Schweitzer Engineering Laboratories SEL-700G Series, Инструкция по эксплуатации

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4.82
SEL-700G Relay Instruction Manual Date Code 20170814
Protection and Logic Functions
Group Settings (SET Command)
If the relay detects an out-of-step condition, it asserts the following Relay
Word bits:
➤
Relay Word bit SWING picks up when the positive-sequence
impedance stays between the outer and inner blinders for more
than 78D seconds (78R1 asserts, mho element 78Z1 may or may
not assert).
➤
Relay Word bit OOS picks up when the impedance trajectory
advances farther inside the inner blinder (78R1, 78R2, and mho
element 78Z1 assert).
➤
At the time the impedance trajectory exits the mho circle, the
rising-edge triggered timer with 78TD pickup delay and
78TDURD dropout delay starts timing. Relay Word bit OOST
remains picked up for 78TDURD seconds after pickup delay
time 78TD expires.
The double-blinder scheme distinguishes between short-circuit faults and out-
of-step conditions by monitoring the length of time that the impedance
trajectory stays between the two blinders. During short-circuit faults, the
impedance either moves inside the inner blinder or goes through the two
blinders almost instantaneously so that the 78D does not time out. Either case
prevents the out-of-step element from picking up. Figure 4.50 shows the logic
diagram for the double-blinder scheme.
The sum of the forward and reverse reaches (the diameter of the mho circle)
has to be 100 ohms or less for a 5 A relay and 500 ohms or less for a 1 A relay.
Set the inner blinder (78R2) so that its setting is greater than or equal to five
percent of either the forward or the reverse reach, whichever is greater.
The 78 element torque control SEL
OGIC
control equation OOSTC has a
default setting of one. If this value is left at one, the out-of-step element is not
controlled by any other conditions external to the element. However, users can
block operation of the 78 element for certain conditions, such as the presence
of excessive negative-sequence currents, by setting OOSTC to NOT 46Q1.
Refer to Logic Settings (SET L Command) for a detailed discussion of
SEL
OGIC
control equations.
The scheme includes positive-sequence current supervision setting 50ABC,
which has a setting range of 0.25–30.00 A for 5 A relays and 0.05–6.00 A for
1 A relays. Normally, a setting of 0.25 A for 5 A relays is adequate for most
applications. However, a higher setting can be applied based on minimum
expected swing currents. Note that the positive-sequence current levels below
the 50ABC setting block the out-of-step function.
The trip delay timer also has an adjustable dropout delay 78TDURD (Trip
Duration). The 78TDURD should be set appropriately if the Relay Word bit
OOST is configured to operate an output contact directly. The default setting
for the 78TDURD is zero because the Relay Word bit OOST is configured to
trip the generator breaker with default trip logic TRX (which includes an
identical timer TDURD). You must change the settings (trip logic and/or
78TDURD) if your application requires a different action.