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Romanens – CH – S3 – 0220

Impact of Distributed Generation on Grid Protection. Paper n° 0220. BKW FMB Energie AG Switzerland. Florian Romanens. Romanens – CH – S3 – 0220. Content. Introduction BKW FMB Energie AG and its grid Changes in existing distribution grids Some requirements considered by BKW

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Romanens – CH – S3 – 0220

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  1. Impact of Distributed Generation on Grid Protection Paper n° 0220 BKW FMB Energie AG Switzerland Florian Romanens Romanens – CH – S3 – 0220

  2. 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. 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. 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. 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. 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 DG-zone Other parts of the grid

  7. 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. 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. generation load

  9. 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. Thank you for you attention!

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