TC151ClearancesofWires,Conductors,Cables,andEquipmentfrom ......communication conductorsand cables;messengers; overheadshield/ surge-protection wires;effectively groundedguys; ungroundedpor-tionsofguysmeet-ingRules215C4,

Transmission Construction Standard

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PublishedDate: 18Apr 17

Last Reviewed: 18Apr 17

Deviation from this standard requires prior approval. Contact the standards engineering manager for approval processes and forms.Printed versions of this standard may be out of date. Please consult the online standards for the most recent version. This standard shall be used and duplicated only in support ofPacifiCorp projects. ©2017 by PacifiCorp.

TC 151 Clearances of Wires, Conductors, Cables, and Equipment from

Buildings, Bridges, and Other InstallationsE n g in e e r :A.S h k u r a tk o vAp p r o v e r :R a c h e lle Ha n n o n1 8 Ap r 1 71 8 Ap r1 7

Disclaimers

Disclaimer for RockyMountain Power and Pacific Power employees: this standard provides a reference to theNational Electric Safety Code and has been expanded to cover common voltages used by RockyMountainPower and Pacific Power. As an estimator or designer you are responsible for verifying that this standard is cur-rent and that additional clearance requirements including but not limited to elevation adders, state and localrules or regulations are applied appropriately or in concert with this standard.

Disclaimer for Contractors: this standard is developed for internal company use only and is provided as a ref-erence document. Contractors are responsible for understanding and adhering to all federal, state and localrules and regulations which may supersede this standard.

Purpose

This standard providesminimum clearances of wires, conductors, cables and equipment from buildings,bridges, swimming pools, and other installations as required by the National Electrical Safety Code (NESC)Rule 234. These minimum clearancesmust be maintained on all lines operated by RockyMountain Power andPacific Power in the states of Utah, Wyoming, Idaho, Oregon, andWashington. These clearances do not applyin the state of California where General Order No. 95 is the governing regulation.

Scope

This standard contains extrapolated tables for company use from Rule 234 of the 2017 edition of theNESC. This standard also contains tables that were not provided by the code, but were derived from applic-able sections of the NESCRule 234 (2017). Since the NESC (2017) provides clearance values for voltagesup to 22 kV or 50 kV line to ground, highlighted sections of the tables were developed to include clearance val-ues for higher voltages used by the company. These values incorporate elevation adder and/or voltageadder for all applicable line voltages and were calculated based on the NESCRule 234G1 and 234G2(2017).

NOTE 1: text in this font, that follows "NESCRule" headings in this document is taken directly from NESCC2-2017 (National Electrical Safety Code® (NESC®) (Accredited Standards Committee C2-2017). All rightsreserved. Figure titles, table headings, and footnotes indicate figure or table content that has been taken dir-ectly from NESCC2-2017.

NOTE 2: it is the user’s responsibility to ensure that the calculated clearances are compliant with the most cur-rent edition of the NESC.

Additional Clearances

1.Construction Tolerance – line construction hasmany aspects that have inherent variability, whichinclude but are not limited to mapping inaccuracies, structure setting depth variations, and conductor sagvariations. For transmission line construction it is strongly recommended that a construction tolerance ofthree (3) feet be added to the clearances listed in this standard to ensure that the NESCminimum clear-ances are met under the worst loading conditions.

2. Elevation Adder – for voltages exceeding 50 kV line to ground and at elevations exceeding 3300 feetabove sea level, the additional clearance calculated from the NESCRule 234G1 (2017) must beincreased by 3% for each 1000 feet in excess of 3300 feet above mean sea level. The tables in this stand-ard list calculated values for elevations up to 12300 feet in increments of 3000 feet.

3. Local Governance – some state, city, or county authorities may require greater minimum clearances thanthe NESCminimum clearances within their jurisdiction. It is the responsibility of the user to ensure com-pliance with all pertinent ordinances for overhead line construction in the local area.

NESC Rule 234A (2017)

A. Application

In each of Rules 234B, 234C, and 234D, horizontal clearance requirements are specified for two conditions: (1) the con-ductor without wind displacement (at rest), and (2) the conductor with wind displacement. In each case, the clearancerequirements for both conditions shall be satisfied.

1. Vertical and horizontal clearances (no wind displacement)

The vertical and horizontal clearances specified in Rules 234B, 234C, 234D, 234E, 234F, and 234I apply underwhichever conditions of the following conductor temperature and loading conditions produces the closest approach.Rules 234A1a, 234A1b, and 234A1c apply above and alongside subject installations; Rule 234A1d applies below andalongside subject installations.

a. 50 °C (120 °F), no wind displacement, final sag.b. The maximum conductor temperature for which the line is designed to operate, if greater than 50 °C (120 °F),no wind displacement, final sag.

c. 0 °C (32 °F), no wind displacement, final sag, with radial thickness of ice, if any, specified in NESC Table230-1 for the zone concerned.

d. The minimum conductor temperature for which the line is designed, no wind displacement, initial sag.

EXCEPTION: Vertical or lateral conductors or cables attached directly to the surface of a supporting structurein accordance with other rules are not subject to the provisions of this rule.

NOTE: The phase and neutral conductors of a supply line are normally considered separately when determiningthe sag of each due to temperature rise.


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TC 151 Clearances ofWires, Conductors, Cables, and Equipment from Buildings, Bridges, and Other Installations

2. Horizontal clearances (with wind displacement)

Where consideration of horizontal displacement under wind conditions is required, the wires, conductors, or cablesshall be considered to be displaced from rest toward the installation by a 290 Pa (6 lb./ft.2) wind at final sag at 15 °C(60 °F). The displacement of a wire, conductor or cable shall include deflection of suspension insulators. The dis-placement of a wire, conductor, or cable shall also include deflection of a flexible structure if the highest wire, con-ductor, or cable attachment is 18 m. (60 ft.) or more above grade.

EXCEPTION: Where the entire span is so close to a building, terrain feature, or other obstacle as to be shelteredfrom the wind flowing across the line in either direction, the wind pressure may be reduced to a 190 Pa (4 lb./ft.2)wind. Trees are not considered to shelter a line.

3. Transition between horizontal and vertical clearances

The horizontal clearance governs above the level of the roof or top of an installation to the point where the diagonalequals the vertical clearance requirement. Similarly, the horizontal clearance governs above or below projections frombuildings, signs, or other installations to the point where the diagonal equals the vertical clearance requirement. Fromthis point the transitional clearance shall equal the vertical clearance as shown in Figures 234-1(a) and 234-1(b). Thisrule should not be interpreted as restricting the installation of a trolley-contact conductor over the approximate centerline of the track it serves.

EXCEPTION: When the horizontal clearance is greater than the vertical clearance, the vertical clearance governs bey-ond the roof or top of an installation, or projections from an installation, to the point where the diagonal equals the hori-zontal clearance requirement, as shown in Figure 234-1(c).

Figure 1—Clearance Diagram for Buildings and Other Structures


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Figure 2—Transitional Clearance when H is Greater than V

NESC Rule 234B (2017) Clearances of Wires, Conductors, and Cables fromOther

Supporting Structures

Wires, conductors, or cables of one line passing near a lighting support, traffic signal support, a supportingstructure of a second line, or intermediate poles in skip-span construction, without being attached thereto, shallhave clearance from any part of such structure not less than the following:

Horizontal Clearances

Table 1—Horizontal Clearance of Conductors fromOther Supporting Structures NOWIND‡Note: Table cell revisionsare in the company's green table revision style and also italicized to help them stand out.

Conductor or cableHorizontal clearance required without wind (ft.)

Elevation:Sea level to 3300 ft.

Elevation:3301 to 6300 ft.



Up to 22 kVphase-to-ground (ft.)† 5.0 5.0 5.0 5.0

22 kV to 70 kVphase-to-ground115 kVphase-to-phase (ft.)

6.6 6.8 6.9 7.1


7.1 7.3 7.5 7.7


7.6 7.9 8.1 8.4


9.0 9.4 9.8 10.1


11.3 11.9 12.5 13.1


14.9 15.8 16.7 17.6

† EXCEPTION: For effectively grounded guys and messengers, insulated communication conductors and cables, neutralsmeeting Rule 230E1, and cables of 300 V or less to ground meeting the requirements of Rule 230C1, 230C2, or 230C3, thehorizontal clearance may be reduced to 900 mm (3 ft.).


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‡ The NESC (2017) does not provide a table for horizontal clearances (without wind) of wires, conductors, or cables fromother supporting structures. The base value of 5.0 ft. was obtained from the NESC Rule 234B1a (2017), and the voltageand elevation adders were calculated from the NESC Rule 234G1 and 234G2 (2017). The calculated values were roundedup to the nearest tenth of a foot.

Table 2—Horizontal Clearance of Conductors fromOther Supporting Structures WITH

WIND§

Note: Table cell revisionsare in the company's green table revision style and also italicized to help them stand out.

Conductor or cable

Horizontal clearance required when displaced by wind

(m.) (ft.)Elevation:

3301 to 6300 ft.Elevation:


9301 to 12300 ft.

(ft.) (ft.) (ft.)

Open supply conductors, 0 to 750 V① 1.1 3.5 3.5 3.5 3.5

230C2 cable, above 750 V 1.1 3.5 3.5 3.5 3.5

230C3 cable, above 750 V 1.1 3.5 3.5 3.5 3.5

Open supply conductors,over 750 V to 22 kV

1.4 4.5 4.5 4.5 4.5


-- 4.7 4.7 4.7 4.7


-- 5.2 5.2 5.2 5.2


-- 6.1 6.3 6.4 6.6

70 kV to 84 kVphase-to-ground138 kVphase-to-phase

-- 6.6 6.8 7.0 7.2


-- 7.1 7.4 7.6 7.9


-- 8.5 8.9 9.3 9.6


-- 10.8 11.4 12.0 12.6


-- 14.4 15.3 16.2 17.1

① Does not include neutral conductors meeting Rule 230E1.

§ The non-highlighted portion of the table was copied from the NESC Rule 234B1b (2017), courtesy of IEEE, (National Elec-trical Safety Code® (NESC®) (Accredited Standards Committee C2-2017). All rights reserved. The highlighted portion wasadded to account for voltage and/or elevation adders for applicable voltages. These adders were calculated based on theNESC Rule 234G1 and 234G2 (2017).


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Vertical Clearances

Table 3—Vertical Clearance of Conductors fromOther Supporting Structures‡Note: Table cell revisionsare in the company's green table revision style and also italicized to help them stand out.

Conductor or cableVertical clearance required (ft.)

Elevation:Sea level to 3300 ft.




Up to 22 kVphase-to-ground (ft.)† 4.5 4.5 4.5 4.5

22 kV to 50 kVphase-to-ground46/69 kVphase-to-phase (ft.)†

5.5 5.5 5.5 5.5


6.1 6.3 6.4 6.6


6.6 6.8 7.0 7.2


7.1 7.4 7.6 7.9


8.5 8.9 9.3 9.6


10.8 11.4 12.0 12.6


14.4 15.3 16.2 17.1

† EXCEPTIONS 1 and 2 shall not be applied cumulatively.EXCEPTION 1: For effectively grounded guys and messengers, insulated communication conductors and cables, andneutrals meeting Rule 230E1 and for cables of 300 V or less to ground meeting the requirements of Rule 230C1, 230C2,or 230C3, the vertical clearance may be reduced to 600 mm (2 ft.).

EXCEPTION 2: The vertical clearances may be reduced by 600 mm (2 ft.) if both of the following conditions are met:

i. The wires, conductors, or cables above and the supporting structure of another line below are operated and main-tained by the same utility

ii. Employees do not work above the top of the supporting structure unless:1. The upper circuit is de-energized and grounded per Rule 444D or temporarily insulated or repositioned, or2. Other equivalent measures are taken.

NOTE: Clearances of wires, conductors, and cables from adjacent line structure guy wires are given in Rule 233.

‡ The NESC (2017) does not provide a table for vertical clearances of wires, conductors, or cables from other supportingstructures. The base value of 4.5 ft. was obtained from the NESC Rule 234B2 (2017), and the voltage and elevation adderswere calculated from the NESC Rule 234G1 and 234G2 (2017). The calculated values were rounded up to the nearesttenth of a foot.


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NESC Rule 234C (2017)

Clearances of wires, conductors, cables, and rigid live parts from buildings, signs, billboards, chimneys, radio and tele-vision antennas, tanks, flagpoles and flags, banners, and other installations except bridges

1. Vertical and horizontal clearancesa. ClearancesUnguarded or accessible wires, conductors, cables, or rigid live parts may be located adjacent to buildings, signs,billboards, chimneys, radio and television antennas, tanks, flagpoles and flags, banners, and other installations andany projections therefrom. The vertical and horizontal clearances of such rigid and nonrigid parts shall be not lessthan the values given in Table 234-1 [Table 5 in this document] when at rest under the conditions specified inRule 234A1. These facilities may be installed beside, over or under buildings, building projections and otherinstallations, as illustrated in Figures 234-1(a), 234-1(b), and 234-1(c).

b. Horizontal clearances under wind displacement conditionsWhen the following conductors and cables are displaced from rest under the wind conditions identified in Rule234A2, horizontal clearances from such conductors or cables to buildings, signs, billboards, chimneys, radio andtelevision antennas, flagpoles and flags, banners, and other installations shall be not less than those shown below:


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Table 4—Horizontal Clearances WITHWIND of Wires, Conductors, Cables, and Rigid Live

Parts from Buildings, Signs, Billboards, Chimneys, Radio and Television Antennas, Tanks,

Flagpoles and Flags, Banners, and Other Installations Except Bridges†Note: Table cell revisionsare in the company's green table revision style and also italicized to help them stand out.

Conductor or cable


(m.) (ft.)Elevation:



9301 to 12300 ft.

(ft.) (ft.) (ft.)


230C2 cable, above 750 V 1.1 3.5 3.5 3.5 3.5

230C3 cable, above 750 V 1.1 3.5 3.5 3.5 3.5

Open supply conductors, over750 V to 22 kV

1.4 4.5 4.5 4.5 4.5


-- 4.7 4.7 4.7 4.7


-- 5.2 5.2 5.2 5.2


-- 6.1 6.3 6.4 6.6


-- 6.6 6.8 7.0 7.2


-- 7.1 7.4 7.6 7.9


-- 8.5 8.9 9.3 9.6


-- 10.8 11.4 12.0 12.6


-- 14.4 15.3 16.2 17.1


See Footnotes 9 and 10 to Table 234-1 [Table 5 in this document].

† The non-highlighted portion of the table was copied from the NESC Rule 234C1b, courtesy of IEEE, (National ElectricalSafety Code® (NESC®) (Accredited Standards Committee C2-2017). All rights reserved. The highlighted portion wasadded to account for voltage and/or elevation adders for applicable voltages. These adders were calculated based on theNESC Rule 234G1 and 234G2 (2017).


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2.Guarding of supply conductors and rigid live parts

Where the clearances set forth in Table 234-1 [Table 5 in this document] cannot be obtained, supply conductors andrigid live parts shall be guarded. Supply cables meeting Rule 230C1a are considered to be guarded within the meaningof this rule.

3. Supply conductors attached to buildings or other installations

Where the permanent attachment of supply conductors of any class to a building or other installation is necessary foran entrance, such conductors shall meet the following requirements over or along the installation to which the con-ductors are attached:

a. Energized service drop conductors, including splices and taps, shall be insulated or covered in accordance withthe following:(1) For 0 to 750V, Rule 230C or 230D(2) For over 750 V, Rule 230C1

This rule does not apply to neutral conductors meeting Rule 230E1.

b. Conductors of more than 300 V to ground shall not be carried along or near the surface of the installationunless they are guarded or made inaccessible.

c. Wires or cables attached to and run along side the installation shall have clearances from the surface of theinstallation not less than 75 mm (3 in.).

EXCEPTION: For open supply circuits of 0 to 750 V and supply cables of all voltages meeting Rule 230C1,230C2, or 230C3, the clearance at the attachment points may be reduced to 25 mm (1 in.). No clearance from theserved structure is specified for such conductors anywhere else in the span where they are physically restrained bya suitable bracket from abrasion against the served structure.

d. Service-drop conductors, including drip loops shall have a clearance of not less than the following:(1) 3.0 m. (10 ft.) vertical clearance from the highest point of readily accessible roofs, balconies, attacheddecks, fire escapes, or other attached structures over which they pass or to which they are attached.

EXCEPTION 1: For clearances above railings, walls, or parapets around balconies, decks, or roofs, use theclearances required for row 1b(1),Table 234-1 [Table 5 in this document]. For such clearances where an out-side stairway exists to provide access to such balconies, decks, or roofs, use the clearances required for row 2b(2), Table 234-1.


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EXCEPTION 2: Where the voltage between conductors meeting Rule 230D does not exceed 300 V, or where thevoltage of cables meeting Rule 230C2 or 230C3 does not exceed 750 V, or where the cable meets Rule 230C1,and the roof or balcony is not readily accessible, the clearance over the roof or balcony, including the drip loopshall be not less than either of the following:

(a) 900 mm. (3 ft.)(b) 457 mm. (18 in.) for a horizontal distance of 1.8 m. (6 ft.) from an approved raceway or supportlocated not more than 1.2 m. (4 ft.) from the edge of the roof and not less than 900 mm (3 ft.) forthe remainder of the horizontal distance that the cable or conductor passes over the roof or balcony.

A roof, balcony, or similar structure is considered readily accessible to pedestrians if it can be cas-ually accessed through a doorway, window, ramp, stairway, or permanently mounted ladder by aperson, on foot, who neither exerts extraordinary physical effort nor employs tools or devices togain entry. A permanently mounted ladder is not considered a means of access if its bottom rungis 2.45 m. (8 ft.) or more from the ground or other permanently installed accessible surface, or isotherwise equipped with barriers to inhibit climbing by unauthorized persons.

NOTE 1: See Figure 234-2.

NOTE 2: See Table 234-6.

(2) Not less than 900 mm (3 ft) in any direction from windows.

EXCEPTION 1: This does not apply to service-drop conductors meeting Rule 230C3 above the top level ofa window.

EXCEPTION 2: This does not apply to windows that are not designed to open.

(3) Not less than 1.5 m (5 ft) horizontally from porches, decks, fire escapes, or other similarly attached struc-tures.

(4) Not less than 900 mm (3 ft) vertical clearance below porches, decks, fire escapes, or similarly attachedstructures.

NOTE: See Rule 232 for clearances above ground.

4. Communication conductors attached to buildings or other installations.

Communication conductors and cables may be attached directly to buildings or other installations.

5. Ladder space

Where buildings or other installations exceed three stories [or 15 m. (50 ft.)] in height, overhead lines should bearranged where practical so that a clear space or zone at least 1.8 m. (6 ft.) wide will be left either adjacent to thebuilding or beginning not over 2.45 m. (8 ft.) from the building to facilitate the raising of ladders where necessary forfire fighting.

EXCEPTION: This requirement does not apply where it is the unvarying rule of the local fire departments toexclude the use of ladders in alleys or other restricted places that are generally occupied by supply conductors andcables.


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NESC Rule 234G (2017)

Additional clearances for voltages exceeding 22 kV for wires, conductors, cables, and unguarded rigid live parts ofequipment.

Greater clearances than specified in Rules 234B, 234C, 234D, 234E, 234F, and 234J shall be provided where requiredas follows:

1. For voltages between 22 and 470 kV, the clearance specified in Rules 234B, 234C, 234D, 234E, 234F, and 234Jshall be increased at the rate of 10 mm (0.4 in.) per kV in excess of 22 kV. For voltages exceeding 470 kV, theclearance shall be determined by the method given in Rule 234H. All clearances for lines over 50 kV shall bebased on the maximum operating voltage.

EXCEPTION: For voltages exceeding 98 kV ac to ground or 139 kV dc to ground, clearances less than thoserequired above are permitted for systems with known maximum switching-surge factor. (See Rule 234H).

2. For voltages exceeding 50 kV, the additional clearance specified in Rule 234G1 shall be increased 3% for each 300m. (1000 ft.) in excess of 1000 m. (3300 ft.) above mean sea level.

3. For voltages exceeding 98 kV ac to ground, either the clearances shall be increased or the electric field, or theeffects thereof, shall be reduced by other means, as required, to limit the steady-state current due to electrostaticeffects to 5 mA, rms, if an ungrounded metal fence, building, sign, billboard, chimney, radio or television antenna,tank or other installation, or any ungrounded metal attachments thereto, were short-circuited to ground. For thisdetermination, the conductor shall be at a final unloaded sag at 50 °C (120 °F).


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Examples (not from the NESC)

Example 1 Line voltage line-to-line: 12.47 kVLine voltage line-to-ground: 7.2 kVElevation: 4500 feetAdjacent installation: deckGoverning clearance: verticalRule 234G1: N/A. Voltage is less than 22 kV to ground.Rule 234G2: N/A. Elevation exceeds 3300 feet, but voltage is less than 50 kV to ground.Reference expanded Table 5 (Expanded NESC Table 234-1): • Column for open supply conductors between 750 V and 22 kV.• Row for vertical clearance over or under balconies, porches, decks, and roofs readily access-ible to pedestriansMinimum required clearance 13.5 ft.

Example 2: Line voltage line-to-line: 138 kV

Line voltage line-to-ground:

Elevation: 9300 feetAdjacent installation: roof, not readily accessible to pedestriansGoverning clearance: verticalRule 234G1: Applies. Voltage exceeds 22 kV to ground.Rule 234G2: Applies. Elevation exceeds 3300 feet, and voltage exceeds 50 kV to ground.Base value: 12.5 feet (Table 5 - Expanded NESC Table 234-1)

Minimum required clearance


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TC 151Clearances ofWires, Conductors, Cables, and Equipment from Buildings, Bridges, and Other Installations1 8 Ap r 1 7

1 8 Ap r 1 7

Table 5—(Expanded NESC Table 234-1) Clearance of wires, conductors, cables, and unguarded rigid live parts adjacent but not attached to buildings

and other installations except bridges(Voltages are phase-to-ground for effectively grounded circuits and those other circuits where all ground faults are cleared by promptly de-energizing the faulted section, both initially and following subsequent breaker operations. See the defin-

itions section for voltages of other systems.Clearances are with NOWINDdisplacement except where stated in the footnotes below. See Rules 234A, 234C1a, 234C2, and 234H4.) Table revisions are in green and italicized.

Insulatedcommunicationconductors and

cables; messengers;overhead shield/surge-protectionwires; effectivelygrounded guys;ungrounded por-tions of guys meet-ing Rules 215C4,215C5, and 279A1exposed to

0 to 300 V⑪ ⑯ ;neutral conductorsmeeting Rule230E1; supply

cables meeting Rule230C1(ft.)

Supplycables of 0to 750 VmeetingRule

230C2 or230C3(ft.)

Unguarded rigidlive parts, 0 to

750 V;noninsulatedcommunicationconductors;ungrounded

equipment cases,0 to 750 V; andungrounded por-tions of guysmeeting Rules215C4, 215C5,and 279A1

exposed to opensupply con-

ductors of over300 V to 750V⑤⑯(ft.)

Supplycables over750 V meet-ing Rule230C2 or

230C3; opensupply con-ductors, 0 to750 V⑮(ft.)

Unguardedrigid live parts,over 750 V to22 kV; ungroun-

dedportions of

guysmeeting Rules215C4, 215C5,and 279A1exposed toover 750 V to22 kV⑤⑯

(ft.)

Open supplyconductors,over 750 V to

22 kV(ft.)

Open Supply ConductorsElevation Range: Sea Level to 3300 ft.†

22

kV

to

27

kV

ph

ase

- to

- gro

un

d

46

kV

ph

ase

- to

-ph

ase

(F

t.)

27

kV

to

42

kV

ph

ase

- to

- gro

un

d

69

kV

ph

ase

- to

- ph

ase

(F

t.)

42

kV

to

70

kV

ph

ase

to

- gro

un

d

11

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

70

kV

to

84

kV

ph

ase

- to

- gro

un

d

13

8 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

8

4 k

V t

o 9

8 k

V p

ha

se- t

o- g

rou

nd

16

1 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

98

kV

to

14

0 k

V p

ha

se- t

o- g

rou

nd

23

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

14

0 k

V t

o 2

10

kV

ph

ase

- to

- gro

un

d

34

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

21

0 k

V t

o 3

18

kV

ph

ase

- to

- gro

un

d

50

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

1. Buildingsa. Horizontal(1) Towalls, projections, and guardedwindows

4.5②⑦ 5.0② 5.0② 5.5②⑨ 7.0② 7.5②⑩ 7.7 8.2 9.1 9.6 10.1 11.5 13.8 17.4

(2) Tounguarded windows⑧ 4.5 5.0 5.0 5.5⑨ 7.0 7.5⑩ 7.7 8.2 9.1 9.6 10.1 11.5 13.8 17.4

(3) Tobalconies and areas readilyaccessible to pedestrians③

4.5 5.0 5.0 5.5⑨ 7.0 7.5⑩ 7.7 8.2 9.1 9.6 10.1 11.5 13.8 17.4

b. Vertical⑭(1) Over or under roofs or projectionsnot readily accessible topedestrians③

3.0 3.5 10.0 10.5 12.0 12.5 12.7 13.2 14.1 14.6 15.1 16.5 18.8 22.4

(2) Over or under roofs, balconies,decks, or similar structures readilyaccessible to pedestrians③

10.5 11.0 11.0 11.5 13.0 13.5 13.7 14.2 15.1 15.6 16.1 17.5 19.8 23.4

(3) Over roofs, ramps, decks, and load-ing docks accessible to vehicles butnot subject to truck traffic⑥

10.5 11.0 11.0 11.5 13.0 13.5 13.7 14.2 15.1 15.6 16.1 17.5 19.8 23.4

† Unhighlighted columns courtesy of IEEE, (National Electrical Safety Code® (NESC®) (Accredited Standards Committee C2-2017). All rights reserved. The highlighted columns are not in the NESC Table 234-1 (2017). Theywere added to indicateminimum clearance requirements for voltages above 22 kV line to ground, and the values were calculated based on the NESC Rule 234G1 (2017). Values are rounded up to the nearest tenth of a foot.


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Deviation from this standard requires prior approval. Contact the standards engineering manager for approval processes and forms.Printed versions of this standard may be out of date. Please consult the online standards for the most recent version. This document shall be used and duplicated only in support of PacifiCorp projects. ©2017 by PacifiCorp.


Table 5 (Expanded Table 234-1, continued) Clearance of wires, conductors, cables, and unguarded rigid live parts adjacent but not attached to

buildings and other installations except bridges(Voltages are phase-to-ground for effectively grounded circuits and those other circuits where all ground faults are cleared by promptly de-energizing the faulted section, both initially and following subsequent breaker operations.See the definitions section for voltages of other systems. Clearances are with NOWIND displacement except where stated in the footnotes below. See Rules 234A, 234C1a, 234C2, and 234H4.) Revisions are in green and

italicized.

Insulatedcommunicationconductors and

cables; messengers;overhead shield/surge-protectionwires; effectivelygrounded guys;

ungrounded portionsof guys meeting Rules215C4, 215C5, and279A1 exposed to

0 to 300 V⑪ ⑯ ; neut-ral conductors meet-ing Rule 230E1;

supply cables meetingRule 230C1(ft.)

Supplycablesof 0 to750 VmeetingRule230C2or

230C3(ft.)

Unguarded rigidlive parts, 0 to

750 V;noninsulatedcommunicationconductors;ungroundedequipment

cases, 0 to 750V; and ungroun-ded portions ofguys meetingRules 215C4,215C5, and

279A1 exposedto open supplyconductors ofover 300 V to750 V⑤ ⑯

(ft.)

Supplycables over750 V meet-ing Rule230C2 or

230C3; opensupply con-ductors, 0 to750 V⑮(ft.)

Unguardedrigid liveparts, over750 V to 22kV; ungroun-

dedportions of

guysmeetingRules215C4,

215C5, and279A1

exposed toover 750 Vto 22 kV⑤

⑯(ft.)

Open sup-ply con-ductors,over 750 Vto 22 kV(ft.)


22

kV

to

27

kV

ph

ase

- to

- gro

un

d

46

kV

ph

ase

- to

-ph

ase

(F

t.)

27

kV

to

42

kV

ph

ase

- to

- gro

un

d

69

kV

ph

ase

- to

- ph

ase

(F

t.)

42

kV

to

70

kV

ph

ase

to

- gro

un

d

11

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

70

kV

to

84

kV

ph

ase

- to

- gro

un

d

13

8 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

8

4 k

V t

o 9

8 k

V p

ha

se- t

o- g

rou

nd

16

1 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

98

kV

to

14

0 k

V p

ha

se- t

o- g

rou

nd

23

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

14

0 k

V t

o 2

10

kV

ph

ase

- to

- gro

un

d

34

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

21

0 k

V t

o 3

18

kV

ph

ase

- to

- gro

un

d

50

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

(4) Over roofs, ramps, decks, andloading docks accessible to trucktraffic⑥⑱

15.5 16.0 16.0 16.5 18.0 18.5 18.7 19.2 20.1 20.6 21.1 22.5 24.8 28.4

2. Signs, chimneys, billboards, radio and television antennas, flagpoles and flags, banners, tanks, and other install-ations not classified as buildings or bridges⑰

a. Horizontal④

1) Toportions that are readily access-ible to pedestrians③

4.5 5.0 5.0② 5.5⑨ 7.0② 7.5⑩ 7.7 8.2 9.1 9.6 10.1 11.5 13.8 17.4

(2) Toportions that are not readilyaccessible to pedestrians③

3.0 3.5 5.0② 5.5②⑨ 7.0② 7.5②⑩ 7.7 8.2 9.1 9.6 10.1 11.5 13.8 17.4

b. Vertical

(1) Over or under catwalks and othersurfaces upon which personnel walk

10.5 11.0 11.0 11.5 13.0 13.5 13.7 14.2 15.1 15.6 16.1 17.5 19.8 23.4

(2) Over or under other portions ofsuch installations④

3.0 3.5 5.5 6.0 7.5 8.0 8.2 8.7 9.6 10.1 10.6 12.0 14.3 17.9

† Unhighlighted columns courtesy of IEEE, (National Electrical Safety Code® (NESC®) (Accredited Standards Committee C2-2017). All rights reserved. The highlighted columns are not in the NESC Table 234-1 (2017). They wereadded to indicateminimum clearance requirements for voltages above 22 kV line to ground, and the values were calculated based on the NESC Rule 234G1 (2017). Values are rounded up to the nearest tenth of a foot. Revisionsare in green and italicized.


Page 14of 34


Last Reviewed: 18Apr 17Deviation from this standard requires prior approval. Contact the standards engineering manager for approval processes and forms.Printed versions of this standard may be out of date. Please consult the online standards for the most recent version. This document shall be used and duplicated only in support of PacifiCorp projects. ©2017 by PacifiCorp.


Table 6—Clearance of wires, conductors, cables, and unguarded rigid live parts adjacent but not attached to buildings and other installations except

bridges for voltages exceeding 50 kV line to ground and at elevations exceeding 3300 feet.†

Clearance of

Open supply con-ductors, over750 V to 22 kV

(ft.)

Open Supply ConductorsElevation Range: 3301 to 6300 ft.



50

kV

to

70

kV

ph

ase

- to

- gro

un

d

11

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

70

kV

to

84

kV

ph

ase

- to

- gro

un

d

13

8 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

84

kV

to

98

kV

ph

ase

- to

- gro

un

d

16

1 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

98

kV

to

14

0 k

V p

ha

se- t

o- g

rou

nd

23

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

14

0 k

V t

o 2

10

kV

ph

ase

- to

- gro

un

d

34

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

21

0 k

V t

o 3

18

kV

ph

ase

- to

- gro

un

d

50

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

50

kV

to

70

kV

ph

ase

- to

- gro

un

d

11

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

70

kV

to

84

kV

ph

ase

- to

- gro

un

d

13

8 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

84

kV

to

98

kV

ph

ase

- to

- gro

un

d

16

1 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

98

kV

to

14

0 k

V p

ha

se- t

o- g

rou

nd

23

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

14

0 k

V t

o 2

10

kV

ph

ase

- to

- gro

un

d

34

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

21

0 k

V t

o 3

18

kV

ph

ase

- to

- gro

un

d

50

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

50

kV

to

70

kV

ph

ase

- to

- gro

un

d

11

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

70

kV

to

84

kV

ph

ase

- to

- gro

un

d

13

8 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

84

kV

to

98

kV

ph

ase

- to

- gro

un

d

16

1 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

98

kV

to

14

0 k

V p

ha

se- t

o- g

rou

nd

23

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

14

0 k

V t

o 2

10

kV

ph

ase

- to

- gro

un

d

34

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

21

0 k

V t

o 3

18

kV

ph

ase

- to

- gro

un

d

50

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

1. Buildings

a. Horizontal

(1) Towalls, projections, andguarded windows

7.5②⑩ 9.3 9.8 10.4 11.9 14.4 18.3 9.4 10.0 10.6 12.3 15.0 19.2 9.6 10.2 10.9 12.6 15.6 20.1

(2) Tounguarded windows⑧ 7.5⑩ 9.3 9.8 10.4 11.9 14.4 18.3 9.4 10.0 10.6 12.3 15.0 19.2 9.6 10.2 10.9 12.6 15.6 20.1

(3) Tobalconies and areas readilyaccessible to pedestrians③

7.5⑩ 9.3 9.8 10.4 11.9 14.4 18.3 9.4 10.0 10.6 12.3 15.0 19.2 9.6 10.2 10.9 12.6 15.6 20.1

b. Vertical⑭

(1) Over or under roofs or pro-jections not readily accessible topedestrians③

12.5 14.3 14.8 15.4 16.9 19.4 23.3 14.4 15.0 15.6 17.3 20.0 24.2 14.6 15.2 15.9 17.6 20.6 25.1

(2) Over or under balconies,porches, decks, and roofs readilyaccessible to pedestrians③

13.5 15.3 15.8 16.4 17.9 20.4 24.3 15.4 16.0 16.6 18.3 21.0 25.2 15.6 16.2 16.9 18.6 21.6 26.1

(3) Over roofs, ramps, decks, andloading docks accessible tovehicles but not subject to trucktraffic⑥

13.5 15.3 15.8 16.4 17.9 20.4 24.3 15.4 16.0 16.6 18.3 21.0 25.2 15.6 16.2 16.9 18.6 21.6 26.1

† Unhighlighted columns courtesy of IEEE, (National Electrical Safety Code® (NESC®) (Accredited Standards Committee C2-2017). All rights reserved. The highlighted columns are not in the NESC Table 234-1 (2017). Thistable was created to indicateminimum clearance requirements for voltages above 50 kV line to ground and at elevations exceeding 3300 feet above sea level. The values were calculated based on the NESC Rule 234G1 and234G2 (2017) and rounded up to the nearest tenth of a foot. Revisions are in green and italicized.


Page 15of 34





Table 6 continued—Clearance of wires, conductors, cables, and unguarded rigid live parts adjacent but not attached to buildings and other

installations except bridgesfor voltages exceeding 50 kV line to ground and at elevations exceeding 3300 feet.†

Clearance of

Open supply con-ductors, over750 V to 22 kV

(ft.)




50

kV

to

70

kV

ph

ase

- to

- gro

un

d

11

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

70

kV

to

84

kV

ph

ase

- to

- gro

un

d

13

8 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

84

kV

to

98

kV

ph

ase

- to

- gro

un

d

16

1 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

98

kV

to

14

0 k

V p

ha

se- t

o- g

rou

nd

23

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

14

0 k

V t

o 2

10

kV

ph

ase

- to

- gro

un

d

34

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

21

0 k

V t

o 3

18

kV

ph

ase

- to

- gro

un

d

50

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

50

kV

to

70

kV

ph

ase

- to

- gro

un

d

11

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

70

kV

to

84

kV

ph

ase

- to

- gro

un

d

13

8 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

84

kV

to

98

kV

ph

ase

- to

- gro

un

d

16

1 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

98

kV

to

14

0 k

V p

ha

se- t

o- g

rou

nd

23

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

14

0 k

V t

o 2

10

kV

ph

ase

- to

- gro

un

d

34

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

21

0 k

V t

o 3

18

kV

ph

ase

- to

- gro

un

d

50

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

50

kV

to

70

kV

ph

ase

- to

- gro

un

d

11

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

70

kV

to

84

kV

ph

ase

- to

- gro

un

d

13

8 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

84

kV

to

98

kV

ph

ase

- to

- gro

un

d

16

1 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

98

kV

to

14

0 k

V p

ha

se- t

o- g

rou

nd

23

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

14

0 k

V t

o 2

10

kV

ph

ase

- to

- gro

un

d

34

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

21

0 k

V t

o 3

18

kV

ph

ase

- to

- gro

un

d

50

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

4) Over roofs, ramps, decks, andloading docks accessible to trucktraffic⑱

18.5 20.3 20.8 21.4 22.9 25.4 29.3 20.4 21.0 21.6 23.3 26.0 30.2 20.6 21.2 21.9 23.6 26.6 31.1

2. Signs, chimneys, billboards, radio and tele-vision antennas, flagpoles and flags, banners,tanks, and other installations not classified asbuildings or bridges⑰

a. Horizontal④

(1) Toportions that are readilyaccessible to pedestrians③

7.5⑩ 9.3 9.8 10.4 11.9 14.4 18.3 9.4 10.0 10.6 12.3 15.0 19.2 9.6 10.2 10.9 12.6 15.6 20.1

(2) Toportions that are not readilyaccessible to pedestrians③

7.5①②⑩ 9.3 9.8 10.4 11.9 14.4 18.3 9.4 10.0 10.6 12.3 15.0 19.2 9.6 10.2 10.9 12.6 15.6 20.1

b. Vertical

(1) Over or under catwalks andother surfaces upon which per-sonnel walk

13.5 15.3 15.8 16.4 17.9 20.4 24.3 15.4 16.0 16.6 18.3 21.0 25.2 15.6 16.2 16.9 18.6 21.6 26.1

(2) Over or under other portionsof such installations④

8.0 9.8 10.3 10.9 12.4 14.9 18.8 9.9 10.5 11.1 12.8 15.5 19.7 10.1 10.7 11.4 13.1 16.1 20.6

† Unhighlighted columns courtesy of IEEE, (National Electrical Safety Code® (NESC®) (Accredited Standards Committee C2-2017). All rights reserved. The highlighted columns are not in the NESC Table 234-1 (2017). This table was cre-ated to indicate minimum clearance requirements for voltages above 50 kV line to ground and at elevations exceeding 3300 feet above sea level. The values were calculated based on the NESCRule 234G1 and 234G2 (2017) and roun-ded up to the nearest tenth of a foot.


Page 16of 34




TC 151Clearances ofWires, Conductors, Cables, and Equipment from Buildings, Bridges, and Other Installations1 8 Ap r 1 71 8 Ap r1 7

NOTE: The following notes appear courtesy IEEE, (National Electrical Safety Code® (NESC®) (AccreditedStandards Committee C2-2017). All rights reserved.

NOTE: The clearance values shown in this table are computed by adding the applicable Mechanical and Electrical (M& E) value of Table A-1 to the applicable Reference Component of Table A-2b of Appendix A.

① Not used in this edition.

② Where available space will not permit this value, the clearance may be reduced by 2 ft. provided the wires, con-ductors, or cables, including splices and taps, and unguarded rigid live parts have a covering that provides sufficientdielectric strength to limit the likelihood of a short circuit in case of momentary contact with a structure or building.

③ A roof, balcony, or similar structure is considered readily accessible to pedestrians if it can be casually accessedthrough a doorway, window, ramp, stairway, or permanently mounted ladder by a person, on foot, who neither exertsextraordinary physical effort nor employs tools or devices to gain entry. A permanently mounted ladder is not con-sidered a means of access if its bottom rung is 8 ft. or more from the ground or other permanently installed access-ible surface or is otherwise equipped with barriers to inhibit climbing by unauthorized persons.

④ The required clearances shall be to the closest approach of motorized signs or moving portions of installationscovered by Rule 234C.

⑤ The portion(s) of span guys between guy insulators and the portion(s) of anchor guys above guy insulators thatare not effectively grounded shall have clearances based on the highest voltage to which they may be exposed due to aslack conductor or guy.

⑥ For the purpose of this rule, trucks are defined as any vehicle exceeding 8 ft. in height.

⑦ This clearance may be reduced to 3 in for the effectively grounded portions of guys.

⑧ Windows not designed to open may have the clearances permitted for walls and projections.

⑨ The clearance at rest shall be not less than the value shown in this table. Also, when the conductor or cable is dis-placed by wind, the clearance shall be not less than 3.5 ft.; see Rule 234C1b.

⑩ The clearance at rest shall be not less than the value shown in this table. Also, when the conductor or cable is dis-placed by wind, the clearance shall be not less than 4.5 ft.; see Rule 234C1b.

⑪ The portion of anchor guys below the lowest insulator meeting Rules 279A1 and 215C5 may have the same clear-ance as effectively grounded guys.

⑫ This footnote not used in this edition.

⑬ This footnote not used in this edition.

⑭ For clearances above railings, walls, or parapets around balconies, decks, or roofs, use the clearances required forrow 1b(1). For such clearances where an outside stairway exists to provide access to such balconies, decks, or roofs,use the clearances required for row 2b(2).

⑮ Does not include neutral conductors meeting Rule 230E1.

⑯ These clearance values also apply to guy insulators.


Page 17of 34





⑰ It is presumed that a flag or banner is fully extended but that there is no deflection or displacement of the flagpoleor other supporting structure due to wind and that the conductors, cables, or rigid live parts are not displaced by thewind. The specified clearance is measured to the point of maximum displacement of the banner or flag towards theoverhead utility facility.

⑱ When designing a line to accommodate oversized vehicles, these clearance values shall be increased by the dif-ference between the known height of the oversized vehicle and 14 ft.

NESC Rule 234D (2017)

Clearance of wires, conductors, cables, and unguarded rigid live parts from bridges

1. Vertical and horizontal clearancesa. Clearances

Unguarded or accessible wires, conductors, cables, or rigid live parts may be located adjacent to or within a bridgestructure. The vertical and horizontal clearances of such rigid and nonrigid parts shall be not less than the valuesgiven in Table 234-2 [Table 8 in this document] when at rest under the conditions specified in Rule 234A1, asillustrated in Figures 234-1(a) and 234-1(b).

EXCEPTION: This rule does not apply to insulated communication cables, effectively grounded guys, spanwires, and surge protection wires; neutrals meeting Rule 230E1; and supply cables meeting Rule 230C1.

b. Horizontal clearances under wind displacement conditions

When the following conductors and cables are displaced from rest under the wind conditions of Rule 234A2, hori-zontal clearances from such conductors or cables to bridges shall be not less than those shown below:


Page 18of 34





Table 7—Horizontal Clearance WITHWIND of Wires, Conductors, Cables, and Unguarded

Rigid Live Parts from Bridges†

Conductor or cable


(m) (ft.)

Elevation:

3301 to 6300 ft.

Elevation:

6301 to 9300 ft.

Elevation:

9301 to 12300 ft.

(ft.) (ft.) (ft.)


230C2 cable, above 750 V 1.1 3.5 3.5 3.5 3.5

230C3 cable, above 750 V 1.1 3.5 3.5 3.5 3.5

Open supply conductors,over 750 V to 22 kV

1.4 4.5 4.5 4.5 4.5


-- 4.7 4.7 4.7 4.7


-- 5.2 5.2 5.2 5.2


-- 6.1 6.3 6.4 6.6


-- 6.6 6.8 7.0 7.2


-- 7.1 7.4 7.6 7.9


-- 8.5 8.9 9.3 9.6


-- 10.8 11.4 12.0 12.6


-- 14.4 15.3 16.2 17.1


See Footnotes 8 and 9 NESC Table 234-2 [Table 8 in this document].

† The non-highlighted portion of the table was copied from the NESC Rule 234D1b courtesy of IEEE, (National ElectricalSafety Code® (NESC®) (Accredited Standards Committee C2-2017). All rights reserved. The highlighted portion was addedto account for voltage and/or elevation adders for applicable voltages. These adders were calculated based on the NESCRule 234G1 and 234G2 (2017).

2. Guarding trolley-contact conductors located under bridgesa. Where guarding is required

Guarding is required where the trolley-contact conductor is located so that a trolley pole leaving the conductor canmake simultaneous contact between it and the bridge structure.

b. Nature of guarding

Guarding shall consist of a substantial inverted trough of nonconducting material located above the contactconductor, or of other suitable means of limiting the likelihood of contact between the trolley support and thebridge structure.


Page 19of 34





TC 151Clearances ofWires, Conductors, Cables, and Equipment from Buildings, Bridges, and Other Installations

1 8 Ap r 1 7

1 8 Ap r 1 7

Table 8—(Expanded NESC Table 234-2) Clearance of wires, conductors, cables, and unguarded rigid live parts from bridges

(Voltages are phase-to-ground for effectively grounded circuits and those other circuits where all ground faults are cleared by promptly de-energizing the faulted section, both initially and following subsequent breaker operations.See the definitions section for voltages of other systems. Clearances are with NOWIND displacement except where stated in the footnotes below. See Rules 234A, 234D1a, and 234H4.) Table revisions are in green and italicized.

Unguarded rigid liveparts,

0 to 750 V; non-insulated

communication con-ductors; supply cablesof 0 to 750 V meeting

Rule 230C2 or230C3⑦ , ungroundedequipment cases,

0 to 750 V; ungroundedportions of guys meet-ing Rules 215C2 and279A1 exposed to opensupply conductors over300 V to750 V④⑪

(ft.)

Supply cablesover 750 V meetingRule 230C2 or

230C3⑦ ; open sup-ply conductors, 0 to

750 V⑩(ft.)

Opensupply

conductors,over750 V to22 kV(ft.)

Unguarded rigidlive parts, over750 V to 22 kV,

ungrounded equipmentcases, 750 V to 22 kV;

ungrounded portions of guysmeeting Rules 215C2 and279A1 exposed to open sup-ply conductors of over750 V to 22 kV④⑪

(ft.)

Open Supply ConductorsElevation Range: Sea Level to 3300 ft†

22

kV

to

27

kV

ph

ase

- to

- gro

un

d

46

kV

ph

ase

- to

-ph

ase

(F

t.)

27

kV

to

42

kV

ph

ase

- to

- gro

un

d

69

kV

ph

ase

- to

- ph

ase

(F

t.)

42

kV

to

70

kV

ph

ase

to

- gro

un

d

11

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

70

kV

to

84

kV

ph

ase

- to

- gro

un

d

13

8 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

8

4 k

V t

o 9

8 k

V p

ha

se- t

o- g

rou

nd

16

1 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

98

kV

to

14

0 k

V p

ha

se- t

o- g

rou

nd

23

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

14

0 k

V t

o 2

10

kV

ph

ase

- to

- gro

un

d

34

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

21

0 k

V t

o 3

18

kV

ph

ase

- to

- gro

un

d

50

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

1. Clearance over bridges①

a. Attached③ 3.0 3.5 5.5 5.0 5.7 6.2 7.1 7.6 8.1 9.5 11.8 15.4

b. Not attached 10.0 10.5 12.5 12.0 12.7 13.2 14.1 14.6 15.0 16.4 18.8 22.4

2. Clearance beside, under, or within bridgestructure⑥

a. Readily accessible portions of any bridge including wing, walls, and bridge attachments①

(1) Attached③ 3.0 3.5⑧ 5.5⑨ 5.0 5.7 6.2 7.1 7.6 8.0 9.4 11.8 15.4

(2) Not attached 5.0 5.5⑧ 7.5⑨ 7.0 7.7 8.2 9.1 9.6 10.0 11.4 13.8 17.4

b. Ordinarily inaccessible portions of bridges (other than brick, concrete, or masonry) and fromabutments②

(1) Attached③⑤ 3.0 3.5⑧ 5.5⑨ 5.0 5.7 6.2 7.1 7.6 8.0 9.4 11.8 15.4

(2) Not attached④ ⑤ 4.0 4.5⑧ 6.5⑨ 6.0 6.7 7.2 8.1 8.6 9.0 10.4 12.8 16.4

† Unhighlighted columnscourtesyof IEEE, (NationalElectricalSafetyCode® (NESC®) (Accredited StandardsCommittee C2-2017). All rights reserved. The highlighted columnsare not in theNESC Table 234-2 (2017). Theywere added to indicateminimum clearance requirements for voltagesabove 22 kV line to ground, and the valueswere calculated based on the NESC Rule 234G1(2017). Valuesare rounded up to the nearest tenth of a foot.


Page 20of 34




Table 9—Clearance of wires, conductors, cables, and unguarded rigid live parts from bridges for voltages exceeding 50 kV line to ground and at

elevations exceeding 3300 feet.†

Open supplyconductors,over 750 Vto 22 kV(ft.)




50

kV

to

70

kV

ph

ase

- to

- gro

un

d

11

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

70

kV

to

84

kV

ph

ase

- to

- gro

un

d

13

8 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

84

kV

to

98

kV

ph

ase

- to

- gro

un

d

16

1 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

98

kV

to

14

0 k

V p

ha

se- t

o- g

rou

nd

23

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

14

0 k

V t

o 2

10

kV

ph

ase

- to

- gro

un

d

34

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

21

0 k

V t

o 3

18

kV

ph

ase

- to

- gro

un

d

50

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

50

kV

to

70

kV

ph

ase

- to

- gro

un

d

11

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

70

kV

to

84

kV

ph

ase

- to

- gro

un

d

13

8 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

84

kV

to

98

kV

ph

ase

- to

- gro

un

d

16

1 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

98

kV

to

14

0 k

V p

ha

se- t

o- g

rou

nd

23

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

14

0 k

V t

o 2

10

kV

ph

ase

- to

- gro

un

d

34

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

21

0 k

V t

o 3

18

kV

ph

ase

- to

- gro

un

d

50

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

50

kV

to

70

kV

ph

ase

- to

- gro

un

d

11

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

70

kV

to

84

kV

ph

ase

- to

- gro

un

d

13

8 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

84

kV

to

98

kV

ph

ase

- to

- gro

un

d

16

1 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

98

kV

to

14

0 k

V p

ha

se- t

o- g

rou

nd

23

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

14

0 k

V t

o 2

10

kV

ph

ase

- to

- gro

un

d

34

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

21

0 k

V t

o 3

18

kV

ph

ase

- to

- gro

un

d

50

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

1. Clearance over bridges①

a. Attached③ 5.5 7.3 7.8 8.4 9.9 12.4 16.3 7.4 8.0 8.6 10.3 13.0 17.2 7.6 8.2 8.9 10.6 13.6 18.1

b. Not attached 12.5 14.3 14.8 15.4 16.9 19.4 23.3 14.4 15.0 15.6 17.3 20.0 24.2 14.6 15.2 15.9 17.6 20.6 25.1

2. Clearance beside, under, or within bridgestructure⑥

a. Readily accessible portions of any bridge includingwing, walls, and bridge attachments①

(1) Attached③ 5.5⑨ 7.3 7.8 8.4 9.9 12.4 16.3 7.4 8.0 8.6 10.3 13.0 17.2 7.6 8.2 8.9 10.6 13.6 18.1

(2) Not attached 7.5⑨ 9.3 9.8 10.4 11.9 14.4 18.3 9.4 10.0 10.6 12.3 15.0 19.2 9.6 10.2 10.9 12.6 15.6 20.1

b. Ordinarily inaccessible portions of bridges (otherthan brick, concrete, or masonry) and fromabutments②

(1) Attached③⑤ 5.5⑨ 7.2 7.8 8.4 9.9 12.4 16.3 7.4 8.0 8.6 10.3 13.0 17.2 7.6 8.2 8.7 10.6 13.6 18.1

(2) Not attached④ ⑤ 6.5⑨ 8.3 8.8 9.4 10.9 13.4 17.3 8.4 9.0 9.6 11.3 14.0 18.2 8.6 9.2 9.9 11.6 14.6 19.1

† Unhighlighted columnscourtesyof IEEE, (NationalElectricalSafetyCode® (NESC®) (Accredited StandardsCommittee C2-2017). All rights reserved. The highlighted columnsare not in theNESC Table 234-2 (2017). This table was created to indicateminimum clearance requirements for voltagesabove 50 kV line to ground and at elevationsexceeding 3300 feet above sea level. Thevalueswere calculated based on the NESC Rule 234G1 and 234G2 (2017) and rounded up to the nearest tenth of a foot.


Page 21of 34






NOTE: The following notes appear courtesy IEEE, (National Electrical Safety Code® (NESC®) (AccreditedStandards Committee C2-2017). All rights reserved.

① Where over traveled ways on or near bridges, the clearances of Rule 232 apply also.

② Bridge seats of steel bridges carried on masonry, brick, or concrete abutments that require frequent access for inspec-tion shall be considered as readily accessible portions.

③ Clearance from supply conductors to supporting arms and brackets attached to bridges shall be the same as specifiedin Table 235-6 (Rule 235E1) if the supporting arms and brackets are owned, operated, or maintained by the same utility.

④ The portion(s) of span guys between guy insulators and the portion(s) of anchor guys above guy insulators that arenot effectively grounded shall have clearances based on the highest voltage to which they may be exposed due to a slackconductor or guy.

⑤ Where conductors passing under bridges are adequately guarded against contact by unauthorized persons and can bede-energized and grounded per Rule 444D for maintenance of the bridge, clearances of the conductors from the bridge,at any point, may have the clearances specified in Table 235-6 for clearance from surfaces of support arms plus one-half the final sag at 15 °C (60 °F), no wind of the conductor at that point.

⑥ Where the bridge has moving parts, such as a lift. bridge, the required clearances shall be maintained throughout thefull range of movement of the bridge or any attachment thereto.

⑦ Where permitted by the bridge owner, supply cables may be run in rigid conduit attached directly to the bridge. Referto Part 3 for installation rules.

⑧ The clearance at rest shall be not less than the value shown in this table. Also, when the conductor or cable is dis-placed by wind, the clearance shall be not less than 3.5 ft.; see Rule 234D1b.

⑨ The clearance at rest shall be not less than the value shown in this table. Also, when the conductor or cable is dis-placed by wind, the clearance shall be not less than 4.5 ft.; see Rule 234D1b.

⑩ Does not include neutral conductors meeting Rule 230E1.

⑪ These clearance values also apply to guy insulators.


Page 22of 34





NESC Rule 234E (2017)

Clearance of wires, conductors, cables, or unguarded rigid live parts installed over or near swimming areas with nowind displacement

1. Swimming pools

Where wires, conductors, cables, or unguarded rigid live parts are over in-ground or permanently installed above-ground swimming pools or the surrounding area, the clearances in any direction shall be not less than those shownin Table 234-3 [Table 10 in this document] and illustrated in Figure 3(a) (NESC 234-3(a)), Figure 3(b) (NESC234-3(b)), and Figure 3(c) (NESC 234-3(c)). Vertical clearances for permanently installed aboveground pools shallbe measured from the highest location where people can stand.

NOTE 1: Permanently installed aboveground pools are ones that are not intended to be moved or routinely dis-assembled.

NOTE 2: For NESC clearance purposes, spas (including whirlpools, hot-tubs, jacuzzis, or other similar install-ations not suitable for swimming) are not considered as swimming pools covered by Rule 234E, Table 234-3[Table 10 in this document]. Note that this rule and table refer to swimming areas and swimming pools. NESCTable 234-3 clearances allow for use of skimmer and rescue poles.

Spas, etc., not suitable for swimming, are usually installed as part of a building or as a similar installation. Clear-ances for such installations are found in Table 234-1 [Table 5 in this document]. Vertical clearance should be fromthe highest point of the installation upon which people can stand. See row 1, Buildings, in Table 234-1 for install-ations that are part of buildings, such as a raised spa on an open deck. See row 2, other installations, in Table 234-1for free-standing installations.

For portable wading pools, see Table 232-1, row 5.

EXCEPTION 1: This rule does not apply to a pool fully enclosed by a solid or screened permanent structure.

EXCEPTION 2: This rule does not apply to communication conductors and cables, effectively grounded surge-pro-tection wires, neutral conductors meeting Rule 230E1, guys and messengers, supply cables meeting Rule 230C1, andsupply cables of 0 to 750 V meeting Rule 230C2 or 230C3 when these facilities are 3 m. (10 ft.) or more horizontallyfrom the edge of the pool, diving platform, diving tower, water slide, or other fixed, pool-related structures.

2. Beaches and waterways restricted to swimming

Where rescue poles are used by lifeguards at supervised swimming beaches, the vertical and horizontal clearancesshall be not less than those shown in Table 234-3 [Table 10 in this document].Where rescue poles are not used, theclearances shall be as specified in Rule 232.

3. Waterways subject to water skiing

The vertical clearance shall be the same as that specified in Rule 232.


Page 23of 34





Figure 3a (NESC 234-3a)—Swimming Pool Clearances

Figure 3b (NESC 234-3b)—Aboveground Swimming Pool with Deck

Figure 3c (NESC 234-3c)—Aboveground Swimming Pool without Deck


Page 24of 34






1 8 Ap r 1 7

1 8 Ap r 1 7

Table 10—(Expanded NESC Table 234-3) Clearance of wires, conductors, cables, or unguarded

rigid live parts over or near swimming pools(Voltages are phase-to-ground for effectively grounded circuits and those other circuits where all ground faults are cleared by promptly de-energizing the faulted section, both initially and following subsequent breaker operations.

See the definitions section for voltages of other systems. Clearances are with NOWIND displacement. Table revisions are in green and italicized.See Rules 234A, 234E1, 234E2, and 234H4.)

Insulated com-munication conductorsand cables; mes-sengers; overheadshield/ surge-pro-tection wires; groun-ded guys; ungroundedportions of guys meet-ing Rules 215C2 and279A1 exposed to 0 to300 V②④ ; neutral con-ductors meeting Rule230E1; supply cablesmeeting Rule 230C1

(ft.)

Unguarded rigid liveparts,

0 to 750 V;noninsulated com-munication con-

ductors; supply cablesof 0 to 750 V meetingRule 230C2 or 230C3;ungrounded portionsof guys meeting Rules215C2 and 279A1

exposed to open sup-ply conductors of over300 V to 750 V①④

(ft.)

Supplycables over750 VmeetingRule 230C2or 230C3;open sup-ply con-ductors, 0to 750 V③(ft.)

Unguarded rigidlive parts over750 V to 22 kV;ungrounded por-tions of guys meet-ing Rules 215C2 and279A1 exposed toover 750 V to 22

kV①④

(ft.)

Open sup-ply con-ductors,over 750 Vto 22 kV(ft.)


22

kV

to

27

kV

ph

ase

- to

- gro

un

d

46

kV

ph

ase

- to

-ph

ase

(F

t.)

27

kV

to

42

kV

ph

ase

- to

- gro

un

d

69

kV

ph

ase

- to

- ph

ase

(F

t.)

42

kV

to

70

kV

ph

ase

to

- gro

un

d

11

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

70

kV

to

84

kV

ph

ase

- to

- gro

un

d

13

8 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

8

4 k

V t

o 9

8 k

V p

ha

se- t

o- g

rou

nd

16

1 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

98

kV

to

14

0 k

V p

ha

se- t

o- g

rou

nd

23

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

14

0 k

V t

o 2

10

kV

ph

ase

- to

- gro

un

d

34

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

21

0 k

V t

o 3

18

kV

ph

ase

- to

- gro

un

d

50

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

A. Clearance in any direction fromthewater level, edge of pool, baseof diving platform, or anchoredraft

22.0 22.5 23.0 24.5 25.0 25.2 25.7 26.6 27.1 27.6 29.0 31.3 34.9

B. Clearance in any direction to thediving platform, tower, water slide,or other fixed, pool-related struc-tures

14.0 14.5 15.0 16.5 17.0 17.2 17.7 18.6 19.1 19.6 21.0 23.3 26.9

V. Vertical clearance over adjacentland

Clearance shall be as required by Rule 232. Clearance shall be as required by Rule 232. (See TC 111).

† Unhighlighted columnscourtesyof IEEE, (NationalElectricalSafetyCode® (NESC®) (Accredited StandardsCommittee C2-2017). All rights reserved. The highlighted columnsare not in theNESC Table 234-3 (2017). Theywere added to indicateminimum clearance requirements for voltagesabove 22 kV line to ground, and the valueswere calculated based on the NESC Rule 234G1(2017). Valuesare rounded up to the nearest tenth of a foot.


Page 25of 34





Table 11 —Clearance of wires, conductors, cables, or unguarded rigid live parts over or near swimming pools for voltages exceeding 50 kV line to

ground and at elevations exceeding 3300 feet.†

Open supplyconductors,

over750 Vto 22 kV(ft.)




50

kV

to

70

kV

ph

ase

- to

- gro

un

d

11

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

70

kV

to

84

kV

ph

ase

- to

- gro

un

d

13

8 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

84

kV

to

98

kV

ph

ase

- to

- gro

un

d

16

1 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

98

kV

to

14

0 k

V p

ha

se- t

o- g

rou

nd

23

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

14

0 k

V t

o 2

10

kV

ph

ase

- to

- gro

un

d

34

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

21

0 k

V t

o 3

18

kV

ph

ase

- to

- gro

un

d

50

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

50

kV

to

70

kV

ph

ase

- to

- gro

un

d

11

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

70

kV

to

84

kV

ph

ase

- to

- gro

un

d

13

8 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

84

kV

to

98

kV

ph

ase

- to

- gro

un

d

16

1 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

98

kV

to

14

0 k

V p

ha

se- t

o- g

rou

nd

23

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

14

0 k

V t

o 2

10

kV

ph

ase

- to

- gro

un

d

34

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

21

0 k

V t

o 3

18

kV

ph

ase

- to

- gro

un

d

50

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

50

kV

to

70

kV

ph

ase

- to

- gro

un

d

11

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

70

kV

to

84

kV

ph

ase

- to

- gro

un

d

13

8 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

84

kV

to

98

kV

ph

ase

- to

- gro

un

d

16

1 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

98

kV

to

14

0 k

V p

ha

se- t

o- g

rou

nd

23

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

14

0 k

V t

o 2

10

kV

ph

ase

- to

- gro

un

d

34

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

21

0 k

V t

o 3

18

kV

ph

ase

- to

- gro

un

d

50

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

A. Clearance in any direction from thewater level, edge of pool, base ofdiving platform, or anchored raft

25.0 26.8 27.3 27.9 29.4 31.9 35.9 26.9 27.5 28.1 29.8 32.5 36.7 27.1 27.7 28.4 30.1 33.1 37.6

B. Clearance in any direction to thediving platform, tower, water slide, orother fixed, pool-related structures

17.0 18.8 19.3 19.9 21.4 23.9 27.8 18.9 19.5 20.1 21.8 24.5 27.8 19.1 19.7 20.4 22.1 25.1 29.6

V. Vertical clearance over adjacentland

Clearance shall be as required by Rule 232. (See TC 111).

† Unhighlighted columns courtesy of IEEE, (National Electrical Safety Code® (NESC®) (Accredited Standards Committee C2-2017). The highlighted columns are not in the NESC Table 234-3 (2017). All rights reserved. Thistable was created to indicateminimum clearance requirements for voltages above 50 kV line to ground and at elevations exceeding 3300 feet above sea level. The values were calculated based on the NESC Rule 234G1 and234G2 (2017) and rounded up to the nearest tenth of a foot.

NOTE 1:A, B, and V are shown in Figure 3 (NESC 234-3).NOTE 2: The clearance values shown in this table are computed by adding the applicable Mechanical and Electrical (M & E) value of Table A-1 to the applicableReference Component of Table A-2b of Appendix A.① The portion(s) of span guys between guy insulators and the portion(s) of anchor guys above guy insulators that are not effectively grounded shall have clear-ances based on the highest voltage to which they may be exposed due to a slack conductor or guy.② The portion of anchor guys below the lowest insulator meeting Rules 279A1 and 215C2amay have the same clearance as effectively grounded guys.③ Does not include neutral conductors meeting Rule 230E1.④ These clearance values also apply to guy insulators.


Page 26of 34





NESC Rule 234F (2017)

Clearances of wires, conductors, cables, and rigid live parts from grain bins

1. Grain bins loaded by permanently installed augers, conveyers, or elevator systems

All portions of grain bins that are expected to be loaded by the use of a permanently installed auger, conveyer, or elev-ator system shall be considered as a building or other installation under Rule 234C for the purpose of determiningappropriate clearances of wires, conductors, cables, and rigid live parts. In addition, the following clearances shallalso apply without wind displacement. See Figure 4 (NESC 234-4a).

a. A clearance of not less than 5.5 m. (18 ft.) in all directions above the grain bin shall be maintained from eachprobe port in the grain bin roof for all wires, conductors, and cables.

b. A horizontal clearance of not less than 4.6 m. (15 ft.) shall be maintained between grain bins and open supplyconductors, 0 to 22 kV. This clearance does not apply to a neutral conductor meeting Rule 230E1.

2. Grain bins loaded by portable augers, conveyers, or elevators (with no wind displacement)a. The clearance of wires, conductors, cables, and rigid live parts from grain bins that are expected to be loaded bythe use of a portable auger, conveyer, or elevator shall be not less than the values illustrated in Figure 5 (NESC234-4b).

EXCEPTION: Clearances of the following items on the nonloading side of grain bins shall be not less thanthose required by Rule 234C for clearances from buildings:

(a) Support arms; effectively grounded equipment cases(b) Insulated communication conductors and cables, messengers, surge-protection wires, effectivelygrounded guys, neutral conductors meeting Rule 230E1, and supply cables meeting Rule 230C1

(c) Supply cables of 0 to 750 V meeting Rule 230C2 or 230C3

b. Any side of a grain bin is considered to be a nonloading side if it is so designated, or if it is so closely abuttinganother structure or obstruction, or so close to a public road or other right-of-way that a portable auger, con-veyor, or elevator is not reasonably anticipated to be used over that side or portion to fill the grain bin.

c. Where an agreement excludes the use of portable augers, conveyors, or elevators from a designated portion of agrain bin, such portion is considered to be a nonloading side.


Page 27of 34





Figure 4 (NESC 234-4a)—Clearance envelope for grain bins filled by permanently installed

augers, conveyors, or elevators

LegendP = probe clearance 5.5 m. (18 ft.) required by Rule 234F1aH = horizontal clearance 4.6 m. (15 ft.) required by Rule 234F1bT = transition clearanceV1 = vertical clearance above a building required by Rule 234C (Table 234-1)V2 = vertical clearance required by Rule 232B (Table 232-1 or 232-2)


Page 28of 34





Figure 5 (NESC 234-4b)—Clearance envelope for grain bins filled by portable augers,

conveyors, or elevators


Page 29of 34






1 8 Ap r 1 7

1 8 Ap r 1 7

Table 12—Clearances of wires, conductors, cables, and rigid live parts from grain bins†

All wires,conductors,and cables(ft.)

Open supplyconductors,

0 V to22 kV‡(ft.)

Open Supply Conductors Elevation Range: Sea Level to 3300 ft.

22

kV

to

27

kV

ph

ase

- to

- gro

un

d

46

kV

ph

ase

- to

-ph

ase

(F

t.)

27

kV

to

42

kV

ph

ase

- to

- gro

un

d

69

kV

ph

ase

- to

- ph

ase

(F

t.)

42

kV

to

70

kV

ph

ase

to

- gro

un

d

11

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

70

kV

to

84

kV

ph

ase

- to

- gro

un

d

13

8 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

8

4 k

V t

o 9

8 k

V p

ha

se- t

o- g

rou

nd

16

1 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

98

kV

to

14

0 k

V p

ha

se- t

o- g

rou

nd

23

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

14

0 k

V t

o 2

10

kV

ph

ase

- to

- gro

un

d

34

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

21

0 k

V t

o 3

18

kV

ph

ase

- to

- gro

un

d

50

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

NESCRule 234F1a (2017) 18.0 18.2 18.7 19.6 20.1 20.6 22.0 24.3 27.9

NESCRule 234F1b (2017) 15.0 15.2 15.7 16.6 17.1 17.6 22.0 21.3 24.9

† The NESC (2017) doesnot provide this table. This table was created to indicateminimum clearance requirements for voltagesabove 22 kV line to ground. The base valueswere taken from theNESC Rule 234F1 (2017), and calculated valueswere derived based on the NESC Rule 234G1 (2017) and rounded up to the nearest tenth of a foot.

‡ Doesnot apply to a neutral conductor meeting Rule 230E1.


Page 30of 34




Table 13—Clearances of wires, conductors, cables, and rigid live parts from grain bins for voltages exceeding 50 kV line to

ground and at elevations exceeding 3300 feet.†

All wires,conductors, and

cables(ft.)

Open supplyconductors, 0

V to22 kV‡

(ft.)

Open Supply Conductors Elevation Range: 3301 to 6300 ft.



50

kV

to

70

kV

ph

ase

- to

- gro

un

d

11

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

70

kV

to

84

kV

ph

ase

- to

- gro

un

d

13

8 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

84

kV

to

98

kV

ph

ase

- to

- gro

un

d

16

1 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

98

kV

to

14

0 k

V p

ha

se- t

o- g

rou

nd

23

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

14

0 k

V t

o 2

10

kV

ph

ase

- to

- gro

un

d

34

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

21

0 k

V t

o 3

18

kV

ph

ase

- to

- gro

un

d

50

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

50

kV

to

70

kV

ph

ase

- to

- gro

un

d

11

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

70

kV

to

84

kV

ph

ase

- to

- gro

un

d

13

8 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

84

kV

to

98

kV

ph

ase

- to

- gro

un

d

16

1 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

98

kV

to

14

0 k

V p

ha

se- t

o- g

rou

nd

23

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

14

0 k

V t

o 2

10

kV

ph

ase

- to

- gro

un

d

34

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

21

0 k

V t

o 3

18

kV

ph

ase

- to

- gro

un

d

50

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

50

kV

to

70

kV

ph

ase

- to

- gro

un

d

11

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

70

kV

to

84

kV

ph

ase

- to

- gro

un

d

13

8 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

84

kV

to

98

kV

ph

ase

- to

- gro

un

d

16

1 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

98

kV

to

14

0 k

V p

ha

se- t

o- g

rou

nd

23

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

14

0 k

V t

o 2

10

kV

ph

ase

- to

- gro

un

d

34

5 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

21

0 k

V t

o 3

18

kV

ph

ase

- to

- gro

un

d

50

0 k

V p

ha

se- t

o- p

ha

se (

Ft.

)

NESC Rule 234F1a(2017)

18.0 19.8 20.3 20.9 22.4 24.9 28.8 19.9 20.5 21.1 22.8 25.5 29.7 20.1 20.7 21.4 23.1 26.1 30.6

NESC Rule 234F1b(2017)

15.0 16.8 17.3 17.9 19.4 21.9 25.8 16.9 17.5 18.1 19.8 22.5 26.7 17.1 17.7 18.4 20.1 23.1 27.6

† The NESC (2017) doesnot provide this table. This table was created to indicateminimum clearance requirements for voltagesabove 50 kV line to ground and at elevationsexceeding 3300 feetabove sea level. The base valueswere taken from the NESC Rule 234F1 (2017), and calculated valueswere derived based on the NESC Rule 234G1 and 234G2 (2017) and rounded up to thenearest tenth of a foot.

‡ Doesnot apply to a neutral conductor meeting Rule 230E1.


Page 31of 34






NESC Rule 234I (2017)

Clearances of wires, conductors, and cables to rail cars

Where overhead wires, conductors, or cables run along railroad tracks, the clearance in any direction shall be not lessthan that shown in Figure 234-5. The values of V and H are as defined as follows:

V = vertical clearance from the wire, conductor, or cable above the top of the rail as specified in Rule 232 minus 6.1m. (20 ft.), the assumed height of the rail car

H = horizontal clearance from the wire, conductor, or cable to the nearest rail, which is equal to the required verticalclearance above the rail minus 4.6 m. (15 ft.) as computed by the lesser of the following:

1. Rules 232B1 and 232C12. Rule 232D

These clearances are computed for railroads handling standard rail cars as common carriers in interchange servicewith other railroads. Where wires, conductors, or cables run along mine, logging, and similar railways that handleonly cars smaller than standard freight cars, the value of H may be reduced by one-half the difference between thewidth of a standard rail car [3.3 m. (10 ft., 8 in.)] and the width of the narrower car.

Figure 6 (NESC 234-5) —Rail Car Clearances

NESC Rule 234J (2017)

Clearance of equipment mounted on supporting structures

1. Clearance to unguarded rigid live parts of equipment


Page 32of 34





The horizontal and vertical clearances of unguarded rigid live parts such as potheads, transformer bushings, surgearresters, and short lengths of supply conductors connected thereto, which are not subject to variation in sag, shallbe not less than those required by Rule 234C or 234D, as applicable.

2. Clearance to equipment cases

Equipment shall be mounted so that clearances are not less than that given by Rules 234J2a, 234J2b, and 234J2c.

a. Effectively grounded equipment cases may be located on or adjacent to buildings, bridges, or other structuresprovided that clearances for unguarded rigid live parts of such equipment, as specified in Rule 234J1, aremaintained.

b. Equipment cases that are not effectively grounded shall be located so that the clearances of Rule 234C or234D, as applicable, are maintained.

c. Equipment cases shall be located so as not to serve as a means of approach to unguarded rigid live parts byunqualified persons.

NOTE: Rule 234J is not subject to the loading conditions of Rule 234A.


Page 33of 34






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Deviation from this standard requires prior approval. Contact the standards engineering manager for approval processes and forms.Printed versions of this standard may be out of date. Please consult the online standards for the most recent version. This standard shall be used and duplicatedonly in support of PacifiCorp projects. ©2017 by PacifiCorp.

Documents

TC151ClearancesofWires,Conductors,Cables,andEquipmentfrom ......communication conductorsand cables;messengers; overheadshield/ surge-protection wires;effectively groundedguys; ungroundedpor-tionsofguysmeet-ingRules215C4,