Encyclopedia of Grounding (CA09040E)

GENERAL INSTALLATION PROCEDURES FOR PERSONAL PROTECTIVE JUMPERS

General guidelines only are presented here. A discussion of some of the applications peculiar to specific situations is presented later. 1. Verify the line is truly de-energized: [OSHA 1910.269] Beforeapplyinganyprotective jumpers, the status of the linemust bedetermined. Several techniques are available. A common field technique is “fuzz ing” or “buzzing” the line by holding a wrench mounted on an insulated “hot stick” or the metal head of a Universal Tool near the conductor. The theory is that if the line is energized it will induce a voltage in the wrench or metal head and corona discharges will cause an audible sound. “Fuzzing” is not a recommended technique. The detection of any audible sound is very subjective and is dependent upon wind conditions, line volt age level, nearby noise levels, etc. It is reported to be more reliable on transmission lines because of their higher voltages, but the use of a detector designed for the purpose increases the level of safety. Chance offers several models of the Multi Range Voltage Detector and Phasing Tools that can be employed to significantly increase the reliability of this determination. See Section 8 for a discussion of these devices. Protective equipment can be installed once the line has been de-energized and the absence of voltage has been verified. All of the connections shouldbemade toa cleaned surface. Either a wire brush or serrated jaw clamp can be used on distribution voltage level conduc tors. On high voltage transmission towers only the wire brush is recommended. Use of the serrated jaw clamp may leave sharp edges on the soft alu minum conductor that could result in increased corona discharge. 2. Clean the connections:

the connection. Fault current passing through a layer of paint that separates the clamp from the tower steel will cause it to heat and soften, melt or burn away. A flat face clamp could lose its grip andcomeoff the tower, breakinga connectionand possibly losing the protective parallel path. It may be desirable to tie the clamp to the tower steel to prevent it from coming off and to avoid the loss of protection fromthese hazards. Locate each clamp to maximize worker safety. The added resistance of a corroded connection may increase that of the parallel path as to jeopardize worker safety. 3. Order of installation of personal protective jumpers: [OSHA 1910.269] Install the personal protective jumpers using an insulated Grip-All clampstick. Begin by connect ing a ground end clamp to an appropriate Earth connection. Per the OSHA acceptable methods of grounding for employers that do not perform an engineering determination found in 1910.269 Appendix C, the circuit should be grounded to the best ground available at the worksite as follows: • Must ground to system neutral if present • Ground to substation grid in a substation • Ground to remote ground when lower impedance grounds are not available • Ground to temporary driven ground if above 3 are absent It is important that a pole down wire not be used for this connection. The small size of a pole down wire could cause it to fuse and melt during the flow of fault current, resulting in the loss of the connection for the Earth return path. For wooden poles, the line end clamp should then be installed onto a cluster bar attached around the pole as close as possible below the location of the worker’s feet. The cluster bar provides a conductive connection point for use with multi ple clamps and a convenient parking location for clamps during installation. The cluster bar also provides the bond to the pole, and per the OSHA acceptable methods of grounding for employers

For tower connections it may be necessary to clean away paint, rust or corrosion before making

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ENCYCLOPEDIA OF GROUNDING