The accident site in the Sierra Nevada foothills.Cable (left) and phone (right) connections at point of incidentShowing wiring (bottom to top) telephone, cable, and high voltage wiring.A 12,000 volt insulator cracked, allowing current to flow down the pole.The cable guy's work site and the isolating insulator.Scale drawing explaining code requirements.

 

CASE STUDY

The Cable Guy Gets Shocked!

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Challenge

A cable technician working atop a ladder grasped his company’s grounded bare steel cable “messenger” (support) wire simultaneously while placing his other hand on a pole-to-ground bare guying cable owned by the electric power company; each wire was installed on a utility pole of shared ownership. The cable guy received a shock greater than the human “let-go” threshold, i.e., he was locked on to the wires. His yell attracted his supervisor who offered to climb up the ladder, 18 feet, and somehow rescue him. The cable guy declined fearing that his boss would also get shocked. Instead he kicked his ladder out allowing his body to fall. Fortunately the resulting descending momentum pulled him off the wires and terminated the shock incident. Unfortunately the subsequent 18 foot fall caused multiple breaks in his ankles.

 

As an employee on the job, his medical costs and lost wages were covered by worker’s compensation insurance. Often that coverage is deemed inadequate, or the worker’s comp carrier initiates a subrogation claim, if there is an eligible defendant who might have liability for the injury. In this case an action was initiated against the electrical power company on behalf of the cable guy; that required electrical expertise.

 

 

 

Process

The basic story was obtained from the retaining attorney. Then documents relevant to the case were reviewed. No site visit occurred because the case was already years old and the power pole scene had been repaired and otherwise changed. There were adequate photos to determine the cause of the accident and, along with some geometric calculations and reference to the appropriate overhead line construction standards (G.O. 95), a power company design and/or construction error was identified and a report produced.

 

 

Resolution

G.O. 95 requires specific insulator locations to prevent exactly the injury received by the cable guy. It is known that the high voltage (12kV) insulators mounted several feet above the communications wires (phone and cable) can crack due to weather or manufacturing anomalies and allow electrical current to leak into the bare guy wires that run from near the insulators on top, down to the earth, creating a shock hazard.

 

Two sectionalizing insulators must be placed in this downward guy wire to preclude such a shock, or electrocution, for both pedestrians on the ground and cable guys working above on communication cables. It was shown with a scale drawing that one of these insulators was several feet out of specification and the other was missing. This error allowed the shock and was the direct cause of the incident.

 

 After reviewing the report the utility company produced a satisfying settlement for the plaintiff.

 

 

SPECIALTIES

Fire Cause and Origin

Power Wiring and Circuits

Alarms

Controls

Machinery

Vehicles

Grounding

National Electrical Code (NEC)

General Order 95

Troubleshooting

Electrician Trade Practice

Lock Out / Tag Out

 

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