Free Expert Guides on Power Systems, Circuit Design & Electrical Troubleshooting

0 IntroductionThe application of live bypass cable working technology in distribution networks has significantly reduced power outage times caused by fault repair and planned maintenance. This technology utilizes mobile power equipment such as bypass cables, bypass load switches, and cable joints to form a miniature temporary power supply network, replacing the existing operational line to supply power to customers.Initially, this technology was primarily used for the maintenance of 10kV overhea

1. Definition of High-Voltage Cable Line Constant TestingHigh-voltage cable line constant testing refers to the systematic measurement, using specialized instruments, of electrical parameters such as resistance, inductance, capacitance, and conductance before a cable line is commissioned or after major maintenance. The aim is to obtain fundamental data characterizing the electromagnetic properties of the cable, serving as a critical testing phase that provides accurate parameter support for powe

1.Work Environment Requirements and Safeguard MeasuresBased on technical requirements for cable equipment storage, laying, transportation, laying, transposition, testing, and cable terminations, the project owner and construction units have conducted extensive trials and implemented protective measures regarding ambient temperature, humidity, bending radius, traction control, and route optimization. These measures ensure high-voltage cable quality and on-site safety under harsh winter conditions

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)

Overhead cables, due to their exposure to external environments, are subject to various influences that can lead to different types of faults. Below are some common types of faults in overhead cables and their causes:1. Mechanical Damage Caused by external forces such as falling trees, vehicle collisions, or construction accidents. Prolonged vibrations or swinging can also cause material fatigue in cables.2. Weather-Related Faults Lightning Strikes: Direct hits or nearby lightning strikes can ca

A core challenge in online cable eccentricity measurement is the cable’s high - speed motion. This requires non - contact measurement equipment that can handle cable jitter. X - ray cable eccentricimeters, based on optical transmission imaging, measure multi - layer contour dimensions to calculate the geometric center of conductors relative to insulation eccentricity. However, they have drawbacks: slow measurement speed (only a few times per second), increased errors from cable jitter,

1. Current Situation and ProblemsLow - voltage overhead cables often suffer insulation damage. Urbanization and infrastructure construction expose them to complex environments (construction, severe weather like strong winds/rains causing scratches or impacts, animal damage), easily breaking insulation layers. Long - term operation also degrades insulation due to aging, corrosion, and prolonged sunlight—e.g., cables in old communities age and crack, raising failure risks.Existing restor