The importance of resistance in the context of critical infrastructure resilience: An extension of the CIERA method

Ci a ion: Rehak, D.; Flynno a, L.; H omada, M.; Fuggini, C. The Impo ance o Resis ance in he Con ex o C i ical In as uc u e Resilience: An Ex ension o he CIERA Me hod. Sys ems 2023,11, 506. h ps:// doi.o g/10.3390/sys ems11100506 Academic Edi o s: Randy Buchanan and G ego y S. Pa nell Recei ed: 3 Sep embe 2023 Re ised: 27 Sep embe 2023 Accep ed: 29 Sep embe 2023 Published: 8 Oc obe 2023 Copy igh : © 2023 by he au ho s. Licensee MDPI, Basel, Swi ze land. This a icle is an open access a icle dis ibu ed unde he e ms and condi ions o he C ea i e Commons A ibu ion (CC BY) license (h ps:// c ea i ecommons.o g/licenses/by/ 4.0/). sys ems A icle The Impo ance o Resis ance in he Con ex o C i ical In as uc u e Resilience: An Ex ension o he CIERA Me hod Da id Rehak 1,* , Lucie Flynno a 1, Ma in H omada 2and Clemen e Fuggini 3 1Facul y o Sa e y Enginee ing, VSB—Technical Uni e si y o Os a a, 700 30 Os a a, Czech Republic; [email p o ec ed] 2 Facul y o Applied In o ma ics, Tomas Ba a Uni e si y in Zlin, 760 05 Zlin, Czech Republic; h [email p o ec ed] 3Rina Consul ing S.p.A., 20123 Milano, I aly; [email p o ec ed] *Co espondence: da id. [email p o ec ed]; Tel.: +420-597-322-816 Abs ac : Technical sec o s compose an insepa able and elemen a y pa o a complex c i ical in as- uc u e (CI) sys em. Thei p o ided se ices a e essen ial o he unc ioning o all o he dependen sec o s o CI on which socie y and s a es depend, especially in a eas expe iencing high le els o u banisa ion. The ini ial poin o e ec i e CI elemen s’ p o ec ion is he pe manen assessmen and s eng hening o hei capaci y o esilience o he nega i e e ec s o in e nal and ex e nal h ea s. The cu en pe cep ions o esilience ocus p ima ily on ep essi e componen s esponsi e o inciden s (i.e., obus ness, eco e abili y, and adap abili y), while minimal a en ion is paid o he p e en a i e componen s. The a icle’s con ibu ion o his li e a u e gap is i s de ini ion o esis ance, which can be conside ed as a CI elemen ’s abili y o p e en he occu ence o inciden s. To his goal, he cu en s udy de ines (1) he indi idual ac o s ( a iables and pa ame e s) de e mining CI esis ance and (2) he me hodological p ocedu e o in as uc u e elemen esis ance assessmen in o de o iden i y he weak poin s h oughou a complex CI sys em and subsequen ly s eng hen hem. Mo eo e , a p ac ical example o esis ance assessmen o a selec ed c i ical ene gy in as uc u e elemen is p esen ed. The main ou come o his a icle is he de ini ion o he p ima y s eps o he expansion o he CIERA me hod, ia he enhancemen o CI componen s’ esilience capaci y in he p e en ion phase. Keywo ds: esis ance; physical esis ance; c isis p epa edness; an icipa ion abili y; secu i y measu es; c i ical in as uc u e esilience 1. In oduc ion The e m esilience was i s ly in oduced by Holling [ 1 ] in 1973 wi hin an ecology con ex as “a measu e o he pe sis ence o sys ems and o hei abili y o abso b change and dis u bance and s ill main ain he same ela ionships be ween popula ions o s a e a iables”, and was o iginally p oposed as a o mula ion o sys ems which can be cha ac e ized as ecological. Howe e , he concep o esilience has s a ed o be e lec ed o e ime in o he scien i ic a eas, oo, such as psychology, economics, and sociology. I was, he e o e, a easonable consequence ha esilience as a concep would be ecognized o i s easibili y and added alue in echnically o ien ed social ields as well. CI esilience was i s ly de ined in 2009 in he C i ical In as uc u e Resilience Final Repo and Recommenda ions [ 2 ], and wi hin his con ex , is pe cei ed as “ he abili y o abso b, adap o, and/o apidly eco e om a po en ially dis up i e e en ”. Based on his de ini ion, h ee key componen s (i.e., obus ness, eco e abili y, and adap abili y) ha e been iden i ied in [ 2 ] in o de o de e mine esilience. Al hough hese componen s a e key de e minan s o esilience, a mo e ho ough in es iga ion e eals ha hey only ha e a esponsi e cha ac e , as hei impac on CI esilience is only appa en a he ime o he inciden [ 2 ]. This obse a ion leads o he assump ion ha he e is no p e en a i e Sys ems 2023,11, 506. h ps://doi.o g/10.3390/sys ems11100506 h ps://www.mdpi.com/jou nal/sys ems Sys ems 2023,11, 506 2 o 15 componen in he p ocess o esilience building; he e o e, his ole could be suppo ed by esis ance, which can be pe cei ed as he CI abili y o p e en he inciden occu ing. The B i annica Dic iona y [ 3 ] de ines esis ance as he abili y o p e en some hing om ha ing an e ec . The e m esis ance is used by au ho s wi hin a ious and b oade scien i ic ields, e.g., in medicine, o e e o an ibac e ial esis ance o an ibio ics [ 4 , 5 ], o in sociology o e e o he mani es a ion o social esis ance [ 6 , 7 ]. The adap a ion and in eg a ion o he esis ance concep in o enginee ing p ac ice we e in luenced by he ecology ield, whe e he e m was i s ly in oduced in ela ion o esilience by Sugden [ 8 ] and in connec ion wi h alpine lake ecosys ems. The au ho de ined he main logical di e ences be ween esis ance and esilience. He sees esis ance as a measu e o how much an ecosys em is able o wi hs and a dis u bance such as he in oduc ion o an alien species. Resilience was hen conside ed as a esponse and eco e y measu e o he ecosys em a e elimina ing he sou ce o he change. O e he las decade, CI esilience issues ha e been analysed by se e al au ho s. Some s udies deal mo e gene ally wi h he impo ance o esis ance in he con ex o CI esilience [ 9 – 12 ], while o he publica ions ha e al eady de ined he p e en i e ac o s o esilience and poin o he necessi y o hei sepa a ion om obus ness [ 13 – 16 ]. Howe e , he e a e se e al amewo ks which ha e al eady de ined and e alua ed he esis ance a iables when assessing he le el o CI esilience [ 17 – 19 ]. Unde his scope, esis ance can be pe cei ed as an impo an componen o esilience, which should be de ined and de e mined h ough basic ac o s. Rega ding he abo e p esen ed landscape, he added alue o his a icle is o de ine CI esis ance and o desc ibe i s in eg a ion and implemen a ion wi hin he es ablished CIERA me hod [ 20 ]. The mos c ucial pa o his a icle includes he exp ession o indi idual CI esis ance ac o s and he me hodological p ocedu e o hei assessmen wi h he ambi ion o s eng hen he esis ance o hese CI sys ems. The e o e, his s udy con ibu es signi ican ly o he de ini ion o a comp ehensi e concep o CI sys ems esilience. 2. Ma e ials and Me hods The cu en s udy a emp s o p o e he sui abili y o in eg a ing esis ance in o esilience, hence he de ini ion o esilience and i s meaning o a CI sys em a e equi ed in he ini ial phase. The o igin o he wo d esilience is oo ed in he La in language, and i is ound as esilie e, which li e ally ansla es as bounce back [ 21 ]. Resilience wi hin he con ex o CI i s ly appea ed in 2009 [ 2 ], bu his de ini ion was expanded in 2012 by he US Na ional Academies o Science in o de o include p epa a ion and planning and was exp essed as “ he sys em’s abili y o p epa e and plan o , abso b, eco e om, and success ully adap o dis up i e e en s” [ 22 ]. Since hen, he e has been no essen ial change in he pe cep ion o CI esilience, which is also illus a ed by he de ini ions o CI esilience gi en in se e al impo an publica ions wi hin his pe iod [ 11 , 23 – 29 ]. All o he de ini ions ound in hese s udies a e o ien ed owa ds he so-called echnical esilience, which e e s o c i ical in as uc u e elemen s (CIEs) and is exp essed by hei abso p ion capaci y and hei abili y o eco e and adap o inciden s ha ha e occu ed. Howe e , a sligh shi in he conside a ion o CI sys em esilience occu ed in 2022, when he Eu opean Union issued a espec i e Di ec i e which has ocused on he esilience o c i ical en i ies [ 30 ]. Resilience wi hin his con ex is conside ed as “a c i ical en i y’s abili y o p e en , p o ec agains , espond o, esis , mi iga e, abso b, accommoda e and eco e om an inciden ”. This de ini ion is e iden ly spo ligh ing and p omo ing he o ganisa ional esilience, aiming a inc easing he esilience o he en i ies which a e esponsible o hese CIEs [31]. F om he summa y and collec ion o he abo e-men ioned de ini ions, i can be s a ed ha CI esilience consis s o ou phases, which oge he o m he so-called CI esilience cycle [ 32 ] and i s signi icance is he e e -inc easing CIE p o ec ion. E en hough esilience is enhanced especially in he adap a ion phase o an inciden ha has occu ed, he inc ease in esilience can be no iced e en om he eco e y phase in some cases (e.g., by adop ing and ins alling a comple ely new and mo e esilien echnology). Sys ems 2023,11, 506 3 o 15 The ini ial phase o he CI esilience cycle is p e en ion, and i s impo ance lies in p e en ing he occu ence o an inciden because o i s po en ial h ea o impac on a CIE. These measu es aim a he ea ly de ec ion o an inciden and he elemen ’s p epa edness o i s impac . When an inciden occu s, hen he esilience cycle mo es in o he abso p ion phase. The essence o his phase is o abso b he inciden ’s e ec s on he CIE. The elemen ’s abili y o abso b he inciden ’s e ec s is e e ed o as obus ness. A e he comple ion o he inciden , esilience mo es in o he eco e y phase. The signi icance o his phase is o mi iga e he consequences o he inciden ’s impac on he CIE and es o e i s pe o mance o i s ini ial le el. Adap a ion is he inal s age o he CI esilience cycle and e e s o he impo ance o he CIE’s adap a ion o he occu ed inciden , s eng hening he eby he elemen ’s o e all esilience capaci y. CI esilience is cu en ly de e mined by h ee componen s, as also men ioned in he in oduc ion, bu hese cha ac e ise only h ee o he abo e phases (i.e., abso p ion, eco e y, and adap a ion), since he p e en ion phase is no ye conside ed among he componen s. Howe e , and be o e mo ing o he de ini ion o he componen in he p e en ion phase, i is app op ia e o p esen he componen s in he exis ing h ee phases o esilience [2]: • obus ness is “ he abili y o he sys em o abso b he e ec s o a dis up ion wi hou signi ican de ia ion om no mal ope a ing pe o mance”; • eco e abili y is “ he abili y o he sys em o eco e quickly om po en ially dis up i e e en s”; • adap abili y is “ he abili y o he sys em o adap o a shock o no mal ope a ing condi ions”. Resea ch on hese h ee speci ic componen s has been conduc ed in he pas by a numbe o epu able au ho s [ 32 – 39 ]. A e a de ailed analysis o hese publica ions, a iables de e mining he CIE esilience componen s we e de ined (Figu e 1) as pa o he CIERA me hod’s de elopmen [20]. Sys ems2023,11,xFORPEERREVIEW3o 15   inc easein esiliencecanbeno icede en om he eco e yphaseinsomecases(e.g.,by adop ingandins allingacomple elynewandmo e esilien  echnology). Theini ialphaseo  heCI esiliencecycleisp e en ion,andi simpo anceliesin p e en ing heoccu enceo aninciden becauseo i spo en ial h ea o impac onaCIE. Thesemeasu esaima  heea lyde ec iono aninciden and heelemen ’sp epa edness o i simpac .Whenaninciden occu s, hen he esiliencecyclemo esin o heabso p ion phase.Theessenceo  hisphaseis oabso b heinciden ’seffec son heCIE.Theelemen ʹs abili y oabso b heinciden ʹseffec sis e e ed oas obus ness.A e  hecomple iono  heinciden , esiliencemo esin o he eco e yphase.Thesigni icanceo  hisphaseis o mi iga e heconsequenceso  heinciden ’simpac on heCIEand es o ei spe o mance oi sini ialle el.Adap a ionis he inals ageo  heCI esiliencecycleand e e s o he impo anceo  heCIEʹsadap a ion o heoccu edinciden ,s eng hening he eby he elemen ’so e all esiliencecapaci y. CI esilienceiscu en lyde e minedby h eecomponen s,asalsomen ionedin he in oduc ion,bu  hesecha ac e iseonly h eeo  heabo ephases(i.e.,abso p ion, eco - e y,andadap a ion),since hep e en ionphaseisno ye conside edamong hecompo- nen s.Howe e ,andbe o emo ing o hede ini iono  hecomponen in hep e en ion phase,i isapp op ia e op esen  hecomponen sin heexis ing h eephaseso  esilience [2]:  obus nessis“ heabili yo  hesys em oabso b heeffec so adis up ionwi hou signi i- can de ia ion omno malope a ingpe o mance”;  eco e abili yis“ heabili yo  hesys em o eco e quickly ompo en iallydis up i e e en s”;  adap abili yis“ heabili yo  hesys em oadap  oashock ono malope a ingcondi ions”. Resea chon hese h eespeci iccomponen shasbeenconduc edin hepas bya numbe o  epu ableau ho s[32–39].A e ade ailedanalysiso  hesepublica ions, a i- ablesde e mining heCIE esiliencecomponen swe ede ined(Figu e1)aspa o  he CIERAme hod’sde elopmen [20].  Figu e1.Va iablesde e miningCIE esiliencecomponen s[20]. Figu e 1. Va iables de e mining CIE esilience componen s [20]. Based on he abo e, i can be concluded ha he e is cu en ly no cha ac e is ic componen o exp ess he i s esilience phase (i.e., p e en ion). This componen could be conside ed he esis ance, which in he con ex o ecology ( om which he whole esilience concep ini ia ed) is ound as he abili y o an ecosys em o p o ec i sel agains a pe u ba ion [8]. Sys ems 2023,11, 506 4 o 15 3. Resul s The ollowing ex is a key pa o he a icle, as he au ho s p esen he e he esul s o hei o iginal esea ch. These esul s e e mainly o he de ini ions o (1) CI esis ance, (2) he ac o s de e mining his esis ance, and (3) a me hodological p ocedu e o assessing hese ac o s in o de o s eng hen CIE esis ance. The e m esis ance was coined by Leona do da Vinci in The Mad id Codices I–II [ 40 ] in o de o desc ibe he esis ance o wa e and ai o mo ing solid bodies, as well as o wa e and i e mo ing in ai . An impo an de ini ion o esis ance was elabo a ed om Geo g Ohm la e , in 1827, and i was in ela ion o he di icul y o passing an elec ic cu en h ough a subs ance [ 41 ]. Ano he use o he e m esis ance was eco ded in 1862, in he sense o o ganised opposi ion o an in ade [ 42 ]. In he ollowing pe iod, he e m was inc easingly used in a mili a y-poli ical con ex o e e o unde g ound esis ance mo emen s in any coun y. O e ime, he e m esis ance has been inse ed in o he ocabula y and p ac ice o a ious o he scien i ic ields, such as medicine (e.g., an ibio ic o an imic obial esis ance, immune esis ance, psychological esis ance), ecology (e.g., ecological o en i onmen al esis ance, pes icide esis ance) o economics (e.g., esis ance economy). In he con ex o he cu en s udy, which is CI sys emic esilience, he e m esis ance has no ye been de ined. Some au ho s conside esis ance and esilience as wo dis inc concep s [ 43 ], unde s anding esis ance as being simila o p e en ing o p o ec ing, while esilience as akin o esponding o eco e ing. O he au ho s include he wo e ms in he same con ex bu conside esis ance as a componen o esilience esponsible o educing he se e i y o consequences o a haza d [ 33 ]. In bo h cases, i can be s a ed ha his in e p e a ion is inaccu a e, as esis ance in all o he abo e men ioned ields is a ac o p e en ing he eme gence o an inciden . I is hus a undamen al componen o esilience ha has a clea ly p e en a i e bu no mi iga ing cha ac e . Taking in o accoun hese conside a ions, he au ho s o his a icle ha e c ea ed a de ini ion whe e hey iew esis ance as “ he c i ical in as uc u e abili y o p e en he occu ence o an inciden ”. In his con ex , i is app op ia e o d aw a en ion o he ac ha his capaci y o esis ance minimizes he ansmission o he inciden consequences o dependen CI sec o s, he eby p e en ing he occu ence o cascading and syne gis ic e ec s [ 44 ]. Based on he abo e, i is easible o de ine esis ance wi hin he CI esilience con ex and, as a consequence, his esis ance is o be seen as one o he essen ial esilience componen s, especially in i s ini ial phase. O he esilience componen s a e obus ness, eco e abili y, and adap abili y. The au ho s’ pe cep ions o hese componen s ega ding an inciden a e p esen ed in Figu e 2. In he ollowing pa o he a icle and wi h e e ence o Figu e 1, he de ini ion o he a iables de e mining CIE esis ance is easible (Figu e 3). I is e iden om he abo e de ini ion o esis ance ha he signi icance o hese a iables mus be hei abili y o p e en inciden s. Fo his scope, all o hese a iables mus be o a p e en a i e cha ac e . The de aul a iable is c isis p epa edness. The essence o c isis p epa edness is o inc ease he eadiness o CI en i ies and hei in as uc u es agains disas e s [ 45 ]. This p epa edness consis s in a ho ough assessmen o isks and he subsequen p ocessing o secu i y planning documen a ion. Risk assessmen is conside ed a sys ema ic and e ec i e way o iden i ying, analysing, and e alua ing isks and de e mining he mos e ec i e cos s and means o minimize hese isks [ 46 ]. Fo his pu pose, i is ad isable o use he ecommended isk assessmen echniques [ 47 ]. Secu i y planning documen a ion speci ically includes eme gency plans and a CI en i y’s c isis p epa edness plan [ 48 ]. An eme gency plan is a documen con aining a comp ehensi e se o p e en i e measu es aimed a p epa ing he CI en i y o an acciden o o he inciden , including na u al and man-made h ea s. Fo example, in he Czech Republic, he c isis p epa edness plan se es CI en i ies o ensu e hei own unc ioning du ing disas e s [49]. Sys ems 2023,11, 506 5 o 15 Sys ems2023,11,xFORPEERREVIEW5o 15    Figu e2.Resis ancepe cep ionsin ela ion oCI esilience. In he ollowingpa o  hea icleandwi h e e ence oFigu e1, hede ini iono  he a iablesde e miningCIE esis anceis easible(Figu e3).I ise iden  om heabo e de ini iono  esis ance ha  hesigni icanceo  hese a iablesmus be hei abili y op e- en inciden s.Fo  hisscope,allo  hese a iablesmus beo ap e en a i echa ac e .  Figu e3.De ining a iablesde e mining heCIE’s esis ance. Thede aul  a iableisc isisp epa edness.Theessenceo c isisp epa ednessis o inc ease he eadinesso CIen i iesand hei in as uc u esagains disas e s[45].This p epa ednessconsis sina ho oughassessmen o  isksand hesubsequen p ocessingo  secu i yplanningdocumen a ion.Riskassessmen isconside edasys ema icandeffec- i ewayo iden i ying,analysing,ande alua ing isksandde e mining hemos effec i e cos sandmeans ominimize hese isks[46].Fo  hispu pose,i isad isable ouse he ecommended iskassessmen  echniques[47].Secu i yplanningdocumen a ionspeci i- callyincludeseme gencyplansandaCIen i y’sc isisp epa ednessplan[48].Aneme - gencyplanisadocumen con ainingacomp ehensi ese o p e en i emeasu esaimed a p epa ing heCIen i y o anacciden o o he inciden ,includingna u alandman- made h ea s.Fo example,in heCzechRepublic, hec isisp epa ednessplanse esCI en i ies oensu e hei own unc ioningdu ingdisas e s[49]. Thesecond a iableisan icipa ionabili y.Thesubs anceo  his a iableis heabili y o  heCIen i y op edic  hepossibleinciden eme genceasa esul o  he h ea impac . Thesea ebasically heac i i ieso  heen i yin hecon ex o de ining he isken i on- men  ha affec s heCIE[33].Fo  hispu pose,i ispossible ouseoneo  hea ailable Figu e 2. Resis ance pe cep ions in ela ion o CI esilience. Sys ems2023,11,xFORPEERREVIEW5o 15    Figu e2.Resis ancepe cep ionsin ela ion oCI esilience. In he ollowingpa o  hea icleandwi h e e ence oFigu e1, hede ini iono  he a iablesde e miningCIE esis anceis easible(Figu e3).I ise iden  om heabo e de ini iono  esis ance ha  hesigni icanceo  hese a iablesmus be hei abili y op e- en inciden s.Fo  hisscope,allo  hese a iablesmus beo ap e en a i echa ac e .  Figu e3.De ining a iablesde e mining heCIE’s esis ance. Thede aul  a iableisc isisp epa edness.Theessenceo c isisp epa ednessis o inc ease he eadinesso CIen i iesand hei in as uc u esagains disas e s[45].This p epa ednessconsis sina ho oughassessmen o  isksand hesubsequen p ocessingo  secu i yplanningdocumen a ion.Riskassessmen isconside edasys ema icandeffec- i ewayo iden i ying,analysing,ande alua ing isksandde e mining hemos effec i e cos sandmeans ominimize hese isks[46].Fo  hispu pose,i isad isable ouse he ecommended iskassessmen  echniques[47].Secu i yplanningdocumen a ionspeci i- callyincludeseme gencyplansandaCIen i y’sc isisp epa ednessplan[48].Aneme - gencyplanisadocumen con ainingacomp ehensi ese o p e en i emeasu esaimed a p epa ing heCIen i y o anacciden o o he inciden ,includingna u alandman- made h ea s.Fo example,in heCzechRepublic, hec isisp epa ednessplanse esCI en i ies oensu e hei own unc ioningdu ingdisas e s[49]. Thesecond a iableisan icipa ionabili y.Thesubs anceo  his a iableis heabili y o  heCIen i y op edic  hepossibleinciden eme genceasa esul o  he h ea impac . Thesea ebasically heac i i ieso  heen i yin hecon ex o de ining he isken i on- men  ha affec s heCIE[33].Fo  hispu pose,i ispossible ouseoneo  hea ailable Figu e 3. De ining a iables de e mining he CIE’s esis ance. The second a iable is an icipa ion abili y. The subs ance o his a iable is he abili y o he CI en i y o p edic he possible inciden eme gence as a esul o he h ea impac . These a e basically he ac i i ies o he en i y in he con ex o de ining he isk en i onmen ha a ec s he CIE [ 33 ]. Fo his pu pose, i is possible o use one o he a ailable me hods aimed a indica ing he dis up ion o CIE esilience [ 29 , 50 , 51 ]. On he basis o he possible elemen esilience dis up ion assessmen , p e en i e measu es a e implemen ed o p e en he eme gence o an inciden . O he measu es which can be used o p edic he eme gence o inciden s a e audi s o so wa e applica ions ha enable inciden p edic ion [52,53]. The hi d a iable is physical esis ance. The subs ance o his a iable is he CIE’s abili y o esis he e ec s o na u al and man-made h ea s (e.g., ockslide o uck a ack), h ough he ma e ial and s uc u al esis ance o CI buildings [ 54 ]. The co e a eas o physical esis ance a e i e, seismic and explosion esis ance. Fi e esis ance is he abili y o building s uc u es o wi hs and he e ec s o a ully de eloped i e, wi hou hei load- bea ing capaci y and s abili y, in eg i y and insula ing abili y being pa icula ly a ec ed [ 55 ]. Seismic esis ance is he abili y o building s uc u es o wi hs and he e ec s o ea hquakes h ough su icien elas ici y o duc ili y [ 56 ]. Explosion esis ance is he abili y o buildings o p e en explosions (i.e., ac i e explosion p o ec ion) o o elimina e he e ec s o an explosion (i.e., passi e explosion p o ec ion) h ough hei layou and measu es [57]. Sys ems 2023,11, 506 6 o 15 The las a iable is secu i y measu es. The use ulness o hese measu es is in he moni o ing and physical p o ec ion o CIEs. The goal o moni o ing is mainly o check he echnical condi ion o he elemen s, hei unc ions and he se ices hey p o ide [ 58 ]. I any de iciencies a e iden i ied h ough moni o ing, i is ad isable o s a he p ocess o epai ing o mode nizing hese elemen s. The essence o mode niza ion is especially in main aining he echnical s a e o elemen s wi h cu en ends and echnologies [ 59 ]. A sui able p e en i e ool o CIE p o ec ion is also a physical p o ec ion sys em, which is de e mined by egime, o ganiza ional and echnical measu es [60]. A comp ehensi e o e iew o he a iables and hei pa ame e s desc ibing CIE esilience is p esen ed g aphically in Figu e 4. The s uc u e o his igu e is designed in he o m o a descending classi ica ion, whe e he i s le el consis s o a iables, he second le el consis s o pa ame e s, and he hi d le el ecommends some po en ially sui able c i e ia. Sys ems2023,11,xFORPEERREVIEW6o 15   me hodsaimeda indica ing hedis up iono CIE esilience[29,50,51].On hebasiso  he possibleelemen  esiliencedis up ionassessmen ,p e en i emeasu esa eimplemen ed op e en  heeme genceo aninciden .O he measu eswhichcanbeused op edic  he eme genceo inciden sa eaudi so so wa eapplica ions ha enableinciden p edic ion [52,53]. The hi d a iableisphysical esis ance.Thesubs anceo  his a iableis heCIE’s abili y o esis  heeffec so na u alandman-made h ea s(e.g., ockslideo  ucka ack), h ough hema e ialands uc u al esis anceo CIbuildings[54].Theco ea easo phys- ical esis ancea e i e,seismicandexplosion esis ance.Fi e esis anceis heabili yo  buildings uc u es owi hs and heeffec so a ullyde eloped i e,wi hou  hei load- bea ingcapaci yands abili y,in eg i yandinsula ingabili ybeingpa icula lyaffec ed [55].Seismic esis anceis heabili yo buildings uc u es owi hs and heeffec so ea h- quakes h oughsufficien elas ici yo duc ili y[56].Explosion esis anceis heabili yo  buildings op e en explosions(i.e.,ac i eexplosionp o ec ion)o  oelimina e heeffec s o anexplosion(i.e.,passi eexplosionp o ec ion) h ough hei layou andmeasu es[57]. Thelas  a iableissecu i ymeasu es.Theuse ulnesso  hesemeasu esisin hemon- i o ingandphysicalp o ec iono CIEs.Thegoalo moni o ingismainly ocheck he echnicalcondi iono  heelemen s, hei  unc ionsand hese ices heyp o ide[58].I  anyde icienciesa eiden i ied h oughmoni o ing,i isad isable os a  hep ocesso  epai ingo mode nizing heseelemen s.Theessenceo mode niza ionisespeciallyin main aining he echnicals a eo elemen swi hcu en  endsand echnologies[59].A sui ablep e en i e ool o CIEp o ec ionisalsoaphysicalp o ec ionsys em,whichis de e minedby egime,o ganiza ionaland echnicalmeasu es[60]. Acomp ehensi eo e iewo  he a iablesand hei pa ame e sdesc ibingCIE e- silienceisp esen edg aphicallyinFigu e4.Thes uc u eo  his igu eisdesignedin he o mo adescendingclassi ica ion,whe e he i s le elconsis so  a iables, hesecond le elconsis so pa ame e s,and he hi dle el ecommendssomepo en iallysui able c i e ia.  Figu e4.Va iablesand hei pa ame e sdesc ibing heCIEʹs esis ance. Theabo e-de ined a iablesand hei pa ame e scanbeusedinpa icula  oassess CIE esis ance,e.g., h ough heassessmen mechanismo  hesemi-quan i a i eCIERA me hod[20].Thisme hodissui able o assessing he esilienceo elemen sin echnical Figu e 4. Va iables and hei pa ame e s desc ibing he CIE’s esis ance. The abo e-de ined a iables and hei pa ame e s can be used in pa icula o assess CIE esis ance, e.g., h ough he assessmen mechanism o he semi-quan i a i e CIERA me hod [ 20 ]. This me hod is sui able o assessing he esilience o elemen s in echnical in as uc u es, such as ene gy, anspo , communica ion and in o ma ion sys ems o wa e managemen . Fo his pu pose, i is necessa y o assess all pa ame e s ha de e mine each a iable. These pa ame e s mus be e alua ed agains he speci ic h ea , as he le el o esis ance o he elemen s canno be gene alised. The assessmen can be ca ied ou , simila ly o he CIERA me hod, h ough poin e alua ion, whe e 5 poin s is he bes and 1 poin he wo s . The le el o each esis ance a iable is hen calcula ed by a weigh ed a e age o he indi idual pa ame e s (see Equa ion (1)). Because he pa ame e le el is ep esen ed as a sco e be ween 1 and 5, he esul ing alue mus be mul iplied by 20, which gi es a esul exp essed as a pe cen age. V =20 ∑ s=1 Psws(1) whe e V = he - h CIE esis ance a iable [%]; Ps = he s- h CIE esis ance pa ame e [poin s]; ws = he s- h s anda dised weigh o he s- h CIE esis ance pa ame e in he in e al h0;1i ; = he numbe o pa ame e s in he - h a iable. The s anda dised weigh s Sys ems 2023,11, 506 7 o 15 o he pa ame e s we e de e mined using he pai wise compa ison me hod [ 61 ] and a e p esen ed in Table 1. Table 1. S anda dised weigh s o pa ame e s de e mining esis ance a iables o CIEs. Va iables Pa ame e s and Thei S anda dised Weigh s ∑ C isis p epa edness (V1)Risk assessmen (P1.1) Sa e y planning (P1.2)- w1.1 = 0.4 w1.2 = 0.6 - w1= 1.0 An icipa ion abili y (V2) Dis up ion indica ing p ocedu e o CIE esilience (P2.1) Regula checks and su eys (P2.2)So wa e applica ions o inciden p edic ion (P2.3) w2.1 = 0.4 w2.2 = 0.3 w2.3 = 0.3 w2= 1.0 Physical esis ance (V3)Fi e esis ance (P3.1) Seismic esis ance (P3.2) Explosion esis ance (P3.3) w3.1 = 0.4 w3.2 = 0.3 w3.3 = 0.3 w3= 1.0 Secu i y measu es (V4)Moni o ing (P4.1)Physical p o ec ion sys em (P4.2)- w4.1 = 0.4 w4.2 = 0.6 - w4= 1.0 In his con ex , i is wo h no ing ha he cu en way o calcula ing indi idual a iables does no ake in o accoun he changing na u e o a CI elemen , i.e., whe he i is a poin , a eal o line elemen [ 62 , 63 ]. The esul ing le el o CIE esis ance is exp essed by he weigh ed a e age o he indi idual a iables (see Equa ion (2)): R= ∑ =1 V h (2) whe e R = he CIE esis ance [%]; V = he - h a iable o CIE esis ance [%]; h = he - h s anda dised weigh o he - h a iable o CIE esis ance [ h0;1i ]; = he numbe o a iables exp essing he CIE esis ance. The s anda dised weigh s o he a iables we e exp essed using he pai wise compa ison me hod [61] and a e p esen ed in Table 2. Table 2. S anda dised weigh s o a iables de e mining he esis ance o CIEs. Va iables S anda dised Weigh s C isis p epa edness (V1)h1= 0.2 An icipa ion abili y (V2)h2= 0.25 Physical esis ance (V3)h3= 0.25 Secu i y measu es (V4)h4= 0.3 ∑1.00 A po en ial g aphical ep esen a ion o he esul ing le el o CIE esis ance and i s a iables is p esen ed in Figu e 5. The esul ing le el o CIE esis ance is exp essed as a pe cen age, which in i sel p o ides only a ough idea o he p o ec ion o he elemen . A mo e de ailed e alua ion o his le el is necessa y by classi ying i acco ding o he e e ence scale (Table 3) which is based on he CIERA me hod [20]. Sys ems 2023,11, 506 8 o 15 Sys ems2023,11,xFORPEERREVIEW8o 15   Apo en ialg aphical ep esen a iono  he esul ingle elo CIE esis anceandi s a iablesisp esen edinFigu e5.  Figu e5.Exp essiono CIE esis ancele els. The esul ingle elo CIE esis anceisexp essedasape cen age,whichini sel p o- idesonlya oughideao  hep o ec iono  heelemen .Amo ede ailede alua iono  hisle elisnecessa ybyclassi yingi acco ding o he e e encescale(Table3)whichis basedon heCIERAme hod[20]. Table3.Re e encescale o assessing heCIE esis ancele el[20]. Resis anceLe elso C i icalIn as uc u eElemen s Highle elo  esis ance85–100% Accep ablele elo  esis ance69–84% Lowle elo  esis ance53–68% Insufficien le elo  esis ance37–52% C i icalle elo  esis ance≤36% Theaccep abili yo  esis anceisdi e si iedin o i e a ingle els,andi isd i enby heinc easeddesi e,in hein e es o  heuse s, oexamine hecomposi iono  esis ance inmo ede ail(i.e., o e ospec i elyb eakdown esis ancein oindi idual a iablesand pa ame e s).I  esis ance eachesale elo ≤68%,iden i ica iono weaknessesconsis ing inab eakdowno  he esis anceassessmen  esul sshouldbeca iedou a  hele elo  hepa ame e sconce ned.Fo pa ame e ssco ing2o less,i isnecessa y o e iew he affec eda eao  heassessedelemen ands a  hep ocesso s eng heningi s esis ance. Tos eng hen he esilienceo  hesepa ame e s,i issui able ouse, o example, he ools o s eng heningCIE esilience[64].These oolsshouldbeapp op ia elyimple- men ed os eng henelemen  esis ance h ough he ele an  a iables.Ingene al,i is easible odi ide hese oolsin oex e nalandin e nal oolsand,due o hei na u e,in o hema icg oups.Insomecases, hesea e ools egula ingp ocessand unc ionala easo  o ganiza ionmanagemen (i.e.,pe sonnel, inancialandp ocess ools).Incon a y, he oolsa e ocusedonex e nal ac o s(p incipleo  hePESTLEme hod),conside ingpoli - ical,economic,social,legisla i e, echnological,anden i onmen alaspec s.Toolssui able o s eng hening esis ance a iablesa ep esen edinFigu e6. Figu e 5. Exp ession o CIE esis ance le els. Table 3. Re e ence scale o assessing he CIE esis ance le el [20]. Resis ance Le els o C i ical In as uc u e Elemen s High le el o esis ance 85–100% Accep able le el o esis ance 69–84% Low le el o esis ance 53–68% Insu icien le el o esis ance 37–52% C i ical le el o esis ance ≤36% The accep abili y o esis ance is di e si ied in o i e a ing le els, and i is d i en by he inc eased desi e, in he in e es o he use s, o examine he composi ion o esis ance in mo e de ail (i.e., o e ospec i ely b eak down esis ance in o indi idual a iables and pa ame e s). I esis ance eaches a le el o ≤68%, iden i ica ion o weaknesses consis ing in a b eakdown o he esis ance assessmen esul s should be ca ied ou a he le el o he pa ame e s conce ned. Fo pa ame e s sco ing 2 o less, i is necessa y o e iew he a ec ed a ea o he assessed elemen and s a he p ocess o s eng hening i s esis ance. To s eng hen he esilience o hese pa ame e s, i is sui able o use, o example, he ools o s eng hening CIE esilience [ 64 ]. These ools should be app op ia ely imple- men ed o s eng hen elemen esis ance h ough he ele an a iables. In gene al, i is easible o di ide hese ools in o ex e nal and in e nal ools and, due o hei na u e, in o hema ic g oups. In some cases, hese a e ools egula ing p ocess and unc ional a eas o o ganiza ion managemen (i.e., pe sonnel, inancial and p ocess ools). In con a y, he ools a e ocused on ex e nal ac o s (p inciple o he PESTLE me hod), conside ing poli ical, economic, social, legisla i e, echnological, and en i onmen al aspec s. Tools sui able o s eng hening esis ance a iables a e p esen ed in Figu e 6. Sys ems 2023,11, 506 9 o 15 Sys ems2023,11,xFORPEERREVIEW9o 15    Figu e6.Toolssui able o s eng heningCIE esilience a iables[64]. 4.P ac icalExampleo Resis anceAssessmen  o aSelec edEne gyCIE Finally,i isapp op ia e odemons a e heapplicabili yo  he esul sob ainedin hecu en s udyby hei implemen a ion oaselec edene gyCIE.Theselec edelemen  isanelec icals a iono a ansmissionsys emwhichisaEu opeanCIE.In heCzech Republic, he ea ea o alo 33elec icals a ionsinope a ionin he ansmissionsys em, o which ou s a ionsensu e heconnec ionbe ween he400kVand220kVsys ems,32 s a ionsensu e heconnec ionbe weenTSandDS,10s a ionsensu e heou pu o powe  ompowe plan s,andeigh s a ionsa ecomposedo 400kVand220kVsubs a ions. Theassessedelec icals a ionisanonymized o secu i y easons,andonlyi sbasicde- sc ip ionisp o idedinTable4. Table4.Desc ip iono selec edene gyCIE. Elemen nameT ansmissionsys emelec icals a ion Sec o /subsec o Ene gy/Elec ici y/T ansmission Key echnologies 1.T ans o me s 2.Vol ageins umen  ans o me s 3.Cu en ins umen  ans o me s 4.Compensa ionchokes 5.Disconnec o sandg oundingswi ches 6.Busba sandb anches 7.Ci cui b eake s Elemen pe o mance400/220kV Figu e 6. Tools sui able o s eng hening CIE esilience a iables [64]. 4. P ac ical Example o Resis ance Assessmen o a Selec ed Ene gy CIE Finally, i is app op ia e o demons a e he applicabili y o he esul s ob ained in he cu en s udy by hei implemen a ion o a selec ed ene gy CIE. The selec ed elemen is an elec ical s a ion o a ansmission sys em which is a Eu opean CIE. In he Czech Republic, he e a e a o al o 33 elec ical s a ions in ope a ion in he ansmission sys em, o which ou s a ions ensu e he connec ion be ween he 400 kV and 220 kV sys ems, 32 s a ions ensu e he connec ion be ween TS and DS, 10 s a ions ensu e he ou pu o powe om powe plan s, and eigh s a ions a e composed o 400 kV and 220 kV subs a ions. The assessed elec ical s a ion is anonymized o secu i y easons, and only i s basic desc ip ion is p o ided in Table 4. In he subsequen sec ion, a semi-quan i a i e assessmen o his selec ed elemen ’s esis ance o he selec ed h ea is conduc ed and p esen ed. This h ea is a e o is a ack using an explosi e de ice aimed a physical damage o he con ol wo kplace and causing a widesp ead blackou . The assessmen o he esis ance o he selec ed ene gy CIE is ealised in h ee s eps: •S ep 1: Analysis and sco ing o each pa ame e ; •S ep 2: Calcula ion o he le el o each a iable; •S ep 3: De e mina ion o he esul ing ene gy CIE esis ance le el. S ep 1: The esul s o he analysis, including he poin a ing and i s a ionale o indi idual pa ame e s de e mining he elemen esis ance, a e shown in Table 5.