Document Lpd5jp72m1JKEnxERrG4nLakQ

ELECTRICAL HAZARDS essential indicators in the circuit Thermo couples or other thermometers are some times provided These indicators provide for safer operation since the characteristics of the apparatus can be constantly observed and men need not make separate tests near energized circuits When high-voltage equipment not equipped with built-in indicators must be in spected, the operator or inspector should examine it carefully to see that it has a sub stantial ground An electrical fault m an ungrounded machine may not be visible dur ing operation, but touching the frame may result in fatal shock A good ground will keep the machine at or near earth potential. Power factor improvement capacitors are used in almost every efficiently operated dis tribution system These capacitors usually have an internal discharge resistor to re duce the voltage to 50 volts within 5 min utes after the capacitor is deenergized Nev ertheless, each terminal and the case must be grounded by means of a grounding stack whenever work is to be done on or near the capacitor This ground connection must be maintained until the entire job inspection, maintenance, or cleaning of the capacitor-- has been completed Extreme precaution should be taken when insulation resistance of high-voltage equip ment is tested to make sure that the megohmmeter is not connected into a live cir cuit After it has been determined that the apparatus is completely dead, the free test lead can be attached to an exposed connec tion by use of a switch hook or other type of insulated hot stick Rubber gloves should be worn in case of hand contact with the hanging leads. Contact to test insulation resistance should be made whenever possible with an exposed conductor in the circuit to be test ed Puncturing of insulation is not recom mended except with the knowledge and per mission of the plant electrician, engineering department, or operator Then it should be understood that the place punctured will be immediately taped or reinsulated As assurance of additional safety, espe cially when the punctured insulation is near metal framework or grounded structures, an insulation test should be made of the taped portion. Rubber gloves should not be used as a substitute for safety devices or procedures, but are worn as a supplementary measure Before each use they should be checked for punctures, tears, or abrasions For an onthe-job test the cuffs should be rolled up and air forced into the fingers and palms of the gloves If there is leakage, the gloves should not be used Leather protectors should be worn over rubber gloves to protect the rubber from mechanical damage and from oil and grease An electrical glove testing service should he provided, with regular testing intervals determined by the amount of use of the gloves, the type of work, and the voltages they are subject to If there is doubt about the insulating quality of the gloves, they should not be used Private testing laboratories can be relied upon for accurate testing In some cases they will keep individual company records on the physical condition of gloves and the tune schedule for retesting Where no lab oratory is available, small concerns can usu ally get tests made at the local public utility Maintenance To be safe and to give the best service, electric equipment must he well-maintained Motors, circuit breakers, moving parts of switches, and similar current-carrying de vices wear out, break down, and need re adjustments Repairs on electrical circuits and electrical apparatus should be made only by experienced electncians (Fig 31-13) Only high-grade electncal equipment list ed as standard by Underwriters' Laboratones, Inc, or other qualified authority, should be used in maintenance work In ferior, unapproved equipment may become hazardous because of defective material or design or poor workmanship If practicable, conductors should be de energized when maintenance work on them is necessary Before they begin work, mam tenance men should make certain that the line is dead by testing it with the voltage testing devices provided It is not safe to test a circuit with the fingers or with make shift devices The men should be instructed in the use of electncal testing equipment and meters how to tap into the circuit, how to locate testing pomts from schematic diagrams, how to use insulated meter leads, dips, and 31-24