Description : Difference between Current Transformer (CT) and Potential Transformer (PT)
Last Answer : Current Transformers (CT) and Potential Transformers (PT) are used to measure the current and voltage in a circuit of the order of hundreds of amperes and volts respectively. A CT has large number of ... and flux density vary over a wide range whereas in PT, they vary over a limited range only
Description : What are the checks on CT & PT?
Last Answer : a) Polarity checks b) Insulation checks c) Ratio checks d) Knee point voltage (only for PS class CT)- magnetising characteristic test.
Description : What is the purpose of CT & PT?
Last Answer : For transformation of current, voltage to a lower level for the purpose of Measurement, Protection and Control.
Description : Draw a neat sketch and explain the use of CT and PT for measurement of power in a single-phase circuit?
Last Answer : If wattmeter of proper range is not available or if voltage and current ranges are high we can usr CT and PT of suitable ratio. Connect the CT and PT as shown in figure. The reading of wattmeter can be multiplied by the ratio to get the actual power.
Description : A three-phase, induction-type motor experiences an open in one phase. Which of the listed automatic protective devices will prevent the machine from being damaged? A. Overspeed trip B. Thermal overload relay C. Three-pole safety switch D. Magnetic blowout coil
Last Answer : Answer: B
Description : What is protective relay?
Last Answer : It is an electrical device designed to initiate the isolation of a part of the electrical installation, or to operate an alarm signal, in the event of abnormal condition or a fault. In ... Breaker) after sensing the fault and helps to isolate the fault system from the healthy electrical system
Description : Why CT operated over load relay is using for loads of high acceleration time upto 30 seconds? How it getting back?
Last Answer : The saturable current transformers linearly transforms the current upto twice the set current, but above this value the transformer core gets saturated and the secondary current is proportionally less. Thus ... overload. When current reduces the core gets de-saturated, as material design is such.
Description : The burden of protective Current Transformer (CT) is specified in
Last Answer : The burden of protective Current Transformer (CT) is specified in Volt - Ampere
Description : Pt. with long hix of hyperthyroidism to screen about the complication of hyperthyroidism do: liver us Ct brain Bone scan (for osteoporosis)
Last Answer : Bone scan (for osteoporosis)
Description : How can we use CT and PT for protection purpose?
Last Answer : CT and PT for Protection purpose: Current transformer (CT) and Potential transformer (PT) are instrument transformers, which are used in conjunction with protective relays for protection purpose. The CT ... from the healthy part. In this way the CT and PT can be used for protection purpose.
Description : Mention the precautions to be taken while connecting CT and PT in the circuit.
Last Answer : Precautions to be taken while using instrument transformers: 1. Secondary of CT is never kept open circuited when it is energized. 2. Secondary of PT is never kept short circuited when it ... of the instrument transformers unless they are properly grounded. 8. Never connect to DC circuits.
Description : Write any four differences between CT and PT.
Last Answer : CT PT CT corresponds to current transformer PT corresponds to potential transformer CT primary is connected in series with load and secondary winding is connected to a low range ammeter. PT ... ) x PT ratio It is a step-up transformer. It is a step-down transformer
Description : Burden of a protective relay is the power (a) required to operate the circuit breaker (b) absorbed by the circuit of relay (c) developed by the relay circuit (d) none of the above
Last Answer : (b) absorbed by the circuit of relay
Description : Define the following terms with respect to protective relays i) Relay time ii) Reset current iii) Plug setting multiplier and iv) Time setting multiplier
Last Answer : 1) Relay Time: The time interval between occurrence of fault and closure of relay contacts. 2) Reset Current: The value of current below which the relay resets and comes back to ... The adjustment arrangement provided for setting the operation time of relay is known as Time setting multiplier.
Description : Draw a neat labeled diagram to show protective system for AC traction and give the function of each relay used in it.
Last Answer : Protective system for AC traction: Function Of Each Relay: For transformer - Inverse time over current relay- as back up protection on primary (HV side) over current ... against faults near substation Under voltage relay - protection against faults far away from substation
Last Answer : Burden of a protective relay is the power absorbed by the circuit of relay.
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
Last 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 : If the fault current is 2000 A, the relay setting is 50% and CT ratio is 400:5, the plug setting multiplier will be
Last 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
Description : The following statement(s) is/are true concerning initial microbiologic diagnostic techniques. a. Appropriate expeditious transport of specimens to the microbiology laboratory is essential for obtaining accurate ... a 4-to 8-fold increase over the MIC to be considered clinically efficacious.
Last Answer : Answer: a, c, d Because most surgical infections are polymicrobial, specimens should be cultured for aerobic and anaerobic bacteria, as well as fungi. Although aerobic and aerotolerant ... fold increase over MIC during the peak serum level have been demonstrated to be clinically efficacious
Description : ct planting zone
Last Answer : Need Answer
Description : Is Danbury CT too far a location to commute to NY airports?
Last Answer : I would think that if you don’t fly all that often that 90 mins. would be acceptable.
Description : 3 Select the antiemetic that prevents activation of emetogenic afferents in the gut and their central relay in chemoreceptor trigger zone/nucleus tractus solitarious, but has no effect on gastric motility: A. Ondansetron B. Domperidone C. Metoclopramide D. Cisaprid
Last Answer : A. Ondansetron
Description : The harmonic currents in a power transformer does not cause increase in: a) Secondary voltage b) Core loss c) Copper loss d) Magnetic interference with protective relays
Last Answer : Ans: A
Description : Routine maintenance of dry-type transformers should include ______________. A. preventing the entrance of water from broken pipe lines steam lines B. keeping protective surfaces and insulating bushings free of ... debris C. periodic testing of insulation resistance with a megger D. all of the above
Last Answer : Answer: D
Description : Complete controller maintenance includes _____________. A. periodic testing of protective devices B. checking for loose or worn contacts and weak springs C. maintaining a sufficient supply of spare parts D. all of the above
Description : A commutator's protective oxide film can be destroyed by _________________. A. periods of low humidity B. very low brush current density C. improper brush grade D. all of the above
Description : A common type of protective covering used on electrical conductors is _____________. A. plain paper B. fibrous braid C. silver sheathing D. babbitt sheathing
Description : What is meant by protective angle? Give its value for reliable operation?
Last Answer : Protective angle is the vertical angle through the ground wire axis and the line passing from the ground wire axis to the outermost phase conductor. Its value for reliable protection is taken equal to 20-30 degrees
Description : What are the functions of protective relays
Last Answer : To detect the fault and initiate the operation of the circuit breaker to isolate the defective element from the rest of the system, thereby protecting the system from damages consequent to the fault.
Description : What are the protective parameters to changeover AVR auto to manual?
Last Answer : a. PT supply fail. b. Auto pulse fail. c. Supply of limiter fail. d. Supply of auto channel fail. e. Regulated supply fail. f. High auto reference.
Description : ________ dimension corresponds to two different states in the eight possible cloud forms. a) Physical location of data b) Ownership c) Security boundary d) None of the mentioned
Last Answer : None of the mentioned
Description : location of headlamp relay on 2001 Buick Century Custom
Description : Where is 2011 Ford Focus door lock relay location?
Last Answer : What is the answer ?
Description : Before servicing the device indicated as 'A' in panels #1 and #3 of the illustration, the device labeled 'CT' must __________. EL-0003 A. have the disconnected leads taped to prevent ... D. have one lead grounded to discharge static electricity for the prevention of damage to electronic components
Last Answer : Answer: C
Description : What are the errors in CT?
Last Answer : (a) Ratio error Percentage ratio error = [(Nominal ratio – Actual ratio)/Actual ratio] x 100 The value of transformation ratio is not equal to the turns ratio. (b) Phase angle error: Phase angle =180/ [(ImCos -I1Sin )/nIs]
Description : Where wound type CT used and where not used?
Last Answer : Used where low CT ratio req. Not used where high short ckt. Current exists.
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 : How CT is connecting in ckt?
Last Answer : If the primary of CT is delta connected load the CT will be in star connection and vice versa. This is because to have square root 3 time compensation.
Description : Why ICT are used?(INTERPOSING CT)
Last Answer : To correct the system primary CT errors in case of high current faults out side CT zone (ICT’s primary CT is 800/1, but in fault current may go to thousands of amps. This ICT will take care of those errors. a) Matching the ratios. b) Matching the phase angle differences.
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 : Where CT secondary of 1A we are using?
Last Answer : For long distance current transmission, to reduce the IR drop.
Description : What is the standard CT polarity?
Last Answer : Primary current enters at P1 and secondary current leaves at S2.
Description : But is it advisable to keep the secondary of CT in open conditions? Will not induce very high voltage?
Last Answer : If the CT has only one secondary winding, we should keep it always short cktd for safety, but if the CT has multiple secondary, then if one secondary voltage is kept limited by suitable loading, then the other secondary voltage is eventually limited proportionately.
Description : A CT has 2 – secondary windings. If we use only one secondary winding can we keep the unused secondary winding short circuited?
Last Answer : No. If it is short-circuited then the ratio will not get correctly. The turns of primary winding will be shared between 2 secondary windings. So the unused secondary winding should kept open.
Description : What is over voltage interturn test for CT?
Last Answer : With secondary open, pass rated current in primary for 1 min. Then check secondary for insulation.
Description : What is the operating point in the Magnetising characteristic of protection CT & measuring CT?
Last Answer : Protection CT – Operation at ankle point only. Measuring CT – Operation from ankle to knee point
Description : What are the errors of the following CT’ s 5p. 10p. 15p. At rated current?
Last Answer : 5p - 1 % Ratio error ± 60 min phase error 10p - 3 % Ratio error ± 60 min phase error 15p - 5 % Ratio error ± 60 min phase error
Description : What are the specifications of CT?
Last Answer : Protection CT - Error. Alf. KpV. Metering CT - Error. Burden. Differential CT - Class PS. Core balance or E/F CT - 5-p type. Primary current - Rating of CT - 1. 15 ( full load current ) Short time rating - 1 sec.
Description : Why CT should not be open circuited?
Last Answer : Very high voltage will be induced in secondary due to less back emf resulting in the failure of the insulation.
Description : How can you de-saturate the CT?
Last Answer : Pass ac current through the primary and vary the current from zero to maximum with secondary in shorted condition. Pass dc current in the secondary and vary it from zero to maximum.