Power System Protection - CDEEP · Power System Protection S.A.Soman Department of Electrical...

Power SystemProtection

S.A.Soman

Power SystemDynamicsOverview

SystemProtectionRelaysExample System

Underfrequency andRate of Change ofFrequency Relays

Undervoltage andReverse Power Relay

LightningProtectionLightningOvervoltages

Lightning ProtectionDevices

Summary

Power System Protection

S.A.Soman

Department of Electrical EngineeringIIT Bombay

Protection Paradigms - System Protection

Power SystemProtection

S.A.Soman

Power SystemDynamicsOverview

SystemProtectionRelaysExample System

Underfrequency andRate of Change ofFrequency Relays

Undervoltage andReverse Power Relay

LightningProtectionLightningOvervoltages

Lightning ProtectionDevices

Summary

Protection Paradigms - System Protection

1 Power System DynamicsOverview

2 System Protection RelaysExample SystemUnderfrequency and Rate of Change of FrequencyRelaysUndervoltage and Reverse Power Relay

3 Lightning ProtectionLightning OvervoltagesLightning Protection Devices

4 Summary

Power SystemProtection

S.A.Soman

Power SystemDynamicsOverview

SystemProtectionRelaysExample System

Underfrequency andRate of Change ofFrequency Relays

Undervoltage andReverse Power Relay

LightningProtectionLightningOvervoltages

Lightning ProtectionDevices

Summary

Protection Paradigms - System Protection

1 Power System DynamicsOverview

2 System Protection RelaysExample SystemUnderfrequency and Rate of Change of FrequencyRelaysUndervoltage and Reverse Power Relay

3 Lightning ProtectionLightning OvervoltagesLightning Protection Devices

4 Summary

Power SystemProtection

S.A.Soman

Power SystemDynamicsOverview

SystemProtectionRelaysExample System

Underfrequency andRate of Change ofFrequency Relays

Undervoltage andReverse Power Relay

LightningProtectionLightningOvervoltages

Lightning ProtectionDevices

Summary

Protection Paradigms - System Protection

Overview of Power System DynamicsSystem protection requires study of system dynamics andcontrol. Power system dynamics

Can be described in terms of a set of differential andalgebraic equations.

Analysis is done by EMTP.

Post fault system stability is determined by transientstability studies.

Power SystemProtection

S.A.Soman

Power SystemDynamicsOverview

SystemProtectionRelaysExample System

Underfrequency andRate of Change ofFrequency Relays

Undervoltage andReverse Power Relay

LightningProtectionLightningOvervoltages

Lightning ProtectionDevices

Summary

Protection Paradigms - System Protection

Power SystemProtection

S.A.Soman

Power SystemDynamicsOverview

SystemProtectionRelaysExample System

Underfrequency andRate of Change ofFrequency Relays

Undervoltage andReverse Power Relay

LightningProtectionLightningOvervoltages

Lightning ProtectionDevices

Summary

Protection Paradigms - System Protection

System Protection RelaysFollowing relays are used to detect system disturbancesand for enhancing system stability.

Under frequency and over frequency relays.

Rate of change of frequency relays.

Under voltage relays.

Reverse power flow relays.

Vector shift relays.

For example, consider a voltage distribution system withlocal generation which is synchronized with the grid. Duringgrid disturbances, the local plant generators have to beisolated from the grid.

Power SystemProtection

S.A.Soman

Power SystemDynamicsOverview

SystemProtectionRelaysExample System

Underfrequency andRate of Change ofFrequency Relays

Undervoltage andReverse Power Relay

LightningProtectionLightningOvervoltages

Lightning ProtectionDevices

Summary

Protection Paradigms - System Protection

1 Power System DynamicsOverview

2 System Protection RelaysExample SystemUnderfrequency and Rate of Change of FrequencyRelaysUndervoltage and Reverse Power Relay

3 Lightning ProtectionLightning OvervoltagesLightning Protection Devices

4 Summary

Power SystemProtection

S.A.Soman

Power SystemDynamicsOverview

SystemProtectionRelaysExample System

Underfrequency andRate of Change ofFrequency Relays

Undervoltage andReverse Power Relay

LightningProtectionLightningOvervoltages

Lightning ProtectionDevices

Summary

Protection Paradigms - System Protection

Example System with Local Generation

Power SystemProtection

S.A.Soman

Power SystemDynamicsOverview

SystemProtectionRelaysExample System

Underfrequency andRate of Change ofFrequency Relays

Undervoltage andReverse Power Relay

LightningProtectionLightningOvervoltages

Lightning ProtectionDevices

Summary

Protection Paradigms - System Protection

Loss of Utility in the Example System

Power SystemProtection

S.A.Soman

Power SystemDynamicsOverview

SystemProtectionRelaysExample System

Underfrequency andRate of Change ofFrequency Relays

Undervoltage andReverse Power Relay

LightningProtectionLightningOvervoltages

Lightning ProtectionDevices

Summary

Protection Paradigms - System Protection

1 Power System DynamicsOverview

2 System Protection RelaysExample SystemUnderfrequency and Rate of Change of FrequencyRelaysUndervoltage and Reverse Power Relay

3 Lightning ProtectionLightning OvervoltagesLightning Protection Devices

4 Summary

Power SystemProtection

S.A.Soman

Power SystemDynamicsOverview

SystemProtectionRelaysExample System

Underfrequency andRate of Change ofFrequency Relays

Undervoltage andReverse Power Relay

LightningProtectionLightningOvervoltages

Lightning ProtectionDevices

Summary

Protection Paradigms - System Protection

Underfrequency and Rate of Change of Frequency Relays

Load-generation imbalance in a system leads to fall infrequency.

Underfrequency relay detects this drop and isolateslocal generation from the grid.

Load-generation balance has to be maintained in theislanded system.

In order to speed up the islanding decision, rate ofchange of frequency relay is used.

Power SystemProtection

S.A.Soman

Power SystemDynamicsOverview

SystemProtectionRelaysExample System

Underfrequency andRate of Change ofFrequency Relays

Undervoltage andReverse Power Relay

LightningProtectionLightningOvervoltages

Lightning ProtectionDevices

Summary

Protection Paradigms - System Protection

1 Power System DynamicsOverview

2 System Protection RelaysExample SystemUnderfrequency and Rate of Change of FrequencyRelaysUndervoltage and Reverse Power Relay

3 Lightning ProtectionLightning OvervoltagesLightning Protection Devices

4 Summary

Power SystemProtection

S.A.Soman

Power SystemDynamicsOverview

SystemProtectionRelaysExample System

Underfrequency andRate of Change ofFrequency Relays

Undervoltage andReverse Power Relay

LightningProtectionLightningOvervoltages

Lightning ProtectionDevices

Summary

Protection Paradigms - System Protection

Undervoltage Relay

If the fault on the grid is close to the plant, voltage atthe supply point of plant generator drops.

This drop in voltage is used as a signal in undervoltagerelay.

Reverse Power Relay

During prefault state, power was being fed to the plant.

During fault in the utility system, the plant will beisolated from the grid and it may be connected to thedownstream loads.

Then, power will flow in reverse direction from plantgenerator to feed the downstream loads.

This reversal of power flow can be used to island theplant generator.

Power SystemProtection

S.A.Soman

Power SystemDynamicsOverview

SystemProtectionRelaysExample System

Underfrequency andRate of Change ofFrequency Relays

Undervoltage andReverse Power Relay

LightningProtectionLightningOvervoltages

Lightning ProtectionDevices

Summary

Protection Paradigms - System Protection

Undervoltage Relay

If the fault on the grid is close to the plant, voltage atthe supply point of plant generator drops.

This drop in voltage is used as a signal in undervoltagerelay.

Reverse Power Relay

During prefault state, power was being fed to the plant.

During fault in the utility system, the plant will beisolated from the grid and it may be connected to thedownstream loads.

Then, power will flow in reverse direction from plantgenerator to feed the downstream loads.

This reversal of power flow can be used to island theplant generator.

Power SystemProtection

S.A.Soman

Power SystemDynamicsOverview

SystemProtectionRelaysExample System

Underfrequency andRate of Change ofFrequency Relays

Undervoltage andReverse Power Relay

LightningProtectionLightningOvervoltages

Lightning ProtectionDevices

Summary

Protection Paradigms - System Protection

Undervoltage Relay

If the fault on the grid is close to the plant, voltage atthe supply point of plant generator drops.

This drop in voltage is used as a signal in undervoltagerelay.

Reverse Power Relay

During prefault state, power was being fed to the plant.

During fault in the utility system, the plant will beisolated from the grid and it may be connected to thedownstream loads.

Then, power will flow in reverse direction from plantgenerator to feed the downstream loads.

This reversal of power flow can be used to island theplant generator.

Power SystemProtection

S.A.Soman

Power SystemDynamicsOverview

SystemProtectionRelaysExample System

Underfrequency andRate of Change ofFrequency Relays

Undervoltage andReverse Power Relay

LightningProtectionLightningOvervoltages

Lightning ProtectionDevices

Summary

Protection Paradigms - System Protection

Undervoltage Relay

If the fault on the grid is close to the plant, voltage atthe supply point of plant generator drops.

This drop in voltage is used as a signal in undervoltagerelay.

Reverse Power Relay

During prefault state, power was being fed to the plant.

During fault in the utility system, the plant will beisolated from the grid and it may be connected to thedownstream loads.

Then, power will flow in reverse direction from plantgenerator to feed the downstream loads.

This reversal of power flow can be used to island theplant generator.

Power SystemProtection

S.A.Soman

Power SystemDynamicsOverview

SystemProtectionRelaysExample System

Underfrequency andRate of Change ofFrequency Relays

Undervoltage andReverse Power Relay

LightningProtectionLightningOvervoltages

Lightning ProtectionDevices

Summary

Protection Paradigms - System Protection

Operation of Reverse Power Flow Pelay

Power SystemProtection

S.A.Soman

Power SystemDynamicsOverview

SystemProtectionRelaysExample System

Underfrequency andRate of Change ofFrequency Relays

Undervoltage andReverse Power Relay

LightningProtectionLightningOvervoltages

Lightning ProtectionDevices

Summary

Protection Paradigms - System Protection

Operation of Reverse Power Relay

Power SystemProtection

S.A.Soman

Power SystemDynamicsOverview

SystemProtectionRelaysExample System

Underfrequency andRate of Change ofFrequency Relays

Undervoltage andReverse Power Relay

LightningProtectionLightningOvervoltages

Lightning ProtectionDevices

Summary

Protection Paradigms - System Protection

1 Power System DynamicsOverview

2 System Protection RelaysExample SystemUnderfrequency and Rate of Change of FrequencyRelaysUndervoltage and Reverse Power Relay

3 Lightning ProtectionLightning OvervoltagesLightning Protection Devices

4 Summary

Power SystemProtection

S.A.Soman

Power SystemDynamicsOverview

SystemProtectionRelaysExample System

Underfrequency andRate of Change ofFrequency Relays

Undervoltage andReverse Power Relay

LightningProtectionLightningOvervoltages

Lightning ProtectionDevices

Summary

Protection Paradigms - System Protection

Lightning OvervoltagesLightning discharges produce overvoltage surges and theyare extremely harmful. Lightning overvoltages can beclassified as

Induced overvoltages.Overvoltages due to shielding failures.Overvoltages by back flashovers.

Power SystemProtection

S.A.Soman

Power SystemDynamicsOverview

SystemProtectionRelaysExample System

Underfrequency andRate of Change ofFrequency Relays

Undervoltage andReverse Power Relay

LightningProtectionLightningOvervoltages

Lightning ProtectionDevices

Summary

Protection Paradigms - System Protection

1 Power System DynamicsOverview

2 System Protection RelaysExample SystemUnderfrequency and Rate of Change of FrequencyRelaysUndervoltage and Reverse Power Relay

3 Lightning ProtectionLightning OvervoltagesLightning Protection Devices

4 Summary

Power SystemProtection

S.A.Soman

Power SystemDynamicsOverview

SystemProtectionRelaysExample System

Underfrequency andRate of Change ofFrequency Relays

Undervoltage andReverse Power Relay

LightningProtectionLightningOvervoltages

Lightning ProtectionDevices

Summary

Protection Paradigms - System Protection

Lightning Protection DevicesThe most commonly used devices for protection againstlightning are:

Shielding by earth wires.

Proper earthing of transmission towers.

Surge Arrestors like ZnO varistor.

Power SystemProtection

S.A.Soman

Power SystemDynamicsOverview

SystemProtectionRelaysExample System

Underfrequency andRate of Change ofFrequency Relays

Undervoltage andReverse Power Relay

LightningProtectionLightningOvervoltages

Lightning ProtectionDevices

Summary

Protection Paradigms - System Protection

Summary

Power System Dynamics.

Various System Protection Relays.

Lightning Protection.