Functions
2.4 Backup Overcurrent
SIPROTEC, 7SD80, Manual
E50417-G1140-C474-A1, Release date 09.2011
90
Inrush Blocking
You can specify for each element of the overcurrent protection whether the element will be blocked when inrush
is detected. The setting applies collectively to the corresponding phase and ground element.
50-1, 3I0> address 2625
50-2, 3I0>> address 2615
50N, 3I0p address 2637
50-3, 3I0>>> address 2653
Pickup Values
The elements can be combined. The pickup values are determined by the type of protected object.
The pickup values are set specifically for each element:
50-B2 PICKUP, 67-B2 PICKUP address 2623
50N-B2 PICKUP, 67N-B2 PICKUP address 2626
50-B1 PICKUP, 67-B1 PICKUP address 2613
50N-B1 PICKUP, 67N-B1 PICKUP address 2616
51-B PICKUP, 67-TOC PICKUP address 2633
51N-B PICKUP, 67N-TOC PICKUP address 2638
The setting of the current pickup value is basically determined by the maximum operational current. Pickup due
to overload must be excluded as the device operates as short-circuit protection in this mode with correspond-
ingly short command times and not as overload protection. A pickup value setting of about 10% is recommend-
ed for line protection, and a setting of about 20% of the expected peak load is recommended for transformers
and motors.
The ground current elements detect the smallest anticipated ground fault current.
For very long lines with small source impedance or on applications with large reactances (e.g. transformers,
series reactors), the 50-2 elements can also be used for current grading. In this case, they must be set such
that they do not pickup reliably on a short circuit at the line end.
For the inverse time elements a safety margin between pickup value and setting value has already been im-
plemented. Pick up only occurs at a current which is approximately 10% above the set value. Please bear this
in mind when specifying the setting values of the inverse time elements.
If an element is not required, set the pickup value to ∞.
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