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

When performing switching operations, operating personnel must carefully verify that the circuit breaker is indeed in the open position. For three-pole interlocked isolating switches, all three phases must move simultaneously, with a maximum allowable vertical discrepancy of no more than 3 mm, before any opening or closing operation of the isolating switch is permitted.1. Key Points for Closing an Isolating SwitchFor manual operation, operating personnel should first remove the interlock pin bef

In substations, the number of isolating switches is generally 2 to 4 times that of circuit breakers. Due to their large quantity, the workload for installation and commissioning is considerable. For voltage levels below 110 kV, the GW4-type isolating switch serves as the dominant equipment. If the installation workmanship and mechanical dimensional adjustments of the isolating switch do not meet requirements, issues such as incomplete opening/closing, overheated contacts, or even porcelain insul

Application of Isolating Switches in Generator Neutral Grounding Resistor CabinetsIsolating switches are commonly installed in NS-FZ generator neutral grounding resistor cabinets. They provide a clearly visible disconnection point, ensuring the safety of maintenance and testing personnel. However, as high-voltage devices without arc-quenching capability, isolating switches must only be operated when the circuit is de-energized—i.e., under no-load conditions.The primary function of an isolating s

How to Select Low-Voltage Electrical Apparatus: Two Key Principles and Four Important ConsiderationsWhen selecting low-voltage electrical devices, two fundamental principles must be followed: safety and economy. Additionally, there are several critical factors to consider. Those unfamiliar with the process should refer to the guidelines below.I. Two Core Principles for Selecting Low-Voltage Electrical Apparatus Safety PrincipleThe selected low-voltage devices must operate accurately and reliably

Single-phase grounding, line break (open-phase), and resonance can all cause three-phase voltage unbalance. Correctly distinguishing among them is essential for rapid troubleshooting.Single-Phase GroundingAlthough single-phase grounding causes three-phase voltage unbalance, the line-to-line voltage magnitude remains unchanged. It can be classified into two types: metallic grounding and non-metallic grounding. Inmetallic grounding, the faulted phase voltage drops to zero, while the other two phas

Definition of Islanding EffectWhen the utility grid power supply is interrupted due to faults, operational errors, or scheduled maintenance outages, distributed renewable energy generation systems may continue operating and supplying power to local loads, forming a self-sustained “island” that is beyond the control of the utility company.Hazards Caused by Islanding Effect Loss of Voltage and Frequency Control: The utility cannot regulate voltage and frequency within the islanded section. If thes

The selection principles and precautions for fuse-switch disconnectors are crucial to ensuring the safe and stable operation of power systems.Selection Principles for Fuse-Switch Disconnectors Rated Voltage:The rated voltage of the fuse-switch disconnector shall be equal to or greater than the rated voltage of the electrical system to ensure the equipment operates normally without damage. Rated Current:The selection of rated current should be based on the load conditions of the electrical system

Essential Rules for Three-Level Power Distribution System Design1.Hierarchical and Branch Circuit Distribution(1) Power distribution from the primary main distribution board (distribution cabinet) to secondary distribution boards can be branched; that is, one main distribution board may supply power via multiple branch circuits to several secondary distribution boards.(2) Similarly, power distribution from a secondary distribution board to tertiary switch boxes can also be branched; that is, one

1.Reasonable Use of TransformersTransformers should be selected with flexible winding configurations according to the power consumption characteristics of industrial enterprises, and load adjustments should be made promptly based on each transformer’s load rate to ensure operation at optimal loading conditions. Three-phase loads on transformers should be kept as balanced as possible; unbalanced operation not only reduces output capacity but also increases losses. Energy-efficient transformers sh

Transformer Longitudinal Differential Protection: Common Issues and SolutionsTransformer longitudinal differential protection is the most complex among all component differential protections. Misoperations occasionally occur during operation. According to 1997 statistics from the North China Power Grid for transformers rated 220 kV and above, there were 18 incorrect operations in total, of which 5 were due to longitudinal differential protection—accounting for approximately one-third. Causes of