Schweitzer Engineering Laboratories SEL-387E - Over-;Undervoltage Element; Application Description; Operating Characteristic

Date Code 20080110 Protection Functions 3-55
SEL-387E Instruction Manual
Figure 3.32: I.E.C. Long-Time Inverse
Curve: C4
Figure 3.33: I.E.C. Short-Time Inverse
Curve: C5
O VER -/U NDERVOLTAGE E LEMENT
Application Description
The SEL-387E Relay offers the following overvoltage and undervoltage elements for protection,
indication, and control functions:
• Two levels of phase undervoltage
• Two levels of phase-to-phase undervoltage
• One level of positive-sequence undervoltage (V1)
• Two levels of phase overvoltage
• Two levels of residual overvoltage (3V0)
• One level of negative-sequence overvoltage (V2)
• One level of positive-sequence overvoltage
• Two levels of phase-to-phase overvoltage
Operating Characteristic
Phase overvoltage elements operate using the maximum of the measured phase voltage
magnitudes. Residual overvoltage elements operate using the sum of the three-phase voltage
(3V0) measurements. The positive- (V1) and negative-sequence (V2) overvoltage elements
operate when their respective measurements exceed their set thresholds. The phase-to-phase