Siemens SIPROTEC 4 7SJ61 Manual page 62

Functions
2.2 Overcurrent Protection 50, 51, 50N, 51N
pickup, will be signaled. If the 50N-2 element or 50N-3 element is not required at all, the pickup threshold
50N-2 or 50N-3 should be set to ∞. This setting prevents tripping and the generation of a pickup message.
50-1 Element (phases)
For setting the 50-1 element, it is the maximum anticipated load current that must be considered above all.
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. For this reason, a setting equal to 20% of
the expected peak load is recommended for line protection, and a setting equal to 40% is recommended for
transformers and motors.
The settable time delay (address 1205 50-1 DELAY) results from the grading coordination chart defined for
the system.
The selected time is an additional delay time and does not include the operating time (measuring time,
dropout time). The delay can also be set to ∞. In this case, the element will not trip after pickup. However,
pickup, will be signaled. If the 50-1 element is not required at all, then the pickup threshold 50-1 should be set
to ∞. This setting prevents tripping and the generation of a pickup message.
50N-1 Element (ground)
The 50N-1 element is normally set based on minimum ground fault current.
If the relay is used to protect transformers or motors with large inrush currents, the inrush restraint feature of
7SJ61 may be used for the 50N–1 relay element. It can be enabled or disabled for both the phase current and
the ground current in address 2201 INRUSH REST.. The characteristic values of the inrush restraint are listed
in Subsection "Inrush Restraint".
The settable delay time (address 1305 50N-1 DELAY) results from the time coordination chart defined for the
system. For ground currents in a grounded system a separate coordination timer with short time delays can be
applied.
The selected time is an additional delay time and does not include the operating time (measuring time,
dropout time). The delay can also be set to ∞. In this case, the element will not trip after pickup. However,
pickup, will be signaled. If the 50N-1 element is not required at all, the pickup threshold 50N-1 PICKUP should
be set to ∞. This setting prevents tripping and the generation of a pickup message.
Pickup Stabilization (Definite Time)
The configurable dropout times 1215 50 T DROP-OUT or 1315 50N T DROP-OUT can be set to implement a
uniform dropout behavior when using electromechanical relays. This is necessary for a time grading. The
dropout time of the electromechanical relay must be known to this end. Subtract the dropout time of the
device (see Technical Data) from this value and enter the result in the parameters.
51 Element (phases) with IEC or ANSI characteristics
Having set address 112 Charac. Phase = TOC IEC or TOC ANSI when configuring the protection func-
tions (Section 2.1.1.2 Setting
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 Defi-
nite 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
anticipated operating current. Pickup due to overload should never occur since in this mode, the device oper-
ates 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 time coordination
chart of the system.
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Notes), the parameters for the inverse time characteristics will also be available.
SIPROTEC 4, 7SJ61, Manual
C53000-G1140-C210-6, Edition 05.2016