Study Of The Rule Of Ship Cable Insulation Aging And Rapid Detection Methods

With the gradual improvement of the ship automation, as well as the emergence of electric-driven ship, marine electrical systems are increasingly complex. Cables of ship electrical system play an important role of power and signals transmission. It is well known that, the working condition of ship cables is very complex, including high temperature, humidity and mechanical vibration, which accelerate the thermal aging of ship cable. As the thermal aging of cable insulation material going on, insulation status of the cable declines. This results in ship electrical system failure, even causing fire. So, the state of cable insulation affects the ship safety and working. In addition, there are a lot of old ships are on active service. The initial ship cables (styrene-butadiene rubber is mainly used) are still used on these ships. The state of these cables insulation is unknown. To eliminate the potential safety hazard of electrical system, and to define the cable change time, it is urgent to make rapid life prediction of ship cables.Among those factors affecting insulation status of ship cables, temperature is the dominant factor. At present the ship cable life prediction is mainly based on the standards of GB/T11026and IEC60216. High-temperature accelerated aging of ship cable is conducted in laboratory firstly, and then the ship cable life in the actual use temperature can be predicted by measuring the elongation at break of the aging test specimen. But this method is destructive, sample cables should be cut from the ship electrical system; and it usually takes a long time to get the life assessment results. In addition, ship cable pass through different cabins on the ship. So, the working condition for the cables in different cabins is different. This means the sample cable can only represent a small part of the whole ship cable. So, we can not get the life assessment results of the whole ship cable.From the above, a kind of online and rapid ship cable life prediction method is needed. This is important for the ship safety and the time choice to change the cable. In this study, styrene-butadiene rubber (SBR) insulated cable which is widely used on old ship was used as the research object. A rapid detection method to evaluate the insulation thermal aging status based on hardness was developed and tested. Following work was done:Firstly, accelerated aging experiment of styrene butadiene rubber was carried out at four aging temperatures of135℃,150℃,165℃and180℃which were chosen based on relevant standards. Performance indicators of the aged samples were measured, such as hardness, elongation at break, density, and insulation resistance. The test results show that as the aging process goes on, hardness of the rubber increases, elongation at break decreases, density increases slowly and insulation resistance decreases at the end the aging process. Among them, there is a significant liner correlation between hardness and degree of aging. In order to realize the quick nondestructive testing of the life of cable insulation layer, hardness is chosen as the characteristic parameter.Secondly, the mathematical model of hardness with elongation ratio, elongation at break and crossling rate of SBR was developed. The relation of the cross linking rate of SBR cable and elongation ratio with its hardness was illuminated bassed on the model. Based on this, residue hardness retention rate (RHRR) was defined. The hardness experimental data was verified and analyzed based on the standards of GB/T11026and IEC60216. And then, a new rapid life prediction method of styrene-butadiene rubber insulated ship cable was put forward.In the end, based on the same standards of GB/T11026and IEC60216, the new rapid detectioin method was verified. There was a high consistency between the new method and the standards. The new method is accurate, rapid and simple. At the same time, the failure criteria of the new method is suggested to RHRR=45%. In addition, the test results of insulation resistance also proved the validity of the new method.In this study, the agine law of the SBR insulated ship cable was studied. Based on this, a new rapid method to predict ship cable life based on RHRR is developed. When using this method, the life prediction model (different models for different types of ship cable) based on RHRR should be developed firstly according to the process discussed in the study. The cable insulation hardness of the part which is intended to be tested should be measured. Then choose a suitable RHRR life prediction model based on the working condtion. The remaining useful life of the ship cable can be calculated then. This means the inspector can check the insulation status of any part of the ship cable at any time on board. There is no need to sample repeatedly, and the long experiment time is also eliminated.