Instrument Transformers interview questions and answers
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- Опубликовано: 10 сен 2024
- 132/33 KV Substation , 110 KV / 33KV Substation - Equipment List & Functions - Part 2
What is Instrument Transformers & Its advantages?
Uses of Current Transformer & Potential Transformers & Basic Connection details
Different Types of Indoor/ Outdoor CT’s & PT’s ?
Difference between CT & PT?
How is Secondary current rating of CT is choosed?
What is Burden of CT?
Testing /Maintenance of CT & PT
There are two categories 1. Metering 2. Protection type.
Metering Type - used in AC system for measurement of electrical quantities -voltage, current, power, energy, power factor, frequency.
Protection Type- used with protective relays for protection of power system.
Types of Potential Transformer-
a.Electromagnetic Voltage Transformer -
b.Capacitor Voltage Transformer -
What is Hermetically Sealing?
How is Secondary Current Rating of CT is choosen ?
Why 1 Amp secondary current is choosen for longer distance?
What is Burden Rate?
What is the most common cause of excess burden impedance?
CT Testing-
1. IR Testing -
Primary to earth by 5 KV megger
Secondary each core to earth by 500 V megger
Primary to secondary by 5 KV megger
Secondary core to core by 500 V megger
2.Polarity Test - For carrying out this test, we require one 1.5 V cell, DC analogue ammeter.
3. Ratio Test - Inject current in primary winding & measure induced secondary current for different current readings and verify with CT Ratio.
4. Knee point check for PS class core - Inject 230 V variable AC voltage in secondary core with ammeter in series. At certain stage, with 10% increase in voltage, current shoots up almost 50%. This is the Knee point voltage. After performing this test, Voltage is gradually reduced to Zero to demagnetise the CT.
5. Winding Resistance Test - Measure secondary winding resistance by microohm meter.
6. Tan Delta Measurement -Higher tan δ produces high dielectric loss that causes increase in temperature of paper insulation.
Increased value of Tan delta can be due to any of the following-
Moisture in the insulation, Contamination of oil & Internal partial discharge
PT Testing:
1.IR Testing -
2.Ratio Test - Inject A.C. variable voltage in primary winding & measure induced secondary voltage at different voltages & verify the same with PTR.
PT Maintenance:
Accuracy Class: - It is the rated ratio accuracy in percent.
Accuracy Limit Factor -ALF: It is the ratio of largest value of current to CT rated current up to which CT must retain the specified accuracy.
Example: - CT - 5P20, 5 VA, ALF = 20
It means error 5 % up to 20 times rated current for burden of 5 VA
Accuracy class 1% means max. Ratio error below 1% at rated current & burden.
CT Core Identification as per class: -
1. Class - 0.2, 0.5, and 1.0: - Metering Core
2. Class - 5P10, 5P20, etc - Backup protection core -O/C & E/F Protection
3. Class - PS: - Primary protection core -Differential, Distance, REF etc.
Appreciated sir please explain in detail about. Testing of CT and PT and also how to read SLD's of substations
Brother, substation SLD given in my previous video. Details of testing will be provided later based on response
Hello sir thanks for providing useful information, please make video on proper cable termination, proper cable lugs crimping and cable joints
Thank u brother...will provide one by one
@@allinone.4you thank you sir
Good presentation sir.
can u make one video for EOT crane maintenance and services.
Sure brother..ASAP
Topic and study materials is very but i can not understand the language,so please make video this type of topic in English or Hindi language which is usefull for other regions viewer
Brother, thanks for your comment.. Will try in future
Bro neenga w r u working now
Presently i am self employed.. previously i have around 23 years experience both in industry and Facility maintenance
Plz speak in English
Thanks brother..but if many request comes..will do for them