Siemens 7SK80 Manual page 99

If the relay is used to protect transformers or motors with large inrush currents, the inrush restraint feature of
7SK80 may be used for the 67N-TOC PICKUP element (for more information see margin heading "Inrush Re-
straint").
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 setting value 67N-TOC PICKUP. 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 1610 67N-TOC DropOut, reset will occur in accordance with the reset curve as for the existing non-
directional time overcurrent protection described in Section 2.2.
The current value is set at address 1607 67N-TOC PICKUP. The most relevant for this setting is the minimum
appearing ground fault current.
The corresponding element time multiplication factor for an IEC Curve is set at address 1608 67N-TOC T-
DIAL and in address 1609 67N-TOC T-DIAL for an ANSI Curve. This has to be coordinated with the system
grading coordination chart for directional tripping. For ground currents with grounded network, you can mostly
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 67N-TOC Element is not required at all, address 116 67N/67N-TOC should be set to
Definite Time when configuring the protection functions (see Section 2.1.1).
Inrush restraint
When used at transformers where high inrush currents are expected, the 7SK80 can activate an inrush restraint
function for the directional overcurrent elements 67N-1 PICKUP, 67N-TOC PICKUP as well as for the non-
directional overcurrent elements. The inrush restraint option is enabled or disabled in 2201 INRUSH REST.
(in the settings option non-directional time overcurrent protection). The characteristic values of the inrush re-
straint are already listed in the section discussing the non-directional time overcurrent (Section 2.2.11).
Manual closing
When a circuit breaker is closed onto a faulted line, a high speed trip by the circuit breaker is often desired. For
overcurrent or high-set Element the delay may be bypassed via a Manual Close pulse, thus resulting in instan-
taneous tripping. This pulse is prolonged by at least 300 ms. To enable the device to react properly on occur-
rence of a fault in the phase elements after manual close, address 1613 MANUAL CLOSE has to be set accord-
ingly. This determines the delay after which the pickup value becomes effective when closing the circuit breaker
manually.
External control command
If the manual closing signal is not generated by the 7SK80, that is, it is sent neither via the built-in operator
interface nor via the serial port but directly from a control acknowledgment switch, this signal must be passed
to a 7SK80 binary input, and configured accordingly („>Manual Close") so that the Element selected for
MANUAL CLOSE will be effective. Inactive means that the Element operates as configured even with manual
close.
Internal control command
If the manual closing signal is generated by the device's integrated control function, the information items have
to be linked via CFC (interlocking task-level) using the CMD_Information function block.
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A5, Release date 11.2012
2.3 Directional Overcurrent Protection Ground 67, 67N
Functions
99