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Central Power Corporation (EVNCPC) announced on September 22 that Typhoon No.5 broke 304 power poles, 169 collapsed columns, and 143 tilted columns. Among 304 broken columns, there are 34 prestressed centrifugal concrete columns and 270 conventional centrifugal concrete columns. Electric poles break, fall and tilt in Quang Binh, Quang Tri, Thua Thien – Hue, Quang Nam and Da Nang provinces.
“I wonder why it is so fragile” (?!)
On the same day, the power outage caused by hundreds of broken and collapsed power poles in Thuan An City and Hue City of Thua Thien – Hue Province was basically overcome. Previously, according to the Thua Thien – Hue Electricity Company report, storm No. 5 broke out, shedding 272 medium voltage and low voltage poles.
Many people wonder why storm winds are only level 6 to level 8, shock level 9 level 11, but how can we find a power pole that is designed to withstand gusts of wind above level 12? Even Thua Thien-Hue Power Company itself admitted that “although it is a storm that is considered to be of low intensity, many power poles have been broken.”
The transformation station in Thuan An city is mounted on two traditional centrifugal concrete electric poles, but it is still broken
According to a survey by journalists on September 22, the medium voltage line combined with the low voltage line along National Highway 49A still has many leaning power poles, some of broken iron inside. Previously, the Thua Thien – Hue Electricity Company mobilized a force to clean up the transformer station on Hoang Sa Street, Thuan An City, which had broken columns and collapsed. The collapsed substation was mounted on two centrifugal concrete piers. The fracture is about 0.5 m above the ground, with a lot of 10-12 iron protruding.
Mr. Pham Thanh Lam, director of a construction company in Hue city, was surprised by the fact that the storm was not strong, but the power pole broke badly. Mr. Lam said that his unit has built many restaurants and hotels using the prestressed concrete technique. “The steel fibers are extracted small, the opening is very large. This technical solution has many advantages over the shortcoming. For the circular poles, the wind force has been greatly reduced, but somehow it is easy to break. So” – said Mr. Lam.
Break … “up to the mark”!
According to EVNCPC, by physical inspection, broken power poles are caused by trees falling within the line, causing an abnormal double impact force, which is beyond the tolerance of the structure of columns, porcelain beams, wires … The number of electric poles located outside the residential area, in the corner positions, when there are strong winds and change of wind direction, swirling and breaking the rope is also the cause of the collapse of the column.
“We have checked that all the design, construction, materials and quality of the equipment are in accordance with the regulations. The acquisition of electric poles is widely tendered in accordance with the Law. Tender By means of a review, the electric poles used in the EVNCPC network are designed and manufactured in accordance with the Vietnamese norms and standards TCVN 5847: 2016, 5847: 1994 and their quality before installation “- declared declaration.
Also stating that the power poles in Thua Thien – Hue province are up to standards, Mr. Nguyen Dai Phuc, Deputy Director of Thua Thien – Hue Electricity Company, said that the wind from storm No. 5 It was unpredictable, causing phenomena. Throwing, throwing, shaking, spinning took down a number of obstacles on the way to get around, including electric poles.
In the coming time, EVNCPC said it will strengthen the mobilization of organizations and individuals who own trees and work to comply with regulations to ensure the safety of the network corridor, especially the pruning of trees before the season. storms, minimizing damage to the network.
Pause using prestressed centrifugal concrete columns
In storm No. 12 in 2017, Khanh Hoa Electricity Joint Stock Company had around 115 transformer stations that had to be repaired or replaced; Almost 1,900 columns broke, 1,700 columns tipped. This is a very strong storm, very strong winds, swirling as the power line gets entangled with obstacles like flying iron, crushing tree … it is the cause of the broken and leaning power pole.
Speaking to the Nguoi Lao Dong newspaper reporter, the head of Khanh Hoa Electricity Joint Stock Company said that at present, the electrical industry signs contracts with concrete pillar factories with new technology, pre-tensioned centrifugation. . This technology uses imported post-tensioned steel with the advantages of saving materials and transportation. The downside is that the bending force is lower, so it often breaks horizontally. This technology allows the use of non-steel 9 in combination with high-hardness cement. Concrete calculated specifically for each component will have a quality equivalent to 20-22 non-steel compared to conventional centrifugal cylinders to ensure compliance with the prescribed TCVN. When asked about changing technology to make the poles more resistant to storms, the head of the Electricity Joint-Stock Company Khanh Hoa said there was no information.
Meanwhile, after the power poles had a massive rupture after Storm No. 5, EVN asked specialized agencies to evaluate the natural conditions of the central region, as well as the suitability of the internal centrifugal columns. specific conditions such as the evolution of the last storm. Pending the official conclusion of the authorities, the use of prestressed centrifugal concrete electric poles is suspended.
K. Nam
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