Transformer protection

Temperature relays protect dry-type transformers from overheating by monitoring the temperature of the winding and core using PTC thermistor sensors or Pt 100 (RTD) sensors. RTD (Resistance Temperature Detector) and PTC (Positive Temperature Coefficient) are two different types of thermistors used for temperature measurement, which differ in their properties and applications.

RTD:

It utilizes the change in resistance in a metal (e.g., platinum) depending on the temperature.
It exhibits a linear increase in resistance with increasing temperature.
They provide high accuracy and stability in temperature measurement.
They are often used in applications where high measurement accuracy is required, such as laboratories, pharmaceutical, and chemical industries.

PTC:

It uses a polymer thermistor with a positive temperature coefficient of resistance.
The resistance increases sharply with increasing temperature above a certain point known as the switching temperature.
They are used for protection against overheating as self-regulating elements.
Applications include surge protection, heating, and electrical control.