Causes and Countermeasures of lightning damage to

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Causes and Countermeasures of lightning damage to rural distribution transformer

summer is the season of frequent thunderstorms, and it is also the peak period of rural distribution transformer damage. What is the cause of lightning stroke accident of distribution transformer? How to effectively prevent the lightning accident of distribution transformer is discussed in combination with the actual situation of Linqu County power supply company

1 cause of lightning damage of distribution transformer

lightning arrester is not perfect. The low-voltage lightning arrester is not installed at the low-voltage side of the rural distribution transformer, because the rural low-voltage lines are distributed in fields and mountains, without any protection, and are prone to lightning strikes

the use and management of lightning arresters are not standardized. Some users should test the arrester before using the obsolete products. In the process of use, some users test irregularly or install for a long time in order to save the test fee. In addition, in order to save money, they privately bought unqualified lightning arresters and installed low-quality products

the grounding resistance value is too large, and the reason for the large grounding resistance:

the grounding resistance test is not carried out, or the measurement is careless, and it is considered that as long as there is a grounding point

the grounding resistance exceeds the specified value due to corrosion and other reasons

the connection point is not firmly connected, such as the downlead is not firmly connected, the lightning arrester is not firmly connected, and the transformer shell is not firmly connected

the vicious cycle of repetition has caused users to distrust domestic brands

the cross section of the grounding downlead is too small

the steel specification of the grounding body does not meet the requirements

the grounding body is not buried deep enough

the soil resistivity is too large and has not been treated, which cannot meet the requirements

2 measures to prevent the distribution transformer from being struck by lightning

hy1.5w-0.28 low voltage metal oxide lightning arrester is installed in the distribution cabinet (box) at the low voltage side of the distribution transformer, which can effectively prevent the damage to the distribution transformer caused by the positive transformation wave when the line at the low voltage side falls into lightning, so as to protect the distribution transformer and its total metering device

if possible, the insulator iron pins on the first, second and third base poles of the incoming line at the high voltage side and outgoing line at the low voltage side of the distribution transformer shall be grounded. When lightning strikes on the line, the lightning intrusion wave will be introduced to the earth through these insulator weak points, which greatly reduces the overvoltage amplitude and steepness entering the distribution transformer winding, and plays the role of wave clipping and pressure reduction to protect the distribution transformer

do a good job in the quality management of concealed works. The horizontal grounding body is buried 0.6 ~ 0.8m deep in the soil, while the vertical grounding body is driven into the ground on the basis of the horizontal grounding body. The horizontal grounding body generally adopts 40mm 4mm Flat Steel focusing on the industrialization development of new materials and new technologies and the market, the vertical grounding body adopts 50mm 50mm 5mm angle steel, and the grounding lead wire adopts 10mm Round steel or 40mm 4mm Flat steel. The construction process is strictly supervised to ensure the project quality and the use of qualified materials. For the convenience of detection and the safety of electricity use, for the transformer installed on the pole, the connection point of the lead wire should be set at the channel steel position under the transformer, welded with galvanized iron sheet, and then connected with the parallel hook clamp

the grounding down lead of the lightning arrester should be Trinity, that is, the grounding down lead of the lightning arrester, the metal shell of the distribution transformer and the neutral point at the low voltage side should be connected together first, forming a glass protective layer on the material surface, and then connected with the grounding wire. The grounding resistance shall comply with the regulations: the grounding resistance below 100kVA shall not be greater than 10100kva, and the grounding resistance above 100kVA shall not be greater than 4

qualified products from regular manufacturers should be used. Before installing high and low voltage side arresters, inspections and tests should be carried out to eliminate the use of inferior arresters. The lightning arrester shall be installed vertically without inclination, and the lead connection shall be firm

the lightning arrester at the high voltage side should be installed at the lower side of the drop protector, more than 0.5m away from the end cover of the transformer, so that it can be close to the transformer and reduce the influence of the down lead inductance on the distribution transformer during lightning stroke; It can also avoid the power failure of the whole line during the maintenance of lightning arrester; It can also prevent the lightning arrester from exploding and damaging the porcelain bushing of the transformer

to strengthen management, first, we should implement the project acceptance and handover system and the operation management assessment system; Second, it is necessary to regularly reduce the weight of components, patrol and inspect the lightning arrester, the connection point of grounding lead and test the grounding resistance value, and timely deal with the problems found during the inspection to ensure that the lightning arrester plays its due role

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