Phase Differential Protection: Self-Balancing And Split-Phase Configurations (50/51); Self-Balancing - Basler BE1-11g Instruction Manual

9424200994 Rev U 131
Phase Differential Protection: Self-
Balancing and Split-Phase
Configurations (50/51)
The BE1-11g can be configured for the protection of generator stator applications involving the use of
self-balancing current transformers for detecting phase faults or for differently connected current
transformers of split-phase generator windings to detect turn-to-turn faults. Typical configurations of these
protection schemes use a 50 or 51 element, or a combination of both, for each phase or winding. The
BE1-11g has six Instantaneous Overcurrent (50) elements and seven Inverse Overcurrent (51) elements,
which can be individually configured to the relative phase or winding to which the protection is to be
applied.
For these applications, the 50 and/or 51 elements will be set to individual phases by selecting IA, IB, or IC
as the mode of protection for each element relative to each winding or phase to be protected. To set the
50 and/or 51 elements for three-phase operation, the "three-phase" mode should be selected. Further
guidance on setting the 50 and 51 elements in BESTCOMSPlus for IA, IB, or IC can be found in the
chapters titled Instantaneous Overcurrent (50) Protection and Inverse Overcurrent (51) Protection.

Self-Balancing

In a split-phase configuration, each phase of generator windings is split into parallel sets of windings. This
design characteristic is used to detect turn-to-turn shorts. When a turn-to-turn short occurs, current
circulates in the generator winding because of the voltage imbalance that occurs as a result of the
shorted turn. This fault can be detected by several different CT configurations. Regardless of the chosen
CT configuration, an Inverse Time Overcurrent (51) element combined with an Instantaneous Overcurrent
(50) element for each set of windings provides adequate protection for turn-to-turn shorts. The CT
configuration and wiring to the BE1-11g is shown in Figure 80.
Figure 80. Split-Phase Connections
BE1-11g

Phase Differential Protection: Self-Balancing and Split-Phase Configurations (50/51)