Introduction
Current society has come to rely upon dependable power as a basic asset for national security; wellbeing and welfare; transportation and water supply; even amusement and relaxation-to put it plainly, almost all present-day life. Humans have expected that power will always be accessible when required at the flick of a switch. Most people have additionally experienced neighborhood blackouts brought about by a vehicle hitting a power shaft, or a lightning storm. What isn’t normal is the event of a huge blackout on a quiet, warm day. Boundless electrical blackouts, for example, the one that happened on August 14, 2003, is uncommon and comes unexpectedly [4].
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Approximately 50 million people in eight U.S states (Ohio, Michigan, Pennsylvania, New York, Vermont, Massachusetts, Connecticut, New Jersey) and the Canadian province were affected by the cascading outage. It was estimated that roughly 63 Gigawatt (GW) of load was interrupted and a loss resulting to billion of dollars were incurred. Though control was effectively re-established to most within hours, a few zones in the United States did not have control for two days and regions of Ontario experienced turning power outages for up to two weeks [5].
“During this event, over 400 transmission lines and 531 generating units at 261 power plants tripped”. Figure 1 shows the general region affected by this blackout. Upon the North American Electric Reliability Council (NERC) investigation, the system was being worked in agreement with NERC operational guidelines. In any case, there were evident reactive power supply issues in the Indiana and Ohio states before early afternoon on that day. There are various operators responsible for the dependable electric systems in respective regions; the Independent System Operator (IMO) which is operated in Ontario Canada. The New York Independent System Operator (NYISO) which operates the New York System. PJM Interconnection, LLC (PJM) which operates the mid-Atlantic area, including the northern Pennsylvania and northern New Jersey which were affected by the outage. Each act as both the system operator and the reliability coordinator. The Midwest Independent Transmission System Operator (MISO) and PJM run the overall Reliability oversight [5].
The Midwest ISO (MISO) State Estimator (SE) and Real-Time Contingency Analysis (RTCA) software were defective (not working appropriately because of programming issues) for the greater part of the evening. This kept MISO from performing legitimate “early cautioning” evaluations as the situations were developing. At the FirstEnergy (FE) control station, various PC programming failure happened on their Energy Management System (EMS) software beginning at 2:14 p.m. The EMS control focuses on checking the activity and reliability of the FE control region. Due to the failure of the EMS, this kept FE from having enough learning of the situations occurring until roughly 3:45 p.m. This added to lacking situational mindfulness at FE control station [2].
The main major incident was the tripping of FE’s Eastlake Unit 5 generator near Cleveland on the shore of Lake Erie which occurred at 1:31p.m. Eastlake Unit 5 and a few different generators in FE’s Northern Ohio service zone were producing large amounts of reactive power, and the reactive power request from these generators kept on expanding as the day advanced. Such high reactive power stacking of generators can be a worry and may prompt control and safety issues. Because of the high reactive yield, the Eastlake Unit 5 voltage controller tripped to manual operation cause of overexcitation. As the administrators endeavored to re-establish the auto-voltage control, the generator tripped. NERC Steering Group. (2004) [5] reported that if Eastlake 5; which was a critical unit in Cleveland; was still functioning, the loading onto the 345-kV transmission line of Cleveland would have been marginally lower and outages due to contacts of trees might have be delayed. The loss of this critical control center was a key factor in the loss of situational awareness of system conditions by the FE operators [2],[5].
Due to tree contact, three FE’s 345-kV Lines supplying the Cleveland-Akron area and Stuart-Atlanta line in southern Ohio tripped. The FE’s Chamberlin-Harding 345-kV line tripped at 3:05 p.m. and was just loaded to 44 percent of its summer ordinary/crisis rating, although the FE control room did not receive any alert due to an alert processor failure. After the loss of the Chamberlin-Harding line, one might say that the system couldn’t be continued without over-burdening different transmission line facilities over the crisis rating [2],[5].
The Hanna-Juniper 345-kV line was loaded to 88 percent of its summer normal and crisis rating and tripped because of a tree contact at 3:32 p.m., almost 1,200MVA had to be loaded to the remaining two 345-kV lines, Star-South Canton 345kV line tripped multiple times, each time opening and reclosing before finally going out of service while being loaded at 93 percent of its crisis rating (due to the loss of the Chamberlin-Harding and Hanna-Juniper) at 3:41:35 p.m. This falling loss of lines proceeded while little move was being made to shed the load burden or readjust the system amid this period. Because of alarm failure at FE and EMS failure at MISO control station, there was little consciousness of the occasions happening. The loss of these 345-kV lines in the northern Ohio region caused a shift in the power flow to the underlying grid system of the 138-kV lines which led to the loss of the 138-kV transmission lines since they were not designed to carry such load. It was said that about sixteen 138-Kv lines tripped in half an hour leading to the overload of the remaining line [5].
The Sammis-Star 345-kV line; which eventually tripped at 4:05:57 p.m. led to the widespread cascading in Ohio and other states. The Sammis End Zone 3 impedance relay which were operating on the real and reactive current overload and voltage caused the Sammis-Star line to trip, which also caused the tripping of numerous additional lines in Ohio and Michigan by Zone 3 Relays (or Zone 2 Relays set like Zone 3 Relays) which instead of responding to faults responded to the line overloads. The Sammis-Star line trip separated the 345-kV path into northern Ohio from southeast Ohio, setting off another, quick paced sequence of 345-kV transmission line trips in which each line trip was placing a larger load burden on the remaining lines which were still in service. The line tripping advanced west across Ohio, northward into Michigan, thereby severing western and eastern Michigan, lines between PJM and New York tripped, Ontario’s east-west line tripped also tripped [5].
The power outage could have been avoided by load shedding in northeast Ohio before the Sammis-star tripping occurred. At around 4:10 p.m., because of the sequential loss of significant tie-lines in Ohio and Michigan, power started flowing counter-clockwise from Pennsylvania through New York and Ontario. This 3,700 MW turn around power flow was planned for serving load in Michigan and Ohio, which was at this stage separated from every other system apart from Ontario [2],[5].
Finally, Voltage crumbled because of heavy loaded transmissions, and blackout of a few hundred lines and generators resulted, coming full circle in a power outage of the whole district and Eastern Ontario leaving north-western Ontario still connected to Manitoba and Minnesota [2],[5].
Figure 1 Areas affected by the U.S.-Canadian blackout of 14 August 2003. [2]
Figure 2. Location of Three Line Trips [5]
Muir, A., & Lopatto, J. (2004) [4] indicates that the cascading outage was brought about by insufficiencies in explicit practices, electrical gear, and human choices influenced the conditions and results. Based on the final NERC Report [5], a few of the causes were highlighted and discussed:
1) Inadequate understanding of the system: The report affirms that FE neglected to take fundamental long-term planning into action. They also did not carry out adequate voltage stability analysis of the Ohio control zone and operational voltage criteria.
East Central Area Reliability Coordination Agreement (ECAR) did not carry out adequate analysis of FE’s voltage criteria in so doing allowed FE make use of inadequate system without improvements.
2) Loss of situation awareness:
The report expresses that the FE control room administrators depended intensely on alarm processors. They had no alarm failure detection system set up, due to not having any occasional diagnostics to report the condition of the alarm processor. They neglected to guarantee security of the framework after critical unanticipated likelihood due to the collapse of the Energy Management System (EMS).
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They basically worked under the presumption that the framework was in good condition. Failure of the FE computer support staff in transferring the information of the loss of the alarm functionality to the operators also contributed to the cause. If it had been communicated on time, it would have been possible to detect the Chamberlin-Harding line outage or enable the administrators to be increasingly open to the data being gotten from MISO or any neighboring framework.
3) Insufficient level of vegetation management:
The report states that by FE failing to practice effective vegetation control in trimming the trees, it allowed the outage of three 345-kV lines (Chamberlin-Harding, Hanna-Juniper, and Star-South Canton lines) and one 138-kV line (Cleveland-Akron line) and the over-loading and tripping of the Sammis-Star line. It was accounted for that all the three lines experienced non-irregular failures because of unchecked tree development. With appropriately quiet climate which existed in Ohio on August 14, the odds of those three lines haphazardly tripping within 30 minutes is very little.
4) Ineffective diagnostic support by Reliability Coordinators:
Due to the MISO real-time contingency analysis, which works on the condition only if the state estimator solves, did not operate properly in automatic mode again until after the outage.
Without real-time contingency analysis information, the MISO operators were not aware of the FE system issues sufficiently early. With an operational state estimator and real-time contingency analysis, MISO operators would have known of the contingency violation and could have informed FE, thus enabling FE and MISO to take appropriate actions to return the system to within limits. The PJM and MISO reliability coordinators lacked an effective procedure on when and how to coordinate an operating limit violation observed by one of them in the others area
Recommendation/Actions to Avoid Future Blackouts
According to Muir, A., & Lopatto, J. (2004) [4] and supported by NERC Steering Group. (2004) [5] some actions were proposed to prevent another future outage and minimize any future risk that may arise. These actions are listed as follow:
- Reliability standards should be made compulsory which should be punishable with a penalty for non-fulfillment.
Proper government branches in both the United States and Canada should also enforce mandatory standard
- The trainings for Operators and Reliability Coordinator should be improved. It was found that most of the operators at the control centers had not received the appropriate training and were not honed with the knowledge in answering to emergencies that may arise. The personnel and operators lack the drill and response to real life simulations. All this contributed to the lack of situational awareness and not being able to response rapidly when an intervention was likely still possible.
- A standard on vegetation clearances ought to be set up. A quantifiable standard indicates the base clearances between energized high voltage lines and vegetation ought to be created by the arranging board with the Standards Authorization Committee, Appropriate criteria from the National Electrical Safety Code, or other proper code, ought to be adjusted and translated in order to be applied to vegetation.
- Regular maintenance, assessment, and testing of power plant and substation equipment should be carried out to guarantee the condition of the gears and to ensure they are always kept in a decent condition and are working under the right design parameters; testing and maintenance will also help to identify inappropriate setting on control and protection systems, in addition to extending equipment life, it also minimizes the risk of failure resulting from the mis-use of the tools [2].
- Communications protocols should be fixed, to enable stronger communications during alarms and crisis.
- Fortify reactive power and voltage control practices in all NERC areas. Redesign correspondence equipment’s where fitting.
- Trainings either long or near terms should be improved
- Clear definition of typical, alert and crisis mode as well as obligations and job roles of the coordinators and operators should be established.
- Automatic load shedding should be employed
Conclusion
On August 14th, 2003, a blackout affected Northeast America and Canada in which millions of people were affected. The tripping of the Sammis-star 345-kV transmission line prompted the outcome propagating across borders and turning into a cascading blackout which affected eight states and two provinces in Canada. Some factors that contributed greatly to the event were a lack of situational awareness by the control operators and tree maintenance.
References
[1] Andersson, G., Donalek, P., Farmer, R., Hatziargyriou, N., Kamwa, I., Kundur, P., … & Schulz, R. (2005). Causes of the 2003 major grid blackouts in North America and Europe, and recommended means to improve system dynamic performance. IEEE transactions on Power Systems, 20(4), 1922-1928.
[2] Pourbeik, P., Kundur, P. S., & Taylor, C. W. (2006). The anatomy of a power grid blackout-Root causes and dynamics of recent major blackouts. IEEE Power and Energy Magazine, 4(5), 22-29.
[3] Vine, D. (2017). Interconnected: Canadian and U.S. Electricity. Center for Climate and Energy Solutions. Retrieved from https://www.c2es.org/site/assets/uploads/2017/05/canada-interconnected.pdf
[4] Muir, A., & Lopatto, J. (2004). Final report on the august 14, 2003 blackout in the United states and Canada: Causes and recommendations.
[5] NERC Steering Group. (2004). Technical analysis of the August 14, 2003, blackout: What happened, why, and what did we learn. Report to the NERC Board of Trustees, 13.
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