Basler BE1-CDS240, Instruction Manual

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27R threshold setting, the overcurrent element will be blocked. When set for this mode of operation, the
51P pickup setting is typically set near or below load current levels.
When set for Restraint mode of operation, the pickup of the phase overcurrent element is adjusted based
upon the magnitude of the measured voltage. Figure 4-26 shows how the overcurrent pickup threshold
setting is adjusted in response to the measured voltage level. Equation 4-1 determines the pickup level
for the 51P elements when the measured voltage is between 25% and 100% of the 27R threshold setting.
Below 25%, the pickup level stays at 25%. Above 100%, the pickup level stays at 100%. For example, if
the 27R threshold is set for 120V and the measured voltage on the appropriate phase is 100V (83% of
the 27R threshold setting), the overcurrent pickup level for that phase will be reduced to 83% of its
setting. When set for this mode of operation, the 51P pickup setting is typically set above worst case, load
current levels.
Figure 4-26. 51P Pickup Level Compensation
The 51/27R function can be set to monitor either Vpp or Vpn depending upon the VTP connection
settings. See Section 3,
Input and Output Functions, Power System Inputs , for more detail on how to set
the VTP Connections. Table 4-14 shows which voltage measurements are used by each phase
overcurrent element for each possible VTP connection and 51/27 voltage monitoring mode setting.
Table 4-14. VTP Connection Cross Reference
VTP Connection 51/27 Mode 51A 51B 51C
4W Vpp Vab Vbc Vca
4W Vpn Van Vbn Vcn
3W Vpp Vab Vbc Vca
AN Vpn Van N/A N/A
BN Vpn N/A Vbn N/A
CN Vpn N/A N/A Vcn
AB Vpp Vab N/A N/A
BC Vpp N/A Vbc N/A
CA Vpp N/A N/A Vca
When single-phase voltage sensing is used, only the overcurrent element on the phase with voltage
magnitude information is affected by the 51/27R feature. Thus, in voltage control mode, the 51 elements
on the two unmonitored phases will always be disabled. In voltage restraint mode, the 51 elements on the
two unmonitored phases will not have their overcurrent pickup settings adjusted from 100%.
NOTE
For single-phase sensing, the unmonitored phase is not restrained or controlled.
These phases are marked in the table by N/A (not applicable).
9365200990 Rev F BE1-CDS240 Protection and Control 4-31