Functions
2.15 Sensitive Earth Flt.(comp/ isol. starp.)
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
298
Figure 2-151 Faulted line location in meshed networks using directional indications
2.15.2 Setting Notes
General
This section applies only to relay models with earth fault detection module and only when these are used in
networks with isolated or compensated starpoint. In other cases, this section can be skipped.
Earth fault detection is only possible if the function Sens. Earth Flt (address 130) was set to Enabled
during configuration. If the device is equipped with earth fault detection but is to operate in an earthed network,
address 130 Sens. Earth Flt must
be set to Disabled!
The earth fault detection can be switched ON: with Trip, OFF or set to Alarm Only at address 3001 Sens.
Earth Flt. In the latter case (default setting) the device announces detected earth faults, identifies the faulty
phase and the earth fault direction according to the other settings.
If the earth fault detection is switched ON: with Trip it also issues a trip command. In this case no earth
fault protocol is generated, but a trip log that registers all information about the earth fault and the earth fault
tripping. The tripping can be delayed via address 3007 T 3U0>.
Voltage Stages
The displacement voltage is the pickup threshold of the earth fault detection and is set in address 3002 3U0>.
If the displacement voltage U
en
of the voltage transformer set is directly connected to the fourth voltage mea-
suring input U
4
of the device and if this was predefined during the configuration, the device will use this voltage,
multiplied by the factor Uph / Udelta (address 211). For the usual transformation of the voltage transformer
with e–n–winding
the factor is set to 1.73 (√3
) (see also Subsection 2.1.2.1, margin heading „Voltage Transformer Connection“).
In case of a complete displacement of a healthy voltage triangle the displacement voltage has a value that is
√3
times the phase-to-phase voltage.
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