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The PSB operation is permitted when phase-overcurrent elements (OCCR) are operating.
The thresholds of OCCR elements are defined with VCT rated current multiplied by 0.08 (i.e.,
secondary rated 1A×0.08 or 5A×0.08).
a. PSBSIN and PSBSOUT in ZS
b. PSBGIN and PSBGOUT in ZG
Figure 2.10-25 Example of PSB element characteristic
The setting of PSBSIN adjusts automatically so that the PSBS operates properly in
accordance with the operation of ZS. The shaded area formed by the rectangle, which is
tangential with the elements (circles) in both directions of ZS, determines the size of PSBSIN.
For example, in Figure 2.10-25, Z2S is the most distant measuring element in the forward
direction; Z3S is the most distant measuring element in reverse direction; the top line of the
PSBSIN function is similar to the tangent of Z2S, the bottom line of the PSBSIN function is
similar to the tangent of Z3S. The outer element PSBSOUT encloses the inner element
PSBSIN with a width which can be set using the setting [PSBSZ].
Figure 2.10-25 illustrates the ZS elements are separately placed in the forward and
reverse directions. If all ZS elements are placed in one direction (in other words, elements are
not placed in the forward and the reverse), the inner and outer are constructed with the ZS
element and the other symmetrical element (see Figure 2.10-26). The symmetrical element is
as large as the largest ZS element; the symmetrical one will be placed by pivoting the largest
one around the origin.
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