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Lightning Phenomenon in High Voltage Engineering

Lightning is one of the most beautiful and powerful natural phenomena in high-voltage engineering. Lightning strikes, with their awe-inspiring displays of electrical energy, have intrigued and fascinated humans for centuries. Beyond their visual spectacle, lightning poses significant challenges and considerations in various areas, including power transmission, surge protection, and infrastructure resilience. The discharge of the charged cloud to the ground is called the lightning phenomenon.

Analyzing Lightning Discharges: Voltage, Current & Power

Lightning is a powerful natural phenomenon that manifests as a sudden and intense discharge of electrical energy in the atmosphere. It is accompanied by a bright flash of light and a characteristic rumbling sound known as thunder. Understanding lightning discharges’ voltage, current, and power characteristics in high-voltage engineering is crucial for assessing their potential impact and designing effective protection systems.

It is a peak discharge in which charge accumulated in the clouds discharges into a neighboring cloud or to the ground.

The large spark accompanied by the light produced by an abrupt, discontinuous discharge of electricity through the air from the clouds, generally under turbulent conditions, is called lightning.

Representative values of a lightning stroke are as below:

Voltage : 2 x 108 volts; 200 MV (peak)

Current :  4 x 44 amperes

Duration:  l0-5 Second

KW      : 8 x 109

KWH: 22

Lightning Phenomenon In High Voltage Engineering

Voltage

Lightning discharges involve extremely high voltages. The voltage levels associated with lightning strikes can reach great values, often exceeding 100 million volts (100 MV). These peak voltages result from the immense charge buildup within thunderstorms, eventually discharged as lightning.

Voltage

Current

The current associated with lightning discharges can be equally remarkable. It typically ranges from tens of thousands to hundreds of thousands of amperes. On average, a typical lightning stroke can have a current magnitude of around 30,000 amperes, although it can vary significantly from one discharge to another.

Power

Analyzing the power associated with lightning discharges provides insights into their potential destructive capabilities. Capacity is calculated by multiplying the voltage and current values. Lightning strokes can generate staggering amounts of power, often reaching billions of watts (gigawatts). The power levels of a lightning discharge can exceed 10^9 watts (1 GW), making it an immensely energetic event.

Duration

Lightning discharges occur rapidly, typically lasting for a fraction of a second. The duration of a lightning stroke is relatively short, typically around 0.1 microseconds (10^-7 seconds). However, multiple strokes can occur within the same lightning event, contributing to the overall duration of the discharge.

Causes and Effects of Over Voltages

The influencing factors for the formation or accumulation of charge in the clouds are many, and they are uncertain. However, during thunderstorm conditions, positive and negative heads in the shadows get separated by heavy air currents, with ice crystals in the upper part and rain in the lower parts of the cloud.

The distance of separation between clouds to the ground is very large, maybe even 10000 m, but it depends on the height of the shadows. The maximum voltage gradient reached at the ground level due to a cloud could be as high as 300 V per cm.

A probable charge distribution model, as shown in the fig. below with the corresponding field gradient near the ground:

Lightning Phenomenon In High Voltage Engineering

A theory by Simpson explains that there are three essential regions in the cloud for charge formation. Below part A (shown in Fig), air currents travel above 800 cm/s, and no raindrops fall through. In region A, air velocity is high enough to break the falling raindrops causing a positive charge spray in the cloud and a negative charge in the air. The fountain is blown upwards, but as the air velocity decreases, the positively charged water drops combine with the larger bubbles and fall again. Thus region A eventually becomes predominantly positively charged, while region B above it becomes negatively charged by air currents. In the upper regions of the cloud, the temperature is as low as the freezing point, and only ice crystals exist. The impact of air on these crystals makes them negatively charged. Thus, the charge distribution within the cloud becomes, as shown at the top of.

Effects on High Voltage Systems

Lightning strikes can cause various adverse effects on high-voltage engineering systems:

Equipment Damage

Sensitive electrical equipment like transformers, circuit breakers, and power electronics can suffer irreversible damage due to the high energy content of lightning strikes.

Transmission Line Outages

Direct or nearby lightning strikes can induce voltage surges that disrupt power transmission, leading to service interruptions.

Insulation Failure

The high electric fields associated with lightning can cause insulation breakdown and flashovers, compromising the reliability of power systems.

Grounding Issues

Inadequate grounding of high-voltage equipment can result in increased vulnerability to lightning-induced transients.
Lightning Protection and Mitigation: To minimize the impact of lightning on high-voltage engineering, several protective measures are employed:

  • Lightning Rods: Installing lightning rods on tall structures can provide a preferred pathway for lightning strikes, safely guiding the electrical discharge to the ground
  •  Surge Arresters: Surge arresters protect equipment from transient overvoltages from lightning strikes or switching operations.
  • Grounding Systems: Proper grounding of electrical systems helps dissipate the energy from lightning strikes safely into the ground.
  • Shielding and Insulation: Shielding high-voltage equipment and improving insulation can reduce the likelihood of lightning-induced damage.

Conclusion

Understanding lightning discharges’ characteristics and effects is crucial in high-voltage engineering. Implementing appropriate lightning protection measures can enhance the reliability and safety of electrical systems, reducing downtime and preventing extensive damage caused by this powerful natural phenomenon.

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