The type of backup protection scheme widely used in the field is Remote backup
Last Answer : Discrimination between main and back up protection is provided by the use of relays which are slow.
Description : Primary and Backup Protection
Last Answer : Primary and Backup Protection B,D,G,I are the primary protection. A,C,H,J are the backup protection. About 90% of faults are clear by Primary Protection. So ... ordinated backup (primary is at various station and backup is at control room with computer)
Description : Explain the “Differential Protection Scheme” used for alternators with neat labeled diagram.
Last Answer : Differential Protection Scheme for Alternator: Figure shows the differential protection provided to 3 phase alternator. Here identical CTs are placed on both sides of 3 phase alternator and ... causing its operation. Relay sends trip signal to the CB, thereby alternator circuit is tripped.
Description : Explain with neat sketch, the Pilot wire protection scheme applied to transmission line.
Last Answer : Pilot Wire Protection scheme of Transmission Line : Figure shows the single line diagram of Merz price voltage balance system for pilot wire protection of three phase transmission line. ... through the relay, which gives trip signal to the circuit breaker for protection of transmission line.
Description : Explain differential protection scheme for busbars with neat sketch.
Last Answer : Differential Protection Scheme for Bus bar: Under normal conditions, the sum of the currents entering the bus bar zone is equal to those leaving it and no current flows through the relay ... of these currents will flow through the relay coil causing opening of circuit breaker of bus-bar.
Description : Discuss in brief the principle of distance protection and state four advantages of distance protection scheme.
Last Answer : Advantages: 1. System is economical 2. High speed of interruption 3. Suitable for very long and high voltage transmission lines. 4. No problem of pilot wires.
Description : List two limitations of Differential-Protection scheme for transformer.
Last Answer : Limitations of Differential Protection Scheme of Transformer: 1) Due to the magnetization characteristics of the CTs used, the ratio errors change with respect to the circulating currents. 2) ... & improper operation. 5) Inrush of magnetizing current may lead to inadvertent operation.
Description : Explain fault bus protection scheme.
Last Answer : Fault bus protection of busbar: In this scheme, the substation is so designed that every fault on the bus bar is converted to earth fault. Under normal operating conditions, there is no current flowing ... This results in operation of relay to actuate trip coil of CB to trip the circuit.
Description : A loss of excitation protection scheme for large generating unit employs A) under frequency relays B) offset Mho relay C) reactance relay D) percentage differential relay
Last Answer : A loss of excitation protection scheme for large generating unit employs offset Mho relay
Description : Which type of protection is provided on a generator to protect against stator insulation failure? A) Differential protection B) Overcurrent relay C) Thermocouple actuated alarm D) Reverse power relay
Last Answer : Which type of protection is provided on a generator to protect against stator insulation failure? A) Differential protection B) Overcurrent relay C) Thermocouple actuated alarm D) Reverse power relay
Description : What is the backup protection available for an alternator?
Last Answer : Overcurrent and earth fault protection is the backup protections.
Description : Why auto transfer is prevented if the backup protection is operated?
Last Answer : The back up protection is supposed to operate in case of a bus fault. Hence the auto transfer is prevented.
Description : State two requirements of transmission line protection.
Last Answer : Requirements of Transmission Line Protection: 1) Faults on lines should be quickly detected to initiate actions to maintain system stability. 2) For very long lines the protection system must be capable ... backup protection in the event of failure of circuit breaker (nearest to fault) to operate.
Description : Explain differential protection of busbar.
Last Answer : Differential protection Scheme for bus bar: Under normal conditions the sum of the currents entering the bus bar zone is equal to those leaving it and no current flows through the relay ... . The difference of these currents will flow through the relay coil causing opening of circuit breaker.
Description : Explain over-current protection of transformer.
Last Answer : Over-Current Protection of Transformer: Simple over-current & earth fault protection of transformer against external shortcircuit and excessive overloads is shown in the above figure. The ... trip command to the circuit breaker and the transformer is disconnected from load or fault.
Description : Explain negative phase sequence protection of alternator.
Last Answer : Negative phase sequence protection of alternator: Unbalanced loading on alternator mainly causes the negative sequence currents which generate the negative sequence components of magnetic fields. These fields ... components due to unbalance and operates the relay which further operates CB.
Description : Explain distance protection of transmission line with neat sketch diagram.
Last Answer : Distance protection of Transmission line: Distance protection scheme uses impedance relay. The relay operation is based on the impedance (or distance) between the relay and point of fault. Figure shows ... than ZL and impedance relay operates which operates the CB and line is protected.
Description : Write down limitation of differential protection of transformer.
Last Answer : Limitations of differential protection of transformer: 1) Due to the magnetization characteristics of the CTs used, the ratio errors change with respect to the circulating currents. 2) The pilot wires ... current (higher imbalance) due to which accuracy of sensing & operation is decreased.
Description : How can we use CT and PT for protection purpose?
Last Answer : CT and PT for Protection purpose: Current transformer (CT) and Potential transformer (PT) are instrument transformers, which are used in conjunction with protective relays for protection purpose. The CT ... from the healthy part. In this way the CT and PT can be used for protection purpose.
Description : For complete protection of a three-phase line: A) three Phase relays and three Earth fault relays are required B) three Phase relays and two Earth fault relays are required C) two Phase relays and two Earth fault relays are required D) two Phase relays and one Earth fault relay are required
Last Answer : For complete protection of a three-phase line: two Phase relays and one Earth fault relay are required
Description : For the protection of parallel feeders fed from one end, the relays used are: A) non-directional relays at the source-end and directional relays at the load-end B) non-directional relays at both the ... at the source-end and non-directional at the load-end D) directional relays at both the ends
Last Answer : For the protection of parallel feeders fed from one end, the relays used are: non-directional relays at the source-end and directional relays at the load-end
Description : For complete protection ofa 3— phase line: (1) Three phase and three—earth fault relays are required (2) Three phase and two—earth fault relays are required (3) Two phase and two—earth fault relays are required (4) Two phase and one-earth fault relays are required
Last Answer : For complete protection ofa 3— phase line: Two phase and one-earth fault relays are required
Description : Blind spot is a point in the zones of protection where
Last Answer : Blind spot is a point in the zones of protection where No protection is available.
Description : A relay used for protection of motors against overload is : (A) Impedance relay (B) Electromagnetic attraction type (C) Thermal relay (D) Buchholz's relay
Last Answer : D
Description : A negative sequence relay is used for protection of (1) Generator (3) Motor (2) Transformer (4) Long Transmission lines
Last Answer : A negative sequence relay is used for protection of Generator
Description : For protection of rotating machines against lightning surges _______ is used. (1) lightning arrester (2) capacitor (3) combination of lightning arrester and capacitor (4) lightning conductor and arrester
Last Answer : For protection of rotating machines against lightning surges combination of lightning arrester and capacitor is used.
Description : Reactance relay is normally preferred for protection against
Last Answer : Reactance relay is normally preferred for protection against earth faults
Description : Surge absorbers are used for protection against
Last Answer : Surge absorbers are used for protection against low voltage high frequency oscillations
Last Answer : Protection by fuses is generally not used beyond 100 A .
Last Answer : A fuse in a motor circuit provides protection against short-circuit and overload.
Last Answer : Overfluxing protection is recommended for generator transformer of the power plant.
Last Answer : Over voltage protection is recommended for hydro-electric generators, steam turbine generators, gas turbine generators.
Last Answer : The inverse definite mean time relays are used for over current and earth fault protection of transformer against internal short-circuits.
Last Answer : The single phasing relays are used for the protection of three phase motors.
Last Answer : For the protection of power station buildings against direct strokes the requirements are interception, conduction and dissipation.
Last Answer : The delay fuses are used for the protection of motors.
Last Answer : H.R.C. fuses provide best protection against short-circuits.
Last Answer : A thermal protection switch can protect against overload.
Description : What parameters or technical particulars are important to be considered while designing protection scheme of the transformer?
Last Answer : 1.Network Diagram showing the position of the transformer in the system 2.kVA or MVA rating of the transformer 3.Fault Level at the transformer 4.Voltage Ratio 5.Winding Connections 6.Per Unit ... Oil Filled 11.Length and area of cross section of the connecting leads between CTs and Relay Panel
Description : Mention the short comings of Merz Price scheme of protection applied to a power transformer.
Last Answer : In a power transformer, currents in the primary and secondary are to be compared. As these two currents are usually different, the use of identical transformers will give differential current, and ... turn-ratio are used, the differential current may flow through the relay under normal condition.
Description : Give protection scheme used for 25kV catenary protection for AC traction.
Last Answer : Protection Scheme Used for 25kV Catenary Protection for AC Traction: As shown in the figure below the scheme consists of 1) MHO relay that makes use of the impedance phase angle to get proper ... adjustment. 2) Over current relay. 3) Under voltage relay for low voltage protection.
Description : A series resistance is added to the over-current relay in a bus bar differential protection scheme which: a. Helps to develop some voltage across it which otherwise should appear across the relay and is ... the effects of CT saturation and lowers the pickup value of the relay d. All of the above
Last Answer : A series resistance is added to the over-current relay in a bus bar differential protection scheme which: a. Helps to develop some voltage across it which otherwise should appear across the relay and is ... the effects of CT saturation and lowers the pickup value of the relay d. All of the above
Description : Laser technology has been widely used in the field of a) neurology b) astrology c) ophthalmology d) psychology
Last Answer : c) ophthalmology
Description : Scheme for testing the field performance of hrbicidies in rice, wheat and sugarcane in different states of India by ICAR was initi ated in a). 1948 b). 1952 c). 1956 d). 1960
Last Answer : b). 1952
Description : 1. If the current in the core decreases, what will the strength of the magnetic field be? 2. What is the commonly used unit for measuring the speed of data transmission? 3. The Govt. of ... flows between the Vindhya and Satpura ranges? 20. Which was a journal brought out by Abul Kalam Azad ?
Last Answer : Answer : 1. Decreases 2. Bits per second 3. Jeevan Sathi Yojana 4. Because warm and cold currents meet 5. Ranga II 6. Fatty tissue 7. Uttar Pradesh 8. Oil gas 9. Silvassa 10. Hunter 11. Sports ... 16. Speaker 17. Because of inadequate supply of air 18. Growth of GNP 19. Narmada 20. Al -Hilal
Description : Sri Arvind Kejriwal has been selected for the Ramon Magsaysay Award for 2006 for his important contribution in the field. (1) Formation of Pani (water Panchayats in Rajasthan helping rural people in ... citizens to fight corruption. (4) Extending education to children of slum dwellers in Delhi.
Last Answer : ‘Right to Information’ movement and empow7ering citizens to fight corruption.
Description : Agronomy is a branch of Agriculture that deals with – a) Breeding of crop plants b) Principles of field management c) Principles and practice of crop production d) Protection of crops from Diseases and Pests
Last Answer : c) Principles and practice of crop production
Description : ……. is a type of backup in which only the data that changed, since last backup is saved. -Technology
Last Answer : Differential backup is a type of backup in which only the data that changed since the last backup is saved.
Description : Explain operation of balanced beam type relay.
Last Answer : Balanced Beam Type Relay: Under normal operating condition the current through relay coil is such that the beam is held in the horizontal position by the spring. When the fault occurs on the system the ... becomes greater than pick-up value and beam is attracted to close the trip circuit.
Description : Explain construction and operation of induction type directional over current relay.
Last Answer : Directional overcurrent relay: Construction: It consists of two units: i) Non-directional Over-current unit ii) Directional power unit The directional unit consists of upper electromagnet ... closes the trip circuit. This operates circuit breaker which isolates the faulty section.