The Selectivity Part -1

8/12/2019 The Selectivity Part -1

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1SDC007100G0202

Technical Application PapersFebruary 2006

1

Low voltage selectivity

with ABB circuit-breakers


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1

Index

A theoretical outline ofselectivity

Introd uction ............................................................. 2

Main definitionsS electivity ................................................................ 3

Tota l selectivity - P a rtia l selectivity ......................... 3

Overloa d zone S hort-circuit zone ..... .. . . . . .. . . . . . .. . . . . 4

Rea l currents circula ting in the circuit-breakers ..... 5

Selectivity techniquesTime-current se lectivity ........................................... 7

Current selectivity ................................................... 8

Time selec tivity ....................................................... 9

Energy selectivity .................................................. 10

Zone selectivity ..................................................... 11

How to obtain selectivity withABB circuit-breakers

Types of AB B circuit-brea kers .............................. 12

MCB Minia ture C ircuit-Brea kersS upply-side S200 /Load -side S200 ..................... 13

S upply-side S 290D-S 500D /Load -side S 200 ...... 13

MC C B -MCB S elec tivityS upply-side T1-T2-T3-T4 / Load -side MCB ...... ... 14

S upply-side T5-T6-S 7-S 8 /Load -side MCB ........ 15

Low volta ge selec tivity w ith AB B c ircuit-brea kers

Technical Application Papers

MCCB-MCCB SelectivityCurrent selectivity ................................................. 16

Time selectivity ..................................................... 17

Energy selectivity .................................................. 18

Zone selec tivity (T4L-T5L-T6L) ... ... ... ... ... ... ... ... ... .. 19

ACB-MCCB SelectivityTraditiona l s olution ................................................ 25

Zone selectivity betw een Emax a nd Tmax ....... . . . . 26

ACB-ACB SelectivityTime selectivity ..................................................... 28

Zone s electivity b etween Emax ..... .. . . . . .. . . . . . .. . . . . .. . . 29

Direc tiona l time se lectivity .................................... 32

Direc tiona l zone selectivity ................................... 34

Appendix A:

MV/LV se lec tivity ...... ...... ..... ...... ...... ..... ...... ...... ..... 40

Appendix B:

G eneral cons ide rations reg a rding residual current

se lectivity .............................................................. 43

Appendix C:

Example of LV/LV se lec tivity stud y ...... ...... ..... ...... 45

Appendix D:

Further co nsiderations reg a rding the rea l currents

circula ting in the circuit-breakers .......................... 48

Glossary .............................................................. 52


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2 Low voltage selectivity with ABB circuit-breakers


A theoretical outline of selectivity

P rob lems a nd req uirements for theco ordination of the protec tions

Selection of the protection system of the electrical in-

sta lla tion is fundam enta l bo th to guarantee c orrect ec o-

nomical a nd functiona l service of the who le insta lla tion

and to reduce the problems caused by abnormal ser-

vice co nditions or ac tual faults to a minimum.

Within the sphere of this analysis, the coordination be-

tween the various devices dedicated to protection of

sections of installation or specific components is stud-

ied in order to:

guarantee s afety of the insta llation and of people in allc ases ;

rapidly ide ntify and exclude just the a rea involved in

the problem, without indiscriminate trips which reduce

the availability of energy in areas not involved in the

fault;

reduce the effects of the fault on o ther integral parts o f

the insta lla tion (red uction in the voltag e va lue, a nd loss

of stability in rotating machines);

reduce the stress on components a nd dama ge to the

a rea involved;

guarantee s ervice continuity with good q uality powe r

supply voltage;

guarantee ad equa te support in the cas e of malfunction

of the protection delegated to opening; provide the personnel in cha rge of maintenance and

the management system with the information needed

to restore se rvice to the rest of the netw ork as rapidly

as possible and with the least interference;

a chieve a g ood c ompromise b etw een relia bi lity ,

simplicity and co st-effectiveness .

In deta il, a goo d protection sys tem must be ab le to:

perceive wha t has ha ppened a nd where, disc riminating

between abnormal but tolerable situations and fault

situations within its zone of competence, avoiding

unwa nted trips w hich ca use unjustified s toppa ge o f a

so und pa rt of the insta llation; a c t a s ra p i d ly a s p o s s ib le t o lim it t h e d a m a g e

(destruction, accelerated ageing, etc.), safeguarding

power supply continuity and stability.

The so lutions c ome from a c ompromise b etw een thes e

tw o a ntithetic requireme nts precise identifica tion of the

fault and rapid tripping - and are defined according to

which req uirement is privileg ed .

For example, in the case where it is more important toprevent unwa nted trips, a n indirec t protection sys tem is

gene rally preferred , ba se d on interloc ks and d a ta trans -

miss ion be tw een different device s w hich loc a lly mea sure

the electrical values, whereas speeds and limitation of

the destructive effects of the short-circuit require direct

action systems with with protection releases integrated

directly in the devices. In low voltage systems for pri-

mary and secondary distribution, the latter solution is

norma lly preferred .

With regard to the Italian Standard CEI 64-8 Electrical

user installations with rated voltage below 1000 V in al-

terna ting current a nd 1500 V in direc t c urrent reg a rding

low volta ge insta llations, under P art 5 S elec tion a nd in-

stallation of the electrical components this states that:

Selectivity between protection devices againstovercurrents (536.1)When s everal protec tion d evices are place d in s eries a nd

when the s ervice need s justify it, their operating c harac -

teristics must be selected s o a s to disconnect o nly the

part of the installation where the fault is.

Moreover, in the c omments , the follow ing is a dd ed :

The op erat ing s itua tions w hich req uire select ivity a re

defined b y the custo mer or by the d es igner of the insta l-

lation.

The S tand a rd therefore sta tes tha t the operating cha r-

acteristics must be selected so as to have selectivity,

when the s ervice need s justify this.

In general, designing a selective installation not only

means realising a state-of-the-art project, but also

des igning a goo d installation which d oes , in fact, respo nd

to the customers requirements, not simply to the as-

pects of the Standa rds.


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3Low voltage selectivity with ABB circuit-breakers

Atheoreticaloutlineof

selectivity

Main definitions

Selectivity

The de finition of se lec tivity is given b y the IEC 60947-1

S tand ard Low voltag e eq uipment - P art 1: G eneral rules

for low voltag e eq uipment

Trip selectivity (for overcurrent) (441-17-15)Coordination between the operating characteristics of

two or more overcurrent protection d evices , so that w hen

a n overcurrent w ithin es tab lished limits oc curs, the de-

vice des tined to o perate within thos e limits trips whereas

the others d o not trip

where b y overcurrent a current of a higher va lue tha n the

rated current is intended, due to any cause (overload,

sho rt-circuit, etc .).

There is therefore se lec tivity b etw een tw o c ircuit-brea k-

ers in series when, for an overcurrent which passes

throug h bo th, the load -side circuit-brea ker opens thereby

protecting the circuit, whereas the supply-side one re-

mains closed guaranteeing power supply to the rest of

the installation.

The d efinitions o f tota l selectivity a nd pa rtia l selectivity

are, on the other hand , given in Pa rt 2 of the sa me S tand -

a rd IEC 60947-2 Low voltag e Eq uipment - P a rt 2: C ir-

cuit-breakers

Total selectivity (2.17.2)Overcurrent selectivity w here, in the prese nce of tw o pro-

tection devices against overcurrent in series, the load-

side protection de vice ca rries out the protection without

making the other device trip.Partial selectivity (2.17.3)Overcurrent s electivity w here, in the prese nce of tw o pro-

tection devices against overcurrent in series, the load-

side protection device ca rries out the protection up to a

given level of overcurrent, without making the other de-

vice trip.

One can spea k of total selectivitywhe n there is selec-tivity for any overcurrent value possible in the installa-

tion.

Between a pair of circuit-breakers, one speaks of total

selectivity when there is selectivity up to the lesser of

the Icu values of the tw o c ircuit-brea kers, s ince the ma xi-

mum pros pec tive s hort-circuit current o f the insta lla tion

will in any c a se b e les s o r equa l to the s ma llest o f the Icu

values of the two circuit-breakers.

One talks about partial selectivity when there is onlyselectivity up to a certain Iscurrent value (ultimate se-lectivity value). If the current exceeds this value, selec-

tivity between the two circuit-breakers will no longer be

guaranteed.

Between a pair of circuit-breakers, one speaks about

pa rtia l se lec tivity w hen there is s electivity up to a ce rtain

Is value below the Icuvalues of the two circuit-break-ers. If the maximum prospective short-circuit current of

the insta llation is lowe r than or eq ual to the Iss electivityvalue, one can still speak of total selectivity.

ExampleThe following two circuit-breakers are considered:On the supply side T4N250 PR221 In250 (Icu= 36kA)

On the loa d s ide S 294 C 100 (Icu= 15kA)

From the C oordination Tab les publica tion it ca n be seen that there

is tota l se lectivity (T) be tw een th e tw o c ircuit-brea kers.

This mea ns tha t there is selec tivity up to 15kA, i.e. the

lower of the two Icu values.

Obviously, the ma ximum po ss ible s hort-circuit current a t the point

of insta llation of the S 294 C 100 c ircuit-brea ker will be less than or

equal to 15kA.

Now the following two circuit-breakers are considered:On the supply side T4N250 PR221 In160 (Icu= 36kA)

On the loa d s ide S 294 C 100 (Icu= 15kA)

ELTM, M

Supplyside

Version

Release

Iu[A]

In[A]

80

100

125

80100

5

5*

5

250

16 0 2 00 25 0 32 0

320 250 320

160 250 320

11

8

8*

118

T

T

12

T

T

T

T

TT

T

12

T12

T

T

T

TT

T

T

T

TT

T

N,S H,L,V

T4

Icu [kA]

15

Charact .

C-K

C

D

Load-side

S290

* Value va lid w ith magne tic only circuit-breaker on the suppy side

T4N 250 PR221DS-LS/I

S 294 C 100

Tmax T4 - S290 @ 400/415 V

From the Co ordination Ta bles p ublica tion it ca n be s een tha t the

selectivity va lue is Is= 12kA betw een the two circuit-brea kers.

This mea ns that, if the m aximum prospe ctive sho rt-circuit current

on the loa d-side o f the S294 C 100 circuit-breaker is less t ha n 12kA,

there will be total selectivity, whereas if the short-circuit current

has a higher va lue, there w ill be pa rtial se lectivity, i.e. only for the

faults with a current below 12kA, whereas for faults between 12

and 15 kA non-tripping of the supply-side circuit-breaker is not

guaranteed.


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selectivity

Overload zone Short-circuit zone Byshort-circuit zoneone mea ns the ranges of currentvalues, and therefore the relative part of the trip curvesof the circuit-breaker, which are 8-10 times higher than

the rated current of the circuit-breaker.

This is the zo ne in w hich the m a gne tic prote ction for

thermomagnetic releases or protections S, D and I for

electronic releas es a re normally c a lled on to intervene.

These current va lues usua lly c orres pond to a fault on

the s upply circuit. This event is mos t unlikely tha n a simple

overload.

For the purpos es of the s elec tivity a nalysis ma de in this

publica tion, the co ncepts o f overloa d zone and short-

circuit zone are introd uced .

B yoverload zone one means the ranges of currentvalues, and therefore the relative part of the circuit-

breaker trip curves co ming b etw een the rated current of

the circuit-breaker itself and 8-10 times this value.

This is th e zo ne in which the the rmal prote ction for

thermomag netic relea se s and protec tion L for elec tronic

relea ses a re no rmally c a lled on to intervene.

Thes e currents us ually co rres pond to a circuit where a

loa d results to b e ove rloa de d. This e vent is likely to o cc ur

more frequently than a real fault.

0.1kA 1kA 10kA

104s

103s

102s

10s

1s

10-1s

10-2s

0.1kA 1kA 10kA

104s

103s

102s

10s

1s

10-1s

10-2s

Overload Zone = In 8-10In Short-circuit Zone => 8-10In

Main definitions


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selectivity

Rea l currents circula ting in the circuit-breakers

When the time-current c urves of tw o c ircuit-breakers a re

compared, one is often led to assess the trip times of

the two d evices as if they were pa ss ed through by the

same current.

This co nsideration is only true when, b etw een the two

circuit-breakers placed in series, there are no other

shunts, i .e. there is a single incoming and a single

outgoing feeder which insist on the same node.

When, on the other ha nd, the re a re s everal supply-side

circuit-breakers which insist on the same busbar or

several outgoing feeders on the load side, the currents

w h i c h p a s s t h r o u g h t h e a p p a r a t u s c a n b e e v e nco nsiderab ly different.

With rega rd to the rea l currents circulating in the circuit-breakers, the three ma in ca ses which c an b e c onsideredare a s follows :- a s ingle circuit-brea ker on the supply side o f a single

circuit-brea ker on the loa d side (pa ss ed through b y thesame current)

- a s ingle circuit-brea ker on the supply side of se vera lcircuit-breakers on the load side (supply-side circuit-breaker passed through by a current higher than thatof the load-side circuit-breaker)

- two o r more circuit-brea kers on the supply side a nd

severa l circuit-brea kers on the loa d side.

Where:IB

is the overcurrent w hich pa ss es through circuit-breaker B

IA

is the overcurrent w hich pa ss es through circuit-breaker A

Iloads

is the sum of the currents which, during normal operation, is consumed by the loads (excluding B) supplied by the supply-side

circuit-breaker A. This s um ca n, if neces sa ry, be c orrecte d w ith suitable co ntempo raneity and us e fac tors

n is the number of circuit-breakers placed in parallel on the power supply side.

* These formulas do not ta ke into a cco unt the different phase d isplac ement of the c urrents or a ny as ymmetry of the circuit; the first two formulas arehowever conservative and the third one is acceptable when the two supply circuits are equal.

tA

tB

IA IB

IB IA

tA

tB

IA=IB

tA

tB

IA= IB + Iloads

IA= (IB + Iloads )/n

IA= IB

A

B

A

B

A

B


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This se ction de sc ribe s the d ifferent selectivity tec hniq ues and their area of a pplica tion.

In the o verloa d zone with the protections in pla y, time-currenttype selectivity is usually realised.

In the short-circuit zone with the protections in play, various selectivity techniques can be used. In particular, the

follow ing will be illustrated in the pa ragra phs below:

current selectivitytime selectivityenergy selectivityzone selectivity.

After an initial theoretical description of the different selectivity techniques, the selectivity technique which can be

used a ppropria tely for the d ifferent types of c ircuit-breakers w ill then b e a nalysed .


selectivity

S elec tivity techniq ues


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Time-current se lec tivity

In general, the protec tions a ga inst overloa d ha ve a d efi-

nite time c harac teristic, whether they are mad e b y mea ns

of a thermal release or by means of function L of an

elec tronic releas e.

A definite time characteristic is intended as a trip

characteristic where, as the current increases, the trip

time o f the c ircuit-breaker dec rea se s.

When there a re p rotec tions with cha racte ristics of this

type, the selectivity technique used is time-currentselectivity.

Time-current se lec tivity makes trip s electivity b y a djusting

the protections so that the load-side protection, for all

possible overcurrent values, trips more rapidly than the

sup ply-side circuit-breaker.

When the trip times of the two circuit-breakers are

ana lysed, it is necess ary to c onsider:

- the toleranc es over the thresholds a nd trip times

- the real c urrents circulating in the circuit-brea kers.

Operatively speakingWith rega rd to the tolerance s, ABB S ACE ma kes the trip curves o f their releas es a vaila ble in the tec hnica l ca talog ues a nd in the DOCWin

software. In particular, in the curve module of the DOCWin software, the curves of both the electronic and thermomagnetic releases

include the toleranc es. A releas e trip is therefore show n by tw o c urves, one w hich indicates the highest trip times (top curve), a nd the o ther

which indica tes the mos t rapid trip times (bo ttom c urve).

For a correct analysis of selectivity, the worst conditions must be considered, i.e.:

- the supply-side circuit-brea ker trips a cco rding to its own bottom c urve

- the loa d-side circuit-breaker trips a cco rding to its ow n top curve

With regard to the real currents circulating in the circuit-breakers:

- if the two c ircuit-breakers are pas sed through by the s ame current, it is s ufficient for there to b e no o verlapping betw een the curve of

the s upply-side c ircuit-brea ker and the c urve of the loa d-side c ircuit-breaker;

- if the two c ircuit-breakers a re pa ssed through by different currents, it is nec essa ry to select a s eries o f significa nt points on the time

current curves and check that the trip times of the supply-side protection are always higher than the corresponding times of the load

side protection.

1.05 x I1 of the supply-side circuit-breakerAssuming I

A=1.05xI1,with reference to w hat has been sa id a bout

the rea lcurrents which c irculate in the circuit-breakers, the IBc urrent

is ob tained on the loa d side.

The trip times o f the two devices are o bta ined from the time-current

curves.

1.20XI3 (or I2) of the load-side circuit-breakerAssuming I

B= 1.20XI3 (or I2),the I

Acurrent is obta ined in the sa me

way on the supply side and, from the time-current curves, the trip

times of the two devices are obta ined.

If the follow ing is true for both the points c ons idered:

tA>t

B

then selectivity in the overload zone is guaranteed.

1 1.05 is the value for minimum definite non- intervention dict ated by the Stand ard (IEC60947-2 ). For some types of c ircuit-b reakers this value could vary

(see the techn ical catalogue for further inform ation).

2 1.2 is the value for maximum d efinite intervention for protect ion against short-circuit dic tated by the Standard (IEC60947-2). For some types of circuit -

breakers this value could be lower (see the technical catalogue fo r further information ).

A

B

In particular, in the c as e o f circuit-breakers e q uipped with electronic releases, since the trend of the curves is at I2t= cons t, to ca rry outthe c heck co rrec tly, it is sufficient to exa mine two c urrent values:

1.05 x I11 of the supply-side circuit-breaker (value below which the supply-side protection never intervenes)

1.20XI3 (or I2)2 of the loa d-side circuit-breaker (value ab ove w hich the loa d-side protection certainly trips w ith the protec tions ag ainst

short-circuit)

Time-current Selectivity

0.1kA 1kA 10kA 100kA

A

B

103s

102s

10s

1s

10 -1s

0.1kA 1kA 10kA 100kA

0.1s

1s

10s

100s

1E3sA

B

Time-current Selectivity


selectivity

In the figure at the side a n ab sorption of current from other loa ds ha s be en

assumed


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Time s elec tivity

This type of s electivity is a n evo lution o f the p revious

one. In this type of coordination, apart from the trip

threshold in terms of current, a trip time is also defined:

a c ertain current va lue w ill ma ke the protec tions trip a fter

a de fined t ime d elay, suita ble for allow ing a ny protec tions

plac ed closer to the fa ult to trip, excluding the area which

is the s ea t of the fault.

The s etting stra teg y is the refore to prog res sively increa se

the current thresholds and the trip delays as one gets

closer to the power supply sources (level of setting

direc tly c orrelate d to the hierarchica l level).

The d elayed trip thresho lds must ta ke into a cc ount the

tolerances of the two protection devices and the effective

currents which circulate in them.

The d ifference b etwe en the delays set for the protec tions

in series must take into account the fault detection and

elimination times of the device on the load side and of

the inertia time (overshoot) of the device on the supply

side (time interval during which the protection can trip

even w hen the pheno menon is over).As in the ca se of current s elec tivity, the study is ma de by

comparing the time-current trip curves of the protection

devices.

G enerally this type o f co ordination:

- is eas y to study and realise;

- is not very costly with rega rd to the protection

system;

- al low s even high s elec t ivity limit va lues to be

ob ta ined (if Icw is hig h);

- allows redundanc y of the protection functions.

However:

- the trip times a nd energy levels let through b y the

protections, espec ially by those close to the s ources ,

a re high.

It is a type of selectivity which ca n also be ma de b etwe en

c i rcu i t -breakers o f the same s i ze , equ ipped w i th

electronic relea ses with delaye d protection a ga inst s hort-

circuit.

Operatively speaking

The protec tions a ga inst s hort-circuit of the two circuit-breakers w ill be s et:

- w it h t he I2 trip thresholds against delayed short-circuit adjusted so as not to create trip overlapping,taking into cons idera tion the tolerance s a nd the real currents c ircula ting in the circuit-breakers.

- w ith t2 trip times adjusted so that the load-side circuit-breaker B extinguishes the fault whereas thesupply-side circuit-breaker A, still in the timing phase, manages to see the extinction of the currentand therefore remains closed.

The ultima te s elect ivity limit which is ob ta ined is eq ua l:

to the instantaneo us trip threshold o f the supply-side protection,

if this function is enabled, less any tolerance:

Is = I3minA

to the va lue of Icwfor s upply-side air circuit-breakers when theinsta ntane ous p rotection function is set to OFF.

Note

These selectivity limits are exceededin all the cases where energy typ e

selectivity is realised.

If the settings indicated for energy selectivi ty are respected for the

com binations of circ uit-b reakers with an energy selectivity value given in the

coord ination tables published by ABB, the selectivity limit to be taken into

consideration is the one given in the tables and not the one whic h can be

obt ained from the considerations mad e in this paragraph. 0.1kA 1kA 10kA 100kA

Time Selectivity

A

B

Is103s

102s

10s

1s

10 -1s

10 -2s

104s

A

B


selectivity


12/16



Energy selectivity

Coordination of energy type is a particular type ofse lec t iv i ty which exp lo i t s the curren t- l imi t ingcharacteristics of moulded-case circuit-breakers. It ispointed out that a current-limiting circuit-breaker is acircuit-brea ker with a s ufficiently sho rt trip time to p reventthe short-circuit current from reaching the peak valuewhich would otherwise be reached (IEC 60947-2).In practice, all the ABB SACE moulded-case circuit-breakers of the Iso ma x and Tma x series , the mod ula rcircuit-breakers and the E2L E3L air current-limitingcircuit-breakers have mo re o r les s ma rked current-limitingcharacteristics.

Und er short-circuit cond itions , thes e c ircuit-brea kers a reextremely fas t ( tr ip t imes in the region of a fewm i l l i s e c o n d s ) a n d o p e n w h e n t h e r e i s a s t r o n g

a symme trica l co mponent. It is therefore not po ss ible touse the time-current trip curves of the circuit-breakers,obtained with symmetrical sinusoidal types of waveforms, for the c oordination s tudy.The phe nome na a re ma in ly dy na mic (there foreproportional to the square of the instantaneous currentvalue) and are heavily dependent on the interactionbetw een the tw o pieces of a ppa ratus in series. Thereforethe energy selectivity values cannot be determined bythe end user.The ma nufac turers ma ke t ab les , s lide -ru les a ndcalculation programmes available where the ultimatecurrent s electivity va lues o f Isunder s hort-circuit betw eendifferent combinations of circuit-breakers are given.

Thes e va lues a re de fined b y theoretica lly integ rating theresults of tests carried out in compliance with what isindicated in Annex A of the IEC 60947-2 Standard.

Operatively speaking

The Isultimate selectivity limit obtained is the one given in the tables which ABB SACE makes available to the customer.

The protections a ga inst s hort-circuit of the tw o c ircuit-breakers must resp ect the co nditions given below.

- Supply-side release of thermomagnetic typethe ma gnetic trip thresho lds must be s uch so as not to c reate trip overlap ping, ta king into cons ideration the tolera nces

a nd t he rea l currents circulating in the c ircuit-breakers;

the ma gnetic threshold of the s upply-side circuit-breaker must be e q ual to or higher tha n10xIn or set to the ma ximum

value when it is adjustable.

- Supply-side release of electronic typeany protections against delayed short-circuit S must be adjusted following the same indications as time selectivity;

the instantaneous protection function I of the supply-side circuit-breakers must be set to off

I3=OFF

B

Supplyside

T5

N,S,H,L,W

Release

In[A] 400 630 400 630

TM LL

Version

Load side

T3

N

S

TM 160

In[A]

63

80

100

125160

200

250

63

80

100

125

160

200

250

25

25

25

20

25

25

25

20

25

25

25

20

25

25

25

20

25

25

25

2020

25

25

25

20

20

25

25

25

2020

20

20

25

25

25

20

20

20

20

25

25

25

2020

20

20

25

25

25

20

20

20

25

25

25

2020

20

20

25

25

25

20

20

20

20

25

25

25

2020

20

20

25

25

25

20

20

20

20

A

Energy Selectivity

0.1kA 1kA 10kA

A

B

Is

103s

102s

10s

1s

10 -1s

10 -2s

A

B


selectivity

S elec tivity techniq ues


13/16


Zone selectivity

This type of c oo rdinat ion is a n evolut ion o f t ime

coordination.

In gene ra l, zone s electivity is ma de b y mea ns o f dia log ue

betw een the current mea suring d evices which, once the

setting threshold has been detected as having been

exceeded, allows just the fault zone to be identified

co rrectly and the pow er supply to it to b e cut off.

It ca n be realised in two w ays :

the mea suring d evices se nd the informa tion linked to

the current setting thresho ld ha ving b een exce ed ed to a

supervision system and the latter identif ies which

protec tion ha s to intervene;

when the re a re current va lues highe r than their se tting,

eac h protection send s a lock signal by means of a direct

connection or a bus to the hierarchically higher level

protection (on the supply side in relation to the power

flow direction) and, before intervening, checks that a

similar lock signal has not arrived from the load-side

protection. In this way only the protection immediately

to the supply side of the fault intervenes .

The se co nd c a se a llow s d efinitely shorter trip times .

Compared with coordination of the time type, the need

to increase the intentional delay a s one moves towa rds

the pow er supply source is no long er neces sa ry. The

delay ca n be reduced to the time needed to exclude the

presence of a pos sible lock signa l com ing from the load -side protec tion.

This is a type o f se lec tivity s uita ble for rad ia l netw orks

and , w hen a ss ociated with the d irectional protection, a lso

suitable for meshed networks.

Co mpa red with coo rdination of time type, zone s electivity

allows:

- reduction of the trip times (these c an b e lower than

hundred millise co nds );

- reduction both of the dama ge c aused b y the fault and

of interferences to the pow er supply sys tem;

- reduction of the thermal and dynamic stress es on the

co mponents of the insta lla tion;

- a very high number of selec tivity levels to b e ob tained.

However:

- it is more burdensome b oth in terms of cos t and o f

complexity of the installation

- it requires an a uxilia ry supply.

This s olution is therefore ma inly use d in sys tems with

high rated current and short-circuit current values, with

sa fety and se rvice c ontinuity req uirements which a re b oth

binding: in particular, there are often examples of logical

se lec tivity in prima ry distribution s witchg ea r immed ia tely

to the load side of transformers and generators.

Aremains closedBopens

AopensBrema ins c los ed

A

B

Fault c urrent

Lock signa l

A

B

Fault c urrent

Lock signa l

Operatively speakingThis is a type o f selectivity which c a n be realised :

- between Ema x air circuit-breakers eq uipped w ith PR122 and P R123 releas es.

The ultima te s electivity limit which c a n be ob tained is eq ual to the Icw Is = Icw- betw een Tma x T4L,T5L a nd T6L moulded-ca se c ircuit-breakers eq uipped with PR223 EF releas es.

The ultima te s electivity limit which ca n be ob tained is 100kA Is = 100kA

Then, by mea ns of the a dd itiona l IM210mod ule, it is po ss ible to ma ke a cha in of zone s electivity betw een Tma x and Ema x. It is a lsopos sible to realise a selectivity c hain including ABB MV protections.

The o perating principle of zone selectivity be twee n ABBcircuit-breakers is a s fo llows:When there are current values higher than their sett ing, ea ch protec tion se nds a loc k signa l by mea ns of a d irect c onnec tion or a b us to the

hierarchically higher level protection (on the supply side in relation to the power flow direction) and, before intervening, checks that a

simila r loc k signal has not a rrived from the load -side protection. In this w a y only the protection immediately to the supply side of the fault

intervenes.


selectivity


14/16



How to obtain selectivity with ABB circuit-breakers

MCB

Minia ture C ircuit-Brea kers

These are the S ystem Pro-Mseries of circuit-breakers.

They a re eq uipped with thermomag netic relea ses whos e

trip characteristics conform to the IEC60898 Standard

a nd to the DIN VDE 0660 Sta nda rd.

Thes e circuit-breakers ha ve the b reaking ca pa city (Icu)

co mplying w ith the Sta nda rd IEC 60947-2 and the e nergy

selectivity limits refer to this Standard.

ACB

Air Circuit-Breakers

Thes e a re the Ema x series of circuit-breakers.

They ca n be eq uipped with electronic relea ses .

The mos t ad vanc ed e lectronic relea ses of the Emax

se ries a re the PR 122/P, w hich a llow s z one s electivity to

be rea lised , a nd the P R123/P which, ap a rt from zo ne

se lectivity, a lso a llow s direc tiona l zone se lectivity to be

realised.

MCCB

Moulded-Case Circuit-Breakers

Thes e a re the Tma x and Iso ma x series o f circuit-brea kers.

They ca n be eq uipped with thermoma gne tic or electronic

releases.

The mos t a dva nce d elect ronic releas e of the Tma x series

is the PR223EF which allows zone selectivity to be

realised between moulded-case circuit-breakers.

Types of AB B c ircuit-brea kers

How to o bta in s elec tivity w ith the d ifferent types of AB Bcircuit-breakers will be analysed in details in the next

chapters.

Each chapter is ded ica ted to a particular co mbination of

circuit-brea kers a nd to the metho ds to realise selectivity

be twe en them.This pub blica tion gives indica tions for

rapid s election o f the c ircuit-brea ker a djustme nts in order

to obtain selectivity.

These indications a bo ut ad justments of the relea ses a re

generally valid and are used for rapid selection of the

settings.

For specific combinations of circuit-breakers and forspecific installation conditions, ABB SACE may provide

indica tions which d o no t respec t the rules given in this

document.

Here is a short description of the different types of ABB

c i rcu i t -breakers t aken in to cons idera t ion in th i s

publication.


15/16


16/16

14 L l l h ABB b k


Supply-side T1-T2-T3-T4 / Load-side MCBIn the Co ordina tion Ta bles pub lica tion, there a re tab les w ith circuit-brea kers of the Tma x T1, T2, T3

and T4 series o n the supply side of the mo dular circuit-breakers of the S 200, S290 and S 500 series.

The energy s electivity va lues given are va lid o nce t he co nditions des cribed below a re verified.

The ca se w here selectivity is looked for bet we en amoulded-case circuit-breaker on the supply side and a

modular circuit-breaker on the load side is now ana lysed .

The Isultima te s electivity limit which is ob ta ined is the o ne g iven in the Co ordination Tab les p ublica tion

Overload zoneIn the overload zone,the loa d-side c ircuit-breaker mus t trip mo rerapidly than the supply-side circuit-breaker, ta king into c ons idera tion

the tolerances and the real currents circulating in the circuit-

breakers.

Short-circuit zoneSupply-side circuit-breaker of thermomagnetic typeThe ma gnetic trip thresho ld mus t be:

- higher than or equa l to 10xIn when the mag netic threshold is

fixed (TMD)

- set to the maximum value when the mag netic threshold is

a djus ta ble (TMA)

- such so a s not to create trip overlapping with the loa d-side

circuit-breaker, taking into consideration the tolerances and

the real currents circulating in the circuit-breakers.

Supply-side circuit-breaker of electronic typeThe instanta neous protection functionImust be set to OFF

I3=OFF

The I2current thresho ld of function S, less any toleranc e, must be

ad justed s o a s not to c reate trip overlapping w ith the upper mag neticthreshold of the load-side circuit-breaker I3

MaxB, taking into

co nsideration the real currents circulating in the c ircuit-breakers.

With regard to the t2 trip time of function S:

t2A100ms both w ithI2t=const as well witht=const

HowtoobtainselectivitywithABBcircuit-breake

rs

Selectivity between T2160 PR221 In100 and S280 C50

0.1kA 1kA 10kA

103s

102s

10s

1s

10-1s

10 -2s

104s

Is

B

A

B

Supply side

Release

Iu[A]

Version

Load side In[A]Icu [kA]Charact.

TM,M

N,S,H,L

T2

EL

160

C

B -C

S200P

25

15

12.5 16 20 25 32 40 50 63 80 100 125 160 10 25 63 100 160

2

3

4

6

8

10

13

16

20

25

32

40

50

63

T

15

15

5.5*

T

15

15

5.5

T

15

15

5.5

5.5

3*

3*

T

15

15

5.5

5.5

3

T

15

15

5.5

5.5

3

3

3*

3*

T

15

15

5.5

5.5

3

3

3

T

15

15

5.5

5.5

4.5

4.5

4.5

3

3*

3*

T

15

15

10.5

10.5

7.5

7.5

5

5

5

T

15

15

15

15

8.5

7.5

7.5

6

6

6

5.5*

3*

T

17

17

17

17

17

12

12

10

10

7.5

7.5

5*

5*

T

T

T

T

T

T

20

20

15

15

12

12

7.5

T

T

T

T

T

T

T

T

T

T

T

T

10.5

10.5

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

10.5

T

T

T

T

T

T

T

T

T

T

T

T

10.5

10.5

A

MC CB -MC B S elec tivity

In this ca se , tha nks to the different s ize o f the tw o c ircuit-breakers, it is a lwa ys po ss ible to ob ta in energy se lec tivity.

A

B

Documents

The Selectivity Part -1