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What are two methods used in most circuit breakers to protect electrical circuits?
There is a heated bimetallic strip that provides a time delay small overload protection. When its contact makes, it energizes a coil to trip the breaker. Some breakers are mechanical, though.
There is a coil that trips the breaker instantly on large overload.
Automatic and manual reset. There is another type of breaker too: the GFCI (Ground Fault Circuit Interrupter).
Fuses, breakers and Ground Fault Circuit Interrupters all protect circuits.
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How can you solve resistance to complicated circuits like diamond shaped circuits?
One way is to use Thevenin's theory and methods. Léon Charles Thévenin was a French telegraph engineer who extended Ohm's Law to the analysis of complex electrical circuits.
What are the advantages and disadvantages of oil compared to air when considering methods of arc control in circuit breakers?
Air has less quenching effects when a breaker breaks on load or on a fault. Air circuit breakers are not suggested for very high rating current and high voltage application. It is ok for Low voltage application. Oil is cumbersome to use and maintain. But Hv or EHV application oil is used for breaker quenching application. These days SF6 or vacuum circuit breakers are more popular for HV, EHV application.
How are parallel circuits and series circuits alike?
in parallel the voltage stays the same in parallell the current is shared in series the voltage is shared in series the current stays the same the main similarity between parallel and series circuits is when voltage increases, current increases.
Where do you use sequence starting methods for electrical motors?
it is used in conveyors belts.
How arc take place in circuit breaker?
All circuit breakers try to achieve the same thing: ensure that the rate of increase of dielectric strength exceeds the rate of increase of potential gradient across the gap between the separating contacts.Explained in another way, the rate at which energy is developed by the arc must be exceeded by the rate at which energy is dissipated through heat transfer.This can be achieved in numerous ways:reduction in arc temperature -which reduces vapourization of contact metals and ionisation of insulating medium.reduction in potential gradient -increasing contact separation distance.constriction of the arc -by insulating medium pressure, which reduces cross-sectional area of arc, and increases its resistance.increasing medium dielectric strength -by replacing contaminated insulation medium.speed of operation -minimising energy build up (I2Rt).utilising 'current zero' -utilising the natural cut-off point for a.c. current.All practical circuit breakers utilise a combination of the above methods.
What are the two most common methods of circuit protection in structures?
Fuses and breakers
How do circuit breakers prevent electrical fires?
Breakers limit the current on the conductor to a safe level, too many appliances plugged in. You trip a breaker, hopefully you then transfer load to another circuit. Breakers use two different methods to accomplish this, one uses a bimetallic strip and the current passes directly through, too high a current causes the strip to deflect. It acts on a mechanism much like the sear in a guns trigger, the deflection pulls the trigger causing a spring to open the contacts and turn off the circuit. Another type is thermal magnetic, current passing through the breaker causes a magnetic field to act on a coil tripping the breaker. When breakers are wired and work properly they prevent fires!Bending metal opens a switch
How can you solve resistance to complicated circuits like diamond shaped circuits?
One way is to use Thevenin's theory and methods. Léon Charles Thévenin was a French telegraph engineer who extended Ohm's Law to the analysis of complex electrical circuits.
Can circuit breakers help to prevent building fires?
Breakers limit the current on the conductor to a safe level, too many appliances plugged in. You trip a breaker, hopefully you then transfer load to another circuit. Breakers use two different methods to accomplish this, one uses a bimetallic strip and the current passes directly through, too high a current causes the strip to deflect. It acts on a mechanism much like the sear in a guns trigger, the deflection pulls the trigger causing a spring to open the contacts and turn off the circuit. Another type is thermal magnetic, current passing through the breaker causes a magnetic field to act on a coil tripping the breaker. When breakers are wired and work properly they prevent fires!Bending metal opens a switch
What is a complex circuits?
A 'complex circuit' is a category of electric circuit that encompasses any circuit that is not just a series circuit, a parallel circuit, or a series-parallel circuit. An example of a complex circuit is a bridge circuit.As you can see, such circuits are not necessarily complicated themselves; its just that they cannot be analyzed using only ohm's law and the power formula, but instead require more complicated methods like Theveninization, Kirchhoff's laws, etc. to be analyzed correctly.
Bus bar arrangements in sub station?
Burbars are the important elements in the electrical substation. Bus bars acts as nodal point in the substation which connects different incoming and outgoing circuits.Substations present in the power system performs various operations depends on the application such as stepping up the voltage, stepping down the voltage, high voltage transmission and switching stations to route the power to desired load center.Busbars in Substation:Busbars used in the substations are generally rectangular or circular cross section bars. These busbars can be either solid or hollow structures. Hollow circular cross section busbars are employes in EHV substations to reduce the corona effect.Switching Schemes:Switching schemes implies different methods employed to connect electrical circuits in the power system to transfer the electrical power in reliable manner. Switching schemes helps in deliver the electrical power to power system if any part of the system is faulty or under maintenance.Substations use different types of busbar arrangements or switching schemes depends upon the application, reliability of the supply and cost of installation. In every substations busbars plays a common role to connect different circuits. However switching is possible in the power system with the help of circuit breakers and isolators.Considerations for selection of busbar arrangement:Different types of busbar arrangements are employed based on the voltage, reliability of the supply, flexibility in transmitting power and cost. The other aspects considering in designing the busbars arrangements are:Simplicity in the designMaintenance of different elements without interruption in the power supplyFuture expansion feasibilityEconomical in cost of installation and operationDifferent busbar arrangements:Some of the switching schemes are busbar arrangements employed in the substations are listed below:Single Bus-bar arrangementDouble Main Bus-bar schemeMain and Transfer bus-bar schemeOne and half breaker schemeRing Main arrangement schemeSingle Bus-bar scheme:This is the simplest busbar scheme available which consists of single set of busbars connected to the generators, transformers and load feeders. All the feeders are connected by circuit breaker and set of isolators. This arrangement helps to remove the connecting elements (Generators, transformers, etc ) for maintenance by opening the circuit breaker contacts and further opening the isolators.Advantages:This busbar arrangement enjoys less cost of installationLess maintenancesimple operationDisadvantages:Fault on the busbar all the feeders connected to the busbars should be disconnectedwhen Busbar is under maintenance total supply and all feeders should be disconnectedLeast flexibility and reliabilitySee all 5 photosSingle busbar SchemeDouble Main Busbar Scheme:Normally in double main busbar scheme each circuit is connected to both the buses. In some cases half of the circuits can be connected and operated on each bus, in these cases bus or circuit breaker failure would cause loss to half of the circuits. In double main busbar arrangement one or two breakers can be provided for each circuit. Double main busbar and double breaker scheme provides high reliability in the case of fault or outage of one of the breaker.Advantages:Any circuit can be taken out of circuit for maintenanceFlexibility in connecting the feeder circuit to either of the busbarsDisadvantages:Most expensiveLoose circuits connected to busbar when fault occurs on the busbarDouble Busbar Single Breaker SchemeMain and Transfer Busbar SchemeMain and Transfer busbar scheme is similiar to single busbar arrangement with additional transfer bus connected. Tie circuit breaker is provided to tie both the main and transfer bus. During normal operation all the circuits are connected to the main bus. When circuit breaker connected to the circuit (transmission line) is required to trip for maintenance, tie circuit breaker connecting the main and transfer bus is closed. The relay protection for the circuits connected to the transfer bus is taken care by the tie circuit breaker.Advantages:Low initial costAny breaker can be taken of circuit for maintenanceDisadvantages:Requires one extra breaker for bus tieSwitching is somewhat complicated when breaker is under maintenanceMain and Transfer Busbar SchemeOne and Half breaker Busbar scheme:In One and half breaker scheme, two circuits are connected between the three circuit breakers. Hence One and Half breaker name was coined for this type of arrangement. Under normal operating conditions all the breakers are closed and both the busbars are energized. Any Circuit fault will trip two circuit breakers and no other circuit will be affected in this arrangement. When a busbar fault occur only breakers adjacent to busbars trips and no circuit will loose power. Two busbars can also be taken out of service with out affecting the power flow if the power source circuit ( alternator circuit) and receiving circuit (transmission line) available in the same bay.Advantages:Most flexible operation possibleHigh reliabilityBus failure will not remove any circuit from serviceDisadvantages:High costRelaying is somewhat complicated since the middle breaker must responsible for both the circuits on either direction and should operateone and Half Breaker SchemeRing busbar schemeIn this ring main busbar scheme arrangement, breakers are connected in ring and circuits are connected between the breakers. There will be same number of circuits as the number of breakers in the arrangement. During normal operation all the breakers are closed. During circuit fault two breakers connecting the circuit trips. During breaker maintenance the ring is broken but all the lines remain in service.Advantages:Low costFlexible operation for breaker maintenanceAny breaker can be taken out of service without interrupting loadPower can be fed from both the directionDisadvantages:Fault occur during maintenance will break the ringRelaying is complexBreaker failure during fault will trip one additional circuitRing Main Busbar Scheme
What are the advantages and disadvantages of oil compared to air when considering methods of arc control in circuit breakers?
Air has less quenching effects when a breaker breaks on load or on a fault. Air circuit breakers are not suggested for very high rating current and high voltage application. It is ok for Low voltage application. Oil is cumbersome to use and maintain. But Hv or EHV application oil is used for breaker quenching application. These days SF6 or vacuum circuit breakers are more popular for HV, EHV application.
How do breakers work to prevent electrical fires?
Breakers limit the current on the conductor to a safe level, too many appliances plugged in. You trip a breaker, hopefully you then transfer load to another circuit. Breakers use two different methods to accomplish this, one uses a bimetallic strip and the current passes directly through, too high a current causes the strip to deflect. It acts on a mechanism much like the sear in a guns trigger, the deflection pulls the trigger causing a spring to open the contacts and turn off the circuit. Another type is thermal magnetic, current passing through the breaker causes a magnetic field to act on a coil tripping the breaker. When breakers are wired and work properly they prevent fires!Bending metal opens a switch
Where will you use Oil Circuit Breakers?
Oil circuit breakers (OCBs) are high-voltage circuit breakers whose contacts are immersed in transformer oil, and are widely used in high-voltage electricity transmission/distribution systems. All circuit breakers, regardless of type, are overcurrent protection devices, designed to disconnect a circuit/load in the event of a persistent overload current (caused by too heavy a load) or a short-circuit fault current.There are various designs of OCB but what they all have in common is that they use a jet of oil to extinguish the high-temperature arc created between the circuit-breaker's contacts as they part in the event of a fault. In most cases, the jet of oil is caused by the expanding gas released as the arc is formed, which then forces a jet of oil between the contacts. To accurately direct the oil jet between the contacts, various devices, such as 'turbulator pots' are used.The operation of these circuit breakers is usually by a spring-press mechanism, although some use other methods may also be used.OCBs have a relatively small 'footprint' (i.e. the amount of space they occupy) because the insulating properties of the oil allow components at different potentials to be much closer together than they would be in, say, air. Operation of high-voltage circuit breakers is initiated by protection relays which are usually located inside the substation building.
Name the electrical methods for temperature measurement?
Thermocouples and resistance thermometers are both methods of electrical temperature measurements.
How does an open circuit occur?
An open circuit does not work. You need to have a complete circuit for the electrical current to flow back to its source. For example: An open circuit occurs when a series fuse blows or a connector is unplugged.
What is electricity test?
A continuity test is a simple test, used to determine whether there is a break in a circuit. This can be done, for example, using an ohmmeter which passes current through the circuit from its internal battery -a deflection (analogue meter) or a '000' reading (digital meter) indicates that there is continuity. A continuity test MUST NOT be performed on an energised circuit, as this will likely damage the ohmmeter and present a shock hazard to the user.
