Leading and lagging power factors are two key concepts related to the power factor in AC electrical systems. The main difference lies in the phase relationship between current and voltage: in a leading power factor, the current leads the voltage, whereas in a lagging power factor, the current lags behind the voltage. This behavior depends on the nature of the load in the circuit.What is Power Factor?Power factor is a crucial, dimensionless parameter in AC electrical systems, applicable to both s

1. Oil-Immersed Self-Cooling (ONAN)The working principle of oil-immersed self-cooling is to transfer the heat generated inside the transformer to the surface of the tank and cooling tubes through natural convection of the transformer oil. The heat is then dissipated into the surrounding environment via air convection and thermal conduction. This cooling method does not require any dedicated cooling equipment.Applicable to:Products with capacity up to 31,500 kVA and voltage level up to 35 kV;Prod

Electromagnets vs. Permanent Magnets: Understanding the Key DifferencesElectromagnets and permanent magnets are the two primary types of materials that exhibit magnetic properties. While both generate magnetic fields, they differ fundamentally in how these fields are produced.An electromagnet generates a magnetic field only when an electric current flows through it. In contrast, a permanent magnet inherently produces its own persistent magnetic field once it has been magnetized, without requirin

RTDs and Thermocouples: Key Temperature SensorsResistance Temperature Detectors (RTDs) and thermocouples are two fundamental types of temperature sensors. While both serve the primary function of measuring temperature, their operational principles differ significantly.An RTD relies on the predictable change in electrical resistance of a single metal element as temperature varies. In contrast, a thermocouple operates based on the Seebeck effect, where a voltage difference (electromotive force, EM

1 Introduction to Fault Current Limiter (FCL) TechnologyTraditional passive fault current limitation methods—such as using high-impedance transformers, fixed reactors, or split-busbar operation—suffer from inherent drawbacks, including disruption of grid structure, increased steady-state system impedance, and reduced system security and stability. These approaches are becoming increasingly unsuitable for today's complex and large-scale power grids.In contrast, active fault current li

1 Locations for Installing Fault Current Limiters (FCLs)At Generator Terminals：Installing an FCL at this location reduces the short-circuit current level in the grid during faults, minimizes mechanical and thermal stress on the generator, and consequently reduces losses in equipment and devices.At Plant Distribution Substations：Short-circuit current levels at this location are typically very high. Installing an FCL can significantly suppress fault currents.Across the Entire Busbar：When increasin

1 Bridge-Type Superconducting Fault Current Limiter1.1 Structure and Operating Principle of the Bridge-Type SFCLFigure 1 shows the single-phase circuit diagram of the bridge-type SFCL, which consists of four diodes D₁ to D₄, a DC bias voltage source V_b, and a superconducting coil L. A circuit breaker CB is connected in series with the limiter to interrupt the fault current after it has been limited. The bias source V_b provides a bias current i_b to the superconducting coil L. The voltage of V_

1 Resistive Superconducting Fault Current Limiter1.1 Operating PrincipleAs power grid scales continue to expand, the short-circuit capacity of domestic power systems is rapidly increasing, posing significant challenges to grid construction and operation. To address the problem of excessive short-circuit currents, superconducting fault current limiters (SFCLs) based on superconductivity principles are receiving growing attention. Depending on their damping characteristics when transitioning into

1 IntroductionTo meet the rapidly growing demand for electric energy, power generation, transmission, and distribution systems must develop accordingly. One of the critical issues arising from this development is the rapid increase in short-circuit currents. The rise in short-circuit currents leads to several hazards:overheating of series-connected devices along the fault path;increased transient and recovery voltages during current interruption, which may damage insulation systems;generation of

1. How to Judge Whether the Temperature Change of a Transformer is Normal or AbnormalDuring operation, losses in the transformer’s core and windings are converted into heat, causing temperature rise in various parts. This heat is dissipated through radiation, conduction, and other means. When heat generation and dissipation reach equilibrium, the temperature of each part stabilizes. Iron losses remain nearly constant, while copper losses vary with load.When inspecting a transformer, record