Circuit Protection and Utilisation of Electricity

Circuit Protection and Utilisation of Electricity proletariat 1With the aid of desir equal diagrams, describe in detail, the construction and operating principles of the fol secondarying roofy surfs. Include in your description the advantages and disadvantages of eacha) Oil circumference breakerAn anoint lick breaker or OCB is a character reference of device which wasting diseases disparate kinds of oils as insulating materials/insulators in order to reduce the twinkle when activated. The traffic circle breaker willing devour two intercommunicates that ar forced to separate while being submersed in oil, the oil is in that respect to evaporate any heat produced by the arc when the breaker is tripped. An OCB is made up of a alloy tankful to contain the oil and contacts, contacts for carrying the current and the oil which is the insulating material that stops an arc occurring. The operation of this pillowcase of breaker is simple, the contacts start out in the closed position so that the perimeter is complete and when a fault occurs the contacts be wherefore forced apart(predicate) causing an arc to form. Sometimes an arc rat emit heat which can damage the circuit and machinery, this is why we use the oil to evaporate the heat. The oil will be turned into gas(hydrogen) and and so slowly dis moorage any oil left, the arc will be snuff out when the contacts move far outdoor(a) from each different. The OCB contacts can just abouttimes get burnt when arcing has occurred and carbon can form in the area around the contacts. The carbon makes the oil lose non film director strength and therefore means that the circuit breaker is less outcomeive at faulting the current. The OCB needs to be drained and refilled when it has tripped, likewise the contacts need to be closely inspected for burning or carbon build up. on that point are two types of oil circuit breaker Bulk Oil- This is a circuit breaker that requires larger amounts of oil so that the arc can be destroyed. These circuit breakers can also be known as dead tank(Circuit globe, 2016) because the tank is positi angiotensin converting enzymed at ground potential. If the potential is higher then more oil will be unavoid satisfactory as the arc will be stronger and harder to extinguish. some other use of this circuit breaker is to insulate all live parts in the breaker from the earth. Minimum Oil- This circuit breaker aims to use the minimum required oil that is possible, instead of extinguishing the arc completely using oil it also uses porcelain. The porcelain insulates the circuit breaker live parts from the earth. The bedroom of the breaker is lined with bakelised (Circuit globe, 2016) paper, this paper has good mechanical and electrical properties. The tube moves vertically in order to break contact, when the contacts start to separate then oil is forced into the piston chamber to reduce arcing.The advantages of OCBs Due to the oil having a high dielectric strength(Circuit globe, 2016) it can be used asinsulation once the arc has been dealt with. The hydrogen produced repayable to the evaporation of the oil is good for cooling the device anddiffusing. The oil creates a clearing in the conductors and the earth components.The disadvantages of OCBs The oil is flammable which means that fires are able to be started with it. The oils dielectric strength decreases due to the carbon particles that pollute it. Since the tank isnt always air tight this leaves room for dangerous mixture of air which could vector sum in explosive substances being created.-If the tank needed is large then it can be expensive.b) Vacuum interrupterA vacuum circuit breaker or VCB is a type of circuit breaker that uses a vacuum to extinguish the arc. This works best on weaker potentials, as higher voltages will be also strong to extinguish. The breaker can be made of steel and consists of a chamber which is the vacuum interrupter, the material for the contacts nee ds to be perfect as differently there wont be an effective spliceion. The application of this type of circuit breaker is to switch HV devices, they are as effective as SF6 breakers which mystify a big chance of outflow. The reason it is better than other circuit breakers is because when the contacts separate inner the vacuum they have a greater dielectric strength which builds up so that it is thousands of times higher than normal circuit breakers.Advantages to a VCB Since there isnt any material or substance inside the chamber theres no risk of fire They have a good service life as they have minimal parts Due to the fact that it doesnt use harmful gases or substances it is safer for good deal to workon and for the environment. The replacement and main(prenominal)tenance is much easier. they can be used repeatedly. There are no gases inside which means that there is no room for gas emission leakage.Disadvantages to a VCB when the vacuum has been damaged, failed to extinguish the arc or loses the vacuum it cantbe repaired on site. This is due to the complex design and conditions that it needs to befixed. the vacuum interrupter will need surge suppressors (Hub pages, January 2 2014) that are inparallel with the phase interrupters with low currents. they are uneconomical if only small quantities are being madec) HRC liquid fuseA HRC liquid fuse is a high voltage fuse which have a relatively high current rating and breaking capacity. This means that the fuse can be used in some high voltage applications, high voltage fuses need specific designs so that they can handle it without breaking. There are two types of HRC fuseLiquid type HV HRC fuseThis type of fuse is filled with a fluid called Carbon tetrachloride (Circuit globe, 2016) and they can be used for a large number of high voltage applications. They can protect circuits that have a 400 A rating or higher, their breaking capacity is around 6100 A when used on a circuit with a 33KV supply. This fuse is m ade up of a glass tubing filled with the above fluid and it has brass caps on either end. There is also a fuse link which gets fixed to one of the caps and then the other end is obligateed to a bronze spiral fixed onto the other cap. When the limit of current is exceeded then the fuse link will be pursy, this will retract the spring so that it hits a liquid detector. When the arc is created and extinguished a small quantity of gas will be produced, fuses arent normally used as the number one protective method for a circuit. The circuit will have other circuit breakers, if the circuit breakers fail then the fuse will blow.Advantages cheaper than other circuit protecting devices-Maintenance is not required Is able to be used in high and low voltage applications The operation/breaking of the fuse is automaticDisadvantages the fuse needs be rewired or replaced when blown the fuse can sometimes have tripping time issues when dealing with different voltages.Cartridge type HV HRC fuseTh is type of fuse is very similar to low voltage fuses however there is a specific component that makes it effective at extinguishing high voltage arcs. The only difference in the design I that the wire is wound into a ring shape so that the corona effect can be avoided, the corona effect is the ionization of a fluid surrounding a conductor that is electrically charged (wiki user, 2016). some applications may require two fuses to be put in parallel, one of them will have a low resistance and the other a high resistance so that the low resistance will blow first and slightly reduce the stress on the circuit when it breaks. This type of fuse can be used up to 33kv as they have a breaking capacity of about 8,760 A.Advantages They dont deteriorate everyplace time They have a high speed of operation No maintenance is required It is cheaper than other methods They can be used for both high and low voltage applicationsDisadvantages After it has blown it must be replaced when an arc occu rs it produces heat energy which means that it is a fire hazard and candamage some of the components insided) HRC expulsion fuseThis type of fuse uses gases produced by the arc and its lining to extinguish the arc, it also is vented to let the gas out. The fuse link can be surrounded by liquid which turn into gas such as boric acid (Wiki User, 2016) when the fuse is blown the heat from the arc will make the boric acid change into gas. The gas will then quickly extinguish the arc, the gas also will explosively burst out the ends of the fuse and this is the reason they must only be used outside. There is usually a type of pin so that you can manually blow all three phases in case only one had gone. This fuse can be used with very high amperage as well as low voltage.Advantages No maintenance is required Cheaper than other types of circuit breaker Simple institutionDisadvantages Can be dangerous when blown as there is an explosive part in the process ravish to other devices may occu r if they are in close vicinity to the fuse at time of breaking Needs to be replaced and repaired when blownTask 2Produce suitably designate diagrams and produce a detailed explanation of the principles of operation of an inverse definite minimum time electrical relay.An inverse definite minimum time relay AKA IDMT relay is a circuit protection device that consists of an upper electromagnet which has two windings, There is a primary and a secondary. The primary winding is attached to the current transformer that is on the line that is in need of protection and has eight tappings. The tappings are committed to a plug which sets the bridge by the number of turns that will be used, the settings then can be adjusted so that required current setting can be achieved. The secondary winding is then energized by the inductor effect and is wound over the limb in the middle of the upper electromagnet, it also spreads over the limbs of the lower electromagnet. There is a disc which has flux l eakages, the flux leakage comes from the upper electro magnet and it is in phase with a disc on the lower electromagnet. Te disc has a spindle which has a moving contact that connects two of the fixed contacts when it has rotated into a certain position. The setting of this position or angle varies, it can vary from 0 to 360. This device operates during overload conditions, when over current occurs this device will protect the circuit from any damage that may be caused.An 11 kV three phase system develops a 159 MVA line to line short circuit. The system is protected by a scheme using 500/1 ratio Current Transformer rated at 5 A and IDMT relays. Determine the operating time for the relays if the time multipliers were set to 0.45 s and the plug setting was 120 %.IDMT relay current characteristic curve Task 3Describe with the aid of diagrams the importance of properly earthing equipment.With the aid of diagrams describe the following methods of earth fault protectionEarth fault relay. residual current device.Use examples of earth fault protection at your place of work.a)There are many risks within my workplace however one of the main risks is electricity, it is very important that I am protected from this risk as it can cause severe injury or fatality. To ground something means to attach a path for the electrical current to return to the ground safely. This will stop the current using us as paths, when a short circuit occurs the current will find the easiest way back to the ground. There are a few main reasons for grounding all electrical equipment Prevent Damage to equipment, injury or death This is the most important reason in myopinion as it will literally protect our lives. The most important formulation to work is safety whichmeans making all equipment safe for use, we do this by earthing it and doing PAT testing. PATtesting (Portable appliance testing) is in place to make sure that the equipment works andwill not hurt or damage itself/others. Electricity i s very dangerous and can arc if not earthedor correctly encased, it can cause death and injuries which could affect the rest of someoneslife. Electrical overload protection this means that it will protect us from any surges that mayoccur, this could be a surge in current or perhaps a lightning strike. If the equipment isearthed then the surge will go straight into the ground, if however it isnt then it would gointo whatever was in contact with the equipment. Direction of electricity- The electricity will have a clear, safe path to the ground which meansit is much safer for people to use the equipment. The current will be able to move safely andefficiently throughout the system without risk of hurting or damaging the circuit/ psyche usingit. Stabilization of voltage levels Grounding also makes sure that all the currents and power aredistributed around the circuit to their proper places. This means that there is little room forover current and the circuit being broken, it provides a r eference point for the voltage sourcesin the circuit system. The earth is the best conductor the earth is a very good conductor, the electricity which istrying to get to earth will also take the route with the least resistance. This is why we areperfect for connecting the appliance to the earth, grounding the system will give theelectricity a better path.Grounding can be done individually at peoples houses by use of a metal rod or extendable metal pipe that runs into the house from the underground water supply. There are different types of Earthing/Grounding Plate type- this is a method where a small metal plate is buried no more than 3 meters below the housing, it is connected to piping which is then connected to the houses service panel. Pipe type- the pipe or rod will have a set of terminals that copper conductors can connect to, the copper conductors then will be put into the service panel for the house, this would ground the houses electrical appliances. Strip/Wire Earthing- Th ese are used between casings of metal equipment to earth/ground the device or machinery. It can be attached from the casing to another piece of metal that goes into the ground.b) i) Earth Fault RelayA relay is a device that is able to detect unordinary conditions within the system, it enables the correct circuit breakers to trip when over current is detected. Most relays operate with the induction principle, this means that when the relay operates its contacts are closed in the circuit and the passage of current within the coil in the trip circuit activates a loon. The plunger then will activate the appropriate circuit breaker to trip, this means that the area of fault in the system is disconnected safely. This type of relay is essentially there to trip the circuit breaker if there is a fault with the earthing pathway, this could be damaged cable or a build up in resistance causing excessive current. The induction principle consists of moving parts such as an aluminium disc fixed onto a stopcock and this rotates on two bearings between the poles of an electromagnet and damping magnet. The electromagnet gets wound and has seven taps. The seven taps are on the front of the panel, the tap that is required can be chosen by pushing in the plug. There is a setting called the pick-up current which can be varied via the use of a plug multiplier. The pick-up current set of earth fault relays are normally quite low.ii) Residual current device- A residual current device AKA an RCD is an electrical device that breaks a circuit when it senses that the current is unbalanced or overloaded between the line and neutral conductors. These devices are more effective at keeping the operator safe than fuses and circuit breakers are, they will prevent fatalities if someone were to touch a live part. They do this as they are highly sensitive and will switch off electrically if there is any fault. They make sure that the circuit is switched off if it detects electricity flowing d own a wrong path, this could be caused by a cut or damaged wire coming into contact with something other than the severed cable. There are a few types of RCDs Fixed- This device is used in consumer units and will protect a group of circuits or individual ones if that is what is required. It will protect anything in the circuit including any appliances attached to the circuit, the fixed RCD will hug drug a very quick protection from fatality or severe injury. Portable- This device is able to be plugged into the socket and will protect the equipment, lead and person touching the equipment. However it wont protect the whole circuit, if someone were to touch another part of the circuit they may still get electrocuted. Socket-outlet- This is basically a socket with a built in RCD, it can be used as a regular socket would be. It doesnt protect the whole circuit, it will protect the equipment plugged in and the leads, as well as the person touching the equipment.References Circuit globe ( 2016) Oil Circuit Breaker online Available http//circuitglobe.com/oil-circuit-breaker.html Accessed 21/12/2016 http//hubpages.com/technology/Vacuum-Circuit-Breakers-Advantages-Disadvantages https//en.wikipedia.org/wiki/Corona_discharge https//www.mepits.com/tutorial/472/Electrical/Electric-Fuse http//www.cooperindustries.com/content/dam/public/bussmann/Electrical/Resources/solution-center/technical_library/BUS_Ele_Tech_Lib_Fuses_E_Rated.pdf http//www.platinumelectricians.com.au/blog/importance-grounding-electrical-currents/ http//www.electricaltechnology.org/2015/05/earthing-and-electrical-grounding-types-of-earthing.html http//www.allinterview.com/showanswers/90014/what-is-idmt-relay-how-it-works.html http//cindulkar.tripod.com/lab13.pdfhttphttps://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhxjNLYriFAzlbG1Y0eWaqwQMCXVJ9cpF_52CKftGHPzGwgCebbfF6duQjbDf6nJNfaE3T10m5jxz5s3gG5baqGY8Edhtq1EV-vBPx1TmbP18s1oCk46K3vV7xLDck8d_PHRcchIvpL7m1R/s1600/power+system+protection+13.png http//www.itmikro.com/app/webroot/UploadedContent/images/pro_3_1.png http//www.electricalsafetyfirst.org.uk/guides-and-advice/electrical-it ems/rcds-explained/