1. Frankfurt (Germany), 6-9 June 2011 Romanens – CH – S3 – 0220 Impact of Distributed Generation on Grid Protection BKW FMB Energie AG Switzerland Florian Romanens Paper n° 0220

2. Frankfurt (Germany), 6-9 June 2011 Content  Introduction BKW FMB Energie AG and its grid Changes in existing distribution grids  Some requirements considered by BKW  Protection concept Short-circuits and earth-faults Frequency  Conclusion

3. Frankfurt (Germany), 6-9 June 2011 Introduction  BKW FMB Energie AG and its grid Swiss utility company based in Bern Generation, transport and distribution of electricity Grid:  Transmission grid:380kV, 220kV  Over-regional distribution grid:132kV, 50kV  Regional distribution grid:16kV, 0.4kV Interconnected topology radial topology

4. Frankfurt (Germany), 6-9 June 2011 Introduction  Changes in existing distribution grids Existing distribution grids are often built only for load flow DG can create a change in the power flow by BKW: - 16kV - star point isolated

5. Frankfurt (Germany), 6-9 June 2011 Some requirements considered by BKW  DG-protection systems have to recognize: earth-f. and short-c. in case of fault on the DG-side  quickly trip the DG-circuit breaker earth-f. and short-c. in case of fault in the grid  normally allow sufficient time for the grid to clear the fault. If the fault is not cleared after a certain time, trip the DG-circuit breaker over / under frequency and over / under voltage  have to stay connected if f>47.5Hz and U>80%  Normally, a communication between substation and DG is used  to realize an “intertrip” from the protection of the bay (in the substation) to the DG-circuit breaker

6. Frankfurt (Germany), 6-9 June 2011 Short-circuits and earth-faults  Protection zones  Each zone is defined by the CBs and CTs (beginning / end) Paper n°0220 shows the protection concept for each zone 16kV switchgear Line between substation and DG Other parts of the grid DG-zone

7. Frankfurt (Germany), 6-9 June 2011 Short-circuits and earth-faults  Example: fault in the 16kV GIS in the substation GIS have a rated arcing duration of 1.0s  Faults in the GIS have to be cleared within 1.0s On the BB: cleared by the reverse interlocking busbar prot. with special “BB- intertrip” Between CB and cable termination, the “intertrip” to the circuit breaker of the DG is used intertrip Simple over current functions are not appropriated

8. Frankfurt (Germany), 6-9 June 2011 Frequency  Example with the frequency DG have to stay connected if f>47.5Hz & U>80%  Important for the stability of the grid in case of a large disturbance Under Frequency Load Shedding (UFLS)  If the load is bigger than the generation, the frequency will fall. In this case, a certain amount of load has to be shed, but the production has to stay connected to support the grid. generationload

9. Frankfurt (Germany), 6-9 June 2011 Conclusion  DG are / will be connected to the distribution grid  Due to DG, the power flow-direction can change  Grid configuration has to take DG into account  Especially protection concept have to be adapted for DG  The sum of a lot of small generation units can impact on the stability and reliability of the grid  Some requirements mentioned are difficult to fulfill. Therefore, the collaboration among the partners involved in projects with DG is very important

10. Frankfurt (Germany), 6-9 June 2011 Thank you for you attention!