Author Topic: Why Power Grids Collapse?  (Read 230 times)

Offline Esrat

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Why Power Grids Collapse?
« on: January 14, 2015, 06:39:39 PM »
Bangladesh Power grid experienced a major disaster on  November 1, 2014. While the reasons leading to the grid collapse are under investigation media reports quoting responsible sources indicates that the trouble started when the Bheramara, Khustia substation receiving power supply from India tripped and in cascading effect there after national power grid collapsed. One after all power generating unit cased operation causing complete brown out in Bangladesh for several hours. The incident that caused a blackout for the longest period after the one caused due to the cyclone Aila in 2007.

The setback forced the whole nation to live without power for at least 8 hours before starting to restore gradually after 7:30 pm in the capital, Dhaka.But the airports, hospitals, Bangabhaban, Gonobhaban, the Prime Minister's Office, the Jatiya Sangsad and other important installations witnessed the worst-ever power outage this time. The standby generators at different establishments of the city ran out of fuel oil, causing a rush to pumps in the capital. Dwellers of high rise buildings suffered the most as they had to take stairs, as a result. Different offices had to release their employees well before the schedule.  ATM booths, telephone networks and shopping malls also suffered setback. The price of candles went sky-high as it ran out of markets within hours. The people remained in dark about the outage as they could not switch on media like television while there were hardly any social media posts.


The actual reasons which triggered such a major disaster can only be established if a through technical investigation by experienced professionals can be conducted but the media information indicate that the incident initiated from the tripping of the Bheramara substation in Kustia .

Bangladesh is importing power from India through a 400 KV dual circuit power transmission line connected the power grid of two countries from Bahrampoor West Bengal to Khustia Bangladesh. Theoretically the transmission system has a capacity to transmit 1000 MW per day .But the substation built at Bheramara can receive about 400 MW. Since commencement of power trading India usually transmitted about 250-300 MW though the agreement is there for supplying 500 MW.

Bangladesh began importing power from India in October last year through a 400-kilovolt transmission line that runs from Baharampur in West Bengal to the southwestern Bangladesh town of Bheramara. The sub-station can receive more than 400MW power at a time, but it cannot transmit anything more than that. India normally supplies 250MW to 350MW to the high voltage DC substation in Bheramara under an agreement for supplying 500MW. In recent times, this sub-station tripped at least twice when the transmission line from India brought in more than 400MW. On those occasions, no disaster took place because both demand and generation were touching the higher threshold of around 6,000MW as most power stations here were operative. But yesterday, some of the power stations around the country were kept shut because it was a weekend and demand was in the lower threshold of 4,500MW. So, there was no backup in case one of the supply sources tripped.

We hope that the findings of the investigation will be made public and if there are any human errors or deliberate negligence exemplary punishment will be met out. Power grids can collapse for few different reasons .There have been several incidents of major collapse in different countries .From our research we have found out the following ten major grid collapse which caused miseries for millions of people.

When the latest Bangladesh power grid disaster is accounted for it will be included among the top as 160 million people for several hours were directly and indirectly were impacted. We will not speculate what caused the disaster but we will definitely appreciate the initiatives of Power and Energy Ministry in restoring supply within quickest possible time.

Reasons which cause grid failures:

Electricity: An Essential Commodity:
Electricity has become an indispensable part of modern day life. Our work, leisure, healthcare, economy, and livelihood depend on a constant supply of electrical power. Even a temporary stoppage of power can lead to relative chaos, monetary setbacks, and in the extreme cases possible loss of life. Our cities live on electricity and without the customary supply from the power grid, pandemonium would break loose. Power outages can be especially disastrous when it comes to life-support systems in places like hospitals and nursing homes, or in co-ordination facilities such as in airports, train stations, and traffic control.   

Fortunately, most life support facilities have a source of backup power that is ready to automatically take over should the main power grid fail.  Backup power is also increasingly being used in corporate facilities, manufacturing, mining, businesses, and even residential houses as the dependence on electronics and computers in our daily lives increases. While a loss of power in smaller scale settings may not be life threatening, it can result in lost data, missed deadlines, decrease in productivity, or loss of revenue.

It is important to know about the possible causes of power failure in order to better protect ourselves and our businesses from its devastating effects. Once we have identified all that can possibly go wrong, it is easier to ensure that adequate safeguards are put into place. Here are a few of some of the obvious, and some not so obvious, causes of power failure:

Natural Causes - Weather Related:

The 70% of power outages in the U.S. are weather related. Numerous power failures are caused by natural weather phenomena such as lightening, rain, snow, ice, wind, and even dust.  While it is more difficult to safeguard from major power failure from natural calamities like floods and severe storms, it does not take much to safeguard your electrical systems from the effects of water and dust. Water can lead to short circuits and power failure. The damage caused due to water in electrical circuits can be very expensive so it makes sense to ensure that you are well protected from it. Electrical switchboards, wires, and circuits should be protected from exposure to water.  Dampness and excessive moisture can also lead to serious damages. If you live in areas with high levels of humidity, you should consider investing in specially sealed circuit protection devices.

Dust can also wreak havoc with electrical systems and lead to short circuits and power failures. If you live in an area that is exposed to dust or sandstorms, you should pay special attention to the location of your electrical circuits and ensure that they are protected from dust exposure as much as possible.  Sealed circuit boxes can also help in protecting your critical electrical equipment and can aid in preventing unplanned power failures.

Natural disasters have historically been at the root of the world’s most severe power outages.  Hurricanes, floods, wind storms, earthquakes, tsunamis, and other severe weather can completely destroy critical power infrastructure and result in outages that leave expansive geographic regions without power for days, weeks, and even months.


Other Causes of Outages:


Large birds, coming in contact with power transmission system accounted for 11% of outages in the U.S.  Additional causes of failures were primarily manmade outages that show up in the form of vehicle and construction accidents with power poles and power lines, maintenance from utilities, and the occasional human error.

Short Circuits:


A short circuit is the most commonly used term to describe the cause of a power failure. A short circuit occurs when an electric current travels along a path that is different from the intended one in an electrical circuit. When this happens, there is an excessive electric current which can lead to circuit damage, fire, and explosion. In fact, short circuits are one of the primary causes of electrical fires throughout the world. 

Why do short circuits occur?

Short circuits can occur when the insulation of the wiring used breaks down. It can also occur due to the presence of an external conducting material (such as water) that is introduced accidently into the circuit. Electrical batteries can explode if they are subjected to a large current. Short circuits can even occur when electric motors are forced to operate when the moving parts are jammed. This can result in abnormal buildup of current, ultimately leading to a short circuit.

Prevention & Safety

Now that we are aware of the possible causes of a short circuit, let us look at some of the ways in which we can safeguard our electrical systems from the hazards they pose. First and foremost, we have to ensure that all the equipment that is used in the electrical installation is composed of good quality materials and meets the correct specification for the application. The initial installation costs may be higher than a system made with cheaper materials but the savings you will make in avoiding potential losses caused by short circuits and maintenance can be substantial, not to mention the additional safety and peace of mind we  get.

Wires should always be of the highest quality and of the correct gauge for your application. It should also be kept in mind that wires and other electrical circuits should not be overloaded. Electrical overload leads to overheating, causing the insulation to break down, which in turn can lead to a short circuit. Pumps, pistons, rotors and other moving parts of an electric motor should be regularly serviced and checked to ensure that there is no jamming. High quality fuses, circuit breakers, and other overload protection devices should be installed so that power can be immediately disconnected in the event of a short circuit, thereby preventing damage to sensitive equipment. When utilizing circuit breakers, it is also important to select circuit breakers of the proper rating. Water is another frequent cause of short circuits. It should be ensured that all exposed circuits are kept covered and protected from moisture.

Brownouts:

A brownout is a drop in the electrical power supply. It is so called because it leads to a drop in voltage and causes lights to become dim. Although brownouts are not total power failures, they can adversely affect electrical equipment. Induction and three-phase electrical motors (like those used in industrial diesel generators) are especially at risk during a brownout, since they can overheat and their insulation can get damaged. If the main power supply is erratic and  one can experience frequent brownouts.  In such cases one  should consider investing in a backup power system that will automatically take over and provide your equipment with the necessary power when the voltage drops.

Blackouts:

Blackouts refer to a complete loss of a power to a geographic area and is the most severe form of power outage that occurs. Depending on the root cause of the blackout, restoring power is often a complex task that utilities and power stations must undertake and repair timeframes very greatly depending on the configuration of the affected electrical network. 

Power Surges:

Power surges are the bane of any electrical system. A power surge can lead to rapid overheating and loss of critical and expensive equipment. Fortunately, protection from such surges is available in the form of surge protectors and circuits breakers. Surge protection should ideally be integrated into your main power switchboard itself. Smaller setups, which have a limited number of critical pieces of equipment, can choose to utilize portable surge protection devices that plug in to the power grid.

Electrical trees:

Electrical treeing is a phenomenon that affects high power installations such as high voltage power cables, transformers, etc. Any impurities or mechanical defects in the equipment used in high voltage installations can lead to partial electric discharges in the equipment. The damaging process manifests itself in a tree-like pattern, hence the name electrical treeing. Over a period of time, if it goes undetected, this phenomenon can lead to a continuous degradation of the equipment and eventually result in a total breakdown.

In order to combat electrical treeing, it is important to use high quality materials that are designed to handle the electric load. Regular maintenance performed by trained engineers can also help to identify and rectify electrical treeing before it can cause a major breakdown.