Areva MiCOM P441, Техническое руководство

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Relay Description P44x/EN HW/E33
MiCOM P441/P442 & P444 Page 29/44
4.3.1 Convergence Analysis
This analysis is based on the measurements of distance and resistance of the fault. These
measurements are taken on each single-phase and two-phase loops. They determine the
convergence of these loops within a parallelogram-shaped, start-up characteristic.
D
R
P3037ENa
- R
R
lim
lim
- D
lim
D = X3
d
lim
= X4
For multi phase fault :
θ
= argument of Z
1
(positive sequenceimpedance)
For single phase fault :
θ
= argument of (2Z
1
+ Z
02
)/ 3
for zone 2, etc...
θ
= argument of (2Z
1
+ Z
01
)/ 3
for zone 1
L = line length in km or mile s
D3 = Z3/Zd x L = X3
D4 = Zd x L = X4
1
2
FIGURE 12 - START-UP CHARACTERISTIC
Let Rlim and Dlim be the limits of the starting characteristic.
The pair of solutions (Dfault (n-1), Rfault (n-1)) and (D fault (n), R fault (n)):
•
Rfault (n-1)< Rlim, and Rfault (n)< Rlim, and Rfault (n-1) - Rfault (n)< 10% x Rlim
•
Dfault (n-1)< Dlim and Dfault (n) < Dlim and Dfault (n-1) - Dfault (n) < 10% x Dlim
with Rlim being the resistance limit for the single and multi phase faults. This convergence is
dependent on the equations not being collinear thus allowing the terms in Dfault and Rfault
to be discriminated.
Theoretically, zone limits are Z3, Z4, +/- R3G-R4G or +/- R3Ph-R4Ph, if zones 3 and 4 are
enabled. The slope of the characteristic mimics the characteristic of the line.
To model the fault current:
•
Two-phase loops: the values (IA - IB), (IB - IC), or (IC - IA) are used.
•
Single-phase loops: (IA+ k0.3 x I0), (IB + k0.3 x I0), or (IC + k0.3 x I0) are used.
The results of these algorithms are mainly used as a backup; therefore, the circuit breaker
located at the other end is assumed to be open.
4.3.2 Start-Up
Start-up is initiated when at least one of the six measuring loops converges within the
characteristic (ZAN, ZBN, ZCN, ZAB, ZBC, ZCA).