16 views
in Switchgear And Protection by

1 Answer

0 votes
by

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.

Related questions

1 answer 14 views

Part of the transformer which is most subject to damage from overheating is?

asked Mar 19, 2018 in Transformer by Shimroz123
1 answer 31 views

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

asked May 3, 2018 in Switchgear And Protection by Shimroz123
1 answer 40 views

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

asked Apr 29, 2018 in Switchgear And Protection by Shimroz123
1 answer 41 views

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.

asked May 8, 2018 in Switchgear And Protection by Shimroz123
1 answer 53 views

A relay used for protection of motors against overload is :  (A) Impedance relay (B) Electromagnetic attraction type (C) Thermal relay (D) Buchholz's relay

asked May 8, 2018 in Switchgear And Protection by Shimroz123
1 answer 26 views

The operating time of instantaneous relay is

asked May 3, 2018 in Switchgear And Protection by Shimroz123
1 answer 366 views

A negative sequence relay is used for protection of  (1) Generator (3) Motor (2) Transformer (4) Long Transmission lines

asked May 1, 2018 in Switchgear And Protection by Shimroz123
1 answer 48 views

What is the use of Buchholz relay in transformer?

asked Dec 17, 2017 in Switchgear And Protection by Quiz
1 answer 69 views

What is the difference between relay and contactor?

asked May 2, 2018 in Switchgear And Protection by Quiz
1 answer 20 views

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

asked Apr 30, 2018 in Switchgear And Protection by Shimroz123
1 answer 25 views

Reactance relay is normally preferred for protection against

asked Apr 29, 2018 in Switchgear And Protection by Shimroz123
1 answer 45 views

What is the difference between a switch and a relay?

asked Dec 17, 2017 in Switchgear And Protection by Quiz
1 answer 22 views

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

asked Apr 28, 2018 in Switchgear And Protection by Shimroz123
1 answer 13 views

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

asked Apr 28, 2018 in Switchgear And Protection by Shimroz123
1 answer 59 views

How do relay works ?

asked Dec 30, 2017 in Switchgear And Protection by Quiz
1 answer 24 views

Buchholz relay is used as a safety device with respect to which of the following? A) Audio transformers B) Oil filled power transformers C) Air core transformer D) None of these

asked Apr 29, 2018 in Electrical Engineering by Shimroz123
2 answers 51 views

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

asked Jun 4, 2018 in Switchgear And Protection by Shimroz123
1 answer 23 views

A reactance relay is (A) Voltage restrained directional relay (B) Directional restrained over-current relay (C) Voltage restrained over current relay (D) Directional restrained over voltage relay

asked Apr 28, 2018 in Power system by Shimroz123
1 answer 19 views

what is reverse power relay?

asked Dec 4, 2017 in Electrical Engineering by Quiz
1 answer 17 views
1 answer 24 views

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

asked May 12, 2018 in Switchgear And Protection by Shimroz123
1 answer 22 views

In induction type directional over current relay the driving torque is due to interaction of magnetic fields derived from (A) current in the potential coil (B) both voltage and current in the relay windings (C) directional element and non-directional element (D) non-directional element and the trip circuit

asked Apr 25, 2018 in Electrical Engineering by Shimroz123
0 answers 18 views

Which of the following test is carried out to ensure the sufficient strength of insulation between two or more conductors to avoid leakage between them ?   (a) Testing of insulation resistance between wiring and earth (b) Testing of insulation resistance between conductors (c) Testing of polarity of single phase switch (d) Testing of earth continuity path 

asked Apr 10, 2018 in Electrical Engineering by Shimroz123
0 answers 22 views

An IDMT relay of rating 5A, 2.2s and having a relay setting of 125% is connected to a supply circuit through a CT having a ratio of 400/5. The plug setting multiplier of IDMT relay in the event of fault current of 4000 A will be a. 5 b. 8 c. 10 d. 125

asked May 24, 2018 in Switchgear And Protection by Shimroz123
1 answer 11 views

If a relay fails to operate for a fault within its reach, it is said to

asked May 12, 2018 in Switchgear And Protection by Shimroz123
0 answers 7 views

Is electron flow out from the positive or negative terminal of the voltage source? 

asked Jul 1 by Shimroz123
0 answers 9 views

Ratio relay by using line-to-neutral voltage protect (A) 3-phase faults (B) double line faults (C) double-line-to-ground faults (D) generator bus earth faults 

asked Jun 4, 2018 in Switchgear And Protection by Shimroz123
1 answer 18 views

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

asked May 12, 2018 in Switchgear And Protection by Shimroz123
1 answer 37 views

In order to reduce the voltage surges due to current chopping and capacitive current breaking, we connect (A) A resistor across the CB contacts. (B) A capacitor across the CB contacts. (C) An inductor across the CB contacts. (D) A switch across the CB contacts

asked May 12, 2018 in Switchgear And Protection by Shimroz123
1 answer 66 views

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

asked May 20, 2018 in Switchgear And Protection by Shimroz123
1 answer 16 views

Electrical contact materials used in switches, brushes and relays must possess   (A) high thermal conductivity and high melting point  (B) Low thermal conductivity and low melting point   (C) High thermal conductivity and low melting point  (D) Low thermal conductivity and high melting point.

asked May 16, 2018 in Switchgear And Protection by Shimroz123
1 answer 10 views

Registers in which data is entered or taken out in serial form are referred as   (A) left shift register (B) right shift register (C) shift registers (D) none of the above

asked May 17, 2018 in Digital Electronics by Shimroz123
1 answer 110 views

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 

asked Jun 17, 2018 in Switchgear And Protection by Shimroz123

Welcome to electronics2electrical.com here you can ask questions related to electrical, electronics, mechanical, telecommunication, instrumentation, computer, mathematics, physics etc.
Be respectful to all the members. Do not copy and paste the answers from other websites which have copyright content. While asking question give full details about it.

Categories

Most popular tags

power motor dc circuit transformer voltage current used system phase resistance factor synchronous load ac energy induction electric generator series frequency between speed capacitor use electrical meter line difference control type mosfet transmission magnetic plant high single instrument bjt unit source advantages function diode and machine winding field define torque parallel amplifier supply shunt thyristor motors electricity arduino maximum time relay armature problem value on transformers types coil diagram state flow ratio material three formula starting direction theorem method emf operating efficiency digital wave microprocessor test instruments inductance loss measure operation connected signal low applications effect single-phase network temperature working constant losses different law wattmeter measuring compare controlled breaker drive device logic rc full switch flux wire resistivity disadvantages free of materials machines angle force converter conductor transistor gain open protection scr core measurement number bridge principle generators reactance circuits negative the friction iron loop short pole battery conservation steam resistors hysteresis computer using analog lines secondary station gate a rectifier inverter linear induced relays nuclear capacitance basic characteristics design direct work rotor electronics ammeter forces diesel damping rlc connection factors capacitors minimum insulation moving regulation running self systems air fault range main stability quality starter igbt eddy alternator ideal rl average 3-phase plants arc thermal error fuzzy biasing dielectric pressure balanced superposition errors copper rotation feedback impedance measured electronic electrons charge inductive transfer explain start off back curve over solar is three-phase tariff locomotive peak bias zener engineering commutator surge conductors rating universal potentiometer density permanent mechanical transducer capacity memory adc excitation two fuse pure harmonics application semiconductor inductor internal pmmc reaction welding resonance traction permeability breakers rms designed electromagnetic si generation brushes switching capacitive shaded rate 1 distribution resistor methods delta star oscillator reluctance simplification algebra 8085 boolean weston dynamometer insulating strength installation definition fuel heating earth units
...