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

Analysis and Handling of DC System Grounding Faults in SubstationsWhen a DC system grounding fault occurs, it can be classified as single-point grounding, multi-point grounding, loop grounding, or reduced insulation. Single-point grounding is further divided into positive-pole and negative-pole grounding. Positive-pole grounding may cause misoperation of protection and automatic devices, while negative-pole grounding may lead to failure to operate (e.g., relay protection or tripping devices). On

We all know that a voltage transformer (VT) must never operate short-circuited, while a current transformer (CT) must never operate open-circuited. Short-circuiting a VT or opening the circuit of a CT will damage the transformer or create hazardous conditions.From a theoretical standpoint, both VTs and CTs are transformers; the difference lies in the parameters they are designed to measure. So why, despite being fundamentally the same type of device, is one prohibited from short-circuit operatio

Q:What are the Operating Sequence Rules for the Secondary Miniature Circuit Breaker and High-Voltage Power Supply During Voltage Transformer De-energizing and Energizing?A:For busbar voltage transformers, the principle for operating the secondary miniature circuit breaker during de-energizing and energizing is as follows: De-energizing:First, open the secondary miniature circuit breaker, then disconnect the high-voltage power supply of the voltage transformer (VT). Energizing:First, energize the

I. Permissible Operating Conditions for Current Transformers Rated Output Capacity: Current transformers (CTs) must operate within the rated output capacity specified on their nameplate. Operation beyond this rating reduces accuracy, increases measurement errors, and causes inaccurate meter readings, similar to voltage transformers. Primary Side Current: The primary current may continuously operate up to 1.1 times the rated current. Prolonged overload operation increases measurement errors and m

I. Normal Operation of Voltage Transformers A voltage transformer (VT) may operate long-term at its rated capacity, but under no circumstances should it exceed its maximum capacity. The secondary winding of a VT supplies high-impedance instruments, resulting in a very small secondary current, nearly equal to the magnetizing current. The voltage drops across the leakage impedances of both primary and secondary windings are therefore very small, meaning the VT operates close to no-load under norma

Optimization Measures for Rectifier System EfficiencyRectifier systems involve numerous and diverse equipment, so many factors affect their efficiency. Therefore, a comprehensive approach is essential during design. Increase Transmission Voltage for Rectifier LoadsRectifier installations are high-power AC/DC conversion systems requiring substantial power. Transmission losses directly impact rectifier efficiency. Increasing the transmission voltage appropriately reduces line losses and improves r

Thermal Relays for Motor Overload Protection: Principles, Selection, and ApplicationIn motor control systems, fuses are primarily used for short-circuit protection. However, they cannot protect against overheating caused by prolonged overloading, frequent forward-reverse operation, or undervoltage operation. Currently, thermal relays are widely used for motor overload protection. A thermal relay is a protective device that operates based on the thermal effect of electric current, and is essentia

General Overview of Automatic Reclosing ModesTypically, automatic reclosing devices are categorized into four modes: single-phase reclosing, three-phase reclosing, composite reclosing, and disabled reclosing. The appropriate mode can be selected based on load requirements and system conditions.1. Single-Phase ReclosingMost 110kV and higher transmission lines employ three-phase single-shot reclosing. According to operational experience, over 70% of short-circuit faults in high-voltage overhead li

I. Management Regulations for Trenchless Construction of MPP Power ConduitsIn power engineering, cable installation often employs trenchless techniques such as "pulling pipe" or "pipe jacking" due to routing constraints, construction schedules, and other objective factors. While trenchless methods offer advantages like minimal traffic disruption and shorter construction periods, they also present safety and management challenges. This is because trenchless technology remains relatively new for p

"Selecting a High-Quality Motor" – Remember the Six Key Steps Inspect (Look): Check the motor’s appearanceThe motor’s surface should have a smooth, even paint finish. The nameplate must be properly installed with complete and clear markings, including: model number, serial number, rated power, rated current, rated voltage, allowable temperature rise, connection method, speed, noise level, frequency, protection rating, weight, standard code, duty type, insulation class, manufacturing date, and ma