Overvoltage Protection in
Transmission Systems
• Surge Arresters and Protection of Transmission
Lines
• [Your Name] - [Date]
Introduction to Overvoltage
• Overvoltage: Voltage higher than the rated
system voltage
• Causes: Lightning, Switching Surges, Faults
• Importance: Prevents damage to power
system equipment
Causes of Overvoltage
• Natural Causes: Lightning, Electrostatic
Induction
• Operational Causes: Switching surges, Load
rejection, Fault initiation/clearing
Temporary Overvoltage (TOV)
• Lasts for a few cycles
• Causes: Faults, Load rejection, Resonance
• Effects: Stress on insulation
Switching Overvoltage
• Caused by breaker operations
• High transient voltages
• Impacts on transmission equipment
Lightning Overvoltage
• Direct strikes: Severe damage
• Indirect strikes: Induced voltage surges
• Requires protection measures
Introduction to Surge Arresters
• Purpose: Protects equipment from transient
overvoltages
• Diverts excess voltage safely to ground
Types of Surge Arresters
• Expulsion-type Arresters
• Valve-type Arresters
• Metal-Oxide Surge Arresters (MOSA)
Metal-Oxide Surge Arresters
(MOSA)
• Structure: Zinc Oxide Discs, Housing
• Fast response, High energy absorption
Placement and Installation of Surge
Arresters
• Installed near transformers, breakers, cable
terminations
• Proper grounding essential
• Follow IEEE/IEC standards
Shielding with Ground Wires
• Overhead Ground Wires (OHGW) reduce
lightning impact
• Shielding Angle determines protection
effectiveness
Grounding of Transmission Lines
• Proper grounding methods: Counterpoise,
Ground rods
• Reduces overvoltage risks
Insulation Coordination
• Ensures insulation withstands voltage surges
• Coordinates line insulation, arresters, and
grounding
Use of Line Arresters
• Placed in high-risk areas
• Improves system reliability
• Example: Polymer-housed arresters for HV
lines
Surge Arrester Ratings
• Continuous Operating Voltage (Uc)
• Maximum Discharge Voltage
• Energy Absorption Capability
Coordination with Other Protective
Devices
• Integration with circuit breakers and relays
• Ensures effective system protection
Case Study 1: Lightning Protection
in 400kV Line
• Use of shield wires and surge arresters
• Results: Improved reliability, fewer outages
Case Study 2: Switching Surge
Protection in Substations
• Application in GIS substations
• Reduction of transient overvoltages
Summary of Overvoltage
Protection Strategies
• Surge Arresters and Shielding techniques are
critical
• Best practices for effective protection
Future Trends in Overvoltage
Protection
• Smart surge arresters with IoT monitoring
• Advanced materials for better performance
References & Q&A
• List of IEEE/IEC standards
• Research papers and technical resources