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

1. Project BackgroundDistributed photovoltaic (PV) and energy storage projects are developing rapidly across Vietnam and Southeast Asia, yet face significant challenges:1.1 Grid Instability:Vietnam's power grid experiences frequent fluctuations (particularly in northern industrial zones). In 2023, coal power shortages triggered large-scale blackouts, resulting in daily losses exceeding USD 5 million. Traditional PV systems lack effective neutral grounding management capabilities, making equipmen

1.Neutral Point Establishment and System StabilityIn photovoltaic power stations, grounding transformers effectively establish a system neutral point. According to relevant power regulations, this neutral point ensures the system maintains certain stability during asymmetric faults, functioning like a "stabilizer" for the entire power system.2.Overvoltage Limitation CapabilityFor photovoltaic power stations, grounding transformers can effectively limit overvoltages. Generally, they can control o

1. Zero-Sequence Overcurrent ProtectionThe operating current for zero-sequence overcurrent protection of grounding transformers is typically determined based on the transformer's rated current and the maximum allowable zero-sequence current during system ground faults. The general setting range is approximately 0.1 to 0.3 times the rated current, with operating time usually set between 0.5 to 1 second to quickly clear ground faults.2.Overvoltage ProtectionOvervoltage protection is a critical com

1. High-Resistance Grounding SystemHigh-resistance grounding can limit ground fault current and appropriately reduce ground overvoltage. However, there is no need to connect a large high-value resistor directly between the generator neutral point and ground. Instead, a small resistor can be used together with a grounding transformer. The primary winding of the grounding transformer is connected between the neutral point and ground, while the secondary winding is connected to a small resistor. Ac

Grounding Transformer Winding ConfigurationsGrounding transformers are classified by winding connection into two types: ZNyn (zigzag) or YNd. Their neutral points can be connected to an arc suppression coil or a grounding resistor. Currently, the zigzag (Z-type) grounding transformer connected via an arc suppression coil or a low-value resistor is more commonly used.1. Z-Type Grounding TransformerZ-type grounding transformers come in both oil-immersed and dry-type insulation versions. Among them

Why Do We Need a Grounding Transformer?The grounding transformer is one of the most important devices in power systems, primarily used to connect or isolate the system neutral point to ground, thereby ensuring the safety and reliability of the power system. Below are several reasons why we need grounding transformers: Prevent Electrical Accidents:During the operation of a power system, abnormal conditions such as voltage leakage may occur in equipment or lines due to various reasons. If the neut

1. System Configuration and Operating ConditionsThe main transformers at Zhengzhou Rail Transit’s Convention & Exhibition Center Main Substation and Municipal Stadium Main Substation adopt a star/delta winding connection with a non-grounded neutral point operation mode. On the 35 kV bus side, a Zigzag grounding transformer is used, connected to ground through a low-value resistor, and also supplies station service loads. When a single-phase ground short-circuit fault occurs on a line, a path

Grounding transformers, commonly referred to as "grounding transformers" or simply "grounding units," operate under no-load conditions during normal grid operation and experience overload during short-circuit faults. Based on the filling medium, they are commonly categorized into oil-immersed and dry-type types; based on phase count, they can be either three-phase or single-phase grounding transformers.A grounding transformer artificially creates a neutral point for connecting a grounding resist

What is a Grounding Transformer?A grounding transformer, abbreviated as "grounding transformer," can be classified into oil-immersed and dry-type according to the filling medium; and into three-phase and single-phase grounding transformers according to the number of phases.Difference Between Grounding Transformers and Conventional TransformersThe purpose of a grounding transformer is to create an artificial neutral point for connecting an arc suppression coil or resistor when the system is conne

In China's power system, the 6 kV, 10 kV, and 35 kV grids generally adopt a neutral-point ungrounded operation mode. The distribution voltage side of main transformers in the grid is usually connected in delta configuration, which provides no neutral point for connecting grounding resistors. When a single-phase ground fault occurs in a neutral-point ungrounded system, the line-to-line voltage triangle remains symmetrical, causing minimal disruption to user operations. Moreover, when the capaciti