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CHAPTER 5: SETTINGS CONTROL ELEMENTS

L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL 5-385

Generally, this scheme uses an overreaching zone 2 distance element to essentially compare the direction to a fault at all

terminals of the line. Ground directional overcurrent functions available in the L90 can be used in conjunction with the

zone 2 distance element to key the scheme and initiate operation. This increases the coverage for high-resistance faults.

The scheme is intended for three-terminal and two-terminal applications with weak-infeed conditions. As a long reach of

the overreaching distance element can be required for three-terminal applications, transient blocking logic is provided for

both distance and ground directional overcurrent elements. In order to cope with weak-infeed conditions, an echo feature

is made available.

By default the scheme uses the reverse-looking zone 4 distance element to identify reverse faults. Additionally, reverse-

looking ground directional overcurrent functions can be used in conjunction with the zone 4.

For proper operation, the zone 2 and 4 phase and ground distance elements must be enabled, configured, and set per

rules of distance relaying. Enable the line pickup element, configure it, and set properly to detect line-end-open/weak-

infeed and undervoltage conditions. If used by the scheme, the selected ground directional overcurrent function(s) must be

enabled, configured, and set accordingly.



HYB POTT WEAK

INFEED: Enabled

Range: Disabled, Enabled, Custom



HYB POTT W/I COND:

Off

Range: FlexLogic operand



HYB POTT RX PICKUP

DELAY: 0.000 s