Basler Electric BE1-40Q - Manual (Page 39)

SECTION 5
• SETTING AND TESTING
SETTING
Setting the pickup value of BE1-40Q relays is facilitated by using the capability curves supplied by the
generator manufacturer as shown previously in the examples in Section 1. The figure for relay operating
characteristics is repeated here as Figure 5-1. Note that the line representing the relay characteristic is
positioned on the curve 8
° from horizontal and just above the point where the steady state stability limit
arc intersects the capability curve. (The 8
° slope applies to all BE1-40Q relays.)
Figure 5-1. Example of BE1-40Q Relay Operating Characteristics
The pickup setting is determined by the point where the BE1-40Q characteristic intersects the Q axis in
per unit (pu) quantities. Therefore, for the example shown in Figure 5-1, the pickup is
–0.4 pu. The actual
per unit pickup setting for your relay is determined by your specific application.
Per Unit Conversion Example
The per unit quantity is converted to a TAP switch setting by the procedure described in the following
example.
Given:
Rated power = 100 MVA
Rated voltage = 12.8 kV
CT ratio = 5000/5
PT ratio = 12800/120
Step 1. Determine the desired primary vars.
Three-phase primary vars = 0.4 x rated power
= 0.4 x 100 MVA
= 40 Mvar
Single-phase primary vars = 13.33 Mvar
Step 2. Determine the desired primary current.
Primary current = (single-phase primary var)
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9171500990 Rev N BE1-40Q Setting and Testing 5-1