Functions
2.32 Sensitive Earth Fault Protection B (ANSI 51GN)
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
233
Measurement Method
In order to preserve the flexibility of the application, there are different measurement methods available for pro-
cessing the sensitive earth current. The protection setting determines the measurement method to be used. In
algorithmic terms, this means that the FIR filter parameters have to be modified. In order to achieve high accu-
racy, a long filter window is used deliberately.
The following filter options are available:
Logic
Figure 2-103 shows the logic diagram. According to the selected measurement method, the measured value
is forwarded to the threshold decision logic. Depending on the application, it is possible to monitor a greater or
a smaller threshold. To prevent the pickup from „chattering“, a dropout time delay can be implemented. This
time is the holding time. A timer furthermore allows to delay the TRIP signal accordingly. Set to 0, the IEE-B<-
stage is disabled.
Figure 2-103 Logic diagram of the sensitive earth current protection IEE-B
Filtering Application
Fundamental component
(50 Hz or 60 Hz)
- Normal earth current protection applications
- Shaft current protection,
if fundamental component is predominant
3rd harmonic
(150 Hz or 180 Hz)
- Earth current monitoring in the generator starpoint to detect faults
in the vicinity of the starpoint (supplementary logic via CFC if necessary).
- Shaft current protection,
if 3rd harmonic is predominant
Fumdamental component
and 3rd harmonic
- Shaft current protection if both the fundamental component and the
3rd harmonic are predominant
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