Interested to Buy Any Domain ? << Click Here >> for more details...
What is the purpose of SOTF being used inspite of distance
Protection given?
- 7 Answers
- 50183 Views
- Alstom, I also Faced
- E-Mail Answers
Answer Posted / ofa khoirun niam
Dear Engineers,
SOTF also known as Switch On To Fault is one of the protection type feature. How it works? Let's see this. During closing or energization on the line in which fault is happening within 20 ms from CB closing, then SOTF feature will clear the fault by opening the CB as instantaneously manner, even if the fault is happen in the zone 1 or zone 2. When the faults happens after 10 or 20ms, CB will opened instantaneously by Line Distance Zone 1 feature when the fault location in Zone 1 or CB tripped with time delay 300 ms to 500 ms when the fault happens in Zone 2.
This type of protection schemes are mostly working while re energizing the line after maintenance if earth switch not opened at other end of line (or maybe another fault happens) . Normally this will be in Zone 2 of distance as Zone 1 will cover only for 80% of line so in this case SOTF will act faster than distance.
Why SOTF should be provided and why distance (21L) feature could not be used. Because there is no impedance could be detected by Distance (due to CB in opening position, no current is flowing). And also there is no line voltage when the fault is caused by earthing switch (ES) in closed position in the opposite Substation, maybe missing by operator forgot to open the ES.
Wthout SOTF feature, line protection could not operate to trip the CB, even breaker failure also will no work or not be initiated. It very possible to resulting in time delay around 20ms until Line distance working properly. massive unit instability maybe occur.
So, SOTF is one of the feature relay should be tested during commissioning the HV Substation Protection Relay. I hope my explanation could be very easy to be understood. CMIIW
Best Regards,
Ofa Khoirun Ni'am
Electrical Engineer
| Is This Answer Correct ? | 5 Yes | 0 No |
Post New Answer View All Answers
what id a dry type transformers and its function ?
Explain (in simple ) - root mean square. whats its role in electrical fundamandal.where its used
Why the unit sizes of hydro generating machines are not standardized as in case of thermal powerplants?
how to calculate the step resistance for slipring induction motor,how you deside the no of step for that?
How each of the following losses occur in d.c machines (i) copper (2)core (3) windage (4)friction please help me
Why back emf used for a dc motor? Highlight its significance.
What is primary and backup protection?
which stabilizer is better ? AVR, Servo Stabilizer, Static stabilizer etc & why explain it
In constant power region of 3-phase IM torque-speed characteristics, if frequency increases flux A does not alter B decreases C increases D none of above
What are the advantages of nichols chart?
can u please mail me the syllabus for GET exam for damodar valley corporation?
State nyquist stability criterion.
what is the difference between electrical choke and electronic choke?
15hp motor wound by 0.9mm & 0.95mm magnet wire. at no load test it draw 4.2A current. Another motor with same condition draw 9.2A current. How can that occur? pls help
WHAT IS DIFFERENCE BETWEEN CAPACITOR AND CAPACITANCE?
