High and low voltage systems are very important for power supply. Switchgear is a key part of these systems. There are many types of switchgear, such as 33kv ais switchgear, 33kv gis switchgear and 33kv indoor switchgear. As an ISO 9001 certified manufacturer with 17 years of experience, Zhejiang Lvma Electric Co., Ltd. (LVMA) specializes in high-quality transformers and serves global markets, so we've listed 20 easy questions and answers to help you learn basic knowledge quickly.
What is the function of the high-voltage fuse?
Answer: It protects transformers. PT is a kind of small transformer, so it also protects PT.
What is the function of the live display device?
Answer: It shows if there is high voltage in the switchgear cabinet.
What is the function of the program lock?
Answer: It controls the operation order of switchgear, and stops wrong operations.
What is the function of the grounding switch?
Answer: It is fixed at the outgoing end. When maintaining equipment, it stops high voltage power supply and keeps workers safe.
What is the function of the valve?
Answer: When the handcart is pulled out, it stops people or metal objects from touching high-voltage static contacts.
Why is the busbar covered with rubber?
Answer: It works as insulation, reduces air insulation distance, and stops small animals from causing short circuits.
What is the function of the lightning arrester? Why does each cabinet group need one?
Answer: Lightning arresters are made for different voltage levels. They absorb extra high voltage to keep lines safe.
Each cabinet group needs at least one lightning arrester. For example, it protects the inside lines of incoming cabinets, and avoids overvoltage caused by vacuum circuit breakers in outgoing cabinets. This rule also applies to 33kv ais switchgear and 33kv indoor switchgear.
What are the functions of current transformers and zero-sequence transformers?
Answer: Current transformers are used for measurement, metering and protection. Zero-sequence transformers only work for protection.
Can current transformers be installed in reverse?
Answer: No. Current normally flows from L1 to L2. If reversed, the secondary line must be redesigned.
What is the function of the humidity controller?
Answer: It checks air humidity. If humidity is too high, it heats the equipment to adjust humidity. It has automatic and manual modes. It is very useful for 33kv indoor switchgear.
What is the function of the one-time schematic diagram?
Answer: It shows the parts and connection directions of the main circuit.
What do PT and CT mean?
Answer: PT means Voltage Transformer. CT means Current Transformer.
What do AC and DC mean?
Answer: AC means Alternating Current. DC means Direct Current.
What is the function of the vacuum circuit breaker?
Answer: It can switch on and off load current. It uses a vacuum bulb to put out electric arcs.
What are the types of circuit breakers?
Answer:
(1) Vacuum Circuit Breaker: Uses vacuum to put out arcs, widely used in 10KV and 35KV systems.
(2) SF6 Circuit Breaker: Uses SF6 gas to put out arcs, with strong breaking capacity. It is the main part of 33kv gis switchgear.
(3) Air-Blast Circuit Breaker: Uses compressed air to put out arcs, for ultra-high voltage systems.
(4) Self-produced Gas Circuit Breaker: Makes gas to put out arcs, for low-voltage agricultural systems.
(5) Magnetic Blow Circuit Breaker: Uses magnetic fields to put out arcs, for low-voltage use.
What is a power transformer?
Answer: It changes voltage and current, but cannot change power. It has a closed iron core and two coils. Three-phase transformers are often used with 33kv gis switchgear.
What is a current transformer?
Answer: It has primary winding, iron core and secondary winding. The primary side connects with load in series, and the secondary side connects with ammeters. The current ratio is decided by the turns ratio of windings.
What is a voltage transformer?
Answer: It is a special transformer to measure voltage. Its structure is the same as ordinary transformers. The voltage ratio follows the turns ratio of windings.
What is a high voltage insulator?
Answer: It fixes and supports busbars and live conductors, and keeps insulation between conductors and the ground. Its surface has special skirts to increase insulation length. It fits all kinds of switchgear including 33kv ais switchgear.
These simple Q&As cover the core knowledge of high and low voltage systems and switchgear. Understanding these points helps you choose and use switchgear correctly. For more professional industry knowledge, please follow our news column.