Schweitzer Engineering Laboratories SEL-587Z - Equation 3.20

3.18
SEL-587Z Instruction Manual Date Code 20020903
Relay Elements
Overcurrent Protection
I.E.C. Class B Curve (Very Inverse): C2
Operating Time
Equation 3.20
Reset Time
Equation 3.21
I.E.C. Class C Curve (Extremely Inverse): C3
Operating Time
Equation 3.22
Reset Time
Equation 3.23
I.E.C. Long-Time Inverse Curve: C4
Operate Time
Equation 3.24
Reset Time
Equation 3.25
I.E.C. Short-Time Inverse Curve: C5
Operate Time
Equation 3.26
Reset Time
Equation 3.27
tp TD
13.5
M1–
--------------
• =
tr TD
47.3
1M
2
–
----------------
• =
tp TD
80.0
M
2
1–
----------------
• =
tr TD
80.0
1M
2
–
----------------
• =
tp TD
120.0
M1–
--------------
• =
tr TD
120.0
1M–
--------------
• =
tp TD
0.05
M
0.04
1–
-----------------------
• =
tp TD
4.85
1M
2
–
----------------
• =