Overhead Lines Safety Rules PDF

T-235-1 Part 2: Safety Rules for Overhead Lines T-235-1 Table 235-1—Horizontal clearance between wires, conductors, or cables at supports (All voltages are between conductors involved except for railway feeders, which are to gr...

T-235-1 Part 2: Safety Rules for Overhead Lines T-235-1 Table 235-1—Horizontal clearance between wires, conductors, or cables at supports (All voltages are between conductors involved except for railway feeders, which are to ground. See also Rules 235A, 235B1a, and 235B3b.) Clearance Class of circuit Notes (mm) (in) Open communication conductors 150 6 Does not apply at conductor transposition points. 75 3 Permitted where pin spac- ings less than 150 mm (6 in) have been in regular use. Does not apply at conductor transposition points. Railway feeders: Where 250 mm to 300 mm 0 to 750 V, AWG No. 4/0 or larger 150 6 (10 in to 12 in) clearance has 0 to 750 V, smaller than AWG No. 4/0 300 12 already been established by Over 750 V to 8.7 kV 300 12 practice, it may be continued, subject to the provisions of Rule 235B1b, for conductors having final sags not over 900 mm (3 ft) and for voltages not exceeding 8.7 kV. Supply conductors of the same circuit: 0 to 8.7 kV 300 12 Over 8.7 kV to 50 kV 300 plus 10 per 12 plus 0.4 per kV kV in excess of in excess of 8.7 kV 8.7 kV Above 50 kV No value No value specified specified Supply conductors of different circuits: For all voltages above 0 to 8.7 kV 300 12 50 kV, the additional Over 8.7 kV to 50 kV 300 plus 10 per 12 plus 0.4 per kV clearance shall be increased kV in excess of in excess of 8.7 3% for each 300 m (1000 ft) 8.7 kV kV in excess of 1000 m (3300 ft) above mean sea Over 50 kV to 814 kV 715 plus 29 plus level. All clearances for 10 per kV in 0.4 per kV in voltages above 50 kV shall excess of 50 kV excess of 50 kV be based on the maximum operating voltage. 167 Copyright © 2016 IEEE. All rights reserved. T-235-2(m) Part 2: Safety Rules for Overhead Lines T-235-2(in) m Table 235-2—Horizontal clearances between line conductors smaller than AWG No. 2 at supports, based on sags (See also Rules 235A and 235B1b.) Sag (mm) Voltage But between 915 1220 1830 2440 3050 4570 6095 not less conductors than  (kV) Horizontal clearance (mm) 2.4 375 525 735 895 1030 1305 1530 300 4.16 390 540 745 905 1040 1320 1545 300 12.47 455 600 810 970 1105 1380 1610 340 13.2 460 605 815 975 1100 1385 1615 345 13.8 465 610 820 980 1115 1390 1620 355 14.4 470 615 825 985 1120 1395 1625 360 24.94 550 695 905 1065 1200 1475 1705 465 34.5 620 770 975 1135 1270 1550 1775 560 46 710 855 1065 1225 1360 1635 1865 675 Clearance determined by Table 235-1, Rule 235B1a. NOTE: Clearance = 7.6 per kV + 20.4 S – 610 , where S is the sag in millimeters. 168 Copyright © 2016 IEEE. All rights reserved. T-235-2(in) Part 2: Safety Rules for Overhead Lines T-235-2(in) in Table 235-2—Horizontal clearances between line conductors smaller than AWG No. 2 at supports, based on sags (See also Rules 235A and 235B1b.) Sag (in) Voltage between But conductors 36 48 72 96 120 180 240 not less (kV) than  Horizontal clearance (in) 2.4 15 21 29 36 41 52 61 12 4.16 16 22 30 36 41 52 61 12 12.47 18 24 32 39 44 55 64 14 13.2 18 24 32 39 44 55 64 14 13.8 19 24 33 39 44 55 64 15 14.4 19 25 33 39 44 55 64 15 24.94 22 28 36 42 48 58 67 19 34.5 25 31 39 45 50 61 70 23 46 28 34 42 49 54 65 74 27 Clearance determined by Table 235-1, Rule 235B1a. NOTE: Clearance = 0.3 per kV + 4.04 S – 24 , where S is the sag in inches. 169 Copyright © 2016 IEEE. All rights reserved. T-235-3(m) Part 2: Safety Rules for Overhead Lines T-235-3(m) m Table 235-3—Horizontal clearances between line conductors AWG No. 2 or larger at supports, based on sags (See also Rules 235A and 235B1b.) Sag (mm) Voltage between But conductors 915 1220 1830 2440 3050 4570 6095 not less (kV) than  Horizontal clearance (mm) 2.4 375 430 520 595 665 810 930 300 4.16 385 440 530 610 675 820 945 300 12.47 450 505 595 675 740 885 1005 340 13.2 455 510 600 680 745 890 1010 345 13.8 460 515 605 685 750 895 1015 355 14.4 465 520 610 685 755 900 1020 360 24.94 545 600 690 765 835 980 1100 465 34.5 615 670 765 840 910 1050 1175 560 46 705 760 850 925 995 1140 1260 675  Clearance determined by Table 235-1, Rule 235B1a. NOTE: Clearance = 7.6 per kV + 8 2.12S , where S is the sag in millimeters. 170 Copyright © 2016 IEEE. All rights reserved. T-235-3(in) Part 2: Safety Rules for Overhead Lines T-235-3(in) in Table 235-3—Horizontal clearances between line conductors AWG No. 2 or larger at supports, based on sags (See also Rules 235A and 235B1b.) Sag (in) Voltage between But conductors 36 48 72 96 120 180 240 not less (kV) than  Horizontal clearance (in) 2.4 15 17 21 24 27 32 37 12 4.16 16 18 21 24 27 33 38 12 12.47 18 20 24 27 30 35 40 14 13.2 18 20 24 27 30 35 40 14 13.8 18 21 24 27 30 36 40 15 14.4 19 21 24 27 30 36 41 15 24.94 22 24 28 31 33 39 44 19 34.5 25 27 30 33 36 42 47 23 46 28 30 34 37 40 45 50 27 Clearance determined by Table 235-1, Rule 235B1a. NOTE: Clearance = 0.3 per kV + 8 S  12 , where S is the sag in inches. 171 Copyright © 2016 IEEE. All rights reserved. T-235-4 Part 2: Safety Rules for Overhead Lines T-235-4 Table 235-4—Electrical clearances in Rule 235B3a(1) [This clearance shall be increased 3% for each 300 m (1000 ft) in excess of 450 m (1500 ft) above mean sea level.] Maximum Electrical component of clearance Switching Switching operating voltage surge factor surge phase to phase (per unit) (kV) (m) (ft) (kV) 242 2.6 or less 890 or less 1.94 6.4 2.8 958 2.20 7.2 3.0 1027 2.47 8.1 3.2 or more 1095 or more 2.65  8.8  362 1.8 893 or less 2.06 6.8 2.0 1024 2.46 8.1 2.2 1126 2.88 9.5 2.4 1228 3.4 10.9 2.6 1330 3.8 12.5 2.7 or more 1382 or more 3.9  12.8  550 1.6 1245 3.4 11.2 1.8 1399 4.2 13.6 2.0 1555 5.0 16.2 2.2 1711 5.8  19.0  2.3 1789 or more 5.8  19.1  800 1.6 1810 6.4 20.8 1.8 2037 7.8 25.3 1.9 or more 2149 or more 8.3  27.4  Not used in this edition. Need not be greater than specified in Rules 235B1 and 235B2. 172 Copyright © 2016 IEEE. All rights reserved. T-235-5(m) Part 2: Safety Rules for Overhead Lines T-235-5(m) m Table 235-5— Vertical clearance between conductors at supports (When using column and row headings, voltages are phase to ground for effectively grounded circuits and those other circuits where all ground faults are cleared by promptly de-energizing the faulted section, both initially and following subsequent breaker operations. When calculating clearance values within the table, all voltages are between the conductors involved. See the definitions section for voltages of other systems. See also Rules 235A, 235C1, 235C2, and 235F.) Conductors and cables usually at upper levels  Supply cables Open supply conductors meeting Rule 230C1, 230C2, Over 8.7 kV to 50 kV or 230C3; Conductors and cables neutral usually at lower levels conductors meeting Rule 0 to 230E1; 8.7 kV Different communica- (m) Same utility  utilities  tions cables (m) (m) meeting Rule 224A2 (m) 1. Communication conductors and cables a. Located in the communication 1.00   1.00 1.00 1.00 plus 0.01 space per kV  in excess of 8.7 kV b. Located in the supply space 0.41  0.41  1.00  1.00 plus 0.01 per kV  in excess of 8.7 kV 2. Supply conductors and cables a. Open conductors 0 to 750 V ; 0.41  0.41  0.41 plus 0.01 1.00 plus 0.01 supply cables meeting Rule 230C1, per kV  per kV  230C2, or 230C3; neutral in excess of in excess of conductors meeting Rule 230E1 8.7 kV 8.7 kV b. Open conductors over 750 V to 0.41  0.41 plus 0.01 1.00 plus 0.01 8.7 kV per kV   per kV A  in excess of in excess of 8.7 kV 8.7 kV c. Open conductors over 8.7 to 22 kV (1) If worked on energized with 0.41 plus 0.01 1.00 plus 0.01 live-line tools and adjacent circuits per kV  per kV  are neither de-energized nor covered in excess of in excess of with shields or protectors 8.7 kV 8.7 kV 173 Copyright © 2016 IEEE. All rights reserved. T-235-5(m) Part 2: Safety Rules for Overhead Lines T-235-5(m) m Table 235-5— (continued) Vertical clearance between conductors at supports (When using column and row headings, voltages are phase to ground for effectively grounded circuits and those other circuits where all ground faults are cleared by promptly de-energizing the faulted section, both initially and following subsequent breaker operations. When calculating clearance values within the table, all voltages are between the conductors involved. See the definitions section for voltages of other systems. See also Rules 235A, 235C1, 235C2, and 235F.) Conductors and cables usually at upper levels  Supply cables Open supply conductors meeting Rule 230C1, 230C2, Over 8.7 kV to 50 kV or 230C3; Conductors and cables neutral usually at lower levels conductors meeting Rule 0 to 230E1; 8.7 kV Different communica- (m) Same utility  utilities  tions cables (m) (m) meeting Rule 224A2 (m) (2) If not worked on energized except 0.41 plus 0.01 0.41 plus 0.01 when adjacent circuits (either above or per kV   per kV   below) are de-energized or covered by in excess of in excess of shields or protectors, or by the use of 8.7 kV 8.7 kV live-line tools not requiring line workers to go between live wires d. Open conductors exceeding 0.41 plus 0.01 1.00 plus 0.01 22 kV, but not exceeding 50 kV per kV   per kV   in excess of in excess of 8.7 kV 8.7 kV Where railroad supply circuits of 600 V or less, with transmitted power of 5000 W or less, are run below communication circuits in accordance with Rule 220B2, the clearance may be reduced to 0.41 m. Where conductors are operated by different utilities, a vertical clearance of not less than 1.00 m is recommended. These values do not apply to conductors of the same circuit or circuits being carried on adjacent conductor supports. May be reduced to 0.41 m where conductors are not worked on energized except when adjacent circuits (either above or below) are de-energized or covered by shields or protectors, or by the use of live-line tools not requiring line workers to go between live wires. May be reduced to 0.75 m for supply neutrals meeting Rule 230E1, fiber-optic supply cables on an effectively grounded messenger meeting Rule 230F1a, entirely dielectric fiber-optic supply cables meeting Rule 230F1b, insulated communication cables located in the supply space and supported by an effectively grounded messenger, and cables meeting Rule 230C1 where the supply neutral or messenger is bonded to the communication messenger at intervals specified in Rule 092C. Bonding is not required for entirely dielectric cables meeting Rule 230F1b. The greater of phasor difference or phase-to-ground voltage; see Rule 235A3. See examples of calculations in Rules 235C2a and 235C2b. For supply cables meeting Rule 230C3 and neutral conductors meeting Rule 230E1, see Rule 235G. No clearance is specified between neutral conductors meeting Rule 230E1 and insulated communication cables located in the supply space and supported by an effectively grounded messenger. The cable messenger may be attached to the neutral at the pole or in the span, provided that the cable is positioned away from the neutral to prevent abrasion damage. If the cable messenger is not attached to the neutral in the span, midspan spacing shall be not less than that specified in Rule 235G. No clearance is specified between fiber-optic supply cables (FOSC) meeting Rule 230F1b and supply cables and conductors. The FOSC may be attached to a supply conductor or cable at the pole or in the span, provided that the FOSC is positioned away from the supply conductor or cable to prevent abrasion damage. If the FOSC is not attached to the neutral in the span, midspan spacing shall be not less than that specified in Rule 235G. 174 Copyright © 2016 IEEE. All rights reserved. T-235-5(m) Part 2: Safety Rules for Overhead Lines T-235-5(in) Does not include neutral conductors meeting Rule 230E1. For simplicity, this table shows clearance requirements between specified facilities located in frequently used posi- tions over or under one another. Where such facilities are located in opposite relative positions from those shown in the table, the table values for usual positions are to be used. in Table 235-5— Vertical clearance between conductors at supports (When using column and row headings, voltages are phase to ground for effectively grounded circuits and those other circuits where all ground faults are cleared by promptly de-energizing the faulted section, both initially and following subsequent breaker operations. When calculating clearance values within the table, all voltages are between the conductors involved. See the definitions section for voltages of other systems. See also Rules 235A, 235C1, 235C2, and 235F.) Conductors and cables usually at upper levels  Supply cables Open supply conductors meeting Rule 230C1, 230C2, or Over 8.7 kV to 50 kV Conductors and cables 230C3; neutral usually at lower levels conductors meeting Rule 0 to 230E1; 8.7 kV  Different communications (in) Same utility  utilities  cables meeting (in) (in) Rule 224A2 (in) 1. Communication conductors and cables a. Located in the communication 40   40 40 40 plus 0.4 space per kV in excess of 8.7 kV b. Located in the supply space 16   16  40  40 plus 0.4 per kV  in excess of 8.7 kV 2. Supply conductors and cables a. Open conductors 0 to 750 V ; 16  16  16 plus 0.4 40 plus 0.4 supply cables meeting Rule per kV  per kV  230C1, 230C2, or 230C3; in excess of 8.7 kV in excess of 8.7 kV neutral conductors meeting Rule 230E1 b. Open conductors over 750 V 16  16 plus 0.4 40 plus 0.4 to 8.7 kV per kV   per kV  in excess of 8.7 kV in excess of 8.7 kV c. Open conductors over 8.7 kV to 22 kV (1) If worked on energized with 16 plus 0.4 40 plus 0.4 live-line tools and adjacent per kV  per kV  circuits are neither de- in excess of in excess of energized nor covered with 8.7 kV 8.7 kV shields or protectors 175 Copyright © 2016 IEEE. All rights reserved. T-235-5(in) Part 2: Safety Rules for Overhead Lines T-235-5(in) in Table 235-5— (continued) Vertical clearance between conductors at supports (When using column and row headings, voltages are phase to ground for effectively grounded circuits and those other circuits where all ground faults are cleared by promptly de-energizing the faulted section, both initially and following subsequent breaker operations. When calculating clearance values within the table, all voltages are between the conductors involved. See the definitions section for voltages of other systems. See also Rules 235A, 235C1, 235C2, and 235F.) Conductors and cables usually at upper levels  Supply cables Open supply conductors meeting Rule 230C1, 230C2, or Over 8.7 kV to 50 kV Conductors and cables 230C3; neutral usually at lower levels conductors meeting Rule 0 to 230E1; 8.7 kV  Different communications (in) Same utility  utilities  cables meeting (in) (in) Rule 224A2 (in) (2) If not worked on energized 16 plus 0.4 16 plus 0.4 except when adjacent circuits per kV   per kV   (either above or below) are de- in excess of in excess of energized or covered by shields 8.7 kV 8.7 kV or protectors, or by the use of live-line tools not requiring line workers to go between live wires d. Open conductors exceeding 16 plus 0.4 40 plus 0.4 22 kV, but not exceeding per kV   per kV   50 kV in excess of in excess of 8.7 kV 8.7 kV Where railroad supply circuits of 600 V or less, with transmitted power of 5000 W or less, are run below communication circuits in accordance with Rule 220B2, the clearance may be reduced to 16 in. Where conductors are operated by different utilities, a vertical clearance of not less than 40 in is recommended. These values do not apply to conductors of the same circuit or circuits being carried on adjacent conductor supports. May be reduced to 16 in where conductors are not worked on energized except when adjacent circuits (either above or below) are de-energized or covered by shields or protectors, or by the use of live line tools not requiring line workers to go between live wires. May be reduced to 30 in for supply neutrals meeting Rule 230E1, fiber-optic supply cables on an effectively grounded messenger meeting Rule 230F1a, entirely dielectric fiber-optic supply cables meeting Rule 230F1b, insulated commu- nication cables located in the supply space and supported by an effectively grounded messenger, and cables meeting meeting Rule 230C1 where the supply neutral or messenger is bonded to the communication messenger at intervals specified in Rule 092C. Bonding is not required for entirely dielectric cables meeting Rule 230F1b. The greater of phasor difference or phase-to-ground voltage; see Rule 235A3. See examples of calculations in Rules 235C2a and 235C2b. For supply cables meeting Rule 230C3 and neutral conductors meeting Rule 230E1, see Rule 235G. No clearance is specified between neutral conductors meeting Rule 230E1 and insulated communication cables located in the supply space and supported by an effectively grounded messenger. The cable messenger may be attached to the neutral at the pole or in the span, provided that the cable is positioned away from the neutral to prevent abrasion damage. If the cable messenger is not attached to the neutral in the span, midspan spacing shall be not less than that specified in Rule 235G. No clearance is specified between fiber-optic supply cables (FOSC) meeting Rule 230F1b and supply cables and conductors. The FOSC may be attached to a supply conductor or cable at the pole or in the span, provided that the FOSC is positioned away from the supply conductor or cable to prevent abrasion damage. If the FOSC is not attached to the neutral in the span, midspan spacing shall be not less than that specified in Rule 235G. 176 Copyright © 2016 IEEE. All rights reserved. T-235-5(in) Part 2: Safety Rules for Overhead Lines T-235-6(mm) Does not include neutral conductors meeting Rule 230E1. For simplicity, this table shows clearance requirements between specified facilities located in frequently used posi- tions over or under one another. Where such facilities are located in opposite relative positions from those shown in the table, the table values for usual positions are to be used. mm Table 235-6— Clearance in any direction from line conductors at or near a support to supports, and to vertical or lateral conductors, service drops, span or guy wires, and to communication antennas attached to the same support [See also Rules 235A, 235E1, 235E3b(2), and 235I.] Supply lines Commu- Commu- nication Circuit phase-to-phase voltage nication lines on Neutral Clearance of line lines in jointly conductors conductors from Over 50 kV general used meeting 0 to Over 8.7 kV (mm) structures Rule 230E1 to 8.7 kV  to 50 kV (mm) (mm) 814 kV   (mm) (mm) (mm) 1. Vertical and lateral conductors— at the support a. Of the same circuit 75 75 75 75 75 plus 6.5 No value per kV specified in excess of 8.7 kV b. Of other circuits  75 75 75 150  150 plus 10 580 plus 10 per kV per kV in excess of in excess of 8.7 kV 50 kV c. Communication  75 75 75 150  150 plus 10 580 plus 10 antennas per kV per kV in excess of in excess of 8.7 kV 50 kV 2. Span or guy wires, or messengers attached to same structure—at or near the support a. When parallel to line 75  150   150   300  300 plus 10 740 plus 10 per kV per kV in excess of in excess of 8.7 kV 50 kV b. Anchor guys 75  150   150   150  150 plus 6.5 410 plus 6.5 per kV per kV in excess of in excess of 8.7 kV 50 kV c. All other 75  150   150   150 150 plus 10 580 plus 10 per kV per kV in excess of in excess of 8.7 kV 50 kV 177 Copyright © 2016 IEEE. All rights reserved. T-235-6(mm) Part 2: Safety Rules for Overhead Lines T-235-6(mm) mm Table 235-6— (continued) Clearance in any direction from line conductors at or near a support to supports, and to vertical or lateral conductors, service drops, span or guy wires, and to communication antennas attached to the same support [See also Rules 235A, 235E1, 235E3b(2), and 235I.] Supply lines Commu- Commu- nication Circuit phase-to-phase voltage nication lines on Neutral Clearance of line lines in jointly conductors conductors from Over 50 kV general used meeting 0 to Over 8.7 kV (mm) structures Rule 230E1 to 8.7 kV  to 50 kV (mm) (mm) 814 kV   (mm) (mm) (mm) 3. Surface of support 75  75  75  75  75 plus 5 280 plus 5 arms—at the per kV per kV support in excess of in excess of 8.7 kV 50 kV 4. Surface of structures— at the support a. On jointly used — 125  125  125 125 plus 5 330 plus 5 structures per kV per kV in excess of in excess of 8.7 kV   50 kV b. All other 75  — — 75  75 plus 5 280 plus 5 per kV per kV in excess of in excess of 8.7 kV   50 kV 5. Service drops— in the span:  a. Communication 300 300 750  750 750 plus 10 1200 plus 10 per kV per kV in excess of in excess of 8.7 kV 50 kV b. Supply N/A 750 300 300 300 plus 10 750 plus 10 per kV per kV in excess of in excess of 8.7 kV 50 kV For guy wires, if practical. For clearances between span wires and communication conductors, see Rule 238C. On jointly used structures, guys that pass within 300 mm of supply conductors, and also pass within 300 mm of communication cables, shall be protected with a suitable insulating covering where the guy passes the supply conductors, unless the guy is effectively grounded or insulated with a strain insulator at a point below the lowest supply conductor and above the highest communication cable. The clearance from an insulated or effectively grounded guy to a communication cable may be reduced to 75 mm when abrasion protection is provided on the guy or communication cable. Communication conductors may be attached to supports on the sides or bottom of crossarms or surfaces of poles with less clearance. This clearance applies only to supply conductors at the support below communication conductors, on jointly used structures. Where supply conductors are above communication conductors, this clearance may be reduced to 75 mm. 178 Copyright © 2016 IEEE. All rights reserved. T-235-6(mm) Part 2: Safety Rules for Overhead Lines T-235-6(mm) All clearances for line over 50 kV shall be based on the maximum operating voltage. For voltages exceeding 814 kV, the clearance shall be determined by the alternate method given by Rule 235E3. For supply circuits of 0 to 750 V, this clearance may be reduced to 75 mm. A neutral conductor meeting Rule 230E1 may be attached directly to the structure surface. Guys and messengers may be attached to the same strain plates or to the same through bolts. For open supply circuits of 0 to 750 V and supply cables of all voltages meeting Rule 230C1, 230C2, or 230C3, this clearance may be reduced to 25 mm. No clearance is specified for phase conductors of such cables where they are physically restrained by a suitable bracket from abrasion against the pole. The additional clearance for voltages in excess of 50 kV specified in Table 235-6 shall be increased 3% for each 300 m in excess of 1000 m above mean sea level. Where the circuit is effectively grounded and the neutral conductor meets Rule 230E1, phase-to-ground voltage may be used to determine the clearance from the surface of support arms and structures. These clearances may be reduced by not more than 25% to a guy insulator, provided that full clearance is maintained to its metallic end fittings and the guy wires. The clearance to an insulated section of a guy between two insulators may be reduced by not more than 25% provided that full clearance is maintained to the uninsulated portion of the guy. See Rule 235A3 to determine the voltage between the conductors involved. These clearances from supply conductors apply to communication antennas located in the supply space and operated at a radio frequency of 3 kHz to 300 GHz. Also see Rules 235I4, 238A, and 239H1, EXCEPTION 3. Does not include neutral conductors meeting Rule 230E1. These service drop values apply anywhere in the span but not at the support. For vertical clearances at the support, see Table 235-5. NOTE: These values were derived from Table 235-5 and Rule 235C2b(1)(a). This value may be reduced to 300 mm if the supply neutral and communication messenger are electrically bonded together. For clearance requirements in any direction between vertical or lateral supply conductors located in the supply space and communication line conductors located in the communication space, use the values in Table 235-5, row 1. 179 Copyright © 2016 IEEE. All rights reserved. T-235-6(in) Part 2: Safety Rules for Overhead Lines T-235-6(in) in Table 235-6— Clearance in any direction from line conductors at or near a support to supports, and to vertical or lateral conductors, service drops, span or guy wires, and to communication antennas attached to the same support [See also Rules 235A, 235E1, 235E3b(2), and 235I.] Supply lines Communi- Communi- cation Circuit phase-to-phase voltage cation lines on Neutral Clearance of line lines in jointly conductors conductors from Over 50 kV general used meeting 0 to Over 8.7 kV (in) structures Rule 230E1 to 8.7 kV  to 50 kV (in) (in) 814 kV  (in) (in) (in) 1. Vertical and lateral conductors— at the support a. Of the same circuit 3 3 3 3 3 plus 0.25 No value per kV specified in excess of 8.7 kV b. Of other circuits  3 3 3 6 6 plus 0.4 23 plus 0.4 per kV per kV in excess of in excess of 8.7 kV 50 kV c. Communication 3 3 3 6 6 plus 0.4 23 plus 0.4 antennas  per kV per kV in excess of in excess of 8.7 kV 50 kV 2. Span or guy wires, or messengers attached to same structure—at or near the support a. When parallel to line 3 6 6 12  12 plus 0.4 29 plus 0.4 per kV per kV in excess of in excess of 8.7 kV 50 kV b. Anchor guys 3 6  6  6 6 plus 0.25 16 plus 0.25 per kV per kV in excess of in excess of 8.7 kV 50 kV c. All other 3 6 6  6 6 plus 0.4 23 plus 0.4 per kV per kV in excess of in excess of 8.7 kV 50 kV 3. Surface of support 3 3 3 3 3 plus 0.2 11 plus 0.2 arms—at the per kV per kV support in excess of in excess of 8.7 kV 50 kV 180 Copyright © 2016 IEEE. All rights reserved. T-235-6(in) Part 2: Safety Rules for Overhead Lines T-235-6(in) in Table 235-6— (continued) Clearance in any direction from line conductors at or near a support to supports, and to vertical or lateral conductors, service drops, span or guy wires, and to communication antennas attached to the same support [See also Rules 235A, 235E1, 235E3b(2), and 235I.] Supply lines Communi- Communi- cation Circuit phase-to-phase voltage cation lines on Neutral Clearance of line lines in jointly conductors conductors from Over 50 kV general used meeting 0 to Over 8.7 kV (in) structures Rule 230E1 to 8.7 kV  to 50 kV (in) (in) 814 kV  (in) (in) (in) 4. Surface of structures— at the support a. On jointly used — 5 5  5 5 plus 0.2 13 plus 0.2 structures per kV per kV in excess of in excess of 8.7 kV   50 kV b. All other 3 — — 3 3 plus 0.2 11 plus 0.2 per kV per kV in excess of in excess of 8.7 kV 50 kV 5. Service drops— in the span  a. Communication 12 12 30 30 30 plus 0.4 47 plus 0.4 per kV per kV in excess of in excess of 8.7 kV 50 kV b. Supply N/A 30 12 12 12 plus 0.4 29 plus 0.4 per kV per kV in excess of in excess of 8.7 kV 50 kV For guy wires, if practical. For clearances between span wires and communication conductors, see Rule 238C. On jointly used structures, guys that pass within 12 in of supply conductors, and also pass within 12 in of communication cables, shall be protected with a suitable insulating covering where the guy passes the supply conductors, unless the guy is effectively grounded or insulated with a strain insulator at a point below the lowest supply conductor and above the highest communication cable. The clearance from an insulated or effectively grounded guy to a communication cable may be reduced to 3 in when abrasion protection is provided on the guy or communication cable. Communication conductors may be attached to supports on the sides or bottom of crossarms or surfaces of poles with less clearance. This clearance applies only to supply conductors at the support below communication conductors, on jointly used structures. Where supply conductors are above communication conductors, this clearance may be reduced to 3 in. All clearances for line over 50 kV shall be based on the maximum operating voltage. For voltages exceeding 814 kV, the clearance shall be determined by the alternate method given by Rule 235E3. For supply circuits of 0 to 750 V, this clearance may be reduced to 3 in. A neutral conductor meeting Rule 230E1 may be attached directly to the structure surface. Guys and messengers may be attached to the same strain plates or to the same through bolts. 181 Copyright © 2016 IEEE. All rights reserved. T-235-6(in) Part 2: Safety Rules for Overhead Lines T-235-7 For open supply circuits of 0 to 750 V and supply cables of all voltages meeting Rule 230C1, 230C2 or 230C3, this clearance may be reduced to 1 in. No clearance is specified for phase conductors of such cables where they are physically restrained by a suitable bracket from abrasion against the pole. The additional clearance for voltages in excess of 50 kV specified in Table 235-6 shall be increased 3% for each 1000 ft in excess of 3300 ft above mean sea level. Where the circuit is effectively grounded and the neutral conductor meets Rule 230E1, phase-to-ground voltage may be used to determine the clearance from the surface of support arms and structures. These clearances may be reduced by not more than 25% to a guy insulator, provided that full clearance is maintained to its metallic end fittings and the guy wires. The clearance to an insulated section of a guy between two insulators may be reduced by not more than 25% provided that full clearance is maintained to the uninsulated portion of the guy.  See Rule 235A3 to determine the voltage between the conductors involved. These clearances from supply conductors apply to communication antennas located in the supply space and operated at a radio frequency of 3 kHz to 300 GHz. Also see Rules 235I4, 238A, and 239H1, EXCEPTION 3. Does not include neutral conductors meeting Rule 230E1. These service drop values apply anywhere in the span but not at the support. For vertical clearances at the support, see Table 235-5. NOTE: These values were derived from Table 235-5 and Rule 235C2b(1)(a). This value may be reduced to 12 in if the supply neutral and communication messenger are electrically bonded together. For clearance requirements in any direction between vertical or lateral supply conductors located in the supply space and communication line conductors located in the communication space, use the values in Table 235-5, row 1. Table 235-7— Clearance in any direction from line conductors to supports [See also Rules 235A, 235E3b, and 235E3b(1)(a).] Computed clearance to supports Maximum operating Switching- Switching surge Free swinging at voltage phase to surge factor Fixed (kV) maximum angle phase (per unit) (kV) (m) (in) (m) (in) 242 2.4 474 0.88  35  0.88  35  2.6 514 1.01 40 0.88  35  2.8 553 1.14 45 0.98 39  3.0 593 1.24  49 1.10 44  3.2 632 1.24  49 1.22 49    362 1.6 473 0.88 35 0.88 35  1.8 532 1.07 42 0.92 36 2.0 591 1.27 50 1.09 43 2.2 650 1.49 59 1.28 51 2.4 709 1.72 68 1.48 59 2.5 739 1.84 73 1.59 63 550 1.6 719 1.76 69 1.51 60 1.8 808 2.14 84 1.84 73 182 Copyright © 2016 IEEE. All rights reserved. T-235-7 Part 2: Safety Rules for Overhead Lines T-235-8 Table 235-7— (continued) Clearance in any direction from line conductors to supports [See also Rules 235A, 235E3b, and 235E3b(1)(a).] Computed clearance to supports Maximum operating Switching- Switching surge Free swinging at voltage phase to surge factor Fixed (kV) maximum angle phase (per unit) (kV) (m) (in) (m) (in) 2.0 898 2.55 100 2.19 87 2.2 988 2.78  111  2.57 102 800 1.6 1045 3.3 129 2.82 111 1.8 1176 4.0 157 3.5 136 1.9 1241 4.1 161  3.8 148 2.0 1306 4.1 161  4.1  161  Shall be not less than that required by Rule 235E3b(2), including the altitude correction for lines as specified in Footnote 9 of Table 235-6. Need not be greater than specified in Rules 235E1 and 235E2. Table 235-8—Vertical spacing between conductors supported on vertical racks or separate brackets Span length Vertical spacing between conductors (m) (ft) (mm) (in) 0 to 45 0 to 150 100 4 Over 45 to 60 Over 150 to 200 150 6 Over 60 to 75 Over 200 to 250 200 8 Over 75 to 90 Over 250 to 300 300 12 EXCEPTION: The vertical spacing between open wire conductors may be reduced where the conductors are held apart by intermediate spacers, but may not be less than 100 mm (4 in). 183 Copyright © 2016 IEEE. All rights reserved. 236 Part 2: Safety Rules for Overhead Lines 236F 236. Climbing space The following requirements apply only to portions of structures that workers ascend. A. Location and dimensions 1. A climbing space having the horizontal clearances specified in Rule 236E shall be provided past any conductors, support arms, or other parts. 2. The climbing space need be provided on one side or corner of the support only. 3. The climbing space shall extend vertically past any conductor or other part between levels above and below the conductor as specified in Rules 236E, F, G, and I, but may otherwise be shifted from any side or corner of the support to any other side or corner. B. Portions of supporting structures in climbing space Portions of the supporting structure, when included in one side or corner of the climbing space, are not considered to obstruct the climbing space. C. Support arm location relative to climbing space Support arms should be located on the same side of the pole. EXCEPTION: Rule 236C does not apply where double crossarms are used on any pole or where crossarms on any pole are not all parallel. D. Location of equipment relative to climbing space 1. All supply and communication equipment such as transformers, regulators, capacitors, cable terminals (potheads), amplifiers, loading coils, antennas, photovoltaic panels, power supplies, surge arresters, switches, etc., when located below conductors or other attachments, shall be mounted outside of the climbing space. 2. All exposed ungrounded conductive parts of luminaires and their supports that are not insulated from current-carrying parts shall be maintained at not less than 500 mm (20 in) from the sur- face of their supporting structure. EXCEPTION 1: This may be reduced to 125 mm (5 in) if located on the side of the structure opposite the designated climbing space. EXCEPTION 2: This does not apply where the equipment is located at the top or other vertical portion of the structure that is not subject to climbing. E. Climbing space between conductors Climbing space between conductors shall be not less than the horizontal clearances specified in Table 235-6. These clearances are intended to provide a clear climbing space of 600 mm (24 in) while the conductors bounding the climbing space are covered with temporarily installed protective covering rated for the voltage involved. The climbing space shall be provided both along and across the line and shall be projected vertically not less than 1.0 m (40 in) above and below the limiting conductors. Where communication conductors are above supply conductors of more than 8.7 kV to ground or 15 kV line to line, the climbing space shall be projected vertically at least 1.50 m (60 in) above the highest supply conductors. EXCEPTION 1: This rule does not apply if it is the unvarying practice of the employers concerned to prohibit employees from ascending beyond the conductors or equipment of a given line or structure unless the conductors or equipment are de-energized and grounded per Rule 444D. EXCEPTION 2: For railroad conductors carried on a structure in a position below communications facilities in the manner permitted in Rule 220B2, the climbing space need not extend more than 600 mm (2 ft) above such supply space. EXCEPTION 3: If the conductors are owned, operated, or maintained by the same utility, the climbing space may be provided by temporarily moving the line conductors using live-line tools. F. Climbing space on buckarm construction Method of providing climbing space on buckarm construction 184 Copyright © 2016 IEEE. All rights reserved. 236F1 Part 2: Safety Rules for Overhead Lines 236I The full width of climbing space shall be maintained on buckarm construction and shall extend vertically in the same position at least 1.0 m (40 in) [or 1.50 m (60 in) where required by Rule 236E] above and below any limiting conductor. A six-pin crossarm having pin spacing of 370 mm (14.5 in) may be used to provide a 750 mm (30 in) climbing space on one corner of a junction pole by omitting the pole pins on all arms, and inserting pins midway between the remaining pins so as to give a spacing of 185 mm (7.25 in), provided that all of the following conditions are met: 1. Circuits are less than 8.7 kV to ground or 15 kV line to line 2. Span lengths do not exceed 45 m (150 ft) 3. Sags do not exceed 380 mm (15 in) for wires of AWG No. 2 and larger sizes, or 750 mm (30 in) for wires smaller than AWG No. 2 4. Each conductor on the end of every arm is tied to the same side of its insulator 5. The spacing on the next pole is not less than 370 mm (14.5 in) G. Climbing space past longitudinal runs not on support arms The full width of climbing space shall be provided past longitudinal runs and shall extend vertically in the same position from 1.0 m (40 in) below the run to a point 1.0 m (40 in) above [or 1.50 m (60 in) where required by Rule 236E]. The width of climbing space shall be measured from the longitudinal run concerned. Longitudinal runs on racks, or cables on messengers, are not considered as obstructing the climbing space if the location, size, and quantity of the cables permit qualified workers to climb past them. This does not apply where communication conductors are above the longitudinal runs concerned. EXCEPTION 1: If a supply longitudinal run is placed on the side or corner of the supporting structure where climbing space is provided, the width of climbing space shall be measured horizontally from the center of the structure to the nearest supply conductors on support arms, under both of the following conditions: (a) Where the longitudinal run consists of neutral conductors meeting Rule 230E1, open supply conductors carrying not more than 750 V, or supply cables and conductors meeting Rule 230C, all voltages; and is supported close to the structure as by brackets, racks, or pins close to the structure (b) Where the nearest supply conductors on support arms are parallel to and on the same side of the structure as the longitudinal run and within 1.20 m (4 ft) above or below the run EXCEPTION 2: For railroad supply conductors carried on a structure in a position below communications facilities in the manner permitted in Rule 220B2, the climbing space need not extend more than 600 mm (2 ft) above such supply space. EXCEPTION 3: A service drop less than 750 V and meeting Rule 230C is not considered to obstruct the climbing space if all conductors concerned are covered by rubber protective equipment or otherwise guarded as an unvarying practice before workers climb past them, provided that such a service drop is (1) not closer to the longitudinal run at the point of attachment than the diameter of the pole plus 125 mm (5 in) measured horizontally, and (2) not closer than 950 mm (38 in) measured horizontally to the longitudinal run at a point 750 mm (30 in) on the run measured from the point of attachment at the pole. See Figure 236-1. H. Climbing space past vertical conductors Vertical runs physically protected by suitable conduit or other protective covering and securely attached without spacers to the surface of the line structure are not considered to obstruct the climbing space. I. Climbing space near ridge-pin conductors The climbing space specified in Table 235-6 shall be provided above the top support arm to the ridge-pin conductor but need not be carried past it. 185 Copyright © 2016 IEEE. All rights reserved. F-236-1 Part 2: Safety Rules for Overhead Lines F-236-1 Figure 236-1—Rule 236G, EXCEPTION 3 186 Copyright © 2016 IEEE. All rights reserved. T-236-1 Part 2: Safety Rules for Overhead Lines T-236-1 Table 236-1— Horizontal clearance between conductors bounding the climbing space (All voltages are between the two conductors bounding the climbing space except for communication conductors, which are voltage to ground. Where the two conductors are in different circuits, the voltage between conductors shall be the arithmetic sum of the voltages of each conductor to ground for a grounded circuit, or phase to phase for an ungrounded conductor. See also Rule 236E.) Horizontal clearance between conductors bounding the climbing space On structures used solely by On jointly used structures Character of Supply conductors Voltage of conductors Communication adjacent to conductors Communication Supply above conductors above climbing space conductors conductors communica- supply tion conductors conductors (m) (in) (m) (in) (m) (in) (m) (in) 1. Communi- 0 to 150 V No re- — No re- cation quire-  quire- ments ments conductors Exceeding 0.60 24 recom- — 0.60 24 recom- 150 V mended  mended 2. Supply cables All voltages — No meeting Rule  require- 230C1 ments 3. Supply cables All voltages — — 0.60 24 0.60 24 0.75 30 meeting Rule 230C2 or 230C3 4. Open supply 0 to 750 V — — 0.60 24 0.60 24 0.75 30 line conductors and supply 750 V to — — 0.75 30 0.75 30 0.75 30 cables meeting 15 kV Rule 230D 15 kV to — — 0.90 36 0.90 36 0.90 36 28 kV 28 kV to — — 1.00 40 1.00 40 38 kV 38 kV to — — 1.17 46 1.17 46 50 kV 50 kV to — — 1.40 54 1.40 54 73 kV Exceeding — — >1.40 >54 73 kV NOTE: Attention is called to the operating requirements of Rules 441A and 446C, Part 4, of this Code. This relation of levels in general is not desirable and should be avoided. Climbing space shall be the same as required for the supply conductors immediately above, with a maximum of 0.75 m (30 in) except that a climbing space of 0.41 m (16 in) across the line may be employed for communication cables or conductors where the only supply conductors at a higher level are secondaries (0 to 750 V) supplying airport or airway marker lights or crossing over the communication line and attached to the pole top or to a pole-top extension fixture. 187 Copyright © 2016 IEEE. All rights reserved. 237 Part 2: Safety Rules for Overhead Lines 237E3 237. Working space A. Location of working spaces Working spaces shall be provided on the climbing face of the structure at each side of the climbing space. B. Dimensions of working spaces 1. Along the support arm The working space shall extend from the climbing space to the outmost conductor position on the support arm. 2. At right angles to the support arm The working space shall have the same dimension as the climbing space (see Rule 236E). This dimension shall be measured horizontally from the face of the support arm. 3. Vertically The working space shall have a height not less than that required by Rule 235 for the vertical separation of line conductors carried at different levels on the same support. C. Location of vertical and lateral conductors relative to working spaces The working spaces shall not be obstructed by vertical or lateral conductors. Such conductors shall be located on the opposite side of the pole from the climbing side or on the climbing side of the pole at a distance from the support arm at least as great as the width of climbing space required for the highest voltage conductors concerned. Vertical conductors enclosed in suitable conduit may be attached on the climbing side of the structure. D. Location of buckarms relative to working spaces Buckarms may be used under any of the following conditions, provided the climbing space is maintained. Climbing space may be obtained as in Rule 236F. 1. Standard height of working space Lateral working space of the height required by Table 235-5 shall be provided between the crossing or tap line conductors attached to the buckarm and the main line conductors. This may be accomplished by increasing the spacing between the line support arms, as shown in Figure 237-1. 2. Reduced height of working space Where no circuits exceeding 8.7 kV to ground or 15 kV line to line are involved and the clearances of Rules 235B1a and 235B1b are maintained, conductors supported on buckarms may be placed between line conductors having normal vertical spacing, even though such buckarms obstruct the normal working space, provided that a working space of not less than 450 mm (18 in) in height is maintained either above or below line conductors and buckarm conductors. EXCEPTION: The above working space may be reduced to 300 mm (12 in) if both of the following conditions exist: (a) Not more than two sets of the line arms and buckarms are involved (b) Working conditions are rendered safe by providing rubber protective equipment or other suitable devices to insulate and cover line conductors and equipment that are not being worked upon E. Guarding of energized equipment Exposed energized parts of equipment such as switches, circuit breakers, surge arresters, etc., shall be enclosed or guarded if all of the following conditions apply: 1. The equipment is located below the top conductor support 2. The equipment is located on the climbing side of the structure 3. The requirements of Rule 441, Part 4, of this Code cannot be met 188 Copyright © 2016 IEEE. All rights reserved. 237F Part 2: Safety Rules for Overhead Lines 238D F. Working clearances from energized equipment All parts of equipment such as switches, fuses, transformers, surge arresters, luminaires and their support brackets, etc., or other connections that may require operation or adjustment while energized and exposed at such times, shall be so arranged with respect to each other, other equipment, vertical and lateral conductors, and portions of the supporting structure, including supporting platforms or structural members, that in adjustment or operation no portion of the body, including the hands, need be brought closer to any exposed energized parts or conductors than permitted in Part 4, Rule 441 or 446 of this Code. Figure 237-1—Obstruction of working space by buckarm 238. Vertical clearance between specified communications and supply facilities located on the same structure A. Equipment For the purpose of measuring clearances under this rule, equipment shall be taken to mean non- current-carrying metal parts of equipment, including metal supports for cables or conductors, metal support braces that are attached to metal supports or are less than 25 mm (1 in) from transformer cases or hangers that are not effectively grounded, and metal or nonmetallic supports or braces associated with communication cables or conductors. Antennas, photovoltaic panels, power supplies, loading coils, etc., shall also be considered equipment for the purpose of measuring clearances under this rule. B. Clearances in general Vertical clearances between supply conductors and communications equipment, between communication conductors and supply equipment, and between supply and communications equipment shall be not less than the values specified in Table 238-1, except as provided in Rules 238C and 238D. C. Clearances for span wires or brackets Span wires or brackets carrying luminaires, traffic signals, or trolley conductors shall have vertical clearances from communications lines and equipment not less than the values specified in Table 238-2. D. Clearance of drip loops associated with luminaires and traffic signals If a drip loop of conductors entering a luminaire, a luminaire bracket, or a traffic signal bracket is above a communication cable, the lowest point of the loop shall be not less than 300 mm (12 in) above the highest (1) communication cable, or (2) through bolt or other equipment. EXCEPTION: The above clearance may be reduced to 75 mm (3 in) if the loop is covered by a suitable nonmetallic covering that extends at least 50 mm (2 in) beyond the loop. 189 Copyright © 2016 IEEE. All rights reserved. 238E Part 2: Safety Rules for Overhead Lines T-238-2 E. Communication worker safety zone The clearances specified in Rules 235C and 238 create a communication worker safety zone between the facilities located in the supply space and facilities located in the communication space, both at the structure and in the span between structures. Except as allowed by Rules 238C, 238D, and 239, no supply or communication facility shall be located in the communication worker safety zone. Table 238-1—Vertical clearance between supply conductors and communications equipment, between communication conductors and supply equipment, and between supply and communications equipment (Voltages are phase to ground for effectively grounded circuits and those other circuits where all ground faults are cleared by promptly de-energizing the faulted section, both initially and following subsequent breaker operations. See the definitions section for voltages of other systems. See also Rule 238B.) Vertical clearance Supply voltage (kV) (m) (in) 1. Grounded conductor and messenger 0.75 30 hardware and supports 2. 0 to 8.7 1.00  40  3. Over 8.7 1.00 plus 0.01 per kV  40 plus 0.4 per kV  in excess of 8.7 kV in excess of 8.7 kV Where non-current-carrying parts of supply equipment are effectively grounded and the associated neutral meeting Rule 230E1 or supply cables meeting Rule 230C1 (including the support brackets) are bonded to communication messengers at intervals meeting Rule 092C through out well-defined areas and where communication is at lower levels, clearances may be reduced to 0.75 m (30 in). Table 238-2—Vertical clearance of span wires and brackets from communication lines and equipment (See also Rule 238C.) Carrying luminaires, traffic signals, or trolley conductors Not effectively grounded Effectively grounded (mm) (in) (mm) (in) Above communication support arms 1000 40 500 20  Below communication support arms 1000 40 600 24 Above messengers carrying communication cables 1000 40 100 4 Below messengers carrying communication cables 1000 40 100 4 From terminal box of communication cable 1000 40 100 4 From communication brackets, bridle wire rings, or 1000 40 100 4 drive hooks This may be reduced to 300 mm (12 in) for either span wires or metal parts of brackets at points 1.0 m (40 in) or more from the structure surface. 190 Copyright © 2016 IEEE. All rights reserved. 239 Part 2: Safety Rules for Overhead Lines 239D1 239. Clearance of vertical and lateral facilities from other facilities and surfaces on the same supporting structure Vertical and lateral conductors shall have the clearances required by this rule from other facilities or surfaces on the same supporting structure. A. General 1. Grounding conductors, surge-protection wires, neutral conductors meeting Rule 230E1, insulated communication conductors and cables, supply cables meeting Rule 230C1 or 350B, insulated supply cables of 0 to 750 V, or conduits may be placed directly on the supporting structure. These conductors, wires, cables, and conduits shall be securely attached to the surface of the structure. Cables not in conduit shall be installed in such a manner as to avoid abrasion at the point of attachment. 2. Installation of supply cable and communication cable in same duct or U-guard type covering a. Supply cables 0 to 600 V may be installed together in the same duct or U-guard, if all of the cables are operated and maintained by the same utility. b. Supply cables exceeding 600 V meeting Rule 230C1 or 350B may be installed together in the same duct or U-guard if all of the cables are operated and maintained by the same utility. c. Supply cables 0 to 600 V and supply cables exceeding 600 V meeting Rule 230C1 or 350B may be installed together in the same duct or U-guard if all of the cables are operated and maintained by the same utility. d. Supply cables shall not be installed in the same duct or U-guard with communication cables unless all of the cables are operated and maintained by the same utility. e. Communication cables may be installed together in the same duct or U-guard provided all utilities involved are in agreement. 3. Paired communication conductors in rings may be attached directly to a structure or messenger. 4. Insulated supply circuits of 600 V or less and not exceeding 5000 W may be placed in the same cable with control circuits with which they are associated. 5. The term nonmetallic covering as used in Rule 239 refers to material other than a cable jacket that provides an additional barrier against physical contact. 6. Where guarding and protection are required by other rules, either conduit or U-guards may be used. B. Location of vertical or lateral conductors relative to climbing spaces, working spaces, and pole steps Vertical or lateral conductors shall be located so that they do not obstruct climbing spaces, or lateral working spaces between line conductors at different levels, or interfere with the safe use of pole steps. EXCEPTION: This rule does not apply to portions of the structure that workers do not ascend while the conductors in question are energized. NOTE: See Rule 236H for vertical runs in conduit or other protective covering. C. Conductors not in conduit Conductors not encased in conduit shall have the same clearances from conduits as from other surfaces of structures. D. Guarding and protection near ground 1. Where within 2.45 m (8 ft) of the ground, or other areas readily accessible to the public, all ver- tical conductors and cables shall be guarded. EXCEPTION: This guarding may be omitted from grounding conductors used to ground multi-grounded circuits or equipment (communications or supply); communication cables or conductors; armored cables; or conductors used solely to protect structures from lightning. 191 Copyright © 2016 IEEE. All rights reserved. 239D2 Part 2: Safety Rules for Overhead Lines 239F2 2. Where guarding is required by Rule 239D1, either conduit or U-guards may be used. A backing plate shall be used with a U-guard unless the U-guard fits tightly to the supporting structure surface. 3. When guarding is not required, conductors and cables shall be securely attached to the surface of the structure or to standoff brackets and located, where practical, on the portion of the struc- ture having the least exposure to mechanical damage. 4. Guards that completely enclose grounding conductors of lightning-protection equipment shall be of nonmetallic materials or shall be bonded at both ends to the grounding conductor. E. Requirements for vertical and lateral supply conductors on supply line structures or within supply space on jointly used structures 1. General clearances In general, clearances shall be not less than the values specified in Table 239-1 or Rule 235E. 2. Special cases The following requirements apply only to portions of a structure that workers ascend while the conductors in question are energized. a. General If open-line conductors are within 1.20 m (4 ft) of the pole, vertical conductors shall be run in one of the following ways: (1) The clearance between open vertical conductors and pole-surface shall be not less than that given in Table 239-2 within the zone specified in the table. (2) Within the zone above and below open supply conductors as given in Table 239-2, vertical and lateral conductors or cables attached to the surface of the structure shall be enclosed in nonmetallic conduit or protected by non-metallic covering. EXCEPTI