TheImpactofPublic Lighting onVoltage Distortion inLow-Voltage Distribution Systems

Portable protective airgaps(PPAG) maybeusedasa liveline tool tocontrol themaximumvoltage that canelectrically stress theairgapataworksite. Theworker's minimumapproach distance (MAD)maybereduced toawithstand distance coordinated withthe sparkover voltage ofthePPAG.PPAGsarecurrently limited toappli- cations at230through 500kV.Thefactors affecting thedesign andper- formance ofPPAGsareprovided. Thedesign dimensions and sparkover characteristics ofseveral PPAGsarediscussed. Workrules foruseofPPAGs, based onfield experience, areprovided. Metropolitana SpA Abstract: Harmonic distortion hasbecome amainconceminelec- tric distribution systems during thelast years. Several public utilities areexperiencing harmonic problems ontheir networks andsomeof themstarted tomonitor thesituation oftheMV andLVdistribution net- works. Recently, theoperation oftheMV andLVnetworks oftheAEM -Torino (the city utility) havebeeninvestigated withseveral on-site measurements. Thesurvey ledtotheobservation ofastep increase in voltage distortion onLV feeders whenthecity street lighting is switched onand, vice versa, asudden decrease whenitisswitched off. Thisphenomenon canbemainly traced backtotheresonance, under certain conditions, between thecapacitance ofthecapacitors fortheim- provement ofthelamps' powerfactor andtheinductance ofthe MV/LVtransformer. Thisworkinvestigates thephenomenon both fromatheoretical point andwithlaboratory andfield tests. Somepossi- bleremedies andtheir practical implementation toreduce harmonic distortion arediscussed.