Siemens SIPROTEC 7UM62 User Manual

Functions
2.9 Definite-Time Overcurrent Protection (I>>, ANSI 50, 51, 67) with Direction Detection
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
70
Figure 2-14 Cross-Polarized Voltages for Direction Determination
The phase carrying the highest current 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 2-3 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
L1
U
L2
- U
L3
L2 I
L2
U
L3
- U
L1
L3 I
L3
U
L1
- U
L2
L1, L2 with I
L1
>I
L2
I
L1
U
L2
- U
L3
L1, L2 with I
L1
=I
L2
I
L1
U
L2
- U
L3
L1, L2 with I
L1
<I
L2
I
L2
U
L3
- U
L1
L2, L3 with I
L2
>I
L3
I
L2
U
L3
- U
L1
L2, L3 with I
L2
=I
L3
I
L2
U
L3
- U
L1
L2, L3 with I
L2
<I
L3
I
L3
U
L1
- U
L2
L3, L1 with I
L3
>I
L1
I
L3
U
L1
- U
L2
L3, L1 with I
L3
=I
L1
I
L1
U
L2
- U
L3
L3, L1 with I
L3
<I
L1
I
L1
U
L2
- U
L3
L1, L2, L3 with I
L1
>(I
L2
, I
L3
) I
L1
U
L2
- U
L3
L1, L2, L3 with I
L2
>(I
L1
, I
L3
) I
L2
U
L3
- U
L1

Siemens SIPROTEC 7UM62 Specifications

General

Brand	Siemens
Model	SIPROTEC 7UM62
Category	Protection Device
Language	English