79 Key Professional Knowledge Areas in Electrical Engineering （1-10）
【1.Why are expansion joints installed on rigid busbars?】
All objects have the property of thermal expansion and contraction. During operation, busbars can change in length due to heating. To avoid excessive stress caused by thermal expansion and contraction that could damage the busbars and supporting insulators, expansion joints are installed on rigid busbars
【2.What is a fully insulated transformer? What is a semi-insulated transformer?】
A semi-insulated transformer refers to a transformer where the main insulation near the neutral point of the winding has a lower insulation level compared to the insulation level at the end of the winding. Conversely, in a fully insulated transformer, the insulation levels at both the beginning (primary end) and the end (neutral end) of the windings are the same.
【3.What is the primary function of a transformer in a power system?】
The main role of a transformer in a power system is to transform voltage to facilitate efficient power transmission. By using a step-up transformer, voltage is increased to reduce line losses, improve economic efficiency, and enable long-distance power transmission. Step-down transformers, on the other hand, reduce high voltages to various levels required by users, meeting their needs.
【4.What are the hazards of bushing cracks? 】
Bushing cracks can reduce insulation strength, leading to further insulation damage and potentially causing complete insulation breakdown. Additionally, water inside the cracks may freeze and expand during cold weather, which could crack the bushing. Therefore, bushing cracks pose a significant threat to the safe operation of transformers.
【5.What is the function of a high-voltage circuit breaker? 】
A high-voltage circuit breaker can interrupt and connect the no-load current and load current in a high-voltage circuit under normal conditions. In the event of a system fault, it works in conjunction with protective devices and automatic systems to quickly interrupt fault currents, preventing accidents from escalating and ensuring the safe operation of the system.
【6.What is the function of a blocking filter?】
A blocking filter is an essential component for carrier communication and high-frequency protection in electrical systems. It prevents high-frequency currents from leaking into other branches, reducing high-frequency energy losses.
【7.What is the function of a current transformer?】
A current transformer reduces large currents to smaller currents at a fixed ratio, providing currents for various instruments and relay protection systems while isolating the secondary system from high voltages. This ensures the safety of personnel and equipment, simplifies and standardizes the manufacturing of instruments and relays, and improves economic efficiency.
【8.What are the wiring methods for current transformers?】
The wiring methods for current transformers include: two-phase V-shaped wiring and two-phase current differential wiring using two current transformers; three-phase Y-shaped wiring, three-phase Δ-shaped wiring, and zero-sequence wiring using three current transformers.
【9.What types of reactive power sources are there in power systems? 】
Reactive power sources in power systems include:
① synchronous generators;
② synchronous condensers;
③ shunt compensation capacitors;
④ series compensation capacitors;
⑤ static compensators.
【10.Why is a group of ZnO surge arresters installed between power capacitors and their circuit breakers? 】
Installing ZnO surge arresters prevents overvoltages that may occur during the switching operations of power capacitors, ensuring the safe operation of electrical equipment.
