2
-
4
MDP Digital Time Overcurrent Relay GE Power Management
2 OPERATING PRINCIPLES GEK-100682D
2
a) 51 INVERSE (5 A RATED RELAYS)
For 1.1 to 4 times the pickup TOC:
For 4 to 31 times the pickup TOC:
See Figure 2–4: INVERSE TIME CURVE on page 2–5.
b) BS142 INVERSE (1 A RATED RELAYS)
For 1 to 31 times the pickup TOC:
See Figure 2–8: BS142 INVERSE TIME CURVE (1 A MODELS ONLY) on page 2–9.
c) 53 VERY INVERSE
For 1.1 to 4 times the pickup TOC:
For 4 to 31 times the pickup TOC:
See Figure 2–6: VERY INVERSE TIME CURVE on page 2–7
d) 77 EXTREMELY INVERSE
For 1.1 to 20 times the pickup TOC:
See Figure 2–7: EXTREMELY INVERSE TIME CURVE on page 2–8.
e) 66 INVERSE LONG TIME
For 1.1 to 3 times the pickup TOC:
For 3 to 5 times the pickup TOC:
For 5 to 20 times the pickup TOC:
For 20 to 31 times the pickup TOC:
See Figure 2–5: LONG INVERSE TIME CURVE on page 2–6.
For all the above equations:
T
= time in seconds
P
= multiple of pickup TOC
Time Dial = for 5 A rated unit
= Time Dial Setting for 1 A rated unit
T
0.0059
P
0.001
1–
------------------------
0.419+
Time Dial
×
0.018+=
T
0.0069
P
0.001
1–
------------------------
0.252–
Time Dial
×
0.018+=
T
0.14
P
0.02
1–
----------------------
Time Dial
×
0.018+=
T
52.954
P
2.11
1–
----------------------
0.923+
Time Dial
×
0.018+=
T
28.447
P
1.702
1–
------------------------
1.007+
Time Dial
×
0.018+=
T
58.132
P
2.135
1–
------------------------
0.166+
Time Dial
×
0.020+=
T
0.0006
P
0.00001
1–
-----------------------------
5.644+
Time Dial
×
=
T
0.746
P
0.01
1–
----------------------
5.630–
Time Dial
×
=
T
0.00085
P
0.00001
1–
-----------------------------
12.530–
Time Dial
×
=
T
250 4.5
P
×
–
10
----------------------------------
Time Dial
×
=
Time Dial Setting
10
---------------------------------------------
Courtesy of NationalSwitchgear.com
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