GE Power ManagementL90 Line Differential Relay2-92 PRODUCT DESCRIPTION 2.3 PROTECTION & CONTROL FUNCTIONS22.3 PROTECTION & CONTROL FUNCTIONS 2.3.1 CURRENT DIFFERENTIAL PROTECTIONThe current differential algorithms used in the L90 Line Differential Relay are based on the Fourier transform “phaselet”approach and an adaptive statistical restraint. The L90 uses per phase differential at 64 kbps with 2 “phaselets” per cycle.A detailed description of the current differential algorithms is found in the THEORY OF OPERATION chapter. The currentdifferential protection can be set in a percentage differential scheme with a single or dual slope.2.3.2 BACKUP PROTECTIONIn addition to the primary current differential protection, the L90 Line Differential Relay incorporates backup functions thatoperate on the local relay current only, such as directional phase overcurrent, directional neutral overcurrent, negativesequence overcurrent, undervoltage, overvoltage, and distance protection.2.3.3 MULTIPLE SETTINGS GROUPSThe relay can store 8 sets of settings. They may be selected by user command, a configurable contact input or a Flex-Logic™ equation to allow the relay to respond to changing conditions.2.3.4 USER PROGRAMMABLE LOGICIn addition to the built-in protection logic, the relay may be programmed by the user via FlexLogic™ equations.2.3.5 CONFIGURABLE INPUTS AND OUTPUTSAll of the contact converter inputs (Digital Inputs) to the relay may be assigned by the user to directly block a protection ele-ment, operate an output relay or serve as an input to FlexLogic™ equations. All of the outputs, except for the self test criti-cal alarm contacts, may also be assigned by the user.
