1. Introduction Disconnect switches play a crucial role in power systems, including isolating power sources, changing system operating modes, switching small load currents, and performing switching operations. Due to their relatively simple operating principle and structure, there are usually no strict overhaul cycles, and they are typically overhauled along with the main equipment. However, with the recent shift towards oil-free circuit breaker upgrades, unmanned substation upgrades, and the gradual transition of substation equipment from periodic maintenance to condition-based maintenance, the overhaul cycle of main equipment is gradually lengthening. Consequently, problems with outdoor disconnect switches in operation have increased significantly, directly affecting the reliability and safety of the power supply system, and in severe cases, even causing a complete busbar outage in a substation. This paper analyzes some problems encountered during the installation and commissioning of the GW4-126 disconnect switch in the newly built #161 bay of the 110kV Baihe Power Plant, compares the differences between the two with the GW4-110 disconnect switch, and proposes solutions to the problems. 2. Structural Differences Between GW4-110 and GW4-126 Disconnect Switches: Both the GW4-110 and GW4-126 series high-voltage disconnect switches are single-phase, double-column structures, mainly composed of a base frame, rod-shaped post insulators, and conductive parts. Each phase has two post insulators, mounted on bearing seats at both ends of the base frame, connected by cross rods, and can rotate horizontally at a 90-degree angle. The conductive disconnect switch is divided into two halves, each fixed to a post insulator, with the contact point between the two post insulators. The terminals can be either rigidly connected or rigidly connected. The GW4-126 disconnectors used in the newly built #161 bay of the 110kV Baihe Power Plant are advanced disconnectors manufactured by Xikai, while the disconnectors currently used by our bureau are basically the older GW4-110 models. The structural differences are as follows: 1) The middle contact section; 2) The contact fingers. The GW4-110 disconnector's contact fingers consist of two rows of four finger pieces with a very small spacing. The contact between the contact and the finger is a line contact, and the two rows of finger pieces are held together by two springs. The GW4-126 disconnector's contact fingers consist of two rows of six finger pieces (see diagram below), with a finger spacing of 1-2mm. The contact between the contact and the finger is a line contact, and the two rows of finger pieces are held together by six springs outside the finger pieces. 3) Limiting pins for opening and closing positions: The GW4-110 type disconnect switch has a limiting pin for opening and closing positions at the lower end of the transmission plate of each phase disconnect switch bearing seat. Adjustment of these limiting pins determines the opening and closing positions of the three phases of the disconnect switch. The GW4-126 type disconnect switch does not have limiting pins for opening and closing positions at the lower end of the transmission plate of each phase disconnect switch bearing seat. Instead, there are limiting pins on the left and right sides of the disc-shaped crank arm connected to the disconnect switch base above its operating mechanism, thus ensuring the determination of the opening and closing positions. 4) Inter-pole connecting rod connection: The inter-pole connecting rod between each phase disconnect switch of the GW4-110 type disconnect switch is connected to the lower connecting plate of the transmission plate of the bearing seat. Generally, the lower connecting plate is welded to ensure the opening and closing operation of the disconnect switch. 5) Regarding the linkage debugging of the main disconnect switch and mechanism: When debugging the GW4-110 disconnect switch, we use the handle to turn the mechanism to the open/closed terminal position, and connect the connecting plate to the bearing seat of the main disconnect switch via the connecting rod. During the debugging of the GW4-126 disconnect switch, we found that if the above method is used, a rebound phenomenon occurs after the handle is turned to the closed terminal position. In severe rebound cases, the contact and contact finger are in a barely contacting state, which cannot guarantee the normal operation of the disconnect switch. 6) Difference in the appearance of the intermediate contact: The GW4-110 disconnect switch has a rain cover for the intermediate contact, which serves to prevent dust and rain. The GW4-126 disconnect switch does not have a rain cover and is exposed for a long time. 3. Regarding the problems and solutions for improving the disconnect switch: 1) Regarding the contact surface problem: During the installation of the GW4-126 disconnect switch, it was found that a row of intermediate contact fingers were deformed, causing only 5 intermediate contacts to be in contact when the main disconnect switch is just closed, thus reducing the contact area. Because the contact surface of the GW4-126 disconnector is a line-to-line contact, in order to maximize the contact area, it is necessary to ensure that the insertion depth of the intermediate contact, i.e., the intermediate gap, meets the conductivity requirements of this type of disconnector (16-21mm) when in the closed position, and the vertical difference between the conductive tube and the contact is no more than 5mm. It is also necessary to ensure that the intermediate contact does not generate greater lateral compressive stress on the spring contact finger during the closing process. The quality and appearance of the contact finger are also important parameters determining the conductivity performance. The silver plating coating on the contact surface of the contact finger should not peel off, and the surface should be free of burrs and oxidation. For disconnectors in operation, regular checks should be conducted on the conductive contact surface for peeling of the silver plating coating, surface burrs, oxidation, etc. 2) Limiting the Opening and Closing Positions: The GW4-126 disconnector does not have limiting stop pins for the opening and closing positions at the lower end of the bearing seat transmission plate of each phase disconnector. Instead, there are limiting stop pins on the left and right sides at the disc-shaped crank arm connector above the operating mechanism connected to the disconnector base, to ensure the determination of the opening and closing positions. During commissioning, as long as the primary phase disconnector and operating mechanism can be properly linked and positioned to meet conductivity requirements, the subsequent two phase disconnectors can be jointly commissioned. However, in reality, relying solely on the primary phase to determine the opening and closing positions places higher demands on the commissioning of the opening and closing positions of the subsequent two phase disconnectors. It requires both three-phase synchronization and the insertion depth of the single-phase intermediate contact, reducing the adjustable surface area and increasing the difficulty of commissioning. Therefore, during commissioning, joint commissioning should be performed first. Adjustments should be made based on the three-phase synchronization and the insertion depth of the intermediate contact, using methods such as adjusting the horizontal connecting rod, inter-pole connecting rod, the clearance of the bearing seat transmission plate fixing bolts, and the clearance of the outlet seat fixing bolts. 3) Regarding the linkage commissioning of the primary phase of the main disconnector and the mechanism: During commissioning, it was found that when the handle is turned to the closing terminal position and the primary phase of the main disconnector is connected to the mechanism, after one opening and closing operation, the intermediate contact exhibits a rebound phenomenon during closing. In severe rebound cases, the contact and the contact finger are in a barely contacting state, which cannot guarantee the normal operation of the disconnector. When debugging the linkage between the main disconnect switch and the mechanism of the GW4-126 type main disconnect switch, the main disconnect switch should first be placed in the closed position. After turning the handle to the open/close terminal position, reverse the rotation to ensure consistency on both the open and close sides, and then connect the main disconnect switch to the mechanism. 4) The middle contact of the GW4-126 type disconnect switch does not have a rainproof cover. Since this disconnect switch is installed in a thermal power plant, it is subject to heavy dust pollution, which is very detrimental to long-term operation and affects its conductivity. 4. Conclusion By comparing the GW4-110 type disconnect switch and the GW4-126 type disconnect switch, it is not difficult to find subtle differences in structure, resulting in differences in debugging methods. Familiarity with the manufacturing processes and debugging methods of various equipment will greatly improve our work efficiency. Accidents caused by disconnect switch failures can lead to equipment damage or even large-scale power outages, which we must pay sufficient attention to. During installation, process quality management should be strengthened, and flexible handling should be carried out according to the equipment's own structure. For daily inspections, the operating status of the equipment should be grasped in a timely manner, and the cause of any faults should be identified and the hidden dangers eliminated as soon as possible to ensure the safe and reliable operation of the power grid.