Functions
2.2 Overcurrent Protection 50, 51, 50N, 51N
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
82
Figure 2-16 Reverse interlocking protection scheme
2.2.11 Setting Notes
General
When selecting the time overcurrent protection in DIGSI a dialog box appears with several tabs, such as , , , ,
and in which the individual parameters can be set. Depending on the functional scope specified during config-
uration of the protective functions in addresses 112 Charac. Phase and 113 Charac. Ground the number
of tabs can vary. If address FCT 50/51 was set to Definite Time, or Charac. Ground was set to
Definite Time, then only the settings for the definite time elements are available. The selection of TOC IEC
or TOC ANSI makes additional inverse characteristics available. The superimposed high-set elements 50-2,
50-3 and 50N-2, 50N-3 are available in all these cases.
Parameter 250 50/51 2-ph prot can also be set to activate two-phase overcurrent protection.
Under address 1201 FCT 50/51, overcurrent protection for phases and under address 1301 FCT 50N/51N,
the ground overcurrent protection can be switched ON or OFF.
Pickup values, time delays, and characteristics for ground protection are set separately from the pickup values,
time delays and characteristic curves associated with phase protection. Because of this, relay coordination for
ground faults is independent of relay coordination for phase faults, and more sensitive settings can often be
applied to directional ground protection.
Depending on the setting of parameter 251 CT Connect., the device can also be used in specific system
constellations with regard to current connections. Further information can be found under Section 2.1.3.2 ,
„Current Connections“.
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