ABB ret650, Applications Manual

Page: 118 / 392

For the customer tailor-made inverse time delay characteristics (type 17), all three
types of reset time characteristics are available: instantaneous (1), IEC (2 = set
constant time reset) and ANSI (3 = current dependent reset time). If the current-
dependent type is used, settings
pr , tr and cr must be given.
tResetx : Constant reset time delay in seconds for step x.
tPCrvx , tACrvx , tBCrvx , tCCrvx : These parameters are used by the customer to
create the inverse time characteristic curve. See equation 20 for the time
characteristic equation. For more information, refer to Technical manual .
[ ]
>
p
A
t s B IxMult
i
C
in
= + ×
-
æ ö
ç ÷
ç ÷
ç ÷
æ ö
ç ÷ ç ÷
è ø è ø
EQUATION1261 V2 EN-US
(Equation 20)
tPRCrvx , tTRCrvx , tCRCrvx : These parameters are used by the customer to create
the inverse reset time characteristic curve. For more information, refer to Technical
manual .
HarmRestrainx : Enables the block of step x from the harmonic restrain function
(2nd harmonic). This function should be used when there is a risk of an unwanted
trip caused by power transformer inrush currents. It can be set to
Off / On .
7.2.3.2 Setting example
GUID-20729467-24AB-42F0-9FD1-D2959028732E v1
Directional phase overcurrent protection, four steps can be used in different ways,
depending on the application where the protection is used. A general description is
given below.
The operating current setting of the inverse time protection, or the lowest current
step of the definite time protection, must be defined so that the highest possible
load current does not cause protection operation. The protection reset current must
also be considered so that a short peak of overcurrent does not cause the operation
of a protection even when the overcurrent has ceased. This phenomenon is
described in Figure
45 .
Section 7
1MRK 504 169-UEN A
Current protection
112 Transformer protection RET650 2.2 IEC
Application manual