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Page 193

Figure 10-16
Load-interrupting device for air-break switch: (A) Switch in closed
position; (B) beginning of opening cycle with by-pass switch still
engaged to prevent arcing; (C) by-pass switch disengaged with
current path now directed through activating arm; (D) completed
load-break cycle with switch blade open.

| The ground leads should be placed and removed with the use of rubber gloves, insulated switch sticks, or both. |

| As a further safety measure, it might be wise to check all the de-energized circuit conductors, switch terminals, and other parts involved in the work with a voltage detecting device prior to applying grounds (Fig. 10-17). |

| Both air and oil switches should be capable of being locked in either the open or closed position, and provision is often made for more than one lock to be employed at the same time (Fig. 10-18). |

| Equally important as all of the physical and electrical preparations involved in operating these switches is the supervision of the activities of the personnel associated with them. Work on lines or equipment, especially the operation of air and oil switches as well as the placing and removing of protective grounds, should always be coordinated by one responsible person. Their job is to see that all necessary steps are executed properly and in correct sequence. It is they who give the orders for circuit breakers and switches to be opened or closed and to be locked in the appropriate position. They must make sure that proper notices are displayed at the breakers, switches, lines, and equipment involved (Fig. 10-19). The workers responsible for the work to be done on the lines or equipment not only receive their orders from the coordinator but must also inform him of the completion of each instruction. As a further safety precaution, orders and instructions must be put in written form. Those given by telephone must be written down by both coordinator and worker and repeated back to the other to avoid error. These written orders and instructions, as well as reports of the completion of each order, become part of a permanent record that can be analyzed for possible improvements in safe operating practices and for investigating events should something go wrong despite the precautions taken. |

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