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2.10.1.2 Setting Notes
General
It is a prerequisite for the operation of the weak infeed function that it was enabled
during the configuration of the device at address 125 Weak Infeed = Enabled.
With the parameter FCT Weak Infeed (address 2501) it is determined whether the
device shall trip during a weak infeed condition or not. With the setting ECHO and
TRIP both the echo function and the weak infeed tripping function are activated. With
the setting ECHO only the echo function for provision of the release signal at the in-
feeding line end is activated. There is, however, no tripping at the line end with missing
or weak infeed condition. As the weak-infeed measures are dependent on the signal
reception from the opposite line end, they only make sense if the protection is coordi-
nated with teleprotection (refer to Section 2.7 and/or 2.9).
The receive signal is a functional component of the trip condition. Accordingly, the
weak infeed tripping function must not be used with the blocking schemes. It is only
permissible with the permissive schemes and the comparison schemes with release
signals! In all other cases it should be switched OFF at address 2501. In such cases
it is better to disable this function from the onset by setting address 125 to Disabled
during the device configuration. The associated parameters are then not accessible.
The undervoltage setting value UNDERVOLTAGE (address 2505) must in any event be
set below the minimum expected operational phase-earth voltage. The lower limit for
this setting is given by the maximum expected voltage drop at the relay location on the
weak-infeed side during a short-circuit on the protected feeder for which the distance
protection may no longer pick up.
Echo Enable
In applications with a transmission channel used by both the distance and the earth
fault protection spurious trippings may occur, if distance protection and earth fault pro-
tection create an echo independently from each other. In this case parameter
Echo:1channel (address 2509) has to be set to YES. The default setting is NO.
The remaining settings apply to the echo function and are described in the corre-
sponding sections (2.7 and 2.9 respectively).
A summary of the settings and the information table can be found right after the setting
notes for the French specification.
2.10.2 Tripping According to Specification RTE
2.10.2.1 Functional Description
An alternative for detecting weak infeed is only available in the models 7SD5***-**D**.
In addition to the classical function of weak infeed, the so called Logic no. 2 (ad-
Pickup with Rela-
dress 125) presents an alternative to the method used so far.
tive Voltage Jump
This function operates independently of the teleprotection scheme by using its own
receive signal and it is able to trip with delay and without delay.
7SD5 Manual
C53000-G1176-C169-1
2.10 Weak-infeed Tripping (optional)
253
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