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Detection of non-technical losses in smart meter data based on load curve profiling and time series analysis

Abstract

This work has been partially supported by the Basque Government under the ELKARTEK program (BID3ABI project, grant ref. KK-2015/0000080), as well as by the Spanish Ministerio de Energía y Competitividad under the RETOS program (OSIRIS project, grant ref. RTC-2014-1556-3).

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Detection of non-technical losses in smart meter data based on load curve profiling and time series analysis

Author: Oregui Bravo, Izaskun,Del Ser Lorente, Javier,Villar Rodríguez, Esther,Bilbao Maron, Miren Nekane,Gil López, Sergio
Publisher: Elsevier
Year: 2017
DOI: 10.1016/j.energy.2017.07.008
Source: https://addi.ehu.eus/bitstream/10810/78659/3/2017_Detection_of_non_technical_losses_in_sma.pdf
De ec ion o Non-Technical Losses in Sma Me e Da a
based on Load Cu e P o iling and Time Se ies Analysis
Es he Villa -Rod igueza, Ja ie Del Se a,b,c,∗, Izaskun O egia,
Mi en Nekane Bilbaob, and Se gio Gil-Lopeza
aTECNALIA, 48160 De io, Bizkaia, Spain.
bUni e si y o he Basque Coun y (EHU/UPV), 48013 Bilbao, Bizkaia, Spain.
cBasque Cen e o Applied Ma hema ics (BCAM), 48009 Bilbao, Bizkaia, Spain.
Abs ac
The ad en and p og essi e deploymen o he so-called Sma G id has un-
leashed a p o i able po olio o new possibili ies o an e icien manage-
men o he low- ol age dis ibu ion ne wo k suppo ed by he in oduc ion
o in o ma ion and communica ion echnologies o exploi i s digi aliza ion.
Among all such possibili ies his wo k ocuses on he de ec ion o anoma-
lous ene gy consump ion aces: dis ega ding whe he hey a e due o mal-
unc ioning me e ing equipmen o audulen pu poses, s ong e o s a e
in es ed by u ili ies o de ec such ou lying e en s and add ess hem o op-
imize he powe dis ibu ion and a oid signi ican income cos s. In his
con ex his manusc ip in oduce a no el algo i hmic app oach o he iden-
i ica ion o consump ion ou lie s in Sma G ids ha elies on concep s om
p obabilis ic da a mining and ime se ies analysis. A key ing edien o he
p oposed echnique is i s abili y o accommoda e ime i egula i ies – shi s
and wa ps – in he consump ion habi s o he use by concen a ing on he
shape o he consump ion a he han on i s empo al p ope ies. Simula-
ion esul s o e eal da a om a Spanish u ili y a e p esen ed and discussed,
om whe e i is concluded ha he p oposed app oach excels a de ec ing
di e en ou lie cases emula ed on he a o emen ioned consump ion aces.
Keywo ds: Sma G ids; Sma Me e Da a; Non-Technical Losses; Ou lie
De ec ion.
∗Co esponding au ho : ja[email p o ec ed] (P o . D . Ja ie Del Se ). TEC-
NALIA. P. Tecnologico Bizkaia, Ed. 700, 48160 De io, Spain. Tl: +34 946 430 50. Fax:
+34 901 760 009. E-mail: ja[email p o ec ed].
June 26, 2017
This is he accep ed manusc ip o he a icle ha appea ed in inal o m in Ene gy 137 : 118-128 (2017), which has
been published in inal o m a h ps://doi.o g/10.1016/j.ene gy.2017.07.008. © 2017 Else ie unde CC BY-NC-ND
license (h p://c ea i ecommons.o g/licenses/by-nc-nd/4.0/)
1. In oduc ion
Acco ding o he o icial de ini ion in oduced by he Ene gy Indepen-
dence and Secu i y Ac o 2007 [1], Sma G ids can be unde s ood in he
wide sense as he echnological e o s o mode nize and digi ize he elec ici y
dis ibu ion sys em o a na ion o ensu e, in an scalable manne , he imp o ed
eliabili y, secu i y and e iciency o he g id, as well as o gua an ee an op i-
mized managemen o i s esou ces and ope a ion. This de ini ion desc ibes
such a e m as a comp ehensi e se o ope a ional esou ces es ablished o
gua an ee an e icien powe ansmission and elec ici y dis ibu ion, paying
an special a en ion o eliabili y and secu i y.
The ad en and p og essi e deploymen o he so-called Sma G id has
unleashed a p o i able po olio o new possibili ies o an e icien manage-
men o he low and medium ol age dis ibu ion ne wo k, suppo ed by he
in oduc ion o in o ma ion and communica ion echnologies o exploi i s
digi aliza ion. In his con ex , he deploymen o he Ad anced Me e ing
In as uc u es (AMIs) allows he u ili ies o acqui e ine-g ained da a abou
he eal consump ion o end-use s (no based on es ima ions o mon hly mea-
su emen s), which esul s essen ial o acqui e deepe insigh s on how, when
and whe e ene gy is dis ibu ed and consumed h ough he ne wo k [2, 3, 4].
This ac is pa icula ly c ucial in ega ds o he aceabili y and cha ac-
e iza ion o elec ical losses, which accoun o he di e ence be ween he
amoun o ene gy dis ibu ed by he elec ical dis ibu ion company and he
amoun o ene gy paid by he consume s. Such losses may be due o wo
main con ibu ing causes: 1) losses inhe en o he ans o ma ion and dis-
ibu ion o ene gy, which a e p opo ional o he squa ed o elec ical cu en
and widely e e ed o as Technical Losses (TL); and 2) non- echnical losses
(NTLs), associa ed o e oneous eadings, de ec ed sma me e s o aud [5].
This wo k ocuses on he de ec ion o ene gy consump ion aces which
con ibu e o NTLs: dis ega ding whe he hey a e due o mal unc ioning
me e ing equipmen o audulen pu poses. As men ioned by [6, 7, 8] he
amoun o ene gy loss in he dis ibu ion g ids a ies be ween 7 – 50 % o he
o al deli e ed ene gy (depending o he coun y and he cha ac e is ics o
he dis ibu ion ne wo k), which undoub edly jus i ies he s ong e o s ha
u ili ies a e in es ing owa ds de ec ing and inspec ing a ypical consump ion
aces o ul ima ely a oid signi ican economical losses. As s a ed in [9], only
in US be ween 1 and 10 billion wo h o elec ici y was s olen in he la e 90s,
showing an inc emen be ween 5-10% in he las wo decades wi h a ema k-
2
able 40% and beyond in Sou heas Asia [10]. In addi ion, he iden i ica ion o
a ypicali ies p o ides u he p o i able ad an ages beyond aud assessmen :
by p ope ly cha ac e izing he s a is ics o he consump ion aces egis e ed
o e he powe g id, he powe dis ibu ion can be op imized by ma ching
gene a ion o consump ion, he eby a oiding ne wo k unde -dimensioning
and elec ical su ge.
In e es ingly o he scope o his wo k, ene gy he accoun s o he
majo i y o easons o he a o emen ioned non- echnical losses. The e a e
indeed e y di e se me hods by which malicious consume s educe illegally
he consump ion moni o ed by he ins alled sma equipmen , pa icula ly
in he las s age o he dis ibu ion ne wo k. One o he mos usual o ms o
elec ici y he is aud, by which he use delibe a ely a emp s a decei -
ing he ene gy supplie (u ili y) a hand. This can be achie ed by di e se
means such as me e ampe ing, by which he me e is o ced o egis e
a lowe powe eading han he eal consump ion o he use . While o he
o ms o elec ici y he p e ail ac oss di e en coun ies and cul u es (e.g.
billing i egula i ies), his wo k e ol es a ound hose audulen cases when
he non- echnical loss may be e lec ed in a beha io al change o he ene gy
consump ion ace egis e ed by he me e ing de ice. In his ega d, bo h
ampe ing and elec ici y he all wi hin he scope o his wo k: hey cons i-
u e a p io i ized a ge o mos u ili y companies a ound he wo ld, due o
he se e e consequences o hese phenomena (i.e. highe elec ici y a es o
paying consume s, inc eased isk o i e o elec ocu ion due o imp ope ly
ins alled bypasses and in gene al, a educed g id eliabili y).
F om a da a based pe spec i e, a change in he ene gy consump ion p o ile
o a use con ibu ing o NTLs can be unde s ood as a de ia ing obse a-
ion in he ime se ies ha models such a p o ile, whose s a is ics make i
qui e likely o be gene a ed by ano he di e en unde lying beha io [11].
Howe e , no mal load p o iling in he low- ol age ne wo k can be p oduced
by he agg ega ion o di e en , ye ela ed beha io al componen s (season-
ali y, daily and weekly s a is ical a iabili y, habi s changes, among o he s)
ha di e om each o he in bo h, ampli ude (i.e. amoun o ene gy con-
sumed om he powe g id due o di e en load consump ions) and ime
domains (co espondingly, he s a is ical consump ion schedule o he se o
use s’ loads along he day o week). I is he dissimila i y o any new con-
sump ion ace o any o hose p e iously lea ned beha io al pa e ns (load
p o iling) wha should di e bo h beha io s (no mal and NTLs). Fu he -
mo e, he de ec ion o anomalous obse a ions allows o he in e ence o
3
mo e obus models by disca ding hose ins ances esul ed om he s ongly
i egula samples, which could de ia e he models om he ep esen a ion o
s a is ically signi ican egula ends in he consump ion habi s o he use
unde analysis. This being said, an ou lie de ec ion me hod can be de ined
as he ask o classi ying elemen s as no mal o di e ing wi h espec o he
s a is ical egula i y cha ac e izing a da ase . A his poin he concep o
egula i y mus be de e mined by he add essed applica ion scena io.
In his con ex , a baseline axonomy o ou lie de ec ion algo i hms com-
p ises 1) pa ame ic me hods ha ely on p io hypo hesis abou he s a-
is ical model gene a ing he da a; and 2) model- ee, non-pa ame ic ech-
niques, which a oid any p io assump ion abou he unde lying dis ibu ion
o he da a o s a is ical pa ame e es ima es. Among he la e we ocus
on dis ance-based unsupe ised ou lie de ec ion app oaches, which gene -
ally hinge on local dis ance measu emen s (no o accoun ing beha io al
di e ences) and a e capable o e icien ly handling la ge da ase s [12]. By
p ope ly de ining a dis ance o measu e o simila i y be ween samples, sub-
sequen da a mining p ocedu es such as clus e analysis can iden i y g oup
o samples ha do no belong o he se o disco e ed da a clus e s. This
iden i ica ion can be done based on di e en dis ance-based c i e ia, such as
he densi y o samples wi hin a gi en dis ance h eshold. In all such cases
he selec ion o he dis ance me ic is a key poin o his collec ion o ech-
niques, since he simila i y c i e ion – which oughly depends on he chosen
dis ance me ic – will guide he whole iden i ica ion p ocess. The e o e, i is
clea ha he bes simila i y unc ion mus be complian wi h he na u e o
da a and he speci ic pa icula i ies o he applica ion.
In his ega d, se e al p io con ibu ions ha e hi he o deal wi h he
iden i ica ion o NTLs in ene gy consump ion aces. To begin wi h, se e al
con ibu ions ha e g a i a ed on he use o machine lea ning models o e su-
pe ised da ase s, such as Suppo Vec o Machines [13, 14, 15, 16, 17, 18],
Neu al Ne wo ks [19, 20, 21], Ex eme Lea ning Machines [22], Pa h Fo es s
[23, 24], Decision T ees [25, 26, 27], model ensembles [28], and s a is ical
me hods [29, 30]. Howe e , all such p e ious wo k builds upon he assump-
ion ha supe ised da ase s cap u e he en i e casuis y o symp oma ic
anomalies o in e es o aud de ec ion and/o elec ici y he , which no
only un ealis ic in p ac ice bu also yields highly imbalanced da ase s ha
subsequen ly jeopa dize he model lea ning p ocess. By con as , unsupe -
ised anomaly de ec ion in Sma G ids o e ides any need o p e iously
labeled da a, ye makes he e alua ion and uning o he model ha d o
4
pe o m due o he non-u iliza ion o posi i e examples du ing he cons uc-
ion o he lea ne . The li e a u e dealing wi h elec ici y aud using non-
supe ised lea ning models has been ela i ely sca ce, wi h Sel O ganizing
Maps [31] and uzzy clus e ing schemes [32] mos ly used o da e.
This manusc ip in oduces a no el algo i hmic app oach o acqui ing
knowledge o cus ome ’s beha io s (load p o iling), which allows o he iden-
i ica ion o consump ion beha io al ou lie s in Sma G ids based on he
hou ly measu emen s p o ided by he AMIs. The p oposed scheme ad ances
o e he s a e o he a by combining p obabilis ic da a mining and ime se-
ies analysis; we adop he so-called Dynamic Time Wa ping (DTW) me ic
as he measu e o simila i y be ween consump ion aces egis e ed by he
use unde analysis, by which such sequences a e aligned in a dynamic, non-
linea ashion dis ega ding any shi s o wa ps along ime [33]. This me ic is
hen used wi hin wo di e en dis ance-based lea ning models, bo h elying
on densi y es ima ions o de ec anomalous pa e ns. A u he no el ing e-
dien o his wo k is a ace encoding s a egy ha depends on he spanned
hou ly s a is ical anges o e e y use , which inc eases he lexibili y o he
models o a oid alse ala ms. The pe o mance o he de i ed schemes is as-
sessed and discussed based on simula ion esul s compu ed o e eal AMI
da a cap u ed by a Spanish u ili y. Gi en he ob ained sco es we conclude
ha he p oposed me hod accommoda es i egula i ies o he analyzed con-
sump ion aces along ime by ocusing exclusi ely on hei shape.
The es o he manusc ip is s uc u ed as ollows: Sec ion 2 poses he
no a ion used h oughou he manusc ip , and o mula es he p oblem o ou -
lie de ec ion con ex ualized o he applica ion ackled in his manusc ip .
Sec ion 3 p o ides an o e iew o he p oposed app oach, emphasizing on i s
cons i uen elemen s in subsec ions he ein. Nex , Sec ion 4 desc ibes he
da ase u ilized o pe o mance assessmen , jus i ies he di e en emula ed
cases o e such da a and discusses he ob ained esul s. Finally conclusions
a e gi en in Sec ion 5 along wi h an ou line o u u e esea ch lines.
2. No a ion and P oblem S a emen
As depic ed in Figu e 1, we assume ha an ene gy dis ibu ion company
has deployed a se o Nsma me e s o moni o he consump ion o pa o
i s cus ome po olio. Le da a samples egis e ed by he n- h sma me e
be deno ed as xn.
={xn
}Tn
=1, whe e s ands o he ime dimension disc e ized
as pe he g anula i y n
s[minu es] by which he sma me e eco ds da a (e.g.
5

hou ly, n
s= 60 minu es). He e Tndeno es he o al numbe o samples ead
o he cus ome a hand, which may a y among di e en cus ome s due o
e.g. he da e on which he sma me e was ins alled in he use p emises. We
u he conside ha he minimum decisional uni o he ou lie de ec ion
model is an en i e day (24 hou s), o which xn.
={xn
}Tn
=1 can be eshaped
as a ma ix Xn, wi h each column con aining he (24 ·60)/ n
s alues ha he
me e o cus ome n∈ {1, . . . , N}samples du ing each day. Fo he sake
o simplici y, in o egoing de i a ions we will o ce n
s= 60 minu es ∀n, such
ha Xnwill ha e 24 eadings pe e e y day ou o a o al o Dn.
=⌊Tn/24⌋
days moni o ed o cus ome n. Samples o day d∈ {1, . . . , Dn}will be
exp essed as Xn
d, i.e. by he d- h ow in Xn.
The aim o an ou lie de ec ion model Mn
θ(Xn
d′;Xn) is o in e , o use n,
whe he a new daily consump ion ace Xn
d′cap u ed by he sma me e o
use n ollows he same dis ibu ion as ha cha ac e izing Xn(decla ing i o
be an inlie ) o , ins ead, di e s signi ican ly (co espondingly, is an ou lie ).
The la e case se es as a igge o a u he inspec ion p ocess o con i m
whe he he beha io al change is due o e.g. aud. The model is con olled
by a se o pa ame e s collec ed in θ, which pe mi o balance be ween he
T ue Posi i e Ra e (TPR, also e e ed o as sensi i i y o ecall) and he
T ue Nega i e Ra e o he model (namely, TNR o speci ici y) [34].
A his poin i is impo an o no e ha o measu ing he TNR and
TPR me ics o any ou lie de ec ion model we need supe ised labels o
he es aces o e which such me ics a e compu ed. In o he wo ds, o
assessing he pe o mance o an ou lie de ec ion algo i hm i is manda o y
o know a p io i whe he he dis ibu ion u ilized o p oducing each o he
es aces co esponds o ha u ilized o modeling he ou lie p o o ype
ha he model should de ec .
We e e as ℓn
d′
.
=Mn
θ(Xn
d′;Xn)∈ {0,1} o he p edic ed label by he
model o es ace Xn
d′. Bea ing his de ini ion in mind, he TPR and
TNR sco es achie ed by model Mn
θ(·) o e a es da ase {Xn
d′}D′
d′=1 a e
gi en by TNR (Mn
θ) and TPR (Mn
θ), espec i ely. No ewo hy is o high-
ligh ha hese me ics implici ly measu e he ex en o which he model is
adap ed o disc imina e among he dis ibu ion 1
X(x) ollowed by ou lie s
wi hin {Xn
d′}D′
d′=1 om ha ollowed by egula aces in Xn(co espondingly,
0
X(x)). While lea ning 0
X(x) is a ma e o i ing he model o Xnon he
assump ion ha all consump ion aces he ein a e legi ima e, he casuis y
o ou lie s dic a ed by 1
X(x) is d i en by he speci ici ies o he applica ion
scena io i sel . To his end, in his wo k we ocus on ou di e en hypo heses
6
o he es ace Xn
d′which Mn
θ(·) should decla e as an inlie o an ou lie :
1. The es ace Xn
d′belongs o he no mal beha io al dis ibu ion o cus-
ome n, i.e. Xn
d′∼ 0
X(x) wi h high likelihood. In his case he model
should decla e ha Xn
d′is an inlie , namely, ℓn
d′
.
=Mn
θ(Xn
d′;Xn) = 0.
2. The es ace Xn
d′ alls again wi hin he ace space spanned by he no mal
beha io o cus ome n. Howe e , in his case a shape-p ese ing shi (o
δ∈[−∆max,∆max] hou s) in he ime domain is p esen in he es ace
o accoun o exogenous ac o s a ec ing he consump ion pa e ns o he
use along he ime domain. Fo ins ance, a domes ic use does no neces-
sa ily use his/he home appliances a he same ime du ing he week, bu
i is o en he case ha such home du ies ollow a egula pa e n in hei
execu ion. In his case he model should be elas ic enough o accommo-
da e his ime a iabili y, ocus on pu ely shape- ela ed cha ac e iza ion
o he consump ion pa e ns and p edic ha ℓn
d′= 0.
3. The es ace Xn
d′ e lec s a sub le ene gy loss o e i s ime span wi h e-
spec o a pa icula legi ima e example in Xn. This e ec is symp oma ic
o sophis ica ed manipula ions by which he me e is slowed down egu-
la ly in sho ime in e als (e.g. by ins alling a ci cui inside he de ice)
o hal he eco ding p ocess and unde - egis e he ene gy consumed by
he cus ome . Clea ly, in his case he model should ou pu ℓn
d′= 1 de-
pending on he a io σ∈(0,1] be ween he o e all ene gy o he es ace
and ha o he legi ima e consump ion ace om whe e i was p oduced.
4. Me e ampe ing, by which he me e is delibe a ely bypassed so ha he
de ice does no eco d any consump ion a all. As a esul , ab up ene gy
losses a e ob ained in he da a aces o he cus ome , which eme ge in he
da a ace o he day in which he ampe ing was pe o med as a se ies
o Zmax ze o- alued samples. The model should p edic ℓn
d′= 1 o his
e en , and igge a subsequen manual inspec ion o e he use a hand.
A good ou lie de ec ion model should ake in o accoun ha he goal
o he applica ion is o co ec ly p edic es aces alling wi hin any o
he abo e 4 ca ego ies. The e o e, he design goal can be o mula ed as a
mul i-objec i e op imiza ion p oblem whe e he op imali y o he sough se
o model pa ame e s is d i en by he ade-o be ween wo con lic ing objec-
i es: he a io o con i med ou lie s (TPR) and he p opo ion o co ec ly
iden i ied inlie s (TNR) when he model p edic s a es se composed by D′
7
new consump ion aces. Ma hema ically:
θop = a g
θhmax TNR Mn
θ({Xn
d′}D′
d′=1;Xn),max TPR Mn
θ({Xn
d′}D′
d′=1;Xn)i,
subjec o Xn
d′∼ { 0,X
X(x), 0,δ
X(x), 1,σ
X(x), 1,z
X(x)} ∀d′∈ {1, . . . , D′}, whe ein
by a sligh abuse in no a ion we disc imina e he pa icula hypo heses ha
each dis ibu ion models: no mal beha io ( 0,X
X(x)), shape-p ese ing ime
a iabili y ( 0,δ
X(x)), sub le loss ( 1,σ
X(x)) o ampe ing ( 1,z
X(x)). In essence:
we pu sue he bes model con igu a ion o de ec all classes o inlie and
ou lie aces in he es se , based on he ace se Xn o use n.
The abo e op imiza ion p oblem models he concep ual, s anda d model
adjus men p ocess in da a mining, which can be ackled by using di e en
well-known me hodologies such as c oss- alida ion [35]. Howe e , he design
challenge goes beyond he nume ical e inemen o he pa ame e s con olling
he lea ning p ocess o he model i sel . Since a design a ge is o accom-
moda e ime shi s in he load cu e ha a e no symp oma ic o NTL, we
op o dis ance-based ou lie de ec o s ha le e age a simila i y me ic be-
ween ime dis ances ha is no a ec ed by such non-linea a ia ions. Two
di e en ou lie de ec ion schemes will be designed based on his simila i y
measu emen , compu ed no o e he o iginal da a aces, bu a he on hei
quan ized alues based on he hou ly s a is ics o Xn. The nex sec ion del es
in o he de ails o hese models, along wi h he u ilized simila i y dis ance
and he s a is ical quan iza ion.
3. P oposed App oach
Figu e 2 shows he o e all p ocessing low o he ou lie de ec ion me hods
p oposed in his manusc ip . Fou a e he ing edien s ha lie a he co e o
he de eloped echniques, which a e desc ibed as ollows:
3.1. Simila i y Measu e
As a gued in he p e ious sec ion, a elas ic measu e o simila i y be ween
load p o iles will be used o accommoda e beha io al changes ha do no
imply a dec ease in he ene gy consumed by he moni o ed use (e.g. ime
wa ps). To his end we will emb ace he so-called Dynamic Time Wa ping
(DTW) measu e, by which he simila i y be ween wo any gi en consump ion
aces Xn
dand Xn
d′(i.e. aces eco ded o use na days dand d′) can be
8
compu ed by sea ching o a minimum-weigh op imal pa h Pbe ween he
(1,1) and (N, N) e ices o a ec angula N×Ng id. The weigh wi,j
associa ed o e ex (i, j) in his g id co espond o he Euclidean dis ance
be ween Xn
d,i (i.e. he consump ion measu ed o use n, day dand hou i)
and Xn
d′,j, namely, wi,j =
Xn
d,i −Xn
d′,j
. The DTW me ic be ween aces o
use nco esponding o day dand d′is gi en by [33, 36]
DTW(Xn
d,Xn
d′) = min
P∈P
KP
X
k=1
wpk=
KP
X
k=1
wik,jk,(1)
wi h P={p1,p2,...,pKP}deno ing a KP-long wa ping pa h composed by
s eps pk= (ik, jk) (k∈ {1, . . . , KP}), and Pdeno ing he se o all pa hs
h ough he g id ul illing p1= (1,1), pk−pk−1∈ {(1,1),(0,1),(1,0)}and
pKP= (N, N).
When con ex ualized on he ene gy applica ion ackled in his manusc ip ,
he DTW me ic allows measu ing he deg ee o dissimila i y be ween wo
consump ion aces by dismissing small beha io al shi s o e he ime do-
main and hence ocusing s ic ly on di e ences in he ampli ude o he en-
e gy consumed by he cus ome a hand. The DTW algo i hm p o ides an
adap ed me ic o assess he simila i y be ween wo empo al sequences which
may a y in speed. A pa e n in e ms o he daily elec ic consump ion mus
be lexible enough o cope wi h ime de o ma ions esul ing om i egula
house habi s o di e en wo king schedules. The e o e, a conc e e consump-
ion pa e n does no necessa ily co espond o a unique ea u e ec o in
e ms o bo h sequence modula ion and pe iodici y – hus conside ing a con-
s an window spacing and a poin - o-poin de ini ion – bu a he o a shape
o a silhoue e in a highe -le el o abs ac ion ha allows s e ching o com-
p essing sec ions o he se ies o compa ison. In his wo k we pos ula e ha
he DTW p ope ly deals wi h such an assump ion on he simila i y be ween
wo consump ion aces unde a mo e elas ic conside a ion o alignmen .
3.2. S a is ical T ace Encoding
An op ional ace encoding s a egy is p oposed based on he s a is ical
anges spanned by he hou ly measu emen s egis e ed o he use a hand.
When compu ing he DTW me ic wo dis inc s a egies can be adop ed:
he i s hinges on compu ing he simila i y be ween da a ins ances Xn
dand
Xn
d′by using di ec ly he nume ical alues o he hou ly ene gy consumed
by he use a hand. Howe e , he s aigh o wa d use o unp ocessed alues
9
Q1: Do all encoding-model combina ions (i.e. LOF,LSA,LOF-box,LSA-box)
pe o m easonably well wi h espec o he a ge ed casuis y o NTL
e en s? Which domina es? In e ms o which me ic? (TNR/TPR)
Q2: When op ing o encoding aces based on hei s a is ical bounda ies
(LOF-box,LSA-box), does i yield an enhanced obus ness agains alse
posi i es? (i.e. a highe alue o TNR). Wha is he downside in e u n?
Q3: How a e misclassi ied aces dis ibu ed o e he di e en pa s com-
p ising he es da ase ? Is he e any link o he egula i y o he use ?
Q4: Is he e any chance o inc easing he pe o mance sco es in a p ac ical
implemen a ion o his scheme?
To his end mac oscopic pe o mance sco e s a is ics ha e been compu ed
based on he esul s ob ained o e a e a p e ious da a cleansing s age com-
p ising co up ed da a disca ding. The pa ame e g id {θ1,...,θϑ},o e
which models o e e y disco e ed clus e we e e ined ia c oss- alida ion,
a e, o LOF,{1,2,...,20} × {0,0.1,...,1.9,2}, whe e he i s e m co e-
sponds o he numbe o neighbo s and he second one s ands o he de-
cision h eshold γn,LOF
c. As o models based on LSA, he pa ame e g id is
{0,0.1,...,0.9,1} × {0,0.1,...,0.9,1} × {0.5}, co esponding o ρn
c,τn
cand
γn,LSA
c o alle ia ing he compu a ional complexi y o he c oss- alida ion
p ocess. To his end he ke nel es ima ion wi hin LSA-based app oaches was
u he es ained o a maximum o 50 poin s ins ead o eso ing o he
whole aining se o he clus e a hand. Those ep esen a i e poin s can be
emula ed by he min(|Dn
c|,50) medoids compu ed by a hie a chical clus e -
ing model, whe e we ecall ha |Dn
c|is aken as he numbe o samples he
aining se o he clus e c. The numbe o olds is F= 10 in all cases.
As p e iously s a ed in Algo i hm 1, he i ness unc ion quan i ying he
op imali y o a pa ame e se du ing he clus e -wise c oss- alida ion p ocess
is max{min{TNR,TPR}} o bo h LOF and LSA app oaches. This combined
me ic p e en s any o he in ol ed me ics om becoming domina ed by
he o he , hence o cing he model o achie e a high sco e in one o he wo
pu sued c i e ia o he de imen o he o he .
4.1. Resul s and Discussion
In esponse o Q1, we begin ou discussion by analyzing Figu e 4, which
depic s a sca e plo comp ising he es TNR/TPR sco es a ained by he
p oposed me hods o e e y use in he da ase . Also a e included in he
16

plo i ed Gaussian dis ibu ions o e e y sco e and echnique ia Ke nel
densi y es ima ion wi h a bandwid h pa ame e equal o 1 in all cases. A
i s look on he esul s plo ed in his igu e e eals ha indeed bo h LSA
and LOF bene i om he op ional s a is ical encoding app oach (Subsec ion
3.2) when he ocus is placed on maximizing he numbe o ue nega i e
sco es. This is specially no able in he case o LOF, whe e he a e age TNR
inc eases om 0.62 (LOF) o 0.77 (LOF-box). This, as expec ed, comes along
wi h a se e e penal y in he numbe o de ec ed posi i es, wi h a dec ease
in a e age TPR om 0.70 (LOF) o 0.36 (LOF-box). This pa icula esul
e inces he ade-o be ween bo h sco es, o which he inclusion o algo i h-
mic design op ions as he s a is ical encoding scheme is c ucial o achie e
pe o mance sco es aligned wi h he ope a ional equi emen s. Fo ins ance,
he ope a o migh conse a i ely p io i ize a low numbe o alse posi i es
due o in e nal budge a y/ esou ce cons ain s o inspec ion asks, hence
op ing o he a o emen ioned encoding scheme.
Compa isons be ween echniques can be be e analyzed by ed awing he
esul s in Figu e 4 as a se ies o iolin plo s, i.e. an enhanced e sion o he
con en ional boxplo wi h ex ended in o ma ion abou he shape o a ke nel
dis ibu ion i ed o he da a samples. Such plo s a e p o ided in Figu e 5
along wi h con en ional boxplo s o e laid o e each case. In ligh o hese
esul s and linking o ques ion Q2, i can be in e ed ha he nai e LOF and
LSA schemes in gene al ou pe o m hei s a is ically encoded coun e pa s in
e ms o ou lie de ec ion (TPR), since hey essen ially yield a ine-g ained
adjus ed model capable o disc imina ing sligh de ia ions om he egula
consump ion pa e ns o he use . Howe e , o use s wi h mo e chao ic o
uns eady pa e ns he pa ame e sea ch p ocedu e o he o e all model ails o
ind a p ope balance be ween sensi i i y (TPR) and speci ici y (TNR). Due
o he ac ha a po ion o he alida ion se (and acco dingly ano he pa
o he es se ) is p oduced by emula ing mino luc ua ions in legi ima e
consump ion aces, he new da a aces a e likely o all in high-densi y
egions al eady popula ed by legi ima e use aces, hence being e en ually
in easible o d aw bounda ies o bina y classi ica ion. A his poin i is
in e es ing o ema k ha he LSA-box scheme seems o be mo e esilien
o he TPR deg ada ion expec ed when including he s a is ical encoding
wi hin he ou lie de ec ion low, wi h 70% o he o e all se o analyzed
use s wi h TPR sco es kep abo e 0.6 o his scheme.
The discussion ollows by add essing ques ion Q3; in his ega d, Figu e
6 depic s he dis ibu ion o he accu acy me ic (i.e. he p opo ion o ue
17
es ima ions – bo h posi i e and nega i e – wi h espec o he o al numbe
o samples p ocessed o each use ) o e he di e en pa s in which he
es se is di ided: Region 1 (o iginal legi ima e es aces o he use ),
Region 2 (o iginal aces wi h andom shi s in he ime domain), Region 3
(sub le andom pe u ba ions in he hou ly consump ion alue o he use )
and Region 4 (sha p ze oing o he consump ion ace). Fo he sake o
space and cla i y esul s a e only shown o he LSA and LSA-box schemes.
Expec edly he use o an elas ic measu e o simila i y a he co e o he
classi ie design implies ha he sco e s a is ics be ween Regions 1 and 2
a e simila o each o he , hus e incing ha he o e all model is capable o
accommoda ing occasional beha io al changes in he consump ion habi s o
he use ha o he con en ional simila i y me ics (e.g. pai wise Euclidean
dis ance) would decla e as a alse posi i e. When ocusing on Regions 3 and
4 he ob ained esul s con i m he in ui ion ha sub le a ia ions in Region 3
a e signi ican ly mo e challenging o de ec as ou lie s han he ze oed da a
aces composing Region 4. In e es ingly, accu acy sco es o LSA-box o
Region 4 a e lowe han hose o he nai e LSA scheme, due o he ac ha
small de ia ions may all wi hin he compu ed s a is ical bounda ies d i ing
he ace encoding s a egy o LSA-box. By con as , ze oed samples playing
he ole o mal unc ions in he powe quan i ica ion o ampe ing (namely,
Region 4) a e be e de ec ed by he LSA-box scheme, wi h accu acy sco es
abo e 0.8 o 80% o he o al se o use s in he expe imen al se up.
The a ionale o he di e en pe o mance pa e ns ound be ween ech-
niques o e he egions o he es da a aces can be also unde s ood in
connec ion o he egula i y o he use in his/he ene gy consump ion pa -
e ns. When ansla ing aw alues o he consumed ene gy o a educed ye
s a is ically meaning ul alphabe , he o e all da ase o he use a hand can
be explained mo e likely by a educed se o pa e ns. A byp oduc o his
simpli ica ion is a be e disc imina ion o ou lie s when hey a e cha ac e -
ized by se e e ampli ude d ops, as dis ances become enla ged by i ue o he
ange disc e iza ion o hei median alues. We exempli y his obse a ion in
Figu e 7, which shows a boxplo o he hou ly ene gy measu emen s o wo
di e en use s in he da ase conside ing he DTW alignmen be ween he
da a aces and he a e age consump ion habi o e e y cus ome . As op-
posed o he consump ion i egula i y cha ac e izing Use A, Use B ea u es
ela i ely mo e s able consump ion pa e ns, yielding signi ican ly be e p e-
dic i e sco es han hose ob ained o use A (i.e. a e age TNR/TPR sco es
equal o 0.95/0.93 e sus 0.83/0.58 o LSA-box).
18
We end he discussion by elabo a ing on he implemen a ion o he p o-
posed de ec o s in p ac ice (ques ion Q4). In his con ex i is impo an
o ema k ha sco es so a ha e epo ed o isola ed daily p edic ions, i.e.
TNR/TPR alues co espond o decisions made o e one single day. This,
howe e , lays a an un ealis ic ex eme wi h espec o he p ac ical imple-
men a ion o he p oposed de ec o s, in which he ope a o would en o ce
he inspec ion depa men o in es iga e he equipmen ins alled a ce ain
use ’s p emises only a e a numbe consecu i e posi i es ha e been de ec ed
on his/he da a aces.
A nai e albei insigh ul scheme modeling a mo e ealis ic implemen a ion
hinges on o ing by majo i y a numbe o consecu i e p edic ions o e e y
use . Resul s shown in Figu e 8 o 3 consecu i ely o ed ou comes o he
model bu ess his hypo hesis: p edic i e sco es a e imp o ed no ably by
adop ing his p ac ical app oach o e hose ob ained by he model p edic ing
on an indi idual sample basis (included also in he plo o compa ison).
Rema kably, LSA-box achie es TNR/TPR sco es abo e 0.9 o a leas 75%
o all use s, p omisingly pa ing he way o he deploymen and ope a ion o
his model in eal sma g id scena ios.
5. Concluding Rema ks and Fu u e Resea ch Lines
This manusc ip has elabo a ed on he de ec ion o NTL e en s in ene gy
consump ion p o iles cap u ed by AMIs in Sma G ids. In pa icula we ha e
p oposed a po olio o echniques inco po a ing se e al no el ing edien s o e
he ela ed li e a u e. Fi s , a elas ic measu e o simila i y be ween consump-
ion aces has been adop ed so as o accommoda e he e en ual empo al
a iabili y o he consump ion pa e ns ea u ed by he use unde analysis,
hus en o cing he o e all de ec o o a he ocus on shape pa e ns wi hin
he consump ion aces dis ega ding he ime suppo o e which hey occu .
Second, we ha e de ined an op ional encoding s a egy elying on bounda ies
d i en by he s a is ics o he load cu es o he use , concei ed as a means
o p o ide lexibili y o he o e all de ec o agains mino ampli ude luc u-
a ions and consequen ly, o de ec ue nega i es mo e eliably.
A da a mining low has been buil upon wo di e en dis ance-based lea n-
ing mechanisms (LOF and LSA) ha can be adop ed as i s inne classi ica ion
model, inco po a ing u he elemen s (e.g. dis ance-based clus e ing and
c oss- alida ion) aimed a a p ope cha ac e iza ion o he use in ega ds
o he casuis y o NTL e en s a ge ed in he pape . The combina ion
19
o dis ance-based lea ning algo i hms and he op ionali y o he encoding
s a egy has gi en ise o 4 di e en schemes – namely, LOF,LSA,LOF-box
and LSA-box –, which ha e been desc ibed in de ail h oughou he a icle
and compa ed o each o he o e a da ase comp ising eal da a aces o
a Spanish u ili y company. Resul s ob ained he e om ha e been analyzed
mac oscopically by assessing how each scheme balances he ade-o be ween
sensi i i y and speci ici y when de ec ing emula ed e en s e lec ing di e en
e ec s o NTL e en s in he load cu es. The obse ed pe o mance sco es
o each echnique in he benchma k con i ms he pos ula ed hypo heses:
he use o an elas ic measu e o simila i y be ween ime se ies educes he
a e o alse ala ms due o he e en ual a iabili y o legi ima e consump ion
aces along ime, whe eas he inclusion o an s a is ical encoding app oach
p io o dis ance compu a ion enhances he eliabili y o he de ec o when
p edic ing legi ima e aces (highe ue nega i e a e), a he cos o a de-
g aded disc iminabili y o con i med NTL e en s (lowe ue posi i e a e).
Ne e heless, he ul ima e decision conce ning he selec ion o one model o
ano he (accep ing possibly op imal models and disca ding subop imal ones)
is essen ially a business- ela ed ma e depending on bo h he a ailabili y o
inspec ion esou ces and he in e es o he u ili y company o igge manual
inspec ion campaigns. F equen ly, in eal en i onmen s a misclassi ica ion in-
ol es conside able inspec ion cos s de i ed om checking in si u he easons
o he p edic ed NTL e en , hence u ning he a e o alse ala ms in o he
mos c i ical objec i e. Among he me hods compa ed in ou expe imen s,
LSA-box s ands ou as he one achie ing he bes balance be ween he a e
o ue posi i es and he a e o ue nega i es.
Finally, we ha e p esen ed a mo e p ac ical de ec ion scheme based on
majo i y o ing consecu i e p edic ions o he p oposed NTL de ec ion al-
go i hms, which has been shown o enhance he pe o mance sco es signi i-
can ly o all echniques in he benchma k, wi h alues abo e 0.9 o 75% o
he use s o LSA-box wi h jus h ee o es in he decision. This las esul is
specially encou aging o he p ac ical deploymen and ope a ion o he p o-
posed scheme, o which esea ch e o s will be in es ed in he nea u u e.
O he aspec in he esea ch agenda ela ed o his wo k will g a i a e on he
alle ia ion o he compu a ional complexi y cha ac e izing he clus e -wise
pa ame e se ing by selec ing he clus e samples o e which models a e sub-
sequen ly ained and op imized. P ac ical policies o pe iodically eschedule
he o e all de ec o based on he p edic ion accu acy s a is ics and he eed-
back om inspec ion campaigns will be in es iga ed. The applicabili y o he
20
p oposed me hod o o he ene gy- ela ed scena ios (e.g. sub-me e ing, use
p o iling, demand-side managemen ) will be also examined.
Acknowledgmen s
This wo k has been pa ially suppo ed by he Basque Go e nmen unde
he ELKARTEK p og am (BID3ABI p ojec , g an e . KK-2015/0000080),
as well as by he Spanish Minis e io de Ene g´ıa y Compe i i idad unde he
RETOS p og am (OSIRIS p ojec , g an e . RTC-2014-1556-3).
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25
LOF LSA LOF-box LSA-box
Technique
0.0
0.2
0.4
0.6
0.8
1.0
Value
TNR
TPR
Figu e 5: Violin plo o he TNR-TPR s a is ics o e e y echnique in he benchma k.
The LOF-box is se e ely a ec ed by he s a is ical ace encoding s a egy, wi h he Pa e o
be ween TNR and TPR se e ely unbalanced in a o o he la e . By con as , TNR s a s
o LSA-box enhance sligh ly, ye keeping he TPR sco e s ill a admissible le els.
32

Figu e 6: Dis ibu ion o e o s in e e y egion o he da ase o LSA- aw and LSA-box:
egion 1 co esponds o o iginal da a aces ha should be labeled as inlie s, simila ly o
hose in egion 2 whe e o iginal da a aces a e wa ped along ime o a maximum shi
o ∆max = 4 hou s. Regions 3 and 4 should be decla ed as ou lie s since hey emula e
sha p (ze oing, as could happen in ampe ing) and sub le (small dec eases o he eco ded
ene gy) NTL e en s, espec i ely. Expec edly, sco es a e signi ican ly lowe in egion 3,
whe e he e ec NTL e en is less se e e o e he es da a han in he es o egions.
33
Figu e 7: Hou ly boxplo exempli ying he egula i y and i egula i y o wo consume s
in wha ega ds o his/he ene gy consump ion habi s. Da a samples used o compu ing
he boxplo a hou h∈ {0,1,...,23}a e composed by hose hou ly measu emen s along
Xn(wi h n∈ {A, B}) ma ched, ia DTW alignmen , o he h- h hou o he a e age
consump ion habi o he cus ome (compu ed o e Xn).
34
Figu e 8: Boxplo s co esponding o he TNR/TPR sco es ob ained o each echnique ( e-
ie ed om Figu e 5), and hose sco ed by o ing by majo i y h ee consecu i e ou comes
o he model.
35