Basler Electric BE1-11m - Manual (Page 227)

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On occasion, however, protection engineers will encounter situations where CT polarity is reversed for a
specific application. That is, non-polarity of the CT secondary will be in phase with the primary current
flow (Figure 180). For example, a transformer differential CT from a breaker with a different polarity
convention such as low voltage switchgear, or a bus differential CT taken from the low side of a
transformer.
Orientation of CT polarity relative to primary current flow establishes the secondary CT terminal that
should be connected to polarity of the BE1-11m.
Figure 178. Standard CT Polarity
Figure 179. Current Transformer Action
BE1-11m Terminals and Connectors