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An Adaptive Protection Algorithm for Distribution

Systems with Distributed Generation

Jamile Pinheiro Nascimento

Department of Electrical EngineeringFederal niversity of !ampina Grande "F!G#

!ampina Grande$ P%& %ra'il

(amile&nascimento)ee&ufcg&edu&br

Nubia Silva Dantas %rito$ %enemar Alencar de Sou'a

Department of Electrical EngineeringFederal niversity of !ampina Grande "F!G#

!ampina Grande$ P%& %ra'il

nubia)dee&ufcg&edu&br

benemar )dee&ufcg&edu&br

Abstract An adaptive protection algorithm is proposed to solve

protection coordination problems in distribution systems with

distributed generation is proposed. The algorithm modifies

relays settings on-line, using circuit breakers state as input

information. At the end, it was found that even with the

connection or disconnection of distributed generators (D!,

distribution system continued to be protected. The "### $%

node test system and the &eal Time Digital 'imulator (&TD'!

were used to validate the proposed algorithm

Index Terms-- Adaptive protection, distributed generation,

overcurrent relay.

*& *N+,-D!+*-N

-ver the past years$ the technology advances wereachieved due to electricity ./0$ which is delivered to the finalcustomers according to the generation$ transmission anddistribution processes& +his traditional arrangement follows anassumption of the unidirectional power flow$ in ordergeneration1consumption& 2owever$ this conventional model ischanging$ due to the gradual inclusion of generating units inelectrical distribution systems "EDS#$ called distributedgeneration "DG#& According to .30$ this new scenario has the

following advantages4

Postponement of investments in e5pansion oftransmission and distribution systems&

,eduction in charging networ6s&

7inimi'ation of losses&

8ower capital investment costs&

+he generation may be located close to the load$which can greatly reduce transmission costs&

Due to these benefits$ several countries created policydrivers encouraging the use of DG$ including %ra'il$ in whichhas been in place since 39/3 when the National ElectricEnergy Agency "ANEE8# allowed the use of DG in EDS ./0&

Despite these many advantages$ the insertion of the DG inEDS can result in various problems such as .:04

*ncreased short circuit level&

Power flow reversal&

,e;uirements of new protection techni;ues&

Problems related to stability and reliability&

0&According to .?0$ adaptive protection "AP# can be defined as a

protection philosophy which permits and see6s to ma6ead(ustments to various protection functions in order to ma6ethem more attuned to prevailing power system conditions&

*n this paper$ an AP method to solve the impact of DG

insertion on overcurrent distribution networ6s protection isproposed& +he method considers that the status of each DG ina distribution system is associated with the status of its circuit

brea6er$updating new setting values in the overcurrent relays&+he method was applied to the *EEE /: node system .@0 andimplemented in the ,eal +ime Digital Simulator ",+DS# .0&

**& P,-P-SED7E+2-D

From the literature$ several researchers have been focusingin adaptive protection$ which aims to modify relay settings inreal time in order to adapt the protection system to anychanges in the electrical system ./901./30& *n this conte5t andta6ing as premises the simplicity of implementation andapplicability in real relays$ i&e&$ non1intervention in the internalrelay code$ the developed algorithm is presented in Fig& /&

+he authors of this paper than6 the National !ouncil for Scientific and +echnological Development "!NP;# for allowing this wor6&

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+he diagram shows a generic distribution systemcontaining some DG units which communicate with an APsystem$ called central control$ represented by a central

processing unit& +he AP system will only consider the relaysconnected to the branches with DG&

Figure /& Flow chart of the proposed algorithm&

%riefly$ the algorithm receives periodically informationabout the status of circuit brea6ers responsible for isolating$ incase of any disturbance$ the branches containing the DG onthe system& +hen$ the algorithm monitors these states$repeating this procedure until there is a change in the state ofany brea6er& *f a change occurs$ the algorithm interprets as aconnection or disconnection of DG& *n this situation$ thealgorithm recalculates the new setting group based on the stateof combination of the circuit brea6ers and sends it to the relay&

Setting groups correspond to various pic6up configurationsthat e5ist internally in digital relays ./:0& *n this wor6$ thesegroups are associated with the possible operation scenarios inthe system$ which depends on the amount of DG in operation&

+he setting groups are configured offline$ which allows theuser to select one of these settings as relay operation pic6up&+he calculation was performed according to "/#4

SG= iN = 1DG.

(1)

+herefore$ the setting group "SG# regarding certainoperating scenario is the arithmetic sum of the circuit brea6ersstatus "BDG# associated with DG system& *f the system is in thescenario in which all DG units are turned off$ then SGj$ willhave the value of i+1$ which means that the position setting inthe relay group will correspond to the ma5imum slot number

plus a generator unit& +his relationship is simple and it doesnot re;uire high computational effort$ providing ;uic6

processing and real time applicability& *n summary$ the centralcontrol proceed as follows4

Step /4 ,eceives regularly information about thecircuit brea6ers status&

Step 34 *s there a change in circuit brea6ers statusB

Step :4 *f so$ recalculate the group setting based on"/#&

Step =4 Send the setting group concerning the newoperation scenario for the relays associated with the

branches with DG&

Generally$ this procedure wor6s$ e5cept in islandingsituations& As a result$ the algorithm imposes the condition inwhich "/# is satisfied only when the system is not islanded&

***& ,ES8+S

+o evaluate the proposed method$ the *EEE /: nodessystem "Fig& 3#$ available for EPS analysis$ was used .@0&Despite being relatively small$ this system has very peculiarcharacteristics4 short and relatively highly loaded feeder$ lineswith variety of phasing$ unbalanced loads&

*n this wor6$ two DG were included on the nodes >:: and>?C$ whose data are provided in +able **& +he DG are

connected with the EDS through transformers with relation/4/$ for the purpose of isolation between DG and the system&

Figure 3& 7odified *EEE /: node system&

+his test system was implemented on ,+DS$ a simulatororiginally developed for the study of electromagnetictransients$ which is able to perform simulations in powersystems with operation in real time .0&

Following the re;uirements of Normative ,esolution=@339/3 of ANEE8 ./0$ the protection system has beenadapted to receive all DG$ which was achieved by installingdirectional overcurrent relays controlled by the AP in thesections containing DG$ in the early sections >C9$ >:31>:= and>?/1>?C& +he associated relays were named >C9$ >:: and >?C$respectively&

+he possible operating scenarios are described in +able *&

Noting that the values of overcurrent relays ad(ustments forthe respective sets were performed offline using conventionaltechni;ues ./C0&

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+A%8E *& -PE,A+*-NS!ENA,*-S-FADAP+*

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0 20 40 60 80 100 120 140 160 180 2000

0.5

1State Breaker 650 without AP

Breaker 650

0 20 40 60 80 100 120 140 160 180 2000

0.5


BreakerState

Breaker 633

0 20 40 60 80 100 120 140 160 180 2000

0.5


Time (ms)

Breaker 675

Figure C& !ase / withoutadaptive protection4 setting group of relays and

circuit brea6ers state&

0 20 40 60 80 100 120 140 160 180 2001

1.5

2Relay Setting Group

SG

Relay Setting Group

0 20 40 60 80 100 120 140 160 180 2000

1

2State Breaker 650

Breaker 650

0 20 40 60 80 100 120 140 160 180 2000

1

2State Breaker 633

Breake

rState

Breaker 633

0 20 40 60 80 100 120 140 160 180 2000

0.5

1State Breaker 675

Time (ms)

Breaker 675

Figure >& !ase / withadaptive protection4 setting group of relays and


For !ase 3$ it was considered a scenario in which only theDG >?C is connected to the EDS and operating normally$when at a given time$ there is a three1phase fault at node >?C"Fig& ? to /9#& As shown$ the system withoutAP4

At the fault inception time "=/&3C ms#$ the relay >?C

immediately identifies the event and then sends a tripsignal to the brea6er that isolates the affected area">?&3C ms#&

Since the protection setting is fi5ed andpredetermined$ the relay >C9 is sensitive to the pic6uptoo for this scenario& So that the relay operatesincorrectly at t C&C ms "Figure #$ triggering the

brea6er when there is no disturbance&

As can be seen$ the system withAP4

At the fault inception time "CC&> ms#$ the relay >?Cimmediately identifies the event and then sends a tripsignal to the brea6er that isolates the affected area">@&=C ms#&

*nstead of what occurs in the non1adaptive protectionsystem$ the relay >C9 changes its setting group alreadyconfigured for scenario :$ avoiding the false trip&

0 20 40 60 80 100 120 140 160 180 200-4

-2

0

2

4Currents in the System Input without AP

Time (ms)

Current(kA)

Input current in phase a

Input current in phase b

Input current in phase c

0 20 40 60 80 100 120 140 160 180 200-4

-2

0

2

4Currents in the Branch 671-675 without AP

Time (ms)

Current(kA)

I675aI675b

I675c

Figure ?& !ase 3 withoutadaptive protection4 currents&

0 20 40 60 80 100 120 140 160 180 200-4

-2

0

2

4Currents in the System Input

Time (ms)

Current(kA)




0 20 40 60 80 100 120 140 160 180 200-4

-2

0

2

4Currents in the Branch 671-675

Time (ms)

Current(kA)

I675a

I675b

I675c

Figure @& !ase 3 withadaptive protection4 currents&

0 20 40 60 80 100 120 140 160 180 2000

0.2

0.4

0.6

0.8


BreakerState

Breaker 650

0 20 40 60 80 100 120 140 160 180 2000

0.5


Time (ms)

BreakerState

Breaker 675

Figure & !ase 3 withoutadaptive protection4 setting group of relays andcircuit brea6ers state&

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0 20 40 60 80 100 120 140 160 180 2000

2


SG

Relay Setting Group

0 20 40 60 80 100 120 140 160 180 2000

1

2State Breaker 650

BreakerState

Breaker 650

0 20 40 60 80 100 120 140 160 180 2000

0.5

1 State Breaker 675

Time (ms)

BreakerState

Breaker 675

Figure /9& !ase 3 withadaptive protection4 setting group of relays and

brea6ers state&

*n case :$ it was considered a scenario in which all DG areconnected to the system and operating normally$ when at agiven time a %G fault occurs on node >:: "Figures // to /=#&As viewed$ the system withoutAP4

At the fault inception time "CC&=C ms#$ the relay >::immediately identifies the event and then sends a trip

signal to the brea6er that isolates the affected area"?>&CC ms#&

+he only trip signal was sent from the relay >::&

+he current in the branch involved with the faulte5tinguished indicating that protection has operatedcorrectly&

0 20 40 60 80 100 120 140 160 180 200-1

-0.5

0

0.5

1

1.5Currents in the System Input without AP

Time (ms)

Current(kA)




0 20 40 60 80 100 120 140 160 180 200-1

-0.5

0

0.5

1

1.5Currents in the Branch 632-634 without AP

Time (ms)

Current(kA)

I633a

I633b

I633c

0 20 40 60 80 100 120 140 160 180 200-1

-0.5

0

0.5

1

1.5Currents in the Branch 671-675 without AP

Time (ms)

Current(kA)

I675a

I675b

I675c

Figure //& !ase : withoutadaptive protection4 currents&

Similar results were obtained for the system with AP& Dueto the fact of the system is heavily loaded and considering thatthe inclusion of synchronous machines substantiallyaggravates this situation$ the occurrence of single1phase faultsdoes not modify significantly the current values&

From the obtained results$ one can conclude that in most ofthese cases$ the proposed method was better than theconventional method$ since the latter failed to satisfy the basicre;uirements of a protection system ./C0& 7oreover$ as thecalculation of the pic6up currents for each scenario was madeoffline from short1circuit studies in various scenarios$ it can beinferred that the proposed method will wor6 satisfactorily forgreater number of cases& Another important fact observedregards to the speed of action$ which is due to the simplicity ofthe calculation of the setting group& *t is important to informeither the ,+DS simulation did not consider the delay inchanging the setting group$ which according to somemanufacturers can be up to C seconds ./>0&

A very interesting feature of this method is that the PA is

e5ternal to relays$ with no need for drastic changes in theconventional protection system& -f course$ it is necessary forthe protection system responsible for branches with DG to usedigital relays& +his is a differential of the proposed methodcompared to other methods available in literature$ which needto implement a new type of relay that processed the proposedmethod .=0 1 .C0&

0 20 40 60 80 100 120 140 160 180 200-1

-0.5

0

0.5

1

1.5Currents in the System Input

Time (ms)

Current(kA)




0 20 40 60 80 100 120 140 160 180 200-1

-0.5

0

0.5

1

1.5

2Currents in the Branch 632-634

Time (ms)

Current(kA)

I633a

I633b

I633c

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0 20 40 60 80 100 120 140 160 180 200-1

-0.5

0

0.5

1

1.5Currents in the Branch 671-675

Time (ms)

Current(kA)

I675a

I675b

I675c

Figure /3& !ase : withadaptive protection4 currents&

0 20 40 60 80 100 120 140 160 180 2000

1


Breaker 650

0 20 40 60 80 100 120 140 160 180 2000

0.5


BreakerState

Breaker 633

0 20 40 60 80 100 120 140 160 180 2000

1


Time (ms)

Breaker 675

Figure /:& !ase : withoutadaptive protection4 setting group of relays and


0 20 40 60 80 100 120 140 160 180 2001

1.5


SG

Relay Setting Group

0 20 40 60 80 100 120 140 160 180 2000

1

2State Breaker 650

Breaker 650

0 20 40 60 80 100 120 140 160 180 2000

1

2State Breaker 633

BreakerState

Breaker 633

0 20 40 60 80 100 120 140 160 180 2000

0.5

1State Breaker 675

Time (ms)

Breaker 675

Figure /=& !ase : withadaptive protection4 setting group of relays and


*$ 39//&.>0 A& 2& 7& Soares and J& !& 7& 1

/=C@$ -ctober /@@&./30 A&L& Jampala$ S&S&

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