GE Multilin 745 Instruction Manual

Protection Schemes 745Transformer Management RelayCommissioninghttp://www.GEindustrial.com/multilin 7ñ27GE MultilinRestricted Ground FaultElement Testa) DescriptionThis procedure verifies that the Restricted Ground Fault performance matches thein-service settings. The ground element measures the current signal connected tothe ground current input CT, H10 and G10 or F12 and E12. The neutral (3Io ) currentis calculated from the vector sum of the three phase currents. Injecting current intoone phase automatically produces a neutral current (i.e. 3Io = I A). Settings forthese elements are found in the S4 ELEMENTS !" RESTRICTED GROUND !" W1(3) RESTDGND FAULT setpoints menu.b) Winding 1 ElementTo ensure that only the Restricted Ground Fault element operates the trip relays(and any other output relays selected by the logic) disable all protection featuresexcept Restricted Ground Fault.Using a current supply as shown in the figure below, connect the I1 current sourceto terminals H1 and G1 for the Winding 1 phase current element and I2 to terminalsG10 and H10 as shown for the ground current element. Monitor the appropriateoutput relays as per the relay FlexLogicô settings.FIGURE 7ñ11: Restricted Ground Test Setupc) Pickup Level1. With the interval timer disabled, apply the current signal feeding the phase cur-rent element and increase its magnitude slowly until the trip relay, and all theselected auxiliary relays, operate. The operate level should correspond to the S4ELEMENTS !" RESTRICTED GROUND ! W1 RESTD GND FAULT !" W1 RESTD GND FAULTPICKUP setting.2. When the element operates, check that the Trip, Ground, and Pickup LEDs areon and that one of the following messages is displayed:LATCHED a: W1 Restd Gnd Fault or OPERATED a: W1 Restd Gnd Fault3. 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 RESTD GND FAULT TARGET was selected as ìLatchedî.Otherwise, only the Trip LED should remain on.4. Reset indicators and clear messages.d) Operating TimeSelect three (3) or four (4) delay times at which the timing is to be measured. Withthe Interval Timer enabled, set the current level to the desired value and applysuddenly by closing the double-pole switch. Record the operate time and compareto the expected value. Repeat for the all the desired values of current.