06-08-2012, 10:16 PM
plz tell me how i present paper on power grid failure -causes &remidities
06-08-2012, 10:16 PM
plz tell me how i present paper on power grid failure -causes &remidities
07-08-2012, 09:48 AM
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10-09-2012, 11:15 AM
powerpoint presentation on the power grid failure in 2012 seminar topic n projects
05-04-2013, 05:45 PM
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06-04-2013, 09:40 AM
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16-04-2013, 04:46 PM
POWER GRID FAILURE
POWER GRID.docx (Size: 827.6 KB / Downloads: 33) INTRODUCTION India is divided into five electrical regions, namely, Northern (NR), Eastern (ER), Western (WR), Southern (SR) and North-Eastern (NER). Of these, the four zones NR, ER, WR and NER are inter-connected, and form what is known as the New Grid. The Southern zone is synchronously interconnected to the New Grid. Every zone is then responsible for the power needs of the states that fall under it. There is a load dispatch centre in every zone that oversees the transfer of power from the generating plant to the states and further. Depending on the need, every state then buys power and has to adhere to the withdrawal limit. All of them are inter- connected, except the Southern grid. STABLE GRID The stability of a grid is determined by keeping a check on the demand and supply. Power frequency reflects the balance between load and power generation in the grid at a given instant and the frequency would drop if there is an imbalance caused by overdrawing somewhere along the grid. This can affect the quality of power supply and the stability of the grid. To maintain the security of the grid, the permissible frequency band specified by the Indian Electricity Grid Code (IEGC) of the Central Electricity Regulatory Commission, effective May 3, 2010, is 49.5 to 50.2 Hz. The stability of the grid depends on a delicate equilibrium of demand-supply chain. The amount of load is directly proportional to the amount of power generated. When the equilibrium between power generated and consumed gets disturbed and the load becomes more, it leads to tripping of the line. It is duty of the power distributors to maintain the equilibrium intact so that not trigger a grid failure. CAUSES FOR GRID FAILURE Grids collapse due to two basic reasons. One is the failure of the equipment, like it happened a decade ago in 2002 when the northern grid collapsed, due to fog/pollution. The second trigger is power suppliers drawing excessive power from the grid. Which results in the balance of power generation and supply goes haywire with a cascading effect. This is probably the reason why the grid failed this time.The grid collapse on two consecutive days — the Northern Grid on July 30 and the Northern, Eastern and North Eastern grids on July 31 — has been widely attributed to overdrawing of power by the Northern States, Uttar Pradesh in particular. The Power Grid Corporation of India Ltd. (PGCIL), which owns and manages the power grids, failed to prevent the collapse in spite of several expensive equipment that are supposed to be in place to monitor the grids. BLACKOUT IN INDIA 2012 According to the data available from the Power System Operation Corporation Ltd. (PSOC) of the PGCIL, the grid frequency at 2.32 a.m. on July 30 was 49.68 Hz. This is as good as it can get against the ideal frequency of 50 Hz. In fact, data obtained from the NTPC Dadri thermal power plant from 12 midnight on July 30 up to the tripping instant shows that the frequency was extremely stable till the grid collapsed, with a frequency minimum of 49.72 Hz at 12.25 a.m. and a maximum of 50.09 Hz at 12.50 a.m. This range is well within the tight norm specified by the IEGC. The same was, in fact, true on July 31 as well. When the disturbance occurred at 1 p.m., the antecedent frequency was 49.84 Hz. Also, it was not a case of generating stations pumping in more power to the grid to restore the balance and the grid frequency. Supply from Dadri during that time suggests that generation was actually being reduced. In fact, it would seem quite odd to say that there was overdrawing of power at 2.30 a.m. on a rainy day. It is true that farmers do use power at night to pump water because of low tariff, which also allows the grid to maintain a certain balance, but it cannot be imagined that there would have been overdrawing by the farming community on a rainy night. According to experts, however, grid frequency is not the only parameter that warns you of an impending grid disturbance. There can be other reasons such as a single-line overloading, which is quite distinct from general overdrawing from the grid. This can be due to poor load management by the load dispatchcentre concerned. This is what seems to have happened. As per the information available from the PSOC, during both the disturbances, there was heavy power flow of 1000 MW on the 400 kV Bina-Gwalior-Agra line. Though there are two circuits available on this line, one circuit has been under outage since July 28 for upgrade to the 765 kV level. The loading capability or the permissible limit, known as Surge Impedance Loading (SIL), on this single circuit line is 691 MW. So the overloading was by more than 300 MW. Similarly, overflow was seen in many circuits in the Eastern sector as well though not as drastic. They were of the order of 550 MW against an SIL of 515 MW. CASCADING EFFECT A cascading failure is a failure in a system of interconnected parts in which the failure of a part can trigger the failure of successive parts. Such a failure may happen in many types of systems, including power transmission, computer networking, finance and bridges. Cascading failures usually begin when one part of the system fails. When this happens, nearby nodes must then take up the slack for the failed component. This overloads these nodes, causing them to fail as well, prompting additional nodes to fail in a vicious cycle. Cascading failure is common in power grids when one of the elements fails (completely or partially) and shifts its load to nearby elements in the system. Those nearby elements are then pushed beyond their capacity so they become overloaded and shift their load onto other elements. Cascading failure is a common effect seen in high voltage systems, where a single point of failure (SPF) on a fully loaded or slightly overloaded system results in a sudden spike across all nodes of the system. This surge current can induce the already overloaded nodes into failure, setting off more overloads and thereby taking down the entire system in a very short time. This failure process cascades through the elements of the system like a ripple on a pond and continues until substantially all of the elements in the system are compromised and/or the system becomes functionally disconnected from the source of its load. For example, under certain conditions a large power grid can collapse after the failure of a single transformer. Monitoring the operation of a system, in real-time, and judicious disconnection of parts can help stop a cascade. Another common technique is to calculate a safety margin for the system by computer simulation of possible failures, to establish safe operating levels below which none of the calculated scenarios is predicted to cause cascading failure, and to identify the parts of the network which are most likely to cause cascading failures. |
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