GIS, which stands for Gas Insulated Switchgear, is typically used in voltage equipment above 35KV. GIS equipment is used as the switching device. During the manufacturing, transportation, and installation of GIS equipment, defects and errors in workmanship and cleanliness are inevitable. These defects affect the reliability of the GIS equipment and can only be detected through monitoring during operation. Under the influence of the electric field, partial discharge is prone to occur, which may lead to insulation breakdown of the GIS equipment. If inspections are not carried out promptly, it can endanger the safety of other equipment in the power station and cause power outages. Manual inspection is inefficient, and monitoring work is very passive.
What Causes GIS Partial Discharge?
The causes of GIS partial discharge are as follows:
SF6 gas in the GIS cavity contains free metal particles, accumulating electric charge;
The inside of the insulation components is not smooth and contains dust and impurities, leading to the deterioration of the insulator surface.
Uneven and rough welds on the inner surface of the casing and sharp burrs caused by friction during conductor installation resulted in electric field distortion.
Collisions during transportation and installation can cause collisions of internal floating structures and accumulation of electric charge.
Increased contact resistance due to oxidation of switch contacts during operation.
Poor contact and gaps in the conductive parts and floating components;
Burrs or sharp edges on the conductor surface;
GIS Partial Discharge Monitoring System
The environment of power transmission substations is usually harsh, with high voltage, high current, high magnetic fields, and adverse weather conditions such as rain, snow, and ice, which place high demands on partial discharge monitoring equipment. The partial discharge monitoring device uses high-frequency monitoring technology. Spatial ultra-high frequency partial discharge sensors are installed in the area near the GIS equipment to achieve long-distance global monitoring. Partial discharge sensors can also be bundled and installed on the outer casing of high-voltage equipment to monitor the insulation status of the high-voltage equipment in real time.
The online GIS partial discharge monitoring system has strong anti-interference capabilities, is suitable for long-term operation, and the collected data is uploaded to the partial discharge data collector in real time. After analysis and processing, the data can be viewed on the independent partial discharge monitoring host display screen. When the GIS equipment generates partial discharge, the partial discharge monitoring host interface will display it separately. Each device has an independent address, the data will not be mixed up, and the network configuration is flexible.
The online partial discharge monitoring system for GIS mainly consists of partial discharge sensors, a partial discharge data collector, and a partial discharge monitoring display screen. PD monitoring system for GIS typically involves installing ultra-high frequency (UHF) partial discharge sensors on the surface of the GIS equipment’s metal enclosure and the local control cabinet for simultaneous multi-point monitoring, ensuring data accuracy. The partial discharge sensors transmit data wirelessly via LoRa to a partial discharge data collector installed in the LCU (Local Control Unit) panel. After processing the partial discharge data, the data collector transmits it to an PD HMI (Human-Machine Interface) embedded in the LCU panel or other low-voltage cabinets, allowing users to view the data on the HMI.