Siemens SIPROTEC 7SJ61

Functions
2.2 Overcurrent Protection 50, 51, 50N, 51N
SIPROTEC, 7SJ61, Manual
C53000-G1140-C210-1, Release date 02.2008
67
51 Element (phases) with IEC or ANSI characteristics
Having set address 112 Charac. Phase = TOC IEC or TOC ANSI when configuring the protection functions
(Section 2.1.1.2), the parameters for the inverse characteristics will also be available.
If address 112 Charac. Phase was set to TOC IEC, you can select the desired IEC characteristic (Normal
Inverse, Very Inverse, Extremely Inv. or Long Inverse) at address 1211 51 IEC CURVE. If
address 112 Charac. Phase was set to TOC ANSI, you can select the desired ANSI characteristic (Very
Inverse, Inverse, Short Inverse, Long Inverse, Moderately Inv., Extremely Inv. or
Definite Inv.) at address 1212 51 ANSI CURVE.
If the inverse time trip characteristic is selected, it must be noted that a safety factor of about 1.1 has already
been included between the pickup value and the setting value. This means that a pickup will only occur if a
current of about 1.1 times the setting value is present. If Disk Emulation was selected at address 1210 51
Drop-out, reset will occur in accordance with the reset curve as described before.
The current value is set in address 1207 51 PICKUP. The setting is mainly determined by the maximum an-
ticipated operating current. Pickup due to overload should never occur since in this mode the device operates
as fault protection with correspondingly short tripping times and not as overload protection.
The corresponding time multiplier for an IEC characteristic is set at address 1208 51 TIME DIAL and in
address 1209 51 TIME DIAL for an ANSI characteristic. It must be coordinated with the grading coordination
chart of the system.
The time multiplier can also be set to ∞. In this case, the element will not trip after pickup. However, pickup, will
be signaled. If the 51 element is not required at all, address 112 Charac. Phase sh
ould be set to Definite
Time during protective function configuration (see Section 2.1.1.2).
51N Element (ground) with IEC or ANSI Characteristics
Having set address 113 Charac. Ground = TOC IEC when configuring the protection functions (Section
2.1.1), the parameters for the inverse characteristics will also be available. Specify in address 1311 51N IEC
CURVE the desired IEC characteristic (Normal Inverse, Very Inverse, Extremely Inv. or Long
Inverse). If address 113 Charac. Ground was set to TOC ANSI, you can select the desired ANSI
characteristic (Very Inverse, Inverse, Short Inverse, Long Inverse, Moderately Inv.,
Extremely Inv. or Definite Inv.) at address 1312 51N ANSI CURVE.
If the inverse time trip characteristic is selected, it must be noted that a safety factor of about 1.1 has already
been included between the pickup value and the setting value. This means that a pickup will only occur if a
current of about 1.1 times the setting value is present. If Disk Emulation was selected at address 1310 51
Drop-out, reset will occur in accordance with the reset curve as described before.
The current value is set in address 1307 51N PICKUP. The setting is mainly determined by the minimum an-
ticipated ground fault current.
The corresponding time multiplier for an IEC characteristic is set at address 1308 51N TIME DIAL and in
address 1309 51N TIME DIAL for an ANSI characteristic. This has to be coordinated with the grading coor-
dination chart of the network. For ground currents with grounded network, you can often set up a separate
grading coordination chart with shorter delay times.
The time multiplier can also be set to ∞. In this case, the element will not trip after pickup. However, pickup, will
be signaled. If the 51N-TOC element is not required at all, address 113 Charac. Ground should be set to
Definite Time
during configuration of th
e protection functions (see Section 2.1.1).