ABB RELION REX640 Technical Manual page 563

1MRS759142 F
residual current estimate regardless of the fault type. This estimate is the result
of the fundamental frequency admittance calculation using the CPS technique.
The stabilized current value is obtained (after conversion) from the corresponding
admittance value by multiplying it by the system nominal phase-to-earth voltage
value. The equations for calculating the stabilized values of the fundamental
frequency admittance and the corresponding current are given below.
1
Y
o stab
1
Y
o stab
1
I
0
CPS
1
U
0
1
G
o stab
1
B
o stab
1
I
o stab
1
I
o stab
1
I
o Cosstab
1
I
o Sinstab
U
baseres
The main advantage of the filtering method is that due to the admittance
calculation, the resulting current value does not depend on the fault resistance
value, that is, the estimated current magnitude equals the value that is measured
during a solid earth fault (Rf = 0 Ω). Another advantage of the method is that it can
estimate correct current magnitude also during intermittent or restriking faults.
The setting
be exceeded for the function to start or operate.
Setting
based on the "Adaptive", "Amplitude" or "Resistive" methods.
REX640
Technical Manual
⋅
1
3 I

= =
1
0 CPS
Y
Re

o stab
−
1
U
0
CPS
Stabilized fundamental frequency admittance estimate, which is result from
fundamental frequency admittance calculation utilizing the Cumulative Phasor
Summing (CPS) technique.
Fundamental frequency zero-sequence current phasor calculated utilizing the
Cumulative Phasor Summing (CPS) technique.
Fundamental frequency zero-sequence voltage phasor calculated utilizing the
Cumulative Phasor Summing (CPS) technique.
CPS
Real-part of stabilized fundamental frequency conductance estimate.
Imaginary part of stabilized fundamental frequency susceptance estimate.
1 1
( G j B )
= + ⋅ ⋅
ostab ostab
Stabilized fundamental frequency residual current estimate, which is obtained
(after conversion) from the corresponding admittance value by multiplying it
with the system nominal phase-to-earth voltage value.
Real-part of stabilized fundamental frequency residual current estimate.
Imaginary part of stabilized fundamental frequency residual current estimate.
System nominal phase-to-earth voltage value.
Min operate current defines the minimum operate current which must
Operating quantity defines whether the current magnitude supervision is
  
+ ⋅ =
1
j Y
Im
  
o stab
1
U I j I
= + ⋅
baseres oCosstab
Protection functions
+ ⋅
1 1
G j B
ost a a b ostab
1
oSinsta b b
(Equation 97)
(Equation 98)
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