Explore topic-wise InterviewSolutions in .

Equipment grounding is the grounding on non-current carrying metal parts. This is done for personal safety of the operator and for the equipment safety by blowing the fuse when earth fault current flows through the fuse. 

Neutral Grounding is done to protect the equipment against arcing grounds, to protect system from lightning surges bypassing surge current through the earth and to protect against unbalanced voltage with grounds. When fault occurs the system voltage increases ♦3 times. This gives stress on the system and failure of the insulation if the neutral grounding not designed properly. 

Mainly there are three types of neutral earthing 

a) Directly 

b) Resistance 

c) Reactance 

The contact resistance should be very low for shaft earthing brush, to prevent even small current through the oil film, so used copper magnite brush or silver carbon brush. 

For above 3.3 kV and below 22 kV resistance grounding is preferred. In this voltage level capacitive ground current is not large, so reactance grounding is not used. 

For below 3.3 kV that for 415 V external resistance earthing is not necessary. Because normal earthing (plate earthing) gives 1.5Ω resistance. This limits current to E (R∅) / Ω

230/1.5=153A(Current limit without resistance). 

For above 22 kV solid or direct grounding is used. 

Reactance grounding is used where capacitive currents are large instead of resistance grounding in transmission lines, generators etc. to neutralize capacitive current by adding reactive current.  

Works on stator 

a) Hydro test (DM water at 5 kg/cm2 pressure, leak acceptable is 5% for 24 hrs). 

b) Hydro test of H2 coolers (DM water at 4 kg/cm2 for 30 seconds no leak is allowed) 

c) Pneumatic test with mask air. 

d) Drying out of stator conductor. Hot air blower is used. 

e) IR value check. 

f) Stator overhang portion inspection. 

g) Inspection of Teflon tubes and rubber grummets. 

h) Stator wedge tightness test with 200 grams hammer. 

i) Inspection of RTD’s. 

j) Maintenance of end shields. 

k) Hot air and hot water test of stator conductors to check whether flow through all stator conductors is uniform. 

l) Measurement of IR and PI value. 

m) Capacitance and tan-delta measurements. 

n) Partial discharge test. 

o) Winding resistance measurement. 

p) DC step voltage. 

q) ELCID (electromagnetic core imperfection detection) test.

Works on Rotor

a) Nitrogen leak tightness test of CC bolts at 4 kg/cm2. 

b) Inspection of rotor slots. 

c) Purge test of rotor ventillation canals. 

d) DP test on slip-ring hub to detect micro crack. 

e) DP and Ultrasonic test on retaining rings to detect any cracks. 

f) Measurement of IR and PI value. 

g) Impedance measurement. 

h) Recurrence surge oscillograph. 

i) Winding resistance measurement. 

j) Slip-ring groove cutting and machining. 

k) Patina formation. Then OCC test. 

The voltage generated in the shaft due to the leakage fluxes can circulate current through the shaft. If shaft earthing is not done the leakage current will flow through the bearings to ground and pitting of bearings will result. Hence bearing foundation and pipelines are insulated.

1. Toner is smearing or not adhering to the page 

If your printer toner is not sticking to the paper, this is usually either due to an old fuser assembly or defective toner cartridge. Before you rush to replace your toner cartridge, first try removing it and carefully shaking it side-to-side. (Not a hard shake!) Put it back inside the printer. Does that fix the problem? If that doesn’t resolve it, then a wise next step is to install fresh toner. Once you replace the toner cartridge, restart your printer. 

2. Paper Jams 

This is a common laser printer problem. Primary causes include grime, dust, worn rollers, or incorrect paper weight. The most basic way to prevent paper jams is simply through regular cleaning of your printer. Also, replace parts as needed. Finally, check the weight of paper your printer is rated for. 

3. Faded print/poor print quality 

This is caused by low toner, print density settings, or some other printer setting error. Make sure your printer isn’t set to an ink-saving or “draft” mode. 

4. Nothing is printing 

These steps may seem obvious, but seriously — verify that you actually sent the print job to the right printer. You may very well be printing dozens of documents in the next department, or to some virtual printer or document imaging software! If that was the problem, then check your printer setting on your desktop to ensure your main printer is set as your default. Next, check that there’s enough (and the correct type) of paper in the tray. While you’re at it, double check that your printer is on. It’s possible someone accidentally turned it off. Maybe the IT department did a system update that shut down the printer and never brought it back online. You never know. When in doubt and if all else fails – REBOOT. Begin by restarting your software application. If that doesn’t work, reboot your computer. Lastly, turn off your printer for a few minutes before powering it back up. You’d be surprised how many common laser printer problems can be solved with a restart. 

5. Wrong Font 

If your document is displaying a different font than what you formatted, the problem could simply be a communication error. First, go back and reprint. If the incorrect font prints again, it’s time to dig deeper. Next, check that the most updated drivers are installed. Finally, ensure the software on the computer and the printer are compatible with the selected fonts. 

6. Wrinkled paper / Skewed images 

Have a look in the paper tray. See if the paper is properly aligned inside the paper guides and tabs. If it’s just a little off, the results on the way out of the printer can be very problematic. 

7. Low toner / no toner warning 

Sorry to say, these warning messages and errors are not reliable. Even after installing a new toner cartridge, many printers will continue flashing and beeping to indicate you need to replace the toner. There is always a slight chance the cartridge itself is damaged or defective. But, in most scenarios, just resetting your printer should easily fix this annoying situation. Not everyone has an IT department or technical ‘go-to’ person for your office equipment issues. But when it comes to laser printers, it’s often not rocket science. Therefore, no special training is required to resolve.

1. Avoid loose wires, cables, and connections.

2. Assume any exposed metal is live with electricity unless otherwise verified.

3. Familiarize oneself with all ON/OFF buttons on equipment, circuit breakers, and disconnect switches of a bench.

4. Only make changes to the experimental setup when the circuit power is turned off and all power sources read zero voltage and zero current, as applicable.

5. Use wires of suitable length for their appropriate applications. Long wires or connections can cause clutter on a bench, and very short wires or connections can be too tight and may be easily disconnected.

6. Separate higher power equipment and connections from lower power equipment, such as microcontrollers, to avoid both interference and electrical interconnections between sensitive electronic devices and higher power devices.

7. Make sure that all DC power supplies, AC sources, and other power sources start from a zero voltage and zero current output or as directed in an experiment. Starting from a non-zero voltage is possible in certain applications where a voltage source should have a specific initial condition.

PT trolley should be isolated very carefully so as to isolate secondary terminals first and primary (HT) terminals next. When primary isolated the arrangement in the trolley make ground connection and HT terminal will be discharged at the drawn-out position. 

When fuse is blown the temporary earth should be done at the HT side of the fuse to replace the fuse. Because PT may be energised through secondary side.

The various protections associated with the generator, Generator transformer and Unit transformer are connected to a trip unit through trip relays 86A, 86B and 86C. 

The protective levels of generator are in three classified groups Class A, Class B and Class C protections which involve fault in the generator, Generator transformer and requires high speed clearance are grouped under Class A. These are routed through trip relays 86A. This trips generator transformer HV side breaker, generator field breaker, and LV side breaker of UT and Turbine simultaneously. 

Certain protections such as loss of excitation, negative sequence protection, overfluxing etc., can tolerate sequential tripping of turbine followed by the generator such that the entrapped steam in the turbine is fully spent before generator is tripped and reduces the risk of over speeding of the turbine. These protections are classified as Class B. These are connected to operate on trip relay 86BG. This relay initiates the tripping of turbine (closure of stop valves) and also the LV side breaker of UT through trip relay 86B1 and 86B2. After turbine stop valves are closed and the entrapped steam is spent, the output power of the generator will come down and is sensed by under power relay 32A and 32B. These interlocks are wired in series with the Class B trip relay 86B, which is wired to trip the generator breaker, generator field. Obtaining better security, the Under Power interlock circuits are duplicated. Some protections such as Bus bar differential, generator under frequency etc, requires tripping only of the 220 kV side of the generator transformer to isolate the external fault. These are classified as Class C. These protections are wired to trip relay 86C, which initiate only the tripping of the generator transformer HV side breaker. During Class C trip, the generator will come on House load mode of operation.

Generator neutral earthing is done through transformer and earth fault current is limited through resistance, which is connected across the secondary of the transformer. Generator 16.5 kV earth fault current is isolated from 220 kV through GT. Only star point of the generator is grounded. 

Covers inter-phase faults both externals to the GT and in GT. This also covers partially faults inside generator, time delayed to coordinate with 230 kV-distance protection. 

a. Speed governing. 

b. Eccentricity monitoring. 

c. Vibration monitoring. 

d. Valve position monitoring. 

e. Temperature monitoring. 

f. Pressure monitoring. 

g. Level monitoring. 

h. Gas leak monitoring. 

i. Conductivity monitoring. 

j. Flow monitoring.

Turning gear is used to run the turbine from rest to low speed and from normal running speed to low speed with the help of barring motor to eliminate the hogging and sagging of turbine because of the high temperature. 

(a). Troubleshooting

All PT’s are racked out. 

Earthing transformer grounding terminals disconnected. 

Barring gear shall be kept off.

Stator water shall be drained fully and hot air blown through conductors. 

Generator flexible lines shall be disconnected to isolate GT/UT

Correct Answer is: (c)

The tangent drawn to a line of force at any point on it must give the direction of the electric intensity at that point. Consider a point midway between any two of the charges. Here, the resultant intensity is only that due to the third charge and must point away from the third charge. This is satisfied only in the sketch (c).

Correct Answer is: (a) zero 

The ±q charges appearing on the inner surfaces of A are bound charges. As B is without charge initially and is isolated, the charges on A will not be affected on closing the switch S. No charge will flow into B.

(D) length should be increased.

Correct Answer is: (b) 5L/9

In the position of balance,

current in AB is i = ℰ/10r .

p.d. across AB is i x 9r = 9ℰ/10 .

 p.d. per unit length of AB is 9ℰ/10L .

For balance,

ℰ/2 = (AJ) 9ℰ/10L 

or AJ = 5L/9 . 

(b) ratio of potential differences will be 4/9

Correct option is  C) on

1. It was a summer morning. It was bright and fresh, quite rejuvenating. Everybody seemed quite cheerful and happy at heart.

2. Tom was assigned the work of whitewashing the fence.

3. The sight of the vast area of Aunt Polly’s unwhite-washed fence, and the fact that he would have to paint it discouraged Tom.

4.

• What he saw, took away all gladness from his heart,
• His sorrow multiplied.

The succinyl-CoA now gets converted into succinic acid in which one molecule of GTP is produced. In the next reaction ATP is synthesised from the ADP, so this is termed as substrate level phosphorylation and NAD is reduced to NADH and FAD is reduced to FADH.

a. Production of food, vaccines/ Production of primary metabolites; acids, alcohol/ Production of secondary metabolites: antibiotics/ Biotransformation reactions: enzymatic, steroids 

b. Strain improvement is done in order to maximize metabolite production by: 

•  Mutant selection : There are two methods - Physical method; Chemical Method 
• Genetic engineering

 Thymus is a greyish, flat, bilobed lymphoid organ situated above the heart and extending into the neck on the front and sites of trachea. Each lobe of thymus is surrounded by a capsule and is divided into a series of lobules, which are separated from each other by strands of connective tissue called trabeculae.

Anticoagulant system comprises four enzyme pathways whose function is to reduce thrombin production, limit its activity, or both. Plasmin is the major enzyme of the fibrinolytic system and will 'dissolve' already formed clots by degrading fibrin.

Ancylostoma duodenale is a species of the roundworm genus Ancylostoma. It is a parasitic nematode worm and commonly known as the Old World hookworm.

(1) The soil water contains extremely dilute solution of salts, that is more dilute than that of the cell sap in the root hair. 

(2) There will be more endosmosis and more water will be absorbed by the roots. 

(3) Otherwise, the concentration of cell sap in the root hair becomes high compared to water. 

(4) Then water does not enter the plant. As a result plant will not get water.

Both of the above reasons.

(b) along the eastern slopes of the Western Ghats 

Southwest monsoon wind

Distance from ocean

a) Yes, I agree 

b) The reasons are given below.

‘Idavapathi’

December, January, February

Arabian Sea branch 

Bay of Bengal branch

Arabian sea branch. The Arabian sea branch reaches the coast of Kerala by early June comes heavy rainfall in the western coastal areas. The Bay of Bengal branch of the Southwest