Operation Principle - ABB RELION REX640 Technical Manual

1MRS759142 C
5.7.5
REX640
Technical Manual

Operation principle

The function can be enabled or disabled with the Operation setting. The
corresponding parameter values are "on" and "off".
The operation of SCEFRFLO can be described with a module diagram. All the
modules in the diagram are explained in the next sections.
I_A
I_B
I3P
I_C
U_A_AB
U_B_BC
U3P
U_C_CA
U
1
U
2
U
URES 0
TRIGG_REC
TRIGG_XC0F
TRIGG_T
BLOCK
GUID-D8247528-11EA-49DB-9D92-7F09C690FED5 V2 EN
Figure 595: Functional module diagram
The fault distance calculation is done in two steps. First, the fault type is determined
with the in-built Phase selection logic (PSL). Second, based on the selected
impedance measuring element (fault loop) the fault distance from the measuring point
to the fault location is calculated.
The phase current magnitude's minimum threshold value is 1% xIn.
Phase selection logic
Phase selection logic identifies the faulty phases based on a combined impedance and
current criterion. Phase selection logic is virtually setting-free and has only one
parameter, Z Max phase load, for discriminating a large symmetrical load from a
three-phase fault. The setting Z Max phase load can be calculated using the equation
Z Max phase load 0 8 .
= ⋅
GUID-0218DF43-DFE8-4F57-AD45-3E65C45AD27E V1 EN
U Nominal phase-to-phase voltage
xy
S Maximum three-phase load
max
For example, if U = 20 kV and S
xy
Protection related functions
Phase
selection
Fault
logic
impedance
and
distance
calculation
Trigger
detection
Alarm
indication
2
U
xy
S
max
= 1 MVA, then Z Max phase load = 320.0 Ω.
max
Section 5
ALARM
Recorded
data
(Equation 258)
1097