1. Co-ordination of LV Protection Devices
DBTP107PRE-En-07/00

2. Contents Operator needs Availability of electrical energy 3
Co-ordination of LV protection devices 8
Co-ordination techniques 12 o The IEC standard 12 o Discrimination techniques 16 o Limitation 21 o Cascading 23
Schneider solutions 24 o Masterpact and the incoming end of the installation 25 o Compact NS and power distribution 30 o Multi 9 circuit-breaker and final distribution 33 o Discrimination rules for 1 to 6300 A 34
Conclusion 35

3. From one application to another operator needs are the same
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…The availability of electrical energy...

4. The availability of electrical energy
Savings for the operator through: o the continuity of electrical supply o the optimised cost of his installation
…A source of profit for the operator...
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5. Availability of electrical energy and the LV protection plan
Structure of LV Distribution
Level 1 General LV = incomer Switchboard
Level 2 = MSB feeders
Distribution Level 3 Switchboard = power or distribution motor control
Level 4 Final = final distribution switchboards distribution
Loads
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6. Availability of electrical energy and the LV protection plan
Structure of LV Distribution
Installation design o priority / non priority feeders
Protection of LV distribution o level 1 and 2: using Air Circuit-Breaker (ACB) or Moulded Case Circuit-Breaker (MCCB) with high rating to 6300 A o level 3: using LV industrial Fuse or Moulded Case Circuit-Breaker (MCCB) 63 to 1250 A o level 4: using Miniature Circuit-Breaker (MCB) 1 to 100 A
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7. Availability of electrical energy and the LV protection plan
Continuity of
electrical
energy supply
Cost of the electrical installation
Customer needs
Co-ordination of
protection devices:
discrimination, cascading
& constraint limitation
Protection Plan

8. LV co-ordination techniques
Optimising LV electrical distribution through 3 actions at the Protection Plan Level
1) discrimination to guarantee continuity of supply
2) limitation to reduce constraints
3) cascading to optimise performances
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9. Co-ordination of protection devices 1) discrimination
Whatever the fault: o overload o short-circuit o insulation fault only the circuit-breaker located just upstream from the fault trips
4 types of discrimination o current o time o energy o logic
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10. Co-ordination of protection devices 2) limitation
Technique that allow for the harmful effects of short-circuit currents to be diminished
Limitation reduces effects of the following type: o electromagnetic: reduction in EMC disturbances o mechanical: reduction of deformation and/or breaks o thermal: rise in the life span of trunkings
Isc presumed
transient peak
steady peak
Isc limited peak
Isc
10 % Â
tsc t
100 % t A2
I2sc
Presumed energy 100 %
Limited energy < 1 %
1 %
100 %
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11. Co-ordination of protection devices 3) cascading
The limiting upstream circuit-breaker helps the downstream circuit-breakers to open
Technique that allows for the cost of LV electrical distribution to be optimised
Non priority
feeder
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12. The IEC 60947-2 standard and co-ordination of protection devices
Recognises the 2 co-ordination elements (appendix A) o discrimination o cascading
Defines testing to guarantee this co-ordination
Characterises the circuit-breakers capable of time discrimination o utilisation category B
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13. The IEC 60947-2 standard appendix A discrimination
Definition of the discrimination limit Is
Tests to be conducted
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14. The IEC 60947-2 standard appendix A cascading
Definition of the current IB and of the reinforced breaking capacity IcuD2+D1
Tests to be conducted
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15. The IEC 60947-2 standard category B circuit-breakers
They ensure time discrimination that is characterised by Icw during Dt o Icw must be at least equal to 12 In or 5 kA for In £ 2500 A 30 kA for In > 2500 A o Dt - standardised delay - of: or 1 s
They are subjected to additional testing
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16. LV discrimination techniques
Quality of discrimination Comparison of the discrimination limit Is to the presumed short-circuit current Isc determines the quality of discrimination
o total discrimination: Is > Isc o partial discrimination: Is < Isc
o if the discrimination limit is equal to the Icu of the upstream circuit-breaker discrimination is total
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only D2 trips
D1 and D2 trip

17. Current discrimination
Linked to the natural staging of Long Delay curves of the association o discrimination limit Is = Isd1
discrimination technique generally used in Final Distribution
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18. Time discrimination
Time delay Dt of the upstream circuit-breaker’s Short Delay CR tripping o extension of current safety o discrimination limit Is = Ii1 (= Icw1)
o discrimination technique generally used on the incoming end of the installation the upstream circuit-breaker is from category B with a high EDW (Icw1 = Icu1)
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19. Energy discrimination
Comparison of energy curves (tripping D downstream/non tripping ND upstream) allows for the discrimination limit Is to be determined
Only the manufacturer can guarantee the quality of discrimination of the energy type D
Tripping ND
Non
tripping
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20. Logic discrimination (ZSI)
Circuit-breakers fitted out with electronic trip units o a pilot wire between upstream / downstream circuit-breakers o no threshold rules
This technique o is easily implemented o reduces to a minimum constraints from delayed tripping of time discrimination
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21. Limitation
Technique consists in using the arc voltage to limit short-circuit currents
3 criteria to be considered
o early o fast o high
Technique that has multiple advantages o limitation of constraints on the installation o better discrimination o circuit-breaker cascading
I asymetric peak
Isc IL
early
fast
high
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22. Improving discrimination through limitation
The use of a limiting downstream circuit-breaker extends current and/or time discrimination with the upstream circuit-breaker
The downstream circuit-breaker by limiting the fault current Id increases the discrimination limit Is
Isc
in D2 D2
non limiting
D2 limiting Is
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D2 non limiting Is Is
D2 limiting
Isc (D2)
presumed

23. Cascading
The use of a limiting upstream circuit-breaker “increases” the breaking capacity of the downstream circuit-breaker
Technique that allows for the installation of a limiting circuit-breaker downstream from circuit-breakers with optimised Breaking Capacities
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24. Totally co-ordonated Schneider protection devices
Schneider solutions
Continuity of electrical
energy supply
Cost of the electrical installation
Customer needs
Totally co-ordonated Schneider protection devices
Constraint
Limitation
Discrimination as a standard in the
circuit-breaker ranges
Economical association of circuit-breakers through Cascading

25. Masterpact power circuit-breakers
Discrimination upstream: setting the long delay (LR) slope (IDMTL) allows for better discrimination
Discrimination downstream: o better time discrimination thanks to higher Icw o on very high Isc (up to 150 kA), maintains a high level of discrimination
Limitation of very high constraints
Masterpact offers unequalled performances as a standard for all applications
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26. Improving MV/LV discrimination thanks to IDMTL curves
5 suggested slopes: o DT: definite time o SIT: inverse standard time o VIT: very inverse time o EIT: extremely inverse time o HVF: HV compatible fuse
HVF curve tr = 2 s
MV Fuse 80 A brought to LV
I2t curve tr = 12 s
Short delay threshold = 4 Ir
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27. Ensuring total time discrimination as a standard
Time discrimination with very high Icw (up to 85 kA 1s) thanks to: o a globally reinforced mechanism, enclosure, copper parts o the use of air CTs for measurement
Accuracy zone of the
instantaneous
tripping threshold (± 10 %)
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Maximum time discrimination
NW H2
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Icw = thermal withstand = self-protection DIN threshold

28. Increasing the breaking capacity without sacrificing discrimination
Conciliate high breaking capacity (150 kA) and high Icw (65 kA -1s)
Disengagement
Half moon actvating
the pole shaft
Effort sensor
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Kinematic chain
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29. Limiting as much as possible the constraints on the incoming end of the installation
Limitation o using disengagement for very fast breaking o modification of the fixed pole to increase the repulsion force
Time discrimination up to 37 kA
Unequalled performances for a limiting circuit-breaker
Breaking chamber
Presumed
short-circuit current
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Magnetic U
Limited
current
Total breaking time
U-shaped
current loop
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Intervention time
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30. Compact NS power distribution
Arc
New breaking technology o roto-active breaking o pressure (“reflex” tripping) n o
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Fixed contact
Breaking enclosure
Breaking chamber
Mobile contact
Piston
Short-circuit
current
Breaking chamber
Short-circuit
current
Provides an exceptional limiting capacity n
Fixed contact
Breaking enclosure
Mobile contact
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Piston
New breaking technology o roto-active breaking
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Fixed contact
Breaking enclosure
Breaking chamber
Mobile contact
Piston
Short-circuit
current
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31. Natural discrimination
Compact NS circuit-breakers have natural discrimination performances o current and/or time tripping curves o natural discrimination energy curves
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32. Simultaneous discrimination and cascading
Compact NS circuit-breakers have natural Cascading performances
reflex tripping (piston)
Reinforced Breaking Capacity without loss of Discrimination D1
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33. Final distribution Multi 9 circuit-breakers
Technology with magnetic actuator
Guaranteed performances o ultra rapid breaking o exceptional limitation o total discrimination with circuit-breakers located upstream
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34. Schneider discrimination rules
Masterpact
total discrimination with Compact NS (<630 A) circuit-breakers located downstream
Compact NS
total discrimination as soon as the ratio between ratings is greater than 2.5
Note: it is necessary to conserve current and time threshold staging The Schneider solution ensures total natural discrimination from 1 to 6300 A
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35. The Schneider solution: mastering the technique
Continuity of supply thanks to total discrimination CA
Recording
box
production
Compact NS
1 to 160 A
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Factory assembly line
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36. The Schneider solution: mastering the financial aspect
Upon installation
During operation
Thanks to the quality of limitation of these circuit-breaker ranges
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37. The Schneider solution: mastering services
Simple and high-performance tools o software: Ecodial 3 o catalogue: Exhaustive choice table
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LV Catalogue
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38. “No one in the world does more with electricity”
Schneider offers circuit-breaker ranges from 1 to 6300 A with unequalled performances
Standards are respected
Performance of co-ordinations: o discrimination as a standard o highly economical cascading
Simple and high-performance catalogues and software
Schneider guarantees a safe and high- performance electrical installation for mastering the LV protection plan
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