Areva MiCOM P441, Техническое руководство

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P44x/EN AP/E33 Application Notes
Page 36/220 MiCOM P441/P442 & P444
2.8.4 Zone 1 Extension Scheme
Auto-reclosure is widely used on radial overhead line circuits to re-establish supply following
a transient fault. A Zone 1 extension scheme may therefore be applied to a radial overhead
feeder to provide high speed protection for transient faults along the whole of the protected
line. Figure 11 shows the alternative reach selections for zone 1: Z1 or the extended reach
Z1X.
P3052ENa
ZL
Z1A
A B
Z1B
Z1 Extension (A)
Z1 Extension (B)
FIGURE 11 - ZONE 1 EXTENSION SCHEME DEFINIED AS DESCRIBED ABOVE:
Z1 < Z1X < Z2 or Z1 < Z2 < Z1X
(with
Z1 < ZL < Z1X)
In this scheme, zone 1X is enabled and set to overreach the protected line. A fault on the
line, including one in the end 20% not covered by zone 1, will now result in instantaneous
tripping followed by autoreclosure. Zone 1X has resistive reaches and residual
compensation similar to zone 1. The autorecloser in the relay is used to inhibit tripping from
zone 1X such that upon reclosure the relay will operate with Basic scheme logic only, to co-
ordinate with downstream protection for permanent faults. Thus, transient faults on the line
will be cleared instantaneously, which will reduce the probability of a transient fault becoming
permanent. The scheme can, however, operate for some faults on an adjacent line,
although this will be followed by autoreclosure with correct protection discrimination.
Increased circuit breaker operations would occur, together with transient loss of supply to a
substation.
The time delays associated with extended zone Z1X are shown in Table 2 below:
Scenario Z1X Time Delay
First fault trip = tZ1
Fault trip for persistent fault on autoreclose = tZ2
TABLE 2 - TRIP TIME DELAYS ASSOCIATED WITH ZONE 1X
The Zone 1 Extension scheme is selected by setting the Z1X Enable bit in the Zone Status
function links to 1.
FIGURE 12 – SETTINGS IN MiCOM S1 (GROUP1\DISTANCE SCHEME\ZONE STATUS)