DesNo72984 GO95 rule 58.3-B

a) Lead and bus wires: The clearances above ground specified in Table 1 are applicable to unprotected lead and bus wires of transformer installations except as modified by the following provisions.

Clearances above ground unprotected lead and bus wires of transformer installations may be less than 25 feet as specified in Table 1, Column E case 3 and 4, but shall not be less than 22 ½ feet except where a clearance of not less than 18 feet above ground is permitted by the provisions of Rule 54.4-A2b in which case the clearance above ground of such lead and bus wires shall be not less than 18 feet,

Clearances above ground of unprotected lead and bus wires of transformer installations may be less than 30 feet as specified in Table 1, Column F, Cases 3 and 4, but shall be not less than 27 feet.

Clearances above ground of unprotected lead and bus wires of transformer installations on structures of two or more poles may be less than 22 ½ feet or 27 feet as specified above, or less than 25 feet as specified in Table 1, Column F, Case 5 but shall not be less than 20 feet above ground, 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 on the structure.

b) Cases: cases of transformers supported on poles or structures shall not be 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 shall be effectively grounded.

2) From Buildings: Transformers on poles shall be so located that normally Unenergized parts clear the surfaces of buildings by not less than 3 feet horizontally or by not less than 8 feet vertically. Lead and bus wires carried as unprotected conductors shall have the clearances from buildings as specified in Table 1, Cases 6 and 7.

In situations where foregoing clearances of cases and lead bus wires from walls of buildings (not windows, fire escapes, etc.) are impracticable to obtain, such as the location of transformers on poles in alleys, these clearances will not be held applicable provided wood barriers authorized by this Commission are used.

3) Cases from conductor levels above and below: Transformers shall be so installed that normally Unenergized metal parts clear unprotected conductors, except the transformer connecting leads by distances specified in the following provisions:

a) From 0-750 volt conductors below: The vertical clearance of transformer cases and hangers from the level of 0-750 volt conductors below (whether such conductors are supported on crossarms or racks) shall not be less than 10 inches except for certain conductors as provided in Rule 58.3-B4.

b) From 0-750 volt conductors above: The vertical clearance of Unenergized metal parts of transformers from 0-750 volt conductors supported on crossarms above shall be not less than 3 inches or, in lieu of such vertical clearance, the Unenergized parts of transformers shall not be less than 6 inches horizontally from such conductors. The vertical clearance of unenergized metal parts of transformers from 0-750 volt conductors supported on racks above shall be not less than 4 feet.

c) From 750-7500 volt conductors below: The vertical clearance of Unenergized metal parts of transformers from the level of 750-7500 volt conductors below shall be not less than 12 inches.

d) From 750-7500 volt conductors above: The clearance between Unenergized metal parts of transformers and 750-7500 volt conductors above or alongside shall be not less than 12 inches vertically or 12 inches horizontally, except that conductors of the circuit to which the transformer is connected may be less than the 12-inch vertical clearance from such Unenergized parts but shall be not less than 6 inches vertically from the transformer case and not less than 3 inches radially from the hanger provided no line conductor which is less than 12 inches horizontally from the case or hanger is less than 3 inches (Table 1 Case 9) above the level of the top surface of the crossarm.

e) From 7500-22,500 Volt conductor Above: The clearance between unergized metal parts of transformers and 7500-22,500 volt conductors above shall be not less than 18 inches vertically or 18 inches horizontally except that the vertical clearance shall be not less than 30 inches from a conductor at the top of pole as in Rule 54.4-D8b.

4) Transformer Cases from Certain Conductors Less than 10 inches below the cases

a) Transformer Leads on Heel Arms: Heel arms shall not used to support lead wires or taps except where necessary to clear the lower voltage transformer leads from the transformer case or other conductors.

b) Line conductors less than 10 inches below cases: Where a transformer case is unusually long, a crossarm supporting line conductors of 0-750 volts may be used as a heel arm or such conductors on an arm may be less than 10 inches below the transformer case or the hangers) provided all of the following conditions are met:

No more than a single transformer with lower voltage of 0-750 volts is supported on the pole at the same level;

The vertical clearances between conductors on the hanger arm and such line arm below shall not be less than as specified in Table 2, Cases 9 to 13;

It is not practicable to obtain the clearance of at least 10 inches specified in Rule 58.3-B3;

Such 0-750 volt conductors clear the transformer case by not less than 15 inches horizontally;

Service drops are not run from the crossarm supporting 0-750 volts conductors at that location; and

The vertical clearance of 0-750 volt conductors below the lowest point of the transformer primary leads is not less than

18 inches for primary leads of 750-7500 volts,
24 inches for primary leads of 7500-20,000 volts,
36 inches for primary leads of 20,000-35,000 volts.

6) From Guys: Transformer cases and hangers shall be not less than 4 inches from all portions of guys which are 6 inches or more from the surface of poles or crossams at the guy attachment. Transformer cases and hangers shall be not less than 1 ½ inches from all portions of guys which are within 6 inches of the surface of poles or crossarms at the guy attachments.

c) From 750-7500 volt conductors below: The vertical clearance of Unenergized metal parts of transformers from the level of 750-7500 volt conductors below shall be not less than 12 inches.

4) Transformer Cases from Certain Conductors Less than 10 inches below the cases

18 inches for primary leads of 750-7500 volts,
24 inches for primary leads of 7500-20,000 volts,
36 inches for primary leads of 20,000-35,000 volts.

5) From Hardware: Transformer cases, hangers, and other metal parts in contact therewith shall clear through bolts, arm braces and other hardware by not less than 1 ½ inches; except that transformer cases and hangers shall clear crossarm braces and crossarm through bolts by not less than 1-inch air-gap distances and 1 ½ –inch creepage distance.

The minimum clearance of 1 ½ inches need not apply to through bolts in metallic contact with transformer 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 a suitable protective covering, and provided that such coverings are made of seasoned Douglas Fir and are installed in a workmanlike manner, or in the alternative, with a suitable nonconducting shield or covering having the insulation efficiency and mechanical strength of impregnated fiber 5/16 inches thick.

7) Treatment of lead wires: Vertical and lateral leads between line conductors and transformers shall comply with Rule 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. Where such leads enter cutouts or switches Rule 58.5-C shall also apply. Such lead wires may be installed in the climbing space.

The clearances specified in Table 1, Case 8, Column 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 possible of the clearance specified in Table 1, Case 8 Columns D and E, is permitted for interconnection wiring of polyphase installations nor to connection wiring of polyphase installations nor to any lead wire passing between pole apparatus.

All lead wires shall clear braces, bolts and other line hardware a distance of not less than 1 ½ inches.

2) From Buildings: Transformers on poles shall be so located that normally Unenergized parts clear the surfaces of buildings by not less than 3 feet horizontally or by not less than 8 feet vertically. Lead and bus wires carried as unprotected conductors shall have the clearances from buildings as specified in Table 1, Cases 6 and 7.

In situations where foregoing clearances of cases and lead bus wires from walls of buildings (not windows, fire escapes, etc.) are impracticable to obtain, such as the location of transformers on poles in alleys, these clearances will not be held applicable provided wood barriers authorized by this Commission are used.

3) Cases from conductor levels above and below: Transformers shall be so installed that normally Unenergized metal parts clear unprotected conductors, except the transformer connecting leads by distances specified in the following provisions:

c) From 750-7500 volt conductors below: The vertical clearance of Unenergized metal parts of transformers from the level of 750-7500 volt conductors below shall be not less than 12 inches.

4) Transformer Cases from Certain Conductors Less than 10 inches below the cases

18 inches for primary leads of 750-7500 volts,
24 inches for primary leads of 7500-20,000 volts,
36 inches for primary leads of 20,000-35,000 volts.

5) From Hardware: Transformer cases, hangers, and other metal parts in contact therewith shall clear through bolts, arm braces and other hardware by not less than 1 ½ inches; except that transformer cases and hangers shall clear crossarm braces and crossarm through bolts by not less than 1-inch air-gap distances and 1 ½ –inch creepage distance.

The minimum clearance of 1 ½ inches need not apply to through bolts in metallic contact with transformer 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 a suitable protective covering, and provided that such coverings are made of seasoned Douglas Fir and are installed in a workmanlike manner, or in the alternative, with a suitable nonconducting shield or covering having the insulation efficiency and mechanical strength of impregnated fiber 5/16 inches thick.

7) Vertical and lateral leads between line conductors and transformers shall comply with Rule 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. Where such leads enter cutouts or switches Rule 58.5-C shall also apply. Such lead wires may be installed in the climbing space.

The clearances specified in Table 1, Cases 8, Column 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, Cases 9, Column D and E, and have as much possible of the clearance specified in Table 1, Cases 8, Column D and E, is permitted for interconnection wiring of polyphase installations nor to connection wiring of polyphase installations nor to any lead wire passing between pole apparatus.

All lead wires shall clear braces, bolts and other line hardware a distance of not less than 1 ½ inches.