Landscaping (C-27) · Lesson 6 of 7

Tree Work Near Power Lines: The 10-Foot Rule and Who May Cross It

"Tree Work Near Power Lines: The 10-Foot Rule and Who May Cross It" is lesson 6 of 7 in the Landscaping (C-27) Learning Hub. It opens with "Treat Every Overhead Line as Live" and works through 5 short steps, then a worked example you can check yourself against.

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Steps in this lesson

  1. Treat Every Overhead Line as Live
  2. The 10-Foot Rule for High Voltage
  3. Low Voltage: Inside 10 Feet but Never Inside 1 Foot
  4. Line-Clearance Work Belongs to Qualified Line-Clearance Trimmers
  5. Equipment and Tools Have Their Own Table

The worked example in the course applies this lesson to a realistic job in 4 steps.

What you'll be able to do

  • Explain the main idea of "Tree Work Near Power Lines: The 10-Foot Rule and Who May Cross It" in plain language you can use on the exam.
  • Apply this step with confidence: "Low Voltage: Inside 10 Feet but Never Inside 1 Foot".
  • Apply this step with confidence: "Line-Clearance Work Belongs to Qualified Line-Clearance Trimmers".
  • Apply this step with confidence: "Equipment and Tools Have Their Own Table".
  • Test yourself on the worked example and the quick-check quiz inside the classroom.
Tree Work Near Power Lines: Who Goes How CloseOVER 600 V (e.g., a 12 kV line)8 ftdashed ring = 10 ft8 ft is inside 10 ft: STOP600 V OR LESS (e.g., 240 V service drop)3 ftdashed ring = 10 ftred ring = 1 ft3 ft: qualified tree worker onlyHOW CLOSE? (8 CCR)Over 600 V, within 10 ftLine-clearance tree trimmers or trainees only(3423(b)(1), (c); 2951(b))600 V or lessQualified tree worker may work within 10 ftbut never closer than 1 ft (3423(b)(2))Table 1, Sec. 2950 (all other persons)0 to 50 kV: 10-0050.1 to 72.5 kV: 10-0972.6 to 121 kV: 12-04138 to 145 kV: 13-02Proximity (Sec. 3420(b))10 ft to 50 kV, plus 4/10 in. per kV above 50115 kV: (115 - 50) x 0.4 = 26 in. = 2 ft 2 in.10 ft + 2 ft 2 in. = 12 ft 2 in.Table 1 prints 12-04 for the 72.6 to 121 kV bandPlan on the printed table value: 12 ft 4 in.No metal-core rope near conductors (3423(d))12 kV limb at 8 ft: STOP - call line-clearance trimmers.240 V limb at 3 ft: qualified tree worker only, never inside 1 ft.Source: 8 CCR Sec. 3420(b), 3423, 2946, 2950 (Table 1), 2951.CC
The diagram for this lesson, exactly as it appears in the Learning Hub.

The first steps of this lesson

Step 1: Treat Every Overhead Line as Live

Cal/OSHA's tree-work rules start with training: workers near electrical equipment and conductors must be instructed to consider all of it energized with potentially fatal voltages, never to touch it directly or indirectly, and to understand that shock can come from contact with a conductor, an energized limb, a tool, or a grounded object, or from step potential near a downed conductor (8 CCR Sec. 3423(a)). Under the electrical orders, an overhead conductor is considered energized unless and until the owner verifies it is not and it is visibly grounded at the work site (8 CCR Sec. 2946(d)). Wet or contaminated rope that is not insulating for the voltage must not be used near exposed energized lines (8 CCR Sec. 2951(i)(2)).

Step 2: The 10-Foot Rule for High Voltage

Employees shall not perform tree trimming within 10 feet of high-voltage energized power lines unless they meet the line-clearance requirements (8 CCR Sec. 3423(b)(1)). The tree-work standard defines 'Proximity' as within 10 feet of overhead conductors rated 50 kV phase to phase or less; above 50 kV the distance grows 4/10 inch (10 mm) for each additional kV (8 CCR Sec. 3420(b)). The High-Voltage Electrical Safety Orders print the minimum approach distance for persons other than qualified line-clearance tree trimmers in Table 1 of Sec. 2950: 10-00 for 0.0 to 50.0 kV, 10-09 for 50.1 to 72.5 kV, 12-04 for 72.6 to 121.0 kV, and 13-02 for 138 to 145 kV.

The remaining 3 steps, the worked example and the quiz are in the course. This is a preview. The full lesson, with the step-by-step explanations, a worked example and a quick-check quiz, is inside the classroom.

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