Blackout | Engineers point to 2 potential reasons for high electricity consumption or cable fire during the "Summer Solstice"

The CLP Cable Bridge in Yuen Long caught fire last night (21st), causing major power outages in Tin Shui Wai and Yuen Long.

The representative of the Electrical Division of the Hong Kong Institution of Engineers, Law Wai-chou, said on the radio program this morning that the investigation is still ongoing, so it is difficult to know exactly the cause of the fire. It may be due to overload, overvoltage, and impedance that is too high or too low.

Although power has been restored so far, there are still power outages for some users. He pointed out that when designing the power network, most of the transmission capacity will be backed up, but even if there is a back-up, it cannot completely replace the original power supply on both sides. Some, but some may have to wait a while.”

▼Fire scene situation▼

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At the moment of the accident, the peak electric current in the evening was too large or overloaded

Asked about the possible cause of the cable bridge fire, Lao Weichao said that overload may be involved, that is, excessive current.

He explained that the weather has been hot recently, and yesterday was the summer solstice. The incident happened in the evening. In the past, 6 to 7 p.m. was the peak time for electricity consumption in Hong Kong. off, so the power consumption will generally be higher.

If the cable current is too large and goes unnoticed, there is a chance of overheating and fire.

Another reason or network overvoltage causes the cable to flash over

Lao Weichao also said that another reason may also be related to voltage, that is, there is a chance that there will be overvoltage in the network, resulting in a flashover in the cable. The reasons may include being struck by lightning.

He pointed out that although there may be no thunder and lightning yesterday, there are other reasons for overvoltage in certain parts of the cable.

Deterioration of the connection point or the entry of rainwater can also cause the resistance to be too low

As for the last possible cause, it involves too high or too low impedance.

He explained that too low means that the insulation resistance is too low, for example, due to insulation aging, fire nearby, etc. In addition, if the connection position is aging, rainwater enters, etc., it may also cause the resistance to be too high.

▼On the evening of June 21, there will be a power outage in Yuen Long and Tin Shui Wai▼

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Lau continued to point out that the above situation was anticipated when the power system was originally designed, so there is a system to monitor.

However, if there is a problem with the monitoring system, such as a broken monitor or an error in the transmission system, there is a chance that the problem will be discovered late or even not discovered.

However, Law said that overvoltage is generally more difficult to monitor, because when a problem is found, the insulation has been damaged. He cited lightning as an example, "When it flashes, as soon as you know the overvoltage ... there has been a flashover."

The backup plan cannot completely replace the normal power supply Lao Weicho: some places may have to wait for the power to be restored

Lao Weichao also said that three cables were affected this time, and the related voltage was very high, that is, the original transportation current was very large, so the scope of influence was very wide.

Regarding the fact that although the power has been restored so far, there are still some users without power. He pointed out that when designing the power network, most of the transmission capacity will be backed up.

However, he said the grid is mostly a ring circuit, with at least two sides supplying power.

Therefore, even if there is a backup, it cannot completely replace the original two-sided power supply, "so most of them can be restored, but some may have to wait for a while."

When asked if the power supply is expected to remain unstable in the short term, he said that this time it was not affected by bad weather, but a fire, so it is not expected.

Attached list｜There are still power outages in some areas of Tin Shui Wai, 11 schools are suspended today, and there is a major power outage｜Residents have a home and can’t be shocked to hear that it will take 2 days to repair it exclaimed: What a big dose!

Power outage｜Cable bridge in Yuen Long was destroyed by fire, firefighters believe there is no suspicious cause of fire urgent bulk