Siemens Siprotec 7UM611 User Manual

2.7 Definite-Time Overcurrent Protection (I>>, ANSI 50, 51, 67) with Direction Detection
47
7UM61 Manual
C53000-G1176-C127-3
Figure 2-6 Cross-Polarized Voltages for Direction Determination
The phase carrying the highest voltage is selected for the direction decision. With
equal current levels, the phase with the smaller number is chosen (I
L1
before I
L2
before
I
L3
). The following table shows the allocation of measured values for various types of
short-circuit faults.
Table 2-2 Allocation of Measured Values for the Determination Direction
If the phase-to-phase voltage used for the direction decision is below the minimum
value of approx. 7 V, the voltage is taken from a voltage memory. This voltage also
allows unambiguous direction determination if the short-circuit voltage has collapsed
(short circuit close to generator terminals). After the expiration of the storage time
period (2 cycles), the detected direction is saved, as long as no sufficient measuring
voltage is available. If a short circuit already exists at generator startup (or for motors
or transformers on connection), so that no voltage is present in the memory and no
direction can be determined, a trip is issued.
The direction detection can be disabled via binary input.
Pickup Selected Current Associated Voltage
L1 I
A
U
L3
— U
L3
L2 I
L2
U
L2
— U
L3
L3 I
L3
U
L3
— U
L3
L1, L2 with I
L1
>I
L2
I
L1
U
L3
— U
L3
L1, L2 with I
L1
=I
L2
I
L1
U
L3
— U
L3
L1, L2 with I
L1
<I
L2
I
L2
U
L2
— U
L3
L2, L3 with I
L2
>I
L3
I
L2
U
L2
— U
L3
L2, L3 with I
L2
=I
L3
I
L2
U
L3
— U
L1
L2, L3 with I
L2
<I
L3
I
L3
U
L3
— U
L3
L3, L1 with I
L3
>I
L1
I
L3
U
L3
— U
L3
L3, L1 with I
L3
=I
L1
I
L1
U
L3
— U
L3
L3, L1 with I
L3
<I
L1
I
L1
U
L3
— U
L3
L1, L2, L3 with I
L1
>(I
L2
, I
L3
)I
L1
U
L3
— U
L3
L1, L2, L3 with I
L2
>(I
L1
, I
L3
)I
L2
U
L3
— U
L1
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Siemens Siprotec 7UM611 Specifications

General

Brand	Siemens
Model	Siprotec 7UM611
Category	Relays
Language	English