Preliminary guidelines for the design of digital pressure, temperature, and partial discharge meters for GIS equipment

2025-04-24 17:38:44

1、 Design Overview

GIS (Gas Insulated Switchgear) equipment uses SF6 gas as the insulation and arc extinguishing medium, enclosing primary equipment such as circuit breakers and isolating switches in a metal grounded enclosure. This guideline focuses on the pressure, temperature, and partial discharge measurement functions of GIS equipment, and provides design specifications for digital meter products, clarifying sensor selection, technical implementation, alarm strategies, and other contents. The aim is to achieve monitoring and intelligent warning of equipment operation status through digital means, while addressing potential environmental factors affecting SF6 gas.

2、 Pressure measurement design

（1） Sensor selection

Adopting a diffusion silicon pressure sensor, stainless steel diaphragm is selected for SF6 gas to produce corrosive substances under special conditions. Stainless steel membrane has excellent corrosion resistance, which can resist potential corrosion risks, and can stably transmit gas pressure to silicon wafers. Based on the principle of piezoresistive effect, pressure measurement is achieved through the characteristic of silicon wafer resistance value changing with pressure.

（2） Installation and Technical Parameters

The sensor is built into the GIS chamber and connected to the intelligent monitoring unit of the digital meter through signal lines. The high mechanical strength and chemical stability of the stainless steel diaphragm ensure reliable operation of the sensor under complex working conditions, with a pressure measurement accuracy of ± 0.5% FS, and can quickly respond to pressure changes. The digital meter collects real-time SF6 gas pressure data and compares it with a preset threshold. When there is an abnormal pressure (such as a decrease due to leakage), the alarm mechanism is immediately triggered, and the data and alarm information are uploaded to the backend system through RS485 communication.

3、 Temperature measurement design

（1） Sensor selection

Select an externally mounted PT100 thermistor sensor, which is made of platinum material and utilizes the characteristic of approximately linear variation of resistance value with temperature to achieve temperature measurement.

（2） Installation method

By using thermal conductive adhesive and fixtures, the sensor is fixed and installed at the switch position of the GIS equipment, ensuring direct contact with key temperature measurement points to obtain accurate temperature data. The temperature measurement range of the sensor is set to -40 ℃ -80 ℃, with an accuracy of ± 0.3 ℃.

（3） Power supply and signal transmission

Adopting an external 12V or 24V DC power supply to ensure stable operation of the sensor. The temperature data collected by sensors is transmitted to digital meters through shielded signal lines, and the meters convert the data into RS485 communication signals for output, facilitating centralized data processing, remote transmission, and integration with other intelligent systems.

（4） Alarm strategy

1. Daytime monitoring: The digital meter is equipped with an external light sensor, which dynamically adjusts the temperature threshold based on the intensity of sunlight to prevent false alarms caused by direct sunlight. When the temperature exceeds the dynamic threshold by 10%, a warning prompt is triggered and the warning information is displayed synchronously through the meter display screen and the backend system.

2. Night monitoring: A fixed temperature threshold is used. When the temperature exceeds 75 ℃, the digital meter immediately triggers an audible and visual alarm and sends a fault code to the background through RS485 communication. At the same time, the meter continuously records temperature data. If there are three consecutive abnormal temperature fluctuations (fluctuation range>5 ℃/10 minutes), an alarm will also be triggered to improve the accuracy of nighttime fault diagnosis.

4、 Partial discharge measurement design

（1） Sensor selection

1. Ultra high frequency (UHF) sensor: used to detect 300MHz -3GHz electromagnetic wave signals generated by partial discharge, with a detection sensitivity of up to 1mV, which can effectively avoid power frequency interference in the power system and achieve accurate positioning and type recognition of partial discharge.

2. Ultrasonic (AE) sensor: captures the mechanical vibration waves generated during the discharge process from 20kHz to 200kHz. By installing multiple sensors on the equipment casing and utilizing the principle of time difference positioning, partial discharge point positioning can be achieved with an accuracy of up to 10cm.

（2） Installation and Technical Implementation

Doppler ultrasonic flowmeter brings you professional service,the UHF sensor is installed inside the GIS cavity or at the bowl insulator, while the AE sensor is fixed on the surface of the equipment casing by magnetic attraction or application of coupling agent. The signals collected by the sensors are processed by the signal conditioning module and transmitted to the data analysis unit of the digital meter. The meter uses built-in artificial intelligence algorithms to diagnose the discharge type and issue timely fault warnings. At the same time, the relevant data and diagnostic results are uploaded to the backend management system through RS485 communication for remote monitoring and decision-making by operation and maintenance personnel.

5、 On site inspection arrangement

To further verify the feasibility and applicability of the digital meter design scheme, it is necessary to organize on-site inspections as soon as possible. The inspection content includes:

1. Equipment operation status: Observe the pressure and temperature trends of GIS equipment during actual operation, record the matching degree between digital meter monitoring data and actual working conditions, check the accuracy and timeliness of meter alarm system triggering, and evaluate the stability of data collection, processing, and transmission.

2. Investigation of working environment: Detailed understanding of factors such as temperature and humidity, electromagnetic interference intensity, ventilation conditions, etc. in the environment where the equipment is located, and evaluation of the impact of the environment on the performance of digital meter sensors and equipment operation. At the same time, collect operational data of equipment under different loads and seasons, and analyze the potential risks and adaptability of digital meters under working conditions.

3. Data collection and feedback: Obtain raw data of digital meter operation through on-site data collection equipment, and compare and analyze it with design expectations. Deeply communicate with operation and maintenance personnel, collect problems and improvement suggestions encountered in the daily maintenance of digital meter functions, operational convenience, and other aspects of equipment, and provide a basis for subsequent design optimization.

4. Doppler ultrasonic flowmeter brings you professional service,compliance with safety regulations: The inspection process strictly follows the on-site safety operation regulations for power equipment to ensure the safety of personnel and equipment. Communicate and coordinate with the unit to which the equipment belongs in advance, develop detailed inspection plans and emergency plans, and ensure the smooth progress of the inspection work.