GE F60 Instruction Manual page 357

5 SETTINGS
• HI-Z LOSS OF LOAD THRESHOLD: Establishes the loss of load level used as an indication of a downed conductor. A
Loss of Load flag is set if the Hi-Z algorithms detect a percentage drop in phase current between two successive two-
cycle RMS values that equals or exceeds the Loss of Load Threshold. The amount the phase current must decrease
between successive two-cycle RMS values is based on this setting times the recent average phase current level. The
range is 5 to 100%; 5% being the most sensitive.
• HI-Z 3-PHASE EVENT THRESHOLD: Establishes the level at which the Hi-Z element characterizes a sudden three-
phase current increase as a three-phase event. The Hi-Z detection algorithms ignore the data generated by a large
three-phase event. The recommended setting is 25 A (primary).
• HI-Z VOLTAGE SUPV THRESHOLD: In the event that a fault simultaneously occurs on two adjacent feeders (line
voltage from the same bus), the drop in line voltage will cause a subsequent drop in load current. This function will
block the Loss of Load flag from being set while the voltage is depressed. Thus, if the voltage level drops by a percent-
age greater than this threshold in successive two-cycle RMS samples, the Loss of Load flag will be blocked. If the set-
ting is "0", the voltage supervision function will be disabled.
• HI-Z VOLTAGE SUPV DELAY: This setting adds time delay to the voltage supervision function. Specifically, the Loss
of Load flag will continue to be blocked for the number of cycles specified by this setting.
• HI-Z EVEN HARMONIC RESTRAINT: This setting determines the level of the even harmonic at which the setting of
the overcurrent flags is inhibited. The even harmonic content is evaluated on each phase current as a percentage of
that phase's RMS current. The intent is to inhibit the setting of the overcurrent flags if the overcurrent is simply a surge
caused by cold-load pickup or other inrush event.
IMPORTANT NOTE REGARDING INSTALLATION: The F60 Hi-Z algorithm is adaptive in nature. The algo-
rithm's internal thresholds gradually adapt to background "noise" on circuits with a moderate to high level
NOTE
of transient activity. For the first three to five days after installation (or after being out-of-service for a sig-
nificant period), the F60 may identify some of this noise as arcing. This should be taken into account when
responding to alarms during these type of operating periods.
GE Multilin F60 Feeder Protection System
5.7 CONTROL ELEMENTS
5-217
5