IEEE 62-1978 pdf free.IEEE Guide for Field TestingPower Apparatus Insulation.
This guide discusses the significance of varioustypes of tests commonly employed to evaluatethe insulation of power apparatus in the field,where environmental conditions cannot readilybe controlled;the equipment and techniquesrequired for each type of test; problems peculiarto field testing,and methods of dealing withthese problems; and the application of fieldtests to specific types of power apparatus.
2.1 Hazards. Insulation tests in the fieldcan present a hazard to personnel unless suitable precautions are taken. Apparatus or circuits to be made available to test personnelmust be disconnected from the power system.Typical safety procedures call for a visualcheck of the disconnection or, when this is notpossible,a check with a voltage indicator.Grounds are then applied. Personnel are usuallyinstructed to treat all ungrounded apparatus asenergized.
Ground Connection.Grounds may beremoved to permit application of test voltage.When feasibie,it is preferable to retain theground connection during the tests and to provide between the ground and the apparatusunder test a second disconnection of sufficientclearance for the test voltage (see 6.8.3.2).
Precautions. When the test voltage isover a few volts，precautions should be takento prevent personnel from contacting the ener-gized circuit. An observer may be stationed towarn approaching personnel and may be sup-plied with means to deenergize the circuit.Themeans may include a switch to shut off thepower source and, particularly in case of a direct test voltage，provisions for grounding thecircuit until all stored charges are dissipated.
Warning Signs and Barriers.The testarea may be marked off with signs and easilyvisible tape. Warning signs should conform tothe requirements of governing bodies such asthe Occupational Safety and Health Adminis-tration (OSHA) in the United States.
2.2 Consequences of Failure. When the testvoltage to be applied to apparatus insulationexceeds the normal operating value，thereexists the possibility of failure under test. Be-fore applying the test,consideration should begiven to the time, material,and labor requiredfor a possible repair. If failure could result infire,firefighting equipment should be available. Overvoltage. In the conduct of high-voltage tests the voltage may accidently exceed
the desired maximum. A sphere gab.adiustedto spark over at a voltage slightly above the de-
sired maximum,may be connected across thevoltage source. By selecting the proper value ofseries resistor, the gap may be used to provide awarning signal, to inhibit further rise in the testvoltage，or to activate an overcurrent circuitbreaker in the power supply circuit.
Graded Insulation. When an alternatingtest voltage is applied to a shortcircuitedwinding,or when a direct test voltage is used,the insulation of the entire winding is subjectto this test voltage. When the insulation level ofthe winding is graded from one end to theother，the magnitude of the applied test voltage should correspond to the lowest insulationlevel.IEEE 62 pdf download.