Method and device for on-line monitoring power cable metal sheath layer insulating state

Abstract

The invention discloses a method to on-line monitor the insulated state of power cable metal shield shelves and its equipment, based on the single conductor cable metal circulation model, the method compute relation formula is as follows: Sensors will be packaged on the power cable metal shield shelves and collect circulation significant change signal, the signals are processed by the signal conditioning which is composes of sampling resistor, circuit protection, filtering circuit, after preliminary processing of signals, the signals sent to acquisition card, complete the signal acquisition, and then the data into PC, data is stored and computed by PC, monitoring results of the insulated state of power cable metal shield shelves base on the calculation of circulation relations of the cable metal shield shelves. This invention with less judgment error, no cable damage, through accident prevention of power cables to extend life of power cables, it assure the purpose safe and stable running of power cables.

Description

technical field [0001] The invention relates to an online monitoring method and a monitoring device for the insulation state of the metal sheath of a power cable, which are used to ensure the safe and stable operation of the power cable line. Background technique [0002] How to improve the safety of power cable operation is a crucial link in the reliability of power system power supply. Both at home and abroad have invested a lot of money and energy in researching power cable performance and various protections. The basic structure of a power cable includes three parts: a conductive core, an insulating layer and a protective layer: the conductive core is used to transmit electrical energy; the insulating layer acts as an insulation isolation, that is, the main insulation of the power cable; the protective layer protects the main insulation from external forces damage and moisture intrusion. There are three types of protective layers, namely metal sheath, rubber-plastic she...

AI Technical Summary

Problems solved by technology

For example, in 1999, the outer insulation of the metal sheath of the high-voltage cable in Huangpu Power Plant was damaged, resulting in multi-point grounding of the metal sheath, which caused damage to the main insulation of the cable, resulting in an explosion of the cable, which brought huge economic losses to the power plant.

In 2000, in the cable preventive test of the Guangzhou Cable Management Institute, the insulation resistance measurement test was carried out on the cable outer sheath of a total of 340 small sections (that is, the cable section formed between two joints or terminals) of the 25-circuit high-voltage cable line cross-connection system. The results show that the insulation resistance of 64.4% of the high-voltage cable outer sheath does not meet the requirements of the regulations, and the insulation resistance of the metal sheath of individual cables is only tens of ohms, which makes it impossible to carry out the DC withstand voltage test and wastes a lot of resources. If it is not handled properly in time, It will inevitably lead to cable accidents

The metal sheath insulation DC resistance measurement method is simple and convenient, but the judgment error is large and the reliability is poor

The location of the fault point can be detected by the impact high-voltage flashover sound measurement method, but it must be measured offline, and it has a destructive effect on the insulation performance of the cable. The location of the fault point is greatly affected by the external complex environment.

The cable fault tester on the market is developed by using the pulse method or the impact flashover method. However, due to the reflection waveform of the fault point of the cable metal sheath, it is transmitted to the cable fault tester along the outer graphite coating of the cable metal sheath and the ground. The loss is large, and the measurement accuracy of the instrument is also poor

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