The correct answer is: D. All of the above
Overfluxing protection is a type of protection that is used to protect transformers from overheating. It does this by monitoring the current and voltage of the transformer and shutting it down if it detects that the transformer is overheating.
Buchholz relay is a type of protection that is used to protect transformers from internal faults. It does this by monitoring the pressure inside the transformer and shutting it down if it detects that there is a fault inside the transformer.
Overcurrent protection is a type of protection that is used to protect transformers from overloads. It does this by monitoring the current of the transformer and shutting it down if it detects that the transformer is overloaded.
Small distribution transformers are typically not provided with all of these types of protection because they are not as expensive as larger transformers and they are not as likely to experience these types of faults.
Here are some additional details about each type of protection:
- Overfluxing protection is typically provided by a device called a fluxmeter. A fluxmeter is a device that measures the magnetic flux in a transformer. If the fluxmeter detects that the magnetic flux is too high, it will send a signal to the transformer’s control system, which will then shut down the transformer.
- Buchholz relay protection is typically provided by a device called a Buchholz relay. A Buchholz relay is a device that is filled with oil. If there is a fault inside the transformer, the oil will start to flow through the Buchholz relay. The Buchholz relay will detect this flow of oil and send a signal to the transformer’s control system, which will then shut down the transformer.
- Overcurrent protection is typically provided by a device called a fuse. A fuse is a device that is designed to melt if the current flowing through it exceeds a certain value. If the fuse melts, it will open the circuit and shut down the transformer.
It is important to note that all of these types of protection are important for the safe operation of transformers. However, small distribution transformers are typically not provided with all of these types of protection because they are not as expensive as larger transformers and they are not as likely to experience these types of faults.