Design o a low- equency impedance measu emen
sys em applicable o LV g ids in li e condi ions
And ea Ma isco i
DITEN
Uni e si y o Geno a
Geno a, I aly
0000-0002-0096-7305
Abs ac —The design o an impedance measu emen sys em is
discussed o applica ion in low- ol age powe g ids in ope a ion,
add essing he p esence o he g id ol age. A shun injec ion
a angemen is p e e ed, elying hen on he measu emen o
he po ol age and cu en . A Twin-T passi e il e is designed
o bu e he isola ing injec ing ans o me , supp essing he
50 Hz undamen al and a oiding excessi e magne izing cu en
and ol age he signal gene a o connec ed o he seconda y
side. Be o e cons uc ion, he sys em has been simula ed and
pa ame e s alues op imized, showing good pe o mance e en
wi h e y la ge-powe g ids wi h impedance Zgo ens o mΩ.
Zges ima e unce ain y is <1 % a co e age ac o k= 1.
Index Te ms—cu en p obe, impedance measu emen , powe
g ids, unce ain y, ol age p obe.
I. INTRODUCTION
In o ma ion on he impedance alue o an elec ic g id is
use ul om se e al iewpoin s. Knowledge o g id impedance
(Zg) helps in g id planning and ope a ion, con ol and p o-
ec ion, ha a e all p ocesses aking place a he undamen al
equency and in gene al a low equency (LF). Dis o ion
p edic ion and mi iga ion is ano he key poin and we ha e
obse ed a ansi ion o s udies and assessmen om he
adi ional ha monic ange o highe equency, i.e. he sup a-
ha monic (SH) ange [1], [2]. I is well known ha adio-
equency conduc ed emissions and he e icacy o il e s
s ongly depend on g id and load impedance [3]. This is e en
mo e impo an in he ha monic and SH in e als, whe e la ge
impedance a iabili y is expec ed, no only o he equen
connec ion and disconnec ion o sou ces and loads, bu also
o a ious esonance condi ions [4].
Zgmeasu emen me hods in li e condi ions may be clas-
si ied om di e en iewpoin s, e.g. equency- and ime-
domain p ocessing (so ocusing on sine-wa es a a iable
equency o s ep-like o impulse-like signals, including g id
ansien s) [5]. In gene al he p e e ed classi ica ion is be-
ween ac i e and passi e me hods:
•Ac i e me hods injec an exci a ion signal o es Zgby
ei he measu ing di ec ly ol age and cu en ( ol am-
pe ome ic me hods) o di ec and e lec ed componen s
(me hods using Vec o Ne wo k Analyse , VNA). The
exci a ion may be ones o a swep sine in a equency-
domain pe spec i e, o impulsi e o s ep-like signals in a
ime-domain pe spec i e.
–VNA-based me hods, using 2-p obe con igu a ion
[6], pe o m be e in he high- equency ange, and
may su e om non-ideali y o he used p obes
(sa u a ion), complex wi ing o on-si e use and
limi ed VNA pe o mance app oaching LF [7], [8];
– ol ampe ome ic me hods, whe e a es signal is
applied o he measu ing po and ol age and cu en
a e sepa a ely measu ed; his me hod can be used a
high equency [9], [10], bu is sui able also o he
LF in e al ( om nea ly DC up o 9 kHz).
•Passi e me hods exploi ins ead exci a ion signals oc-
cu ing du ing ope a ion, passi ely lis ening o he g id.
These me hods a e pa icula ly sui able o elec ic g ids
wi h la ge powe le els and/o high ol age, whe e ex e -
nal exci a ion would be imp ac ical. A common app oach
is o use a mul i ude o measu ing poin s by means
o phaso measu emen uni s [11], which, howe e , a e
ha dly applicable a he dis ibu ion le el and pose a
signi ican accu acy equi emen o ol age and cu en
ans o me s, besides a igh ime e e ence [12].
Me hods a e in gene al bes applicable in ou -o -se ice
condi ions, no only o a me e ma e o elec ical sa e y, bu
also o achie e be e dynamic ange and o educe noise and
non-linea i y p oblems. This ules ou also any p e-exis ing
ol ages in he measu ed g id. In eali y he con ibu ion o
mode n powe con e e s o he a iabili y o Zgis c ucial
and his can be assessed only in li e and ull ope a ing
condi ions. This en ails he men ioned issues o non-linea i y
and senso s obus ness, besides he p esence o la ge signals a
he mains equency (assumed o simplici y 50 Hz), causing
issues o dynamic ange and wo sening sensi i i y and e ical
esolu ion. This la e poin ep esen s a challenging poin
o no el y wi h espec o o he solu ions, ope a ing always
beyond he undamen al equency [13], [14].
The en i e LF in e al is conside ed ins ead wi h pa icula
a en ion as pa o he Me 4EVCS P ojec [15], s udying
among o he poin s he in luence o Zgon elec ic ehicle
cha ging s a ions and ice e sa.
This pape hus ocuses on he design o a LF Impedance
Measu ing Sys em (IMS), sol ing p oblems ela ed o li e con-
di ions, signal- o-noise a io a he es po ( he In e nal Poin
o Coupling, IPC) wi h espec o dynamic ange equi emen s
o imp o e e ical esolu ion, wi h less demanding injec ed
cu en ampli ude o la ge powe g ids. The pape de elops
om a discussion o equi emen s in Sec ion II, o he design
o he mos ele an IMS componen s, b inging in he no el y
o he p oposed sys em (Sec ion III). Sec ion IV hen ocuses
on selec ed ha dwa e and ins umen a ion and p o ides he un-
ce ain y budge . Feasibili y and pe o mance a e demons a ed
by means o simula ion; es s on he p o o ype will be ca ied
ou in summe o use in he men ioned EU- unded p ojec .
II. PROBLEM REQUIREMENTS AND CONSTRAINTS
Applica ion equi emen s and cons ain s a e conside ed,
examining published al e na i e solu ions, subs an ia ing he
design choices and p o iding discussion o he s a e o he
a o he measu emen o LF Zg. The LF ange spans om
almos DC o he la ges ha monic equency (2 kHz) o he
lowes equency o he RF conduc ed emissions, 9 kHz.
The expec ed Zg alues may ange om ens o mΩ (la ge-
powe g id wi h a 1 MVA ans o me ) up o hund eds o Ω
a esonances.
A. Exis ing ealiza ions
Vol ampe ome ic ac i e me hods injec a es cu en I
supe posed o he no mal ope a ing cu en , measu ing he g id
ol age and cu en a ia ion δVgand δIgand es ima ing Zg
as =δVg/δIg) [16]. Published me hods consis o :
•se ies cu en injec ion by cu en ans o me (CT), e.g.
o he clamp-on ype, as o ea hing esis ance measu e-
men s, wi h injec ed cu en limi ed o abou 200 mA in
a low- esis ance ci cui ( he ea hing ci cui ) [17];
•shun injec ion using powe ampli ie s [18] o sui ably
con olled in e e s [19];
–i is unde lined ha he o me [18] was used o
measu emen s well abo e he undamen al equency
(s a ing a 1 kHz, il e ing ou he undamen al and
i s highes ha monics;
–solu ions using in e e s ins ead can ope a e a ound
he undamen al, bu hei a ings a e simila o g id
loads and qui e expensi e, and ea u e he in insic
limi a ion o semiconduc o s swi ching speed, wi h
maximum applied equency up o 10 kHz.
B. P oposed la ge bandwid h solu ion
Coupling o he es signal I may be implemen ed by a
clamp-on p obe (se ies injec ion) o by di ec injec ion a an
accessible node (shun injec ion), as shown in Fig. 1.
A sweeping exci a ion signal is injec ed in o he In e nal
Poin o Coupling (IPC) po : he g id on he le is cha ac e -
ized by Zgand he load on he igh by Zlquan i ies.
The injec ion geome y is in “de i ed mode” (so h ough a
hi d b anch sha ing he IPC as common node). The b anched
injec ion allows o dis inguish he le and igh hand side sec-
ions, by measu ing he espec i e cu en s. A se ies injec ion,
Fig. 1. IMS schema ic o a hypo he ical 3-ph. g id wi h neu al o
he measu emen o Zgbe ween phase R and N. Cu en p obe (CP)
measu es he cu en Igin o he IPC ( he o he CP in ligh blue is
op ional); he ol age p obe (VP) measu es Vga he IPC po .
ins ead, would ha e made g id and load no sepa able. Igand
Ilmay be measu ed wi h LF clamp-on p obes.
Al hough clamp-on coupling seems less in asi e, as i does
no modi y a all he sys em con igu a ion, he abili y o
injec ing a sui able es cu en in ensi y is comp omised as
soon as Zgis abo e some ens o Ω, educing d as ically
as soon as he sys em app oaches high-impedance egions.
Clamp-on p obes hen ha e non-negligible physical size ha
equi es anyway some modi ica ion, like s ipping cable shea h
o sepa a e he in e nal conduc o s, o use o sho wi e
pa ches o allow one o a ew u ns a ound he clamp. A
p elimina y check wi h he clamp-on p obes equipping he
Chau in A noux mod. 6471 me e [17] has shown ha injec ed
cu en in a simula ed g id is limi ed o abou a ew ens o
mA app oaching o e loading and only abo e 100 Hz.
Ano he d awback is ha clamp-on coupling applies a
se ies injec ion allowing he de e mina ion only o Zgand
Zlcombined. The use o shun injec ion a he coupling po ,
con e sely, allows sepa a ing he cu en lowing in o he wo
di ec ions, leading o sepa a e e alua ion o Zgand Zl.
The p oposed solu ion consis s o a di ec signal injec ion
by a coupling ans o me , d i en by a powe ampli ie . Being
he selec ed band co e ing all LF componen s including he
undamen al and i s ha monics, he una oidable coupling and
consequen ial a ing o componen s is a ou ably educed by
using a no ch il e o he 50 Hz undamen al (adjus able
o 60 Hz ). The no ch il e has wo bene i s: educ ion o
powe dissipa ion on downs eam de ices and educ ion o
he magne izing cu en lowing in o he ans o me , allowing
using ans o me s wi h lowe nominal ol age. Such il e is
Fig. 2. Twin-T no ch il e schema ic.
di ec ly connec ed o he g id and he bes a chi ec u e is he
win-T no ch il e shown in Fig. 2.
Fo g ids wi h highe nominal ol age, a 230 V ans o me
may s ill be used, p o ided ha magne izing cu en is no
excessi e and ol age insula ion a ings a e no app oached
du ing no mal use.
Fo he es signal gene a ion and i s coupling, wha is he
equi ed I in ensi y? The Zg,min alue implies a co esponding
I ,max, once he minimum measu able po ol age V ,min is
conside ed. This quan i y is de e mined no only by he ins u-
men a ion, bu also by he exis ing noise in he LF in e al.
Assuming V ,min = 1 mV, he esul ing I ,max = 100 mA, as
mos o ea h esis ance and aul -loop impedance es e s [17].
Conside ing he V measu emen , ypical di e en ial ol age
p obe (VP) noise is in he o de o some mV o a en h o mV
[20]–[22], measu ed as b oadband ms and educed by almos
an o de o magni ude i measu ed in he LF in e al only.
An impo an poin o conside is he possible VP non-
linea i y in he p esence o a la ge undamen al signal. This
is ne e documen ed o au ho ’s knowledge, bu we can say
ha i occu s, i will a ec only he undamen al ha monics,
ha , o s ay on he sa e side, may be disca ded om he
pool o measu ed equencies du ing pos -p ocessing. Anyway
his is an in e es ing poin ha is pa o he ac i i ies in he
Me 4EVCS P ojec [15].
The da a acquisi ion sys em (DAS), ins ead, su e s om he
inabili y o ejec ing he undamen al ha de e mines hus he
equi ed ull scale. Also in his case an imp o emen comes
om he use o a downs eam no ch il e .
Assuming a VP cons an a enua ion (100 o he Tes ec SI-
9010), we can eason on he alues a he injec ing po o
ul il equi emen s o de ec abili y and signal- o-noise a io a
he DAS and easibili y o cu en and powe a ing. This is
summa ized below, ocusing on some de ices and i ems o
equipmen o exempli ica ion pu poses.
• he 400 V maximum nominal ol age se s he DAS ull
scale; he no ch il e can educe i down o abou 15 V,
compa able o he la ges ha monic dis o ion compo-
nen s; he VP a enua ion (100 o he Tes ec SI-9010)
ans e s his o he DAS as 200 mVpk;
• he 16-bi DAS has a quan iza ion noise loo in he o de
o 1.8µV ms o 4.4µV ms, gi ing 0.4 mV ms o e he
en i e 10 kHz bandwid h; his alue is s ill smalle han
he assumed VP ou pu noise, ha o he Tes ec SI-9010
amoun s o 0.9 mV ms; assuming a esolu ion equency
o 10 Hz he noise in each equency bin amoun s o
0.03 mV ms, o 3 mV ms a he IPC (g id side), ha is
an es ima e o he IMS sensi i i y;
• he assumed nominal I = 100 mA ms causes he IPC
ol age o s ay abo e he sensi i i y o Zg>30 mΩ;
la ge es cu en in ensi y is necessa y o ex emely s i
g ids; in a eal-wo ld scena io 30 mΩ is he impedance
o a 630 kVA MV/LV ans o me accoun ing o some
me e s o cable;
•assuming an o e es ima ing I ,max = 0.5 A ms in a
400 V ms phase- o-phase con igu a ion, leads o 200 VA
o a ing o he s ep-up ans o me .
III. IMS DESIGN AND SIZING
A. Twin-T no ch il e
This is a well-known no ch il e a chi ec u e and p obably
he only sui able ci cui o passi e implemen a ion. Ac i e
implemen a ions may ins ead ely on al e na i e schemes, like
he Fliege, Wien, e c.
The Twin-T ci cui has a known op imized o m whe e he
ans e sal componen s R3and C3a e equal o R/2and 2C,
espec i ely, ha ing he se ies componen s equal o Rand
C. The gene al ans e unc ion (neglec ing sou ce and load
impedances) is a hi d-o de polynomial (ha ing 3 capaci o s),
ha simpli ies o a second-o de one wi h he pa ame e s
choice abo e (ze o-pole cancella ion). Unde such condi ions
he no ch equency can be de e mined as:
0=1
2πRC (1)
Values in he Twin-T no ch il e we e de e mined ading
o powe dissipa ion, educ ion o he magne izing cu en ,
a oiding excessi e impedance a o he equencies no o limi
he injec ed cu en ampli ude. A i s e sion was iden i ied
( e sion 1) using C= 4.7µF, a ailable as he la ges alue o
sa e y capaci o s wi h he 400 V ms ol age a ing, and R=
680 Ω powe esis o s ( he exac alue being 677.3 Ω, bu no
including sou ce and load esis ance, so achie ed p ac ically
by ine uning on he inal implemen a ion).
A second e sion ( e sion 2) o he Twin-T was also
conside ed, whe e a ac o o 2 is applied, educing he esis o
alues o one hal and doubling he capaci o s alues wi h he
objec i e o inc easing he injec ed cu en ampli ude.
B. T ans o me and sou cing impedance
The ans o me was selec ed wi h con igu able p ima y and
seconda y windings, bo h spli in o wo hal es (2×115 V/2×
24 V) wi h a a ed powe o 200 VA, o limi i s weigh , and
elying on he ac ha powe a ing is speci ied o con inuous
ope a ion a he highes ope a ing empe a u e.
The p ima y induc ance o he wo se ies-connec ed wind-
ings is abou 0.9 H, o 300 Ω a 50 Hz. As an icipa ed, he
conside ed Twin-T il e con igu a ions ha e been he C=
4.7µF&R= 680 Ω (“ e sion 1”) and he C= 9.4µF&R=
340 Ω (“ e sion 2”), he la e wi h a sligh ly la ge dissipa ion,
bu allowing a highe injec ed cu en (almos double) o he
same es signal ampli ude.
Fig. 3. Vol age coupled on he signal gene a o wi h 100 V g id
ol age wi h (blue) and wi hou (o ange) no ch il e .
Dissipa ion alues in Wa e shown in Table I. They we e
calcula ed using a maximum undamen al ampli ude wi h
wo s -case la ge dis o ion o each equency in e al, i.e.
a he undamen al, a he i s low-o de ha monics, and
hen up o 3 kHz. The p eponde an dissipa ion is a he
undamen al, as expec ed, wi h much smalle alue a he
ha monic equencies, luc ua ing as he cu en changes pa h
h ough he win-T ci cui . The highes dissipa ion is o R1
and amoun o 110 W.
TABLE I. Dissipa ion o he wo win-T il e e sions.
F eq. Vol age Twin-T e sion 1 Twin-T e sion 2
(Hz) (V ms) PR1PR2PR3PR1PR2PR3
50 230 89.1 17.7 35.7 97.5 19.4 39.0
100 30 1.09 0.12 0.49 2.12 0.39 0.97
150 30 1.17 0.13 0.55 2.25 0.46 1.19
250 15 0.30 0.06 0.16 0.58 0.23 0.44
350 15 0.30 0.10 0.20 0.59 0.39 0.64
450 15 0.30 0.17 0.26 0.60 0.56 0.87
550 15 0.30 0.27 0.37 0.61 0.70 1.09
650 15 0.31 0.38 0.49 0.62 0.80 1.25
750 15 0.31 0.47 0.62 0.63 0.85 1.36
1500 15 0.33 0.47 0.78 0.66 0.78 1.42
2250 15 0.33 0.40 0.72 0.66 0.72 1.38
2250 15 0.33 0.37 0.70 0.66 0.70 1.36
The e ec i eness o he no ch il e is e i ied by simula ing
he sys em wi h and wi hou i , assuming a la 100 V g id
ol age a all equencies and looking a he ol age coupled
on he signal gene a o . Such ampli ude was chosen because
much close o ac ual alues, p o iding di ec indica ion o he
expec ed signal magni ude. The esul s a e shown in Fig. 3:
he 50 Hz is supp essed by almos 3 o de s o magni ude and
he la ges ha monics by app oxima ely a ac o o 3, ha ing
iden ical beha iou abo e 1 kHz.
The o e all beha iou is e i ied by simula ing he injec ion
o he es signal in o a g id o a iable impedance Zg, made o
a se ies connec ion o esis ance Rgand induc ance Lg. Fig. 4
shows he injec ed cu en in o he g id Ig, he IPC ol age
Vg, he p ima y ol age V1and he seconda y ol age V2 o
Rs= 1 Ω. A wide ange o g id pa ame e s is swep , om
la ge esis i e (Rg= 200 Ω) o mode a e esis i e (Rg= 2 Ω),
o e y low alues ypical o a la ge sho -ci cui powe a io
g id (Rg= 0.02 Ω and Lg= 20 µH).
The esul s o 1 Ω (Fig. 4) demons a e ha Igmain ains
Fig. 4. Vol age and cu en le els o e he 10 Hz o 10 000 Hz
in e al: black (Rg= 2 Ω), blue (Rg= 200 Ω), ed (Rg= 20 Ω
and Lg= 2 mH) and g een (Rg= 0.02 Ω and Lg= 20 µH). Tes
signal gene a ion wi h Rs= 1 Ω.
a le el o 100 mA o 200 mA wi h he desi ed no ch a ound
50 Hz, cha ac e ized by only 5 mA a 50 Hz and abou 40 mA
a 40 and 60 Hz.
A sligh ly mo e uni o m cu en injec ion can be achie ed
inc easing he gene a o esis ance a he expense o a lowe
injec ed cu en (abou 30 mA o 10 Ω). One may wonde i
some equaliza ion wi h educ ion o cu en a high equency
may be achie ed by modi ying he gene a o impedance.
Simula ions we e ca ied ou wi h an induc o o 0.1 mH o
10 mH added in se ies o Rs= 0.1 Ω, and he esul s a e
shown in Fig. 5. This maximizes he cu en injec ed a LF
(200 mA applying a es signal o 20 V) and educes he high-
equency cu en , keeping i below abou 1 A wi h he se ies
induc ance >1 mH.
IV. LF IMS ARCHITECTURE AND UNCERTAINTY
A. Implemen a ion
The blocks discussed and designed in he p e ious sec ion
a e assembled o o m he h ee unc ions o he IMS: es
cu en injec ion, po ol age measu emen and b anch cu en
measu emen , all connec ed o he DAS.
The IPC ol age can hen be measu ed by using an isola ed
ol age p obe and he Tes ec SI 9010 was selec ed o a
Fig. 5. Vol age and cu en le els o e he 10 Hz o 10 000 Hz in e al
wi h he mos challenging g id impedance o Zg= 20 mΩ + 40 µH:
g een (Zs= 0.1 Ω + 0.1 mH), magen a (Zs= 0.1 Ω + 1 mH) and
cyan (Zs= 0.1 Ω + 10 mH).
ma e o a ailabili y and e y low in e nal noise, besides he
abundan insula ion le el.
The cu en p obes used o he measu emen o Igand Il
a e om he CA 6471 ins umen , bu hey may be eplaced
by Rogowski coils o closed luxga e senso s, wi h di e en
unce ain y con ibu ions.
The ac i e win-T il e is used o ejec he incoming
50 Hz om he ol age and cu en p obes. The alues a e
op imized selec ing a ailable esis o s alues (26.1 kΩ) leading
o a capaci ance o 122 nF, ob ained by pa alleling wo s an-
da d alues. The so ob ained no ch equency is 49.983 Hz:
C21 =C22 =C23/2 = 122 nF and R21 =R22 = 2 ×R23 =
26.1 kΩ. Such esis o s can be ound wi h 0.1 % accu acy
and 10 ppm/°C empe a u e coe icien . Capaci o s a e 1 % o
2 % and he wo s -case empe a u e coe icien is 30 ppm/°C,
al hough much smalle a oom empe a u e up o abou 45 ◦C.
B. Unce ain y budge
The discussed coupling me hod h ough he s ep-up ans-
o me and Twin-T no ch il e does no con ibu e o unce -
ain y, as all quan i ies ha de ine he g id impedance a e
sepa a ely measu ed. Ra he , co ec sizing and a ing allows
a mo e ideal beha iou , wi h a su icien ly la es cu en and
accep able dissipa ion and sel hea ing.
Fig. 6. Ac i e Twin-T no ch il e FR o di e en gain G alues.
The g id impedance Zg, de e mined as he a ion o he
IPC ol age Vgand g id cu en Ig, has hus a s aigh o wa d
unce ain y exp ession:
u{Zg}=q(u{Vg})2+ (u{Ig})2(2)
The ac o s con ibu ing o he unce ain y o Vgand Ig
a e he unce ain y associa ed o he espec i e p obes and he
wo DAS channels, including he signal no ch il e s be o e
he DAS channels.
The cu en p obe (CA-C180) has a decla ed accu acy o
±0.5 % wi h a phase shi o less han 1 deg a 50 Hz. In
addi ion o he wo e ms o unce ain y a e he in luence o
adjacen conduc o s (decla ed less han 0.05 % a 50 Hz) and
o conduc o posi ioning wi hin he p obe jaws (decla ed less
han 0.1 % up o 400 Hz). The ol age p obe (Si-9010) has
a decla ed accu acy o ±2 % [22]. This is a conse a i e
s a emen ha also lacks he phase shi cha ac e iza ion: an
ad-hoc calib a ion should possibly educe i o less han 1 %.
The DAS channels ha e he ollowing con ibu ion:
•The quan iza ion noise e m can be heo e ically es i-
ma ed a 0.02 % o a 12-bi sys em wi h a ull scale
signal; i he applied signal is only 1 % o he ull scale,
he con ibu ion becomes 2 % ela i e, la ge han ha
o p obes. The p esence o he undamen al o ces he
selec ion o a la ge ange; his can be a oided only wi h
an ac i e no ch il e . This does no occu when measu ing
only he SH ange, as all p obes ha e high-pass beha iou .
•The e ical ampli ude accu acy (aka “DC accu acy”) is
be e han 1 % [23], bu can be educed d as ically by
indi idual calib a ion; he emaining empe a u e depen-
dency and non-linea i y e ms a e no be e documen ed.
The ac i e no ch win-T il e (designed as in [24]) is
cha ac e ized by he capaci o s accu acy in he i s place
(2 %), bu indi idual calib a ion can educe i o he used
ins umen unce ain y plus he con ibu ion o he empe a u e
a iabili y, <300 ppm o ±10 ◦Co a ia ion.
Fla ness o i s equency esponse (FR) can be co ec ed
a e calib a ion, bu i helps ha ing an almos ideal channel
esponse. The esul s o PSpice simula ions a e shown in
Fig. 6, o a ange o alues o he eedback gain G and,
as a consequence, o he ac o o me i .
Assuming all accu acy e ms wi h a uni o m dis ibu ion
o he e o and he use o he no ch il e o undamen al
supp ession, he esul ing unce ain y o Zgis less han ±1 %
wi h uni a y co e age ac o ( elying on wha decla ed in he
espec i e da ashee s).
V. CONCLUSION
The design o a LF IMS was discussed, ocusing on
easibili y o a ing, powe dissipa ion, dynamic ange and
esolu ion, as “li e condi ions” implies he p esence o he
g id ol age causing he ollowing p oblems: elec ical sa e y
issues, sa u a ion o he coupling ans o me a highes ol -
ages, dissipa ion and un a ou able dynamic ange a he DAS.
The sys em was kep simple, using a coupling ans o me o
injec in o he IPC, bu e ed by a 50 Hz passi e win-T no ch
il e .
The e ec i eness o he passi e no ch il e has been demon-
s a ed, showing a signi ican educ ion o he undamen al
(almos 3 o de s o magni ude) and i s ha monics, educing
bo h chances o sa u a ion o he ans o me i used a highe
nominal ol ages and he low o la ge undamen al cu en a
he seconda y and in o he signal gene a o .
The g id impedance is es ima ed by a simple IPC ol -
age/cu en a io and i s unce ain y u{Zg}is de i ed om ha
o he measu ing p obes and DAS. Wi hou special co ec ions
and ad-hoc calib a ions, u{Zg}was es ima ed be e han 1 %
wi h k= 1 co e age ac o i supp essing he undamen al
la ge swing. The dynamic ange may be in ac signi ican ly
imp o ed by adding an ac i e no ch il e on each channel,
allowing a educ ion o he ull scale by mo e han an o de
o magni ude and imp o ed sensi i i y.
The p oposed IMS can be applied o online eal- ime
measu emen o he g id impedance du ing ope a ion as he
in ensi y o he injec ed signal can be adap ed o a oid in e -
e ence. The sys em is lexible o he choice o he ol age
and cu en p obes o adap o he pa icula cha ac e is ics o
he g id and loads.
This IMS add esses one o he equi emen s o impedance
measu emen in he DC o 9 kHz equency in e al o he
Me 4EVCS p ojec [15]. A e i s cons uc ion in summe
2025, i will be ex ensi ely used in he planned es campaigns.
ACKNOWLEDGMENT
The p ojec 23IND06 Me 4EVCS ecei es unding om
he Eu opean Pa ne ship on Me ology, co- inanced om he
Eu opean Union’s Ho izon Eu ope Resea ch and Inno a ion
P og amme and by he Pa icipa ing S a es.
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