Chapter 7 - 7SR45 Applications Guide
©2018 Siemens Protection Devices Limited
Chapter 7 Page 2 of 10
Contents
Section 1: Current Transformer Requirements .................................................................................................... 3
1.1
Time Delayed Overcurrent (51/51G/51N) ............................................................................................ 7
1.2
Selection of Overcurrent Characteristics ............................................................................................. 8
1.2.1
Reset Delay ......................................................................................................................... 9
1.3
Instantaneous Overcurrent (50/50G/50N) ......................................................................................... 10
List of Figures
Figure 1-1
Burden of the Relay for Different Currents ..................................................................................... 5
Figure 1-2
IEC NI Curve with Time Multiplier and Follower DTL Applied.......................................................... 7
Figure 1-3
IEC NI Curve with Minimum Operate Time Setting Applied ............................................................ 8
Figure 1-4
Reset Delay ................................................................................................................................. 9
Figure 1-5
General Form of DTL Operate Characteristic ............................................................................... 10