such as distribu tion cuto ut
cal
cu
l
8ted Vmm
otrical sho
rt
·c;rcuit
cu
rre
nt
-
8/20/2019 GET-1008L Distribution Data Book
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Table 9. Circuit breaker
s,
circuit reclosers. distribution expulsion a
rr
esters and fuses
Reacun
-
8/20/2019 GET-1008L Distribution Data Book
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CALCULATIONS
•
220
'&D
..,
•
COPP R CONDUCTORS
LU
MINUM CONDUCTORS
': fN _ __ r
i
1
Y ' l ' f I Y f : l J
} t · ~ f
.-
..
.. .
••
,-
. n .. ;
,;;;;
•
•
: ' 1
•
I·
.
-
1-
'"
-
-1000
,..., _no
-'
.
•
Rr ....
N t y e e .. ..
,
, .
..
. . . .
Ou. .
.. c ~ [ O '>
[ . ,.,
..
,.
,
- - t t t t - t - t - i . O ~ H
' e (. ·'
.. 00.
,
.....
,.
t .
0 . ,0 >0. ·7>.·
100 ]0
, CTeL[ .. .
.CTC , EHU • •
:
---{
-{,
, ,.>i-.d -o,;,.,-,,
O,
.
t, . ;('
lIO 10 ,>0 • >0 0.00
•
_I -r- _ 40
,000
'0
.,0
c . . . . $I owe 00 .. e .
' >0''''
111
,,.
Fig. 8. Maximum siZes of insulated copper and alum inum conductors for a conductor t emperature change from 75 C initi
al
to 200 C final during a short·circuit·cu rrent interrupting interval .
A'
.
•
..
:Yf
.
;,:-'
1
..
~
/$
){ .;p
-
-
4. Application
Proce du
re
Step'
- Evaluate the symmetrical short·circuit current
Step 2 - Knowing
th
e clearing time
of
the protective device,
determine a correction fac tor Ko from Fig.
1' .
Mult ply the symmetrical current by factor Ko to
allow for the d·c component
Step 3 - If the problem involves
an
initial temperature other
than 75 C
or
a maximum short·circuit temperature
other th
an
200 C a correction
fa
ctor K
t
should
be
obtained
from
Fig. 9. Multiply the symmetrical
curre
nt
(or its corrected value from Step 2) by the
factor K
t
to allow
for
different limiting temperatures
..
,10
'
.
.
Step 4 - Check the conductor
size
being considered on Fig.
Fig. 9. Corret:tion factors K
t
for initial and ma •.
short
·circuit
temperatu
res
.
,
,
,
'OTo
.
,u..
.'
,
,
,
, ,
, ,
10. Oscillograms showing dec ay of d ·c com ponent
asymmetry of current
and effect
01
S using the corrected value
of
current. The
permissible time should exceed the protector inter·
rupting time to
prevent
cab
le damage.
5. Examples o f Data Use
EHampl a 1 - Feeder ci rcuits are
to
be
run
fr
om
a 48D-volt, 6D-hertz load
center unit su
bst
ation. During
normal
operat ion it has been
decid
ed that a No. 2 AWG
Versato
l Geoprene Cable
(co pper conductor) will provide adequate current·carr ying
capacity. Evautalion indicates
that
the symmetrical shon·
ci.cuit
current
is
16,000
amperes.
The interrup
t ing
time
of
th
e c ho
sen
breaker
is
1.5
cycles
and it is desired to check
the cab le 's short·circuit capacity.
Sol
ution;
Symmetrical curre nt - 16,000
amps.
Time duration - 1.5 cyc les.
Factor Ko - 1.3 (
From
Fig. 111.
Corrected current - 16.00 0 x 1.3 - 20,800 amps.
In
Fig. 8
we
deTermine
thaI
a N
o.2
AWG
copper conductor will
wi
thstand 20,800
amperes for more
than
two cycles. The refore, an
interrupting time o f 1-
1/2
cycles
will
adequately prolect Ihe
cable.
E>
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8/20/2019 GET-1008L Distribution Data Book
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v - VOLTAGE CALCULATIONS
Voltage Drop
When
the
electrical characteristics of
the
line under con·
have
been
determined, the line
drop for
a
g i ~ n
of power-factor cos can be computed from
formula :
Volts
drop
= I fR
cos J +
X sin 0
here R and X are
the
total resistance and reactance,
of one
conductor
of the line under consideration.
formula
gives the voltage drop on one conductor, line-to
The three-phase line-te-line drop is..j3 imes the above
drop is tw ice the above value, To
drop in percen t, the fo l lowing equation
can
be
%
volts
drop = kVA
fR cosO + X sinO)
10
kV2
kVA
is three·phase kVA, R and X are the
total
resistance
of one
conductor
in ohms and
kV
is
·line kilovolts.
For
single'phase circuits,
kVA is
single·
kVA, R
and X are
total
values
for both
conductors, and
is
the
actual single'phase
kilovolts.
It
can
be seen from
the vector diagram
in
Fig. 12
that both
are approximate, but are close enough
for
practica l
In this diagram, is shown
as
the
powedactor
angle at the
of
the feeder because,
on
most
distribution
feeders,
is
the
only lo
cation at
which
the power factor
of
the load
be
measured.
To assist in the application of this formula, Table 11 has
le gives
the
values of ,sines, tangents, and
l
es
which correspond
to
cosine or power·factor values
from
O.
In actual practice, loads are usually distributed over the
rather than concentrated at one end. When this is the
simpl ifying assumptions can often be made. These are
own in
Fig. 1
3.
For instance,
if
a load
is uniformly distributed
the
drop to
the end
of
the tine
is
the
same as if
to t
al
load were concentrated at a
point
half
way out
on the
. Th is is mathematically correct
for
a very large number of
For a small number of
distributed
loads the error may be
When the load can be divided into a number of large
loads
distributed
along the tines,
it is
possible to
lin
e
into
the sections between loads
for
calculation
to
consider each section
individually
w
ith
the
hich
it
carries.
If there is
distributed
load
on
a line and it is desired to
find
voltage
drop to
some
point on
the line, the
following
will be
helpful:
kVA
(R
cosO+X sinO)
Ll
% volts drop = 2
10
kV
e re:
kVA
"
total
three·phase load
in
L l ine
A • resistance per 1000
It
X '" reactance per 1000
It
'
source power' factor angle
L l • distance
from
source
to
desired
point
in
thousands of feet
L . total length of line in thousands of feet
CoI(ula led d,ap
Fig.
12. VlI(:
lor diagrem
~ ~ = = : : = = = = = = = O ~ ~ r ~ ~ = = ~ ~ ; :
v,
,.
B. T
ab
les for Estimating Voltage Drop
Voltage drops
for
open·wire and cable circuits can be
quickly
estimated by simple calc
ul
ations and
use of
the foflowing
ampe
re · eet tables. The values given in the tables are the
absolute difference in voltage (voltage drop) between sending
end and receiving end line·
to
·neutral voltages
of
a balanced
three·phase
circuit for
each 100,000 ampere·feet of combined
load and circu
it
length. Tab le 12 covers standard. open·wire
three·phase voltages used for distribution. A wide range of
spacing is use d to cover various line construction. Table
13
gives
similar
information for
various
classes of distribution
cable
voltages.
1. Th ree ·phase Prob lems
In using
the
tables. the
first
thing required is
the
number of
ampere·feet involved
in
the problem. This
is
obtained
by
multiplying
the amperes per phase by length
of circuit in feet.
Divide this ampere·feet by 100
,000
to determine the multiplier
to be used
wit
h values in the tables. For the
proper
voltage,
conductor s ze,
conductor
material, power factor, and
conductor spacing (interpolate, if necessary) find the vol tage
drop factor in
the table and mul t
iply by
the
multiplier
determined previously. Th is
will
be the absolute line·to·neutral
volts
differe
nce (drop) between the sending and receiving ends
of the
circuit.
Dividing
by
l ine·to·:1eutral voltage
of
sending end
So . e. LlRt
(A)
tatle
t
M,a
l
t
-
8/20/2019 GET-1008L Distribution Data Book
14/35
Tabl
e 12.
Voltage drops of open_wire
lin
es
in yolts
per 100
,
000 ampere le et Inote
1)
SYSTEM VOLTAGE CLASS
-,
(qui
000,. _ ' ",",. 21
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Table 13. Vo ltage drops
of underground
cab l
es
in volts per 100 ,000
ampere
feel see note
CABLE VOLTAGE CLASS 000 V
V
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18/35
VI
- VOLTAGE REGULATING EQUIPMENT
. Selection of Regulator
The
two
fundamental factors
of
service, from both the
r's and the operating company's point-of-view,
is
the
of continuity and as nearly a constant vol tage
as
is
economically possible. To the consumer,
an
in
voltage regulation means greater satisfaction
electric devices and a stronger incentive
for
extending the
of electric energy. To the operating company, an improve·
in voltage regulation results in greater customer satisfac
greater goodw ill towards the operating company, an
of service rendered, and a higher
average
vol
tage
ich results in higher revenue to the company for the
va lue of connected load. Where the load
is
chiefly lighting
as in residential areas, this variation
in kW
·hr
will
be most pronounced .
Fig.
14 gives the
on typical circuits.
. Type
Several different types of equipment are used to maintain
roughout a system. This equipment can be
into three major classes:
1.
Source voltage control; generat ing station bus voltage
control.
2. Voltage ratio control.
a. l oad tap changing transformers
b. Step voltage regulators
c. Induct ion voltage regulators
3.
Ki
lovar control
a. Synchronous condensers
b. Switched capaci tors
The l ypes and sizes of the equipment chosen depend upon
of the load and the characteristics of the system.
It
should be recognized that
the
easiest and least expensive
et hod of system voltage control
is
by variation of the
X
>14
L
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AS5umpliOM
Feeder load loc
i
or
• 0.30,
pI
=0.95
UQhlillQ
l
ood
5 ° 1
10 10 1.
VolloQe
drop ofteelillQ all lighlinQ
lood
7 °1
0 1
drop
01
o
ron uat
p ak
R ...e
llu
. fro m incr o s d
loo
d 0 1
3 c
p.r
kWh
200
,
generating station bus voltage, using the generator field control.
Although fun use shou ld be made of th
is
method of voltage
control, this met hod alone does not meet all of the require
ments of the system. To meet the system requiremen ts most
utilities use,
in
varying degrees, a combination of
au
tomatic
voltage·ratio and kilovar control or. as applied here, regulators
and shunt capacitors. The question arises as to how much
emphasis should be placed upon each of these methods of
voltage control. The technical functions that can be performed
by regulators and capacitors are given in Table 14.
2. l ocation and Size
To determine the correct location and size of the regulator,
the loading and voltage characterist ics of the circuit should be
known. Also, the voltage conditions from the substation to the
end of the feeder should be known fo r b oth the peak and light
loads. These voltages may be measured or t hey may be
calculated if the following are available: a circuit diagram which
shows
the
size, spacing, and length of conductor;
an
indication
of at least the most important loads and the phases to which
they connect; and a notation
as
to whether the loads and
circuits are single-phase or three·phase.
The size of the regulator depends upon the load which it
must carry and the percent of voltage regulation. Therefore it
is
necessary first to determine the proper location for the
regulator. In determining the location for a regulator it
is
adv isable to consider
the
effect of load growth as well as present
loa
d condit
ions_
If a voltage profile based on a reasonable
estimate of
fu
ture load
is
made and compared with a vo ltage
profile based on present load, a determi nati on of the extent of
voltage control requ ired with time can be made. A regulator
that is sized and located in accordance with this procedure
will
provide proper voltage correct ion for present and future load
conditions. See Fig. 15.
. , ~
00 XlO
2000
XlO
Example: Compensating for a 5-percenr drop at yearly peak load
o
600 kVA increases the annual revenuB $f 250.
Fi
g.
14. Dollar< reve
nu
e
pe
r yea r r ecovered b y
compe
nsating
fo
r vo lt age
dr op a t yea
rly
peak
t
oa
d
VOLT GE REGUL TING E
Table 14. Function pe rformed by re gulators and ca pa citors
P
trlo
rmed By Perfor
...
d By
FI,nc.
ti
on
Voltage Ra To Con
ol Kilo"a. Cont rol
Commllnts
Vo ltage Reg
ul
aTOf
$)
)Switched Capaci to.s
L
c.,
raise and lower OUTPUT VOLTAGE. YES YES '
·
No
inherent
with switched capacit
Or<
bu
this eHect by being swllched off ,
,
Carl rilise
SVSlem
voltages on source or i
"put
NO
YES
side of regulati"g mea"s .
,
Capable
.
stepless
"
small voltage step
YES
NO'
·
Not inherent with switched capaCitors.
bu
control.
duce
small c h
ar>ge5
in vollage if
ba"k
s i ~ e
system
impeda...::e to ba"k is small.
4.
Capable
.
mai"tai"i"g a
±
314-volt band·
YES
NO'
Switched capacilOfs do not usuallv pefmit
w.dth,
bandwidth,
5.
Capable
of
many SWitching operations with· YES
NO'
·
Capacitor switch contacts deterio'Dle
ra
oul
l'eQuent inspec tion.
large numbe,
01
switching operatio"s per da
6.
Reduces 12R loss lI"d 1
2
X loss in system . NO'
YES
·
Not
inherent with uoltage regulators but s
tion in losses may rasult on output side b
,"creased volta{le.
7.
Reduces thermal loading. NO
YES
8. Raises
system
loading capabililV.
YES'
YES
·
Voltage
regulat
ors
will raise
the
loading
ca
output
side
but
will
0"'
raise loading ca
system
on
input side.
NOTE : Neilhe, egulerors nor cepacitofs by themselves can fulf il l all
of
these desired funct,ons. However, used
s a
c ~ m b , a l , o n , ,the twO
voltage
control
can
maintain
relati vely
flat
feeder voltage
profile and
at the same
time
reduce system
lones and provide for
com,derable s
grOWlh on the feeder.
The amount of kVA of regulation required for a single·phase
regu lator
in
a single'phase circuit can be determined as the
product of percent vol tage regulation and the total circuit kVA
beyond the regulator div id ed by 100
(see
Fig. 16.).
A three-phase circuit can be regulated by one th ree-phase
regu
lator, two single-phase regulators, or three single·phase
regu lators. Fig. 17, 18, 19, 20a and 20b show the connections
fo
r the different methods. There are two types of th ree·phase
regulato rs:
a. Three·phase core·and·coi l construction with three·pha
se
switchi
ng
mechanism.
b. Triplex. Three separate single·phase units mechanically
coupled within one rank.
The amount of kVA of regulation required for wye·
connected three-phase regulators
is
equal to the product of
percent voltagE regulation and the circuit kVA beyond the
regulator divided by 100 (see Fig. 17.).
•
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TAGE REGULATING EQUIPMENT
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REGULATING EQUIPMENT
Singl '
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Rleiprotall
ng
Cron
Pumpi
.
,
Compr,,,or.
,
Automalic
;
Spal_wlld .
,
1\
,
-
-
-
-
1 -
-
,'
"-
,
"
;
"
-
......
1
/ ~ " " ' "
r - '-t
I
I ,
r -
,
,
.......
,
r-
A
o
'0
-
I ,
i
or
: M ~ o :
I
01 I "
'0 "
' I '
i li ' 1
,
I'
,
I
,'''0'
1
olid Lines
composi
te curves
of
voltage f(icker
studies by
General Electric
Company.
Gener; 1
Electric Rev iew
August
1925;
Kansas City
Power
&
Light
Company, Electrical World
May 19,
1934;
T.
& D. CommiHee, EEl, October 24,1934,
Chicago;
Detroit
Edison
Company;
est
Pennsylvania Power
Company; Public
Service
Company of Northern
Illinois.
DOlled Lines voltage flicker
allowed by two
utilities, references Electrical
World November
3,
1958 and
June
26,
1961.
Fig. 24. Relations of voltage fluc
tuat
ions to frequency of their
occur
rence iincandescent lamps)
consumption corresponding
to
a given connected load.
amount
of
increased revenue resulting
from
the additional
can
be calculated using the
following
formula:
'"
Voltage·sensitive kW·hr Load
Total kW-hl'
load
voltage reduction in band width x load factor x annual peak
x rate in cents per kW-hr.
01 bandwidth
of
one
or two
volts. A change in revenue
from
large voltage changes can be determined by
Fig. 14.
time
delay should
be set
so that a proper compromise
the number
01 tap change operations and the
control
desired. I the
time
delay is
too
short, the
will operate excessively
by
responding to
voltage changes. It is recommended, then , that the
of
operations
be
controlled
by
changing the
time
delay,
than
by
varying the bandwidth.
regulators are cascaded on a
circuit
the regulator
to the source should have the shortest
time
delay setting,
time delays should be increased for regulators. located
is set lor the
from the source.
3. Volt
-
8/20/2019 GET-1008L Distribution Data Book
21/35
Burning lamps
may
be extinguished if voltage drop to appro>:;·
75 percent o the ,ated
ine
voltage.
Fig. 27. FllIores
-
8/20/2019 GET-1008L Distribution Data Book
22/35
OF SHUNT CAPACITORS
p., wnll (a pocUot kVA • .Y
kVA ,
mple: Assume
II 5Q()(}--k
VA SUbstatiorr has II load power faeror
of
0.70
that 2000
k
VA
of
,,pacitors IIf. applied.
The Pf/f·uni t
capacitof
k VA
- 0.40
for which
the
feleased
capaci
tv IH 0.70 power
f lewr
per unit or
(0.24
x
50001 - 1200 kVA. Also
it may be
noted
rhe
dotted
ines) {niH
the
final power faclo
r is IIbOUI 0.92.
Fig.
32.
Thermal ca pacity re lEtlsed bV application0 1 ca pa
-
8/20/2019 GET-1008L Distribution Data Book
23/35
OF SHUNT CAPACITOR
S
ble 17.
App licat ion guide for group-fusi ng capacitor banks with Genera l Electric uni
ve
r
sa
l cab
le-
type and oil
cu tout fuse link rati ngs N, O
IL
, K, and T types
·WVE ANO DELTA CONNECTIONS
BANKS
W
ITH l00
·
KVAR
UNITS
.
. V O I I $
.
4160 Valli 4800
Voln 7200 Vol
.
12470 Vo u.
13200 Volt. 13800 voru
l(u.. N/D,I - '(' T NID,I
."
NIDi Kn"
N/D,I
Kn"
W O r
Kn"
NIOli
Kn"
NID il
."
' ,00
100
/-
50
57/60
50
,.
25 25
25
25
00
-
1
00
/-
-
tOO / -
8s/ tOO
50
.
50
,.
30
-
100
1-
50
50
50
9
51 100
80/ - 851100
85
/ 100
I
-
100/
-
-
100/-
'
100
/-
-
'00 1
-
'00 1
-
'00 1
,
TOR SANKS
WI
TH 25 ANO
50
KVAR
UNITSI
2400
Vol
41
60 Volts
4800
Volls 7200 12410 Yolts
13200
Volts 13800 VoU,
e
1(
3
NID,I
'
N
ID
,I
m
Nl
a,1
m
N/Dil
m
NIO
,I
m NIOil
."
N/D
il
."
,.
2. 2.
.
..
50
/-
.
25
,.
25
2
.
.
7&
/60 501 -
50
.
JO
20
2.
2.
2.
>2
713
1-
501-
75/ -
501-
,.
25 25
25 25
B51-
65/ -
75/ - 501-
50
JO
2.
30 2. 30 2.
75/ -
501
-
,.
25 25 25
75/ - 501-
.
25
,.
25
,.
25
85
65
/-
50
.
SO
,.
30
S
f
50
/-
SO
,.
0
,.
15f 50 /-
75
/- 501-
50
,.
75/-
50
1-
75
/-
501- 75/60 501-
15/- SO/ -
75/ - 501- 75
/-
501-
75
/-
SO
/- 75/ -
501-
75
/-
501-
85 /-
65/
-
75
/-
501
-
'51
-
50
/-
15
I
851
-
65
/-
851 -
651-
85
/-
65
/-
651- 85 /- 65/- 85
/-
65
/-
100 h .. ' ' ' . / .u/ll; ,' . , ould nOf
uned
SOOO .,.,,,e" f.
15 ·
,
,,,d 1 r ~ . J ' ' ' . 111.111 ' u em
.
hould
nOI eX
;eed 4()(}()
m{Jt'n .
For . ,gll1''', oI'l1 (; iH: or b;mlr .
Ihe .m
gle·
ha
. e
k ~ a , '041 '9 3 10
obI
' II,,,
I1Q
.. l l 1 n r
3· , .11
,. ng. and mul /l ' Ih
''''9Ie. h .
by 1
131
0 o
m ,,,
I
he
nJ
l 1m 3· ha. ~ o l l ~ g t I 'al,n9_ SeIeOO,
, ... 0 ' .
'
Fig. 38. Proposed ch
aracle
rislil;S 01 150 ·, 200 ·,
an
d 3OO
rated 2400·1960 ~ o l
-
8/20/2019 GET-1008L Distribution Data Book
24/35
OF SHUNT CAPACITORS
Application guide for group-fusing capacitor banks with General Electric universal cab le-type and oil
cutout fuse link ratings N, OIL, K, and T types
FlOA.TING ·WYE CONNECTION
CAPACITOR BANKS WITIi
25.
50 ·
OR l00
· KVAR
UNITSIt
4160
Volt.
4800 Voh.
7200 Voh.
8320 Vol . 12470 Volts 13200 Vol .
13800 V"II>
J. h
.. Ky
. "
NIO,I
'
"1/0,1
'
NI
Oil
'
N{Oil
'
NIOil
'
NIOil
'
1,0,\
'
,
-
- -
40130
' ' ' '
,
,
,
'
45140
' '
'
'
75160
'
'
'
85175 45/50
'
' ' ' '
'
,. -
-
85/-
-
40/ -
' '
-
'
951-
-
75/60
'
'
.,
,.-
75160
'
451.0
'
4
5
40
85/ -
'
'
45
150
'
45
150
'
''''
95/-
-
85/-
~ I '
,
'
'
951-
-
,.-
'
~ I O O
' ''''' '
00
'
'
95/_
-
75 60
'
75 60
'
-
'
'
' '
'
151-
,. -
151_
'
125
851
-
'
'
'
851-
'
,.-
'
75/-
'
215 -
851 -
'
85
1-
'
,.-
-
,. -
-
,.-
425
,.-
-
95
/
-
,
'
,. -
-
- Application guide for group-fusing capacitor banks with General Electr ic universal cable-type and oil
cutout
fuse link rat ings N, OIL, K, and "TH types
·WVE
AND DELTA CONNECTIONS
I
TOR
BANI{S
WITH
150-, 200· AND 300·I( VAR UNITS
'
'
'
''''
''''''
00 ' / -
100/ _ 85/100
200'/
-
2 - ~ , . o c up ,
..
_
a/xl
. 25()(}ampe
Orf circulr curren .
1
>
15
25/25
4(1/40
'''''
5/65
95/95
100/ '00
125/ 100/ 1
00
125/
100/100
150/ 140/ 1401
150/
140/1401
200'/
-
e 20 - Application guide for group-fusing capacitor banks with General El
ect
r
ic
universal cable-type and o
il
cutout fuse link ratings
N,
"OIL
, K,
and
T
types
FLOATtN
G·WVE
CONNECT
I ONS
CAPACITOR SA NKS WITH 150-
zoo.
ANa 3
00
I{VAR UNITS
3·pIo_
4160 Votu
4800 VolU
7200
Vot .. 8320 Vol "
12.410
Vol
13.200 Vott. 13.900 Vol ..
K•• •
N/o;l
'
N/o;l
,.
N/o;l
'
N/o;l
'
N/o;l
'
NfOil
'
N/o;l
'
.'
951100
'''''
,. -
65/65
'
40140
"''''
40140
,.'
25125
;ro/20
-
20120
'
- -
- -
75175 751€0
.,,'
45140
:1()/30
4
0/40
25125
2 >125
'
- -
-
-
100/100
-
,. -
,.'
'
'
,.'
"''''
"'-
40/
40
,
'
- -
- -
- -
-
-
8 >1100
65165
,. - 65165
,.-
'
'
- -
- -
-
- -
-
951100
'
,. - 65165
,.- 6 >165
-
- -
- -
-
1001100
-
10011
00
- -
VIII LI HTNIN PROTECTION OF DISTRIBUTION SYSTEM
A.
Primary Distribution Systems
Continual research in the laboratory and in the field on
lightning and its effects on circuits and apparatus has established
the fundamentals of lightning
protection
so well
that the
careful
selection
and
application of modern arresters will provide
distribution systems with a high degree of immunity from
lightning troubles.
Adequate lightning protection of distribution systems
depends upon three major considerations:
1. The selection of distribution transformers
and
other
distribution
equipment that
have an insulation strength
to
lightning voltages
not
less than present·day basic insula·
tion levels.
2. The selection of arrester ra t ings which will limit
the
lightning stress
to
a value well below the standard
impulse-withstand level of
ap
paratus .
3. The effective application of the arresters, by mounting
them in close
shunt
relation with the apparatus
to
be
protected and, whenever possible, interconnecting
the
primary arrester ground to transformer secondary neutral.
1. Impulse Withstand Level
to
be P
rotected
ANSI basic in sulation levels and withs tand test values for
electrical apparatus are shown in Table 21. For example, this
table shows
that
the primary winding of a 15·kV voltage class
distribution transformer must withstand a
1.2
x 50
tlS
impulse
full ·wave test of
95
-kV crest
and
a chopped·wave
test
of 11O·kV
crest.
Conservative protection for a distribution transformer
throughout
its service life generally requires