# What is the factor of safety used for current ratings in a power installation?

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2 is the factor of safety used for current ratings in a power installation.

## Related questions

Two wattmeters are used to measure the power in a 3 -phase balanced system. What is the power factor of the load when one wattmeter reads twice the other ?  (a) 0 (b) 0.5 (c) 0.866 (d) 1

Current ratings of MCB for Air conditioners is generally used as _________. A. 10/15 Amp B. 5/10 A C. 20/25 Amp D. none of these

Which of the following is used for power factor improvement in transmission line ? (a) Three phase induction (b) An overexcited three phase synchronous motor running on no load (c) Three phase AC series motor (d) Choke

It is always economical to improve the power factor of an electric installation to (a) zero (b) unity (c) a little less than unity (d) a little more than unity

What is the power factor when a single phase watt meter operating on 200 V and 5 A for 5 hours makes 2016 revolutions and the meter constant in revolution is 420? A) 0.04 B) 1.04 C) 0.96 D) None of these

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

A single phase motor draws a current of 5 A from a 120 V, 60 Hz line. The power factor of the motor is 65%. Calculate the active power absorbed by the motor.  (A) 600 W (B) 390 W (C) 456 W (D) 650 W

An alternator is delivering rated current at rated voltage and 0.8 power-factor lagging. For delivering rated current at rated voltage and 0.8 poWer—factor leading, the required excitation will be:  (A) less  (B) more (C) more or less (D) the same

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

A capacitor used for power factor correction in single phase circuit decreases: (1) Power factor (2) Line current (3) Both line current and p.f. (4) The line current and increases p.f.

What is the power factor of a cable of loss angle “ө”?  (A) sin ө (B) cos ө (C) tan ө (D) Independent of ө

For a balanced three phase star connected load for which line voltage is 230V and per phase resistance and reactance is 6 Ohm and 8 Ohm respectively. Calculate: 1) phase voltage 2) line current 3) power factor 4) total power absorbed

State any eight safety precautions to be followed while working with an electric installation.

. If the peak transmitted power in a radar system is increased by a factor of 16, the maximum range will be increased by a factor of : (A) 2 (B) 4 (C) 8 (D) 16

For a series R -C circuit, the power factor corresponding to maximum power is (a) 0-5 lag (b) 0.5 lead (c) 0.707 lag (d) 0-707 lead

What is the power factor of purely resistive circuit.

In case of a power transformer, the no load current in terms of rated current is (1) 10-20% (2) 15-30% (3) 2-6% (4) 30-50%

In a distortion factor meter, the filter at the front end is used suppress   (A) odd harmonics (B) even harmonics (C) fundamental component (D) dc component

State the working principle and operation of Automatic power factor controller used in Transmission and Distribution system.

The power factor angle and torque angle of a salient pole synchronous generator drawing a current of 1.0 pu from a lagging load are 45o and 15o, respectively. The direct axis and quadrature axis currents, respectively, are (A) 0.5 pu, 0.866 pu (B) 0.866 pu, 0.5 pu (C) 0.707 pu, 0.707 pu (D) 0.5 pu, 0.5 pu

A synchronous generator is feeding a zero power factor (lagging) load at rated current. The armature reaction is  (A) magnetizing (B) demagnetizing (C) cross-magnetizing (D) ineffective

An electrodynamic wattmeter is not considered suitable for low power factor circuits because of (A) Inductance of voltage coil (B) Reactance of current coil (C) Power loss in voltage coil (D) Power loss in current coil

What is the percentage error when 3 resistors with ratings 100 Ω at 5%, 150 Ω at 6% and 250 Ω at 8% respectively, are connected in series? A) 6.33% B) 6.80% C) 19% D) None of these

Define: i) Elastic limit ii) Factor of safety .

Zero-sequence current is used for relaying purpose only in the case of   (a) Phase over current relay (b) Phase impedance relay (c) Ground over current relay (d) Ground impedance relay

Ratings on a capacitor are given 25 µF, 12 V. Also a plus sign is written near one of its terminals. The capacitor is: -  a) Mica capacitor b) Ceramic capacitor c) Electrolytic capacitor d) Paper capacitor

The current in a 200 mH coil increases from 2 to 5 A in 0.1 Second. What is rate of change of current? A. 30 A/s B. 20 A/s C. 10 A/s D. none of these

Capacitors for power factor correction are rated in?

The power factor of a spot welding machine is expected to be around (1) Unity (2) 0.8 lagging (3) 0.3-0.5 lagging (4) 0.8 leading

The power factor of a D.C. circuit is always?

The input of an A.C. circuit having power factor of 0.8 lagging is 40 kVA The power drawn by the circuit is?

The benefit of power factor correction in a power system is (A) lower power consumption (B) increased demand charge (C) reduced load carrying capabilities in existing lines (D) reduced voltage profile

What is the value of form factor in connection with single phase alternating supply systems ? (A) 1.01 (B) 1.11 (C) 1.21 (0) 1.31

What is the most effective way to reduce the cost of power generation in a power station?  (A) By increasing the diversity factor and decreasing the load factor (B) By increasing both the diversity factor and the load factor (C) By decreasing both the diversity factor and the load factor (D) By decreasing the diversity factor and increasing the load factor

What type of insulators are used whenever the conductors are dead ended and there is a change in the direction of transmission line?  (A) Shackle type (B) Strain type (C) Pin type (D) Suspension type

Power (P) in a 3 phase circuit with two watt meters at unity power factor is (W1 & W2 = watt meter readings)

Regulating transformers are used in power systems for control of : a) voltage b) power factor c) power flow d) all of the above

In a power generating station the Demand Factor and Load Factor are 0.5 and 0.2, respectively. If the connected load is 400 MW, the average demand is (A) 40 MW (B) 100 MW (C) 140 MW (D) 280 MW

Two wattmeter method is employed to measure power in a 3 -phase balanced system with the current coil connected in the A and C lines. The phase sequence is ABC. If the wattmeter with its current coil in A -phase line reads zero, then the power factor of the 3 -phase load will be

In a balanced 3 -phase 200 V circuit, the line current is 115.5 A. When the power is measured by two wattmeter method, one of the wattmeters reads 20 kW and the other one reads zero. What is the power factor of the load ?