Functions
2.7 Negative Sequence Protection 46
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
152
Settable Dropout Times
Pickup stabilization for the definite-time tripping characteristic 46-1, 46-2 can be accomplished by means of set-
table dropout times. This facility is used in power systems with possible intermittent faults. Used together with
electromechanical relays, it allows different dropout responses to be adjusted and time grading of digital and
electromechanical relays to be implemented.
2.7.2 Inverse Time Characteristic 46-TOC
The inverse time element is dependent on the ordered device version. It operates with IEC or ANSI character-
istic tripping curves. The curves and associated formulas are given in the Technical Data. When programming
the inverse time characteristic also definite time elements 46-2 PICKUP and 46-1 PICKUP are available (see
aforegoing paragraph).
Pickup and Tripping
The negative sequence current I2 is compared to the setting value 46-TOC PICKUP. When the negative se-
quence current exceeds 1.1 times the setting value, a pickup annunciation is generated. The tripping time is
calculated from the negative sequence current according to the characteristic selected. After expiration of the
time period a tripping command is output. The characteristic curve is illustrated in the following figure.
Figure 2-50 Inverse time characteristic for negative sequence protection
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