The short-circuit strength of a bus duct reflects its ability to withstand short-term short-circuit currents(rated short-time withstand current and rated peak withstand current).Short circuit currents generate thermal and electrical stresses,and the bus duct should not deform excessively after being impacted by short-circuit currents.If the electrical clearance and creepage distance of the bus duct still meet the requirements after being impacted by short-circuit currents,it will not hinder the normal connection of the tap changer unit.When there is no sign of damage to the insulation of the bus duct and the insulation support parts of the components,slight deformation of the bus duct is allowed;The detection device has no fault current indication;The parts used for connecting the busbar should not be loose or detached.

　　The function of the protective grounding device should not be weakened;Not damaging the protection level;It can withstand withstand voltage tests without maintenance.The national standard does not specify the short-circuit strength of bus ducts,but requires the value of short-time withstand current to be specified in the product standard.The short-circuit strength of bus ducts varies in different places in engineering.At the near power end,the required short-circuit strength is higher,and the farther away from the power end,the lower the required short-circuit strength.The short-circuit strength of the bus duct is related to the distance between the busbars,and the larger the phase to phase distance,the greater the short-circuit strength that the bus duct can withstand.Bus ducts require almost no maintenance,and daily maintenance usually involves measuring the temperature rise of the casing and core bolts,as well as the temperature rise of the joints in the incoming box.If the core bolts are of grade 4.8,they need to be tightened regularly.

　　If the bus duct uses 8.8 grade high-strength bolts,it does not need to be reinforced regularly,while cables are limited by factors such as easy wear and tear,aging,and short service life,and require regular inspection,maintenance,and even replacement.The busbar duct utilizes air conduction for heat dissipation and dissipates heat through a tightly contacting steel casing,thus its heat dissipation performance is comparable to that of cables,and the cable heat dissipation performance is evident.The busbar trunking has good heat dissipation performance.The insulation material of the cable(core wire insulation and outer insulation)is both insulation material and thermal insulation material.Therefore,when laying power cables in the cable tray,it is allowed to lay 2 layers,because heat dissipation is considered.

　　The bus duct adopts a non-magnetic material aluminum alloy shell with good conductivity as the protective ground wire,which is surrounded by the conductive busbar.Due to its proximity to the three-phase busbar as much as possible,it can achieve low reactance,and the distance between the protective ground wire and the three-phase busbar is equal,with the same reactance.In this way,whether it is a short-term or continuous relative ground short circuit fault,this grounding method is better than setting up a separate PE row.Due to the fact that the fault current induced by electromagnetic induction on the protective ground wire is 50%higher than calculated by actual measurement,and the distance between the three-phase conductive rows and PE is uneven,the inductance is also uneven.When the line is long,the three-phase is severely unbalanced under fault current.