Eaton Cooper Power NR Series Maintenance Instructions Manual

Contents

Manual operationThe switch may be manually opened and closed by operat-ing the yellow handle under the sleet hood.ote:N Manual operation does not affect the status of theelectrically operated actuator. To electrically closea switch which has been manually opened, theelectrical open circuit must be first activated tochange the status of the selector switch for a closeoperation.Oil conditionOil plays an important role in the proper functioning ofthe switch. It provides the internal insulating barrier fromphase to ground, and acts as an arc quencher. Switchingoperations cause reductions of some of the oil intochemical compounds, free carbon and gases. Some ofthese compounds form water-absorbing particles whichreduce the dielectric strength of the oil. For effective switchoperation the oil must be replaced before it deterioratesbelow a safe level. Oil that has been contaminated withcarbon sludge or has a dielectric strength of less than 22 kVshould be replaced.Used oil must be reconditioned before using. Filtering mayremove absorbed and free water, and other contaminants toraise the dielectric strength to an acceptable level. However,it does not always remove water-absorbing contaminants.Thus, the dielectric strength of the oil may fall rapidly afterthe switch is returned to service. Therefore the switchshould be filled with new oil or oil that has been restored tolike-new condition. Oil used in these switches conforms toASTM Standard D3487, Type 2; its property limits are listedin Reference Data R280-90-1, Oil Specifications and Tests.New oil should always be filtered before using eventhough it is obtained from an approved source. Passing oilthrough a blotter press will remove free water and solidcontaminants such as rust, dirt, and lint. When filteringthe oil, aeration should be kept to a minimum to preventmoisture in the air from condensing in the oil and loweringits dielectric strength.Insulation level withstand testsHigh-potential withstand tests provide information regardingthe dielectric condition of the switch. Testing is performed at75% of the rated low-frequency withstand voltage (Table 3).Test 1: Proceed as follows:1. Close the switch.2. Ground switch tank and head.3. Apply proper test voltage to one of the bushingterminals.• The switch should withstand the test voltage for 60seconds.Test 2: Proceed as follows:1. Open the switch.2. Ground switch tank and head.3. Ground the bushing on one side of the switch.4. Apply proper test voltage to the ungrounded bushing.• The switch should withstand the test voltage for 60seconds.5. Reverse the test and ground connections to thebushings.6. Again apply proper test voltage to the ungroundedbushing.• The switch should withstand the test voltage for 60seconds.Test results:These high potential withstand tests provide information onthe dielectric condition of the switch.1. If the switch passes the closed-contacts test (Test 1)but fails the open-contacts test (Test 2) the cause islikely to be in the main contact assembly.2. If the switch fails the closed-contacts test (Test 1) thecause is likely to be a diminished electrical clearance orfailed insulation.3. After correcting the problem, retest to confirm therepair.Table 3. Test Voltages for Insulation Level WithstandTestSwitch Type BIL (kV) Test Voltage (kV)NR 95 35.0NR* 125 42.0* Extra creepage bushings5TYPE NR OIL SWITCH MAINTENANCE INSTRUCTIONS MN230001EN February 2016