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mile section is about 64 f�t, with��ck Iocated near the
<br />center. Accordingly, a very restricted space remained
<br />for locating the 230-Kv transmission line structures.
<br />The first choice of structures was narrow base [12-ft
<br />wide] lattice-type steel towers which had been used
<br />throu�hout thc Public Service transmission system.
<br />Hozvever, after preliminary checks of the route were
<br />made, it was rcalized that many other factors needed
<br />to be considered.
<br />First, the railroad required a minimum clearance of
<br />16 ft from centcrlinc of track to face of steel for
<br />operating future mechanized equipmeni. Thc 12-ft wide,
<br />narro���-base towcrs initially considered could not meet
<br />this rcyuiremcnt at many sites. Further, the close
<br />proximity of rrsicicntial housing along the right-of-way
<br />to the prpposrd transmission structrares favored the
<br />selection of the aesthically plcasing tapered steel poles
<br />as a logical solution.
<br />There are 64 self-supportirig poles on the line [see
<br />ciata on adjacent pagc]. All suspension poles were de-
<br />signe�l to sustain an}� t��•o broken ivires at 7,500 lb each
<br />[holding po�v�:r af suspcnsion clamp plus 50% impact]
<br />at 8-lb-per-sc�-ft wind pressure on �/�-in radial-iced wire
<br />at f.li� (with z 5-dcg angle in line]. All tension poles
<br />���cr� cicsigncJ to sustain all �vires broken at one side at
<br />hca�}� load;n�" c�r .ill wires intact with 1�/z-in. radial
<br />ice, no winci �ressure a[ OF [with a full angle in the
<br />linc).
<br />Poles are of 60,000-psi-yield-strength steel
<br />'I�hc heavie,t pol� �vcighs 25 tons; thc highest pole is
<br />+ 1-17 ft. 7�hey arc 1'_-sidcd, tapered, with curved, upswept
<br />k arn�s, fabricated c�f LS Steel's Ex-Ten steel, having a
<br />}�icld strcn�th o[ 60,(100 psi. The poles were dcsigned
<br />and furnished h}� i��icyer Machine Co of Red Wing,
<br />titinn. Lach polc is composcd of two sections �vith a
<br />tcicscopin� join[.
<br />Thc top sections arc a Tixcd 60 ft in Icngth; thc
<br />bottom sections vary accordin� to the hei�ht of the pole.
<br />'I'hc ttico sections were fiucd at the shop, marked for
<br />ficld alibnmcnt an� overlap, �ind then knockcd down for
<br />railroad s}iipment.
<br />I=u11-lo.ici iielcl tcsts wcr� conducted on t«•o of tlic
<br />� pc�lcs in thc horizontal position at thc fabricatur's yard.
<br />� "[�he polcs, c�ne a 5-de�� suspension pole and the other
<br />� a 30-cle� tcnsion �ole, �r�ere tcsted to yield strength
<br />' �E�ithout ci�struction and latcr uscd in the line. The test
<br />' c3ata dcmonstrated that the poles fully met strength
<br />" rcquiremcnts; ho�c��c��cr, defl�ctions at full load were
<br />�lightly grcuter than anticipated.
<br />Under actual operating condition; [60F �vith no
<br />windJ, it is prcfcrrcd ihat all polcs stand plumb to
<br />achievc �ood looks. Therefore, four-anglc-poles were
<br />factory-camberc� along transverse-axcs. 'Th� rcmainder
<br />of tl�� poles were raked away from the line approxi-
<br />matcl�- 9 in. (at poIe top) to compensste for the installed
<br />wcight of conductor and hardware.
<br />Pole secti�ns sealed to minimize oxidation
<br />Sincc tlie internal corrosion of a freely ventilated
<br />stc:,l pole is something over which on� has no control
<br />once tf�e pole is erccted, the fabricator made a study of
<br />�i 100-ft steel [8,500 lb] pole with both ends sealed.
<br />Thc total weight of inetal consumed by the trapped
<br />oxy�en inside the pal� [at 100% oxidation] was calcu-
<br />68
<br />{ij: _ .
<br />Pilot hole for multi-section foundation casing is bored
<br />v�rith 6•ft dia auge�
<br />�, ;�
<br />Pole sections were fitted at shop, marked for field
<br />alignment and k�ocked down for shipment
<br />Field-joining of the two pole sections was achieved
<br />with a speciallydesigned jacking device
<br />Electrical Wor1d, Jurte 26, 1967
<br />- 4
<br />� '
<br />spra5�-cbats .of
<br />` Design dataM ��`for. 230-kY shade of gray �
<br />Grentoch Branch steel- ol I' sBG , �.0%0.4
<br />1 1
<br />_ 4
<br />tower=gray paiut were; u
<br />11 •t
<br />The -
<br />fl N� ,
<br />p e me . � �- ---..�,� on : �,.
<br />sunn�.or`�c�udy days: - �.
<br />❑ Conductors-1,590 MCM, ACSR, 54/19, ultimate ,r`'�-y""`�ach pole section is held together by welds. To make
<br />strength 55,000 !b; F' . sure :no faulty weld would be discovered later in the .
<br />❑ Ground wire-7 No. 5 Alumoweld, ultimate strength field, a testing lab�ratory was employecl to perfornl a '
<br />27,030 Ib, 30-deg shield angle, grounded:at each noridestz'tlCtiVe Shop iIlspeCtioil. 1Vlany-defective weids;
<br />structure and jumpered at dead-ends; `' � v�rere discovered,�ar�d or.Cected. �•�'.
<br />❑ Ins�lators-16 in suspension, 18 for dead-ends;
<br />❑ Damper�-1 Stockbridge-type for each conductor in' j�0�9P SUb-soi! conditions er�countered_= -�- �"�� �
<br />all spans; . , ,
<br />❑ Ruling span-500 ft; ' Soil lioriags were taken at each pole site. '.�hey indi-
<br />❑ �oadin9—most criticat of the fo��ow�n9: cated poor soil con�litions ai most of the sites, varying
<br />a] Bare wires at 60F, 2o Ib per sq tt wind �o� 10 to 20 ft of gray, clayey silt underlaid by a
<br />ressure on wires ard poles;
<br />b] 1/Z-in. radial iced wire at OF, 8 Ib per sq tt stratus of green marl at the nozth end of the line, to
<br />wind pressure on iced wire and pole; black, silty sand with a trace of gravel at the Blackwood
<br />c] l i/2-in. radiai iced wire at OF with no wind on section. The nominal underground water level in the
<br />wire or structure; area is about 15 ft belo.w grade, but at Beaver �rook
<br />❑ Clearances
<br />a] Vertical clistance from top of rail to low point of and Pi'neS Run Swamps, the water is close to the surface.
<br />sag of lowest conductor�40.5 ft at 120F; Because of the loR� bearing value of soils and limited
<br />b] Minimum horizontal distance: space between track and edge of right-of-way, spread
<br />1] irom centerline of track to face of steel, footings would have been difficult and expensive to
<br />16 it; build; therefore, the round-sha�ft foundation design was
<br />2] between coducfiors in swing position and determined to �e the most �conomical solution.
<br />nearby 26-kv line, 16 ft;
<br />3] from centerline of conductors in static Six- and seven-ft diameter shafts were speciiied for
<br />position to edge of right-of-way, 20.� ft most of the poles, with nine-ft diameter sLafts for the
<br />[except where the conductor line heaviest ones. With the anchor-bolt circle varying
<br />parallels an adjacent �ledicated roadway]; between 3z/a and 51/2 ft, the diaxneter of shaft is about
<br />❑ Right-of-way clearing—right-of-4vay is cleared only the minimum size to accomz�5date the an�hor-bolt
<br />for a total width of 40 ft, consisting of 20 ft on each
<br />side �f the condu�tor centerl;ne. In addition, brush and a5sembly.
<br />other low-growing trees are allowec! to remain if there The bending moment at tke bases of most of the ]ioles
<br />is at least 20-ft clearance under the lowest conductor is about 2,000,000 ft-lb, and the heaviest one i5
<br />as indicated by the plan and profile; 7,050,000 ft-Ib. The soil passive-resi'stance assumea
<br />❑ Pole footing res?stance—maximum 10 ohms.
<br />"�TDesign conditions exceed Grade B NESC heavy loading
<br />requirements
<br />lated to t� 8.61b, or 1/10% of the original garent metal
<br />which is considered negligible. Therefore, it was speci-
<br />fied thai� all �omponents of the poles—top sections,
<br />bottom sections and arms—be sealed at both ends.
<br />In anticipati�on of winter construction, epoxy paint,
<br />vanes from 200 to SOO lb per sq ft of depth [so�l passive-
<br />resistance is utilized to stabilize the fo�.indation], Using
<br />these criteria, the �average depth of shaft is about 25 ft,
<br />with the deepest one 36 ft.
<br />Pole gr�und-lina-defl�ction field tesis conducted
<br />To obtain correlation between passiv�-resistance of a
<br />specific type of soil, having a known bearing value, and
<br />ground-�ine deflections of a cantilever pole with over-
<br />turning loads, field tests were made at two pole sites—
<br />one site with bad, clayey-silt sub-soil, and the ather of
<br />as recommended by the supplier, ��as rejected because clayey sand. Two, 12-in. dia [26 ft'long] standard steel � �I
<br />curing becomes critical below 50F. Iustead, one shop pipes filled with concrete were driven 15 ft into the
<br />spray-coat of rust inhibiting brown primer and two field ground. Loads were applied to the poles 10 ft above . ;: I
<br />Pole data fior 2�0-kv Grenloch Branch steel-pole tr�n�mission iine �
<br />i:
<br />Angle fdeg] 0 to 5 5 to 30 30 to 60 ' FO to 90 j'
<br />Number of poles [64] 44 17 1 2
<br />Construction taper 12 sides round 12 s'sdes round 12 sides elliptical ' 12 sides elliptical �
<br />11/a in./10 ft 2 En./10 ft 2.5 ft/10 ft. 3.0 in./10 ft
<br />Arm len�'th fftj 131h 12 . 12" ;' 12
<br />..:
<br />Verticai d�stance fftl ,
<br />between'ground wsre -
<br />and xop conductar : 11 15 15 _ 15
<br />between conductors 19 ' 19 19 19 i;
<br />Overall height [ft] 108�� to 146�/a 1041/a te 1301/a 106. � 118 to 128 �.
<br />Bo�ttom dia [in.] 321/z to 391/s 383/a to 435/a 453/s , '54 and 57 ,
<br />Top dia [in.] 141h ; 181/2 • 20 ; .'� :20 : ; �'. -
<br />Weight [Ib] 21,70� to 32,000. . 28;200 to 38.000 :33,28�. 5I.300 to a2�640
<br />, , , . .
<br />Foundation [ft].- ' : 6-7,dia x 16-33 deep �7_ �ia x 16-33 deep ,7 dia x:30 deep ' 9 dia x'35;deep ' a.
<br />Foundation bolts :._ <' 16 2�d-�n. x-12 � ft` 20 21�2 in. x 14 ft '. '24 21/z in. x 12:6 ft'32 2�/i in: x.14�ie`ft. ;. .
<br />- ` r
<br />. � � - �.• r�„
<br />� S t vR
<br />E�ect�ical�lNor[d;�June 26, 1967 , �,,
<br />.� � i..,t � e
<br />d' ... 34,� i .'4, �r��' "r
<br />- . . . . �. . ' . . _ _ . � _ . ... ._ . , . . . , . . .. . , .. . _ .: a�.�'Y��.��s+` -. . �rnv'`zKh.. ���
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