ABB RELION Series, Technical Manual

Page: 387 / 804

1.2 · Reset delay time (minimum of 600 ms). If the fault direction based on the cyclic
phasor accumulation is opposite to the function direction output for Reset delay time
or 500 ms (minimum of 500 ms), the function is reset and fault direction calculation
of MFADPSDE is restarted.
In case the earth-fault protection is alarming, the MFADPSDE includes also a
RESET
input, which can be utilized to externally re-trigger the fault direction determination,
if re-evaluation of fault direction during a persistent earth fault is required. It is also
recommended to connect the start signal of non-directional earth-fault protection
(EFxPTOC), set to operate in case of a cross-country fault, to
RESET
input of
MFADPSDE to reset phasor accumulation during a cross-country fault. MFADPSDE
is then able to adapt to possible fault direction change more rapidly, if single phase
earth fault still persists in the system after the other faulty feeder has been tripped
(cross-country fault has been transformed back to a single phase earth fault).
The direction of the MFADPSDE function is supervised by a settable current
magnitude threshold. The operate current used in the magnitude supervision is
measured with a special filtering method, which provides very stable residual current
estimate regardless of the fault type. This stabilized current estimate is the result from
fundamental frequency admittance calculation utilizing the CPS technique. The
stabilized current value is obtained (after conversion) from the corresponding
admittance value by multiplying it with the system nominal phase-to-earth voltage
value, which is entered as a base value for the residual voltage (U
baseres
). The
equations for calculating the stabilized values of the fundamental frequency
admittance and the corresponding current are given below.
Y
I
U
Y j Y G
o stab
CPS
CPS
o stab o stab ost
1
0
1
0
1
1 1
3
=
⋅
−
=

 

+ ⋅

 

=
Re Im
a ab ostab
j B
1 1
+ ⋅
GUID-8236D202-E4DB-4185-898D-0FAE1A15431C V1 EN
(Equation 40)
Y
o stab
1
The stabilized fundamental frequency admittance estimate, which is result from fundamental
frequency admittance calculation utilizing the Cumulative Phasor Summing (CPS) technique.
I
CPS
0
1
The fundamental frequency zero-sequence current phasor calculated utilizing the Cumulative
Phasor Summing (CPS) technique.
U
CPS
0
1
The fundamental frequency zero-sequence voltage phasor calculated utilizing the Cumulative
Phasor Summing (CPS) technique.
G
o stab
1
The real-part of stabilized fundamental frequency conductance estimate.
B
o stab
1
The imaginary part of stabilized fundamental frequency susceptance estimate.
1MRS758755 A
Section 4
Protection functions
REC615 and RER615 381
Technical Manual