ABB RELION 650 Series Applications Manual page 103

1MRK 505 363-UEN A
IdMin =
EQUATION14000040 V1 EN-US
In order to allow the differential protection to be backup protection for internal faults and
faults on the LV side of the transformer, we activate the function
and calculate suitable setting for the parameter
threshold
the transformer on HV side. The setting will be:
ImaxAddDelay
EQUATION14000041 V1 EN-US
Table 12:
Station
Type of fault
Object
Settings
Characteristic
High set stage
It is then important to achieve a proper back-up protection. The Short circuit protection on the
outgoing bays and on the transformer LV side are set according to a prepared selectivity
chart. An example is prepared and shown in Figure
protection on the LV side is 14 MVA and Normal Inverse with k=0.12 to give back-up to
outgoing bays relays which are extremely inverse, selective to remote fuses.
IEC14000047 V1 EN-US
Figure 50: Selectivity chart
Application manual
If
× 138 =
1 2 . 11 5 .
I
Base
Imax AddDelay will be time delayed. We choose the value 2 times the rated current of
S
n
= × 2
3 × U × I
n Base
Backup protection example data
Tap transformer 10 MVA
Three phase fault
1 = 10 kV Line A
2 MVA
IEC Extr.inverse, k=0.5,
A=80, p=2
14 MVA
Imax AddDelay . Differential currents below the
= 2 0 .
2 = T1 10 kV 50/51
14 MVA
IEC Norm.inverse k=0.12,
A=0.14, p=0.02
- - - -
50 where the setting of the short circuit
Differential protection
(Equation 29)
AddDelay by setting it to On
(Equation 30)
3 = 130 kV 87L
(ImaxAddDelay)
20 MVA
IEC Norm.inverse k=0.18,
A=0.14, p=0.02
- - - -
IEC14000047 -1-en.ai
Section 6
97