ABB RED650 - Page 239

where:
Un< Set value for step 1 and step 2
U Measured voltage
The type B curve is described as:
n
n
k
t
U U
U
2.0
480
0.055
32 0.5
×
= +
æ ö
< -
× -
ç ÷
<
è ø
EQUATION1432 V2 EN-US (Equation 38)
The customer programmable curve can be created as:
p
n
n
k A
t D
U U
B C
U
é ù
ê ú
ê ú
×
= +
ê ú
æ ö
ê ú
< -
× -
ç ÷
ê ú
<
è ø
ë û
EQUATION1433 V2 EN-US (Equation 39)
When the denominator in the expression is equal to zero the time delay will be
infinity. There will be an undesired discontinuity. Therefore a tuning parameter
CrvSatn is set to compensate for this phenomenon. In the voltage interval U
n
<
down to U
n
< · (1.0 – CrvSatn/100) the used voltage will be: U
n
< · (1.0 – CrvSatn/
100). If the programmable curve is used this parameter must be calculated so that:
0
100
CrvSatn
B C× - >
EQUATION1435 V1 EN-US (Equation 40)
The lowest voltage is always used for the inverse time delay integration. The
details of the different inverse time characteristics are shown in section "Inverse
characteristics".
1MRK 505 394-UEN A Section 9
Voltage protection
Line differential protection RED650 2.2 IEC 233
Technical manual