A brief description of the structure, performance and principle of DC voltage divider

作者： GOZ Electric 时间：2014-05-06 09:50:27 阅读：14

1 Overview

In order to ensure that the high-voltage direct current transmission system has reliable regulation and protection functions, there must first be available and reliable system data.

According to the data, a complete measurement system should be set up at the converter station. DC voltage divider is an important part of high voltage DC transmission system. It is an indispensable component to realize the control and protection sampling of high-voltage direct current transmission system, and provides the necessary collection amount for the corresponding control and protection. The following is a brief introduction to the structure, performance and principle of the DC voltage divider.

2 Working principle

In the high-voltage DC circuit, a DC voltage divider is connected in parallel, the voltage at both ends of the voltage divider is measured, and then the voltage is converted into a digital quantity, which is transmitted through optical fiber and used as electrical isolation to transmit the digital quantity to the corresponding control or protection.

3 Basic structure

An introduction to the structural part of a DC voltage divider. A DC voltage divider consists of a high voltage part and a low voltage part. The high voltage part is some

    Resistors and capacitors are first connected in parallel and then in series. The design principle of the low-voltage part is similar to that of the high-voltage part, and is equipped with a protective discharge gap. The common feature of both is that they take the same time constant. If the conditions are met, the voltage transformation ratios of DC and AC are the same, and the accuracy of AC measurement can reach 10kHz. The protective low-voltage value of the discharge gap F will not cause damage to the components of the low-voltage circuit. The rated output voltage of the DC voltage divider at rated load is equal to the rated voltage of the primary side. The load is mounted on the bottom output connector located on the DC voltage divider. The high voltage capacitor is installed directly inside the resistor coil. These resistors are sealed with epoxy resin and placed in a vacuum. According to the level of the voltage taken, the corresponding series and parallel connections are made. There is a control terminal box at the bottom, with optical fiber connections and corresponding circuit boards inside.

Field application of 3 voltage dividers

1) Signal measured by voltage divider

During the voltage divider debugging process, there are 11 types of debugging items for overvoltage testing: AC filter switching test, converter transformer and valve group charging test, unlocking performance test, locking performance test, emergency shutdown tripping test, DC filter switching test, metal ground return mode conversion, commutation failure (lost) pulse test, the last AC circuit breaker tripping, DC line ground fault, AC line single-phase ground short-circuit fault.

In each test, a large amount of overvoltage data and waveforms were extracted at the test point through the voltage divider. Through these data and waveforms

Through analysis, you can understand the characteristics of the measured overvoltage and whether it meets the engineering requirements.

2) Analysis of waveform measured by voltage divider

1) AC side waveform

The waveform reflects that the response speed of the voltage divider is sufficient to meet the test requirements.

   in conclusion

    The working principle and internal structure of the DC voltage divider are analyzed. According to the measured waveform research, the response speed of the voltage divider meets the test requirements, and the voltage signal extracted by the voltage divider can correctly reflect the process of ground fault occurrence.