With aid from suitable diagrams, describe at length, the building and operating concepts of the following circuit breakers.
Include in your description advantages and disadvantages of each
a) Oil circuit breaker
An oil circuit breaker or ‘OCB’ is a type of device which uses unique kinds of oils as insulating elements/dielectrics in order to decrease the arc when activated. The circuit breaker will have two contacts that will be forced to separate while staying submersed in essential oil, the oil is there to evaporate any warmth made by the arc when the breaker is usually tripped. An OCB is made up of a metal tank to contain the oil and contacts, contacts for carrying the existing and the oil which is the insulating materials that stops an arc happening. The operation of this kind of breaker is easy, the contacts start off in the closed placement so that the circuit is entire so when a fault occurs the contacts are then simply forced apart leading to an arc to create. Oftentimes an arc can emit heat which can harm the circuit and machinery, because of this , we use the oil to evaporate heat. The oil will be converted into gas(hydrogen) and then slowly displace any oil still left, the arc will come to be extinguished when the contacts maneuver far away from each other. The OCB contacts will often acquire burnt when arcing features occurred and carbon can develop in the region around the contacts. The carbon produces the essential oil lose dielectric strength and therefore ensures that the circuit breaker is certainly less able to breaking the current. The OCB should be drained and refilled when it provides tripped, as well the contacts have to be closely inspected for losing or carbon build-up. There are two types of essential oil circuit breaker:
– Bulk Oil- This is a circuit breaker that requires larger amounts of oil in order that the arc can be extinguished. These circuit breakers can be known as ‘dead tank'(Circuit world, 2016) for the reason that tank is positioned at ground probable. If the voltage can be higher then more oil will be needed as the arc will come to be stronger and harder to extinguish. Another utilization of this circuit breaker is usually to insulate all live parts in the breaker from the planet earth.
– Minimum Oil- This circuit breaker aims to utilize the minimum required oil that is possible, instead of extinguishing the arc completely using oil in addition, it uses porcelain. The porcelain insulates the circuit breaker live parts from the earth. The chamber of the breaker can be lined with ‘bakelised’ (Circuit globe, 2016) paper, this paper has very good mechanical and electrical homes. The tube moves vertically to be able to break call, when the contacts start to separate then essential oil is forced in to the cylinder to lessen arcing.
The features of OCB’s:
– Because of the oil having a ‘substantial dielectric strength'(Circuit world, 2016) it can be utilized as
insulation once the arc has been dealt with.
– The hydrogen generated because of the evaporation of the essential oil is good for cooling the device and
– The oil creates a clearing in the conductors and the planet earth components.
The disadvantages of OCB’s:
– The oil is flammable which implies that fires are able to be started with it.
– The natural oils dielectric strength decreases due to the carbon contaminants that pollute it.
– Since the tank isn’t always surroundings tight this leaves bedroom for dangerous combination of air which could
result in explosive substances being created.
-If the container needed is large then it can be expensive.
b) Vacuum interrupter
A vacuum circuit breaker or VCB is usually a type of circuit breaker that uses a vacuum to extinguish the arc. This is most effective on weaker voltages, as bigger voltages will be also strong to extinguish. The breaker could be manufactured from steel and consists of a chamber which may be the vacuum interrupter, the material for the contacts has to be perfect as in any other case there will not be an effective connection. The use of this kind of circuit breaker is to switch HV units, they are as effective as SF6 breakers which have a big chance of leakage. The reason it is better than other circuit breakers is because when the contacts split inside vacuum they have a larger dielectric strength which builds up so that it really is thousands of times greater than normal circuit breakers.
Advantages to a VCB:
– Since there’s no material or substance inside chamber there’s no threat of fire
– They have a good service life as they have minimal parts
– Because of the fact that it doesn’t use hazardous gases or substances it really is safer for individuals to work
on and for the surroundings.
– The substitution and maintenance is much easier.
– they works extremely well repeatedly.
– There will be no gases inside which ensures that there is no place for gas emission leakage.
Disadvantages to a VCB:
– when the vacuum has been damaged, failed to extinguish the arc or loses the vacuum it cant
be repaired on internet site. This is because of the complex design and circumstances that it needs to be
– the vacuum interrupter will require ‘surge suppressors‘ (Hub webpages, January 2 2014) that are in
parallel with the stage interrupters with low currents.
– they are uneconomical if only small amounts are being made
c) HRC liquid fuse
A HRC liquid fuse can be a high voltage fuse which have a relatively high current ranking and breaking potential. This means that the fuse can be used in some high voltage applications, excessive voltage fuses need particular designs so that they are able to deal with it without breaking. There happen to be two types of HRC fuse:
Liquid type HV HRC fuse:
This kind of fuse is filled with a fluid referred to as ‘Carbon tetrachloride‘ (Circuit globe, 2016) plus they can be used for a large number of excessive voltage applications. They are able to protect circuits which may 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 made up of a glass tubing filled up with the above liquid and it has got brass caps on either end. There is also a fuse link which gets fixed to one of many caps and then the various other end is mounted on a bronze spiral fixed onto the additional cap how to write an analytical essay. When the limit of current is usually exceeded then your fuse link will come to be blown, this will retract the planting season in order that it hits a liquid detector. When the arc is established and extinguished a tiny level of gas will be produced, fuses aren’t normally used as the first protecting method for a circuit. The circuit could have additional circuit breakers, if the circuit breakers fail then the fuse will blow.
– cheaper than other circuit protecting devices
-Maintenance is not required
– Can be used in large and low voltage applications
– The operation/breaking of the fuse can be automatic
– the fuse wants be rewired or substituted when blown
– the fuse can sometimes have tripping time issues when dealing with different voltages.
Cartridge type HV HRC fuse:
This kind of fuse is very similar to low voltage fuses on the other hand you will find a specific component that means it is effective at extinguishing excessive voltage arcs. The sole difference in the look I that the cable is wound into a ring shape so that the corona effect can be avoided, the corona effect is certainly ‘the ionization of a fluid surrounding a conductor that’s electrically charged‘ (wiki customer, 2016). some applications may necessitate two fuses to be placed in parallel, one of these will have a minimal resistance and the additional a higher resistance so that the reduced resistance will blow initial and slightly reduce the pressure on the circuit when it breaks. This kind of fuse can be utilized up to 33kv because they have a breaking potential of about 8,760 A.
– They don’t deteriorate over time
– They have a high speed of operation
– No protection is required
– It really is cheaper than other methods
– They can be used for both high and low voltage applications
– After it provides blown it must be replaced
– when an arc happens it produces high temperature energy which signifies that this is a fire hazard and can
damage a number of the components inside
d) HRC expulsion fuse
This type of fuse uses gases made by the arc and its own lining to extinguish the arc, in addition, it is vented to allow gas out. The fuse website link can be encircled by liquid which turn into gas such as ‘boric acid’ (Wiki Customer, 2016) when the fuse is blown the heat from the arc will make the boric acid change into gas. The gas will quickly extinguish the arc, the gas will explosively burst out the ends of the fuse and this is the reason they must only be
used outside. There is often a type of pin so that you can manually blow all three phases in the event only one had opted. This fuse can be utilized with very high amperage and low voltage.
– No maintenance is required
– Cheaper than other types of circuit breaker
– Simple installation
– Can be risky when blown as there can be an explosive part in the process
– Damage to other devices may occur if they’re in close vicinity to the fuse at time of breaking
– Must be replaced and repaired when blown
- Produce suitably labelled diagrams and produce a detailed explanation of the ideas of operation of an inverse definite minimum amount time relay.
An inverse definite bare minimum period relay AKA IDMT relay is usually a circuit coverage device that includes an upper electromagnet which includes two windings, You will find a primary and a second. The principal winding is attached to the current transformer that is on the line that’s in need of protection and provides eight tappings. The tappings are linked to a plug which sets the bridge by the number of turns that will be used, the settings then simply can be adjusted so that required current setting may be accomplished. The secondary winding is definitely in that case energized by the induction result and is wound over the limb in the center of the upper electromagnet, it also spreads over the limbs of the lower electromagnet. There is a disc which has flux leakages, the flux leakage comes from the upper electro magnet in fact it is in stage with a disc on the low electromagnet. Te disc includes a spindle which has a moving contact that connects two of the predetermined contacts when it offers rotated into a specific position. The setting of this position or angle varies, it can vary from 0 to 360. This product operates during overload circumstances, when over current occurs this product will defend the circuit from any destruction that may be caused.
- An 11 kV three phase program evolves a 159 MVA line to line brief circuit. The system is protected by a scheme employing 500/1 ratio Current Transformer rated at 5 A good and IDMT relays. Decide 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
- Describe with the aid of diagrams the value of properly earthing apparatus.
- With the aid of diagrams describe the following ways of earth fault protection:
- Earth fault relay.
- Residual current device.
Use examples of earth fault safety at your house of work.
There are many hazards within my workplace however one of the primary how much is 500 words risks is electricity, it is crucial that I am covered from this risk as it could cause severe personal injury or fatality. To ground something methods to attach a course for the electrical current to come back to the ground safely. This will minimize the current applying us as paths, when a short circuit occurs the existing will find the simplest way back to the bottom. Here are a few main reasons for grounding all electrical equipment:
– Prevent Harm to equipment, damage or death– This is the most important reason in my
opinion since it will practically protect our lives. The most crucial aspect to do the job is safety which
means making all apparatus safe for use, we do this by earthing it and carrying out PAT testing. PAT
testing (Portable appliance screening) is in spot to make sure that the gear works and
will certainly not hurt or damage itself/others. Electricity is quite dangerous and will arc if not earthed
or correctly encased, it can cause death and injuries which could affect the rest of someone’s
– Electrical overload protection– this signifies that it will protect us from any surges that may
occur, this could be a surge in current or simply a lightning strike. If the gear is
earthed then the surge will go directly into the ground, if however it isn’t then it would go
into whatever was in touch with the equipment.
– Direction of electricity- The electricity could have a clear, safe path to the bottom which means
it is a lot safer for folks to use the equipment. The current should be able to move safely and
efficiently throughout the system without risk of hurting or damaging the circuit/person using
– Stabilization of voltage levels– Grounding also makes certain that all the currents and power are
distributed around the circuit with their proper places. This ensures that there is little room for
over current and the circuit being broken, it provides a reference stage for the voltage sources
in the circuit system.
– The earth is a good conductor– the earth is a very good conductor, the energy which is
trying to access earth will also take the route with minimal resistance. This is exactly why we are
perfect for connecting the applying to the earth, grounding the system will give the
electricity a much better path.
Grounding can be carried out individually at peoples homes by utilization of a metallic rod or extendable steel pipe that incurs the home from the underground normal water supply. There are different types of Earthing/Grounding:
– Plate type- that is a method where a little steel plate is buried only 3 meters below the housing, it really is connected to piping which is certainly then linked to the houses assistance panel.
– Pipe type- the pipe or rod will have a couple of terminals that copper conductors can hook up to, the copper conductors then will be put into the service panel for the home, this would ground the houses electric appliances.
– Strip/Wire Earthing- These are used between casings of metal equipment to earth/ground these devices or machinery. It could be attached from the casing to another little bit of metal that switches into the ground.
i) Earth Fault Relay
A relay is normally a device that is able to detect unordinary conditions within the system, it enables the right circuit breakers to trip when over current is normally detected. Most relays operate with the induction basic principle, this signifies that when the relay functions its contacts are shut in the circuit and the passage of current within the coil in the trip circuit activates a plunger. The plunger after that will activate the correct circuit breaker to trip, this implies that the region of fault in the machine is disconnected safely. This sort of relay is basically now there to trip the circuit breaker if you have a fault with the earthing pathway, this may be damaged cable or an accumulation in resistance causing unnecessary current. The induction theory consists of moving parts such as an aluminium disc fixed onto a shaft which rotates on two bearings between your poles of an electromagnet and ‘damping magnet’. The electromagnet gets wound and possesses seven taps. The seven taps will be on the front of the panel, the tap that is required could be chosen by pressing in the plug. There is a setting called the pick-up current which is often varied via the utilization of a plug multiplier. The pick-up current ideals of earth fault relays are normally quite low.
ii) Residual current system-
A residual current unit AKA an RCD is an electrical system that breaks a circuit when it senses that the current can be unbalanced or overloaded between the line and neutral conductors. The unit are far better at keeping the operator safe than fuses and circuit breakers are, they will prevent fatalities if an individual were to contact a live part. They do this as they are highly sensitive and will switch off electrically if you have any fault. They ensure that the circuit is switched off if it detects power flowing down a wrong path, this could be caused by a cut or damaged cable coming into contact with something other than the severed cable. Here are a few types of RCD’s:
– Fixed- This device can be used in consumer units and can protect a group of circuits or individual ones if that is what is required. It will defend anything in the circuit incorporating any appliances mounted on the circuit, the set RCD will give you 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. Nonetheless it wont protect the whole circuit, if somebody were to feel another the main circuit they may still get electrocuted.
– Socket-outlet- That is essentially a socket with a built in RCD, it can be used as a regular socket would be. It doesn’t protect the complete circuit, it’ll protect the equipment plugged in and the prospects, plus the person touching the gear.
– Circuit globe (2016) Essential oil Circuit Breaker [online] Available: http://circuitglobe.com/oil-circuit-breaker.html [Accessed: 21/12/2016]