?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.relation=http%3A%2F%2Fmiis.maths.ox.ac.uk%2Fmiis%2F101%2F&rft.title=Forecasting+triads%3A+the+negative+feedback+problem&rft.creator=Hunt%2C+Robert&rft.creator=Clarke%2C+Liam&rft.creator=Byatt-Smith%2C+John&rft.creator=Billingham%2C+John&rft.subject=Energy+and+utilities&rft.description=At+the+end+of+the+winter+season+(November+1st+to+February+28th)%2C+National+Grid+identifies+the+three+half-hour+periods+of+highest+consumption+of+electricity%2C+subject+to+a+separation+of+at+least+10+calendar+days.+These+three+periods+are+called+Triads.+Thus%2C+the+half-hour+in+which+national+demand+was+highest+is+the+first+Triad%3B+the+second+highest+half-hour%2C+excluding+a+period+of+21+days+centred+on+the+first+Triad%2C+is+the+second+Triad%3B+and+the+third+highest+half-hour%2C+excluding+two+periods+of+21+days+centred+on+the+first+and+second+Triads%2C+is+the+third+Triad.+Historically%2C+Triads+always+occur+on+Mondays+to+Thursdays+between+16%3A30+and+18%3A00+hours%2C+and+not+close+to+Christmas+(which+is+a+period+of+relatively+low+consumption).+Figure+1+shows+the+typical+pattern+over+a+winter.%0A%0AFigure+1%3A+National+electricity+consumption+figures+from+the+winter+of+2003%2F04.+Diamonds+indicate+daily+levels%3B+squares+indicate+dates+on+which+British+Energy+issued+Triad+warnings%3B+and+circles+indicate+those+dates+on+which+a+Triad+was%2C+at+the+end+of+the+winter%2C+declared+to+have+occurred.%0A%0ABritish+Energy+supplies+electricity+to+large+industrial+and+commercial+customers.+Charges+are+based+on+the+Transmission+Network+Use+of+System+(TNUoS)+Charges+which+are+levied+by+National+Grid+and+passed+through+to+British+Energy%E2%80%99s+customers.+TNUoS+includes+a+substantial+surcharge+based+on+each+customer%E2%80%99s+usage+during+the+Triad+periods%3A+the+higher+a+customer%E2%80%99s+usage+during+Triads%2C+the+higher+their+overall+electricity+supply+costs.%0A%0ABritish+Energy%2C+in+common+with+other+large+commercial+electricity+suppliers%2C+aims+to+reduce+National+Grid+charges+for+some+of+its+customers+by+issuing+a+%E2%80%9CTriad+warning%E2%80%9D+on+days+when+it+seems+possible+that+a+Triad+might+later+be+found+to+have+occurred.+Industrial+customers+are+often+encouraged+by+their+contract+with+British+Energy+to+reduce+their+consumption+on+those+warning+days.+British+Energy+are+restricted+by+the+contract+to+issuing+a+limited+number+of+calls+over+the+entire+winter+period%2C+anything+up+to+23.%0A%0AA+customer+who+receives+a+Triad+warning+may%2C+or+may+not%2C+take+action+(e.g.+shutting+down+their+factory+early+that+day).+Some+%E2%80%93+but+not+all+%E2%80%93+customers+are+contractually+required+to+inform+British+Energy+whether+or+not+they+are+reducing+their+consumption.+Therefore+British+Energy+cannot+be+sure+by+how+much+overall+consumption+will+drop+if+a+warning+is+issued.+Furthermore%2C+the+national+consumption+is+also+affected+by+suppliers+other+than+British+Energy+who+may+also+have+issued+a+Triad+warning.%0A%0AIt+is+thought+that+this+system+may+suffer+from+%E2%80%9Cnegative+feedback%E2%80%9D.+That+is%2C+on+a+day+that+is+likely+to+include+a+Triad+period+because+it+has+high+predicted+consumption%2C+many+suppliers+will+issue+warnings%2C+resulting+in+many+customers+reducing+their+actual+consumption%2C+ensuring+that+the+total+national+demand+is+actually+much+lower+than+predicted%3A+sufficiently+low%2C+in+fact%2C+that+no+Triad+occurs%2C+and+no+warning+was+actually+necessary.+It+is+expensive+for+customers+to+take+action+when+it+is+not+actually+required.%0A%0ABritish+Energy+currently+uses+the+deterministic+half-hourly+consumption+forecast+issued+by+National+Grid+and+the+recent+and+forecast+temperatures+at+hourly+intervals+at+7+locations+around+the+country+to+decide+on+a+daily+basis+whether+to+issue+a+Triad+warning.+The+decision-making+tool%2C+called+TriFoS%2C+does+not+currently+take+into+account+the+possible+problem+of+negative+feedback.%0A%0AThe+Study+Group+was+asked+to+consider+ways+of+compensating+for+negative+feedback.+Section+2+confirms+that+feedback+is+a+statistically+significant+phenomenon.+Sections+3+and+4+then+use+the+so-called+%E2%80%98Full-Information+Secretary+Problem%E2%80%99+to+motivate+the+derivation+of+possible+triad-calling+strategies.+Section+5+examines+the+possibilities+for+issuing+triad+warnings+from+analysing+historical+data.&rft.date=2007-04-13&rft.type=Study+Group+Report&rft.type=NonPeerReviewed&rft.format=application%2Fpdf&rft.language=en&rft.identifier=http%3A%2F%2Fmiis.maths.ox.ac.uk%2Fmiis%2F101%2F1%2FTriadReport.pdf&rft.identifier=++Hunt%2C+Robert+and+Clarke%2C+Liam+and+Byatt-Smith%2C+John+and+Billingham%2C+John++(2007)+Forecasting+triads%3A+the+negative+feedback+problem.++%5BStudy+Group+Report%5D+++++