Siemens 7SC80 Manual page 89

Due to the following definition
[hochstrom-260602-kn, 1, en_US]
the following setting applies to the protection device: The 50-2 high-set current element must be set higher
than the maximum fault current which is detected during a low side fault on the high side. To reduce fault
probability as much as possible even when fault power varies, the following setting is selected in primary
values: 50-2 /Ι
Nom
50-3.
Increased inrush currents, if their fundamental component exceeds the setting value, are rendered harmless
by delay times (address 1203 50-2 DELAY or 1218 50-3 DELAY).
The principle of the "reverse interlocking" utilizes the multi-element function of the time overcurrent protec-
tion: Element 50-2 PICKUP is applied as a fast busbar protection with a shorter safety delay time 50-2
DELAY (e.g. 100 ms). For faults at the outgoing feeders, element 50-2 is blocked. The elements 50-1 or 51
serve as backup protection. The pickup values of both elements (50-1 PICKUP or 51 PICKUP and 50-2 PICKUP)
are set equal. The delay time 50-1 DELAY or 51 TIME DIAL is set in such manner that it overgrades the
delay for the outgoing feeders.
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 50-2 element or the 50-3 element is not required at all, the pickup threshold
50-2 or 50-3 is set to ∞. This setting prevents tripping and the generation of a pickup message.
High-Set Current Elements 50N-2, 50N-3 (ground)
The pickup current of the high-set current element 50N-2 PICKUP or 50N-3 PICKUP can be set at address
1302 or 1317. The corresponding delay time 50N-2 DELAY or 50N-3 DELAY can be configured under
address 1303 or 1318. The same considerations apply to these settings as they did for phase currents
discussed earlier.
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-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, the maximum anticipated load current must be considered. Pickup due to over-
load must 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, lines are set to approx. 20 % above the
maximum expected (over)load and transformers to approx. 40 %.
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.
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.
SIPROTEC Compact, 7SC80, Manual
E50417-G1140-C486-A8, Edition 07.2017
= 10, i.e. 50-2 = 1000 A. The same applies analogously when using the high-set element
2.2 Overcurrent Protection 50, 51, 50N, 51N
Functions
89