Iec 62689 2 2016

13 4.7 Summary of FPI/DSU req irements with resp ct to fault detection ac ordin to network o eration mode an fault typ.. By local zation of the fault is me nt the fault p sition with res

Part 2: System aspects

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Part 2: System aspects

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INT ERNAT IONAL

ELECT ROT ECHNICAL

COMMIS ION

ELECT ROT ECHNIQUE

INT ERNAT IONALE

®

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FOREWORD 5

INTRODUCTION 7

1 Sco e 9

2 Normative referen es 9

3 Terms, definition , a breviation an s mb ls 9

3.1 Terms an definition related to neutral p int tre tment 10 3 2 Ab reviation an s mb ls 1

0 4 Choice of FPI/DSU req irements related to fault detection ac ordin to network o eration mode an fault typ 10 4.1 General 10 4.2 F Is/DSUs for isolated neutral s stem 10 4.2.1 Earth fault detection 10 4.2.2 Polyphase fault detection 1

4.3 F Is/DSUs for resonant e rthed (neutral) s stem – arc-s p res ion-coi -e rth (neutral) s stem 1

4.3.1 Earth fault detection 1

4.3.2 Polyphase fault detection 12 4.4 F Is/DSUs for sol dly e rthed neutral s stems (s stems with low-imp dan e e rthed neutrals) 12 4.5 F Is/DSUs for imp dan e e rthed neutral s stem (resistive imp dan e e rthed neutral s stem ) 12 4.5.1 Earth fault detection 12 4.5.2 Polyphase fault detection 1

3 4.6 F Is/DSUs for s stems with hig presen e of DER 13 4.7 Summary of FPI/DSU req irements with resp ct to fault detection ac ordin to network o eration mode an fault typ 13 5 Fault detectin prin iples ac ordin to network an fault typ 15 5.1 General 15 5.2 Earth fault detection an neutral tre tment 18 5.2.1 General 18 5.2.2 Earth fault detection in isolated neutral s stems 18 5.2.3 Earth fault detection in resonant e rthed s stems 2

5.2.4 Overc r ent detection in a sen e or negl gible presen e of DER 3

5.2.5 Overc r ent detection in presen e of a large amou t of DER (sig ificantly in re sin s ort circ it c r ent values) 3

An ex A (informative) Example of a p s ible solution for fault detection throu h FPIs/DSUs on closed lo p fe der 3

A.1 General 3

A.2 Double bip le model 3

A.3 Analy is of zero-seq en e values in case of fault on a l ne out of the closed lo p 4

A.4 Analy is in case of fault on the closed-lo p 4

A.5 Example of on- ield a pl cation 4

An ex B (informative) Example of fault detection co rdination tec niq e amon FPIs/DSUs an MV fe der protection relay 4

B.2 Fault detection confirmation from F Is/DSUs throu h voltage

presen e/a sen e detection 4

Biblogra h 4

Fig re 1 – General arc itecture of an FPI 8

Fig re 2 – General thre -phase diagram of an e rth fault in isolated neutral s stem 16

Fig re 3 – General thre -phase diagram of an e rth fault sol dly e rthed s stem

(example 2) 17

Fig re 4 – Isolated neutral s stem – detection of e rth fault c r ent direction from

FPI/DSU upstre m from the fault location ( ault down tre m from the FPI’s/DSU’s

location) 18

Fig re 5 – Isolated neutral s stem – detection of e rth fault c r ent direction from

FPI/DSU down tre m from the fault location ( ault upstre m from the FPI’s/DSU’s

location) 19

Fig re 6 – Isolated neutral s stem – vector diagrams related to Fig re 4 an Fig re 5 2

Fig re 7 – Relation hip b twe n FPI/DSU reg lated c r ent thres old an e rth fault

c r ent in case of non-directional e rth fault c r ent detection Fault down tre m from

FPI/DSU A4-2 21

Fig re 8 – Relation hip b twe n FPI/DSU reg lated c r ent thres old an e rth fault

c r ent in case of non-directional e rth fault c r ent detection Fault down tre m from

FPI/DSU A4-1 an upstre m from FPI/DSU A4-2 2

Fig re 9 – Relation hip b twe n FPI/DSU reg lated c r ent thres old an e rth fault

c r ent in case of non-directional e rth fault c r ent detection Fault on MV bu b r

(upstre m from an F I/DSU) 2

Fig re 10 – Pure resonant e rthed s stem – detection of e rth fault c r ent direction

from FPI/DSU upstre m from the fault location ( ault down tre m from the FPI’s/DSU’s

location) 2

Fig re 1 – Pure resonant e rthed s stem – detection of e rth fault c r ent direction

from FPI/DSU down tre m from the fault location ( ault upstre m from the FPI’s/DSU’s

location) 2

Fig re 12 – Pure resonant e rthed s stem – vector diagrams related to Fig re 10 an

Fig re 1 2

Fig re 13 – Resonant e rthed s stem with in u tan e an p rmanent p ralel resistor

– detection of phase to e rth fault c r ent direction from FPI/DSU upstre m from the

fault location ( ault down tre m from the FPI’s/DSU’s location) 2

Fig re 14 – Resonant e rthed s stem with in u tan e with p ral el resistor s stem –

detection of phase to e rth fault c r ent direction from FPI/DSU down tre m from the

fault location ( ault upstre m from the FPI’s/DSU’s location) 2

Fig re 15 – Resonant e rthed s stem with in u tan e with p ral el resistor s stem –

vector diagrams related to Fig re 13 an Fig re 14 3

Fig re 16 – Earthin resistor s stem – detection of phase to e rth fault c r ent

direction from FPI/DSU upstre m from the fault location ( ault down tre m from the

FPI’s/DSU’s location) 3

Fig re 17 – Earthin resistor s stem – detection of phase to e rth fault c r ent

direction from FPI/DSU down tre m from the fault location ( ault upstre m from the

Fig re 2 – Overc r ents in a radial network with negl gible DER presen e – cor ect

c r ent detection by non-directional FPI/DSU (go d sen itivity con ernin overc r ent

detection) 3

Fig re 21 – Overc r ents in a radial network with a large amou t of DER – u rel a le fault detection by non-directional FPIs/DSUs (in or ect detection or extremely low sen itivity) 3

Fig re A.1 – Double bip le 3

Fig re A.2 – Cas ade of double bip les 41

Fig re A.3 – Closed lo p double bip les 4

Fig re A.4 – Eq ivalent model in case of fault 4

Fig re B.1 – Cor ectly co rdinated fault selection amon FPIs/DSUs an protection relay 4

Fig re B.2 – In or ectly co rdinated selection amon FPIs/DSUs an protection relay Case 1 4

Fig re B.3 – In or ectly co rdinated fault selection amon FPIs/DSUs an protection relay Case 2 4

Ta le 1 – Summary of FPI/DSU req irements refer ed to fault detection ac ordin to

network o eration mode an fault typ 14

INTERNATIONAL ELECTROTECHNICAL COMMISSION

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p te t rig ts IEC s al n t b h ld re p n ible for id ntifyin a y or al s c p te t rig ts

International Stan ard IEC 6 6 9-2 has b en pre ared by IEC tec nical commit e 3 :

In trument tran formers

The text of this stan ard is b sed on the fol owin doc ments:

Ful information on the votin for the a proval of this stan ard can b foun in the re ort on

votin in icated in the a ove ta le

A l st of al the p rts in the IEC 6 6 9 series, u der the general title Curre t and v lag

se sors orde te cto rs, to be used forfault pa s ge indic ato purp o se s, can b fou d on the

IEC we site

The commit e has decided that the contents of this publ cation wi remain u c an ed u ti

the sta i ty date in icated on the IEC we site u der "ht p:/we store.iec.c " in the data

related to the sp cific publ cation At this date, the publ cation wi b

th t it c ntains c lours whic are c nsidere to be us ful for the c r e t

und rsta ding of its c nte ts Us rs s ould therefore print this doc me t using a

c lo r printer

The IEC 6 6 9 series is a prod ct fami y stan ard for c r ent and voltage sen ors or

detectors, to b u ed for fault p s age in ication purp ses by pro er devices or fu ction ,

in icated as fault p s age in icator (FPI) or distribution s bstation u it (DSU), de en in on

their p rforman es

Dif erent names are u ed to in icate FPIs de en in on the region of the world an on their

fu ctional ties con ernin ca a i ty to detect dif erent kin s of faults, for in tan e:

• fault detector;

• smart sen or;

• faulted circ it in icator (FCI);

• s ort circ it in icator (SCI);

• e rth fault in icator (EFI);

• test p int mou ted FCI

• combination of the a ove

Simpler version , only u in local information/sig als an /or local commu ication, are cal ed

FPI whi e very evolved version are cal ed DSU The lat er are expl citly desig ed for smart

grid an b sed on IEC 6 8 0-5 an IEC 618 0 commu ication protocols.Comp red to

in trument tran formers, digital commu ication tec nolog is s bject to on-goin c an es

whic are exp cted to contin e in the future

Profou d exp rien e with de p integration b twe n electronic an in trument tran formers

has yet to be gathered on a bro der b sis, as this typ of eq ipment is not yet widespre d in

the in u try

DSUs, b sides FPI b sic fu ction , may also o tional y integrate ad itional au i ary fu ction

• voltage presen e/a sen e detection for medium voltage (MV) network automation, with

an without distributed energ resources presen e (not for fault confirmation, whic can

b a b sic FPI fu ction de en in on the ado ted fault detection method, neither for

safety-related asp cts, whic are covered by IEC 612 3-5);

a pl cation , s c as MV network automation, monitorin of p wer flows, etc

• smart grid management (s c as voltage control an u wanted islan o eration) by

me n of a pro er interface with local distributed generators (DER);

• local output of colected information by me n of s ita le interfaces;

• remote tran mis ion of col ected information;

• others

A general FPI s heme is outlned in Fig re 1

A Cure t (a d, if n c s ary, v lta e) s n ors 1 or 3 p a e ma b mo itore

B Tra smis io of sig als b twe n s n ors a d ele tro ic

C: L c l in ic tio s (lamp , LEDs,fla s, etc.)

D An lo u , digital a d/or c mmu ic tio in uts/o tp ts for remote c mmu ic tio /c mma d (h rd wire a d/or

wirele s)

E Co n ctio s to field a p ratu

F Sig al c n itio in , pro e sin a d in ic tin u it (CPIU)

G Power s p ly

Cur e t s n ors) ma d te t fa lt c re t p s a e with ut a y n e of g lv nic c n e tio to th p a e(s) (for

in ta c in c s of c ble ty e c r e t s n ors or of ma n tic field s n or)

Not al th a o e lste p rts or fu ctio s are n c s ariy in lu e in th F I d p n in o its c mple ity a d o

its te h olo y Howe er, at le st 1 o e of C or D fu ctio s s al b pre e t

Figure 1 – Ge eral arc ite ture of a F I

0.2 Position of this sta dard in relation to the IEC 618 0 s rie

The IEC 618 0 series is inten ed to b u ed for commu ication an s stems to s p ort

p wer uti ty automation

The IEC 6 6 9 series wi also introd ce a dedicated namesp ce to s p ort integration of

FPIs/DSUs into p wer uti ty automation

In ad ition, it defines pro er data models an diferent profi es of commu ication interfaces to

s p ort the dif erent u e cases of these FPIs/DSUs

Some of these u e cases rely on the con e t of exten ed s bstation, whic is inten ed as the

commu ication amon intel gent electronic devices (IED) throu h IEC 618 0 located b th

alon MV fe ders an in the main s bstation, for the most so histicated FPI version (an

therefore DSUs) ( or smart grid a plcation , for in tan e) Su h a profi e may not b l mited

to FPI/DSU devices, but may embrace fe tures ne ded to s p ort exten ion of these

CURRENT AND VOLTAGE SENSORS OR DETECTORS,

Part 2: System aspects

This p rt of IEC 6 6 9 des rib s electric phenomena an electric s stem b haviour d rin

faults, ac ordin to the most widely dif u ed distribution s stem arc itecture an to fault

typ logies, to define the fu ctional req irements for fault p s age in icators (FPI) an

distribution s bstation u its (DSU) (in lu in their c r ent an /or voltage sen ors), whic are,

resp ctively, a device or a device/combination of devices an /or of fun tion a le to detect

faults an provide in ication a out their local zation

By local zation of the fault is me nt the fault p sition with resp ct to the FPI/DSU in tal ation

p int on the network (upstre m or down tre m from the FPI/DSU’s location) or the direction of

the fault c r ent flowin throu h the FPI itself The fault local zation may b o tained

• directly from the FPI/DSU, or

• from a central s stem u in information from more FPIs or DSUs,

con iderin the fe tures an the o eratin con ition of the electric s stem where the

FPIs/DSUs are in tal ed

This p rt of IEC 6 6 9 is therefore aimed at helpin u ers in the a pro riate c oice of

FPIs/DSUs (or of a s stem b sed on FPI/DSU information) pro erly o eratin in their

network , con iderin ado ted solution an o eration rules (defined by tradition an /or

de en in on p s ible con traints con ernin contin ity an q al ty of voltage s p ly defined

by a national reg lator), an also takin into ac ou t complexity of the a p ratu an

con eq ent cost

This p rt of IEC 6 6 9 is mainly foc sed on s stem b haviour d rin faults, whic is the

“core” of FPI/DSU fault detection ca a i ty clas es des rib d in IEC 6 6 9-1, where al

req irements are sp cified in detai

The fol owin doc ments, in whole or in p rt, are normatively referen ed in this doc ment an

are in isp n a le for its a pl cation For dated referen es, only the edition cited a ples For

u dated referen es, the latest edition of the referen ed doc ment (in lu in an

amen ments) a pl es

IEC 6 6 9-1, Cu rre t and v lage senso rs o r de te cto rs, to be used for fau lt p as ag

indic ato n p urpo se s – Part 1: Ge ne ral p rinciple s and re qu ire me ts

3 Terms, definitions, abbreviations and symbols

For the purp ses of this doc ment, the terms an definition given in IEC 6 6 9-1 an the

3.1 Terms a d definitio s relate to ne tral point tre tme t

3.1.1

arc-s p re sion c i

sin le-phase neutral e rthin re ctor inten ed for comp n atin the ca acitive l ne- o-e rth

c r ent d e to a sin le-phase e rth fault

Note 1 to e try: In te d of a p re re ctor, with hig q alty fa tor Q, a re istiv -re ctiv imp d n e ma b u e

to re d r e sier th e rth fa lt d te tio a d/or cle ra c

Note 2 to e try: An arc-s p re sio c i is als k own a a Peters n c i in c rtain are s

[SOURCE: IEC 6 0 0-4 1:19 0, 4 1-01-0 , modified – Note 1 an Note 2 to entry have b en

ad ed

3.2 Abbre iations a d s mbols

For the purp ses of this doc ment, the a breviation an s mb ls given in IEC 6 6 9-1

a ply

4 Choice of FPI/DSU requirements related to fa lt detection according to

network operation mode a d fault type

Clau e 4 is mainly foc sed on radial y o erated distribution network , b cau e this is,

general y, the most widely ado ted mode of o eration

Fault (or fault c r ent p s age) detection on s c network stron ly rel es on MV neutral p int

mode of o eration

In case of closed lo p distribution network , diferent con ideration are neces ary

Directional fault detection, b th con ernin e rth faults an overc r ents, b sed on vector

relation hips amon voltages an c r ents, is influen ed by the imp dan e of the fe der an

have to b evaluated case by case Commu ication amon F Is may b req ired

A simpler solution may con ist in o enin the closed lo p returnin to radial o eration an /or

to ado t commu ication amon FPIs

An example of a p s ible solution is s own in An ex A

4.2 FPIs/DSUs for is late n utral s stem

4.2.1 Earth fa lt dete tion

The e rth fault c r ent is influen ed b th by the network config ration an typ log an by

the fault resistan e

The ca acitive e rth fault c r ent contribution of medium voltage fe ders' he lth section is

general y an a precia le p rcentage of total e rth fault c r ent

NOT Th c ntrib tio to e rth fa lt c r e t of a u d rgro n me ium v lta e c ble is a o t 5 time th t of a

o erh a fe d r of th s me le gth

Hen e, in case of a fault upstre m from the location of a FPI/DSU not eq ip ed with

directional detection of fault c r ent p s age, to avoid in or ect in ication regardin the fault

location, the c r ent thres old set on F I/DSU s ould b hig er than the maximum e rth fault

L w sen itivity with regard to fault resistan e could, therefore, b o tained in case of

non-directional FPIs/DSUs

One method to dis riminate the fault c r ent with relatively hig sen itivity with regard to

fault resistan e could b the ado tion of F Is/DSUs b sed on directional e rth fault detection

If the contribution to ca acitive e rth fault c r ent from the network down tre m from the

FPI’s/DSU’s location is negl gible, non-directional e rth fault detection may b con idered

without any sig ificant decre se of FPI/DSU p rforman e

Pos ible presen e of DER has no ef ect on the direction of fault c r ent

If no DER (or not a precia le amou t of DER) is present, in case of p lyphase faults, the fault

c r ent is comin from the HV/MV tran former Directional FPIs/DSUs s ould, general y, b

req ired if DER contribution to p lyphase fault c r ent is a precia ly present or in case of

closed-lo p config ration

4.3 FPIs/DSUs for re o a t e rthe (ne tral) s stem – arc-s ppre sion-c i -e rth

(ne tral) s stem

4.3.1 Earth fa lt dete tion

The fault c r ent is influen ed by the network config ration, the coi desig (pure in u tive or

in u tive-resistan e or in u tive with s ort term resistan e, etc.), the con ection to MV

neutral p int, the tu in of the resonant coi , the network los es at zero seq en e an the

fault resistan e

Two main solution are p s ible: a “pure” arc-s p res ion coi, a fixed or tu a le in u tor

with neglgible resistive comp nent d e only to internal los es or an in u tan e with an

intentional resistor to in re se the amou t of resistive c r ent d e to the coi

4.3.1.2 “Pure” arc-s ppre sio c i

In case of “pure” arc-s p res ion coi , tu ed ne rly to 10 % of network ca acitve c r ent an

stan ard los es value in the network comp nents, the e rth fault c r ent is extremely low,

mainly resistive, as the ca acitive e rth fault c r ent contribution from the MV network is

comp n ated by the in u tive contribution from the arc s p res ion coi The mag itu e of

the e rth fault c r ent would have ne r zero value when an e rth fault oc urs at an location

on the same HV/MV s bstation bu b r network

More ver, e rth fault c r ent throu h al FPIs/DSUs, whatever their location on the network

(upstre m or down tre m from the fault p sition), is mainly re ctive (vector relation hip

b twe n resid al c r ent in an FPI/DSU an resid al voltage is the same, cor esp n in to

9 ° degre le din an le of resid al c r ent with resp ct to resid al voltage), with neglgible

active comp nent ( his comp nent is the only one a le to modify vector relation hips b twe n

FPIs/DSUs for pure resonant e rthed (neutral) s stems s ould, therefore, b directional for

phase to e rth fault detection

NOT With ut th a o tio of a re istiv -in u tiv arc-s p re sio c i (4.3.1.3), it ma b p s ible to d te t a

e rth fa lt with n n-dire tio al F I/DSU a d with temp rary mo ific tio of th n twork c nfig ratio , b , for

in ta c , cre tin a mistu in of th arc-s p re sio c i u in a c p citor in p ralel to th c i its lf a d

switc in it o a d of with difere t mo altie

4.3.1.3 Re istiv -in uctiv arc-s ppre sion c i

If a hig -value resistor is in tal ed in p ral el to the arc s p res ion coi , temp rari y or

p rmanently con ected to e rth:

• e rth fault c r ent throu h FPI/DSU in tal ed on he lth fe ders or down tre m from the

fault is mainly re ctive ( he vector relation hip b twe n resid al c r ent an resid al

voltage ne rly cor esp n s to 9 ° le din an le of resid al c r ent with resp ct to resid al

voltage), with negl gible active comp nent;

• e rth fault c r ent throu h FPI/DSU in tal ed on faulty fe ders upstre m from the fault is

resistive-re ctive ( he vector relation hip b twe n resid al c r ent an resid al voltage is

u ual y in the ran e from 9 ° to 18 ° le din an le of resid al c r ent with resp ct to

resid al voltage), with non-negl gible active comp nent

The mag itu e of the e rth fault c r ent would have a value ne rly cor esp n in to the

active c r ent from the e rthin resistor when an e rth fault oc urs at an location on the

same s bstation bu b r network

FPIs/DSUs for resistive-in u tive resonant e rthed (neutral) s stems s ould, therefore, have

either directional or non-directional ca a i ty for phase to e rth fault detection

Pos ible presen e of DER has no ef ect on the direction of fault c r ent

NOT Dete tio of intermite t e rth fa lts b F I/DSU mig t b re uire

4.3.2 Polypha e fa lt d te tion

Se 4.2.2

4.4 FPIs/DSUs for s l dly e rth d ne tral s stems (s stems with low-impe a c

e rth d ne trals)

Overc r ent detection can b u ed to detect b th e rth an p lyphase faults

If no DER (or no a precia le amou t of DER) is present, the fault c r ent comes from the

HV/MV tran former Phase directional FPIs/DSUs may b req ired only if DER is a precia ly

present

More ver, e rth directional FPIs/DSUs may b req ired even if, ac ordin to the DER neutral

p int an the DER tran former group, a phase to e rth c r ent contribution may have come

FPIs/DSUs could b directional an /or non-directional, de en in on the values of the

intentional e rthin resistor ( he lower it is, the hig er is the neutral c r ent, th s directional

detection could b avoided in some circ mstan es), on the network config ration, on the

network ca acitive c r ent an on the desired sen itivity con ernin fault resistan e value

detection

In the case of an e rthin resistor injectin low or moderate neutral c r ents in the event of an

e rth fault, F Is/DSUs s ould prefera ly b directional for e rth fault detection This is to

o tain a pro riate sen itivity with regard to faults with hig resistan e value The res ltin

e rth fault c r ent o tained with this solution is not mu h hig er than the pure ca acitive e rth

fault c r ent comp nent

In the case of an e rthin resistor injectin moderate or hig neutral c r ent in the event of an

e rth fault, non-directional FPIs/DSUs may b u ed With this solution, the e rth fault c r ent

is hig er than the network ca acitive c r ent

4.5.2 Polyph s fa lt dete tion

Se 4.2.2

4.6 FPIs/DSUs for s stems with high pre e c of DER

The presen e of DER on a network is con idered to b hig when the c r ent contribution

from DER down tre m from the FPI’s/DSU’s location for a fault located upstre m from the

FPI/DSU itself (even on another MV fe der con ected to the same HV/MV or MV/MV

tran former) is comp ra le to the FPI/DSU overc r ent thres old

In this case, FPIs/DSUs s al have directional detection of phase faults if the DER

sig ificantly contributes to s ort circ it c r ents (se 5.2.4 an 5.2.5) Con ernin phase to

e rth fault detection, se 4.2.1, 4.3.1, 4.4, 4.5.1 In an case, if directional detection is

present for p lyphase overc r ents, the same s ould b true for phase to e rth c r ents

NOT This v rsio of F I/DSU c n als b a le to:

• ma a e ma y smart grid n twork c nfig ratio s, a s min th t smart grid are distrib tio n twork with a

hig p n tratio of DERs;

• ofer a ditio al fe ture (for in ta c , a v n e n twork a tomatio , in lu in s lf h aln a d a tomatic

s p ly re tore) e e in th pre e c of DER;

• s p ort e s n twork re o fig ratio , DER a tiv p wer a d re ctiv p wer c ntrol for v lta e re ulatio , etc

Ev n a ditio al distrib tio n twork o eratio stru ture , difere t from th main difu e ra ial o e , ma b

s c e sfuly h n le b th s F Is/DSUs (for in ta c clo e lo p o eratio of MV fe d rs)

4.7 Summary of FPI/DSU re uireme ts with re pe t to fa lt dete tion a c rding to

network operatio mo e a d fa lt type

Ta le 1 gives a s mmary of FPI/DSU req irements des rib d in 4.1 to 4.6

Ta le 1 refers only to whether it is p s ible or not to ado t the directional fault detection

prin iple on FPIs, i.e the detection of the fault c r ent throu h the FPI itself

The direction may b o tained with dif erent solution : by me s rin the an le b twe n

resid al/phase voltage an resid al/phase c r ent, by tran ient analy is of c r ent (an /or

voltage) of the first mi isecon af er fault oc ur en e, etc

The complete FPI (an DSU) clas ification by clas es is in lu ed in IEC 6 6 9-1

Table 1 – Summary of FPI/DSU re uireme ts refer e to fa lt dete tion

a c rdin to network operation mode a d fa lt type

Fault type MV network neutal p int o eratio mo e

Fault detection has to cor ectly o erate in e en ent of network neutral p int tre tment an

when there is the p s iblty of a hig degree of p netration of distributed generation (DER)

con ected to distribution fe ders If not, this has to b cle rly stated by the man facturer in

the “a pl cation field”

In order to cor ectly detect faults, FPIs/DSUs s ould b integrated in the network protection

s stem for fault location or, at le st, co rdinated with the protection s stem itself

They s ould have the same fault detection ca a i ty an sen itivity as the network protection

s stem This is to avoid p s ible pro lems in fault location d e to lower FPI/DSU sen itivity

with resp ct to the MV fe der protection relay, ir esp ctive of whether the location is

p rformed by p rson el in field or by an automation s stem These pro lems may b present

if it is neces ary to detect an cle r a hig resistan e value e rth fault

On the other han , in case of hig er FPI/DSU sen itivity with resp ct to MV fe der

protection , n isan e e rth fault detection may ha p n, with negative con eq en es for

p rson el in field or for automation s stems; the lat er may b avoided, for in tan e, throu h

a fault presen e confirmation (e.g voltage or c r ent a sen e determined by MV fe der

protection relay trip in as ociated with simultane u fault detection from the FPI/DSU)

In An ex B, two diferent examples of solution for fault detection an fault location detection

an cle rin are des rib d They have the same efectivenes with regard to faults, but

dif erent p rforman e with regard to n mb r an typ logy of s p ly inter uption to en u ers

Fig res 2 an 3 s ow the fault c r ent p th an the vector diagrams as ociated with diferent

kin s of faults on dif erently o erated network , as it is fu damental for the FPI/DSU

man facturer an u er to take al this into ac ou t for an a pro riate FPI/DSU desig an

c oice

NOT Th v ctor dia rams s own in Fig re 2, Fig re 3 a d in 5.2 are inte d d o ly for th a o e d s rib d

p rp s So th v ctor s ale c n b in ore t b c u e of e itorial c n traints

Co c rnin e rth fa lts, MV s stems ma b gro p d in two main c te orie : s ldly e rth d n utral s stems a d

al th oth rs (is late , c mp n ate , etc) Th s two c te orie h v c mpletely difere t b h vio rs (s e

23

23

3

12

C

ECje

23

23

3

6

C

C

C

C

9

333

3

23

Cj

ECj

C

C

C

9

333

3

23

Cj

ECj

rsd)

in c s of a e rth fa lt in tale o a fa lty MV fe d r For

c mplete d tais a d for oth r MV n utral p int o eratio mo e (e c pt for s ldly e rth d s stems), s e 5.2

B: Toroid l CT for d te tio of re id al c re t I

R

in c s of a e rth fa lt in tale o a h alth MV fe d r Th

b h vio r is simiar for al s stems, e c pt for s ldly e rth d s stems

ECje

23

23

CSA

R A

IIII

Ca a itiv c re t c ntrib tio from h alth a d fa lty MV fe d rs is 1/3 with re p ct to th a o e d s rib d

s stems Th refore, I

C

> I

A, I

B, etc whic ma b c n id re n glgible

Figure 3 – Ge eral thre -pha e dia ram of

5.2 Earth fa lt dete tion a d ne tral tre tme t

Earth faults c r ents are de en ent up n neutral tre tment an fault resistan e

FPIs/DSUs s al b desig ed an tested for e c neutral p int tre tment of MV network

where they are req ired to b in tal ed

5.2.2 Earth fa lt dete tion in is late ne tral s stems

The s heme of c r ent flow direction with referen e to the orientation of resid al c r ent

sen ors is s own in Fig re 4 an Fig re 5

The vector diagrams an s mb l definition are in icated in Fig re 6

Figure 4 – Is late n utral s stem – dete tion of e rth fa lt c r e t dire tion

from FPI/DSU upstre m from the fa lt loc tion

C2+I

C3

= I

C-I

C2+I

C3+I

Figure 5 – Is late n utral s stem – dete tion of e rth fa lt c r e t dire tion

from FPI/DSU downstre m from th fa lt loc tion

( a lt upstre m from the FPI s/DSU’s lo atio )

C2+I

C3+I

C2+I

C3

=I

C-I

C4

A3

A1

c n e te to th s me MV b s ar (E = p a e to e rth v lta e of th ele tric s stem)

Ca e A: Earth fa lt d wn tre m from F I/DSU A1

Ca e B: Earth fa lt d wn tre m from F I/DSU A2

Ca e C: Earth fa lt u stre m from F I/DSU A3

If the FPI/DSU is non-directional, its c r ent thres old set in s al b hig er than the

ca acitive c r ent of the down tre m p rt of the fe der (with resp ct to the FPI’s/DSU’s

location) to avoid an in or ect in ication in case of an upstream e rth fault

This may drastical y red ce its sen itivity; for in tan e, no detection is p s ible if the

down tre m ca acitive c r ent is comp ra le to or hig er than that of the upstre m one (case

of down tre m u dergrou d network)

A s ort des ription is s own in Fig re 7, Fig re 8, an Fig re 9 where, for a b t er

explanation, the seq en e re resentation of the phenomena is ado ted

Ke

lo atio of re id al c re t tra sformers (CTs) (or of c r e t s n ors for me s reme t of re id al c re t

c n e tio al orie tatio of re id al c re t tra sformers (CTs) (or of c r e t s n ors for me s reme t of

C2, I

C3, I

re id al c p citiv c re t of th Fe d r 4 s ctio u stre m from th F I/DSU A4-2 lo atio

a d d wn tre m from th F I/DSU A4-1 lo atio

re id al c r e t me s re b F I/DSU A4-2 re id al c r e t tra sformer (CT) or c re t s n or

in c s of a e rth fa lt d wn tre m from th F I/DSU A4-2 (e u l to I

A4-2A4-

Ir2= IC -IC4Ir

1

= I

C1+I

C2+I

C3

= I

C-I

C4

A 1,A2,A 3Ir

In case of an e rth fault down tre m from the FPI/DSU A4-2 (Fig re 7), its maximum c r ent

thres old to detect the fault, without directional e rth fault c r ent detection, is I

C

− I

C 4_(with

fault resistan e eq al to zero an not con iderin CT/sen or ac uracies) The lower the

reg lated c r ent thres old, the hig er the FPI/DSU sen itivity

Ke

lo atio of re id al c re t tra sformers (CTs) (or of c r e t s n ors for me s reme t of re id al c re t

c n e tio al orie tatio of re id al c re t tra sformers (CTs) (or of c r e t s n ors for me s reme t of

C2,I

C3,I

re id al c p citiv c re t of th Fe d r 4 s ctio u stre m from th F I/DSU A4-2 lo atio

a d d wn tre m from th F I/DSU A4-1 lo atio

I

C4 2

re id al c p citiv c r e t of th Fe d r 4 s ctio d wn tre m from th F I/DSU A4-2 lo atio

A1, A2, A3 F Is/DSUs at th d p rture of fe d r 1, fe d r 2 a d fe d r 3, re p ctiv ly, a d afe te b

I

C1, I

2+I

3

= I-I

4A1, A 2, A3

In case of an e rth fault down tre m from the FPI/DSU A4-1 but upstre m from FPI/DSU A4-2

(Fig re 8), its maximum c r ent thres old, without directional e rth fault c r ent detection, is

I

C

− I

C 4

(with fault resistan e eq al to zero an not con iderin CT/sen or ac uracies) The

lower the reg lated c r ent thres old, the hig er the FPI/DSU sen itivity

Nevertheles , the minimum c r ent thres old of FPI/DSU A4-2 s al b hig er than I

C4 2

in

order to avoid in or ect fault c r ent p s age detection

Ke

lo atio of re id al c re t tra sformers (CTs) (or of c r e t s n ors for me s reme t of re id al c re t

c n e tio al orie tatio of re id al c re t tra sformers (CTs) (or of c re t s n ors for me s reme t of

C2, I

C3, I

re id al c p citiv c re t of th Fe d r 4 s ctio u stre m from th F I/DSU A4-2 lo atio

a d d wn tre m from th F I/DSU A4-1 lo atio

Both in case of an e rth fault down tre m from the F I/DSU A2 or A1, the minimum c r ent

thres old of FPIs/DSUs A1, A2 an A3, without directional e rth fault c r ent detection, are

CT/sen or ac uracies)

Furthermore, in case of an e rth fault on the MV bu b r, c r ent thres old of F I/DSU A4-1

an A4-2 s al b hig er than I

C4

C 4_

, resp ctively

The hig er the reg lated c r ent thres old, the lower the p s ibi ty of an in or ect fault

detection from FPIs/DSUs on he lth fe ders or on the faulty fe der down tre m from the

fault

This me n that, in case of non-directional fault detection from FPIs/DSUs:

• the cor ect fault detection is determined b th from down tre m fe der fe tures an from

upstre m network fe tures;

• FPI/DSU reg lated c r ent thres old s al b hig er than the e rth fault c r ent

contribution from the network down tre m from its location an lower than the e rth fault

c r ent contribution from the whole network upstre m from its location This may red ce

its sen itivity;

• e c FPI/DSU s ould have a dif erent reg lated c r ent thres old, therefore res ltin in

dif erent sen itivities related to the in talation p int;

• c an es in the distribution s stem config ration of the network may c an e the fault

c r ent contribution an res lt in inac urate fault detection

Therefore, directional detection from the FPI/DSU is recommen ed: dif erent algorithms may

b u ed to determine the direction of the fault (varmetric detection prin iple, tran ient analy is

of the first mi isecon af er the fault, etc.)

5.2.3 Earth fa lt dete tion in re on nt e rthe s stems

5.2.3.1 Pure re on nt e rthe (only in ucta c )

The s heme of c r ent flow direction with referen e to the orientation of resid al c r ent

sen ors is s own in Fig re 10 and Fig re 1

C3-I=-I

C2+I

C3+I

C2+I

C3-I=-I

C2+I

C3+I

C4

B

B

B

in u tiv c re t from th c i (I) ∼ z ro v lu (s me p a e, n v ctor s m n c s ary).

L s e (a tiv c re t c mp n nt at z ro s q e c of n twork c mp n nts are n glgible

(E is th p a e to e rth v lta e of th ele tric s stem)

NOT Co sid rin fa lts u stre m or d wn tre m

from th s me F I lo ate o th fa lty fe d r,

als fa lt c re t v lu s a d a gle with re p ct to

re id al v lta e are th s me

IE

C1+ I

C2+ I

C3

− I = −I

C4 (s me dire tio a I)

(s me p a e, n v ctor s m n c s ary) L s e (a tiv c re t c mp n nt at z ro

re id al c r e t me s re from F I/DSU in th lo atio o Fe d r 4 for a e rth fa lt

d wn tre m from th F I/DSU; I

r 2

= I

C1+ I

C2+ I

C3+ I

In the case of a down tre m fault an coi at 10 % of ca acitive c r ent, the c r ent throu h

the FPI/DSU is the vector s m of the ca acitive c r ent of the MV fe der down tre m from

the FPI’s/DSU’s location an of a minimal neutral active c r ent (d e to coi internal los es

an to al the other zero seq en e resistive comp nents in the network, not s own in

Fig re 10 or Fig re 1 an b in u ual y negl gible or, an way, very smal )

For coi s tu ed at values dif erent from 10 % I

C, the c r ent throu h the FPI/DSU is the

vector s m of the ca acitive/in u tive c r ent mismatc (mismatc , intentional or not,

b twe n the in u tive c r ent from the coi an the total MV network ca acitive c r ent an

of the ca acitive c r ent of the MV fe der down tream from the FPI’s/DSU’s location an of

the neutral active c r ent

In b th cases, this c r ent is comp ra le or even lower than the down tre m ca acitive

c r ent an has the same direction as the fault c r ents in the he lth fe ders (an relative

FPIs/DSUs) So, directional detection from the FPI/DSU s ould b present, even if it is

extremely dif ic lt to determine the direction of e rth- ault c r ent with pure neutral imp dan e

when the s stem is tu ed to 10 % of the network total ca acitive c r ent: dif erent algorithms

may b u ed (varmetric, provided the coi internal los es are hig enou h, tran ient analy is,

etc.)

5.2.3.2 Re ona t e rthe thro gh inducta c with paral el re istor (re cta c

e rthe )

The s heme of c r ent flow direction with referen e to the orientation of resid al c r ent

sen ors is s own in Fig re 13 an Fig re 14

Fig re 13 – Re on nt e rthe s stem with in ucta c a d perma e t paral el re istor –

dete tio of pha e to e rth fa lt c r e t dire tion from FPI/DSU upstre m from the fa lt

loc tion ( a lt downstre m from the FPI s/DSU’s loc tion)

C2+I

C3

C4+I

C2+I

C3+I

C4

=-IA1

C2+I

C3

C4+I

C2+I

C3+I

of c i tu e to 10 % I

C, ie

RLCF

III

× C

E) × E – I

C4), c i in u tiv c re t I a d c i + a ditio al re istiv c re t d e to

n twork lo s s at z ro s q e c , ∼ v ctor s m of (−I

C 4), s me dire tio a I, a d I , ie.:

RLCCR

IIIII

CCCCC

(E is th p a eto e rth v lta e of th ele tric s stem)

re id al c r e t me s re from F I/DSU in th lo atio o Fe d r 4 for a e rth fa lt

d wn tre m from th F I/DSU, c r e p n in to v ctor s m of c p citiv c re t

dwn stra m4CCR

III

II

CCC

CC

v ctor dia rams relate to Fig re 13 a d Fig re 14

In case of non-directional fault detection, it is very dif ic lt to determine fault c r ent direction

FPI/DSU sen itivity (minimum thres old) is related to the active comp nent of the c r ent

throu h the (eq ivalent p ral el resistor an to the cap citive c r ent of the fe der section

that is down tre m from the FPI’s/DSU’s location

If the contribution to e rth fault c r ent of the network down tre m from the FPI’s/DSU’s

location is comp ra le to or hig er than that of the network upstre m, only the active

comp nent of the c r ent d e to an (eq ivalent p ral el resistor may al ow cor ect directional

fault detection

The active comp nent of the c r ent al ows for FPI’s/DSU’s c r ent sen itivity to b in re sed

so that faults down tream from the FPI’s/DSU’s location can b detected, th s avoidin

n isan e o eration an providin s f icient sen itivity for hig -resistan e fault detection

Directional detection from the F I/DSU s ould b present Without directional fault detection

fu ction, sen itivity may b very red ced, de en in on the total value of the resistan e

elements in series in the fault circ it

Here again, c an es in the config ration of the network or network config ration in whic a

sin le MV fe der gives a mu h big er contribution (in terms of ca acitive c r ent, with resp ct

To detect the fault c r ent direction , diferent algorithms may b u ed (wat metric detection

prin iple, tran ient analy is of first mi isecon af er the fault, etc.)

In case of a down tre m fault an coi at 10 % of ca acitive c r ent, the c r ent throu h the

FPI/DSU is the vector s m of the ca acitive c r ent of the MV fe der down tream of the

FPI’s/DSU’s location an of the neutral active c r ent

For coi tu ed to values dif erent from 10 % I

C, the c r ent throu h the FPI/DSU is the vector

s m of the ca acitive/in u tive c r ent mismatc (mismatc , intentional or not, b twe n the

in u tive c r ent from the coi an the total MV network ca acitive c r ent , of the ca acitive

c r ent of the MV fe der down tre m from the FPI’s/DSU’s location an of the neutral active

c r ent

For active c r ent, two cases can b examined:

• Permanent p ral el resistor: the neutral active c r ent is relatively low (some amp res or

ten of amp res), res ltin in low total e rth fault c r ent In this case, the c r ent in the

FPI/DSU is comp ra le to or lower than the down tre m ca acitive c r ent an has the

same direction (with referen e to re ctive comp nent as the fault c r ents in the he lthy

fe ders (an relative FPIs/DSUs) As mistu in of the coi is u ual y negl gible, an total

c r ent values very low, directional FPIs/DSUs are req ired;

• Short term p ral el resistor: when the resistor is put in service, the e rth fault c r ent

in re ses enoug to al ow for directional detection The neutral active c r ent, in this

solution, may b relatively hig (se also 5.2.3.3)

To detect the fault c r ent direction dif erent algorithms may b u ed (varmetric or wat metric

detection prin iple, tran ient analy is, etc.)

5.2.3.3 Earth fa lt dete tion in re istiv impe a c e rthe ne tral (s stem with

e rthing re istor)

The s heme of c r ent flow direction with referen e to the orientation of resid al c r ent

sen ors is s own in Fig re 16 an Fig re 17

The vector diagrams an s mb l definition are in icated in Fig re 18

Figure 16 – Earthin re istor sy tem – dete tio of pha e to e rth fa lt

c r e t dire tio from F I/DSU upstre m from th fa lt loc tion

( a lt d wn tre m from th FPI s/DSU’s lo atio )

Figure 17 – Earthin re istor s stem – dete tio of pha e to e rth fa lt

c r e t dire tion from FPI/DSU downstre m from the fa lt loc tion

C2+I

C3+I

A3I

C2+I

C3+I = I

C2+I

C3+I

I

A2

A1I

C4I

C2+I

C3+I = I

C

C4 +I

B

B

B

e rthin re istor re istiv c re t, ie.:

RCFIII

× C

E) × E – I

C 4) a d e rthin re istor re istiv c re t, i e.:

RCCR

IIII

(E is th p a e to e rth v lta e of th ele tric s stem)

re id al c r e t me s re from F I/DSU in th lo atio o Fe d r 4 for a e rth fa lt

d wn tre m from th F I/DSU, c r e p n in to v ctor s m of c p citiv c re t

CR

II

II

C4 downsream

), the FPI/DSU may b

non-directional, as the direction of the fault c r ent is determined from the fe tures of the

network FPI/DSU sen itivity (minimum thres old set in ) is related only to I

Due to this, the F I/DSU may b non-directional, as the direction of the fault c r ent is

determined from the fe tures of the network (u les there is a large amou t of DER)

Con eq ently, it can b q ite diferent de en in on the fault location – ne r the HV/MV TR

or alon the fe der – an , in the later case, on the typ log of the con u tor upstre m from

the fault location (overhe d, un ergrou d ca le, etc.)

= 0 for a y F I/DSU d wn tre m from a 2Φ or 3Φ fa lt

Figure 19 – Overc r e ts in a ra ial network witho t DER – c r e t c r e t dete tio by

no -dire tion l FPI/DSU (go d s nsitivity c nc rnin ov rc r e t dete tion)

s ort circ it c ntrib tio to a fa lt o a oth r MV fe d r from a smal-me ium rate p wer g n rator

c n e te alo g a h alth MV fe d r (lower th n prote tio rela a d F I/DSU ma imum c re t s tin s)

I

C_

s ort circ it c ntrib tio to a fa lt o a oth r MV fe d r from a smal-me ium rate p wer g n rator

c n e te alo g a h alth MV fe d r (lower th n b th prote tio rela a d F I/DSU ma imum c re t

s tin s)

Figure 2 – Overc r e ts in a ra ial network with ne l gible DER pre e c –

c r e t c r e t d te tion by no -dire tional FPI/DSU

(go d s nsitivity c nc rnin ov rc r e t dete tion)

For phase faults, direction of fault c r ent is determined from the HV/MV tran former in a

radial config ration with no DER or negl gible DER presen e Directional F Is/DSUs are not

C_1 +I

C_1 +I

5.2.5 Ov rc r e t dete tion in pre e c of a large amount of DER (signific ntly

in re sing s ort circ it c r e t v lue )

Figure21a – FPIs/D Us u st e m f om the fault loc tio

Figure 21b – FPIs/D Us d wnst e m fom the fault loc tio

Ke

lo atio of p a e c re t tra sformers (CTs) (or of s n ors for me s reme t of o erc re ts)

I

C

s ort circ it c ntrib tio to a fa lt o MV n twork from HV/MV tra sformer u stre m from th

MV fe d r prote tio a d/or th F I s/DSU’s lo atio alo g th MV fe d r

lo atio alo g Fe d r 4) in c s of 2Φ to 3Φ fa lt d wn tre m from th F I/DSU lo atio o th MV fe d r (it ma

(c ntrib tio of DER d wn tre m from th F I/DSU lo atio alo g Fe d r 4) in c s

of 2Φ to 3Φ fa lt u stre m from th F I/DSU lo atio o th MV fe d r (it ma b lower or hig er th n F I/DSU

ma imum c re t s tin s)

Figure 21 – Ov rc r e ts in a ra ial network with a large amou t of DER –

unrel able fa lt dete tion by non-dire tional FPIs/DSUs

(inc r e t dete tion or e tremely low s nsitivity)

In this situation, DER contributes to s ort circ it c r ents at an location on the distribution

network s p led from the same s bstation bu

Cur ent contribution is not defined, as it strictly related to typ an fe tures of the generator

tec nology an grou din method, in p rtic lar, typical the retical values are:

• s n hronou , in the ran e from a out 6 p r u it (p.u.) to a out 8 p.u nominal c r ent

(s btran ient re ctan e);

• as n hronou (with no self ex itation s stem), in the ran e from a out 8 p.u to a out

10 p.u nominal c r ent, some ten of mi isecon s;

• in erters, in the ran e from a out 1,1 p.u to a out 1,3 p.u nominal c r ent, etc

Minor ef ects may derive, in some cases, from the nature of the primary energ resource:

• fos is;

• win ;

• solar, etc

an /or from the u age of the generator (related to a prod ction c cle, combined he t an

p wer, pure generation, etc.)

From Fig re 21, it is evident that it may not b p s ible to have a cor ect detection of

overc r ents with the indication of their direction, b th from MV fe der protection relay an

from FPIs/DSUs, d e to the imp ct of a large amou t of DER

For overc r ent fault detection in distribution network with a hig presen e of DER,

directional F Is/DSUs are neces ari y req ired b cau e the c r ent contribution to the fault

from DER can b comp ra le to the c r ent contribution to the fault comin from the HV/MV

tran former

In case the fault is close to the FPI/DSU location, the voltage memory prin iple may b

ado ted, con iderin the voltage of at le st one he lth phase (phase to e rth or phase to

phase) b fore the fault ha p n