Schweitzer Engineering Laboratories SEL-321 - Time-Overcurrent Curve Equations; Figure 2.49: Ground and Phase Distance Speed Curves

2-80 Specifications Date Code 20011026
SEL-321/321-1 Instruction Manual
Figure 2.49: Ground and Phase Distance Speed Curves
TIME-OVERCURRENT CURVE EQUATIONS
Both US and IEC time-overcurrent curves are provided in the SEL-321 Relay. Use the SET
command to select the curve characteristics you desire. Refer to Section 3: Communications
for a complete description of the use of the SET command and selection of time-overcurrent
characteristics.
These time curve equations are valid for all time-overcurrent elements. Plots showing operating
time versus multiples of pickup current are shown on the following pages. The equations and
curves apply while the product of the multiples of pickup and pickup setting is less than 32⋅I
nominal
amps, secondary.