ABB REG670 - Page 489

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 (Equation 107)
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 (Equation 108)
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 (Equation 109)
The lowest voltage is always used for the inverse time delay integration. The details
of the different inverse time characteristics are shown in section 25.3 "Inverse
characteristics".
1MRK502052-UEN B Section 9
Voltage protection
483
Technical manual