Voltage transformer is an important device for detection and protection in power system. It has the following important functions:

1.1 Convert the system high voltage into standard low voltage (10Ov) to supply the necessary voltage for surface protection.

1.2 Cooperate with the detection surface to detect the phase voltage and line voltage of the circuit; cooperate with the relay protection equipment to provide overvoltage and single-phase grounding protection for the system and equipment.

1.3 Isolating primary and secondary equipment protects personnel and equipment. Because voltage transformers play such a crucial role, installing appropriate protective devices (high-voltage fuses) is essential. High-voltage fuses are economical and provide a certain level of reliability. Their simple structure makes them easy to maintain and overhaul, making them widely used in systems up to 35kV.

Voltage transformers are typically connected to the high-voltage grid via disconnectors and high-voltage fuses. In systems of 110 kV and above, the corresponding voltage transformers utilize single-phase cascade insulation, which provides a large insulation margin. Furthermore, these systems often have a directly grounded neutral point, preventing equipment on each phase from receiving line voltage for extended periods and prohibiting grounding. Therefore, the primary side of the voltage transformers in 110 kV and above systems is not equipped with fuses, but is connected directly to the grid via disconnectors. In distribution systems of 380 kV and below, since high-voltage fuses meet system operating requirements, voltage transformers can be connected directly to the grid without disconnectors.

The 35kV system plays a crucial role in the power grid designed and constructed by our bureau. However, the high-voltage fuses in its voltage transformers frequently blow, making replacement a laborious and time-consuming task, increasing potential safety hazards and requiring urgent improvement. This article reviews the high-voltage fuses in 35kV voltage transformers and proposes solutions for their improvement.