ABB Relion 670 Series Technical Reference Manual page 234

Section 7
Voltage protection
228
The type C curve is described as:
×
k 480
=
t
æ - > ö
U U
ç × - ÷
32 0.5
è ø
>
U
IECEQUATION2288 V1 EN
The customer programmable curve can be created as:
×
k A
=
t
- >
æ ö
U U
× -
B C
ç ÷
>
è U ø
EQUATION1439 V1 EN
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< down
to U< · (1.0 – CrvSatn/100) the used voltage will be: U< · (1.0 – CrvSatn/100). If
the programmable curve is used this parameter must be calculated so that:
CrvSatn
× - >
B C 0
100
EQUATION1435 V1 EN
The highest phase (or phase-to-phase) voltage is always used for the inverse time
delay integration, see figure 112. The details of the different inverse time
characteristics are shown in section
+
0.035
3.0
+
D
p
"Inverse characteristics"
1MRK 505 208-UEN B
(Equation 53)
(Equation 54)
(Equation 55)
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