Q.org - Organic Synthesis II Selectivity and Control. Handout 1
The Selectivity Part -1
Transcript of 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
Technical Application Papers
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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4 Low voltage selectivity with ABB circuit-breakers
Technical Application Papers
Atheoreticaloutlineof
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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5Low voltage selectivity with ABB circuit-breakers
Atheoreticaloutlineof
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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6 Low voltage selectivity with ABB circuit-breakers
Technical Application Papers
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 .
Atheoreticaloutlineof
selectivity
S elec tivity techniq ues
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7Low voltage selectivity with ABB circuit-breakers
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
Atheoreticaloutlineof
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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9Low voltage selectivity with ABB circuit-breakers
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
Atheoreticaloutlineof
selectivity
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10 Low voltage selectivity with ABB circuit-breakers
Technical Application Papers
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
Atheoreticaloutlineof
selectivity
S elec tivity techniq ues
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11Low voltage selectivity with ABB circuit-breakers
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.
Atheoreticaloutlineof
selectivity
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12 Low voltage selectivity with ABB circuit-breakers
Technical Application Papers
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.
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14 L l l h ABB b k
Technical Application Papers
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