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Bachelors Theses Student Theses and Dissertations

1923

Design of high tension outdoor substation Design of high tension outdoor substation

Joseph Worley

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Department: Electrical and Computer Engineering Department: Electrical and Computer Engineering

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DRSIGN OF HIGH TENSION OUTDOOR SUBSTATION

BY

A

THESIS

submitted to the faculty of the

SCHOOL OF MIKES AND METALLURGY OF THE UNIVERSITY OF MISS~

in nartial fulfillment of the work required for the

Degree of

BACHELOR OF SCIENCE IN ELECTRICAL ENGINERdING

1923

£ W~- .. ..

Apnroved by--- ..E...- ----,~~c:;..-~......-~-----Professor of Electricaf ~ngineering.

DESIGN OF HIGH TENSION OUTDOOR SUBSTATION

This thesis deals with the selection and arrangement of

the equipment used in high tension outdoor sUbstations.

Joseph WorleYe

TABLE OF CONTENTS.

Introduction.

Selection of equipment.

Calculations or tension.

Bibliography.

Substation drawings.

Indp.x

-1-

Page2

5

15

21

37

Suggested Procedure in SUbstation Design

aMental picture of layout.1.bSingle line diagram of connections.

aSelection of equipment,with given capacity and loado

2.bSnacing and influential factors must be considered.

3,aSketch and indicate the equipment in its selected place.

Equipment includes oil switches,transformers,suspension

disconneeting swicches,buses,ligbtning arresters,and

choke coils.

4aDetails of above should be drawn freehand in order to

'get an idea of the proper arrangement and the necess-

ary 10cations.It might be we~l to cut out some small

templets and arrange them in the best order that would

give the proper spacing required.

5QClearances should be cheeked.

Size of wire and size of buses must conform with minimum

allowable values.

Insulators must be of such strengah in order to with-

stand any mechanical or electrical strain.

eaAll equipment must be checked up for final selection.

7a.A material list should be drawn up including all equip-

and necessary apparatus used in the SUbstation.

BaDesign should be started at the transmission lines and

and finished at the secondaries of the Toltage trans-

rormers.

-2-

The present day tendency appears to be toward the more

rrequent use or outdoor sUbstations.Where not only the

section disconnecting switches,but also transrormers,

lightning arresters,and indeed all high tension equip­

ment,are exposed to the weather.The eontrol or loeal

feeder eircuits at the lower pressures would be by means

of switch-panels in cheaply eonstructed houses ereeted

near the transformers.

When the Toltage is high, the clearances required by the

high-tension leads and bus-bars within a substation may

require a large building and henee a considerable invest­

ment.The investment in equipment and in buildings situat-.ed along transmission lines and supplying small loads

may be large eompared with the kilowatt-hours consumed.

Substations ror small loads would not be economically

possible were it necessary to place all the apparatus

within a bUilding.Transformers,switches,lightning arrest­

ers ,have been designed so that it is possible to operate

them out of door••Tb~ bUilding needs only to house the

switchboard and the operator,ir one is necessary.The oil

switches, the light*ing arresters, the transformers,and the

bus-bars CaD alr'lbe placed out or doors.The apparatus

must be prachically air tight to keep out moisture.out-

door SUbstations on a large seale are highly developed at

the present timeo

-3-

A very desirable arrangement of the transmission lines

and apparatus is obtained in the outdoor substation as

shown in drawings.NOol and NO.2.The two three phase

66,000 / 6,60 0 volt ~ransformers are fed from the same or

separate transmission lines.They may also feed these trans­

mission lines if their secondaries are connected to a gen­

erator bus by means of an oil switbh.The load on one trans­

mission line may be shifted by means of the bus tie within

the station.

This design brings out the simplicity and the flexibility

of arrangement which may be obtained where the space is

not limitedoWith unlimited space fUture provisions may be

made thus avoiding changes in the structural arrangement

when the power demand increases.The only changes which

would be necessary,would be to change the position of the

transformers.Enough space is provided for such that the

change ~ould be made within a few hours upon notice given

by the consumero

This sUbstation may be used as a unit of a High Tension dis­

tributing system, such as a ring system with generating stations

and sUbstations at various points in the systam.The sUbstation 11

may be used to distribute the power from the transmission ~ine

or it ma. be used in supplying power to the transmission line

f'rom a generati:*g station.In using two banks of transformers <d"l{l

-4-

and a double circuit it of'f'ers many advantages SUChi.laS great­

er reliabi~ity of' service, easier main~enance and repairs.

It can be seen in the general wiring diagram that a bus-tie

is used,This of'f'ers several advantages in that the load on one

transmission line may be shif'ted to the other and thus should

there be any interuption in sevice due to a short circuit on

one transmission the load can be immediately switched to the

other parallel line and the truuble can be permanently repaired.

There is one way in which the designer can design a station o~

the correct capacity and then as industrial condi tl. ons change

the capacity of' the station may not be large enough to supply

the power demand,so it remains f'or him to assume some app.rent

load keeping in mind that a greater load demand might occur in

the future.

The capacity of' this particular sUbstation is 3000.00 IT.V.A.

CONDUCTOR SPACING.

S.,.a.eing between conductors and ground clearances for

Voltage of 66,000 Volts.

Non-Rigid Conductors.

(Outdoor type spans up to 900 ft.).

Minimum ground spacing 96 inches.

Recommended " " 36 " •

MiAimum spacing of conductors 52 " 0

Beeomme'!'~~d " If " 78 It •

The aboTe table is taken from Bulletin No.13.

Hickey & Schneider. Inc.

Engineers & Manufacturers.

Electrical Equipment.

Elizabeth,New Jersey.

-5-

SI ZE OF WIRE.

Canacity of each transformer bank is 1500.n K.VoA.

Thp. high sides are connected in delta and the Toltage

ratio is 66,000 / 6,600 Volts.

The line current is,

1,50n ,onnI = ---------------line 66, noo x-13

= 13.1 amperes.

Size of copper wire selected = No.1 / O.

The allowavle current carrying capacity is 125 amperes.

This is raner high but its use is suggested as pro..is-

ions must be made for future power demand.

Diameter in mils 318.

Weight is 322#./ 10 00 ft.

Breaking strain of Medina Hard Drawn wire is 4558#=.c.

The size of wire is determined by the mechanical strength that

iB i~osed upon the span.Elastic limit should be approximately

one half the ultimate strength. The wire should not be stressed

beyond its elastic limit.Max1mmm tension tp prevent excessiTe sag

is about 2000 GD 2500 pounds.

-6-

TOWERS.

Towers are to be or the A-frame type and are to be design­

ed by the stryetural engineers. The mechanical stress and

strain can be obtained rrom the calculations on Sago The

height and width can be found in the sectional drawings

Nos.3,4,5,6,7o.A factor of safety of not less than ~

shall be used as provisions must be made for a change in

the ruture.

In diagram No 1.and in drawing N03.it will be seen that ladders

are used this ma~ not be obvious but they are used since the~~~

length of disconnecting switcbJ\! are about 20 ft,long.The switch-

es are 32 ft.from the ground and it would be impossible for an

operatir to be able to open them unless these ladders were used

for this reason I find it necessary to malce some device where­

by the operator can open the 'disconnecting switches without

much trouble and time on his part.

~-

OXIDE FILM ARRESTERS.

Three phase oxide fiLm arresters are used.

Made by the General Electric Co.

Cat.Np.1576244. tt About 30% of the line voltage i£ applied

List price $4610. 03 the first insulator therfore it is

Weight 6400 #. necessary to select an insulator of the

Number of cells 536. proper electrical strength, These insulat-1h

Number of cells per stack 141. ors are good for 20,000 Volts.

Minimum Toltage 6a~OO volts-Maximum voltage 73000 volts.

Note~Choke coils should be used with oxide film arresters

except on cable systems.

The oxide finm arrester consists essentially of a number

of cells with a gap in seri~s between line and ground.The

cells are held together under slilht pressure and are ar­

ranged in sections or stacks according to the ~oltage and

kind of a circuit.The cell are disc shapel,about 7 1/2"

in diameter and 5/R" tbickpEach cell is made of two cir­

eular brass plates crimped firmly to the edges of an an­

nular ~iece of procelain.A powder, lead perox1d~,wbich has

a Tery low resistance,compaetly fillsLthe space between the

plates.The inside of the metal plates is cOTered with a

varnish film which is an insulator.The number of cells

used in an arrester is such that the Toltage per cell is

approximately 300 volts.These arresters do not need daily

charging. -s-

OIL SWITCIIES(CIRCUIT BHEAKERS).

Three phase oil circuit breakers are used.

:Made by the Westinghouse Electric & Manu:racturing Cpo

Type GA Oil Circuit breakers. OUTDOOR TYPE.

Hand-operated.

Automatic.

style No.163515.

Voltage 66000 volts.

Shipping weight 7500#.Net weight 550n#.

Gallons pf Oil 360.

Note: Weight does not include oil.Weight of' oil is appro~­

imate1y 7 1/2 pounds per gallon.

The bushing on these oil switohes are to be equiped with bush­

ing type current transformers, this will enable the oil switch

to open on some predetermined value of' the line eurrent o

-~-

Transformers.

Single phase transformers are to be used.

Made by the General Electric Co.

Canacity 500 K.V.Ao

Voltage Ratio 66000 / 6600 Volts.

Frequency 60 cycles.

Type Out door-~~~. Oil-Cooled.

weights with oil =22?OO#.

Comnlete without oil =1~nno#_

To be lifted from tank for inspection 7~OO#.

Transformers have pipe tap connections for filter press.

Caution:Lines or buses connected to these transformers

should be supported such that no appreciable weight or

mechanical stra~n is imposed on the transformers terminals.

The mransformers are connected Delta on the high side and may

be either connected in wye or delta on the low side according

to what eTBr connections are aesired.

-10-

CHOKE COILS-SUSPENSION SWITCHES & SUSPENSION INSULATORS.

The choke coils,suspellSioll disconnecting switches and sus­

pension insulators,assehlbly were selected :from I.H.J.Jovett's

design book.

Anderson disconnecting switches are used in ,combination

with the insulators of the O.B.type.

Insulator units are made by the Ohio Brass Co .dansfield, Ohio.

Six insulators are used for a line voltage of 66000 volts.

-11-

The C-B (The Ohi:) Brass Company.Hansficlcl,Ohio)

Suspension Porcclai}, Insulator,No.2!:-017,is lmown

as tbe clevis type unit.It embodies all the latest

refinements of ::lcsi:r.l1.Dir]CllSi~JllS of nctal parts

and spacili2; lJetwccl1 uHi ts al'e :lli accordance wi tIl

the st::''..l''(l.ards 3,(10 ptOCL by the :Lnsu la. tor manufacturers.

Call eastii.lgs are l;~:.lllealJle iron, center pins are for/?;-

ed steel, both ;:;alvanizedo

Coclc wordlNO 0

Racemate 25017-Type D,Fol'm 3,SUSpe!lSion

sinr;le unit ......•.•.•List per

Insulator,

100, $440.

Note :This disc can also lJC supplied with Ball and.

Socket connectio'l.

-12-

Det ..:51 s of O-E I~lsulator.

INo .of 1Len~th of ;Net ',it. cor.:- -r;;t 0 ~-;~'.,c](el1-! '-' -- - 1'- --

Units. II complete iplete lusu1 a tor' for shi1Jment. ;I: II ! ,

il Insulator.I

I

~, ; I: I

/i

1 5 3/8 9 "In i

.6 -§'f-- ----;2 : 10 3/4 18 I..J J I

i : II

3 1[) 1/8 27 36 ;I II

I4 21 -172--- 36 I 45 II

--~ ------fj1i----- --nI

26 8 4(1I

n!5I

I --oM32 1/4 --- r- 55{i 05 Ii'I-- f-~-' - -,......-_.-- I

7 3 f,;' ,j 1'0 74 !,. ':

_. ..1 : I().;1

~... .. .. .- -.. !"I~-" f14t.i ,I ~_,

Ii , I-- -~~-.. .. - -

For export shipment these insulator'units are reg-

ularly packed 12,1<1, or 10tn f" case. Other si~e cases

can be f''Lll~nishe("t whell required.

(APurox ) •

MATERIAL LIST.

Name.

Transformers

Oil Switches(three phase)

Lightning Arresters(three phase)

Choke coils

Anderson Disc.S~itch

G.B.Insulator Units

Disconnecting sticks

Wire No.1 / 0

Three bolt clamps

CleTises (Roller).

Eye Bolts. 5/8" ~ 19."

Loeke Clevis No 2937.

Quantity.

6

:l

2

6

42

:.12

2

1700 feet.

90

90

60

60

CALCULATIONS

on

TENSION

IwmmLA used.

wx1 2

p = ------ ~ wxsmax 8xs

Where

P is the maximum tension, in pounds.max

s,is the sag in reet

l,is the length or the s-pan in reet.

w,is the weight per root.

In the above formula w is the weight per unit len~th and I

-t:.have assumed the t~al weight as distributed however this

would only result in approximate resultso

-15-

Calculations on Tension.

Transmission line section.

Length of span = 86 ft.

Height of tower = ~2 ft.

WAi.ght of No. 1 /0 wire ( 86:f~.) = 2'.7 #.

" If Insulators. ( 24 ) = 220.0 #.

" fI Copper blades ( 2 ) = "lO.O #.

" " Tie wire ( 1(\ ft.) = :1.? #.

Total weight = 28fl.{) #.

Assuming a sag of ~ f'eet, the max:irnmn tension is,

:1.26x 862

P = --------- + 3.26 x 2max ox?

= 1510 #.

Where

w = :1.26 =#= / f't.

1 = 86 ft. length of span.

s = 2 :ft. sag assumed.

Calcdlations on Tension.

Section be'tween Lightning Arresters and 01.1 Switches.

Length of s-pan = 70 ft.

Height of tower = 22 :ft"

Weight of No, 1 /0 wire ( 7() :ft.) 92.5 "= =tf.

H " Choke coil. = 20.0.#.

tt " Insulators ( is \ = 165.0 J1.J ir·

" " Tie wire. ( ~? :ft.) = 7.1 ..u.iJ·

Total weight

Assuming a sag o:f 9 feet, the maximum tension is,

max 8 x 2p =

:1. ?Q X

+ ~.2q x 2.

Where

w = 3~29 # / :ft.

1 = 70 ft.length of span.

s = sag 2 :ft. assumed.

-17-

Calculations on ~ension,

Bus-Tie section.

T,ength of span = ?~.5 ft.

Height o:f tower = 16. n. ft.

Weight of No lIn wire ( 45.() ft.) = 14.6 #.

Weight of Insulators (18): = 165.0 #.

Weight o:f Copper blade (1) = 15.0 #.---------~------------------------~-----------------

Weight Toeal

Assuming a sag of 0 7 ft,jhe maximum tehsion is,

9.65 x ?9.52

P = ------------max 8 x .7

= 150rl #.

Where

w = 0.65 #/ ft.

0.65 x .7

1 = ?o.5 ft.length of span.

s =07 :ft.sag assumed.

-lR-

Calculationc- on Tension.

Transformer 'Section.

Length of span

Height of tower

= 89.5 ft.

:: 22.0 :ft.

Weight of No.1 /0 wire ( tN.5 l'to) = 28.R i.ff tI Insulators ( 18 ) = 165. 0 ·:1f.

" " Copper blade ( 1 ) = 15.0 :#:'..It " Tie wire ( 46.0 ft ) = 14.8 =H=.

Total weight = 233.6 HAssuming a §ag of ? ft.,the maxiulUID tension is,

2.5 i 80 .52

P = ----------- + 2.5 x 9

max 8 x 2

= 1250 #=.

Where

w = 2.5 #=./ f't ..

1 rt 8~.5 f't.length of' span~

s = 2 ft. sag assumed.

-19-

REFERENCE PAGE FOR DRA1YING NO.1.

Item

A-A

B-B

Name Drawing No.

Longi. tudinal.C. S. 3

Blevation.C.S. 4

Page.

?5

C-C

D-D

E-E

a

b

c

"

""

Towers

Insulators

Ladders

" "" "

" "

5

6

7

3

8,9,10.

3

?6

:'.8

:'.9-31

d

e

f'

g

h

i

j

1I

m

n

Disc.Switch.

NO.1/0 M.ll.D wire.

Lt.Arresters.

Tie line

Choke coils

Substation Bus

Oil switches

Bus-Tie

Transf'ormers.

IIi-side of' trans.

Low-side of' trans.

11

4,1~

12

5,14

6

7,15

32

32

~6,35

27

28,36

o

p

Tracks f'or transf'ormers. 7

Lif'ting tower f'or trans. 7

28

BIBLIOGRAPHY.

Electrical World Volume Pagp.

6Q 819

70 98

70 100

70 1236

71 718

70 689

72 537

72 928

72 1068

73 788

73 831

73 884

78 132f.

79 681

75 433

75 139

75., 883

75 949

75 827

75 955

74 1110

"77 1315

66 689

-21-

BIBLIOGRAPHY.

Electric Journal Volwne Page

21 193

11 158

12 157

13 420

A.IoP..F. 40 Jan- Dec.

General EIActric Review 17 397

17 639

17 728

19 44

19 973

21 640

23 342

24 41

")(''!!Jllrreder~

~~<::

~~~

;r-~'

~~r-+-. ~

:r--Coil.

""'" ~DOD a0 0 L!!JlJt

. Cfoke

T~•

~'------ ~ ----~

- ~~ ---~-~ -~-....

.. ...,~ .~

~,

-1 J.~~ \f)

~ .~~-1 1 ~\jQ

~ I ~

~ :~ ~ ~.~~lf)

~.0 .....

-1.....,. ~ \)

~~ ".~ ~

1co

"'"f-~

IfC'i~'

.t-C\~

~ ~~~

~(';0.....

~Q

~~

f~~ ~~ ~ -'- \:)

~~ - ~, (J)!\

tl'\f!r\-

I--.f-<:l.>..

-27-

-25- .

Ckl..

t\l\ I

~'•

/YO 8

C-B Sl1SrHJJlsi.on P 1'cc1n1n Insulator.

Type J),Form '. -Patented

___.l::::;::==-====:::::;;::l:-:::£---'_

Two units,No o 25017,connectcd;lower unit

shown in section.

/YO. q

Suspension Irsula tor ~~o, :::::'017, 't'ype n, F(~r!.1 '1.

(YO. /0.

Deaf} End wi.th Tur,l Buckle for' Gf1,800 Volt Sul}-

st:l.tJon.

Dead. Bnd on Steel Gil'ller.g~<fc: Bolt userl on d.eai.1. end. •

..

1. Servii.1C.

2.Three Bolt Clamp A.To&

:~ "noller Clevis.

."

jl',;

T • Pl:.... t tern ..

~.Suspension Disc .. o.n.No.2~OI7g

6 .. 5/f?" xIS" Rye Dolt, threa(led lfl", & h<,.. s 2 nuts & 1 washer.

IVa / I.~)llspension Disconi.ec. tinn' Swltch For ()6, ono Volt

Substation.

1.See Drawing NO p 8 't ,.

2.Serving.

3.Iloller UleTis.

4.Suspension Disc,O.B.No.2~017.

~.Anderson Suspension Disconncctill~ Switch.

6.Three Bolt Cla~p A.T.&T.Pattern.

1Yl7.IZSuspension Choke Cu:U For Ci(;, "',:.r) Volt

Sul)statinn.

\,\

\

11.Suspension Choke Coil.

2.Serving.

~. Punchecl Trlhe Terrdnal f'or lin Wire.

40 Threo Bolt ClaMp ,AoT 0 8~ T .r;:.. t tern

5.Roller Cleviso

NO./-f:Wcstiu.:-hons0 ~'~'~ctl':'ic & E;1mLf':,-ctnr:i..nrr Co.

East T'itts1nH':~11,Pao

Type GA Oil Circuit-Breaker.

style No.163515oVolts RoOOO.

Net wt.55,)';:'!: vithout o:il.Gals 0;1 :l!~f).

~~ f~

'::

~

.,..~~

, ..

•ll)

,I

\)...I I

I

GI I;

~

I

~

""

-36-

INDEX.

Arresters

Bibliography

Breakers, circuit

Bus tie

Circuit breakers

Choke colitIs

Conductors size

Conductors s~acing

Contents table

Disconnecting switches

Drawing general diagram

Drawings

EQuipment

Film arresters

Formula tension

General diagram

HifP tension equipment

Introduction

Insulators

Length of' spans

Material list

Oil Switches

Page.

8,'.:>5,'14

?ol,o')

~7

q,26,~5

11,~3

6

5

1

11, ~:.}2

5>.3

?8-36

7-1;l

8,25,:14

15

7-1:1

2- 4

12, 1~, ?-9_-:n

16-19

14

Q,~6t:l5

Index.

Oxide rilm arresters

Page rererence

Porcelain insulators

Rererence page

Ratio Toltage

Sag

Size of wire

Snacing

Substation procedure

Susuension choke coils

Susuension insulators

Suspension disconnecting switches

Switches oil

Table 01' con*ents

Tie bus

Tension calculations

Towers

Transformers

Voltage ratio

Wire size

-38-

Page.

8,?5,:l4

20

1 2 , 13~ 2q-~1

?()

6,1()

16-1G

6

5

2

11,33

1 2 ,13,29-31

11,32

°,26,35

1

27

16-19

7,24

10,28,36

6,10

6

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