ERL 8700/BUS, Руководство пользователя, Страница: 58 / 166

4 Protection Functions
4-14 B-PRO User Manual 8700 D01908R02.12
50/51/67 Phase Overcurrent
Phase overcurrent provides backup protection to the differential protection.
This function operates on fundamental quantities of the highest phase current
of the 3 phases. Two sets of phase time overcurrent protection functions on
each CT input provide directional or non-directional current detection. There
is a definite time overcurrent element (50) and an inverse time overcurrent el-
ement (51). You can configure both 50 and 51 to be non-directional, forward
direction, or reverse direction sensitive. You can also configure both 50 and 51
outputs to initiate the 50BF protection element. Device 51 provides three pre-
defined IEEE, three IEC inverse time curves, and one user-defined curve. The
equation and the parameters of device 51 are listed below. You can select the
user-defined curve type and the parameters in the equation are settable other-
wise they are fixed and determined by the curve type.
Figure 4.17: 50/51/67 Phase Overcurrent
When the threshold for pickup of the relay is exceeded, the function 51 alarm
will pickup indicating the relay has commenced timing.
Table 4.1: IEC and IEEE Curves
#
Characteristic A B p tr
1
IEC Standard Inverse 0.14 0 0.02 13.5
2
IEC Very Inverse 13.5 0 1.0 47.3
3
IEC Extremely Inverse 80.0 0 2.0 80.0
4
IEEE Moderately Inverse 0.0103 0.0228 0.02 0.97
5
IEEE Very Inverse 3.922 0.0982 2.0 4.32
6
IEEE Extremely Inverse 5.64 0.0243 2.0 5.82
7 User-defined
0.0010 to
1000.0 0.0000 to
10.000 0.01 to
10.0 0.10 to
100.00
Timer is active only
if it's directional.
Directional element
Directional element
50/51 Over Current for Input 1
0
T
0
10ms
T = 10 ms or setting whichever
is greater if it's directional.
Max
1A
1B
1C
50
51 Pickup
Alarm
51
www
. ElectricalPartManuals
. com