What is the difference between lockout of 6.6 kV and 415 V CB’s?

1 Answer

Answer :

Voltage levels.

Manual / auto reset.

Lockout relays of 415 V breakers are all Electro-magnetic type. There is no

mechanical latch. But in 6.6 kV it is of mechanical latch type relays.

Related questions

Description : What are the types of cables used in 6.6 kV and 415 V system voltages? 

Last Answer : In 6.6 kV system AC (unearthed) grade having stranded aluminium conductors cables are used. Their insulation's are as follows. 1. XLPE - Crossed linked polyethylene insulation. 2. FRLS PVC - Fire ... V grade copper or aluminium stranded cables are used. Their insulations are HR PVC and FS type. 

Description : What are the interlocks between 415 V and 6.6 kV switch gear? 

Last Answer : 6.6 kV Breaker closed cannot rack in or out. Service lever cannot move while breaker closed. Breaker cannot be closed in in-between position. 415 V Breaker door cannot be opened when breaker is ... . Breaker cannot be closed in in-between position. Breaker closed cannot be rack in or out. 

Description : Why resistance grounding preferred for less than 33 kV and more than 415 V?

Last Answer : a) To limit the earth fault current for equipment safety else, high short ckt forces dislocate in windings/bus bars etc, b) Over voltage due to arcing ground reduced c) Permits earth fault protection (not possible in ungrounded system)

Description : What are the protections used in 415 V Class II side?

Last Answer : LV to UPS 1. CTZM 2. 50 (instantaneous over current) 3. short circuit UPS to PMCC S & T 1. 51 RYB (inverse over current) 2. 27 (under voltage) 3. 51N (earth fault) From Class III to Class II tie CTZM at Class III and 51, 51N at Class II. 

Description : What are the protections used in Class III & Class IV 415 V LV side?  

Last Answer : Class III 415 V LV side 1. 51 (inverse over current) 2. 50 (instantaneous over current) 3. 27 (under voltage) 4. 51N (earth fault) 5. 64 (REF)  Class IV 415 V LV side 1. 51 RYB (inverse over current) 2. 51N (earth fault) 

Description : What are the built in protections provided in 415 V breaker?  

Last Answer : a. DINF (making current magnetic release) This consists of a laminated magnetic circuit. This is placed under the lower current terminal pole. This is provided for all the three poles. It has a core that rotates ... by a lever. It is placed in front of the breaker. Setting range is 60% to 100%.  

Description : What is the purpose of spring charging in 415 V breaker? 

Last Answer : If the breaker is to be closed and tripped manually the closing time and tripping time would vary from person to person. Also it would not be very fast. So spring charging is provided. It ... timings irrespective of the operator and its action is fast and closing and tripping time is very less. 

Description : Explain clearly the three positions in 415 V breaker. 

Last Answer : a. Service position: Power connections and control connections are available to the breaker. b. Test position: Power connections are cut off but control connections are available to the breaker and ... the breaker and in this positions both the control and power connections are not available. 

Description : The type of control circuit that will not permit automatic restarting after power is restored, following a power failure is called _____________. A. low voltage protection B. low voltage release C. overload lockout D. reduced voltage restart

Last Answer : Answer: A

Description : What is use of lockout relay in ht voltage?

Last Answer : Answer:A lock-out relay is generally placed in line before or after the e-stop switch so the power can be shut off at one central location. This relay is powered by the same electrical source as ... allows the control power for multiple machines to be locked out by the turn of a single key switch.

Description : A 100 kVA, 415 V(line), star-connected synchronous machine generates rated open circuit voltage of 415 V at a field current of 15 A. The short circuit armature current at a field current of 10 A is equal to the ... unit saturated synchronous reactance is  (A) 1.731 (B) 1.5 (C) 0.666 (D) 0.577

Last Answer : 0.6

Description : Why in DG E/F protection, we do not open class IV CB’s or supply CB’s?

Last Answer : Delta of aux. Transformer prevents E/F currents from grid into DG neutral.  

Description : What is the difference in action of lock out pressure signal on 6.6 kV and 220 kV breakers?

Last Answer : When lock out signal comes to 6.6 kV breakers the breaker will trip. Where as in case of 220 kV breakers the breaker will not trip. If the breaker is open it will be open only and can not be closed. If it is in closed condition it will be closed.

Description : The sparking voltage of the spark plug is A. 6 to 12 V B. 100 to 450 V C. 1 to 2 kV D. 20 to 30kV

Last Answer : ANSWER : D

Description : The potential difference across the gap of a spark plug ranges between a) 10-20 mV b) 10-20 V c) 10-20 kV d) 10-20 MV

Last Answer : ans a

Description : What are your opinions on the NHL lockout?

Last Answer : answer:Complete stupidity. Is this an attempt at collective suicide? I used to be a BIG hockey fan. But I can't work up any enthusiasm for a bunch of spoiled owners and spoiled players. I don't ... they ever settle. Maybe the NHL will go bust. I will not cry. This was completely self inflicted.

Description : Is the NBA lockout really worth it?

Last Answer : I hate basketball, so I find this wonderful. Now I don’t need to worry about some basketball game preempting a show I like.

Description : What's NBA lockout?

Last Answer : That's the gist of it. The players and owners are having a pissing contest about money (because, when you're a multi millionare, a couple hundred thousand dollars is really important, you know?). If they ... start, there won't be a season. Basically, the same thing that was going on with the NFL.

Description : What is the rule for equipment with a lockout tag attached?

Last Answer : A lockout tag should only be removed by the person who attached the tag in the first place. Anyone removing the tag could actually cause injury or death to an electrical/engineer working on ... safely switched off. I would sack any person who decided to remove a lockout tag without authorisation.

Description : Depreciation is defined as A) destruction of a plant in a fire accident B) loss of equipment over time due to wear and tear C) closure of a plant due to labour trouble D) closure of a plant due to lockout

Last Answer : Answer: B

Description : What is the distribution of DC control supply in CL IV, III, II- 415V and 6.6 kV?

Last Answer : Closing coil and Trip coil 2 supply from one source. Trip coil 1 supply from one source. Protections supply from one source. 

Description : How 6.6 kV-bus supply was chosen?

Last Answer : 11 kV was rejected in view of the high insulation cost with 11 kV motors. 3.3 kV was rejected, since max motor size with 3.3 kV bus is limited to 2 MW. But we are having the motors having rating more than 2 MW, which cannot suit to 3.3 kV bus. 6.6 kV bus we can start upto 5 mw size motor. 

Description : Why core balance CT is preferred over residual connected CT’s to sense earth fault in 6.6 kV feeders?

Last Answer : a) To avoid relay mal-operation due to CT saturation b) Better sensitivity is got. c) High pickup and TMS avoided in IDMT earth fault relay. 

Description : Why 2 types of earth fault relays in 6.6 kV side of transformers?

Last Answer : I – Trips 6.6 kV breakers only. It gives primary protection for 6.6 kV bus bars. I1 – Trips the both HT and LT breakers. It acts as a backup to ref and also acts as backup to bus bar earthfault relay. 

Description : What is the design basis of 6.6 kV aluminium bus bars?  

Last Answer : a) Temperature rises not exceed 90 ºC. b) Withstand short ckt stresses. c) Take care of thermal expansion. 

Description : During unit operation can we have one UT feeding both unit 6.6 kV loads? 

Last Answer : No, logically prevented.  

Description : Why 6.6 kV transformer is resistance grounded by 10 ohms and current limited to 400 A?

Last Answer : a) To reduce burning and melting in faulted switchgear or machine. b) To reduce mechanical stresses in equipment. c) To reduce the electrical hazards by stray ground fault currents in the ground ... screen in 6.6 kV XLPE (cross-linked polyethylene). Therefore the cost of the cable decreases. 

Description : What type breakers are provided in 6.6 kV buses?

Last Answer : ABB. Make, SF6 gas, 1250A and 2000A capacity circuit breakers are provided in 6.6 kV buses. 

Description : List some important loads to 6.6 kV buses. 

Last Answer : a. Auxiliary transformers. b. PHT motors. c. BFP motors.  d. CEP motors. e. CCW motors. f. Chiller motors. g. Pressuring pump motors. 

Description : What are the main sources of power supply to 6.6 kV buses? 

Last Answer : a. Unit transformer which steps down the generated voltage to 6.6 kV from the generator. b. Start up transformer, which steps down the grid voltage to 6.6 kV. 

Description : What is the minimum voltage required for starting of 6.6 kV motors?

Last Answer : Minimum 80% of rated voltage.

Description : The voltage at the two ends of a transmission line are 132 KV and its reactance is 40 ohm. The Capacity of the line is (A) 435.6 MW (B) 217.8 MW (C) 251.5 MW (D) 500 MW

Last Answer : (A) 435.6 MW

Description : Brother A and B had some savings in the ratio 5:6. They decided to buy a gift for their sister, sharing the cost in the ratio 4:5. After they bought, A is left with three-fourth of his amount, while B is left with Rs.497. Then, the value of the gift is a) 215 b) 115 c) 315 d) 415 e) None of these

Last Answer : Answer: C Let the savings of A and B are 5x, 6x and the share cost of gift are 4y, 5y respectively. According to question, For A, 5x-4y=3/4×5x =>x=16y/5 For B, 6x-5y=497 =>6×16y/5-5y=497 =>y=35 Cost of gift=4y+5y=9×35 =315

Description : Ionisation potential applied across the electrodes of electrostatic tar precipitator is around (A) 230 V AC (B) 60 KV AC (C) 230 V DC (D) 60 KV DC

Last Answer : (D) 60 KV DC

Description : Ionisation potential employed in the industrial electrostatic precipitator is of the order of (A) 30 to 70 kV DC (B) 30 to 70 kV AC (C) 230 V AC (D) 230 V DC

Last Answer : (A) 30 to 70 kV DC

Description : The underground system cannot be operated above (a) 440 V (b) 11 kV (c) 33 kV (d) 66 kV

Last Answer : (d) 66 kV

Description : Large industrial consumers are supplied electrical energy at (a) 400 V (b) 11 kV (c) 66 kV (d) 400 kV

Last Answer : (c) 66 kV

Description : The underground system cannot be operated above (a) 440 V (b) 11 kV (c) 33 kV (d) 66 kV

Last Answer : (d) 66 kV

Description : The dielectric strength of transformer oil should be (A) 100 V. (B) 5 KV. (C) 30 KV. (D) 132 KV.

Last Answer : (C) 30 KV.

Description : Compare Single phase 25 kV AC and 1500 V DC track electrification.

Last Answer : Points Single phase 25 kV AC track Electrification 1500 V DC track electrification Supply given to O/H condition 1-ph, 25KV, AC 50 Hz  600/750V-Tromways 1500/3000V urban/suburban ... track distance Less More Applications Main line services Urban and suburban area

Description : The magnetizing reactance of a 4 kV/ 400 V, 50 Hz single-phase transformer on low voltage side is 35 Ω. The magnetizing reactance on the high voltage side is (A) 0.35 Ω (B) 3.5 Ω (C) 350 Ω (D) 3500 Ω

Last Answer : 3500

Description : The dielectric strength of a vacuum or dry air is approximately ________________. A. 450 volts/inch B. 1000 volts/inch C. 20-kv/inch D. 50-kv/inch

Last Answer : Answer: C

Description : If we give 2334 A, 540V on Primary side of 1.125 MVA step up transformer, then what will be the Secondary Current, If Secondary Voltage=11 KV?

Last Answer : A. As we know the Voltage & current relation for transformer-V1/V2 = I2/I1 We Know, VI= 540 V; V2=11KV or 11000 V; I1= 2334 Amps. By putting these value on Relation540/11000= I2/2334 So,I2 = 114.5 Amps

Description : Why 1.1 kV grade cables used for 415V?

Last Answer : To take care of the both earthed / unearthed systems.  

Description : What are the levels of SF6 gas in 220 kV breaker and their significance?

Last Answer : 7 kg/cm2 - normal pressure 5.2 bar - alarm 5.0 bar - closing/tripping operation blocked. 

Description : What is the type of 220 kV circuit breaker? 

Last Answer : 220 kV, SF6 breaker, single pole, puffer type. 

Description : What are the main parts of 220 kV Circuit Breaker? 

Last Answer : Pole column filled with SF6 Pneumatic drive system with compressed air circuit Control cubicle unit 

Description : Give the details of switchyard 220 kV CB, Isolator, CT, CVT and lightning arrestor.  

Last Answer : 220 kV SF6 Circuit Breaker 1. Make - ABB 2. Air pressure blocking a. Close Block - 17.3 bar. b. Open block - 16.7 bar. c. Auto reclose block - 19 bar. 3. SF6 pressure block a. Alarm - 5. ... , storage and erection. Rated voltage : 216 kV rms. Operating voltage : 184 kV rms. 

Description : Why neutrals are solid grounded above 33 kV? 

Last Answer : a) Less transient over voltage due to arcing grounds. b) Voltage of phases are limited to phase to ground voltage. (No neutral shifting) c) Allows graded insulation of transformer (low cost) d) Fast E/F protection. 

Description : Why the earthing transformer primary voltage is 16.5 kV rated in main generator even though actual voltage during the E/F is root 3 times less?

Last Answer : The transformer should not saturate during E/F otherwise it will cause ferroresonance with the GT winding capacitance. Dangerous O/V and neutral shifting will occur. During loss of load or field ... saturation. Saturation can also occur due to point on wave of application causing flux doubling.