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

1.Selection and Role of Microcomputer Integrated Protection Devices1.1 Selection of Microcomputer Integrated Protection DevicesTo ensure a microcomputer integrated protection device correctly and accurately performs its relay protection tasks, selection during design should comprehensively consider reliability, response time, maintenance and commissioning, and additional functions.Signal input for microcomputer integrated protection devices is the same as traditional relay protection: voltage an

AC contactors (with the electrical schematic code KM) are core electrical devices used to control the connection/disconnection between power supplies and loads in circuits, and they are also common equipment that electricians need to work with regularly. In practice, it is not uncommon to find that some peers make mistakes in selecting AC contactors, leading to improper sizing and subsequent persistent issues. Here, four of the most typical common mistakes are highlighted for reference.I. Over-R

AC contactors are widely used for switching and controlling power circuits. They use main contacts to open and close circuits, and auxiliary contacts to execute control commands. Main contacts typically only have normally open contacts, while auxiliary contacts often have two pairs of contacts with normally open and normally closed functions. Small-sized contactors are also frequently used as intermediate relays to work with main circuits, thereby achieving the function of remote control or cont

1.Work Environment Requirements and Safeguard MeasuresBased on technical requirements for cable equipment storage, laying, transportation, laying, transposition, testing, and cable terminations, the project owner and construction units have conducted extensive trials and implemented protective measures regarding ambient temperature, humidity, bending radius, traction control, and route optimization. These measures ensure high-voltage cable quality and on-site safety under harsh winter conditions

1.Flame-Retardant Cable Classification StandardsThe flame-retardant standard system is divided into two main categories. The first category follows the "Classification of Burning Behavior for Electric and Optical Fiber Cables" GB 31247. Cables complying with this standard system are widely used in densely populated areas such as high-speed railways and subways. This standard imposes strict requirements on parameters such as smoke density, heat release, and total smoke production, and cables typi

For a 24V switch-mode power supply branch, I used a single-pole DC circuit breaker, with the negative pole subjected to equipotential bonding (previously, I even directly used AC breakers as substitutes—the main difference being arc-extinguishing performance, but how significant can the arc be in a few-amp low-current short circuit?).During a design review, an expert stated that DC circuit breakers must be bipolar, arguing that DC has positive and negative poles, unlike AC!I'm puzzled—where is t

The installation quality of indoor load switches directly affects their operational safety and service life. It must be carried out focusing on four core principles: "safety protection, standardized wiring, mechanical compatibility, and insulation assurance." Specific precautions are as follows:1.Basic Preparation and Safety Protection Before Installation: Verify that the switch model and specifications (e.g., rated voltage, current) match the actual power distribution requirements to avoid "usi

Fuses are connected in series in a circuit. When the current through the fuse element is less than or equal to its rated current, the element will not melt. Only when the current exceeds the rated value and reaches the fusing current will the element melt. When a short circuit (or overload) current occurs in the line, the current through the fuse element exceeds the specified value, causing the element to overheat and melt, thereby automatically interrupting the circuit. This prevents damage to

In the power plants and substations of various voltage levels that we operate and maintain, high-voltage current-limiting fuses are widely used, primarily for protecting voltage transformers, small transformers, and small high-voltage motors. So why are they called high-breaking-capacity fuses? And why can't ordinary fuses be used? Today, let's learn about this topic together.High-breaking-capacity fuses, also known as high-voltage current-limiting fuses, differ from ordinary fuses in two main a

Safe operation and regular maintenance of low-voltage pole-mounted circuit breakers are essential for long-term system reliability.1. Operational Safety ProceduresOperations must be strictly regulated under dispatch control, following the "Three Tickets and Two Systems" (work permit, operation ticket, emergency repair order; read-back and supervision systems). Operation tickets must use dual equipment identifiers (e.g., "XX kV XX Line XXX Circuit Breaker") and list detailed steps and safety meas