Busbars And Their Uses

Used in electrical power distribution, busbars are usually made out of aluminium or copper and they are able to conduct electricity to transmit power from the source of electric power to the load. They are usually supported by insulators and conduct electricity within switchboards, substations or other electric apparatus. Some typical applications of these devices can be to form the interconnectedness of the incoming and outgoing electrical transmission lines and transformers at an electrical substation; supplying huge amounts of amperes to the electrolytic process in an aluminium smelter by using large busbars and also interconnecting generators to the main transformers in a power plant.

 

The size of the busbar determines its application and the amount of current that it can carry safely. They can be tubular, solid or flat depending on the application and to serve different needs. A tubular busbar is hollow and this shape allows it to dissipate heat more efficiently as it has a high surface area. Hollow or flat shaped bus bars are prevalent in high current applications. Also, the hollow section of a busbar is generally stiffer as compared to a solid rod, thus this allows a greater span between busbar support in outdoor switchyards. The smallest cross-sectional area of a busbar can be as little as 10mm2, but electrical substations would make use of busbars with a diameter of more than 50 mm as they carry great amounts of amperes. Aluminium smelters would make use of these large busbars to carry tens of thousands of amperes to the electrochemical cells that produce aluminium from molten salts.

 

As they carry large amount of electricity, it is important to support the busbars with insulation to prevent any accidents from happening whereby someone may accidentally touch the bus bar. Insulation can either support the busbar or completely surround it. They can be prevented from accidental touch by placing the bus bars at an elevated height so it would not be easily accessible or by a metal earth enclosure. Some bus bars such as the earth bus bar can be bolted directly into the housing chassis of their enclosure. This prevents unwanted touch and also saves the bus bar from any damage it may incur when left exposed. There are several other ways that busbars can be connected to one another or the electrical apparatus with which they would be used with such as by bolting, clamping or welding connections. Switchgears, panelboards or busways usually contain the busbars and the electrical supply is split by the distribution boards into different circuits. Busways are a type of busbars that have a protective cover and are long in shape. Also referred to as bus ducts, these devices allow the electricity to branch out to different circuits at any point along its surface; unlike regular busbars that allow branching of the main supply only at one location.

 

The most common types of busbars present in the industry today are rigid busbars, strain busbars and insulated phase busbars. Each of these different types of busbars has different applications and uses. The rigid busbars are used in low, medium or high voltage applications, constructed with aluminium or copper bars and they make use of porcelain to insulate them. As for the strain busbars, they are mostly used in high voltage applications and are usually strung between the metal structures of a substation. They are held in place by suspension-type insulators. Lastly, as for the insulated-phase bus bars, they are used at medium voltage and similar to the rigid bus bars, they are rigid bars that are supported by insulators. These busbars are able to eliminate short circuits between adjacent phases.

 

DC motor types

Advantages & disadvantages of energy saving bulbs

Energy saver light bulbs are highly energy efficient. You can find a wide range of energy efficient products in the market. However during the time when they were introduced in the market they were available in big sizes and did not have unique designs. Moreover they were costly and took a considerable time to reach full brightness. With the advanced technology the energy light bulbs available today are much more superior to their old models. After improvisation the energy saver bulbs are available in several sizes, designs and are cost effective.

Below are some of the advantages and disadvantages discussed

 

1.       The Advantages of energy saver Bulb are many.

2.       They are environmental friendly

3.       Help in saving your electricity bills;

4.       Serve the households with 4 times better energy efficiency than the incandescent lamps

5.       Prevent carbon emissions to a large extent.

6.       Are durable and long lasting than the filament lamps.

 

Disadvantages:

 

1.       They are expensive but by considering the best eco-friendly features the price really does not matter.

2.       The Compact fluorescent light also known as CFLs are available in only white or colored lights

3.       The size of the CFLs is bigger as compared to the conventional bulbs.

4.       These cannot be used with dimmer switches.

Thus summing up briefly we can come up to a conclusion that the disadvantages of CFLs are ignorable as they have numerous solutions available. Ignoring the drawbacks which are too minute we can say that CFLs are the highly energy efficient lights.

DIFFERENTIAL PROTECTION

Differential protection is a very reliable method of protecting generators, transformers, buses, and transmission lines from the effects of internal faults.

Figure: Differential Protection of a Generator

In a differential protection scheme in the above figure, currents on both sides of the equipment are compared. The figure shows the connection only for one phase, but a similar connection is usually used in each phase of the protected equipment. Under normal conditions, or for a fault outside of the protected zone, current I₁ is equal to current I₂ . Therefore the currents in the current transformers secondaries are also equal, i.e. i₁ = i₂ and no current flows through the current relay. 

If a fault develops inside of the protected zone, currents I₁ and I₂ are no longer equal, therefore i₁ and i₂ are not equal and there is  a current flowing through the current relay.

 

Differential Protection of a Station Bus

The principle of the differential protection of a station bus is the same as for generators.

The sum of all currents entering and leaving the bus must be equal to zero under normal conditions or if the fault is outside of the protected zone. If there is a fault on the bus, there will be a net flow of current to the bus and the differential relay will operate.

 

Figure: Single Line Diagram of Bus Differential Protection

 

Hybrid cars

Hybrid cars are considered as major breakthrough in the vehicle technology progress. For long, vehicles that use gasoline or some other fossil fuels have been running on the road. People have been familiar with such kind of vehicle, but more of them are aware with such fossil fuel engine performance effects to environment condition. Pollutions that are provided by combustion process of the engine can bring bad effects. Therefore, hybrid technology is considered as the most reasoned solution to correct the failure of usual car engine, but still maintain or even improve the performance.

 

Hybrid cars technology combines two or more different power sources to make the car moving. Actually, this technology is not a new one. There have been some kinds of vehicle applying hybrid technology long time ago, such as the WWII submarine that used diesel-electric engine as its mover engine. Usual locomotive also applies such diesel –electric engine and it is considered as a hybrid engine. Any car that uses two or more power sources is recognized as hybrid car. The main benefit of such hybrid car technology types is the lower consumption of the fuel and surely lower emission rate as well. With the latest improvement of the technology, such hybrid system can also provide better performance.

 

Hybrid cars are also categorized into several types. People who want to purchase a new hybrid car should also understand the types of hybrid car so they can try choosing one that suits their need.

 

Basically, there are three types of hybrid car: full hybrid, parallel hybrid and series hybrid car. The first type is the full hybrid car. The obvious characteristic of such type of hybrid car is it still can propel the car forward when it runs slowly without any gasoline intake. The other type is parallel hybrid car. This type applies two motors that work together. The first motor is powered by gasoline and the other is powered by electrical battery. Other hybrid cars type is the series hybrid car. In this type, fuel is mainly only used to ignite the engine, while the power source is the generator. Generator has main function as the battery charger. It can charge batteries, which later provide powers to such car electric motor that drives the transmission and moves the car. The main benefit of such type of hybrid car is that it does not require fuel engine to obtain the energy; at least not immediately. Hybrid car type that is offered mostly today is the parallel type.

 

The progress of hybrid technology has been passing long timeline, from just several military vehicles to current common vehicles. Hybrid vehicles have been known by many people for about two decades. Its main concept is to combine fuel engine system and the electrical motor system that has been invented previously. The electrical engine seemed more environmental friendly, but it was only capable for short distance use, while common gasoline car provides emission. Hybrid cars battery provide energy to the electric motor until such car reaches specific speed then gas engine will take the main role. The gas engine also has function to charge the battery while it propels the car. This combined system provides benefit in the fuel intake rate as such type of car can save more fuel when the electrical motor system works.

 

Previously, the battery that provided power to the motor took pretty wide space and provided energy for short time and took pretty long time for charging, but the technology progress of hybrid car battery provides better quality battery, which is smaller, but can provide power for longer last and takes fewer times for charging. The next step in hybrid car progress is the availability of plug-in car. People can charge their hybrid car in a charging station while they get rest.

Voltage sags

Voltage sags -- or dips typically lasting from a cycle to a second or so, or tens of milliseconds to hundreds of milliseconds. Voltage swells are brief increases in voltage over the same time range.

(Longer periods of low or high voltage are referred to as "undervoltage" or "overvoltage".)

Voltage sags are caused by abrupt increases in loads such as short circuits or faults, motors starting, or electric heaters turning on, or they are caused by abrupt increases in source impedance, typically caused by a loose connection. Voltage swells are almost always caused by an abrupt reduction in load on a circuit with a poor or damaged voltage regulator, although they can also be caused by a damaged or loose neutral connection.

 

A typical voltage sag.

Voltage sags are the most common power disturbance. At a typical industrial site, it is not unusual to see several sags per year at the service entrance, and far more at equipment terminals.

Power system protection

Types of protection

 

Generator sets – In a power plant, the protective relays are intended to prevent damage to alternators or to the transformers in case of abnormal conditions of operation, due to internal failures, as well as insulating failures or regulation malfunctions. Such failures are unusual, so the protective relays have to operate very rarely. If a protective relay fails to detect a fault, the resulting damage to the alternator or to the transformer might require costly equipment repairs or replacement, as well as income loss from the inability to produce and sell energy.

 

High voltage transmission network

Protection on the transmission and distribution serves two functions: Protection of plant and protection of the public (including employees). At a basic level, protection looks to disconnect equipment which experience an overload or a short to earth. Some items in substations such as transformers might require additional protection based on temperature or gas pressure, among others.

 

Overload & Back-up for Distance (Overcurrent)

Overload protection requires a current transformer which simply measures the current in a circuit. There are two types of overload protection: instantaneous overcurrent and time overcurrent (TOC). Instantaneous overcurrent requires that the current exceeds a pre-determined level for the circuit breaker to operate. TOC protection operates based on a current vs time curve. Based on this curve if the measured current exceeds a given level for the preset amount of time, the circuit breaker or fuse will operate.

 

Earth fault

Earth fault protection again requires current transformers and senses an imbalance in a three-phase circuit. Normally the three phase currents are in balance, i.e. roughly equal in magnitude. If one or two phases become connected to earth via a low impedance path, their magnitudes will increase dramatically, as will current imbalance. If this imbalance exceeds a pre-determined value, a circuit breaker should operate.

 

Distance (Impedance Relay)

Distance protection detects both voltage and current. A fault on a circuit will generally create a sag in the voltage level. If the ratio of voltage to current measured at the relay terminals, which equates to an impedance, lands within a pre-determined level the circuit breaker will operate. This is useful for reasonable length lines, lines longer than 10 miles, because its operating characteristics are based on the line characteristics. This means that when a fault appears on the line the impedance setting in the relay is compared to the apparent impedance of the line from the relay terminals to the fault. If the relay setting is determined to be below the apparent impedance it is determined that the fault is within the zone of protection. When the transmission line length is too short, less than 10 miles, distance protection becomes more difficult to coordinate. In these instances the best choice of protection is current differential protection.

 

Back-up

The objective of protection is to remove only the affected portion of plant and nothing else. A circuit breaker or protection relay may fail to operate. In important systems, a failure of primary protection will usually result in the operation of back-up protection. Remote back-up protection will generally remove both the affected and unaffected items of plant to clear the fault. Local back-up protection will remove the affected items of the plant to clear the fault.

Low-voltage networks – The low voltage network generally relies upon fuses or low-voltage circuit breakers to remove both overload and earth faults.