1 Classification of Neutral Grounding Methods for Solar Photovoltaic Power StationsInfluenced by differences in voltage levels and grid structures across regions, the neutral grounding methods of power systems are mainly categorized into non-effective grounding and effective grounding. Non-effective grounding includes neutral grounding via arc suppression coils and neutral ungrounded systems, while effective grounding comprises neutral solid grounding and neutral grounding via resistors. The sel

In a neutral-insulated three-phase power system, an earthing transformer provides an artificial neutral point, which can be solidly earthed or earthed via reactors/arc suppression coils. The ZNyn11 connection is typical, where zero-sequence magnetomotive forces in the inner/outer half-windings of the same core column cancel out, balancing fault currents in series windings and minimizing zero-sequence leakage flux/impedance.Zero-sequence impedance is critical: it determines fault current magnitud

The neutral grounding mode refers to the connection between the power system neutral point and ground. In China's 35 kV and below systems, common methods include ungrounded neutral, arc-suppression coil grounding, and small-resistance grounding. The ungrounded mode is widely used as it allows short-term operation during single-phase grounding faults, while small-resistance grounding has become mainstream for its fast fault removal and overvoltage limitation. Many substations install grounding tr

With the expansion of power system scale and the cableization process of urban power grids, the capacitive current in 6kV/10kV/35kV power grids has significantly increased (generally exceeding 10A). As power grids at this voltage level mostly adopt neutral ungrounded operation mode, and the distribution voltage side of main transformers is usually in delta connection, lacking a natural grounding point, the arc during ground faults cannot be reliably extinguished, necessitating the introduction o

The equivalent circuit diagram of any device can be extremely useful for predicting how the device will behave under different operating conditions. It is essentially a circuit - based depiction of the equations that describe the device's performance.The simplified equivalent circuit of a transformer is constructed by representing all of the transformer's parameters on either the secondary side or the primary side. The equivalent circuit diagram of the transformer is presented below:Let the equi

Transformer Operation Under Load ConditionsWhen a transformer is under load, its secondary winding connects to a load, which can be resistive, inductive, or capacitive. A current I2 flows through the secondary winding, with its magnitude determined by the terminal voltageV2and load impedance. The phase angle between the secondary current and voltage depends on the load characteristics.Explanation of Transformer Load OperationThe operational behavior of a transformer under load is detailed as fol

Transformer Vector Group DefinitionThe transformer vector group denotes the phase difference between the primary and secondary sides of a transformer, while also defining the arrangement of high-voltage and low-voltage windings in three-phase transformers. Vector groups are determined by the connection configurations of three-phase transformers, which can be categorized into four main groups based on the phase difference between corresponding line voltages of the high-voltage and low-voltage sid

Definition of Parallel Magnetic CircuitA parallel magnetic circuit is defined as a magnetic pathway with two or more branches for magnetic flux, analogous to a parallel electric circuit. Such circuits feature multiple flux paths with varying cross-sectional areas and materials, each potentially composed of different magnetic components.Parallel Magnetic Circuit AnalysisThe figure above depicts a parallel magnetic circuit, where a current-carrying coil is wound around the central limb AB. This co

Background of Transformer EMF Equation DerivationWhen a sinusoidal voltage is applied to the transformer's primary winding, an alternating flux ϕmis induced in the iron core. This sinusoidal flux links both primary and secondary windings, with its functional form described by a sine function.Mathematical Derivation of Flux Rate of ChangeThe following outlines the derivation of the transformer's EMF equation, with defined parameters:ϕm: Maximum flux (Weber)f: Supply frequency (Hz)N1: Number of pr

No-Load Operation of TransformerWhen a transformer operates under no-load conditions, its secondary winding is open-circuited, eliminating load on the secondary side and resulting in zero secondary current. The primary winding carries a small no-load currentI0​, comprising 2 to 10% of the rated current. This current supplies iron losses (hysteresis and eddy current losses) in the core and minimal copper losses in the primary winding.The lag angle ofI0​is determined by transformer losses, with th