Areva MiCOM P441, Техническое руководство

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P44x/EN HW/E33 Relay Description
Page 26/44 MiCOM P441/P442 & P444
4.2.3 Confirmation
In order to eliminate the transitions generated by possible operations or by high frequencies,
the transition detected over a succession of three sampled values is confirmed by checking
for at least one loop for which the two following conditions are met:
• ∆
V > threshold V, where threshold V = 0.1 Un /
√
3 = 0.1 Vn
and
• ∆
I > threshold l, where threshold I= 0.2 In.
The start-up of the high-speed algorithms will be confirmed if
∆
U AND
∆
I are detected on
three consecutive samples.
4.2.4 Directional Decision
The "Delta" detection of the fault direction is determined from the sign of the energy per
Phase for the transition values characterising the fault.
Relay
Z
L
Z
S
Z
L
Z
R
Reverse Fault
P3035ENa
-V
F
R
F
Voltage at Relay Location
Current at Relay Location
=
=
V
R
R
I
V
R
R
I
R
Relay
Z
L
Z
S
Z
L
Z
R
Forward Fault
-V
F
R
F
Voltage at Relay Location
Current at Relay Location
=
=
V
R
R
I
V
R
F
I
R
FIGURE 10 - DIRECTIONAL DETERMINATION USING SUPERIMPOSED VALUES
To do this, the following sum per phase is calculated:
)
0
0
i
A
5
i
AN A
I . ( S
∆ ∆ =
∑
+ ≥
n ni
n
V )
0
0
i
B
5
i
BN B
I . ( S
∆ ∆ =
∑
+ ≥
n ni
n
V )
0
0
i
C
5
i
CN C
I . ( S
∆ ∆ =
∑
+ ≥
n ni
n
V
Where no is the instant at which the fault is detected, ni is the instant of the calculation and S
is the calculated transition energy.
If the fault is in the forward direction, then S i <0 (i = A, B or C phase).
If the fault is in the reverse direction, then S i >0.
The directional criterion is valid if
S >5 x (10% x Vn x 20% x In x cos (85° )
This sum is calculated on five successive samples.
RCA angle of the delta algorithms is equal to 60° (-30°) if the protected line is not serie
compensated (else RCA is equal to 0°).