Inverse-Time Overcurrent Protection 51(N) - Siemens SIPROTEC 7SK80 Manual

Motor protection

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Table of Contents

Inverse-Time Overcurrent Protection 51(N)

Operating Modes

Measuring Technique

All elements

Setting Ranges / Increments

Pickup currents 51 (phases)

Pickup currents 51N

Time multiplier T for 51, 51N

for IEC characteristics

Time multiplier T for 51, 51N

for ANSI characteristics

Trip Time Curves acc. to IEC

Acc. to IEC 60255-3 or BS 142, Section 3.5.2 (see also Figures 4-1 and 4-2)

The tripping times for I/I

For zero sequence current, read 3I0p instead of I

for ground fault, read I

Pickup threshold

SIPROTEC, 7SK80, Manual

E50417-G1140-C344-A4, Release date 08.2010

Phases A and C

First harmonic, rms value (true rms)

= 1 A 0.10 A to 4.00 A

= 5 A 0.50 A to 20.00 A

= 1 A 0.05 A to 4.00 A

= 5 A 0.25 A to 20.00 A

≥ 20 are identical with those for I/I

instead of I

instead of T

4.3 Inverse-Time Overcurrent Protection 51(N)

0.05 s to 3.20 s or ∞

0.50 s to 15.00 s or ∞

instead of T

approx. 1.10 · I

Technical Data

Increments 0.01 A

Increments 0.01 s