UE Project N Assessment and applicability of the global risk assessment tool. Hanne Vefsnmo, SINTEF Energy Research

Transcription

1 UE Project N Assessment and applicability of the global risk assessment tool Hanne Vefsnmo, SINTEF Energy Research Final workshop, Rome,

2 Outline Short introduction to the AFTER risk assessment tool Description of the test system Risk evaluation of different threats and operating states Risk evaluation of different hidden failure probabilities Applicability of the tool 2

3 Bow tie model 3

4 SICILY TEST SYSTEM 4

5 Sicily 220/400 kv transmission system 400 kv 220 kv Main load area is in the Northwest Main generation area is in the East Small Realistic power system 5

6 Two different operating states High load operating state an autumn peak day time Low load operating state autumn night time Different topologies in the two states 6

7 RISK EVALUATION OF DIFFERENT THREATS AND OPERATING STATES 7

8 The choice of threat under study 8

9 The low load operating point is more critical in terms of loss of load risk The reduction in risk from low load to high load is due to a more meshed grid in the high load situation The less meshed grid topology makes cascadings and/or low voltage problems occur more frequently over the set of contingencies 9

10 Total expected loss of load for different threat scenarios comparing high load and low load conditions 180 Global risk indicators in db (base = ) for threat scenarios comparing high load and low load conditions Snow storm 1 Snow storm 2 Wind 1 Wind 2 Icing 1 Icing 2 Pollution 1 Pollution 2 Pollution 3 Lightning Earthquake 1 Earthquake 2 Landslide 1 Landslide 2 Sabotage 1 Sabotage 2 Sabotage 3 Sabotage 4 Flood 1 Flood 2 Tree 1 Tree 2 Tree 3 Fire Aging 1 Aging 2 HIGH LOAD LOW LOAD 10

11 HIDDEN FAILURES A hidden failure of a protection system is a permanent defect that will cause a relay or a relay system to incorrectly and inappropriately remove circuit elements as a direct consequence of another switching event. (Phadke and Thorp, 2006) 11

12 AFTER risk assessment tool 12

13 Hidden failures are among the major causes of blackouts Three scenarios: 5 % hidden failure probability 1 % hidden failure probability 0 % hidden failure probability 13

14 The cumulative sum curve for the loss of load severity indicator clearly shows the effect of including hidden failures LOL Severity Index Cumulative Curve (time interval = 10 minutes) phf = 5% phf=1% no HF's

15 The effects of considering the effect of hidden failures become even more prominent when looking at the risk instead of only the severity. Although the difference between zero and one percent probability of hidden failure looks negligible in the figure, it is equal to 5%. It is just vanishingly small compared to the 239 percent increase one experiences by going from zero hidden failure probability to five. 15

16 The global loss of load risk shows a 239 % increase when the hidden failure probability increases from zero to 5 %. Total expected loss of load [MW] 5,0E-05 4,5E-05 4,0E-05 3,5E-05 3,0E-05 2,5E-05 2,0E-05 1,5E-05 1,0E-05 5,0E-06 0,0E+00 0% HF probability 1% HF probability 5% HF probability 16

17 APPLICABILITY OF THE RISK ASSESSMENT TOOL 17

18 Visualization of the actual risk level Send alarms to operators based on the risk level Example: Threat: ice and snow storm Contingency Impact, Loss of Load in MW isorisk = 1e-12 Bubble plot of risk contributions 78 isorisk = 1e isorisk = 1e Increasing risk level Contingency Probability 18

19 Quantify the benefit of the most suitable maintenance procedure the most effective physical security measure 140 Global risk indicators in db (with base level ) for sabotage scenarios high load operating point 120 db value for risk Loss of load [ expected MW] High currents Low voltages Costs [expected a.u.] 20 0 Sabotage 1 Sabotage 2 Sabotage 3 Sabotage 4 Threat scenario 19

20 Advantages with the risk based-approach Identifying most risky multiple contingencies (N-k) Identifying of most vulnerable components for the actual weather and operating state Assessment of effects of operators' delay Improved awareness Operational planning studies to evaluate impact of RES and load uncertainties Easy-to-interpret visualisation of results Complementing the deterministic N-1 criterion 20

21 Operational planning The global risk indicator provides a better insight into the security with respect to the risk level compared to the deterministic N-1 criterion catches the power system response affected by uncertainties (e.g. hidden failures, renewable energy sources) Perform risk evaluation to quantify the dependence of the risk of losing load for several factors like probability of inadvertent trippings, operators delay in deploying control actions, uncertainties on renewable and load forecasts 21

22 Bow tie model 22

23 Input data Instead of failure rate of components, the input is expressed as the expected value and standard deviation for the specific threat and component vulnerabilities The tool offers the user default reasonable data to characterise the component vulnerability curves, so the user need only very few parameters to establish threat scenarios. Possible to start from real time data retrieved from web services 23

24 Wide application range 24