Functions
2.32 Sensitive Earth Fault Protection B (ANSI 51GN)
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
232
Figure 2-101 Connection of the shaft current transformer (possible current flow in the event of a fault)
The shaft current transformer has to be purchased separately from a transformer manufacturer, or the existing
shaft current transformer can be used when replacing the protection. The diameter of the transformer depends
on the shaft diameter and can amount up to 2 m. The number of secondary winding turns vary slightly with the
diameter. These transformer are available with between 400 and 1000 turns. Transformers with less turns (e.g.
600 turns) should be used so as to provide a sufficiently high measurement current.
Shaft current transformers also have a test winding with usually 4 turns. It allows injecting a test current to check
the entire circuit. Figure 2-102 shows an example of the terminals S1-S2: measurement terminal (400 turns)
and A-B: test terminal (4 turns).
Figure 2-102 Terminals of the shaft current transformer
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