Cascading & Discrimination

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1 Cascading & Discrimination

2 Typical LV System Level 1 ACBs A General LV Switchboard Level 2 ACB A MCCB 3200A Level 3 MCCB 1250A Fuses 630A Switchboard, Panelboard or MCC Level 4 MCBs - 100A Final Distribution Boards E62649

3 How do you determine the Fault level?

4 Terminology BSEN Overload >105% nominal current in an electrically sound circuit over a given period of time. ( Long Time Protection ) Short Circuit Electrical fault between Phases or to Earth usually >10x nominal current ( Instantaneous Protection ) Nominal Current = rating of the breaker

5 Terminology BSEN Icu Ultimate breaking capacity tested by O- CO O = opening or breaking operation C = closing or making operation. test for di-electric 2x rated voltage, but not less that 1000v, example: Icu = 70KA Ics Service Rating, tested by O-CO-CO test for di-electric 2 x rated voltage. temperature rise test at nominal operating current sometimes expressed as a % of Icu example Icu/Ics = 50% standard ratios 100%,75%,50% & 25%

Terminology BSEN 60947-2 Utilisation category Cat A a circuit breaker not

selectivity under short circuit conditions (eg.

delay in respect of providing selectivity under short circuit conditions, such

6 Terminology BSEN Utilisation category Cat A a circuit breaker not specifically designed with an intentional time delay in respect of providing selectivity under short circuit conditions (eg. Lower rating MCCBs Compact NSX) Cat B a circuit breaker with an intentional time delay in respect of providing selectivity under short circuit conditions, such circuit breakers have a short time withstand current rating ( Icw ) (eg. Large MCCBs & ACBs Compact NS, Masterpact NT & NW)

7 Arc chute Magnet Double rotating contact Filter

8 Fundamental Features

9 Customer Benefits

Fundamental Features Improved double roto-active contact New contact material, new arc chamber Breaking units rationalized Reflex tripping For energy discrimination

10 Fundamental Features Improved double roto-active contact New contact material, new arc chamber Breaking units rationalized Reflex tripping For energy discrimination reflex tripping unit new raw material Polar breaking units to confine gas New filters for ratings above 400A, more exchange area Isolation function Positive break indication

Completely safe controls and settings "Mitop"

required after fitting Settings shown in Amps

remote control The Micrologic 5/6 keyboard can be

11 Completely safe controls and settings "Mitop" integrated in the tripping device No electrical test required after fitting Settings shown in Amps Transparent sealed cover on the tripping device on the remote control The Micrologic 5/6 keyboard can be locked The settings and control can be locked in communication mode video_007

12 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 stresses 3) cascading to optimise performances

The IEC 60947-2 standard and co-ordination of protection devices Recognises the 2 co-ordination elements (appendix A) discrimination cascading

13 The IEC standard and co-ordination of protection devices Recognises the 2 co-ordination elements (appendix A) discrimination cascading Defines testing to guarantee this co-ordination Characterises the circuit-breakers capable of time discrimination utilisation category B E55229

14 What is discrimination? Total discrimination No discrimination CB1 CB1 CB1 and CB2 trip CB2 Only CB2 trips CB2 The power supply to the other feeders is still ensured The power supply to the other feeders is no longer ensured

15 Discrimination on different levels CB1 CB 2 CB3 CB 4 CB 5 CB 6 CB 7 Only CB7 trips

16 Co-ordination of protection devices 1) discrimination B A C Whatever the fault: overload short-circuit Ideally only the circuit-breaker located just upstream from the fault trips E types of discrimination current time energy logic

Discrimination in overload - rules Distribution Motor (circuit) Thermalmagnetic circuit breaker Electronic protection circuit breaker Electronic protection circuit breaker Thermal-magnetic or

17 Discrimination in overload - rules Distribution Motor (circuit) Thermalmagnetic circuit breaker Electronic protection circuit breaker Electronic protection circuit breaker Thermal-magnetic or electronic protection circuit breaker Thermalmagnetic circuit breaker Electronic protection circuit breaker Thermalmagnetic circuit breaker Thermalmagnetic or electronic protection circuit breaker Ratio : Upstream setting Downstream setting

6 Upstream Ir = 250A, Downstream = 160A Upstream/downstream ratio <1.

18 Discrimination in overload - rules NSX250N TMD NSX160N TMD NSX250N TMD NSX160N TMD NSX250N + TM250D NSX160N + TM160D 250/160 = 1.56 ratio Ratio should be > 1.6 Upstream Ir = 250A, Downstream = 160A Upstream/downstream ratio <1.6 therefore partial discrimination only Upstream Ir = 250A, Downstream = 144A ( 0.9xIn ) Therefore Upstream/downstream ratio >1.6 TM160D 160A/40 o C x160a x160a 250/144 = 1.73 ratio

19 Discrimination in short circuit - rules Distribution Motor (circuit) Thermalmagnetic circuit breaker Electronic protection circuit breaker Electronic protection circuit breaker Thermal-magnetic or electronic protection circuit breaker Thermalmagnetic circuit breaker Electronic protection circuit breaker Thermalmagnetic circuit breaker Thermalmagnetic or electronic protection circuit breaker Ratio : Upstream setting Downstream setting [TM upstream] 1.5 [Micrologic upstream]

Discrimination in short circuit - rules NSX250N + TM250D NSX250N TMD NSX160N TMD Upstream Im = 2500A (10xIn), Downstream = 1250A (fixed) Therefore Upstream/downstream ratio = 2 NSX160N + TM160D Steps

20 Discrimination in short circuit - rules NSX250N + TM250D NSX250N TMD NSX160N TMD Upstream Im = 2500A (10xIn), Downstream = 1250A (fixed) Therefore Upstream/downstream ratio = 2 NSX160N + TM160D Steps to be taken: Provisionally select devices Consult catalogue for discrimination info. on particular combination of devices. Set devices to ensure ratios between upstream/downstream settings are adequate.

21 Energy based Discrimination according to IEC Energy let through curve of the downstream device Non-tripping energy curve of the upstream device. EN defines the method for calculating discrimination by comparing the operational curves based on the energy provided: i2 dt i2 dt downstream device I upstream device I

22 Discrimination with Compact NSX NSX160F/N/H/L TM125D Non-tripping curve NSX160 (TM125D) ic60 ic60 (63A) ic60 (10A) Total discrimination

23 Discrimination table ic60n B,C,D curves ic60n C curve All figures in ka

24 Logic Discrimination Principle: E41329 Breaker 2 detects the fault and sends a signal to Breaker 1 250mS Delay CB1 Twisted pair cable Breaker 1 receives 2 s signal & remains closed 2 eliminates the fault CB2 1 remains closed

25 Co-ordination of protection devices 2) limitation Technique that allows for the harmful effects of short-circuit currents to be reduced Limitation reduces following effects: electromagnetic: reduction in EMC disturbances mechanical: reduction of deformities and breaks thermal: increase the life span of busbars and cables Isc Â 100 % Isc presumed transient peak Isc presumed steady peak I 2 sc A % Presumed energy 100 % Isc limited peak E % tsc t 1 % Limited energy < 1 % t E62651

26 Co-ordination of protection devices 3) cascading The limiting upstream circuit-breaker helps the downstream circuit-breakers to open This technique allows the cost of LV electrical distribution to be optimised E62667

Cascading tested combination example Re-inforced breaking capacity of downstream device NSX250L 220A E41149 + Allows the

27 Cascading tested combination example Re-inforced breaking capacity of downstream device NSX250L 220A E Allows the installation of lower fault rating breakers downstream ( cost saving) NSX100F 63A - Discrimination study still needs to be carried out ic60h 25A

28 Cascading and enhanced discrimination Gives all the benefits of cascading without loss of discrimination Achievable with: Compact NSX - ic60h Compact NSX - Compact NSX Cascading and enhanced discrimination

29 Acti9 E41343 ic60n ic60h 30/30 = 30kA Discrimination level, 30kA back-up protection

30 Schneider solutions Customer needs Continuity of electrical energy supply Cost of the electrical installation Totally co-ordonated Schneider protection devices Discrimination as a standard in the circuit-breaker ranges Stress Limitation Economical association of circuit-breakers through Cascading

31 Design Aids - Curve Direct V3.4

32 On-Line Electrical Calculation Tools

33 Complementary Technical Information

Cascading. Complementary technical information

Cascading. Complementary technical information Cascading What is cascading? Cascading is the use of the current limiting capacity of circuit breakers at a given point to permit installation of lower-rated and therefore lower-cost circuit breakers downstream.