Frankfurt (Germany), 6-9 June Astrid Petterteig, SINTEF Energy Research, Norway – Paper 0840 Presented by Dag Eirik Nordgård, SINTEF Energy Research Smart grid measures to reduce losses in distribution feeders and increase capacity to integrate local small hydro generation

Frankfurt (Germany), 6-9 June 2011 Small hydro power plants ( MVA) in areas with low consumption and weak lines  Generation much higher than local consumption  Strongly varying generation (river plants without water storage)  Long feeders and high voltage levels when the generation is high  Generators consume reactive power to reduce line voltage Common DG situation in Norway

Frankfurt (Germany), 6-9 June 2011 Measured power flow into feeder with several DG units - 2 year  Frequent changes in power flow  Seasonal variations in power generation: High generation when consumption is low & Low when consumption is high  Reactive power flow increases with increasing active power generation Measurements Jan March May July Sept Nov Active power Reactive power

Frankfurt (Germany), 6-9 June 2011 Measured power flow in three different networks for 2 and 3 years:  Case I DG unit producing 2.1 MW and consuming up to 1.1 MVAr  Case II Measured: 7.1 MVAr into with 11.4 MW out of feeder  Case III Measured: 2.8 MVAr into with 5.7 MW out of feeder  Reactive power flow increases with increasing active power generation Measurements Jan March May July Sept Nov Active power Reactive power

Frankfurt (Germany), 6-9 June 2011 QsQs Is UU  Two simplified feeders analysed  In different load conditions:  Low load & high generation – Production limited by maximum line voltage  High load & low/med. generation – Frequently occurring, no line voltage issues  Compare three strategies for reactive power generation:  Qdg = 0All DG units run with zero reactive power  Qdg < 0 One or more DG unit consumes reactive power  Qs = 0 Coordinated control of reactive power  Focus on feeder losses, Maximum line voltage and flow in sub-station Reactive power flow strategies analysed:

Frankfurt (Germany), 6-9 June 2011 In networks with several synchronous generators:  Generator(s) at the end of feeder consumes reactive power  Generator(s) close to sub-station produces reactive power Goal:  Minimize flow of reactive power (Qs) and sub-station current (Is)  Reduce feeder losses (compared to strategy with Qdg<0)  Maximize active power generation without violating voltage limits (∆U)  Can increase active power generation (compared to Qdg=0)  Utilize existing network (postpone reinforcement) without increasing losses and reactive power flow Coordinated control of reactive power QsQs Is UU

Frankfurt (Germany), 6-9 June     Qs=0 Line voltage – 20 km feeder (FeAl 120), 2 MW load Reactive power flow into feeder: Illustration – High generation & low load: Coordinated

Frankfurt (Germany), 6-9 June 2011  Synchronous generators can easily contribute in voltage control Necessary in many networks  Large flow of reactive power  Common strategies for reactive power generation:  Qdg=0  High line voltages & Low losses  Qdg<0  Low voltages & High losses & High Qs into feeder Coordinated reactive power control is suggested  when generation is high & consumption is low  in many other frequently occurring operating situations  Sub-station reactive power and current is reduced compared to Qdg<0  Active power generation can be increased compared to Qdg=0 with almost the same maximum line voltage as with Qdg<0 Calculated loss reduction up to 20 %.... More efficient measures as line reinforcement can be postponed! Paper conclusion: