If no portion of a structure or its supported facilities exceeds 18 m (60 ft) above ground or water level, the provision of the rule are not required, except as specified in Rule 261A1c, 261A2e, or 261A3d. Where a structure or its supported facilities exceeds 18 m (60 ft) above ground or water level, the structure and its supported facilities shall be designed to withstand the extreme wind load associated with the Base Wind Speed as specified by NESC Figure 250-2(b). The wind pressures calculated shall be applied to the entire structure and supported facilities without ice.
The following formula shall be used to calculate wind load.
Load in Newton = 0.613 • (Vm/s)
2 • kZ • GRF • I • Cd • A(m2)
Load in pounds = 0.00256 • (Vmi/h)
2 • kZ • GRF • I • Cd • A(ft2)
Table PSC 114.250-2 (Metric)
Velocity Pressure Exposure Coefficient, kZ
Gust Response Factor, GRF
- See PDF for table 
Table PSC 114.250-2 (English)
Velocity Pressure Exposure Coefficient, kZ
Gust Response Factor, GRF
- See PDF for table
Where:
h = height of the structure above ground or water level. For wind loads on wires attached to the structure, the height of the highest wire attachment above ground or water level may be used if less than the height of the structure. In unique terrain where the height of the wire above ground at mid-span may be substantially higher than at the attachment point, engineering judgment may be used to determine an appropriate value the height of the wire.
PSC 114.250 Note
Note 2: The height of all wire attachments should be based on the height of the highest attachment or total structure height. The formulas to determine kZÌGRF were based on this premise, not the height of each attachment.
The wind pressure parameters (kZ, V, and GRF) are based on open terrain with scattered obstructions (Exposure Category C as defined in ASCE 7-98). Exposure Category C is the basis of the NESC extreme wind criteria. Topographic features such as ridges, hills, and escarpments may increase the wind loads on site-specific structures. A topographic Factor, kzt, from ASCE7-98 may be used to account for these special cases.
PSC 114.250(2)
(2) Longitudinal capability. [Follows NESC 250D, p. 205] (Addition) Following NESC 250D, add the following paragraph E:
E. Longitudinal capability
Each supply line designed to operate at 300 kV phase to phase or above shall be constructed to limit the effects of a cascading-type failure to a line segment not exceeding 9.6 km (6 mi) to 16 km (10 mi) in length. Such construction requirement may be met by providing, at appropriate intervals, structures and associated facilities having full dead-end capability under the loading provisions of Rules 250 A, B, C and D. Consideration shall be given to factors such as structure type and material, length of line, distance between dead-end or heavy angle structures, and other basic design criteria in determining the length of such individual line segments. For lines supported by “flexible" structures designed with plastic, energy-absorbing capability in failure, this requirement may be met if such design and construction will provide equivalent limitation to longitudinal cascading.
PSC 114.250 History
History: CR 07-021: cr.
Register January 2008 No. 625, eff. 2-1-08;
CR 13-039: r. and recr.
Register June 2014 No. 702, eff. 7-1-14; cr. PSC 114.250 (title) under s.
13.92 (4) (b) 2., Stats., renum. (1) and (2) from PSC 114.250C and 114.250E under s.
13.92 (4) (b) 1., Stats.,
Register March 2015 No. 711;
CR 18-007: am. (1), Table PSC 114-250-2 (Metric), Table PSC 114.250-2 (English), (2) (intro.) Register February 2020 No. 770, eff. 3-1-20; correction in (1) (formula) made under s. 35.17, Stats., Register February 2020.
PSC 114.253
PSC 114.253
Load factors for structures, cross arms, support hardware, guys, foundations, and anchors. Table PSC 114.253-1 [NESC Table 253-1, p. 225] Load factors for structures
1, crossarms, support hardware, guys, foundations, and anchors to be used with the strength factors of Table 261-1 (Changes)
2For guys and anchors associated with structures supporting communications conductors and cables only, this factor may be reduced to 1.33. For guys associated with structures supporting supply conductors or supply conductors and communications conductors and cables, this factor may be reduced to 1.5.
9For guys associated with structures supporting only supply conductors or supply conductors and communications conductors and cables, this factor may be reduced to 2.00.
PSC 114.253(3)
(3)
The reference to Footnote 9 is added to the value located at Transverse loads, Wind for Grade C, At crossings.
PSC 114.253 History
History: CR 07-021: cr.
Register January 2008 No. 625, eff. 2-1-08;
CR 13-039: r. and recr.
Register June 2014 No. 702, eff. 7-1-14; cr. PSC 114.253 (title) under s.
13.92 (4) (b) 2., Stats., renum. (1) and (2) from PSC 114.253-1 under s.
13.92 (4) (b) 1., Stats.,
Register March 2015 No. 711; correction in PSC 114.253 (title) under s.
13.92 (4) (b) 2., Stats.,
Register June 2015 No. 714;
CR 18-007: am. (intro.), (2) (intro.), (footnote), cr. (3) Register February 2020 No. 770, eff. 3-1-20.
Part 3. Safety Rules for the Installation and
Maintenance of Underground Electric Supply
and Communication Lines
Section 30. Purpose, Scope, and Application of Rules
PSC 114.302
PSC 114.302
Application of rules. [NESC 302, p. 247] (Change) Change Rule 302 to read:
302. Application of Rules
The general requirements for application of these rules are contained in s.
PSC 114.005.
Section 31. General Requirements Applying to Underground Lines
PSC 114.310
PSC 114.310
Referenced sections. [NESC 310, p. 248] (Change) Change Rule 310 to read:
310. Referenced Sections
The Introduction (Section 1) as amended by s.
PSC 114.010, Definitions (Section 2) as amended by Section 2 of Chapter
PSC 114, List of Referenced Documents (Section 3), and Grounding Methods (Section 9) as amended by Section 9 of Chapter
PSC 114, shall apply to the requirements of Part 3.
PSC 114.317
PSC 114.317
Outdoor location of oil-insulated padmounted transformers near buildings. [Follows NESC 316, p. 250] (Addition) Following NESC 316, add the following section:
317. Outdoor location of oil-insulated padmounted transformers near buildings.
A. Noncombustible and Combustible Walls
For the purposes of this section, combustible walls are walls of Type No.V buildings as determined by Wisconsin Building Code (Construction Classification IBC Chapter
6). All other walls are considered to be non-combustible.
B. Noncombustible Walls
Padmounted oil-insulated transformers may be located directly next to noncombustible walls if the following clearances are maintained from doors, windows and other building openings.
1. Padmounted oil-insulated transformers shall not be located within a zone extending 6.1 m (20 ft) outward and 3.0 m (10 ft) to either side of a building door. See Figure PSC 114-317B1.
Figure PSC 114-317B1.
2. Padmounted oil-insulated transformers shall not be located within a zone extending 3.0 m (10 ft) outward and 3.0 m (10 ft) to either side of an air intake opening. Such transformers may be located within said zone beneath an air intake opening provided there is not less than 7.6 m (25 ft) diagonal separation between the transformer and said opening. See Figure PSC 114-317B2.
Figure PSC 114-317B2.
3.a. Padmounted oil-insulated transformers shall not be located within a zone extending 3.0 m (10 ft) outward and 0.9 m (3 ft) to either side of a building window or opening other than an air intake. See Figure PSC 114-317B3a.
PSC 114.317 Note
Exception: This does not apply to a glass block or fire window meeting the requirements of the Wisconsin Commercial Building Code (Fire Window IBC Chapter
7, Section 714.3).
Figure PSC 114-317B3a.
3.b. For second story windows, the transformer shall not be located less than 1.5 m (5 ft) from any part of the window. See Figure PSC 317B3b.
PSC 114.317 Note
Exception: This does not apply to a glass block or fire window meeting the requirements of the Wisconsin Commercial Building Code (Fire Window, IBC Chapter
7, Section 714.3).
Figure PSC 114-317 B3b.
C. Combustible Walls
1. Padmounted oil-insulated transformers in sizes up to and including 100 kVA shall be located according to the provisions set forth in Subsection B for noncombustible walls.
2. Padmounted oil-insulated transformers in sizes above 100 kVA shall be located a minimum of 3.0 m (10 ft) from the building wall in addition to the clearances from building doors, windows and other openings set forth for noncombustible walls.
D. Barriers
If the clearances specified in PSC 114.317 cannot be obtained, a fire-resistant barrier may be constructed in lieu of the required separation. The following methods of construction are acceptable:
1. Noncombustible Walls
The barrier shall extend to a projection line from the corner of the padmounted transformer to the furthest corner of the window, door or opening in question. The height of the barrier shall be 0.3 m (1 ft) above the top of the padmounted transformer. See Figure PSC 114-317D1.
Figure PSC 114-317D1.
2. Combustible Walls
The barrier shall extend 0.9 m (3 ft) beyond each side of the padmounted transformer. The height of the barrier shall be 0.3 m (1 ft) above the top of the transformer. See Figure PSC 114-317D2.
Figure PSC 114-317D2.
E. Fire Escapes
1. Padmounted oil-insulated transformers shall not be located within a zone extending 6.1 m (20 ft) outward and 3 m (10 ft) to either side of the point where a fire escape meets the ground. See Figure PSC 114-317E1.
2. Padmounted oil-insulated transformers located beneath fire escapes shall have a vertical clearance of not less than 3 m (10 ft) from the top of the transformer to the bottom of the fire escape. See Figure PSC 114-317E2.
Figure PSC 114-317E1
Figure PSC 114-317E2
Section 35. Direct-Buried Cable
PSC 114.350
PSC 114.350
General. [NESC 350F, p. 263] (Change) Change paragraph F to read:
F. All direct-buried jacketed supply cable meeting Rule 350B and all direct-buried communication cables shall be legibly marked as follows:
The appropriate identification symbol shown in Fig 350-1 shall be indented or embossed in the outermost cable jacket at a spacing of not more than 1m (40 in). The symbol may be separate or sequentially combined with other data, or symbols, or both, printed on the jacket. If the symbol is sequentially combined, it shall be separated as indicated in Fig 350-1. If optional supplemental striping is used, only supply cables or non-metallic duct containing or intended to contain supply cables may have three equally separated longitudinal red stripes.
This rule applies to cable installed on or after January 1, 1996.
PSC 114.350 Note
Exception 1: Cables with jackets that cannot be effectively marked in accordance with Rules 350F need not be marked.
PSC 114.350 Note
Exception 2: Unmarked cable from stock existing prior to 1 January 1996 may be used to repair unmarked direct-buried jacketed supply cables and communication cables.
PSC 114.350 History
History: CR 07-021: cr.
Register January 2008 No. 625, eff. 2-1-08;
CR 13-039: r. and recr.
Register June 2014 No. 702, eff. 7-1-14; PSC 114.350 renum. from PSC 114.350F under s.
13.92 (4) (b) 1., Stats.,
Register March 2015 No. 711;
CR 18-007: am. (intro.) Register February 2020 No. 770, eff. 3-1-20.
PSC 114.352
PSC 114.352
Installation. Table PSC 114.352-1 [NESC Table 352-1, p. 266] Supply cable, conductor, or duct burial depth (Change and Addition)
PSC 114.352(1)
(1) Change the present “Exception" after the table to “Exception 1".
PSC 114.352 Note
Exception 2: Installations of insulated secondary underground cables operating at less than 600 volts between conductors shall be permitted to be laid on the ground during winter months provided they are suitably protected.
PSC 114.352 Note
Note 2: Grounding and bonding conductors are covered by Rule 093.
