ABB RELION REX640 Technical Manual page 599

1MRS759142 F
where
[A],
Consider next the following example:
Example 1. Definite time operation of IFPTOC, when Operation principle = "EF
current based",
In the example, setting
DT stage Op time = 400 ms. Reduction factor =1.0. IFPTOC starts when estimated
fault current exceeds 4 A and operates after 400 ms, if start conditions are met. For
illustrating possible operating speed requirements of protection, limits of touch
voltage and earth potential rise durations defined in standard EN50522 scaled
into corresponding earth-fault current requirements using the maximum earthing
resistance R
are shown for reference.
REX640
Technical Manual
can be obtained. Sensitivity in terms of fault resistance depends also
on the network parameters (nominal voltage, damping and detuning) as
described by equation below:
U
is the nominal phase-to-earth voltage [V],
PE
I I
is the detuning [A],
v
Operating curve type = "Definite time" is illustrated in
EF current Str Val = 0.04*In (4 A with primary 100 A) and
(setting Maximum earthing Ris ) encountered in protected feeder
Emax
EF current Str Val in primary amperes.
is setting
F
Protection functions
(Equation 120)
I
is the total system damping
d
Figure 341
.
599