Switchgear And Protection Pdf
What are the features of directional relay? The power frequency rms voltage appearing across the breaker contacts after the arc is extinguished and transient oscillations die out is called recovery voltage. Modern alternators are provided with mechanical centrifugal devices mounted on their driving shafts to trip the main valve of the prime mover when a dangerous over-speed occurs.
It also includes all devices associated with control, metering and regulating of electrical power systems. It is a mathematical tool to resolve unbalanced components into balanced components. What are the main safety devices available with transformer?
Overcurrent relays are those that operate when the current in a line exceeds a predetermined value. What is resistance switching? The restraining coil produces a bias force in the opposite direction to the operating force.
In other words systems used for switching, controlling and protecting the electrical power circuits and different types of electrical equipment are known as switchgear. If a fault occurring in a zone can be immediately detected and or isolated by a protection scheme dedicated to that particular zone. What are the problems in bus zone differential protection? Mention the advantages of field tests. This gives flexibility to the test.
Define operating time of a relay. Mention any two applications of differential relay. What are unit system and non unit system?
The operation of a relay should be fast and selective, ie, it should isolate the fault in the shortest possible time causing minimum disturbance to the system. What are the causes of bus zone faults? Sudden loss of all or major part of the load causes over-speeding in alternators. Large number of circuits, different current levels for different circuits for external faults. Differentiate between a fuse and a circuit breaker.
Difference in lengths of pilot wires on either sides of the relay. State the different types of faults. Define energizing quantity. What are the types of air blast circuit breaker? When a free electron comes and collides with a neutral gas molecule, the electron is absorbed by the neutral gas molecule and negative ion is formed.
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The degree of carbonization is increased due to smaller quantity of oil. What are the limitations of Buchholz relay? In order to limit the flow of current through neutral and earth a resistor is introduced between them. State the various types of unsymmetrical faults. This is overcome by connecting adjustable resistors to pilot wires to get equipotential points on the pilot wires.
Circuit breaker is a high current interrupting device and it act as a switch under normal operating conditions. Theoretical support and mathematical background is given in the text to support key concepts. Relays which operates whenever the current in a circuit drops below a predetermined value.
This phenomenon is called over fluxing. What are faults associated with an alternator? What is biased differential bus zone reduction? What are the merits of carrier current protection?
This arc delays the current interruption process and also generates enormous heat which may cause damage to the system or to the breaker itself. This method is known as field suppression. What is an under frequency relay? What are the various faults to which a turbo alternator is likely to be subjected? In single line to ground fault all the sequence networks are connected in series.
The switchgear has to perform the function of carrying, cistocele grado 1 pdf making and breaking the normal load current like a switch and it has to perform the function of clearing the fault in the power system. Definition of Switchgear A switchgear is a generic term which includes all the switching devices associated with power system protection.
The resistance of the pilot wires is usually less than ohms. What are over and under current relays? The switch is used to manually open and close the electrical circuit in our home and electrical fuse is used to protect our household electrical circuit from over current and short circuit faults. The dielectric strength of the oil deteriorates rapidly due to high degree of carbonization.
Top 100 Switchgear and Protection Interview Questions
In addition to this, there always an inherent phase difference between the primary and the secondary quantities and a possibility of current through the relay even when there is no fault. What are the functions of protective relays. It is the method of connecting a resistance in parallel with the contact space arc. Give the two methods of arc interruption? In addition to that, it also has the provision of metering and regulating the various parameters of electrical power systems.
The Switchgear and Protection Pdf Notes SGP Pdf Notes
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