9-4 Setting the SEL-351P Recloser Control Date Code 990430
SEL-351P Manual Técnico
T
IME
-O
VERCURRENT
C
URVES
The following information describes the curve timing for the curve and time dial settings made
for the time-overcurrent elements (see Figure 3.14 through Figure 3.20). The time-overcurrent
relay curves in
Figure SECTION 9: .1 through Figure SECTION 9: .10 conform to IEEE
C37.112-1996 IEEE Standard Inverse-Time Characteristic Equations for Overcurrent Relays.
tp = operating time in seconds
tr = electromechanical induction-disk emulation reset time in seconds (if electromechanical
reset setting is made)
TD = time dial setting
M = applied multiples of pickup current [for operating time (tp), M>1; for reset time (tr), M≤1].
U.S. Moderately Inverse Curve: U1 U.S. Inverse Curve: U2
tp = TD*(0.0226 + 0.0104/(M
0.02
- 1)) tp = TD*(0.180 + 5.95/(M
2
- 1))
tr = TD*(1.08/(1 - M
2
)) tr = TD*(5.95/(1 - M
2
))
U.S. Very Inverse Curve: U3 U.S. Extremely Inverse Curve: U4
tp = TD*(0.0963 + 3.88/(M
2
- 1)) tp = TD*(0.0352 + 5.67/(M
2
- 1))
tr = TD*(3.88/(1 - M
2
)) tr = TD*(5.67/(1 - M
2
))
U.S. Short-Time Inverse Curve: U5
tp = TD*(0.00262 + 0.00342/(M
0.02
- 1))
tr = TD*(0.323/(1 - M
2
))
I.E.C. Class A Curve (Standard Inverse): C1 I.E.C. Class B Curve (Very Inverse): C2)
tp = TD*(0.14/(M
0.02
- 1)) tp = TD*(13.5/(M - 1))
tr = TD*(13.5/(1 - M
2
)) tr = TD*(47.3/(1 - M
2
))
I.E.C. Class C Curve (Extremely Inverse): C3 I.E.C. Long-Time Inverse Curve: C4
tp = TD*(80.0/(M
2
- 1)) tp = TD*(120.0/(M - 1))
tr = TD*(80.0/(1 - M
2
)) tr = TD*(120.0/(1 - M))
I.E.C. Short-Time Inverse Curve: C5
tp = TD*(0.05/(M
0.04
- 1))
tr = TD*(4.85/(1 - M
2
))
All 38 traditional recloser control response curves are available and shown in Figure 9.11
through Figure 9.20. Each curve has two designations. For example, the bottom curve in
Figure 9.11 has the following two designations:
Older electronic control designation: A
Newer microprocessor-based control designation 101
Use either designation in making curve settings in the SEL-351P.
See Table 8 and Table 9 and following text in the Settings section of the SEL-351P Quick-Start
Installation and User’s Guide for more information on available time-overcurrent curves,
including user-programmable curves.
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