Document Rp4oZ50j7Ln1wK0292rMYK8OV

ELECTRICAL HAZARDS Test equipment Most electrical equipment is designed for safe operation un der limited overload conditions for varying periods of time. Op erators should be thor oughly familiar with the limitations of their equipment and should be trained to observe and report abnormal oondibons Continued overload may intro duce additional oper ating hazards by caus ing fire, short circuits, circuit failures, or ma chine failures Through the use of various types of elec trical testing meters, many of these condi tions can be detected before they get out of control and cause Hg. 31-8. An electrician checking equipment with on insulation damage resistance tester His findings will be recorded on a chart The following types similar to thot shown In Fig 31-9 of equipment are standard and should Courtesy Associated Research, /nc be considered even by plants with limited budgets split-core am ure voltage and an ammeter to measure meter, voltmeter, ammeter, megohmmeter, current When these two instruments are ground fault indicators and locators, watt used, more accurate readings can be taken meter, industrial analyzer, recording instru Also separate instruments are useful when ment, and specialized testing instruments simultaneous voltage and current readings The split-core ammeter can be used with out tapping into the circuit The instru ment's core is slipped around the electnc leads, and the scale is then read for the are needed Such readings might be neces sary when tests are being made to check on voltage surges or dips and unusual power conditions while current is on amount of current flow A current read When the current to be measured exceeds ing in excess of the rated full-load current the ammeter's range, shunts should be used gray indicate an overload or a grounded They are generally limited to direct current motor winding. instruments and to current transformers for When test leads are used with this instru alternating current measurement Likewise, ment, the line voltage can be checked to see when voltages exceed the voltmeter's maxi if it equals the motor voltage rating This mum rating, resistors or potential trans check is important because low voltage can formers must be used to step down voltage cause excessive current flow which may re The megohmmeter ("megger") is a high- sult in a complete breakdown, arcing, or scale ohmxneter which gives the value of electrical fires insulation resistance Almost every wire in Voltmeter and ammeter When the voltage a plant (including the wires on motors, gen and current used in a plant exceed the range erators, and transformers) is wrapped in of a split-core ammeter, separate instru electrical insulation ments should be used a voltmeter to meas- Not all electrical insulation provides a 31-17