Energy Saving Opportunities for Transformers Hans De Keulenaer Outokumpu Tara Mines Energy Efficient Motors & Transformers Workshop May 7, 2002

15-May-022 Content Introduction Technical issues & standards Economic equations Ecological equations The business case for high efficiency transformers Conclusion

15-May-023 Why transformer efficiency is an issue? All electricity passes through several stages of transformation Savings potential of 22 TWh / year for EU Technology exists Economic potential Many pieces to the sustainable energy puzzle

15-May-024 Losses in distribution transformers No load loss, or iron loss (Po) Load loss, or copper loss (Pk) –DC loss –Extra losses eddy current loss in windings stray loss Other losses (ventilation, …)

15-May-025 No load loss Extra loss Resisitive loss Conventional load loss excl harmonics Extra loss due to harmonics Unloaded Rated load Actual load Actual load (excl harmonics) (incl harmonics) Load loss Losses in distribution transformers

15-May-026 Iron loss Occurs 24 hours / day, 365 days / year Example: 1,600 KVA, Po = 2,600 W –Annually2,600 W * 8,760 hrs = 22.8 MWh / yr –30 yrs= 684 MWh –Emissions (0.4 kg CO 2 / kWh)= 274 tonnes –5 c / kWh= 34,200 €

15-May-027 Historical evolution in the production of magnetic steel

15-May-028 Evolution of magnetic steel since the introduction of cold-rolled magnetic steel

15-May-029 Copper loss Occurs only when transformer is loaded Varies quadratically with the load Example: 1,600 kVA, Pk = 17 kW, 50% loaded –Annually17 kW * 8,760 hrs * 0.5^2 = 37.2 MWh/yr –30 yrs= 1.11 GWh –Emissions (0.4 kg CO 2 / kWh)= 444 tonnes –5 c / kWh= 55,500 €

15-May-0210 Loading Case 1: –30% of time 80% load –70% of time 10% load Case 2: –8 80% –8 40% –8 10%

15-May-0211 Typical load profile

15-May-0212 Results Energy transformed: –1,600 kVA * 0.5 * 8,760 = 7,008 MWh / year Efficiency –  = 7,008 / (7, ) = 99.2% Lifetime cost: –Transformer:10,000 €10% –Iron loss:34,200 €35% –Copper loss:55,500 €55% –Total99,700 €100%

15-May-0213 Transformer efficiency 400 kVA, efficiency level A-A’ (HD428)

15-May-0214 low load 400 kVA, efficiency level A-A’ (HD428)

15-May-0215 Efficiency standards Two approaches –European approach: specify Po and Pk CENELEC HD428 (oil)Po class A’, B’, C’ Pk class A, B, C (nine combinations) CENELEC HD538 (dry)one class for Po, Pk –US approach: specify efficiency at average load (typically 35-50%)

15-May-0216 Source: CENELEC Distribution transformer efficiency standards

15-May-0217 Extreme cases High loss >> AA’ Low loss >> CC’

15-May-0218 Comparison of efficiency at 50% load

15-May-0219 Conductor materials Cu and Al transformers can be built to comply to the same performance and quality standard Smaller ratings are typically cheaper with Cu In general, use of Cu leads to: –heavier, but more compact windings –a smaller core –a smaller, more compact transformer –a lower noise level –less oil-content

15-May-0220 Copper and Aluminium Designs for the same efficiency

15-May-0221 Dry-type versus oil-filled transformers higher initial cost higher no-load losses lower load losses harmonics cause less extra heating and ageing better fire protection no oil spilling container

15-May-0222 Total loss = 1685 W Full load losses in a 100kVA C-C’ transformer

15-May-0223 Harmonic profile of a typical Personal Computer

15-May-0224 Total loss = 3245 W Full load losses in a 100kVA C-C’ transformer

15-May-0225 where T is working temperature at rated fundamental power, P f,, P k is the total power and T is the rated life-time in years Effect of additional losses on life-time

15-May-0226 Harmonic culture

15-May-0227 Economic evaluation 2 approaches to buy a transformer –Specify Po and Pk –Specify A & B factors Ct = Purchase price + A * Po + B * Pk WithI = interest rate7% n = lifetime30 yrs C kWh = cost / KWh0.05 c I l /I r = loading50%

15-May-0228 Example 1600 KVA, 50% load, oil-cooled: (A = 5.4 euro / Watt; B = 1.3 euro / Watt) –EfficiencyAA’CC’ –Purchase9,700 €10,300 € –Load loss22,100 €18,200 € (1.3 * 17,000)(1.3 * 14,000) –No load loss14,040 €9,180 € (5.4 * 2,600)(5.4 * 1,700) –Total45,840 €37,680 €

15-May-0229 A and B values for selected countries

15-May-0230 Lifetime owning cost 400 kVA oil-cooled

15-May-0231 Beyond the magic of A & B

15-May-0232 Example - revisited 1600 KVA, 50% load, oil-cooled: –EfficiencyAA’CC’ –Purchase9,700 €10,300 € –Load loss1,850 € / yr1,533 € / yr –No load loss1,140 € / yr745 € / yr –Result Payback10 months 30 years

15-May-0233 Ecological evaluation 1600 KVA, 50% load, oil-cooled: –EfficiencyAA’CC’ –Energy 210 GWh210 GWh transformed –No load loss684 MWh447 MWh –Load loss1,110 MWh921 MWh –Emissions718 tonnes547 tonnes –Emission savings171 tonnes

15-May-0234 Soft benefits Save energy Save emissions Noise? Reduced heating Improved lifetime Reliability? More robust against harmonics

15-May-0235 What’s the catch? Increased capital outlay Commercial policy of suppliers Small amounts Risk of being a pioneer

15-May-0236 Energy & emission savings potentials related to transformers & standby power

15-May-0237 More information –electronic library –calculation tools K-Factor & Factor K Investment evaluation spreadsheet –daily, on-line measurement of energy saving for 4 high efficiency transformers installed in Poland

15-May-0238

15-May-0239

15-May-0240 Super-trafo demonstration

15-May-0241 Conclusions Evaluate transformers for lifetime cost –oil-cooled Buy only CC’ or higher Evaluate transformer with 15-20% less loss than CC´ –dry-type if you need the advantages evaluate transformer with 15% less loss than HD538 Check harmonic culture Consider replacement of veteran transformers