A massive lightning bolt has ignited a fireball over a city in China after it struck the city's high-voltage power lines. A footage captured by a resident shows a blaze that broke out after a very loud bang was heard in the city of Shenyang on August 3.

Terrifying blast

The residents were shaken after the blast, which happened near numerous tower blocks but no casualties were reported, according to Shenyang's state medial. The event happened during the evening rush hour in the Tiexi District of Shenyang, which is the capital of Liaoning, as reported by CCTV, the state broadcaster.

A flash of lightning hit the transmission lines near a residential compound. It sparked a fire on the grass underneath. The incident did not cause any damage to the public facility and it did not interrupt the local electrical services,.

Shenyang is a city of 8 million located in north-eastern China and it has been battered by downpours since August 3. At 11 pm local time, the meteorological bureau of the city declared a red alert for rainstorms, which is the highest level in China's four-tier color-coded weather warning system.

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The warning was immediately followed by an orange alert, the second-highest level, around 15 minutes later. Shenyang was hit by heavy rainfall of up to 70.1 millimeters per hour, between 3 pm to 8 pm on August 3, according to the local government.

The officials activated the second-highest level of alert for flood control in Shenyang as a response to the adverse weather, as reported by The DailyMail. 

What happens when lightning strikes power lines?

When lightning hits a power line, it can cause a flashover due to the surge of electricity. The appropriate corrective action all depends on how flashover happened.

A back flashover happens when a lightning stroke hits a tower structure or a shield wire. When this occurs, the current flows in both directions and down the tower into the ground, it will develop a voltage on the crossarm sufficient to flash over the insulator string. A backflash is usually caused by massive stroke currents, high tower surge impedances, and/or high footing resistance.

One cause of flashover is shielding failure. A lower current lightning stroke may cause a line to flash over if ever the stroke hits the phase wire, it could bypass the overhead shield wire.

On high-voltage transmission lines, the low-current lightning strokes cause shielding failures while the high-current strokes result in back flashovers of the tower to the phase conductors. The lower-voltage lines of this distinction are also not clear.

An induced flashover usually happens on sub-transmission and distribution lines when the impulse insulation level is below approximately 400 kV. In such cases, a lightning strike hits the ground near the line, or some other object near the right-of-way, without striking the line directly.

The electromagnetic field that results from the rapidly changing currents in the stroke can induce severe voltages that are on the phase conductors and it causes flashovers on one or even more of the insulators.

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