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Reactance relay is preferred for phase fault on short transmission line.

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Description : For a short transmission line with r/x ratio of is 1.0, the regulation will be zero when the load power factor is

Answer : For a short transmission line with r/x ratio of is 1.0, the regulation will be zero when the load power factor is 0.707 lead

Description : what is mean by short transmission line ?

Answer : The transmission lines which have length less than 80 km is known as short transmission lines.

Description : In which fault the maximum short circuit current occurs?

Answer : In three phase bolted fault the maximum short circuit occurs.

Description : If the % reactance upto the fault point is 20%, then the short circuit current will be

Answer : If the % reactance upto the fault point is 20%, then the short circuit current will be 5 times the full load current

Answer : When a wave propagates on a transmission line, it suffers reflection several times at sending and other end.

Answer : When a transmission line is energized, the wave that propagates on it is current wave and voltage wave.

Description : In a transmission line if booster transformers are to be used, preferred location will be  (A) At the receiving end (B) At the sending end (C) At the intermediate point (D) Anywhere in the line 

Answer : In a transmission line if booster transformers are to be used, preferred location will be At the intermediate point

Answer : Impedance relays are used for phase faults on long line.

Description : State the effects of low power factor on efficiency and voltage regulation of short transmission lines. 

Answer : i) Effect of Low power factor on efficiency:- When power factor of load reduces current drawn by transmission line increases so copper losses in transmission line increases, hence transmission ... increases, so voltage drop in transmission line increases so regulation increases. (Become Poor) 

Description : If an unsymmetrical line to ground fault occurs at the secondary terminals of a delta/star, ungrounded transformer, then  (A) zero sequence currents are present on both sides of the transformer  (B) ... side  (D) zero sequence currents are present on the primary side but not on the secondary side

Answer : If an unsymmetrical line to ground fault occurs at the secondary terminals of a delta/star, ungrounded transformer, then zero sequence currents are absent on both sides of the transformer 

Description : Transmission efficiency of a transmission line increases with the

Answer : Transmission efficiency of a transmission line increases with the increase in power factor and voltage

Answer : The interaction between a transmission line and communication line is minimized by transposing transmission as well as communication lines, increasing the height of the transmission line tower, increasing the distance between the two lines.

Answer : A transmission line is protected by distance protection, time graded and current graded overcurrent protection.

Description : The sending end and receiving end voltages of a three-phase transmission line are 10 kV/ph and 9.5 kV/ph, respectively. If the resistance drop is 150 V/ph and receiving end power factor is 0.8, the sending end power factor is (A) 0.745 lagging (B) 0.775 lagging (C) 0.8 lagging (D) 0.85 lagging

Answer : Vscos¢s-Vrcos¢r=IR

Description : Explain the procedure to perform Short Circuit test on single phase transformer with circuit diagram.

Description : The armature current on symmetrical 3 phase short circuit of a synchronous machine (salient pole)  (A) has q -axis current only (B) has d -axis current only (C) has both d and q axis currents (D) cannot be divided between q and d axis currents

Answer : The armature current on symmetrical 3 phase short circuit of a synchronous machine (salient pole) has d -axis current only

Description : State the impact of inductance and resistance on transmission line performance

Answer : Impact of inductance on transmission line: 1) It causes IXL drop in transmission line which affects regulation. 2) It is the only parameter which decides power transmission capacity of line i. ... is very small, it causes losses, temperature rise& poor voltage regulation so it cannot be neglected

Description : effect of inductance and capacitance on performance of transmission line.

Answer : Following are the effect on performance of transmission line:  1. Due to inductance (L) voltage drop in transmission line produces.  2. Capacitor (C) draws charging current ... , transmission line efficiency, voltage regulation & also power factor of transmission line gets affected. 

Description : effect of line parameter on performance of transmission line. 

Answer : Following are the effect of line parameter on performance of transmission line:  1. Due to resistance (R), voltage drop in transmission line & copper losses in transmission line ... transmission line efficiency, voltage regulation & also power factor of transmission line gets affected. 

Description : A transmission line has 1 P.0 impedance on a base of 11 KV, 100 MVA. On a base of 55 KV. it will have a P.0 impedance of

Answer : A transmission line has 1 P.0 impedance on a base of 11 KV, 100 MVA. On a base of 55 KV. it will have a P.0 impedance of 0.02 P.U

Description : What is phase failure relay and how it's work?

Description : State the limitations of EHVAC transmission line. 

Answer : Following are the Limitations of EHVAC Transmission:   1. Insulation cost increases as voltage increases 2. Skin effect is more 3. Proximity effect is more. 4. Corona loss increases. 5. Radio ... 18. EHVAC is economical only for bulk amount of power is to be transmitted over long distance. 

Description : State line parameters of transmission line. 

Answer : Following are the of Line parameters of transmission line:  1. Resistance  2. Inductance  3. Capacitance

Description : While calculating performance of medium transmission line, what assumptions are made in case of (i) Nominal 'T' Method (ii) Nominal 'TT' Method. 

Answer : (i) Assumptions are made in case of Nominal 'T' Method:  a. It is assume that line capacitance is connected at center of transmission line. b. It is assume that half ... assumed that transmission line resistance & reactance per phase is connected in between two half transmission line capacitance 

Description : HVDC transmission line in India: 

Answer : HVDC transmission line in India:  S.N .  From To  Voltage 1 Rihand (U.P) (from 1990) Dadri +- 500 KV (bipolar) 2 Talcher- is the biggest ... (Chandrapur) Western Region  140KV   8 Connecting Southern region(Vizag- Gajuwaka) Eastern Region 140KV 

Description : Why is transmission line 11kV, 33kV 66kV Not Is 10kV, 20kV, 30kV ?

Answer : 10kv plus to compensate losses in olden days 1kv were added and transmitted. Since all equipment used for transmission have a multiple of 11 from olden days, still that is being followed even though the losses are ... voltages, multiples of 11 is eazy for winding ratios.. i.e. 11kv to 33kv is 1:3.

Description : A 50Ω transmission line is terminated in an impedance of 20-j50. What will be the reflection coefficient? A) 0.69 B) 1.69 C) 6.9 D) 16.9 

Answer : A 50Ω transmission line is terminated in an impedance of 20-j50. What will be the reflection coefficient? A) 0.69 B) 1.69 C) 6.9 D) 16.9 

Description : Stability of a transmission line can be increased by

Answer : Stability of a transmission line can be increased by Shunt capacitor, Series capacitor

Description : The sag of a transmission line is least affected by (A) Self weight of the conductor. (B) Temperature of the surrounding air. (C) Current through the conductor. (D) Ice deposited on the conductor.

Answer : The sag of a transmission line is least affected by Current through the conductor.

Description : A transmission line of 200 km has a certain A, B, C and D parameters. If the length is reduced to 60 km

Answer : A transmission line of 200 km has a certain A, B, C and D parameters. If the length is reduced to 60 km A increases, B decreases

Description : Series capacitive compensation in EHV transmission line is used to

Answer : To maintain voltage stability 

Description : What are the losses in a transmission line?

Description : what is mean by medium transmission line ?

Answer : The transmission line which have length between 80 km to 250 km is known as medium transmission line.

Description : what is mean by long transmission line ?

Answer : The transmission line which have length more than 250 km are known as long transmission lines.

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

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 : Reactance relay is normally preferred for protection against

Answer : Reactance relay is normally preferred for protection against earth faults

Description : Write the relation between phase and line current, phase and line voltage for Star connection.

Answer : Line voltage is equal to root three times of phase voltage and line and phase currents are equal in star connection

Description : For 11kV line the inductance per km per phase will be of the order of:  (A) 1 H (B) 0.1 H (C) 1 mH (D) 0.1 mH

Answer : For 11kV line the inductance per km per phase will be of the order of: 1 mH

Description : Explain following techniques related to energy conservation in transmission and distribution system. (i) By balancing phase currents (ii) Variable technical losses (I2R losses).

Answer : (i) Balancing Phase currents: Proper (healthy balanced) three phase loads always draw equal currents in all lines but single phase loads in the 3 phase 4 wire system or loads connected between two ... . 11) Minimize I2R losses. 12) Balance the load currents. 13) Regulate the system voltages.

Description : What is line voltage and phase voltage? Draw balanced three phase star connected system. Show all the voltages and currents.

Description : What is the difference between line and phase current?

Answer : The currents flows through phase lines is called line voltage and currents flows from phase to neutral line is called phase current

Description : What is the difference between line and phase voltage?

Answer : Line voltage  is  voltage  between two  phases R &Y  (415 v)  while  phase  voltage  is  the  voltage  between  one  phase and  a neutral  B &  N   (240 v).

Description : What is the voltage in 3 phase line?

Answer : between 430 to 440 v

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

Answer : In the induction type directional over current relay, when a short-circuit occurs in the circuit power flows in reverse direction

Description : If the fault current is 2000 A, the relay setting is 50% and CT ratio is 400:5, the plug setting multiplier will be

Answer : If the fault current is 2000 A, the relay setting is 50% and CT ratio is 400:5, the plug setting multiplier will be 10 A

Answer : The inverse definite mean time relays are used for over current and earth fault protection of transformer against internal short-circuits.

Description : Which is the most common type of fault?

Answer : Single phase to ground fault is the most common type of fault.

Description : With fault clearing time, the transient stability of a power system

Answer : With fault clearing time, the transient stability of a power system decreases

Description : To protect the power transformer (Y-Y with neutral grounded) against fault, what type of connection do the CTs have ?

Answer : To protect the power transformer (Y-Y with neutral grounded) against fault, what type of connection do the CTs have ? Δ-Δ connection

Answer : Fault diverters are basically fast switches.

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