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Power Equipment in a Substation and Their Functions

Time:2024-06-03   Author:As Beam   Browse:

1. Main Power Equipment in a Substation

Substations are critical components in power systems, used for transforming, distributing, and controlling electrical energy. They comprise various typical power equipment, including:


Transformers: Used to convert electrical energy between different voltage levels, including stepping up or stepping down voltage.

Circuit Breakers: Employed to disconnect or connect circuits under normal or short-circuit conditions for maintenance, fault handling, and safe operation.

Disconnect Switches: Used to isolate electrical equipment, ensuring the safety of maintenance personnel and equipment.

Voltage Transformers (VTs) and Current Transformers (CTs): Used to measure voltage and current, providing feedback signals for control systems.

Reactive Power Compensation Devices (Capacitors and Reactors): Used for power compensation and improving power factor.

Surge Arresters: Protect equipment from overvoltage damage by diverting excess voltage to the ground.

Control Systems and Protective Devices: Monitor, control, and protect the normal operation of power equipment.

Transmission Lines and Cables: Transmit electrical energy from power plants to substations and from substations to consumers.

Battery Banks and Backup Power Supplies: Provide emergency power supply to ensure the operation of control and protection systems.

These devices work collaboratively to ensure the stable supply, distribution, and control of electrical energy, thereby guaranteeing the normal operation of the power system.


2. Power Transformers in Substation

Power transformers play a crucial role in substations by converting electrical energy between different voltage levels for efficient transmission and utilization.


Typical structure of a power transformer includes:

Main Magnetic Circuit (Core): Made of high magnetic permeability iron core to guide and concentrate the magnetic field, enabling efficient energy transfer.

High Voltage (HV) and Low Voltage (LV) Windings: Coils wound around the core, with the HV winding typically connected to the transmission line and the LV winding connected to the distribution system or users. The turns ratio determines the transformer's voltage ratio.

Insulation Materials: Insulate between windings and between windings and the core, ensuring electrical isolation and safe operation.

Oil Tank and Cooling System: Transformers are usually filled with insulating oil. The oil tank holds the oil, and the cooling system (typically radiators) dissipates heat to maintain normal operating temperature.

Connectors and Bushings: Connect HV and LV windings to external circuits, usually located on the transformer sides.

Protection and Monitoring Devices: Monitor the transformer's condition, temperature, oil level, and trigger protective actions to prevent overloads or short circuits.

Oil Thermometer and Temperature Controller: Monitor the temperature of the insulating oil and activate the cooling system as needed.

Discharge Devices and Surge Arresters: Discharge overvoltages and protect the transformer from damage.

These components work together to enable power transformers to convert electrical energy, meeting different voltage level requirements and ensuring the stable supply of the power system.

Power Transformers in Substation.jpg


3. Circuit Breakers in Substation

High-voltage circuit breakers in substations are crucial for connecting or disconnecting circuits, with primary functions including:


Circuit Interruption and Connection: Quickly and reliably disconnect circuits for maintenance, inspection, or fault handling and reconnect circuits to restore power supply.

Overload and Short Circuit Protection: Detect overcurrent or short circuit conditions and automatically disconnect circuits to prevent equipment damage or fire.

Electrical Isolation: Isolate electrical equipment from the power supply for safety during maintenance or emergencies.

Control and Protection: Typically connected to protection and control systems for automated operation, remote control, and monitoring.

Typical structure of high-voltage circuit breakers includes:


Body: Usually a metal enclosure supporting and protecting internal components.

Breaker Mechanism: Controls the opening and closing of the breaker, can be manual or motor-operated.

Contacts: Connect circuits in the closed state and disconnect in the open state, usually made of conductive materials.

Spring Mechanism: Provides sufficient force to ensure quick and reliable disconnection.

Protection Devices: Detect parameters like current, voltage, and temperature to trigger disconnection in case of faults or anomalies.

Actuator: Provides the force for controlling the breaker mechanism, especially in motor-operated breakers.

Control Circuit: Receives external control signals and triggers the breaker operation as needed.

The design and structure of high-voltage circuit breakers vary according to voltage levels, current capacities, and application requirements, playing a critical role in ensuring the safe operation of power equipment and the stability of the power system.

Circuit Breakers in Substation.jpg


4. Disconnecting and Grounding Switches in Substation

High-voltage disconnecting and grounding switches in substations are critical for isolating high-voltage electrical equipment from the ground and ensuring safe operation. Their primary function is to disconnect electrical equipment from the power supply during maintenance, inspection, or emergencies, allowing personnel to safely approach and work on the equipment. They can also isolate faulty equipment to prevent fault propagation.


Typical components of high-voltage disconnecting and grounding switches include:


Body: Usually made of insulating materials to support the switch components and isolate electrical connections.

Operating Mechanism: Mechanical device for opening or closing the switch, typically manual or motor-operated.

Contacts: Electrical connection parts that connect or disconnect electrical equipment from the power supply.

Insulating Supports: Support the contacts in the closed state and ensure electrical isolation.

Grounding Blades: Ensure safe grounding of equipment, preventing residual charges.

High-voltage disconnecting and grounding switches are typically used only for disconnecting electrical connections, not for load switching or breaking circuits, and require specific operating procedures and safety guidelines to ensure personnel and system reliability.

Disconnecting and Grounding Switches in Substation.jpg


5. Instrument Transformers

Instrument transformers (Current Transformers and Voltage Transformers) in substations are essential for measuring current and voltage, performing the following functions:


Current Measurement: Current transformers convert high current to low current for measurement and monitoring, connecting to ammeters, protection devices, etc., to monitor current changes and protect the system.

Voltage Measurement: Voltage transformers convert high voltage to low voltage for measurement and monitoring, connecting to voltmeters, protection devices, etc., to monitor voltage changes and control the system.

Protection and Control: Instrument transformers play a crucial role in protection devices, monitoring current and voltage anomalies, triggering circuit breakers during faults to prevent system failures.

Typical structure of instrument transformers includes:

Windings: Wrapped with insulating materials to convert high current or voltage to suitable levels for measurement or protection devices.

Magnetic Core: Concentrates the magnetic field for current or voltage conversion, typically made of high permeability iron core.

Housing: Encases the transformer to ensure safe operation and protect internal components from external environments.

Insulation Materials: Ensure electrical isolation between windings and other components, preventing electrical leakage.

Terminals and Connectors: Connect instrument transformers to measuring devices, protection devices, or control systems.

Discharge Devices and Surge Arresters: Discharge overvoltages to protect transformers from damage.

Instrument transformers are designed considering accuracy, insulation performance, and thermal endurance to provide accurate and reliable current and voltage measurements for power system protection and control.

 Instrument Transformers.jpg

6. Reactive Power Compensation Devices

Reactive power compensation devices in substations adjust reactive power to improve system power factor and stability. Their main functions include:


Power Factor Improvement: Adjust the phase difference between current and voltage to improve system power factor, reducing reactive power flow and enhancing energy transmission efficiency.

Voltage Stability: Adjust grid voltage to maintain it within a reasonable range, enhancing grid stability and preventing equipment damage from low or high voltage.

Energy Loss Reduction: Reduce reactive power flow, lowering energy losses in transmission and distribution, and improving energy utilization.

Grid Capacity Enhancement: Free up transmission lines and transformer capacity to carry more active loads.

Typical structure of reactive power compensation devices includes:

Capacitors and Reactors: Capacitors provide reactive power, and reactors absorb reactive power, forming reactive compensation units.

Controllers: Monitor grid parameters like power factor and voltage, automatically adjusting the connection and disconnection of capacitors and reactors for desired compensation.

Contactors and Switching Devices: Control the connection and disconnection of capacitors and reactors based on controller instructions.

Protection Devices: Monitor the status of devices like overcurrent and overvoltage, triggering disconnection to protect the device and grid.

Reactive power compensation devices are designed and configured based on specific power system needs and load conditions, playing a crucial role in maintaining power system stability, improving efficiency, and optimizing energy utilization.

 Reactive Power Compensation Devices.jpg

7. Surge Arresters in Substation

Surge arresters in substations protect electrical equipment from overvoltage damage by diverting excess voltage to the ground.


Main functions of surge arresters include:

Overvoltage Protection: Divert overvoltage caused by lightning, switching operations, or other reasons to the ground, protecting equipment from damage.

Insulation Protection: Reduce the risk of insulation breakdown caused by overvoltage, protecting equipment insulation.

Equipment Reliability Maintenance: Enhance equipment reliability and lifespan by protecting against overvoltage damage.

Typical structure of surge arresters includes:

Zinc Oxide Varistors: Main component that conducts overvoltage, typically made of zinc oxide for high conductivity.

Insulating Housing: Encloses the internal electrodes to ensure insulation performance.

Base and Terminal Connectors: Connect the surge arrester to the power system, ensuring electrical connection and mechanical support.

Sealing Device: Prevents moisture or other contaminants from entering the arrester, maintaining performance.

Surge arresters are designed for high reliability and endurance, protecting the power system from overvoltage damage and ensuring stable operation.

 Surge Arresters in Substation.jpg

8. Transmission Lines and Cables

Transmission lines and cables in substations transmit electrical energy from power plants to substations and from substations to consumers.


Main functions include:

Electrical Energy Transmission: Carry electrical energy between power plants, substations, and consumers, enabling energy distribution.

Voltage Regulation: Maintain voltage levels within specified ranges to ensure power quality and system stability.

Fault Detection and Protection: Monitor current and voltage parameters for detecting and protecting against faults, ensuring safe operation.

Typical structure of transmission lines and cables includes:

Conductor: Transmits electrical energy, typically made of aluminum or copper.

Insulation Layer: Surrounds the conductor to prevent electrical leakage, typically made of high-strength insulating materials.

Shielding Layer: Protects against electromagnetic interference and ensures transmission quality.

Mechanical Protection Layer: Ensures mechanical strength and durability, typically made of steel wire or armor.

Outer Jacket: Protects internal components from environmental damage, ensuring cable performance.

Transmission lines and cables are designed for reliable, efficient, and safe electrical energy transmission, playing a crucial role in maintaining the stability and reliability of the power system.


9. Battery Banks and Backup Power Supplies

Battery banks and backup power supplies in substations provide emergency power to ensure the operation of control and protection systems during power outages.


Main functions include:

Emergency Power Supply: Provide power to control and protection systems during power outages, ensuring continuous operation and avoiding system failures.

Stabilizing Voltage and Current: Stabilize voltage and current to maintain normal operation of control and protection devices, enhancing system stability.

Improving Reliability: Enhance system reliability by providing redundant power sources and ensuring normal operation during emergencies.

Typical structure of battery banks and backup power supplies includes:

Battery Cells: Store electrical energy and provide emergency power, typically made of lead-acid or lithium-ion.

Charging System: Charges the batteries during normal operation, ensuring sufficient energy storage for emergencies.

Inverters and Converters: Convert DC power from batteries to AC power for control and protection systems, ensuring compatibility.

Monitoring and Protection Devices: Monitor battery status, voltage, and current, protecting against overcharge, overdischarge, and other faults.

Battery banks and backup power supplies are critical for ensuring the reliability and stability of the power system, providing emergency power during outages, and enhancing system resilience.

 Battery Banks and Backup Power Supplies.jpg

10. Control Systems and Protective Devices

Control systems and protective devices in substations monitor, control, and protect power equipment, ensuring the stable operation of the power system.


Main functions include:

Monitoring and Control: Monitor power system parameters like voltage, current, and frequency, controlling the operation of power equipment to ensure normal operation.

Fault Detection and Protection: Detect faults like overcurrent, overvoltage, and short circuits, triggering protective actions to prevent equipment damage and system failures.

Automation and Remote Control: Enable automated operation and remote control, enhancing system efficiency and reliability.

Typical structure of control systems and protective devices includes:

Control Units: Central processing units that monitor and control the operation of power equipment, executing control commands and processing feedback signals.

Sensors and Transducers: Measure power system parameters and convert them to signals for the control units, ensuring accurate monitoring.

Communication Systems: Transmit control commands and feedback signals between control units and power equipment, enabling remote control and monitoring.

Protection Relays: Detect faults and trigger protective actions, ensuring equipment safety and system stability.

Human-Machine Interface (HMI): Provide user interfaces for operators to monitor and control the power system, enhancing usability and efficiency.

Control systems and protective devices are designed for high reliability and precision, ensuring the stable operation of power equipment and the overall power system.

New industry Technology regarding to Bussmann fuse, ABB breakers, Amphenol connectors, HPS transformers, etc. 

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