Current Transformer and Current Input
26 RTHC-SVD01B-EN
5. Phase Unbalance. Using the current inputs, UCP2 provides
Phase Unbalance Protection based on average three phase cur-
rent. The ultimate phase unbalance trip point shall be 30% for 90
seconds (not including individual phase sensing error) based on
the following calculation:
where:
and: I0x = the phase with the largest difference from Iave.
Individual phase sensing error: 3% maximum (or 6% phase-to-
phase max)
91 25 230
92 25 230
93 26 229
94 27 228
95 28 227
96 28 227
97 29 226
98 30 225
99 30 225
100 31 224
% unbalance =
(I0x - Iave) x 100
Iave
Iave =
I01 + I02 + I03
3
Table 4-2: Current Overload Settings #1 and #2 as a Function
of CT Factor
CT Factor Setting #1 Setting #2
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