Protection with distributed generation, experience with the Mont-Soleil wind farm project

Transcription

1 Protection with distributed generation, experience with the Mont-Soleil wind farm project Florian Romanens IEEE Workshop 28 April 2011 Kursaal Bern

2 Content BKW FMB Energie AG Mont-Soleil project Overview Layout Protection Kinds of faults Introduction to the protection functions Protection concept Short-circuit / Earth-faults Frequency Conclusion 2

3 About BKW FMB Energie AG Swiss utility company based in Bern Generation, transport and distribution of electricity Grid: 380kV, 220kV: Transmission grid 56km, 655km mesh network 132kV, 50kV: 406km, 781km mesh network Over-regional distribution grid 16kV, 0.4kV: Regional distribution grid 5 439km,14 790km radial topology, 16kV: isolated star point 3

4 Overview Mont-Soleil project 16 wind turbines (25.36MW) Before 2010: 8 wind turbines (9.36MW) New: 8 wind turbines (16MW) Located in region of Bern-Jura (CH) A new substation 50/16kV was necessary Mont-Soleil Bern 4

5 Overview Mont-Soleil project 50kV-GIS 16kV-GIS 5

6 General layout Mont-Soleil project Mont-Soleil project Juvent wind farm Mix of load and generation in the substation 6

7 Simplified layout Mont-Soleil project Substation Load and DG not mixed on the same bay - DG can create voltage problems for customers - if overhead-line: problem with the fct auto-reclosure Each generator has a 16kV circuit breaker - selectivity in case of fault in a DG Wind farm 7

8 Changes in existing distribution grid Existing distribution grids are often built only for load flow DG can create a change in the power flow 8

9 Challenges Challenges: Additional sources to supply the load Power quality: bandwidth of the voltage by the customers Additional sources in case of fault Influence on: Configuration of the grid Operation of the grid Protection concept 9

10 Kind of faults Faults in a grid with isolated star point (e.g. BKW distrib. Grid) Short-circuit Contact of 2 or 3 phases together Earth-fault Contact of 1 phase to earth Isolated star point Short-circuit Isc Isolated star point C E Earth-fault I E I E C E Isc 50/16kV 50/16kV I E Isc G I E C E G Short-circuit current is defined by the energy sources Earth-fault current is defined by the capacities of the grid (lines, cables ) 10

11 Protection functions (used in CH) Short-circuits 50/51: Non-directional phase over current (only I) 67: Directional phase over current (I & U) 21: Impedance (I & U) 81, 87L: Differential (I of both sides) Earth-faults 50/51N: Non-directional earth-fault over current (only I 0 ) 67N: Directional earth-fault over current (I 0 and U 0 ) 32N: Wattmetric directional earth fault (I 0 and U 0 ) 59N: Residual overvoltage earth fault (only U 0 ) 11

12 Protection concept Some requirements 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% communication to realize an intertrip from the protection of the bay (in the substation) to the DG-circuit breaker 12

13 Protection concept Mont-Soleil project Protection zones Each zone is defined by the circuit breakers and CTs (beginning / end) 13

14 Protection concept Mont-Soleil project Focus on the important zones 16kV switchgear Line between substation and DG Other parts of the grid DG-zone 14

15 Protection concept Mont-Soleil project 50kV 16kV (67) Iph>, 0.1s (51N) I0>, 0.1s Additional fct: (59N) U0> (51) Iph> (49) Overload kV G G A 15

16 Protection concept Mont-Soleil project 50kV (67) Iph>, 0.3s (67N) I0>, 0.3s... 16kV Intertrip to DG 1/X" Intertrip B (59N) U0> kV G G Special fct generator Alternative: (21) Impedance (87L) Line differential (51+U<) Iph+U< Rev. Interlocking prot. 16

17 Protection concept Mont-Soleil project 50kV rev. interlock. for BB short-circuit intern busbar (BB) intertrip rev. interlock. for BB earth-fault 16kV C (67) Iph>, 0.1s (67) Iph> Uph-ph< & signal = trip (67N) I0>, 0.1s (67N) I0> 1/X"... Iss 0.7kV G G Intertrip to DG 40ms Example of WT shortcircuit behaviour 17

18 Protection concept Mont-Soleil project 50kV D 16kV - DG have to stay connected with the grid. Otherwise: risk of problem 0.7kV G G 18

19 Protection concept Mont-Soleil project 19

20 Protection concept Frequency (used in CH) DG have to stay connected if f>47.5hz & U>80% Important for the stability of the grid in case of large disturbance Under Frequency Load Shedding (UFLS) Stage Frequency Load Action [Hz] shedding[%] Activation of reserve production Disconnection of pumps Load shedding 10-15% 10-15% Load shedding 10-15% 20-30% Load shedding 15-20% 35-50% Load shedding 15-20% 50-70% Disconnection of the power plants Reference: Transmission Code 20

21 Protection concept Example DG-frequency-setting: tripping if f<49hz (not appropriated) Frequency falls to 48.3Hz Transmission grid Normal state at 50Hz Objective state at 48.3Hz -50% of load Effective state at 48.3Hz With DG-frequency-setting of 49.0Hz 100MW 0MW 100MW Distribution grid 100MW 200MW 100MW 100MW 0MW 100MW DG DG DG 50 generators of 2MW 200MW load 50 generators of 2MW 100MW load 50 generators of 2MW 100MW load 21

22 Conclusion DG are / will be connected to the distribution grid Grid configuration has to take DG into account 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 are difficult to fulfil The collaboration among the partners involved in project with DG is very important 22

23 Thank you for your attention! 23