1. Frankfurt (Germany), 6-9 June 2011 1 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

2. Frankfurt (Germany), 6-9 June 2011 Small hydro power plants (1 - 10 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

3. 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

4. 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

5. 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:

6. 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

7. Frankfurt (Germany), 6-9 June 2011 7     Qs=0 Line voltage – 20 km feeder (FeAl 120), 2 MW load Reactive power flow into feeder: Illustration – High generation & low load: Coordinated

8. 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: