By Amol Surendra Patharkar
Medium Voltage (MV) Switchgear and protective relays play crucial roles in an electrical system, complementing each other to ensure reliable operation. As a technical manager in the MV industry, I often address customer inquiries about the specific functions of switchgear and relays in an electrical system. Although most customers are familiar with the basic concepts, it is essential to clarify their distinct roles and importance. This article aims to explain these components in layman's terms.
A) Medium Voltage Switchgear
1. Function: Medium voltage switchgear is designed to make, carry, and break current under normal and certain abnormal conditions. It isolates healthy sections of the electrical system from faulty sections, protecting both life and property.
2. Types of Switchgear:
- Isolators
- Switch Fuse Units (SFUs)
- Circuit Breakers
These can be further classified based on:
- Installation: Indoor, Outdoor
- Mechanism: Fixed Type, Drawout Type
- Technology: Air Insulated Switchgear (AIS), Gas Insulated Switchgear (GIS)
- Application: Primary, Secondary
3. Components:
- Isolators/Switch Fuse Units/Circuit Breakers: Interrupt current flow under normal and certain abnormal conditions, either automatically (except SFUs) or manually.
- Busbars: Distribute power within the switchgear, made of copper or aluminum based on current and application.
- Instrument Transformers: Current Transformers (CTs) and Voltage (Potential) Transformers (VTs) measure current and voltage for monitoring and protection purposes. Detailed discussion on instrument transformers will be covered in a subsequent article.
4. Location: Switchgear is a part of the primary panel.
5. Role: Ensures isolation of healthy sections from faulty sections, enables maintenance, and protects personnel and equipment during abnormal conditions.
B) Protection Relay
1. Function: Protection relays monitor electrical parameters (such as current, voltage, and frequency) and initiate protective actions like tripping a circuit breaker when abnormal conditions are detected. They help prevent harm to personnel and damage to equipment, ensuring the safety of the electrical system.
2. Types of Protective Relays:
- Overcurrent Relays: Trip the circuit breaker when current exceeds a preset level.
- Voltage Relays: Respond to overvoltage or undervoltage conditions.
- Differential Relays: Compare current entering and leaving a protected zone to detect faults.
- Distance Relays: Operate based on the impedance of a line section to detect faults.
Additionally, relays can be classified as:
- Electromechanical, Numerical, Digital
- Non-communicable, Communicable
- Based on different communication protocols
Detailed discussion on relay types will be covered in a subsequent article.
3. Components: Basic components include current and voltage sensors (CTs and VTs), processing units, and communication interfaces to analyse data and send trip signals to the switchgear unit.
4. Location: Relays are placed in the Low Voltage Compartment (LVC).
5. Role: Provide intelligence and automation to detect and isolate faults quickly, minimizing damage and enhancing system reliability.
Conclusion
- Medium Voltage Switchgear: A physical assembly of components used to control and protect medium voltage electrical circuits. It includes devices like circuit breakers and switches to manage power distribution and safety.
- Protection Relay: An intelligent device that monitors electrical parameters and initiates protective actions to prevent equipment damage and maintain system integrity. It works in conjunction with switchgear to enhance system protection and automation.
In essence, switchgear serves as the hardware that controls and interrupts power flow, while protection relays provide the intelligence to detect faults and instruct the switchgear to act.
At Nuventura, we offer the SF6-free nu1 switchgear panel, utilizing dry air insulation. Our switchgear is designed with flexible configurations to meet various project and customer requirements, including circuit breaker feeder panels, disconnector panels, bus bar sectionalizer panels, bus riser panels, and bus bar earthing panels.
Our Low Voltage Compartment (LVC) comes in different heights to accommodate relays of any make and model, ensuring easy integration. Additionally, we provide a draw-out design with Harting plugs for straightforward installation and on-site LVC exchange.
For additional details regarding Dry Air (SF6 Free) GIS solutions, please contact:
Amol Surendra Patharkar
Technical Manager – Sales & Marketing
Email: amol.patharkar@nuventura.com
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