Losses on the low voltage underground cable network due to contact voltage. 6 th July 2017

Transcription

1 Losses on the low voltage underground cable network due to contact voltage 6 th July 2017

2 Jeremy Wright BEng(Hons), MBA(Open), CEng, FIET, FCMI, MIAM UK Power Networks Asset Inspection, Maintenance & Compliance Manager

3 Programme Origin 2004 Jodie Lane Dies in New York City 2008 IEEE 1695 Development Begins 2015 Initial Dialogue with Power Survey 2016/2017 London Survey Supported by NIA Funding 2005 NY Regulator Mandates Survey Programme 2014 Jeremy Wright presents at Jodie Lane Conference in NYC 2016 IEEE 1695 Published 2017 CV Losses Identified 2018 IET Technical Standard??? What began as a programme to address safety has yielded interesting results in the losses area

4 Mobile Asset Assessment Vehicle (MAAV) Programme Origin The MAAV has obvious public safety benefits UK Power Networks explored a variety of possible applications for this unique system beginning in 2014 Innovation opportunity to test new detection algorithms, measurement processes and prediction tools Two stage Ofgem NIA pilot approved in 2016-Q3 Loss reduction was not originally envisioned as a potential benefit Losses opportunity became apparent only after evaluation of results

5 MAAV Overview Two surveys of Central London Survey covered approximately 1,300 miles of carriageways Survey identified 343 energised objects, which were previously unknown to UK Power Networks 24 objects discovered with greater than 100 volts at the surface Unmetered losses in excess of 1.2 GWh/yr (Equivalent to consumption of about 100 homes) Associated carbon emissions of 586 tonnes/yr

6 David Kalokitis Chief Technology Officer Power Survey Stuart Hanebuth Vice President Power Survey Dave is the Chief Technology Officer at Power Survey Company, a firm dedicated to the detection of contact voltage. Dave lead the development of the first-of-its-kind mobile detector for contact voltage, a system which has detected over 130,000 cases of contact voltage in the last 10 years. In his role as CTO, Dave has developed technologies and field measurement techniques which have become industry standard for the detection and measurement of contact voltage. Stu has more than 20 years experience in the electric transmission and distribution sector. Prior to Power Survey, Studirected the Public Safety Programmes at Consolidated Edison Company of New York, where he oversaw the investigation and mitigation of tens of thousands of cases of contact voltage. At Con Edison, Stu successfully implemented and managed more than $100 Million in Public Safety Programs, including contact voltage detection and mitigation.

7 Who is Power Survey Company? Global service provider formed in 2006 at SRI International Core Business: Contact voltage detection Over 130,000 contact voltage hazards detected 50+ vehicle fleet deployable worldwide

8 Low Voltage Cable Faults Low voltage distribution systems are fault tolerant, allowing faults to persist for long durations Contact Voltage (CV) faults are high impedance faults and the source of many distribution system events Electric shock reports by the public Manhole fires and explosions Electric service quality complaints Customer equipment damage Increased system losses Underground systems have relatively high generation rates of new faults

9 The Traditional View of Losses Technical losses are the energy required to make the distribution system operate Reductions can be achieved through optimisation of transformers and conductors Approximately 26 TWh annually across the United Kingdom Total achievable improvements are on the order of 1 to 2 TWh, with significant investment required Non-technical losses are due to administrative gaps, metering errors and theft Approximately 1 TWh annually across the United Kingdom Reduction strategies vary in cost and complexity and are often not scalable Non- Technical Losses Technical Losses

10 A New Class of Losses The MAAV trials identified a new and significant class of losses, Contact Voltage losses (CV Losses) CV Losses are not a required element of a properly functioning distribution system (i.e. not a technical loss) CV Losses are not due to administrative gaps, metering errors and theft (i.e. not a non-technical loss) CV Losses are erroneously grouped in both of the traditional loss classifications Non- Technical Losses Technical Losses Non- Technical Losses CV Losses Technical Losses

11 Contact Voltage Losses Easily detected with the MAAV Mitigated through traditional repair processes Mitigation is permanent and benefit is not impacted by load growth (i.e. there is no variable element to the loss reduction) Highly scalable CBA validated solution Estimated achievable savings 500 GWh to 1 TWh annually across The United Kingdom

12 Basis for Contact Voltage Losses CV Losses are the result of an energised cable sheath or lighting column which is making contact with the earth Both items can be modeled as earthing rods using industry reference publication from 1936 in Calculation of Resistances to Ground by H. B. Dwight This work is the basis for system earthing standards worldwide Modeled results match values measured in the field

13 Cable Sheaths Cable sheaths are modeled as horizontal earthing rods Where: R = Resistance (Ω) ρ = (Rho) Earth Resistivity (Varies with soil type) (Ω*cm) -9 L = 2X Length of horizontal wire (in cm) a= Radius of conductor (in cm) s = 2X depth of conductor (in cm) Using the formula and the following assumptions: ρ = 3,850 (Ω*cm) -9 Average Soil Resistivity 1 L = 2 Meters of Energised Sheath a= 1 cm Sheath Radius (OD/2 of cable) s = 25 cm depth of conductor The CV fault impedance is 6.82 Ω drawing 33.7 amps or 7,751 watts. If left for one year this would result in 68 MWh of losses per fault 1 Average value of British Geological Society Earth Resistivity Values for Lithology A and B at the 50% percentile at each location where a CV fault was known or suspected.

14 Lighting Columns Lighting columns are modeled as vertical earthing rods Where: R = Resistance (Ω) ρ = (Rho) Earth Resistivity (Varies with soil type) (Ω*cm) -9 L = 2X Length of horizontal wire (cm) a = Radius of conductor (cm) Using the formula and the following assumptions: ρ = 5,875 (Ω*cm ) -9 Average Soil Resistivity L = 2 Meters, average depth of grounding system, rebar, etc. a= 40 cm pole base radius (Column Diameter/2) The CV fault impedance is 9.33 Ω drawing 24.7 amps or 5,770 watts. If left for one year this would result in 51 MWh of losses per fault 1 Average value of British Geological Society Earth Resistivity Values for Lithology A and B at the 50% percentile at each location where a CV fault was known or suspected.

15 MAAV Technology Sophisticated truck mounted electric field sensor system Operates at speeds up to 25 MPH Sensitive down to 1 volt Proactively identifies potential safety hazards Pinpoints network risks Identifies CV loss locations

16 CV Loss Detection using the MAAV Survey underground service areas for fault conditions Record observations and measurements at fault locations Repair faults and analyse results

17 Case Study Energised Footway Initial Detection MAAV discovered 71.8 volts on footway Excavation found 230 volts on lead sheath due to a failed pot end Detection creates opportunity for multiple benefits

18 Case Study Energised Footway Safety Improvement Failure on UK Power Network LV cable energised non-ukpn assets: Footways Fences Lighting Columns Energised street level objects are a risk to pedestrians Sheath of buried cable was energised to 230 volts, a risk to employees and 3 rd party contractors

19 Case Study Energised Footway Reduced Losses Contact voltage faults are the electrical equivalent of a leaking water main Annual losses of 68 MWh/year The CO 2 resulting from the generation of the lost electricity is about 33 tonnes/year Carbon dioxide emissions associated with this fault would fill 159 London double decker busses annually

20 Emergent Policy Questions What is the appropriate timeframe to quantify the loss savings 1 year? 4 years? Life of the new cable? How frequently should DNO s survey networks for losses? What tools can DNO s use to incentivise repairs outside of their control? Can DNO s realize the benefit for behind the meter reductions when CV losses are the result of customer owned equipment faults? In the LCF will increased reliance on LV network lead to more CV faults and losses?

21 Summary Contact Voltage losses are: Sizable Accessible Addressable Mitigating CV losses also improves system safety and reliability Detection process is highly scalable The MAAV is an economical loss reduction strategy