Change List for this Rule

 

General Order 95

 

Section V

 

Detailed Construction Requirements for Supply Lines
(Class H, L and T Circuits)


58.1    Enclosed Equipment (Transformers, Capacitors, Regulators, etc.) (For purposes of this rule, enclosed means encased such as with cases or tanks of equipment operated at greater than 750 volts.)

 

A.    Position on Pole

 

(1)    Multiple Units: Where more than one unit is installed on a pole, they shall be placed on the same side of the pole. Transformers installed on metal mounting brackets shall not extend beyond the vertical plane through the centerline of the pole.

 

(2)    Pole Top Extensions: Equipment shall not be supported on pole top extensions.

 

EXCEPTION:    Pole top extensions that conform with strength requirements for a whole pole (see Rule 49.1–A ) may be used to support equipment.

 

B.    Case and Lead Wire Clearances (See Tables 58–1 & 58–2 )

 

(1)    Unprotected Lead Wire Clearances: Unprotected vertical and lateral leads between line conductors and equipment shall comply with Rules 54.6 and 54.4–C6 ; and with the clearances specified in Table 1, Cases 8 and 9 ; and Table 2, Cases 15, 16 and 17 . Such lead wires may be installed in the working space but shall not be installed in the climbing space.

The clearance specified in
Table 1, Case 8, Columns D and E , need not apply to apparatus installed on poles consisting of single–pole structures or on crossarms attached thereto, provided that terminals and lead wires are not less than 6 inches from surface of pole instead of 3 inches specified in Table 1, Case 9, Columns D and E , and have as much as possible of the clearances specified in Table 1, Case 8, Columns D and E. No reduction of the clearances specified in Table 1, Case 8, Columns D and E is permitted for interconnection wiring of polyphase installations nor to any lead wire passing between pole and apparatus.

 

(2)    Cases above Ground: Cases of equipment supported on poles or structures shall be not less than 17 feet above the ground except that in areas which are not in any way accessible to vehicles, the clearance of cases above ground may be less than 17 feet provided all cases which are less than 8 feet above ground shall be effectively grounded.

 

(3)    From Hardware: Equipment cases, hangers, and other metal parts in contact therewith shall clear through bolts, arm braces of metal, and other hardware elements, by not less than 1.5 inches; except that such cases and hangers shall clear crossarm braces and crossarm through bolts by not less than 1 inch air–gap distance and 1.5 inch creepage distance.

The minimum clearance of 1.5 inches need not apply to through bolts in metallic contact with equipment cases or metal parts thereof nor to through bolts supporting heel arms, provided the portion of such through bolts extending into the climbing space is covered with non–conducting material as specified in
Rule 22.8 .

 

(4)    From Guys: Equipment cases and their hangers shall not be less than 4 inches from all portions of guys which are 6 inches or more from the surface of poles or crossarms at the guy attachments. Such cases and hangers shall not be less than 1.5 inches from all portions of guys which are within 6 inches of the surface of poles or crossarms at the guy attachment.

 

Note:    Revised September 18, 1967 by Decision No. 72984.

 

C.    Equipment Cutouts or Other Equipment Disconnecting Devices

Equipment cutouts, fuses, disconnects or switches shall be located so that they are readily accessible from climbing and working spaces. Such devices or their connecting leads shall not extend into the climbing space, but may extend into the working space.

The vertical clearance between equipment cutouts, fuses, disconnects or switches and unprotected conductors of other circuits below shall not be less than the clearances required between conductors as specified in
Table 2, Cases 8 to 13 .

The horizontal clearance between equipment cutouts, fuses, disconnects or switches and unprotected conductors of different phase or polarity shall not be less than the clearances specified in
Table 2, Case 17 .

The provisions of this rule shall not apply to partial underground distribution systems.

 

Note:    Revised January 19, 1994 by Resolution SU–25.

 

D.    Ungrounded Case Clearances from Line Conductors (See Table 58–2 )

 

E.    Grounded Case Clearances from Line Conductors (See Rule 54.4–G )

 

F.    Bonding

Cases of equipment may be bonded together but shall not be bonded to cutouts, metal pins or deadend hardware.

 

Note:    Revised January 19, 1994 by Resolution SU–25. (Formerly Rule 58.4) andJanuary 13, 2006 by Decision No. 05-01-030

 

Table 58–1    Unprotected Bus and Lead Wire Clearances

Case

Nature of Clearance

Clearances Required

750 Volts - 22.5 kV

22.5 kV & above

Above Ground

1

Single Pole Structure

22.5 Feet

27.0 Feet

2

Two or More Pole Structure

22.5 Feet (a)

27.0 Feet (a)

From Buildings - Horizontal

From Building Walls

3

With Windows, Fire Escapes, etc.

6.0 Feet (b)

6.0 Feet

4

Without Windows, Fire Escapes, etc.

1.0 Foot (c)

1.0 Foot

From Building - Vertical above

5

Walkable Surfaces

12.0 Feet

12.0 Feet

6

Non–Walkable Surfaces

8.0 Feet

8.0 Feet

 

Footnotes Modifying Clearances in Table 58–1

 

(a)    May be reduced to 20 feet provided such lead or bus wires are guarded by transformer platform flooring which extends not less than 1 foot horizontally outside the vertical planes of all such lead and bus wires.

 

(b)    May be reduced under special conditions: Supply conductors of 750 - 7,500v see Rule 54.4–H1 .

 

(c)    If less than 6 feet below a walkable surface must have 6 foot horizontal clearance until vertical clearance is obtained.

 

Insert 58.1

 

Note:    Table added January 19, 1994 by Resolution SU–25

 

Table 58–2    Ungrounded Cases from Line Conductors (a) (b)


Line Conductors

Comm.

0 - 750 Volts

750 - 7500 Volts

7500V - 22.5KV

22.5 kV & above

1

Vertical above Case

48 in.

3 in.(c)

12 in.(d)

18 in. (e)

24 in.

2

Vertical below Case

48 in.

10 in.(d)

12 in.(d)

18 in. (e)

24 in.

3

Horizontal from Case

N/A

6 in.

12 in.

18 in.

24 in.

 

Footnotes Modifying Clearances in Table 58–2

 

(a)    For grounded cases see Rule 54.4–G .

 

(b)    For clearances from connecting lead wires and cases, see Table 2, Case 17 .

 

(c)    For conductors supported by rack construction, this dimension shall be a minimum of 4 feet.

 

(d)    May be reduced to 3 inches radially from unenergized cases and hangers, provided no line conductor which is less than 12 inches horizontally from the case or hanger is less than 3 inches above the level of the top surface of the crossarm.

 

(e)    For transformers see Rule 54.4–D8 .

 

Note:    Table added January 19, 1994 by Resolution SU–25