Protection & Control Functions; Current Differential Protection; Backup Protection; Multiple Settings Groups - GE UR Series Instruction Manual

2 PRODUCT DESCRIPTION 2.3 PROTECTION & CONTROL FUNCTIONS
2.3 PROTECTION & CONTROL FUNCTIONS

2.3.1 CURRENT DIFFERENTIAL PROTECTION

The 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 current
differential protection can be set in a percentage differential scheme with a single or dual slope.
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2.3.2 BACKUP PROTECTION

In addition to the primary current differential protection, the L90 Line Differential Relay incorporates backup functions that
operate on the local relay current only, such as directional phase overcurrent, directional neutral overcurrent, negative
sequence overcurrent, undervoltage, overvoltage, and distance protection.

2.3.3 MULTIPLE SETTINGS GROUPS

The 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 LOGIC

In addition to the built-in protection logic, the relay may be programmed by the user via FlexLogic™ equations.

2.3.5 CONFIGURABLE INPUTS AND OUTPUTS

All 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.
GE Power Management L90 Line Differential Relay 2-9