Withstand voltage test is an insulation test, but it is a destructive test that can reveal insulation defects difficult to detect in non-destructive testing.The test cycle for high-voltage cables is three years, and it must be conducted after non-destructive tests. In other words, the withstand voltage test is performed only after all non-destructive tests have been passed.Most high-voltage cables used today are cross-linked polyethylene (XLPE) cables, which can have large cross-sections and cov

I. Introduction to Cable Grounding Loop CurrentCables rated 110 kV and above use a single-core structure. The alternating magnetic field generated by the operating current induces a voltage on the metallic sheath. If the sheath forms a closed circuit through the earth, a grounding loop current will flow on the metallic sheath. Excessive grounding loop current (loop current exceeding 50 A, more than 20% of the load current, or a ratio of maximum-to-minimum phase current greater than 3) not only a

1.Flame-Retardant Cable Classification StandardsThe flame-retardant standard system is divided into two main categories. The first category follows the "Classification of Burning Behavior for Electric and Optical Fiber Cables" GB 31247. Cables complying with this standard system are widely used in densely populated areas such as high-speed railways and subways. This standard imposes strict requirements on parameters such as smoke density, heat release, and total smoke production, and cables typi

I. Functions of Metallic Sheaths and Necessity of RepairThe metallic sheath of high-voltage cables is a metal shielding structure laid outside the insulation layer, including types such as lead sheaths, aluminum sheaths, and steel wire armor. Its core functions include mechanical protection (resisting external impact and compression), electrochemical corrosion protection (isolating moisture and soil pollutants), electromagnetic shielding (reducing electromagnetic interference to the environment)

Transformer design is a complex process that requires consideration of multiple factors to ensure safe and efficient operation. In addition, compliance with international and local regulations is essential to guarantee that transformers meet safety and performance standards. Below are key factors to consider in transformer design and the relevant regulations to follow:Transformer Design Factors: Voltage and Frequency: Determine the input and output voltage levels and the operating frequency. The

Transformers are critical components in power systems, and various failure modes can affect their operation. Timely identification and resolution of these failure modes are essential to prevent costly downtime and ensure system reliability. Below are some common transformer failure modes, along with methods to identify and address them: Insulation FailureIdentification: Insulation failure leads to decreased insulation resistance, which can be detected through insulation resistance testing (megge