| Circuit breakers are used in the electrical power system to protect electrical power devices during failures caused by various breakdowns. It protects the equipment from being damaged under situations such as overload, short-circuit, undervoltage, electric leakage and earthing. A release, being the core functional unit of detection and control in breakers, detects electrical parameter of the circuits being protected and breaks the connection when certain conditions are met. The intelligent release is an innovative remote-control model without any physical connections with high-voltage switchgear. In transfer switching operations, by using an intelligent release one can shut down only one switching device, as compared with the old complicated practice of shutting down the whole bus. Therefore, steps are greatly reduced, and the risk assessments of safety production are highly improved. Since large-scale implicated electricity failure is minimized, it resolves contradictions between safety production and mass supply.When looking back on the development of releases, one can find that they evolved from mechanical, electromagnetic and electrothermal model, all the way to intelligent releases with microprocessor, which can detect faults, control circuit and display status. However, most of the domestic intelligent releases are designed with low class 51 series processors, and owing to the limitation of resources and computed speed, these intelligent releases cannot achieve many functions and have poor stability. The releases are widely used. In all transformer stations, over 80% of the cubicle switchboard are vertically-fixed ones or trolley ones which are equipped with separating brake release buttons on the panel. If the microcomputer protection device is placed under conditions of high voltage, intense electromagnetic field and high temperature, the ageing device will not function properly. Moreover, the protection device, namely EPROM, goes wrong from time to time, leading to reversion failure of the control device. When the remote-controlled plug-in in the detect and control device breaks down, the secondary circuit is seized at the circuit contact and hence switched on for a long time, the electric resistance of the coil increases dramatically so that the coil of divide-shut brake will be burnt out, causing failures of remote control and suspension of normal operation. Therefore, in accordance with regulations made by the China Southern Power Grid concerning power transformation, in an attempt to ensure safety operations, operators must adopt default and defect mechanism and stop power supply of the bus at higher level, whereas any on-the-spot release braking is strictly prohibited.At the beginning, the thesis analyze the main causes for remote-control failure of switch equipments and offers resolutions accordingly. Secondly, in order to accommodate to the current division of labor in power transformation, i.e. staff on duty are not allowed to fix the default of protection device, but he can use a remote-controlled release with a trolley, the author has designed a remote-controlled intelligent release for a 10kV switch, which are safe, reliable, rapid, automatic, universal and highly cost-effective. The paper introduces in detail the principle, configuration and application of the new intelligent release, and gives test data at the end. Practice proves that the intelligent release achieves good performance, high cost-effectiveness and has sound effect in practice. |
PDF Full Text Request