Safety Rules for Underground Lines PDF 2017

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2016

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Part 3 of this code provides safety rules for installing and maintaining underground electric supply and communication lines. It covers the scope, application of rules, installation and maintenance procedures, accessibility, inspection, grounding of circuits and equipment and communication protective requirements. The rules apply to underground cables and equipment, structural arrangements, and extensions into buildings.

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300 Part 3: Safety Rules for Underground Lines 302 Part 3. Safety Rules for the Installation and Maintenance of Underground Electric Supply and Communication Lines...

300 Part 3: Safety Rules for Underground Lines 302 Part 3. Safety Rules for the Installation and Maintenance of Underground Electric Supply and Communication Lines Section 30. Purpose, scope, and application of rules 300. Purpose The purpose of Part 3 of this Code is the practical safeguarding of persons during the installation, operation, or maintenance of underground or buried supply and communication cables and associated equipment. 301. Scope Part 3 of this Code covers supply and communication cables and equipment in underground or buried systems. The rules cover the associated structural arrangements and the extension of such systems into buildings. It also covers the cables and equipment employed primarily for the utilization of electric power when such cables and equipment are used by the utility in the exercise of its function as a utility. They do not cover installations in electric supply stations. 302. Application of rules The general requirements for application of these rules are contained in Rule 13. While it is common practice to use the terms duct and conduit interchangeably, in Part 3 they have distinct definitions. Duct is a single enclosed raceway for conductors or cable; conduit is a structure containing one or more ducts; and conduit system is the combination of duct, conduit, conduits, manholes, handholes, and/or vaults joined to form an integrated whole. 247 Copyright © 2016 IEEE. All rights reserved. 310 Part 3: Safety Rules for Underground Lines 313A5b Section 31. General requirements applying to underground lines 310. Referenced sections The Introduction (Section 1), Definitions (Section 2), References (Section 3), and Grounding methods (Section 9) of this Code shall apply to the requirements of Part 3. 311. Installation and maintenance A. Persons responsible for underground facilities shall be able to indicate the location of their facilities. B. Reasonable advance notice should be given to owners or operators of other proximate facilities that may be adversely affected by new construction or changes in existing facilities. C. For emergency installations, supply and communication cables may be laid directly on grade if they are guarded or otherwise located so that they do not unduly obstruct pedestrian or vehicular traffic and are appropriately marked. Supply cables operating above 600 V shall meet either Rule 230C or 350B. NOTE: See Rules 014A2 and 230A2d. 312. Accessibility All parts that must be examined or adjusted during operation shall be arranged so as to be accessible to authorized persons by the provision of adequate working spaces, working facilities, and clearances. 313. Inspection and tests of lines and equipment A. When in service 1. Initial compliance with safety rules Lines and equipment shall comply with these safety rules upon being placed in service. 2. Inspection Accessible lines and equipment shall be inspected by the responsible party at such intervals as experience has shown to be necessary. 3. Tests When considered necessary, lines and equipment shall be subjected to practical tests to determine required maintenance. 4. Inspection records Any conditions or defects affecting compliance with this Code revealed by inspection or tests, if not promptly corrected, shall be recorded; such records shall be maintained until the conditions or defects are corrected. 5. Corrections a. Lines and equipment with recorded conditions or defects that would reasonably be expected to endanger human life or property shall be promptly corrected, disconnected, or isolated. b. Other conditions or defects shall be designated for correction. 248 Copyright © 2016 IEEE. All rights reserved. 313B Part 3: Safety Rules for Underground Lines 315A3 B. When out of service 1. Lines infrequently used Lines and equipment infrequently used shall be inspected or tested as necessary before being placed into service. 2. Lines temporarily out of service Lines and equipment temporarily out of service shall be maintained in a safe condition. 3. Lines permanently abandoned Lines and equipment permanently abandoned shall be removed or maintained in a safe condition. 314. Grounding of circuits and equipment A. Methods The methods to be used for grounding of circuits and equipment are given in Section 9. B. Conductive parts to be grounded Cable sheaths and shields (except conductor shields), equipment frames and cases (including pad- mounted devices), conductive lighting poles, and conductive handhole covers on non-conductive lighting poles shall be effectively grounded. Conductive-material ducts and riser guards that enclose electric supply lines or are exposed to contact with open supply conductors shall be effectively grounded. EXCEPTION: This rule does not apply to parts that are 2.45 m (8 ft) or more above readily accessible surfaces or are otherwise isolated or guarded. C. Circuits 1. Neutrals Primary neutrals, secondary and service neutrals, and common neutrals exposed to personnel contact shall be effectively grounded. EXCEPTION: Circuits designed for ground-fault detection and impedance current-limiting devices. 2. Other conductors Conductors, other than neutral conductors, that are intentionally grounded, shall be effectively grounded where exposed to personnel contact. 3. Surge arresters Surge arresters shall be effectively grounded. 4. Use of earth as part of circuit a. Supply circuits shall not be designed to use the earth normally as the sole conductor for any part of the circuit. b. Monopolar operation of a bipolar HVDC system is permissible for emergencies and lim- ited periods for maintenance. 315. Communications protective requirements A. Where required Where communications apparatus is handled by other than qualified persons, it shall be protected by one or more of the means listed in Rule 315B if such apparatus is permanently connected to lines subject to any of the following: 1. Lightning 2. Contact with supply conductors with voltages exceeding 300 V 3. Transient rise in ground potential exceeding 300 V 249 Copyright © 2016 IEEE. All rights reserved. 315A4 Part 3: Safety Rules for Underground Lines 316 4. Steady-state induced voltage of a level that may cause personal injury NOTE: When communication cables will be in the vicinity of supply stations where large ground currents may flow, the effect of these currents on communication circuits should be evaluated. B. Means of protection Where communications apparatus is required to be protected under Rule 315A, protective means adequate to withstand the voltage expected to be impressed shall be provided by insulation, protected where necessary by surge arresters. Severe conditions may require the use of additional devices such as auxiliary arresters, drainage coils, neutralizing transformers, or isolating devices. 316. Induced voltage Rules covering supply-line influence and communication-line susceptiveness have not been detailed in this Code. Cooperative procedures are recommended to minimize steady-state voltages induced from proximate facilities. Therefore, reasonable advance notice should be given to owners or operators of other known proximate facilities that may be adversely affected by new construction or changes in existing facilities. 250 Copyright © 2016 IEEE. All rights reserved. 320 Part 3: Safety Rules for Underground Lines 320A5b Section 32. Underground conduit systems NOTE: For supply and communication cables installed in ducts that are not part of a conduit system, see Rule 350G. 320. Location A. Routing 1. General a. Conduit systems should be subject to the least disturbance practical. Conduit systems extending parallel to other subsurface structures should not be located directly over or under other subsurface structures. If this is not practical, the rule on separation, as stated in Rule 320B, should be followed. b. Conduit alignment should be such that there are no protrusions that would be harmful to the cable. c. Where bends are required, the bending radius shall be sufficiently large to limit the likeli- hood of damage to cable being installed in the conduit. 2. Natural hazards Routes through unstable soils such as mud, shifting soil, etc., or through highly corrosive soils, should be avoided. If construction is required in these soils, the conduit should be constructed in such a manner as to minimize movement or corrosion or both. 3. Highways and streets Where conduit must be installed longitudinally under the roadway, it should be installed in the shoulder. If this is not practical, the conduit should be installed within the limits of one lane of traffic. 4. Bridges and tunnels The conduit system shall be located so as to limit the likelihood of damage by traffic. It should be located to provide safe access for inspection or maintenance of both the structure and the conduit system. 5. Railroad tracks a. The top of the conduit system should be located not less than 900 mm (36 in) below the top of the rails of a street railway or 1.27 m (50 in) below the top of the rails of a railroad. Where unusual conditions exist or where proposed construction would interfere with existing installations, a greater depth than specified above may be required. EXCEPTION: Where this is impractical, or for other reasons, this separation may be reduced by agreement between the parties concerned. In no case, however, shall the top of the conduit or any conduit protection extend higher than the bottom of the ballast section that is subject to working or cleaning. b. Where practical, manholes, handholes, and vaults should be placed where they are not under the trackbed. 251 Copyright © 2016 IEEE. All rights reserved. 320A6 Part 3: Safety Rules for Underground Lines 320B6 6. Water Conduit installed under water should be routed, installed, or both so that it will be protected from erosion by tidal action or currents. The conduit should not be located where ships normally anchor. B. Separation from other underground installations 1. General The radial separation between a conduit system and other underground structures should be as large as necessary to permit maintenance of either the conduit system or other underground structures while limiting the likelihood of damage to the other. These separations should be determined by the parties involved. EXCEPTION: When conduit crosses a manhole, vault, or subway tunnel roof, it may be supported directly on the roof with the concurrence of all parties involved. 2. Separations between supply and communication conduit systems Conduit systems to be occupied by communication conductors shall be separated from conduit systems to be used for supply systems by not less than a. 75 mm (3 in) of concrete b. 100 mm (4 in) of masonry c. 300 mm (12 in) of well-tamped earth EXCEPTION: Lesser separations may be used where the parties concur. 3. Sewers, sanitary and storm a. If conditions require a conduit to be installed parallel to and directly over a sanitary or storm sewer, it may be done provided both parties are in agreement as to the method. b. Where a conduit run crosses a sewer, it shall be designed to have suitable support on each side of the sewer to limit the likelihood of transferring any direct load onto the sewer. 4. Water lines Conduit should be installed as far as is practical from a water main in order to protect it from being undermined if the main breaks. Conduit that crosses over a water main shall be designed to have suitable support on each side as required to limit the likelihood of transferring any direct loads onto the main. 5. Gas and other lines that transport flammable material Radial separation of conduit from gas and other lines that transport flammable material shall be not less than 300 mm (12 in) as measured from the nearest duct in the conduit and should have sufficient separation from gas and other lines that transport flammable material to permit the use of pipe maintenance equipment. Conduit shall not enter the same manhole, handhole, or vault with gas or other lines that transport flammable material. EXCEPTION: For conduit containing communication cables or supply cables operating at not more than 600 V between conductors, the radial separation may be less than required by Rule 320B5 provided supplemental mechanical protection, if needed, is used to limit the likelihood of detrimental heat transfer to gas and other lines that transport flammable material due to a cable fault. Agreement to the reduced separation by all utilities involved is required. NOTE: For appropriate separations between grounds of supply systems and pipelines used for the transmission of flammable liquids or gases operating at high pressure [1030 kPa (150 lb/in2) or greater] see Rule 095B2. 6. Steam or cryogenic lines Conduit should be installed with sufficient separation from steam or cryogenic lines to limit the likelihood of thermal damage to the cable. Where it is not practical to provide adequate separation, a suitable thermal barrier shall be placed between the two facilities. 252 Copyright © 2016 IEEE. All rights reserved. 321 Part 3: Safety Rules for Underground Lines 322B5c 321. Excavation and backfill A. Trench The bottom of the trench should be undisturbed, tamped, or relatively smooth earth. Where the excavation is in rock, the conduit should be laid on a protective layer of clean tamped backfill. B. Quality of backfill All backfill should be free of materials that may damage the conduit system. Backfill material should be adequately compacted to limit settling under the expected surface usage. 322. Conduit, ducts, and joints A. General 1. Duct material shall be corrosion-resistant and suitable for the intended environment. 2. Duct materials, the construction of the conduit, or both shall be designed so that a cable fault in one duct would not damage the conduit to such an extent that it would cause damage to cables in adjacent ducts. 3. The conduit shall be designed to withstand external forces to which it may be subjected by the surface loadings set forth in Rule 323A, except that impact loading may be reduced one third for each 300 mm (12 in) of cover so no impact loading need be considered when cover is 900 mm (3 ft) or more. 4. The internal surface of the duct shall be free of sharp edges or burrs, which could damage supply cable. B. Installation 1. Restraint Conduit, including terminations and bends, should be suitably restrained by backfill, concrete envelope, anchors, or other means to maintain its design position under stress of installation procedures, cable pulling operations, and other conditions such as settling and hydraulic or frost uplift. 2. Joints Ducts shall be joined in a manner so as to limit solid matter from entering the conduit line. Joints shall form a sufficiently continuous smooth interior surface between joining duct sections so that supply cable will not be damaged when pulled past the joint. 3. Externally coated pipe When conditions are such that externally coated pipe is required, the coating shall be corrosion resistant and should be inspected, tested, or both, to see that the coating is continuous and intact prior to backfill. Precautions shall be taken to prevent damage to the coating when backfilling. 4. Building walls, floors, or roofs The portion of conduit installed through an exterior building wall, floor, or roof shall have seals inside the conduit and external seals on the outside surface of the conduit at the point of entry to the building intended to limit the likelihood of the entrance of gas into the building. The use of seals may be supplemented by gas-venting devices in order to minimize building up of positive gas pressures in the conduit. 5. Bridges a. Conduit installed in bridges shall include the capability to allow for expansion and con- traction of the bridge. b. Conduits passing through a bridge abutment should be installed so as to avoid or resist any shear due to soil settlement. c. Conduit of conductive material installed on bridges shall be effectively grounded. 253 Copyright © 2016 IEEE. All rights reserved. 322B6 Part 3: Safety Rules for Underground Lines 323C2 6. In vicinity of manholes Conduit should be installed on compacted soil or otherwise supported when entering a manhole to limit the likelihood of detrimental shear stress on the conduit at the point of manhole entrance. 323. Manholes, handholes, and vaults A. Strength Manholes, handholes, and vaults shall be designed to sustain all expected loads that may be imposed upon the structure. The horizontal design loads, vertical design loads, or both shall consist of dead load, live load, equipment load, impact, load due to water table, frost, and any other load expected to be imposed upon the structure, to occur adjacent to the structure, or both. The structure shall sustain the combination of vertical and lateral loading that produces the maximum shear and bending moments in the structure. 1. In roadway areas, the live load shall consist of the weight of a moving tractor-semitrailer truck illustrated in Figure 323-1. The vehicle wheel load shall be considered applied to an area as indicated in Figure 323-2. In the case of multilane pavements, the structure shall sustain the combination of loadings that results in vertical and lateral structure loadings that produce the maximum shear and bending moments in the structure. NOTE: Loads imposed by equipment used in road construction may exceed loads to which the completed road may be subjected. 2. In designing structures not subject to vehicular loading, the design live load shall be not less than 14.5 kPa (300 lb/ft2). 3. Live loads shall be increased by 30% for impact. 4. When hydraulic, frost, or other uplift will be encountered, the structure shall either be of suffi- cient weight or so restrained as to withstand this force. The weight of equipment installed in the structure is not to be considered as part of the structure weight. 5. Where pulling iron facilities are furnished, they should be installed to withstand twice the expected load to be applied to the pulling iron. B. Dimensions Manholes shall meet the following requirements: A clear working space sufficient for performing the necessary work shall be maintained. The horizontal dimensions of the clear working space shall be not less than 900 mm (3 ft). The vertical dimensions shall be not less than 1.83 m (6 ft) except in manholes where the opening is within 300 mm (1 ft), horizontally, of the adjacent interior side wall of the manhole. EXCEPTION 1: Where one boundary of the working space is an unoccupied wall and the opposite boundary consists of cables only, the horizontal working space between these boundaries may be reduced to 750 mm (30 in). EXCEPTION 2: In manholes containing only communication cables, equipment, or both, one horizontal dimension of the working space may be reduced to not less than 600 mm (2 ft), provided the other horizontal dimension is increased so that the sum of the two dimensions is at least 1.83 m (6 ft). C. Manhole access 1. Round access openings in a manhole containing supply cables shall be not less than 650 mm (26 in) in diameter. Round access openings in any manhole containing communication cables only, or manholes containing supply cables and having a fixed ladder that does not obstruct the opening, shall be not less than 600 mm (24 in) in diameter. Rectangular access openings should have dimensions not less than 650 mm  560 mm (26 in  22 in). 2. Openings shall be free of protrusions that will injure personnel or prevent quick egress. 254 Copyright © 2016 IEEE. All rights reserved. 323C3 Part 3: Safety Rules for Underground Lines 323F 3. Manhole openings shall be located so that safe access can be provided. When in the highway, they should be located outside of the paved roadway when practical. They should be located outside the area of street intersections and crosswalks whenever practical to reduce the traffic hazards to the workers at these locations. 4. Personnel access openings should be located so that they are not directly over the cable or equipment. Where this is not practical, they can be located over the cable if one of the follow- ing is provided: a. A conspicuous safety sign NOTE: ANSI Z535.1-2011, ANSI Z535.2-2011, ANSI Z535.3-2011, and ANSI Z535.4-2011 contain information regarding safety signs. b. A protective barrier over the cable c. A fixed ladder 5. Any manhole greater than 1.25 m (4 ft) in depth shall be designed so it can be entered by means of a ladder or other suitable climbing device. Equipment, cable, and hangers are not suitable climbing devices. D. Covers 1. Manholes and handholes, when not being worked in, shall be securely closed by covers of sufficient weight or proper design so they cannot be easily removed without tools. 2. Covers should be suitably designed or restrained so that they cannot fall into manholes or protrude into manholes sufficiently far to contact cable or equipment. 3. Strength of covers and their supporting structure shall be at least sufficient to sustain the applicable loads of Rule 323A. E. Vault and utility tunnel access 1. Access openings shall be located so that safe access can be provided. 2. Personnel access openings in vaults should be located so that they are not directly over or do not directly open into equipment or cable. In vaults, other types of openings (not personnel access) may be located over equipment to facilitate work on, replacement, or installation of equipment. 3. Where accessible to the public, access doors to utility tunnels and vaults shall be locked unless authorized person(s) are in attendance to restrict entry by unauthorized persons. Where vaults and utility tunnels contain exposed live parts, a prominent safety sign shall be posted where it is visible to persons before they enter. NOTE: ANSI Z535.1-2011, ANSI Z535.2-2011, ANSI Z535.3-2011, and ANSI Z535.4-2011 contain information regarding safety signs. 4. Such doors shall be designed so that a person on the inside may exit when the door is locked from the outside. EXCEPTION: This rule does not apply where the only means of locking is by padlock and the latching system is so arranged that the padlock can be closed on the latching system to prevent locking from the outside. 5. Clearance of energized parts and controls from penetrable ventilation openings Where ventilation openings in an aboveground vault are not protected with louvers or baffles that limit the opportunity for penetration from outside the vault by sticks or other objects, energized parts and controls that are not guarded shall be located so as to have a clearance from the outside of the ventilation opening not less than that required by the safety clearance zone of Rule 110A2 and Table 110-1. F. Ladder requirements Fixed ladders shall be corrosion-resistant. Portable ladders shall be used in accordance with Rule 420J. 255 Copyright © 2016 IEEE. All rights reserved. 323G Part 3: Safety Rules for Underground Lines F-323-1 NOTE: ANSI ASC A14.1-2007 [B8], ANSI ASC A14.2-2007 [B9], ANSI ASC A14.3-2008 [B10], and ANSI ASC A14.5-2007 [B11] contain information about ladders. G. Drainage Where drainage is into sewers, suitable traps or other means should be provided to limit the likelihood of sewer gas entering into manholes, vaults, or tunnels. H. Ventilation Adequate ventilation to open air shall be provided for manholes, vaults, and tunnels, having an opening into enclosed areas used by the public. Where such enclosures house transformers, switches, regulators, etc., the ventilating system shall be cleaned at necessary intervals. EXCEPTION: This does not apply to enclosed areas under water or in other locations where it is impractical to comply. I. Mechanical protection Supply cables and equipment should be installed or guarded in such a manner as to avoid damage by objects falling or being pushed through the grating. J. Identification Manhole and handhole covers should have an identifying mark that will indicate ownership or type of utility. Figure 323-1—Roadway vehicle load 256 Copyright © 2016 IEEE. All rights reserved. F-323-2 Part 3: Safety Rules for Underground Lines F-323-2 Figure 323-2—Wheel load area 257 Copyright © 2016 IEEE. All rights reserved. 330 Part 3: Safety Rules for Underground Lines 333B Section 33. Supply cable 330. General A. Cable should be capable of withstanding tests applied in accordance with an applicable standard issued by a recognized organization such as the American National Standards Institute (ANSI), the Association of Edison Illuminating Companies (AEIC), the Insulated Cable Engineers Association (ICEA), the National Electrical Manufacturers Association (NEMA), or the American Society for Testing and Materials (ASTM). B. The design and construction of conductors, insulation, sheath, jacket, and shielding shall include consideration of mechanical, thermal, environmental, and electrical stresses that are expected during installation and operation. C. Cable shall be designed and manufactured to retain specified dimensions and structural integrity during manufacture, reeling, storage, handling, and installation. D. Cable shall be designed and constructed in such a manner that each component is protected from harmful effects of other components. E. The conductor, insulation, and shielding shall be designed to withstand the effects of the expected magnitude and duration of fault current, except in the immediate vicinity of the fault. 331. Sheaths and jackets Sheaths, jackets, or both shall be provided when necessary to protect the insulation or shielding from moisture or other adverse environmental conditions. 332. Shielding A. General 1. Conductor shielding should, and insulation shielding shall, be provided as specified by an applicable document issued by a nationally recognized cable standardization organization. EXCEPTION: Shielding is not required for short jumpers that do not contact a grounded surface within enclosures or vaults, provided the jumpers are guarded or isolated. NOTE: Typical cable standardization organizations include: the AEIC, the ICEA, and the NEMA. 2. Insulation shielding may be sectionalized provided that each section is effectively grounded. B. Material 1. The shielding system may consist of semiconducting materials, nonmagnetic metal, or both. The shielding adjacent to the insulation shall be designed to remain in intimate contact with the insulation under all operating conditions. 2. Shielding material shall either be designed to resist excessive corrosion under the expected operating conditions or shall be protected. 333. Cable accessories and joints A. Cable accessories and joints shall be designed to withstand the mechanical, thermal, environmental, and electrical stresses expected during operation. B. Cable accessories and joints shall be designed and constructed in such a manner that each compo- nent of the cable and joint is protected from harmful effects of the other components. 258 Copyright © 2016 IEEE. All rights reserved. 333C Part 3: Safety Rules for Underground Lines 333D C. Cable accessories and joints shall be designed and constructed to maintain the structural integrity of the cables to which they are applied and to withstand the magnitude and duration of the fault current expected during operation, except in the immediate vicinity of the fault. D. For insulating joints, see Rule 332A2. 259 Copyright © 2016 IEEE. All rights reserved. 340 Part 3: Safety Rules for Underground Lines 341B2b(5) Section 34. Cable in underground structures 340. General A. Section 33 shall apply to supply cable in underground structures. B. On systems operating above 2 kV to ground, the design of the conductors or cables installed in non- metallic conduit should consider the need for an effectively grounded shield, a sheath, or both. 341. Installation A. General 1. Bending of the supply cable during handling, installation, and operation shall be controlled to avoid damage. 2. Pulling tensions and sidewall pressures on the supply cable should be limited to avoid damage. NOTE: Manufacturers’ recommendations may be used as a guide. 3. Ducts should be cleaned of foreign material that could damage the supply cable during pulling operations. 4. Cable lubricants shall not be detrimental to cable or conduit systems. 5. On slopes or vertical runs, consideration should be given to restraining cables to limit the like- lihood of downhill movement. 6. Supply cables shall not be installed in the same duct with communication cables unless all of the cables are operated and maintained by the same utility. 7. Communication cables may be installed together in the same duct provided all utilities involved are in agreement. B. Cable in manholes and vaults 1. Supports a. Cable supports shall be designed to withstand both live and static loading and should be compatible with the environment. b. Supports shall be provided to maintain specified clearance between cables. c. Horizontal runs of supply cables shall be supported at least 75 mm (3 in) above the floor, or shall be suitably protected. EXCEPTION: This rule does not apply to grounding or bonding conductors. d. The installation should allow cable movement without destructive concentration of stresses. The cable should remain on supports during operation. NOTE: Special protection may be necessary at the duct entrance. 2. Clearance a. Adequate working space shall be provided in accordance with Rule 323B. b. Between supply and communications facilities (cable, equipment, or both): (1) Where cable, equipment, or both are to be installed in a joint-use manhole or vault, it shall be done only with the concurrence of all parties concerned. (2) Supply and communication cables should be racked from separate walls. Crossings should be avoided. (3) Where supply and communication cables must be racked from the same wall, the sup- ply cables should be racked below the communication cables. (4) Supply and communications facilities shall be installed to permit access to either without moving the other. (5) Clearances shall be not less than those specified in Table 341-1. 260 Copyright © 2016 IEEE. All rights reserved. 341B3 Part 3: Safety Rules for Underground Lines 344A 3. Identification a. General (1) Cables shall be permanently identified by tags or otherwise at each manhole or other access opening of the conduit system. EXCEPTION: This requirement does not apply where the position of a cable, in conjunction with diagrams or maps supplied to workers, gives sufficient identification. (2) All identification shall be of a corrosion-resistant material suitable for the environment. (3) All identification shall be of such quality and located so as to be readable with auxil- iary lighting. b. Joint-use manholes and vaults Cables in a manhole or vault that are operated and maintained by different utilities shall be permanently identified by markings or tags denoting the utility name and type of cable use. Table 341-1—Clearance between supply and communications facilities in joint-use manholes and vaults Surface to surface Phase-to-phase supply voltage (mm) (in) 0 to 15 000 150 6 15 001 to 50 000 230 9 50 001 to 120 000 300 12 120 001 and above 600 24 EXCEPTION 1: These clearances do not apply to grounding conductors. EXCEPTION 2: These clearances may be reduced by mutual agreement between the parties concerned when suitable barriers or guards are installed. 342. Grounding and bonding A. Cable and joints with bare metallic shields, sheaths, or concentric neutrals that are exposed to per- sonnel contact shall be effectively grounded. B. Cable sheaths or shields that are connected to ground at a manhole shall be bonded or connected to a common ground. C. Bonding and grounding leads shall be of a corrosion-resistant material suitable for the environment or suitably protected. 343. Number not used in this edition. 344. Communication cables containing special supply circuits A. Special circuits operating at voltages in excess of 90 V ac or 150 V dc and used for supplying power solely to communications equipment may be included in communication cables under the following conditions: 261 Copyright © 2016 IEEE. All rights reserved. 344A1 Part 3: Safety Rules for Underground Lines 344A6 1. Such cables shall have a conductive sheath or shield that shall be effectively grounded. 2. All circuits in such cables shall be owned or operated by one party and shall be maintained only by qualified personnel. 3. Supply circuits included in such cables shall be terminated at points accessible only to qualified employees. 4. Communication circuits brought out of such cables, if they do not terminate in a repeater sta- tion or terminal office, shall be protected or arranged so that in event of a failure within the cable, the voltage on the communication circuit will not exceed 400 V to ground. 5. Terminal apparatus for the power supply shall be so arranged that live parts are inaccessible when such supply circuits are energized. 6. Such cables shall be identified, and the identification shall meet the pertinent requirements of Rule 341B3. EXCEPTION: The requirements of Rule 344A do not apply to communication circuits where the transmitted power does not exceed 150 W. 262 Copyright © 2016 IEEE. All rights reserved. 350 Part 3: Safety Rules for Underground Lines 350G Section 35. Direct-buried cable and cable in duct not part of a conduit system NOTE: The term duct or ducts as used in this section refers to duct(s) not part of a conduit system. 350. General A. Section 33 shall apply to direct-buried supply cable. B. Cables operating above 600 V to ground shall have a continuous metallic shield, sheath, or concen- tric neutral that is effectively grounded. EXCEPTION: At a splice or joint, the current path of the metallic shield, sheath, or neutral shall be made continuous but need not be concentric. C. Cables meeting Rule 350B of the same supply circuit may be buried with no deliberate separation. D. Cables of the same circuit operating below 600 V to ground and without an effectively grounded shield or sheath shall be placed in close proximity (no intentional separation) to each other. E. Communication cables containing special circuits supplying power solely to communications equip- ment shall comply with the requirements of Rules 344A1 through 344A6. 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 Figure 350-1 shall be indented or embossed in the outermost cable jacket at a spacing of not more than 1 m (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 Figure 350-1. This rule became effective for cable installed on or after 1 January 1996. RECOMMENDATION: If color coding is used as an additional method of identifying cable, the American Public Works Association Uniform Color Code for marking underground utility lines is recommended. EXCEPTION 1: Cables with jackets that cannot be effectively marked in accordance with Rule 350F need not be marked. 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. G. The rules in this section shall also apply to supply and communication cables installed in duct that is not part of a conduit system. RECOMMENDATION: If color coding is used as a method of identifying the duct, the American Public Works Association Uniform Color Code for marking underground utility lines is recommended. 263 Copyright © 2016 IEEE. All rights reserved. F-350-1 Part 3: Safety Rules for Underground Lines 351C1 Figure 350-1—Symbols for identification of buried cables 351. Location and routing A. General 1. Cables should be located so as to be subject to the least disturbance practical. When cables are to be installed parallel to and directly over or under other subsurface structures, the rules on separation in Rule 353 or 354, as applicable, shall be followed. 2. Cables should be installed in as straight and direct a line as practical. Where bends are required, the bending radius shall be sufficiently large to limit the likelihood of damage to the cable being installed. 3. Cable systems should be routed so as to allow safe access for construction, inspection, and maintenance. 4. The location of structures in the path of the projected cable route shall, as far as practical, be determined prior to trenching, plowing, or boring operation. B. Natural hazards Routes through unstable soil such as mud, shifting soils, corrosive soils, or other natural hazards should be avoided. If burying is required through areas with natural hazards, the cables shall be constructed and installed in such a manner as to protect them from damage. Such protective measures should be compatible with other installations in the area. C. Other conditions 1. Swimming pools (in-ground) Supply cable should not be installed within 1.5 m (5 ft) horizontally of a swimming pool or its auxiliary equipment. If 1.5 m (5 ft) is not attainable, supplemental mechanical protection shall be provided. NOTE: For aboveground pools, see Rule 351C2. 264 Copyright © 2016 IEEE. All rights reserved. 351C2 Part 3: Safety Rules for Underground Lines 352A2 2. Buildings and other structures Cable should not be installed directly under the foundations of buildings or other structures, such as aboveground swimming pools, tanks, toolsheds, etc. Where a cable must be installed under such a structure, the foundation shall be suitably supported to limit the likelihood of transfer of a detrimental load onto the cable. 3. Railroad tracks a. The installation of cable longitudinally under the ballast section for railroad tracks should be avoided. Where cable must be installed longitudinally under the ballast section of a railroad, it should be located at a depth of not less than 1.27 m (50 in) below the top of the rail. EXCEPTION: Where this is not practical, or for other reasons, this burial depth may be reduced by agreement between the parties concerned. NOTE: Where unusual conditions exist or where proposed construction would interfere with exist- ing installations, a greater depth than specified above would be required. b. Where a cable is installed under railroad tracks, the same burial depths indicated in Rule 320A5 shall apply. 4. Highways and streets The installation of cable longitudinally under traveled surfaces of highways and streets should be avoided. When cable must be installed longitudinally under the roadway, it should be installed in the shoulder or, if this is not practical, within the limits of one lane of traffic to the extent practical. 5. Water Cable or cable in duct installed under water should be routed, installed, or both, so that it will be protected from erosion by tidal action or currents. The cable or cable in duct should not be located where ships normally anchor. 6. Bridges Where permitted by the bridge owner, cables may be run in duct attached directly to the bridge. The duct shall be located so as to limit the likelihood of damage by traffic and be located to provide safe access for inspection or maintenance of both the bridge and the duct. 352. Installation A. Trenching 1. Direct-buried cable The bottom of the trench receiving direct-buried cable should be relatively smooth, undisturbed earth; well-tamped earth; or sand. When excavation is in rock or rocky soils, the cable should be laid on a protective layer of well-tamped backfill. Backfill within 100 mm (4 in) of the cable should be free of materials that may damage the cable. Backfill should be adequately compacted to limit settling under the expected surface usage. Machine compaction should not be used within 150 mm (6 in) of the cable. 2. Cable in duct For cable installed in a duct, the bottom of the trench should be in undisturbed, tamped, or relatively smooth earth. Where the excavation is in rock, the duct should be laid on a protective layer of clean tamped backfill. All backfill should be free of materials that may damage the duct. Backfill should be adequately compacted to limit settling under the expected surface usage. 265 Copyright © 2016 IEEE. All rights reserved. 352B Part 3: Safety Rules for Underground Lines T-352-1 B. Plowing 1. Plowing in of cable in soil containing rock or other solid material should be done in such a manner that the solid material will not damage the cable, either during the plowing operation or afterward. 2. The design of cable-plowing equipment and the plowing-in operation should be such that the cable will not be damaged by bending, side-wall pressure, or excessive cable tension. C. Boring Where a cable system is to be installed by boring and the soil and surface loading conditions are such that solid material in the region may damage the cable, the cable shall be adequately protected. D. Depth of burial 1. The distance between the top of a cable or duct and the surface under which it is installed (depth of burial) shall be sufficient to protect the cable or duct from damage imposed by expected surface usage. 2. Supply cable or duct shall have burial depths not less than the values indicated in Table 352-1. EXCEPTION: Where the burial depths required by Rule 352D2 cannot be met lesser depths than indicated in Table 352-1 may be used if supplemental mechanical protection is provided. The supplemental mechanical protection shall be sufficient to protect the cable or duct from damage imposed by expected surface usage. Where the cable is installed in duct, additional supplemental mechanical protection is not required if the duct is of sufficient strength to protect the cable from expected surface usage. NOTE 1: Cable depths at the time of installation may need to be adjusted to meet known grade changes. NOTE 2: In areas where frost conditions could damage cables or ducts, greater burial depths than indicated in Table 352-1 may be desirable. E. Supply cables shall not be installed in the same duct with communication cables unless all of the cables are operated and maintained by the same utility. F. Communication cables may be installed together in the same duct provided all utilities involved are in agreement. Table 352-1—Supply cable, conductor, or duct burial depth (See Rule 352D.) Depth of burial Voltage (phase-to-phase) (mm) (in) 0 to 600 600 24 601 to 50 000 750 30 50 001 and above 1070 42 EXCEPTION: Where conflicts with other underground facilities exist, street and area lighting cables operating at not more than 150 V to ground may be buried at a depth not less than 450 mm (18 in). 266 Copyright © 2016 IEEE. All rights reserved. 353 Part 3: Safety Rules for Underground Lines 354A3 353. Deliberate separations—Equal to or greater than 300 mm (12 in) from underground structures or other cables A. General 1. These rules apply to a radial separation of supply and communication cables or conductors from each other and from other underground structures such as sewers, water lines, gas and other lines that transport flammable material, building foundations, steam lines, etc., when sep- aration is equal to or greater than 300 mm (12 in). NOTE: For radial separation less than 300 mm (12 in) see Rule 354. 2. The radial separation should be adequate to permit access to and maintenance of either facility to limit damage to the other. B. Crossings 1. Where a cable crosses under another underground structure, the structure shall be suitably sup- ported to limit the likelihood of transferring of a detrimental load onto the cable system. 2. Where a cable crosses over another underground structure, the cable shall be suitably supported to limit the likelihood of transferring a detrimental load onto the structure. 3. Adequate support may be provided by installing the facilities with sufficient vertical separation. C. Parallel facilities Where a cable system is to be installed directly over and parallel to another underground structure (or another underground structure installed directly over and parallel to a cable), it may be done providing all parties are in agreement as to the method. Adequate vertical separation shall be maintained to permit access to and maintenance of either facility without damage to the other cables. D. Steam or cryogenic lines Cable should be installed with sufficient separation from steam or cryogenic lines to limit the likelihood of thermal damage to the cable. Where it is not practical to provide adequate separation, a suitable thermal barrier shall be placed between the two facilities. 354. Random separation—Separation less than 300 mm (12 in) from underground structures or other cables A. General 1. These rules apply to a radial separation of supply and communication cables or conductors from each other and from other underground structures when the radial separation between them will be less than 300 mm (12 in). 2. Radial separation of supply and communications cables or conductors from steam lines, gas, and other lines that transport flammable material shall be not less than 300 mm (12 in) and shall meet Rule 353. EXCEPTION: For supply cables operating at not more than 300 V between conductors, the radial separation may be less than required by Rule 354A2, provided supplemental mechanical protection is used to limit the likelihood of detrimental heat transfer to gas and other lines that transport flammable material due to a cable fault. For communication cables, the radial separation may be less than required by Rule 354A2. Agreement to the reduced separation by all utilities involved is required. 3. Supply circuits operating above 300 V to ground or 600 V between conductors shall be so constructed, operated, and maintained that when faulted, they shall be promptly de-energized initially or following subsequent protective device operation (phase-to-ground faults for effectively grounded circuits, phase-to-phase faults for ungrounded circuits). 267 Copyright © 2016 IEEE. All rights reserved. 354A4 Part 3: Safety Rules for Underground Lines 354D2a(1) 4. Communication cables and conductors, and supply cables and conductors buried in random separation may be treated as one system when considering separation from other underground structures or facilities. B. Supply cables or conductors The cables or conductors of a supply circuit and those of another supply circuit may be buried together at the same depth with no deliberate separation between facilities, provided all parties involved are in agreement. C. Communication cables or conductors The cables or conductors of a communication circuit and those of another communication circuit may be buried together and at the same depth with no deliberate separation between facilities, provided all parties involved are in agreement. D. Supply and communication cables or conductors Supply cables or conductors and communication cables or conductors may be buried together at the same depth, with no deliberate separation between facilities, provided all parties involved are in agreement and the applicable rules in 354D1 are met and either Rule 354D2, 354D3, or 354D4 is met. EXCEPTION: Entirely dielectric fiber-optic communication cables may be buried together at the same depth with no deliberate separation from supply cables or conductors provided all parties involved are in agreement and Rules 354D1a, b, c, and d are met. 1. General a. Grounded supply systems shall not be operated in excess of 22 000 V to ground. b. Ungrounded supply systems shall not be operated in excess of 5300 V phase to phase. c. Cables of an ungrounded supply system operating above 300 V shall be of effectively grounded concentric shield construction. Such cables shall be maintained in close proxim- ity to each other. d. Ungrounded supply circuits operating above 300 V between conductors and in random separation with communication conductors shall be equipped with a ground-fault indica- tion system. e. Communication cables and communication service wire having metallic conductors or metallic components shall have a continuous metallic shield under the outer jacket. EXCEPTION: This requirement does not apply to Rule 354C. f. Communications-protective devices shall be adequate for the voltage and currents expected to be impressed on them in the event of contact with the supply conductors. g. Adequate bonding shall be provided between the effectively grounded supply conductor or conductors and the communication cable shield or sheath at intervals that should not exceed 300 m (1000 ft). EXCEPTION: The bonding interval of Rule 354D1g may be increased for grounded supply conduc- tors and communications cables in buried locations where adherence would require opening a duct and/or removing the protective jacket only for the purpose of installing a bond, provided all parties are in agreement. h. In the vicinity of supply stations where large ground currents may flow, the effect of these currents on communication circuits should be evaluated before communication cables are placed in random separation with supply cables. 2. Grounded bare or semiconducting jacketed neutral supply cables a. A supply facility operating above 300 V to ground shall include a bare or semiconducting jacketed grounded conductor in continuous contact with the earth. This conductor, ade- quate for the expected magnitude and duration of the fault current that may be imposed, shall be one of the following: (1) A sheath, an insulation shield, or both 268 Copyright © 2016 IEEE. All rights reserved. 354D2a(2) Part 3: Safety Rules for Underground Lines 354E3 (2) Multiple concentric conductors closely spaced circumferentially (3) A separate conductor in contact with the earth and in close proximity to the cable, where such cable or cables also have a grounded sheath or shield not necessarily in contact with the earth. The sheath, shield, or both, as well as the separate conductor, shall be adequate for the expected magnitude and duration of the fault currents that may be imposed. EXCEPTION: Where buried cable passes through a short section of conduit such as under a roadway, the contact with earth of the grounded conductor can be omitted, provided the grounded conductor is continuous through the conduit. NOTE: This is applicable when a cable in nonmetallic duct is considered as a direct-buried cable installation and random separation is desired. b. The bare conductor or conductors in contact with the earth shall be of suitable corrosion- resistant material. The conductor covered by a semiconducting jacket shall be compatible with the jacketing compound. NOTE: Experience has shown that in many geographic areas, bare concentric copper neutral con- ductors experience severe corrosion. c. The radial resistivity of the semiconducting jacket shall be not more than 100   m and shall remain essentially stable in service. The radial resistivity of the jacket material is that value calculated from measurements on a unit length of cable, of the resistance between the concentric neutral and a surrounding conducting medium. Radial resistivity is equal to the resistance of a unit length times the surface area of the jacket divided by the average thickness of the jacket over the neutral conductors. All dimensions are to be expressed in meters. 3. Insulating jacketed effectively grounded neutral supply cables Each phase conductor of a multi-grounded supply system operating above 300 V to ground and having an overall insulating jacket shall have an effectively grounded copper concentric conductor meeting all of the following requirements: a. Adequate for the expected magnitude and duration of fault current that may be imposed b. Effectively grounded as required by Rule 314 except that the number of grounding electrodes shall be not less than eight in each 1.6 km (1 mile) of the random buried section, not including grounds at individual services EXCEPTION: The grounding interval of Rule 354D3b may be increased for grounded neutral supply cables with insulating jackets where adherence would require opening a duct and/or removing the protective jacket of the buried cable only for the purpose to install a ground connection. For such cases, the supply circuit shall be effectively grounded where the cable does become accessible. 4. Insulating jacketed grounded neutral supply cables in nonmetallic duct Insulating jacketed grounded neutral supply cables meeting the rules of 354D3, when installed in nonmetallic duct, may be random-laid with communication cables. E. Supply and communication cables or conductors and non-metallic water and sewer lines 1. Supply cables and conductors and non-metallic water and sewer lines may be buried together with no deliberate separation between facilities and at the same depth, provided all parties involved are in agreement. 2. Communication cables and conductors and non-metallic water and sewer lines may be buried together with no deliberate separation between facilities and at the same depth, provided all parties involved are in agreement. 3. Supply cables or conductors, communication cables or conductors, non-metallic water and sewer lines may be buried together with no deliberate separation between facilities and at the same depth, provided the applicable rules in Rule 354D are met and all parties involved are in agreement. 269 Copyright © 2016 IEEE. All rights reserved. 355 Part 3: Safety Rules for Underground Lines 355D 355. Additional rules for duct not part of a conduit system A. Duct material shall be corrosion-resistant and suitable for the intended environment. B. The internal surface of the duct shall be free of sharp edges or burrs, which could damage the supply or communication cable. C. Ducts shall be joined in a manner so as to limit solid matter from entering the duct line. Joints shall form a sufficiently continuous smooth interior surface between joining duct sections so that the supply or communication cable will not be damaged when pulled past the joint. D. The portion of duct installed through a an exterior building wall, floor, or roof shall have seals inside the duct and external seals on the outside surface of the duct at the point of entry into the building intended to limit the likelihood of the entrance of gas into the building. The use of seals may be supplemented by gas-venting devices in order to limit the buildup of positive gas pressures in the conduit. 270 Copyright © 2016 IEEE. All rights reserved. 360 Part 3: Safety Rules for Underground Lines 363B Section 36. Risers 360. General A. Mechanical protection for supply conductors or cables shall be provided as required by Rule 239D of this Code. This protection should extend at least 300 mm (1 ft) below ground level. B. Supply conductors or cable should rise vertically from the cable trench with only such deviation as necessary to permit a reasonable cable-bending radius. C. Exposed conductive ducts or guards containing supply conductors or cables shall be effectively grounded as required by Rule 314B. 361. Installation A. The installation should be designed so that water does not stand in riser pipes above the frost line. B. Conductors or cables shall be supported in a manner designed to limit the likelihood of damage to conductors, cables, or terminals. C. Where conductors or cables enter the riser pipe or elbow, they shall be installed in such a manner that shall minimize the possibility of damage due to relative movement of the cable and pipe. 362. Pole risers—Additional requirements A. Risers should be located on the pole in the safest available position with respect to climbing space and exposure to traffic damage. B. The number, size, and location of riser ducts or guards shall be limited to allow adequate access for climbing. 363. Pad-mounted installations A. Supply conductors or cables rising from the trench to transformers, switchgear, or other equipment mounted on pads shall be so placed and arranged that they will not bear on the edges of holes through the pad nor the edges of bends or other duct work below the pad. B. Cable entering pad-mounted equipment shall be maintained substantially at adequate depth for the voltage class until it becomes protected by being directly under the pad, unless other suitable mechanical protection is provided. 271 Copyright © 2016 IEEE. All rights reserved. 370 Part 3: Safety Rules for Underground Lines 374B Section 37. Supply cable terminations 370. General A. Cable terminations shall be designed and constructed to meet the requirements of Rule 333. B. Riser terminations not located within a vault, pad-mounted equipment, or similar enclosure shall be installed in a manner designed to ensure that the clearance specified in Parts 1 and 2 of this Code are maintained. C. A cable termination shall be designed to limit the likelihood of moisture penetration into the cable where such penetration is detrimental to the cable. D. Where clearances between parts at different potentials are reduced below those adequate for the voltage and BIL (basic impulse insulation level), suitable insulating barriers or fully insulated termi- nals shall be provided to meet the required equivalent clearances. 371. Support at terminations A. Cable terminations shall be installed in a manner designed to maintain their installed position. B. Where necessary, cable shall be supported or secured in a manner designed to limit the likelihood of the transfer of damaging mechanical stresses to the termination, equipment, or structure. 372. Identification Suitable circuit identification shall be provided for all terminations. EXCEPTION: This requirement does not apply where the position of the termination, in conjunction with diagrams or maps supplied to workers, gives sufficient identification. 373. Clearances in enclosures or vaults A. Adequate electrical clearances of supply terminations shall be maintained, both between conductors and between conductors and ground, consistent with the type of terminator used. B. Where exposed live parts are in an enclosure, clearances or insulating barriers adequate for the volt- ages and the design BIL shall be provided. C. Where a termination is in a vault, uninsulated live parts are permissible provided they are guarded or isolated. 374. Grounding A. All exposed conducting surfaces of the termination device, other than live parts and equipment to which it is attached, shall be effectively grounded, bonded, or both. B. Conductive structures supporting cable terminations shall be effectively grounded. EXCEPTION: Grounding, bonding, or both is not required where the above parts are isolated or guarded. 272 Copyright © 2016 IEEE. All rights reserved. 380 Part 3: Safety Rules for Underground Lines 381G2 Section 38. Equipment 380. General A. Equipment includes: 1. Buses, transformers, switches, etc., installed for the operation of the electric supply system 2. Repeaters, loading coils, etc., installed for the operation of the communications system 3. Auxiliary equipment, such as sump pumps, convenience outlets, etc., installed incidental to the presence of the supply or communications systems B. Where equipment is to be installed in a joint-use manhole, it shall be done with the concurrence of all parties concerned. C. Supporting structures, including racks, hangers, or pads and their foundations, shall be designed to sustain all loads and stresses expected to be imposed by the supported equipment including those stresses caused by its operation. D. Pad-mounted equipment, pedestals, and other aboveground enclosures, should be located not less than 1.2 m (4 ft) from fire hydrants. EXCEPTION 1: Where conditions do not permit a clearance of 1.2 m (4 ft), a clearance of not less than 900 mm (3 ft) is allowed. EXCEPTION 2: Clearances in Rule 380D may be reduced by agreement with the local fire authority and the equipment owner. 381. Design A. The expected thermal, chemical, mechanical, and environmental conditions at the location shall be considered in the design of all equipment and mountings. B. All equipment, including auxiliary devices, shall be designed to withstand the effects of normal, emergency, and fault conditions expected during operation. C. Switches shall be provided with clear indication of contact position, and the handles or activating devices clearly marked to indicate operating directions. D. Remotely controlled or automatic devices shall have local provisions to render remote or automatic controls inoperable if such operation may result in a hazard to the worker. E. Enclosures containing fuses and interrupter contacts shall be designed to withstand the effects of normal, emergency, and fault conditions expected during operation. F. When tools are to be used to connect or disconnect energized devices, space or barriers shall be designed to provide adequate clearance from ground or between phases. G. Pad-mounted and other aboveground equipment 1. Pad-mounted and other aboveground equipment shall have an enclosure that is either locked or otherwise secured against unauthorized entry. 2. Access to exposed live parts in excess of 600 V shall require two separate conscious acts. The first shall be the opening of a door or barrier that is locked or otherwise secured against unau- thorized entry as required by Rule 381G1. The second act shall be either the opening of a door or the removal of a barrier. A prominent and appropriate safety sign should be visible when the first door or barrier is opened or removed. NOTE: ANSI Z535.1-2011, ANSI Z535.2-2011, ANSI Z535.3-2011, and ANSI Z535.4-2011 contain information regarding safety signs. 273 Copyright © 2016 IEEE. All rights reserved. 382 Part 3: Safety Rules for Underground Lines 385 382. Location in underground structures A. Equipment shall not obstruct personnel access openings in manholes or vaults, nor shall it impede egress by persons working in the structures containing the equipment. B. Equipment shall not be installed closer than 200 mm (8 in) to the back of fixed ladders and shall not interfere with the proper use of such ladders. C. Equipment should be arranged in a manhole or vault to permit installation, operation, and mainte- nance of all items in such structures. D. Switching devices that have provision for manual or electrical operation shall be operable from a safe position. This may be accomplished by use of portable auxiliary devices, temporarily attached. E. Equipment should not interfere with drainage of the structure. F. Equipment shall not interfere with the ability to ventilate any structure or enclosure. 383. Installation A. Provisions for lifting, rolling to final position, and mounting shall be adequate for the weight of the device. B. Live parts shall be guarded or isolated to limit the likelihood of contact by persons in a normal posi- tion adjacent to the equipment. C. Operating levers, inspection facilities, and test facilities shall be visible and readily accessible when equipment is in final location without moving permanent connections. D. Live parts shall be isolated or protected from exposure to conducting liquids or other material expected to be present in the structure containing the equipment. E. Operating controls of supply equipment, readily accessible to unauthorized personnel, shall be secured by bolts, locks, or seals. 384. Grounding and bonding A. Cases and enclosures made of conductive material shall be effectively grounded or guarded. B. Guards constructed of conductive material shall be effectively grounded. C. Bonding should be provided between all aboveground metallic supply and communications enclosures that are separated by a distance of 1.8 m (6 ft) or less. For the purpose of this rule, pole grounds are not required to be bonded to the communication enclosure. NOTE: This rule does not prohibit bonding communication metallic enclosures to supply pole grounds, provided all affected parties are in agreement. 385. Identification Where transformers, regulators, or other similar equipment operate in multiple, tags, diagrams, or other suitable means shall be used to indicate that fact. 274 Copyright © 2016 IEEE. All rights reserved. 390 Part 3: Safety Rules for Underground Lines 391B3 Section 39. Installation in tunnels 390. General A. The installation of supply and communications facilities in tunnels shall meet the applicable require- ments contained elsewhere in Part 3 of this Code as supplemented or modified by this section. B. Where the space occupied by supply or communications facilities in a tunnel is accessible to other than qualified persons, or where supply conductors do not meet the requirements of Part 3 of this Code for cable systems, the installation shall be in accordance with the applicable requirements of Part 2 of this Code. C. All parties concerned must be in agreement with the design of the structure and designs proposed for installations within it. 391. Environment A. When the tunnel is accessible to the public or when workers must enter the structure to install, oper- ate, or maintain the facilities in it, the design shall provide a controlled safe environment including, where necessary, barriers, detectors, alarms, ventilation, pumps, and adequate safety devices for all facilities. Controlled safe environment shall include the following: 1. Design to avoid poisonous or suffocation atmosphere 2. Design to protect persons from pressurized lines, fire, explosion, and high temperatures 3. Design to avoid unsafe conditions due to induced voltages 4. Design to limit the likelihood of hazards due to flooding 5. Design to ensure egress; two directions for egress shall be provided for all points in tunnels 6. Working space, in accordance with Rule 323B, the boundary of which shall be not less than 600 mm (2 ft) from a vehicular operating space or from exposed moving parts of machinery 7. Safeguards designed to protect workers from hazards due to the operation of vehicles or other machinery in tunnels 8. Unobstructed walkways for workers in tunnels B. A condition of occupancy in multiple-use tunnels by supply and communications facilities shall be that the design and installation of all facilities is coordinated to provide a safe environment for the operation of supply facilities, communications facilities, or both. Safe environment for facilities shall include the following: 1. Means to protect equipment from harmful effects of humidity or temperature 2. Means to protect equipment from harmful effects of liquids or gases 3. Coordinated design and operation of corrosion-control systems 275 Copyright © 2016 IEEE. All rights reserved. Part 3: Safety Rules for Underground Lines 276 Copyright © 2016 IEEE. All rights reserved. 400 Part 4: Work Rules 402 Part 4. Work Rules for the Operation of Electric Supply and Communications Lines and Equipment Section 40. Purpose and scope 400. Purpose The purpose of Part 4 of this Code is to provide practical work rules as one of the means of safeguarding employees and the public from injury. It is not the intent of these rules to require unreasonable steps to comply; however, all reasonable steps shall be taken. 401. Scope Part 4 of this Code covers work rules to be followed in the installation, operation, and maintenance of electric supply and communications systems. 402. Referenced sections The Introduction (Section 1), Definitions (Section 2), References (Section 3), and Grounding methods (Section 9) of this Code shall apply to the requirements of Part 4. The standards listed in Section 3 (References) shall be used with Part 4 where applicable. 277 Copyright © 2016 IEEE. All rights reserved. 410 Part 4: Work Rules 410A3b Section 41. Supply and communications systems—Rules for employers 410. General requirements A. General 1. The employer shall inform each employee working on or in the vicinity of communications equipment or electric supply equipment and the associated lines, of the safety rules governing the employee’s conduct while so engaged. When deemed necessary, the employer shall provide a copy of such rules. 2. The employer shall provide training to all employees who work on or in the vicinity of exposed energized lines and parts. The training shall include applicable work rules required by this Part and other mandatory referenced standards or rules. The employer shall ensure that each employee has demonstrated proficiency in required tasks. The employer shall provide retraining for any employee who, as a result of routine observance of work practices, is not following work rules. 3. The employer shall ensure that an assessment is performed to determine potential exposure to an electric arc for employees who work on or near energized lines, parts, or equipment. If the assessment determines potential employee exposure, employees shall not wear any cloth- ing made from acetate, nylon, polyester, or polypropylene unless arc rated, and shall not wear an outer layer of clothing that could ignite and continue to burn when exposed to flames or the electric arc identified in the assessment. If the assessment determines a potential employee exposure greater than 2 cal/cm2 exists (see Neal, Bingham, and Doughty [B62]), the employer shall: a. Perform a detailed arc hazard analysis, or use Table 410-1, Table 410-2, or Table 410-3 to determine the effective arc rating of clothing to be worn by employees working on or near energized lines, parts, or equipment at voltages 50 V to 800 000 V. The arc hazard analysis shall include a calculation of the estimated arc energy based on the available fault current, the duration of the arc (cycles), and the distance from the arc to the employee. b. Require employees to cover the entire body with arc rated clothing and equipment having an effective arc rating not less than the anticipated level of arc energy. EXCEPTION 1: If the clothing required by this rule has the potential to create additional or greater hazards than the possible exposure to the heat energy of the electric arc, then clothing with an effective arc rating less than that required by the this rule may be worn. EXCEPTION 2: Arc-rated equipment is not necessary for the employee’s hands when the employee is wearing rubber insulating gloves with protectors. Heavy-duty leather work gloves with a weight of at least 407 gm/m2 (12 oz/yd2) may be worn if the estimated incident energy is no more than 14 cal/cm2. EXCEPTION 3: Arc-rated equipment is not necessary for the employee’s feet when the employee is wearing heavy-duty work shoes or boots. EXCEPTION 4: Arc-rated equipment is not necessary for the employee’s head or face when the employee is wearing head protection meeting 29 CFR 1910.135 [B66] if the estimated incident energy is less than OSHA 9 cal/cm2 for exposures involving single phase arcs in open air less than or 5 cal/cm2 for other exposures. Arc-rated equipment is necessary for the protection of the employee’s head and face and may consist of head protection meeting OSHA 29 CFR 1910.135 and a face shield with a minimum arc rating of 8 cal/cm2 if the estimated incident-energy exposure is greater than 9 cal/cm2 and less than 13 cal/cm2 for exposures involving single-phase arcs in open air or greater than 5 cal/cm2 and less than 9 cal/cm2 for other exposures. For exposures involving single phase arcs in open air, the arc rating for the employee’s head and face protection may be 4 cal/cm2 less than the estimated incident energy. 278 Copyright © 2016 IEEE. All rights reserved. 410A4 Part 4: Work Rules 410C2 EXCEPTION 5: For dc systems with voltages from 50 V to 250 V and 8000 A maximum fault current, in lieu of performing an arc hazard analysis, clothing with a minimum effective arc rating of 5 cal/cm2 shall be used (see Doan, “Arc Flash Calculations for Exposures to DC Systems”). NOTE 1: See Doan, “Arc Flash Calculations for Exposures to DC Systems” [B28]. NOTE 2: Assessments performed to determine potential exposure to an electric arc consider the affected employee’s assigned tasks and/or work activities. NOTE 3: Multiple layers of arc rated clothing (e.g., shirts, pants, and jackets) have been shown by testing to block more heat than a single layer. NOTE 4: Clothing includes normal garments such as shirts, pants, jackets, and coveralls, whether in single or multiple layers. NOTE 5: Engineering controls can be utilized to reduce arc energy levels and work practices can be utilized to reduce exposure levels. 4. Employers shall utilize positive procedures to secure compliance with these rules. Cases may arise where the strict enforcement of a particular rule could seriously impede the safe progress of the work; in such cases the employee in charge of the work should make a temporary modification to the particular rule so the work can be accomplished without increasing the hazard. 5. If a difference of opinion arises with respect to the application of these rules, the decision of the employer or the employer’s authorized agent shall be final. This decision shall not result in any employee performing work in a manner that is unduly hazardous to the employee or to other workers. 6. The employer shall provide training to all employees who work in the vicinity of antennas operating in the range of 3 kHz to 300 GHz to recognize and mitigate exposure to radio- frequency sources that exceed exposure levels set forth by the regulatory authority having jurisdiction. NOTE: See OSHA 29 CFR 1910.97, Subpart G [B65]; OSHA 29 CFR 1910.268, Subpart R [B67]; FCC Bulletin No. 65 [B30]; IEEE Std C95.1-2005 [B60]. B. Emergency and first aid procedures 1. Employees shall be informed of the procedures to be followed in case of emergencies and first aid including approved methods of resuscitation. Copies of such procedures should be accessi- ble where the number of employees and the nature of the work warrants. 2. Employees working on communications or electric supply equipment or lines shall be regularly instructed in methods of first aid and emergency procedures, if their duties warrant such training. C. Responsibility 1. A designated person shall be in charge of the operation of the equipment and lines and shall be responsible for their safe operation. 2. If more than one person is engaged in work on or in the vicinity of the same equipment or line, one person shall be designated as in charge of the work to be performed. Where there are separate work locations, one person may be designated at each location. 279 Copyright © 2016 IEEE. All rights reserved. T-410-1 Part 4: Work Rules T-410-1 Table 410-1—Clothing and clothing systems (cal/cm2) for voltages 50 V to 1000 V (ac)  (See Rule 410A3.) Nominal voltage range and cal/cm2 Equipment type 50 V to 250 V 251 V to 600 V 601 V to 1000 V Self-contained meters / cabinets 4 20  30  Pad-mounted transformers 4 4 6 CT meters and control wiring 4 4 6 Metal-clad switchgear / motor control centers 8 40  60  Pedestals / pull boxes / hand holes 4 8 12  Open air (includes lines) 4 4 6 Network protectors 4   Panel boards—single phase (all) / three phase 4 8 12 (100 A) Panel boards—three phase (>100 A) 4   This table was developed from fault testing based on equipment type and is independent of fault current unless oth- erwise noted. Calculations and test data are based on a 46 cm (18 in) separation distance from the arc to the employee. See IEEE Std 1584-2002. Other methods are available to estimate arc exposure values and may yield slightly different but equally acceptable results. The use of the table in the selection of clothing is intended to reduce the amount or degree of injury but may not prevent all burns. Industry testing on this equipment by two separate major utilities and a research institute has demonstrated that volt- ages 50 V to 250 V will not sustain arcs for more than 2 cycles, thereby limiting exposure to less than 4 cal/cm2. (See 208-V Arc Flash Testing [B1].) Value based on IEEE 1584 formula for Motor Control Centers. [Gap = 2.54 cm (1 in)] (Xd = 1.641) [46 cm (18 in) distance] 51 kA (Based on a 208 V, 1000 kVA, 5.3% Z, served from a 500 MVA system) Maximum duration with- out circuit protective device operation from industry testing (see 208-V Arc Flash Testing [B1]) is 10 cycles: 46.5 cal/s/cm2 x 0.167 s = 7.8 cal/cm2. Industry testing on 480 V-200 A, self-contained, Form 16S, single-socket meter cabinet indicates exposures do not exceed 20 cal/cm2 [B2] Testing on 480 V 400 A, Class 320-A meter sockets and multi-meter panels (with large amounts of internal exposed bus bar) indicates higher heat flux rates and do not self-extinguish similar to larger pow- er panels. (See Footnote 13 and 480-V Distribution Arc Flash Updates [B2]. Industry testing on 480 V equipment indicates exposures for CT meters and control wiring does not exceed 4 cal/cm2. Value based on IEEE 1584 formula for Motor Control Centers. [Gap = 2.54 cm (1 in)] (Xd = 1.641) [46 cm (18 in) distance] 12.7 kA at 480 V (worst-case energy value from testing). (See Eblen and Short [B29].) Maximum duration without circuit protective device operation from tests is 85 cycles: 26.2 cal/s/cm2 x 1.42 s = 37 cal/cm2. Incident analysis on this equipment indicates exposures do not exceed the values in the table. Engineering analysis indicates that applying a 150% multiplier to the 480 V exposure values provides a conservative value for equipment and open air lines operating at 601 V to 1000 V. Industry testing on 480 V equipment indicates exposures on pad-mounted transformers do not exceed 4 cal/cm2. (See Eblen and Short [B29].) Industry testing on 208 V network protectors indicates exposures do not exceed 4 cal/cm2. (See 208-V Arc Flash Testing [B1].) Industry testing on 480 V network protectors indicates arcs will not self-extinguish and heat flux rates will exceed 60 cal/cm2/s at 24 in working distance. Perform arc hazard analysis. (See Eblen and Short [B29].) 280 Copyright © 2016 IEEE. All rights reserved. T-410-1 Part 4: Work Rules T-410-2 Industry testing on 480 V panels with non-edge mounted bus bars indicates exposures do not exceed 8 cal/cm2. (See Eblen and Short [B29].) Industry testing on panelboards with edge-mounted, parallel bus bars indicate arcs will not self-extinguish and heat flux rates will exceed 60 cal/cm2/s at 46 cm (18 in) working distance. Perform arc hazard analysis. (See Eblen and Short [B29].) IEEE 1584 original test data indicates there is no significant difference between heat flux rates for 400 V class equip- ment verses 600 V class equipment. Table 410-2—Clothing and clothing systems—voltage, fault current, and maximum clearing time for voltages 1.1 kV to 46 kV ac  (See Rule 410A3.) 4-cal system 8-cal system 12-cal system Phase-to-phase Fault current voltage Maximum Maximum Maximum (kA) (kV) clearing time clearing time clearing time (cycles) (cycles) (cycles) 1.1 to 15 5 46.5 93.0 139.5 10 18.0 36.1 54.1 15 10.0 20.1 30.1 20 6.5 13.0 19.5 15.1 to 25 5 27.6 55.2 82.8 10 11.4 22.7 34.1 15 6.6 13.2 19.8 20 4.4 8.8 13.2 25.1 to 36 5 20.9 41.7 62.6 10 8.8 17.6 26.5 15 5.2 10.4 15.7 20 3.5 7.1 10.6 36.1 to 46 5 16.2 32.4 48.6 10 7.0 13.9

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