Are you puzzled about the function of each switchgear cabinet? Don’t worry, you’re not alone. From industrial plants to commercial centres, there are numerous types, each with an array of components and intricate terminology. We will thoroughly discuss switchgear components and their functions, and explain them in simpler terms so that you know exactly how they operate. So, keep reading!
1) What is a switchgear?
An electric switchgear is essentially an electrical device that regulates, safeguards, and isolates electrical systems. It automates the control and flow of electricity, ensuring everything is operating properly without any danger. If you visit any power stations, factories or electrical-intensive buildings, you will notice that switchgear is commonly found there.
The thing is that during any faults or short circuits, switchgear maintains everything in order. No matter what the situation is, it is extremely important to have switchgear in the system. Everything needs to be automated, and that can only be accomplished through quick interchange systems. Moreover, switchgear is advanced and saves the users from any unwanted issues from arising.
Main Functions of Switchgear
- Switchgear Protection
One of the primary functions of switchgear is protection. The moment switchgear notices an issue, such as a short circuit, an overload, or some other form of complication, it shuts off immediately. Action is taken to prevent any damage, and the overall system remains intact. It also helps prevent any potential accidents and power failures.
- Control
Switchgear allows the user to take full control of their electrical system, barring any switches that can be toggled on/off at will. Yes, the specific circuits that need to be actuated/ deactivated can be done so freely at any point in time.
- Isolation
Isolation means the cut-off and deactivation of a specific faulty part of the system from the whole system. In terms of switchgear, parts can be separated that require a repair or inspection, safely. This helps protect the workers from live wires and reduces electric shock noticeably.
- Monitoring and Measurement
Apart from the system’s fault detection, the real-time data helps improve the process of detection for other issues. So, having access to data in real-time ensures that any arising issues are identified in advance while power is managed effectively.
- Fault Clearing
Switchgear fault clearing is done by cutting off the current supply in the circuit. All this quick response makes fault repairing in a minimum time. So, it makes sure that no damage occurs and the system remains intact, stable, and safe.
2) Types and components of switchgear
Every power system employs an electrical switchgear to manage, distribute, and control power. Selecting the correct type of switchgear will allow for the safe and reliable operation of your electrical system. In this section, we will explore switchgear types, starting from their definition to their specific parts and purposes.
i) Incoming cabinet
The incoming cabinet is the part of the switchgear which brings electrical power into the system. Generally, it receives 10kV power from the external power supply network and feeds it into the 10kV bus, which is further used for distribution. This cabinet is of utmost importance in controlling, protecting and monitoring the Power supply.
Components of the Incoming Cabinet
- Vacuum Circuit Breaker: This equipment disconnects the circuit in almost instantaneous time during short circuits or overloads to save the system from damage.
- Isolating Switch: Shuts the power off safely when there is a need for maintenance or repair, for the safety of operators and equipment.
- Current Transformers: There are three sets of three coil current transformers which change the magnitude of current to a safe level for measurement and protection devices.
- Voltage Transformer: Changes high voltage into a lower controlled and standard one for special control and measuring tools.
- Lightning Arrester: Makes the system safe from dangerous voltage level increases due to lightning or electrical surges.
- Live Display: Memorises the important information concerning the electrical system and provides it to users for monitoring the power, so that they can control the flow of the power.
- Wiring and Other Components: They serve to connect all the devices in the cabinet so that the communication and tapping of power between the various components is seamless.
Functions of the Incoming Cabinet
- Power Reception and Distribution
The incoming cabinet receives power from an external source and sequentially dispatches it via the busbar to the various components of the system. This is important for the uninterrupted flow of power.
- Fault Protection
The vacuum circuit breaker is able to stop the flow of power instantaneously in the event of faults such as short circuits or overloads. This fast action protects equipment from damage and excessive financial burden.
- Maintenance Safety
The isolating switch removes power completely during maintenance. This ensures that the workers are not exposed to danger when inspecting or attempting to fix parts of the equipment.
- Accurate Measurement
Current and voltage transformers measure electrical parameters supplied, monitored, protected, and even controlled within the system.
- Surge Protection
The system is shielded against the adverse effects of lightning and other electrical activity surges by the lightning arrester.
- Real-Time Monitoring
With the aid of a live display, operators are provided with real-time updates on the system, which makes it easier to identify and correct the problems when they arise.
ii) Metering Cabinet
Another component of the switchgear system is the metering cabinet. It mainly measures the amount of electrical energy usage so that users can monitor their power consumption.
Components of the Metering Cabinet
- Current Transformer (CT): This device steps down high current to a lower, measurable value. It accurately measures the current flowing through the system.
- Fuse: This component works as a protective device. If the current exceeds a certain limit, the fuse will melt and open the circuit, which protects the equipment from sustaining damage.
- Voltage Transformer (VT) with V-V Wiring: The voltage transformer reduces the high voltage to a lower voltage that is safe for measurement. The V-V wiring method aids in effective voltage measurement with less equipment.
- Live Display: Displays parameters such as voltage and current in real time. It aids users and operators in monitoring the ease of power supply.
Functions of the Metering Cabinet
- Measure Electric Energy
The metering cabinet calculates the quantity of electric energy consumed by the system using current and voltage transformers.
- High Supply and High Metering
Deals with high amounts of voltage and current, with safety to ensure accurate energy measurement.
- Load Monitoring
Displays the real-time load power consumption to track electricity consumption.
- Energy Management
Supplies data needed for billing, fault detection, and controlling energy consumption.
- Protection Responsibility of the User
The user needs to safeguard the meter seals so that no damage or tampering can be done.
iii) PT Cabinet
The PT (Potential Transformer) cabinet may be considered a critical PT component of switchgear for measuring and controlling voltage, as it does so safely. It transforms high voltage to lower voltage within a manageable range, which, in turn, allows all meters, as well as protection devices, to function accurately.
Components of the PT Cabinet
- Voltage Transformer: Steps down the high voltage from the power system to a low voltage. This transformation enables the measurement of voltage in a safe as well as precise manner.
- Isolating Knife: A switch that safely disconnects parts of a circuit. It guarantees that no power flows during maintenance or emergencies.
- Fuse: Interrupts the circuit and ensures that the current level does not exceed the safe level. This averts damage from overload and faults.
- Lightning Arrester: Protects the system from voltage spikes which could occur through lightning bolts or other surges. This device aids in preventing faulty equipment from being damaged.
Functions of the PT Cabinet
- Voltage Measurement
Supplies a constant or close to constant voltage circuit for the meters, which takes the measurement and enables close monitoring of system voltage selection.
- Operating Power Supply
The PT cabinet supplies power to the control or operational boxes. It ensures proper operation of the switchgear equipment.
- Overvoltage Protection
The PT cabinet also places overvoltage limiters on every bus bar, enabling protection against unexpected increases in voltage, sudden rises.
- Relay Protection Support
Assists in relay actions by observing bus insulation under over-voltage and under-voltage, enabling automatic switching when faults, power back, or stand-by occur.
- Types of Wiring Schemes
The PT Cabinet employs Vv, Y, Yn, and YN wiring schemes. These wiring techniques help the transformers and units so that they can be used with high dependability.
iv) Outgoing Line Cabinet
The Outgoing Line Cabinet is an important component in the Switchgear system. It is primarily used to distribute electrical power from the primary busbar to the transformers and branch circuits. This cabinet is constructed specifically for 10kV systems, so it is the centre of medium voltage distribution.
Components of the Outgoing Line Cabinet
- 3 Sets of Three-Coil Current Transformers: These transformers ascertain the amount of current circulating in each phase of the circuit. To enable system protection by monitoring the current and providing the current reading to the protection devices.
- Isolating Switches: These devices operate to open parts of a circuit for servicing or emergencies. They make a safe break that is certainly free of current as long as the system is open.
- Circuit Breakers: They provide instantaneous interruption of power to the affected section in case of fault conditions like short circuits and overloads. Their role is to enhance the safety of equipment by disconnecting the flow of harmful currents.
- Knife Switches: These are simple manual switches which isolate or connect parts of the circuit. Their design permits easy switching of electric power on or off during operation or upkeep.
- Live Display Devices: These devices depict the status of the system in real-time.
Functions of the Outgoing Line Cabinet
- Power Distribution
The main function is to sub-distribute electric energy from the main bus bar to different branch circuits, which should receive power at appropriate levels.
- Branch Disconnection and Connection
Permits safe disconnection or connection of branch power supplies using switches and circuit breakers. Hence, control over individual circuits is achieved.
- Overcurrent Protection
The cabinet functions in conjunction with other protection devices to detect overload or fault in the shortest time possible to avoid damage.
- Monitoring
Provide circuit status updates in real time, which enables operators to monitor if the circuits are energised or isolated in a safer manner, using live display devices.
v) Contact Cabinet
Also named a busbar segmentation cabinet, the contact cabinet completes the linkage between two busbar sections. It is found in single and double busbar systems and facilitates the different desired operating modes or assists in the selective fault isolation.
Components of the Contact Cabinet
- Disconnector: This is a switch that completely opens a circuit and is used, in maintenance or during faults, to secure a circuit part.
- Breaker: A Circuit breaker automatically cuts the power to the system. This is done when faults such as short circuits or overloads occur.
- Transformer: Current transformer, as the name suggests, measures current flow for monitoring and for the purpose of protection.
- Live Display Device: Solves the problem of operators not being able to know the status of the cabinet and shows them what is going on in real time.
Functions of the Contact Cabinet
- Busbar Connection
Providing the function of bridging the gap between 2 busbar sections, it is also responsible for controlling the flow of power depending on the system’s requirements.
- Power Source Separation
If two power sources are operating at the same time, the contact cabinet will cut off the middle point in order to avoid overlap, which could lead to damaging two sections.
- Automatic Backup Supply
The cabinet will connect the busbars if the power supply is switched off or disconnected due to an accident. This maintains the continuous flow of power supply.
- Restoration to Standby
Auto disconnection of the backup supply will occur once the initial power source is restored. Disengagement of the ex-backup connections will lead the device to go into standby mode.
vi) Isolation Cabinet
An isolation cabinet is used to separate busbars at both ends, or is used to isolate receiving apparatuses from the power supply. It provides a clear endpoint that can be observed, making inspection and maintenance simpler, safer and more effective for operators.
Components of the Isolating Cabinet
- Circuit Breaker: Instantly stops power feed to a system when there’s a circuit overcurrent and short circuit fault. It can also provide control of a switch at a distance, which passes electric energy into or out of the section of the circuit.
- Fuse: Ensures peaceful operation of a circuit by removing the current path temporarily, which is melted and broken at certain limits.
- Isolating Switch: Cuts off electricity to high-voltage equipment while severing connection with live parts.
- Voltage Transformer & Current Transformer: Devices that convert high voltages to low voltage (100V) or small current (5A or 1A) streams for precise and dependable measurement.
- Lightning Arrester: Safely reduces the potential of damage to equipment derived from great energy produced by lightning or other disturbances by clipping high voltage surges.
Functions of the Isolation Cabinet
- Busbar and Equipment Isolation
The device efficiently isolates busbars or disconnects receiving equipment from the power supply. This action protects the equipment and personnel during maintenance.
- Visible Disconnection Point
The physical disconnection from the circuit allows the operator to perceive that the circuit is safely disconnected before commencing work on it.
- Fault Protection
The cabinet contains circuit breakers and fuses that very quickly interrupt the abnormal current in order to contain the fault from propagating.
- Voltage and Current Monitoring
Electrical parameters in the cabinet are measured by transformers to ensure safe and efficient operation.
- Overvoltage Protection
The lightning arrester shields the system from harmful voltage surges from external influences like a lightning strike.
3) Where to Find a Professional Switchgear Manufacturer?
If you are looking for a professional switchgear manufacturer, a good choice is Eberry Electric Co., Ltd. The company was established in 2013 and is based in Yueqing, Zhejiang, China. Eberry deals with high and low voltage components of power transmission and distribution systems. Our product range includes indoor and outdoor 10- 35kV vacuum circuit breakers, vacuum load switches, SF6 switches, gas-insulated metal-enclosed switchgear (C-GIS), and more.
Eberry’s dedication to quality is demonstrated by our certifications such as ISO 9001, ISO 5001, ISO 14001, IEC, and CE. With an in-house R&D team, we have provided tailored solutions for over 100 large-scale electrical solutions throughout the world. One more good thing is that our products are made with the utmost durability, reliability, and seamless integration.
