Siemens SENTRON - Default Chapter; Table of Contents

Selectivity for 3VA molded case circuit breakers
Configuration Manual, 08/2016, A5E03603181010-01
5
Table of contents
1 Introduction ................................................................................................................................................ 7
2
Selectivity - terms and definitions .............................................................................................................. 9
3
Methods of implementing selectivity using circuit breakers ...................................................................... 13
3.1
Starting point ........................................................................................................................... 15
3.2
Selectivity in the overload zone .............................................................................................. 15
3.2.1
Example .................................................................................................................................. 16
3.2.2
Circuit breaker parameters ..................................................................................................... 17
3.2.3
Tripping characteristics of circuit breakers ............................................................................. 18
3.3
Current selectivity ................................................................................................................... 19
3.3.1
Circuit breaker parameters ..................................................................................................... 20
3.3.2
Tripping characteristics of circuit breakers ............................................................................. 21
3.3.3
Different short-circuit currents at different fault locations ....................................................... 22
3.4
Time selectivity ....................................................................................................................... 23
3.4.1
Circuit breaker parameters ..................................................................................................... 26
3.4.2
Tripping characteristics of circuit breakers ............................................................................. 27
3.4.3
Implementation of total selectivity ........................................................................................... 28
3.5
Zone selective interlocking ..................................................................................................... 30
3.5.1
Zone selective interlocking and time selectivity ...................................................................... 33
3.5.2
Setting of circuit breakers ....................................................................................................... 36
3.6
Dynamic selectivity ................................................................................................................. 40
3.6.1
Implementation of dynamic selectivity .................................................................................... 41
3.6.2
Let-through energy diagram ................................................................................................... 43
3.6.3
Example .................................................................................................................................. 44
4
Selectivity implemented by combinations of protective devices ............................................................... 47
4.1
Molded case circuit breakers and downstream fuse .............................................................. 47
4.2
Fuse and downstream molded case circuit breaker ............................................................... 50
4.3
Fuse and downstream miniature circuit breaker ..................................................................... 53
4.4
Fuse and downstream fuse .................................................................................................... 53
5
Selectivity with parallel incoming feeders ................................................................................................. 57
5.1
Selectivity with two identical incoming feeders ....................................................................... 58
5.1.1
Symmetrical distribution (ideal scenario) ................................................................................ 59
5.1.2
Asymmetrical distribution ........................................................................................................ 59
5.2
Selectivity with three identical incoming feeders .................................................................... 60
5.2.1
Fault within the protection zone of the downstream protective device ................................... 60
5.2.2
Fault between transformer terminals and incoming feeder circuit breaker ............................. 61
5.3
Selectivity with bus-couplers ................................................................................................... 63
5.4
Sources of information and other documentation ................................................................... 68