GE Multilin 745 Instruction Manual

Protection Schemes745Transformer Management RelayCommissioninghttp://www.GEindustrial.com/multilin7ñ24 GE Multilinc) Pickup Level1. With the interval timer disabled, apply the current signal and slowly increase itsmagnitude until the trip relay (and all the selected auxiliary relays) operate.2. If the relay has a very inverse time characteristic, it is easier and more accurateto increase the current far above the pickup level until the trip relay operatesand then reduce the current to just above the operate level. Then slowly reducethe current below the operate level and observe for a reset action on the triprelay. This reset level for the current should be approximately 98% of thepickup level. Once the relay drops out, slowly increase the current until the tripcontact closes. The operate level should correspond to the S4 ELEMENTS !"GROUND OC ! W1 GND TIME OC !" W1 GROUND TIME OC PICKUP setpoint.3. When the element operates, check that the Trip, Ground, and Pickup LEDs areon and one of the following messages is displayed:LATCHED a: W1 Gnd Time OC or OPERATED a: W1 Gnd Time OC4. Reduce the current until the element resets. The reset level should be 97% ofthe operate level. When the element resets the Trip and Message LEDs shouldremain on if the W1 GROUND TIME OC TARGET was selected as ìLatchedî.Otherwise, only the Trip LED should remain on.5. Reset indicators and clear messages.d) Operating TimeUsing a table like the one shown blow, select three (3) or four (4) values of currentmultiples at which the timing is to be measured. Enter the expected operating timesfrom the timing curve applied in the settings. Using FIGURE 7ñ9: General Test Setupon page 7ñ18 with the Interval Timer enabled, set the current level to the desiredvalue and apply suddenly by closing the double-pole switch. Record the operatetime and compare to the expected value. Repeat for the all the desired values ofcurrent.e) Reset TimeA precise measurement of the reset time requires a relay test set capable ofdynamic operation, with three sequenced stages, each with programmable currentlevels and time duration, and flexible external contact triggering. To perform such atest, contact GE Multilin for detailed test instructions.A simple verification of the reset mode selected with the S4 ELEMENTS !" GROUND OC! W1 GND TIME OC !" W1 GROUND TIME OC RESET setpoint is obtained using the setupin FIGURE 7ñ9: General Test Setup on page 7ñ18. The procedure consists ofrepetitive operating time measurements in quick succession. If the reset is selectedfor ìInstantaneousî, the operating time always equals the nominal time derivedfrom the selected curve. If the reset is selected as ìLinearî, the operating timevaries as a function of the time between successive applications of the currentsignal. If this test is performed at current multiples of 2 to 3 times the pickup level,the variations in operating time are easier to detect.f) Winding 2 or 3 ElementsBecause the second Ground Time Overcurrent element could be set with completelydifferent parameters than the element for the first winding, it is necessary to repeatthe full set of tests described above for each winding.CURRENTMULTIPLENOMINALTIMEMEASUREDTIME1.535