Protecting 33 kV Systems from Lighting Surges- Surge Arrester

The Role of Surge Arresters

Lightning surges are a major threat to electrical systems, causing damage and downtime that can result in significant costs and lost productivity. For 33 kV systems, the risk of lightning surges is particularly high, making effective surge protection crucial. In this post, we’ll explore the importance of surge arresters in protecting 33 kV systems from lightning surges.

What are Lightning Surge Arresters?

Surge arresters are devices designed to detect and divert lightning surges, preventing them from damaging electrical equipment. They work by detecting the rapid voltage increase caused by a lightning strike and providing a low-impedance path to ground, safely dissipating the surge.

Why are Surge Arresters Necessary for 33 kV Systems?

33 kV systems are particularly vulnerable to lightning surges due to their high voltage and exposure to outdoor environments. Without effective surge protection, these systems are at risk of damage and failure, resulting in costly repairs and downtime. Surge arresters provide a critical layer of protection, ensuring reliable operation and minimizing the risk of lightning-related damage.

How do Surge Arresters Protect 33 kV Systems?

Surge arresters protect 33 kV systems by:

Detecting lightning surges and providing a safe path to ground
A surge arrester detects a lightning surge and provides a safe path through the following process:

• Surge Detection
The arrester’s sensing element (usually a metal oxide varistor or silicon carbide resistor) continuously monitors the system voltage.

• Voltage Surge
When a lightning surge occurs, the voltage suddenly increases, exceeding the arrester’s threshold.

• Conduction
The sensing element rapidly switches to a low-impedance state, creating a conductive path for the surge current.

• Current Diversion
The surge current is diverted through the arrester, bypassing the protected equipment.

• Voltage Clamping
The arrester limits the voltage across the protected equipment to a safe level, preventing damage.

•  Discharge
The arrester safely dissipates the surge energy to ground, typically through a grounding system.

•  Reset
After the surge has passed, the arrester returns to its high-impedance state, ready to detect future surges.

By providing a low-impedance path for the surge current, the arrester effectively “arrests” the surge, protecting the equipment from damage.

Preventing surges from entering the system and causing damage

A surge arrester prevents surges from entering the system and causing damage in the following ways:

• Voltage Clamping
The arrester limits the voltage across the protected equipment to a safe level, preventing excessive voltage stress.

• Current Diversion
The arrester diverts the surge current away from the protected equipment, preventing it from entering the system.

• Impedance Matching
The arrester’s impedance is designed to match the surge impedance, allowing the surge energy to be effectively absorbed and dissipated.

• Fast Response Time
Surge arresters respond quickly (typically in nanoseconds) to surges, ensuring that the surge is intercepted before it can damage the equipment.

• Low Impedance Path
The arrester provides a low-impedance path for the surge current, encouraging the surge to flow through the arrester rather than the protected equipment.

• Surge Absorption
The arrester absorbs the surge energy, converting it into heat, which is then dissipated safely.
By preventing surges from entering the system, surge arresters protect equipment from damage caused by voltage spikes, current spikes, and electrical noise.
– Reducing the risk of equipment failure and downtime
A surge arrester reduces the risk of equipment failure and downtime in several ways:

• Protects against voltage spikes
Surge arresters absorb voltage spikes, preventing them from damaging equipment.

• Reduces stress on equipment
By limiting voltage surges, arresters reduce the stress on equipment, increasing its lifespan.

• Prevents overheating
Arresters dissipate surge energy, preventing overheating that can lead to equipment failure.

• Minimizes current surges
Arresters divert current surges, preventing them from flowing through equipment and causing damage.

• Reduces electrical noise
Surge arresters filter out electrical noise, preventing it from interfering with equipment operation.

• Protects against multiple surges
Arresters can withstand multiple surge events, ensuring continued protection.

• Fast response time
Arresters respond quickly to surges, reducing the exposure time of equipment to surge conditions.

• Reduces maintenance costs
By reducing equipment failure, arresters minimize maintenance costs and downtime.

By reducing the risk of equipment failure and downtime,

surge arresters help ensure reliable operation, minimize costly repairs, and maintain productivity.

– Extending the life of electrical equipment
A surge arrester helps extend the life of electrical equipment in several ways:

• Reduces voltage stress
By limiting voltage surges, arresters reduce the stress on equipment insulation and components, increasing their lifespan.

• Minimizes electrical fatigue
Repeated surges can cause electrical fatigue, leading to equipment failure. Arresters reduce the number of surges reaching the equipment, minimizing fatigue.

• Reduces component degradation
Surge arresters prevent surges from causing component degradation, extending the life of equipment components.

By reducing the stress and damage caused by surges, surge arresters help extend the life of electrical equipment, reducing the need for premature replacement and minimizing maintenance costs.

Selection and Installation Considerations:

When selecting surge arresters for 33 kV systems, consider the following factors:

– Voltage rating:
The voltage rating of a surge arrester refers to the maximum voltage that the device is designed to withstand without failing or deteriorating. It is the highest voltage that the arrester can handle without breaking down or allowing excessive current to flow.

In other words, the voltage rating represents the arrester’s ability to:

1. Withstand the normal operating voltage of the system (e.g., 33 kV)
2. Absorb surge voltages without failing (e.g., lightning strikes)
3. Prevent excessive current from flowing through the system

Read Also:   How to prevent power surge damage

Voltage ratings are typically specified as:

– Nominal voltage: The rated voltage of the system (e.g., 33 kV)
– Maximum continuous operating voltage (MCOV): The highest voltage the arrester can handle continuously
– Temporary overvoltage (TOV) rating: The highest voltage the arrester can withstand for a short period (e.g., during a surge event)
Ensure the arrester is rated for 33 kV systems
– Discharge capacity: Choose an arrester with sufficient discharge capacity to handle potential surges
– Installation: Follow proper installation practices to ensure effective protection


Surge arresters play a critical role in protecting 33 kV systems from lightning surges. By understanding the importance of surge protection and selecting the right arresters for your system, you can minimize the risk of damage and downtime, ensuring reliable operation and extending the life of your electrical equipments.

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