​​I. Why Medium Voltage Protection Matters​​

• ​​Short Circuits​​ (phase-to-phase or phase-to-ground)
• ​​Overcurrents​​ (due to overload or equipment failure)
• ​​Ground Faults​​ (current leaking to earth)
• ​​Arc Flashes​​ (dangerous electrical explosions)

​​II. Key Components of Medium Voltage Protection​​

​​1. Protective Relays​​

• ​​Overcurrent Relays​​ – Detect excessive current flow.
• ​​Differential Relays​​ – Compare currents at both ends of a line to detect internal faults.
• ​​Distance Relays​​ – Identify faults based on impedance measurements.
• ​​Earth Fault Relays​​ – Protect against ground faults.

​​2. Circuit Breakers (MV Range)​​

• ​​Vacuum Circuit Breakers (VCBs)​​ – Most common for MV (up to 36 kV).
• ​​SF₆ Circuit Breakers​​ – Used in high-voltage applications (though being phased out).
• ​​Air & Gas-Insulated Breakers​​ – Alternative for specific environments.

​​3. Switchgear & Protection Panels​​

• ​​Metal-Clad Switchgear​​ – Enclosed, modular design for safety.
• ​​Ring Main Units (RMUs)​​ – Compact protection for distribution networks.
• ​​Protection Control Panels​​ – House relays, meters, and control devices.

​​4. Current & Voltage Transformers (CTs & VTs)​​

• ​​Step down high MV signals​​ to measurable levels for relays.

​​III. Types of Medium Voltage Protection Schemes​​

​​1. Feeder Protection​​

• Protects power lines feeding loads (motors, transformers).
• Uses ​​overcurrent, distance, and differential relays​​.

​​2. Transformer Protection​​

• ​​Differential Relays​​ (detect internal faults).
• ​​Buchholz Relays​​ (for transformer internal faults like gas buildup).
• ​​Overload & Temperature Protection​​.

​​3. Motor Protection​​

• ​​Overcurrent & Thermal Protection​​ (prevent motor burnout).
• ​​Earth Fault & Stalling Protection​​.

​​4. Busbar Protection​​

• ​​Differential Relays​​ (detect faults in main busbars).
• ​​Fast isolation to prevent system-wide outages​​.

​​IV. Advanced MV Protection Technologies​​

​​V. Best Practices for MV Protection​​

1. ​​Proper Relay Coordination​​ – Ensure ​​selective tripping​​ (only faulty section isolates).
2. ​​Regular Testing & Maintenance​​ – ​​Relay calibration, breaker testing, CT/VT checks​​.
3. ​​Arc Flash Risk Assessment​​ – ​​Proper PPE & fast protection schemes​​.
4. ​​Redundancy & Fail-Safes​​ – ​​Backup protection for critical systems​​.
5. ​​Compliance with Standards​​ – ​​IEC, IEEE, ANSI, and local regulations​​.

​​VI. The Role of Degatech Electric in MV Protection​​