By sion932 
Abstract: Sulfur hexafluoride (SF₆) gas is widely used in electrical equipment due to its excellent insulation and arc-extinguishing properties, and the purity of SF₆ gas directly affects the operational safety and reliability of electrical equipment. T/CEC 140-2017, a group standard issued by the China Electricity Council, specifies the measurement method for the purity of SF₆ gas in SF₆ electrical equipment. This article systematically elaborates on the background, scope of application, core technical requirements, measurement principles and procedures, as well as the application value and significance of T/CEC 140-2017. It aims to provide technical reference for relevant practitioners in the power industry to accurately grasp and apply this standard, and further ensure the safe and stable operation of power systems.
Keywords: T/CEC 140-2017; SF₆ electrical equipment; SF₆ gas purity; measurement method; power system safety
1. Introduction
In the field of power transmission and transformation, SF₆ electrical equipment has become a key component of modern power systems because of its advantages such as compact structure, high reliability and low maintenance cost . However, the purity of SF₆ gas in the equipment is a crucial factor affecting its performance. Impurities such as air, moisture and decomposition products in SF₆ gas will reduce its insulation performance, increase the risk of equipment breakdown, and even lead to serious power outages. Therefore, accurate measurement of SF₆ gas purity is of great significance for the routine inspection, maintenance and fault diagnosis of SF₆ electrical equipment.
To standardize the measurement method of SF₆ gas purity in China’s power industry, the China Electricity Council issued the group standard T/CEC 140-2017 “Measurement Method for Purity of Sulfur Hexafluoride Gas in Sulfur Hexafluoride Electrical Equipment” on May 15, 2017, which was officially implemented on August 1 of the same year . This standard fills the gap in the field of SF₆ gas purity measurement in China’s power industry to a certain extent, provides a unified technical basis for relevant testing work, and plays an important role in improving the level of equipment operation and maintenance and ensuring the safe and stable operation of the power grid.
2. Overview of T/CEC 140-2017
2.1 Background of Standard Formulation
With the rapid development of China’s power industry, the number of SF₆ electrical equipment has increased significantly. However, before the formulation of T/CEC 140-2017, there was a lack of unified and standardized measurement methods for SF₆ gas purity in the industry. Different testing institutions and enterprises adopted different measurement techniques and procedures, resulting in large differences in measurement results, which could not effectively guide the practical work of equipment operation and maintenance. In order to solve this problem, the State Grid Hunan Electric Power Company and other units undertook the task of drafting the standard, and completed the formulation of the standard after in-depth research, experiment and demonstration .
2.2 Scope of Application
T/CEC 140-2017 specifies the measurement method for the purity of SF₆ gas in SF₆ electrical equipment. The standard is applicable to the purity measurement of SF₆ gas in various SF₆ electrical equipment such as SF₆ circuit breakers, gas-insulated switchgears (GIS), SF₆ transformers and SF₆ bushings used in power systems. It should be noted that this standard is not applicable to the measurement of other gas components in SF₆ electrical equipment, nor to the purity measurement of SF₆ gas in non-electrical equipment.
3. Core Technical Requirements of T/CEC 140-2017
3.1 Requirements for Measurement Equipment
T/CEC 140-2017 has clear requirements for the measurement equipment used for SF₆ gas purity measurement. The measuring instrument should have good stability and accuracy, and its measurement range and precision should meet the relevant technical requirements. Generally, gas chromatographs or special SF₆ gas purity analyzers are recommended. Before use, the measuring instrument must be calibrated in accordance with relevant regulations to ensure the reliability of the measurement results. In addition, the standard also requires that the auxiliary equipment such as gas sampling pipelines and valves used in the measurement process should be compatible with SF₆ gas, without leakage or adsorption, so as to avoid affecting the accuracy of the measurement results.
3.2 Requirements for Measurement Environment
The measurement environment has a significant impact on the accuracy of SF₆ gas purity measurement. T/CEC 140-2017 stipulates that the measurement should be carried out in a clean, dry and well-ventilated environment, avoiding the influence of dust, moisture, corrosive gas and other factors. The ambient temperature should be controlled within the range of (15 ~ 35) °C, and the relative humidity should not exceed 85%. At the same time, the measurement site should be free from strong electromagnetic interference to ensure the normal operation of the measuring instrument.
4. Measurement Principle and Procedure of T/CEC 140-2017
4.1 Measurement Principle
The measurement method specified in T/CEC 140-2017 is mainly based on the principle of gas chromatography or thermal conductivity detection. For the gas chromatography method, the sample gas is separated into different components through a chromatographic column, and then the separated components are detected by a detector. The purity of SF₆ gas is calculated according to the peak area or peak height of each component. For the thermal conductivity detection method, it is based on the difference in thermal conductivity between SF₆ gas and other impurity gases. When the sample gas passes through the thermal conductivity detector, the change of thermal conductivity will cause the change of the detector’s output signal, and the purity of SF₆ gas can be obtained by processing the signal.
4.2 Measurement Procedure
The measurement procedure specified in T/CEC 140-2017 mainly includes the following steps:
- Sample Collection: Before sampling, the sampling pipeline and valve should be purged to remove the air and other impurities in the pipeline. Then, the sample gas is collected from the SF₆ electrical equipment in accordance with the relevant sampling requirements. The sampling process should be carried out slowly to avoid the generation of eddy currents and the mixing of air. The volume of the sample gas should be sufficient to meet the measurement requirements.
- Instrument Preparation: Turn on the measuring instrument and preheat it to the specified temperature. Then, calibrate the instrument with standard gas of known purity to ensure that the instrument is in a normal working state.
- Sample Injection: Inject the collected sample gas into the measuring instrument in accordance with the operating requirements of the instrument. The injection volume and injection speed should be controlled stably to ensure the repeatability of the measurement results.
- Measurement and Data Processing: After the sample gas is injected, the measuring instrument will automatically complete the separation and detection of the gas components. The instrument will output the measurement data, and the relevant personnel will calculate the purity of SF₆ gas according to the data processing method specified in the standard. At the same time, the measurement data and related information should be recorded in detail.
- Instrument Shutdown and Maintenance: After the measurement is completed, turn off the measuring instrument in accordance with the operating procedures, and clean and maintain the instrument and auxiliary equipment to ensure their service life and performance.
5. Application Value and Significance of T/CEC 140-2017
5.1 Ensuring the Safe Operation of Electrical Equipment
By standardizing the measurement method of SF₆ gas purity, T/CEC 140-2017 enables relevant practitioners to accurately grasp the purity status of SF₆ gas in electrical equipment. Timely detection of unqualified SF₆ gas purity can help maintenance personnel take corresponding measures such as gas replacement and equipment maintenance in a timely manner, thereby avoiding equipment faults caused by impure SF₆ gas and ensuring the safe and stable operation of electrical equipment.
5.2 Improving the Level of Industry Standardization
The formulation and implementation of T/CEC 140-2017 have unified the technical requirements and operation procedures for SF₆ gas purity measurement in the power industry. It has changed the situation of non-uniform measurement methods in the past, improved the comparability and reliability of measurement results, and promoted the standardization and normalization of SF₆ gas testing work in the industry. At the same time, this standard also provides a technical basis for the supervision and inspection of relevant departments.
5.3 Promoting the Development of the Power Industry
Accurate measurement of SF₆ gas purity is an important guarantee for the normal operation of SF₆ electrical equipment. T/CEC 140-2017 provides strong technical support for the application and promotion of SF₆ electrical equipment. It helps to improve the reliability and service life of SF₆ electrical equipment, reduce maintenance costs, and then promote the healthy and sustainable development of the power industry.
T/CEC 140-2017 is an important group standard in the field of SF₆ electrical equipment testing in China’s power industry. It has important guiding significance for standardizing the measurement method of SF₆ gas purity, ensuring the safe operation of electrical equipment and improving the level of industry standardization. Relevant practitioners in the power industry should deeply understand and strictly implement the requirements of this standard, master the core technical points of measurement, and continuously improve the accuracy and reliability of SF₆ gas purity measurement results. In the future, with the continuous development of power technology, it is necessary to further revise and improve T/CEC 140-2017 in combination with the actual needs of the industry to better adapt to the development of the power industry.
References
[1] China Electricity Council. T/CEC 140-2017, Measurement Method for Purity of Sulfur Hexafluoride Gas in Sulfur Hexafluoride Electrical Equipment[S]. Beijing: China Electricity Council, 2017.
[2] Safety Management Network. Measurement Method for Purity of Sulfur Hexafluoride Gas in Sulfur Hexafluoride Electrical Equipment – T/CEC 140-2017[EB/OL]. 2018-03-13. http://m.safehoo.com/Standard/Trade/Electric/201803/1514901.shtml.
[3] Yun Biaozhun. China Electricity Council (T/CEC) Group Standard Download[EB/OL]. 2025-09-26. https://www.yunbiaozhun.com/category/600125.html.