ACB,MCCB
Merlin Gerin Circuit breaker application guide MM M M M M M M M M M M M M E R L IN G E R IN multi 9 C6 0N C 63 4 0 0 V a 6 0 0 0 2 4 2 3 4 2 4 10 kA IE C 9 47 .2 O - OFF O - OFF O - OFF O - OFF 6 8 1 3 5 7 M E R L I N G E R I N m ulti 9 C60N C 25 2 3 0 V a 6 0 0 0 2 4 1 7 8 O - OFF 10 kA IEC 947. 2 M E R L IN G E R IN multi 9 C 60N C 63 4 0 0 V a 6 0 0 0 2 4 2 3 4 2 4 10 kA IE C 9 47 .2 O - OFF O - OFF O - OFF O - OFF 6 8 1 3 5 7 1 .5 2 3 4 5 6 8 10 xI r I m .6 3 .7 .8 . 85 . 9 .9 5 . 9 8 1 xI n I r S T R 2 2 S E 9 0 1 0 5 % I r a l a r m Im Ir I n = 2 5 0 A 250N P 9 3 0 8 3 OFF M E R L I N G E R I N c o m p a c t N S 2 5 0 N U i 7 5 0 V . U i m p 8 k V . 2 2 0 / 2 4 0 3 8 0 / 4 1 5 4 4 0 5 0 0 6 6 0 / 6 9 0 2 5 0 8 5 3 6 3 5 3 0 8 5 0 c a t A I E C 9 4 7 - 2 U T E V D E B S C E I U N E N E M A U e ( V ) I c u (k A ) I c s = 1 0 0 % I c u 1 6 0 / 2 5 0 A p u s h t o t r i p p u s h t o t r i p 250N P 9 3 0 8 3 1.5 2 3 4 5 6 8 1 0 x Ir I m .6 3 .7 .8 . 8 5 .9 .9 5 .9 8 1 xI n I r S T R 2 2 S E 9 0 1 0 5 % I r a l a r m I m Ir I n = 2 5 0 A OFF M E R L IN G E R I N c o m p a c t N S 2 5 0 N U i 7 5 0 V . U i m p 8 k V . 2 2 0 / 2 4 0 3 8 0 / 4 1 5 4 4 0 5 0 0 6 6 0 / 6 9 0 2 5 0 8 5 3 6 3 5 3 0 8 5 0 c a t A I E C 9 4 7 - 2 U T E V D E B S C E I U N E N E M A U e ( V ) Ic u ( k A ) I c s = 1 0 0 % I c u 1 6 0 / 2 5 0 A p u s h t o t r i p p u s h t o t r i p M E R L IN G E R IN m u l t i 9 ID 'clic C 3 2 40 m A ∆ n 0 , 0 3 0 A 2 3 0 V a 2 0 5 6 4 2 0 5 6 4 I D ' c l i c b i 4 0 A B S E N 6 1 0 0 9 a 3 0 0 0 3 N 1 L 1 3 L 2 I . O N M E R L I N G E R I N m u l t i 9 N G 1 2 5 L I n = 1 2 5 A 2 2 0 / 2 4 0 V 3 8 0 / 4 1 5 V 4 4 0 V 5 0 0 V U e(V ) 5 0 2 5 1 5 6 I E C 9 4 7 . 2 1 8 8 0 6 Ic u(kA ) 1. 5 2 3 4 5 6 8 1 0 x Ir I m .6 3 . 7 . 8 .8 5 .9 .95 .9 8 1 x In I r S T R 2 2 S E 9 0 1 0 5 % I r a l a r m I m I r I n = 2 5 0 A 250N P 9 3 0 8 3 OFF M E R L I N G E R I N c o m p a c t N S 2 5 0 N U i 7 5 0 V . U i m p 8 k V . 2 2 0 / 2 4 0 3 8 0 / 4 1 5 4 4 0 5 0 0 6 6 0 /6 9 0 2 5 0 8 5 3 6 3 5 3 0 8 5 0 c a t A I E C 9 4 7 - 2 U T E V D E B S C E I U N E N E M A U e ( V ) I c u ( k A ) Ic s = 1 0 0 % Ic u 1 6 0 / 2 5 0 A p u s h t o t r i p p u s h t o t r i p Ic µP >I r >I m t e s t fa u l t S T R 5 3 U E 6 0 7 5 9 0 1 0 5 % I r I Im Ir Io tr tm ( s ) x I n x Ir x Io x In o n I 2 t o f f ( s ) a t 1 .5 Ir te s t R t r t m I m I r I M E R L I N G E R I N c o m p a c t NS400 H U i 7 5 0 V . U i m p 8 k V . U e ( V ) 2 2 0 / 2 4 0 3 8 0 / 4 1 5 4 4 0 5 0 0 / 5 2 5 6 6 0 / 6 9 0 1 0 0 7 0 6 5 4 0 3 5 I E C 9 4 7 - 2 U T E V D E B S C E I U N E N E M A I c u ( k A ) c a t B I c s = 1 0 0 % Ic u Ic w 6 k A / 0 , 2 5 s I n = 4 0 0 A . 8 1 . 6 3 . 5 . 9 . 9 3 . 9 5 . 9 8 . 8 8 . 8 5 . 8 1 4 5 6 8 3 2 1 . 5 1 0 4 6 8 1 0 3 2 1 . 5 1 2 . 3 . 3 . 2 . 1 . 2 . 1 0 0 1 2 0 2 4 0 6 0 3 0 1 5 2 4 0 . 9 . 9 3 . 9 5 . 9 8 . 8 8 . 8 5 . 8 1 p u s h t o t r i p p u s h t o t r ip 40 0 250N P 9 3 0 8 3 1 .5 2 3 4 5 6 8 1 0 xI r I m .6 3 .7 . 8 .8 5 .9 . 95 .9 8 1 x In I r S T R 2 2 S E 9 0 1 0 5 % I r a l a r m I m I r I n = 2 5 0 A OFF M E R L IN G E R IN c o m p a c t N S 2 5 0 N U i 7 5 0 V . U i m p 8 k V . 2 2 0 / 2 4 0 3 8 0 /4 1 5 4 4 0 5 0 0 6 6 0 / 6 9 0 2 5 0 8 5 3 6 3 5 3 0 8 5 0 c a t A I E C 9 4 7 - 2 U T E V D E B S C E I U N E N E M A U e ( V ) I c u ( k A ) Ic s = 1 0 0 % Ic u 1 6 0 / 2 5 0 A p u s h t o t r i p p u s h t o t r i p R e s e t res et A p Ig I ∆n I s d I i I r Microlo gi c 7 0 I c s = 1 0 0 % I c u 2 2 0 / 4 4 0 5 2 5 6 9 0 1 0 0 1 0 0 8 5 I c w 8 5 k A / 1 s N X 3 2 H 2 c a t . B IE C 9 4 7 - 2 U T E V D E B S C E I U N E A S N E M A E N 6 0 9 4 7 - 2 5 0 / 6 0 H z U e I c u ( V ) ( k A ) 0 1 2 5 3 p u s h O F F p u s h O N O O F F d i s c h a r g e d 1 Contents Description Circuit breakers and system design The requirements for electrical power distribution Safety and availability of energy Structure of LV electrical power distribution Functions and technologies of protection devices Standard BS EN 60947-2 Current limitation Cascading Discrimination Earth leakage protection discrimination Range of circuit breakers Discrimination rules LV discrimination study Enhanced discrimination and cascading Supplementary requirements Transformer information Cable fault reduction 400Hz operation DC information Residual current device selection Circuit breaker markings LV switch disconnectors Technical data Cascading tables Discrimination tables Type 2 co-ordinationtables for motor protection Co-ordination with Telemecanique busbar Section 1 2 3 Page 3 55 77 2 1000 kVA 1000 A M M 100 A400 A 100 A 160 A 75 kW 16 A 20 kV/400 V 1000 kVA 1600 A 1000 kVA 19 kA 45 kA 60 kA 23 kA 70 kA main switchboard building utilities lighting, heating, etc. distribution board sub-distribution switchboard power distribution switchboard - industrial/commercial non-priority feeders priority feeders distribution distribution enclosure distribution workshop 1 3 Section 1 System requirements Circuit breakers and system design Safety and availability of energy Structure of LV electrical power distribution Functions and technologies of protection devices Standard BS EN 60947-2 Current limitation Cascading Discrimination Discrimination rules Earth leakage protection discrimination Coordination of protection devices Range of circuit breakers LV discrimination study Enhanced discrimination and cascading Page 5 6 7 10 15 19 21 25 26 28 30 43 46 4 Glossary EDW: SCPD: IEC: BS: CT: CU: MSB: BBT: MV: Isc: Isc(D1): Usc: MCCB: BC: Icu(*): IcuD1(*) Ue: Ui: Uimp: In: Ith: Ithe: Iu: Icm: Icu: Ics: Icw: Ir: 1.05 x Ir: 1.30 x Ir: Ii: Isd: ElectroDynamic Withstand Short circuit protection device International Electrotechnical Commission British Standard Current transformers control Unit Main Switchboard Busbar Trunking Medium Voltage (1kV to 36kV) Short-circuit current Short-circuit current at the point D1 is installed Short-circuit voltage Moulded case circuit-breaker Breaking Capacity Ultimate Breaking Capacity Ultimate Breaking Capacity of D1 Rated operational voltage Rated insulation voltage Rated impulse withstand voltage Rated operational current Conventional free air thermal current Conventional enclosed thermal current Rated uninterrupted current Rated short-circuit making capacity Rated ultimate short-circuit breaking capacity Rated service breaking capacity Rated short time withstand current Adjustable overload setting current Conventional non-tripping current Conventional tripping current Instantaneous tripping setting current Short time tripping setting current 5 The design of LV installations leads to basic protection devices being fitted for three types of faults: c overloads c short-circuits c insulation faults. Operation of these protection devices must allow for: c the statutory aspects, particularly relating to safety of people, c technical and economic requirements. The chosen switchgear must: c withstand and eliminate faults at optimised cost with respect to the necessary performance, c limit the effect of a fault to the smallest part possible of the installation in order to ensure continuity of supply. Achievement of these objectives requires coordination of protection device performance, necessary for: c managing safety and increasing durability of the installation by limiting stresses, c managing availability by eliminating the fault by means of the circuit-breaker immediately upstream The circuit-breaker coordination means are: c cascading c discrimination. If the insulation fault is specifically dealt with by earth fault protection devices, discrimination of the residual current devices (RCDs) must also be guaranteed. Safety and availability of energy are the operator s prime requirements. Coordination of protection devices ensures these needs are met at optimised cost. Safety and availability of energy The requirements of electrical power distribution 6 The various levels of an LV electrical installation Each of the three levels of the installation has specific availability and safety needs. Structure of LV electrical power distribution The requirements of electrical power distribution Simplified diagram of a standard installation covering most of the cases observed in practice. 1000 kVA 1000 A M M 100 A400 A 100 A 160 A 75 kW 16 A 20 kV/400 V 1000 kVA 1600 A 1000 kVA 19 kA 45 kA 60 kA 23 kA 70 kA main switchboard building utilities lighting, heating, etc. distribution board sub-distribution switchboard power distribution switchboard - industrial/commercial non-priority feeders priority feeders distribution distribution enclosure distribution workshop 1 Level A Level B Level C 7 Circuit-breaker functions This connection device is able to close and break a circuit regardless of current up to its breaking capacity. The functions to be performed are: c close the circuit, c conduct current, c open the circuit and break the current, c guarantee isolation. The requirements concerning installation, cost optimisation, management of availability and safety generate technological choices concerning the circuit-breaker. Level A: the Main Switchboard (MSB) This unit is the key to the entire electrical power distribution: availability of supply is essential in this part of the installation. c Short-circuit currents are high due to: v the proximity of the LV sources, v amply sized busbars for conveying high currents. cc cc c This is the area of the power circuit-breakers Functions and technologies of the protection devices Own current compensation diagram Protection devices and their coordination must be suited to the specific features of the installation. c At the main switchboard, the need for energy availability is greatest, c At the sub-distribution switchboards, limitation of stresses in event of a fault is important, c At final distribution, user safety is essential. 1/3 2/3 i i A i cc cc c Main data of these circuit-breakers: v of industrial type, meeting standard BSEN 60947-2, v with a high breaking capacity lcu from 40 to 150 kA, v with a nominal rating of 1000 to more than 5000 A, v category B: - with a high lcw from 40 kA to 100 kA — 1 s - with a high electrodynamic withstand (EDW), v with a stored energy operating mechanism allowing source coupling. Continuity of supply is ensured by total discrimination: v upstream with the protection fuses of the HV/LV transformer (*), v downstream with all the feeders (time discrimination). (*) The value of HV/LV discrimination lies above all in the fact that resumption of operation has fewer constraints in LV (accessibility, padlocking). This offers considerable advantages for continuity of supply. These circuit-breakers are designed for high current electrical distribution: v they are normally installed in the MSBs to protect high current incomers and feeders; v they must remain closed in event of short-circuits so as to let the downstream circuit-breaker eliminate the faults. Their operation is normally time-delayed. ElectroDynamic Withstand (EDW) and high thermal withstand characterised by a short time withstand current lcw are essential. EDW is designed to be as great as possible by an own current compensation effect. 8 Level B: the subdistribution boards These boards belong to the intermediate part of the installation: c distribution is via conductors (BBT or cables) with optimised sizing, c sources are still relatively close: short-circuit currents can reach 100 kA, c the need for continuity of supply is still very great. Protection devices must consequently limit stresses and be perfectly coordinated with upstream and downstream LV distribution. This is the area of the moulded case circuit-breakers These circuit-breakers must open and break the current as quickly as possible. The main need is to avoid as far as possible stresses at cable and connection level and even at load level. For this purpose, repulsion at contact level must be encouraged in order to eliminate the fault even as the current is rising. Fm i i Fm The possible diagrams are: c with a single repulsion loop, c with double repulsion c with an extractor, a magnetic core pushing or pulling the moving contact. Example of a repulsion diagram Fm = magnetic force The repulsion effects can be enhanced by implementation of magnetic circuits: c with effects proportional to the current square (U-shaped attracting or expulsion circuit), c with effects proportional to the current slope (di/dt) and thus particularly effective for high currents (lsc). Main data of the moulded case circuit-breakers: c of industrial type, meeting standard BSEN 60947-2, c with a high breaking capacity (36 to 150 kA), c with a nominal rating from 100 A to 1600 A, c category B for high rating circuit-breakers (> 630 A), c category A for lower rating circuit-breakers (< 630 A), c with fast closing and opening and with three operating positions (ON/OFF/ Tripped). Continuity of supply is ensured by discrimination: c partial, possibly, to supply non-priority feeders, c total for downstream distribution requiring high energy availability. The requirements of electrical power distribution 9 Level C: Final distribution The protection devices are placed directly upstream of the loads: discrimination with the higher level protection devices must be provided. A weak short-circuit current (a few kA) characterises this level. c This is the area of the Miniature Circuit-breaker i i Fm i These circuit-breakers are designed to protect final loads. The purpose is to limit stresses on cables, connections and loads. The technologies for the miniature circuit-breakers, mainly used at this installation level, prevent such stresses from occurring. In miniature circuit-breakers, limitation partly depends on the magnetic actuator. Once the mechanism has been released, it will strike the moving contact making it move at a high speed very early on. Arc voltage thus develops very quickly at a very early stage. For small rating circuit-breakers, specific pole impedance contributes to limitation. The miniature circuit-breaker is ideal for domestic use and for the protection of auxiliaries; it then conforms to standard BSEN 60898. On the other hand, if it is designed for industrial use, it must meet standard BSEN 60947-2. Main data of these circuit-breakers: cc cc c a breaking capacity to match needs (i.e. Below 10 kA on average), cc cc c a nominal rating of 1.5 to 125 A according to the loads to be supplied, cc cc c normally intended for domestic applications: conform to standard BSEN 60898. The protection devices installed must provide: cc cc c current limitation, cc cc c operating convenience, cc cc c absolute safety, as these devices are handled by non-specialist users. [...]... devices, by using circuit- breakers with standard performance Cascading provides circuit- breakers placed downstream of a limiting circuit- breaker with an enhanced breaking capacity The limiting circuit- breaker helps the circuitbreaker placed downstream by limiting high short -circuit currents Cascading makes it possible to use a circuit- breaker with a breaking capacity lower than the shortcircuit current... protection of people against indirect contacts 29 Range of circuit breakers The Merlin Gerin and Telemecanique circuit- breaker ranges cover all the requirements of LV electrical power distribution from 0.5 to 6300 A, i.e.: c the Merlin Gerin 630 to 6300 A Masterpact and power circuit- breaker ranges, c the range of Compact moulded case circuit- breakers (MCCB): v Compact CM from 1250 to 3200 A, v Compact... very important as it gives the ability of a circuit- breaker to provide totally normal operation once it has broken this short -circuit current three times The higher lcs, the more effective the circuit- breaker c Rated short time withstand current(*) (lcw) Defined for B category circuit- breakers lcw (kA rms) is the maximum short -circuit current that the circuit- breaker can withstand for a short period of... Moulded case circuit- breaker circuit- breaker or moulded case circuit- breaker Miniature circuit- breaker c c c (1) v (2) c c c 800 to 6300 A 50 kA to 150 kA B 100 to 630 A 25 kA to 150 kA A 1 to 125 A 3 kA to 25 kA A * (3) *** (1) for domestic use as per BSEN 60898 (2) possible up to 250 A (3) Sizing of the switchboard at level A means that this characteristic is not very important for standard applications... characterises the instantaneous short -circuit protection for all circuit- breaker categories For high overcurrents (short-circuits) greater than the li threshold, the circuit- breaker must immediately break the fault current This protection device can be disabled according to the technology and type of circuit- breaker (particularly B category circuit- breakers) 11 The requirements of electrical power distribution... discrimination v limiting downstream circuit- breakers Use of a limiting downstream circuit- breaker enables the discrimination limit to be increased non-limiting Ic short -circuit limiter Id ILd Id Isc (D2) In fact, when referring to the figure, a fault current ld will be seen by D1: v equal to ld for a non-limiting circuit- breaker, v equal to lLd < ld for a limiting circuit- breaker The limit of current and... defines two circuit- breaker categories: c category A circuit- breakers, for which no tripping delay is provided This is normally the case of moulded case circuit- breakers These circuit- breakers can provide current discrimination c category B circuit- breakers, for which, in order to provide time discrimination, tripping can be delayed (up to 1 s) for all short-circuits of value less than the current lcw This... category circuit- breakers designed for time-delayed tripping These circuit- breakers have a high thermal withstand (lcw > 50% lcn for t = 1s): ls > lcw1 Even for high lsc(D2), time discrimination normally provides total discrimination: lcw1 > lsc(D2) NB: Use of B category circuit- breakers means that the installation must withstand high electrodynamic and thermal stresses Consequently, these circuit- breakers... asymmetrical short-circuits (BSEN 60947.2 para 4.3.5.3.) lsc: symmetrical assumed short -circuit kA (root mean square value) 4,5 i I i 6 6 < I i 10 10 < I i 20 20 < I i 50 50 < I asymmetry factor k 1,5 1,7 2,0 2,1 2,2 c Rated short -circuit making capacity(*) (lcm) lcm (peak kA) is the maximum value of the asymmetrical short -circuit current that the circuit- breaker can make and break For a circuit- breaker, the... defined for a specific voltage rating Ue 12 Circuit- breaker coordination The term coordination concerns the behaviour of two devices placed in series in electrical power distribution in the presence of a short -circuit c Cascading or back-up protection This consists of installing an upstream circuit- breaker D1 to help a downstream circuit- breaker D2 to break short -circuit currents greater than its ultimate