Differential protection is a type of protective relay system used to detect internal faults in a transformer. It compares the current entering the transformer with the current leaving the transformer, and if there is a significant difference, it trips the circuit to prevent damage.
Differential protection works by using two current transformers (CTs) to measure the current entering and leaving the transformer. The CTs are connected to a relay which compares the two currents. If the difference between the currents exceeds a set threshold, the relay sends a tripping signal to the circuit breaker to isolate the transformer.
Differential protection is a fast and reliable method for detecting internal faults in transformers. It can quickly isolate the faulty transformer and prevent further damage to the system. It also has a high sensitivity and can detect low-level faults that other protection systems may miss.
One of the main limitations of differential protection is that it is only effective in detecting internal faults. It cannot protect against external faults, such as lightning strikes or overloading. It also requires precise settings and coordination with other protective devices to avoid false tripping.
The type of differential protection scheme used for a transformer depends on factors such as the transformer configuration, size, and application. It is recommended to consult with a professional engineer or refer to industry standards (such as IEEE C37.91) to select the most suitable scheme for your specific transformer.