Which relay is more sensitive ? 1 VA or 2 VA ?
(A) 1 VA (B) 2 VA
(C) Both are equally sensitive (D) Both are insensitive
Description : With the help of neat diagram, explain operation of static relay.
Last Answer : Operation of Static Relay: Operation: 1) The solid-state component used are transistors, diodes, resistors, IC s, capacitor etc. The function of comparison and measurement are accomplished by ... ) An auxiliary dc supply is provided for operation of static relay elements as shown in figure.
Description : Describe the construction and Operation of Buchholz relay with neat labeled diagram.
Last Answer : Construction of Buchholz Relay: It takes the form of a domed vessel placed in the connecting pipe between the main tank and the conservator. The device has two elements. The upper element ... manner that it senses the sudden violent movement of oil/gas from transformer tank to conservator.
Description : Describe the operation of current differential relay with neat sketch.
Last Answer : Operation of Current Differential Relay: Figure shows an arrangement of an overcurrent relay connected to operate as a differential relay for alternator protection under fault conditon. ... current flows through relay coil, causing relay to operate for protection of alternator winding.
Description : With a neat sketch, explain the working of Thermal relay.
Last Answer : Working of Thermal Relay: 1) When the system is in normal operating condition, the heating element carries normal current from CT, this current produces heat = I2Rt. This heat ... of the spring releases which operates relay contacts resulting into providing trip signal to trip circuit.
Description : Define the following terms with respect to protective relays i) Relay time ii) Reset current iii) Plug setting multiplier and iv) Time setting multiplier
Last Answer : 1) Relay Time: The time interval between occurrence of fault and closure of relay contacts. 2) Reset Current: The value of current below which the relay resets and comes back to ... The adjustment arrangement provided for setting the operation time of relay is known as Time setting multiplier.
Description : Draw a typical time-current characteristic for IDMT relay.
Last Answer : Time-Current Characteristic for IDMT Relay:
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 Buchholz relay with neat labelled diagram.
Last Answer : Buchholz relay: The relay is located in the path of the oil from transformer tank to conservator. As seen from diagram, the upper mercury switch operates the alarm circuit due to tilting of the ... manner that it senses the sudden violent movement of oil from transformer tank to conservator.
Description : Explain MHO relay in detail.
Last Answer : MHO Relay: In this relay, poles 1, 2, 3 are energized by a voltage V through polarizing coil to produce flux, the capacitor connected provides phase shift. The left pole 4 is energized by a current which is the ... hence on the ratio (I/V) = Y i.e. admittance, hence called as MHO relay.
Description : Describe over current relay with time-current characteristic.
Last Answer : Over current relay with time-current characteristics:- 1. Definite time over current relay: Operating time is constant, the relays operates after a predetermined time when the current exceeds the pickup ... of fault current and definite time characteristics at higher values of fault current.
Description : Explain operation of µP based relay with block diagram
Last Answer : Operation of Microprocessor (µP) based relay: The inputs from the power system through CTs and PTS are received by the analog Input receiver; they are sampled simultaneously or ... compares the dynamic inputs and decides accordingly to generate trip/alarm signal to the output device.
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.
Description : The reactance relay is essentially: A) an over-voltage relay with current restraint B) an over-voltage relay with directional restraint C) a directional relay with voltage restraint D) a directional relay with current restraint
Last Answer : an over voltage relay with delay an over voltage relay with directional resistance
Description : The operation of the relay which is most affected due to arc resistance is A) Mho relay B) Reactance relay C) Impedance relay D) All are equally affected
Last Answer : The operation of the relay which is most affected due to arc resistance is Mho relay
Description : The most efficient torque — producing actuating structure for induction — type relay is:
Last Answer : The most efficient torque — producing actuating structure for induction — type relay is: induction-cup structure
Description : In a biased differential relay, the bias is defined as the ratio of A) Number of turns of restraining coil and operating coil B) Operating coil current and restraining coil current C) Faulteurrent and operating coil current D) Fault current and restraining coil current
Last Answer : In a biased differential relay, the bias is defined as the ratio of Number of turns of restraining coil and operating coil
Description : 30°, 60° and 90° connections are made in a directional relay to render the relay (A) Sufficient torque under fault conditions (B) Zero torque under fault conditions (C) Current grading (D) Time grading
Last Answer : 30°, 60° and 90° connections are made in a directional relay to render the relay Sufficient torque under fault conditions
Description : If a relay fails to operate for a fault within its reach, it is said to
Last Answer : If a relay fails to operate for a fault within its reach, it is said to Under reach
Description : The purpose of the restraining coil in a biased differential relay is (A) To reduce CT saturation during fault. (B) To increase the sensitivity of the relay. (C) To match the transformation ratio. (D) To limit the spill current through the relay during heavy external fault.
Last Answer : d
Description : If the fault current is 6000 A, the relay plug setting is 150% and the CT ratio is 400/5, the plug setting multiplier will be
Last Answer : If the fault current is 6000 A, the relay plug setting is 150% and the CT ratio is 400/5, the plug setting multiplier will be 10
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 relay has a rating of 5 A, 2.2 sec IDMT and a relay setting of 125% TMS = 0.6. It is connected to a supply circuit through a C.T. 400/5 ratio. The fault current is 4000 A. The operating current of the relay is
Last Answer : A relay has a rating of 5 A, 2.2 sec IDMT and a relay setting of 125% TMS = 0.6. It is connected to a supply circuit through a C.T. 400/5 ratio. The fault current is 4000 A. The operating current of the relay is 6.25A
Description : The operating time of instantaneous relay is
Last Answer : The operating time of instantaneous relay is 0.1 sec
Description : What is the difference between relay and contactor?
Last Answer : Relay have smaller ratings. Contactor is a high rating relay.
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 : Buchholz relay is (1) located in the conservator tank (2) located in the transformer tank itself (3) connected in the pipe connecting main tank of transformer and conservator (4) installed in the circuit breaker
Last Answer : Buchholz relay is connected in the pipe connecting main tank of transformer and conservator
Description : To prevent mal-operation of differentially connected relay while energizing a transformer, the relay restraining coil is based with (1) second harmonic current (2) third harmonic current (3) fifth harmonic current (4) seventh harmonic current
Last Answer : To prevent mal-operation of differentially connected relay while energizing a transformer, the relay restraining coil is based with second harmonic current
Description : Reactance relay is normally preferred for protection against
Last Answer : Reactance relay is normally preferred for protection against earth faults
Description : In the induction type directional over current relay, when a short-circuit occurs in the circuit (A) power flows in reverse direction (B) power flows in normal direction (C) directional power element does not operate (D) over current element is not energized
Last Answer : In the induction type directional over current relay, when a short-circuit occurs in the circuit power flows in reverse direction
Description : A solid state relay (A) withstands voltage transients (B) does not require auxiliary dc supply (C) provide low burden on CT and P (D) does not provide earth fault protection
Last Answer : A solid state relay provide low burden on CT and P
Last Answer : The torque produced in induction type relay (shaded pole structure) is inversely proportional to the square of the current.
Last Answer : Admittance relay is directional relay.
Last Answer : The relay with inverse time characteristic will operate within 5 to 10 sec.
Last Answer : The under voltage relay can be used for generators, busbars, transformers, motors.
Last Answer : Reactance relay is preferred for phase fault on short transmission line.
Last Answer : Induction cup relay is operated due to changes in current, voltage, impedance.
Last Answer : Interruption of large currents by relay requires arc suppressing blow out coils, wide separation of the opened contacts, high speed opening of contacts.
Last Answer : Overheating of relay contacts or contact born out is due to slow making and breaking of load circuit contacts, foreign matter on the contact surface, too low contact pressure.
Last Answer : A differential relay measures the vector difference between two or more similar electrical quantities.
Last Answer : Burden of a protective relay is the power absorbed by the circuit of relay.
Last Answer : In order that current should flow without causing excessive heating or voltage drop, the relay contacts should have low contact resistance, be clean and smooth, be of sufficient size and proper shape.
Last Answer : The relay operating speed depends upon the spring tension, the rate of flux built up, armature core air gap.
Description : How do relay works ?
Last Answer : Relay working like contact it is noise less
Description : What is the use of Buchholz relay in transformer?
Last Answer : This is a transformer that is used to step up and down current.
Description : What is the difference between a switch and a relay?
Last Answer : Switch is simply a mechanical contact mechanism and relay is a electromagnetic switch . Switch can be direct mechanically turn on and off but relay can be operated by energising coil .
Description : Low voltage releases as used in some shipboard motor starter and control equipment will have which of the following characteristics? A. They trip circuit contactors when the motor starts to overspeed. B. ... coil of the starter. D. They allow the motor to restart upon restoration of normal voltage.
Last Answer : Answer: D
Description : Where can we find more information for va loans?
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Description : What are your feelings regarding the VA?
Last Answer : From what I heard, it depends on the city/region. Some of the VA medical centers and hospitals have top notch doctors and top quality care, are well managed. People get seen quickly. Others are second ... get really good docs and med students in Cleveland). Sadly, not all VA facilities are as good.
Description : What jelly from W Va would make a good companion for a journey across the oceans to the Far East, so she could blow the doggy door off the 30K mansion?
Last Answer : Congratulations lady!! A well deserved 30K! You beat me to it, but I’ll always have 20k!
Description : What is that high pitched screeching noise occasionaly heard in Virginia Square in Arlington VA?
Last Answer : answer:I'm guessing lawyers being questioned on their billable hours, but I haven't heard your noise, so I can't say for certain. Maybe if you can describe it in more detail, such as time of day, ... wide range. (You should have heard my sisters years ago when I would look at them in the car.)