Integrated field calibration of high-precision DC standard voltage divider

作者： GOZ Electric 时间：2024-07-21 09:18:22 阅读：14

With the continuous development of DC measuring devices in my country, my country has established a national standard for 1000kV DC voltage ratio, which has the conditions for value transfer of DC voltage transformers, and also has the ability to carry out on-site calibration of DC measuring devices at a rated voltage of 800kV. However, there are still some problems, such as the large size and weight of the test power supply and standard instrument, and the complex assembly and disassembly, which are not conducive to long-distance transportation and on-site installation; the standard instrument is designed for the laboratory environment, and the calibration accuracy of the calibration equipment is also easily affected by the on-site environmental conditions. This paper conducts research on the integrated integration technology and vehicle-mounted platform of high-precision DC standard voltage divider and high-stability DC power supply, improves the efficiency, level and quality of the voltage divider error detection test, and has certain guiding significance for the current on-site inspection technology.

1. Research on the on-site calibration method of DC voltage transformer and the overall design of the integrated source device

Based on the traditional DC voltage divider calibration method used in the laboratory, a DC measuring device on-site calibration scheme is proposed. On this basis, the design schemes such as industrial frequency high-voltage power supply and high-frequency high-voltage power supply are studied, and the overall design scheme based on high-frequency high-voltage power supply is proposed. Finally, the key technology research of DC voltage standard for on-site use is carried out, and its equipment is developed. The basic principle and structural composition of the DC voltage transformer in the DC transmission system are analyzed. Based on the traditional DC voltage divider calibration methods used in the laboratory, including the difference measurement method, compensation method and voltage ratio method, the field calibration method of the DC voltage transformer is studied [4]. According to the output type of the DC measuring device to be measured, a field calibration scheme for the DC measuring device is proposed. The DC voltage transformer is calibrated on site.

2. Research on the automatic mechanical deployment technology of the vehicle-mounted platform

In order to facilitate the transportation, rapid assembly and disassembly of the 1100 kV high-stability DC voltage source on site, an integrated vehicle-mounted platform solution is designed. The integrated vehicle-mounted platform uses a hydraulic lifting device to realize lying transportation and erection on site. The platform bracket has high mechanical strength and can effectively bear the mechanical load of the mechanical erection mechanism, hydraulic support legs and lifting bracket mechanism. In the transportation state, the lifting bracket is in a nearly horizontal state, and the fixed mechanical erection mechanism, hydraulic support legs and lifting bracket mechanisms are all in a fixed locked state.

2.1 The hydraulic support unit uses hydraulic lifting to "erect the lifting bracket like a missile", thereby ensuring the insulation safety distance of the high-voltage test equipment on the lifting bracket to the ground. The lifting bracket is equipped with two high-voltage equipment fixing positions of the same size, which can be used to install high-voltage test equipment required for on-site calibration tests of DC voltage transformers such as high-stability DC voltage sources and standard voltage dividers. After unlocking the fixing device, the "missile erection" operation of the lifting bracket is performed using the integrated vehicle platform control software and PLC controller. The hydraulic support rod pushes the vertical axis rotation from both sides of the erection bracket to achieve a rotation range of 0°~100° until the erection bracket is completely vertical to the ground. At this time, the high-stability DC voltage source and DC high-voltage standard voltage divider on site are converted from the initial horizontal state to the working vertical state. During the erection process, the hydraulic support rod can continuously change the inclination angle through the program and control mechanism, and erect to the working state with maximum efficiency.

2.2 Airbag metal scale pressure-equalizing hood The airbag metal scale pressure-equalizing hood can solve the technical problems of not disassembling and dismantling the pressure-equalizing hood of the 1100kV high-stability DC voltage source and the 1100kV DC voltage standard divider for on-site use, and not installing the equipment on site. The pressure-equalizing hood is a pressure-equalizing hood composed of an inflatable inner liner and a scaly stainless steel sheet on the outer surface. The scales are electrically connected to each other in the middle to form a ring pressure-equalizing structure. Two electrode connection columns are set in the through hole of the central axis of the pressure-equalizing ring, one for connecting to the high-voltage output end of the electrical equipment, and the other for connecting the output high-voltage lead-out pipe. The metal bracket is made of aluminum alloy material and is connected to the pressure-equalizing hood through the mounting feet. The entire pressure-equalizing hood assembly is fixedly connected by the metal bracket and the high-voltage equipment through bolts. In order to ensure the rapid filling/deflation of the inner liner, it is equipped with a high-power electric filling/exhausting machine, which can inflate the pressure-equalizing hood to the working state or exhaust and shrink it to the storage and transportation state in a short time.

2.3 The power cabinet of the remote control box with high-stability DC voltage source on site is connected to the power control box by optical fiber or wireless connection to achieve complete isolation of the control unit and the high-voltage unit. A variety of electromagnetic compatibility shielding measures and multiple protections are adopted inside the control box. At the moment of flashover of the test product, it can ensure that the control box itself is not damaged by discharge and the personal safety of the operator can be guaranteed.

2.4 The power supply system of the integrated platform of the power distribution auxiliary system is managed and safely protected by a dedicated instrument power supply box. The total power supply of the integrated platform is connected to the total power socket on the adapter board, and the isolation switch is used as an obvious disconnection point. The instrument power supply box distributes the input total power supply to the hydraulic support unit, DC high-stability power supply, secondary measurement and control unit and other distribution units, and provides overcurrent, overvoltage and other protections for each distribution branch. In particular, a phase sequence automatic switching device is provided for the hydraulic support unit, without manual phase inversion.