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

Failure PhenomenonFailure Information and Operational Mode Before FailureAt 17:53:50 on May 16, 2016, the protection devices of two sets on Jingchuan II Line operated successively. Phase B was selected for tripping, and the B - phase of circuit breakers 7522 and 7520 was opened. The protection of circuit breaker 7522 detected a permanent fault on the two - circuit line protection device, with a delay of 0.6s. Subsequently, the ABC three - phase of circuit breaker 7522 tripped. During this proces

Definition: Voltage regulation (or line regulation) refers to the variation in voltage at the receiving end of a transmission line when the full load at a specified power factor is removed, with the sending-end voltage maintained constant. In simpler terms, it is thepercentage changein the load-end voltage when transitioning from no-load to full-load conditions. This parameter is expressed as a fraction or percentage of the receiving-end voltage, serving as a critical metric for assessing the st

When the current-carrying contacts of a circuit breaker separate, an arc forms and persists briefly after contact separation. This arc is hazardous due to the heat energy it generates, which can produce explosive forces.A circuit breaker must extinguish the arc without damaging equipment or endangering personnel. The arc significantly influences the breaker’s performance. Interrupting aDC arcis inherently more challenging than anAC arc. In an AC arc, the current naturally reaches zero

In an air break circuit breaker, the arc is initiated and extinguished in substantially static air as the arc moves. These breakers are used for low voltages, generally up to 15 kV, with rupturing capacities of 500 MVA. As an arc-quenching medium, air circuit breakers offer several advantages over oil, including: Elimination of risks and maintenance associated with oil use. Absence of mechanical stress caused by gas pressure and oil movement. Elimination of costs from regular oil replacement due

A fuse is a device employed in electrical circuits to protect electrical equipment against overloads and short circuits. It is the simplest and most cost-effective component for interrupting an electrical circuit when exposed to short-circuit currents or excessive overloads.Fuses are used for overload or short-circuit protection in high-voltage systems of up to 66 kV and low-voltage systems of up to 400 V. In certain applications, their use is limited to scenarios where their performance charact

A fuse is a current-interrupting device that breaks or opens a circuit by melting its element when the current in the circuit surpasses a specific value. Fuses are predominantly categorized into two types: high-voltage fuses and low-voltage fuses. Low-voltage fuses can be further divided into two subtypes: semi-enclosed or rewirable fuses, and fully enclosed cartridge fuses.Rewirable FusesRewirable fuses, commonly referred to as kit-kat fuses, are widely utilized in residential wiring and small-

High Rupturing Capacity (HRC) Fuses: Design, Operation, and ApplicationsCore FunctionalityHRC fuses are engineered to safely conduct short-circuit or fault currents for a specified duration. If the fault is cleared within this timeframe, the fuse element remains intact; otherwise, it melts to interrupt the circuit. Encased in an airtight container, the element is shielded from environmental factors while enabling efficient arc quenching.Inverse Time CharacteristicHRC fuses exhibit a criticalinve

Definition and Principle of Impedance Relay (Distance Relay)An impedance relay, also known as a distance relay, is a voltage-controlled protective device whose operation depends on the electrical distance (impedance) between the fault point and the relay’s installation position. It functions by measuring the impedance of the faulty section and comparing it with a pre-set threshold.Working Mechanism Measurement and Comparison: The relay continuously monitors line voltage (via potential

Reactance RelayA reactance relay is a high-speed relay composed of two elements: an overcurrent element and a current-voltage directional element. The current element generates positive torque, while the current-voltage directional element produces torque opposite to the current element, depending on the phase angle between the current and voltage.The reactance relay is an overcurrent relay with directional limitation. The directional element is designed to generate maximum negative torque when

Abnormal Operating Conditions and Causes of Induction MotorsThree-phase induction motors are widely used in industrial applications. Their abnormal operating conditions and causes can be summarized as follows:Abnormal Operating Conditions and Causes of Induction MotorsThe following are the abnormal operating conditions and causes of induction motors:Mechanical Overload Blockage in Pump/Gear Systems: Obstruction in mechanical systems (e.g., pumps or gears) connected to the motor. Damaged Bearings