Oil-immersed transformers are one of the important equipment in the power system. They often suffer from overload, short circuit and other faults, so effective protection measures are needed. Common oil-immersed transformer protection methods are as follows:
1. Differential protection
Differential protection is the main protection method for oil-immersed transformers. Differential protection determines whether there is an internal fault by comparing the difference in current on both sides of the transformer. When a winding of the transformer is short-circuited or grounded, resulting in current imbalance, the differential protection will be activated, thereby cutting off the power supply line and protecting the transformer from damage.
2. Overvoltage protection
Overvoltage protection is an effective way to prevent oil-immersed transformers from being damaged when high voltage occurs. Overvoltage protection can be divided into internal overvoltage protection and external overvoltage protection. Internal overvoltage protection is mainly achieved by setting lightning arresters on each winding of the transformer; external overvoltage protection includes grounding protection and lightning protection, which can be achieved by setting lightning arresters, capacitors and other equipment around the transformer.
3. Overload protection
Overload protection is a protection method to prevent oil-immersed transformers from being damaged under long-term overload conditions. When the transformer is overloaded, the temperature rises, which can easily lead to problems such as transformer oil bubble rupture, insulation aging, and winding burnout. Therefore, overload protection is mainly achieved through the transformer temperature controller.
4. Short-circuit protection
Short-circuit protection is a protection method to prevent oil-immersed transformers from being damaged when a short-circuit fault occurs. When the transformer is short-circuited, the current will rise instantly, which can easily lead to problems such as winding burnout and lightning arrester breakdown. Therefore, short-circuit protection is mainly achieved by setting a current limiter or current transformer in the transformer winding.