Functions
2.20 Out-of-Step Protection (ANSI 78)
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
169
Figure 2-70 Logic Diagram of the Out-of-Step Protection
2.20.3 Setting Notes
General
Out-of-step protection is only effective and available if this function was set during protective function configu-
ration (Section 2.4, address 135, OUT-OF-STEP is set to Enabled. If the function is not required Disabled
is set. Address 3501 OUT-OF-STEP serves to switch the function ON or OFF or to block only the trip command
(Block relay).
Pickup
Measurement is enabled only if the positive sequence component of the currents has exceeded a minimum
threshold 3502 I1> RELEASE (overcurrent pickup). Also because of the symmetry condition, a maximum
value of negative sequence current 3503 I2< RELEASE must not be exceeded.
Generally the setting value I1> RELEASE should be set over rated current i.e. about 120 % I
N
to avoid pickup
on overload. Depending on network conditions, smaller pickup values are admissible so that the measurement
(see logic diagram ) may be released all the time. As out-of-step conditions are symmetrical occurrences, the
pickup threshold of the negative sequence component of the current I2< RELEASE should be set to approx.
20 % I
N
.
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