XGN-12 Fully Insulated and Sealed Gas-Insulated Ring Main Unit

The XGN-12 box-type fixed metal-enclosed switchgear (hereinafter referred to as the switchgear) is primarily used in 3.6 KV, 7.2 KV, and 12 KV three-phase AC 50 Hz indoor systems, making it particularly suitable for frequent operation scenarios. This switchgear complies with the standards GB3906 and IEC298 and features a rigorous "five-prevention" interlocking function.

The main switch utilizes the ZN28 series split-type vacuum circuit breaker or vacuum contactor, while the isolating switch employs the GN30-10 rotary type and the GN22-10 current isolating switch.

1. Environmental Conditions

Ambient temperature: upper limit +40°C, lower limit -25°C;

Relative humidity: daily average not exceeding 95%, monthly average not exceeding 90%;

Altitude: not exceeding 1000 m;

2. Installation

The dynamic load generated by the vacuum circuit breaker during opening and closing is approximately 7840 N upward and downward, which should be considered for estimating foundation stress during design.

The construction of the switchgear installation foundation should comply with the relevant provisions of the "Technical Code for Construction and Acceptance of Electric Power Construction."

3. Installation Procedures and Precautions:

a. Use specific transportation tools such as cranes or forklifts; rolling or prying with crowbars is prohibited.

b. Place the switchgear on the foundation according to the arrangement sequence, adjust the straightness, verticality, and levelness of the switchgear group, and secure the switchgear to the foundation channel steel. Use appropriate bolts to fix the cabinets together.

c. Install the main busbar: Open the top cover plate of the busbar chamber for installation. After installation, tighten the top cover plate. When connecting the busbars, ensure the contact surfaces are flat and free of contaminants. Clean any contaminated areas and apply power composite grease to enhance conductivity.

d. Install primary cables: After the cable heads are prepared, fix them on the support. The contact surface between the cable and the busbar should be flat. Apply power composite grease to the contact surface before connection. After cable installation, use partitions to seal the cable chamber from the cable trench.

e. Install secondary cables: Thread the cables through the bottom left side of the cabinet and into the relay room through the side wall, then connect them to the corresponding terminals. During installation, ensure that cable numbers and terminal numbers are not missed or misconnected. After secondary cable installation, remember to seal the cable holes.

f. Connect the grounding busbars between cabinets to integrate the grounding busbars along the switchgear arrangement direction. Check for any omissions in working grounding and protective grounding, and ensure the grounding circuit is continuous and conductive. The working grounding resistance should not exceed 10 ohms, and the protective grounding resistance should not exceed 4 ohms.

4. Preparations Before Acceptance Testing and Commissioning

(1) Acceptance Test Items

① Check whether the switchgear model and specifications match the order data;

② Check for loose fasteners and tighten any found immediately;

③ Check whether the contact surfaces of the busbar connections are tight;

④ Manually operate the isolating switch, circuit breaker, mechanical interlocking, and other items 3–5 times. They should operate flexibly without sticking, with accurate actions and correct procedures;

⑤ Check whether the secondary wiring conforms to the drawing requirements. Conduct an action test on the secondary circuit with the main circuit de-energized. All relays should operate accurately and reliably, meeting design requirements;

⑥ Measure the main circuit resistance. Due to the variety of switchgear configurations and significant differences in resistance values, the measurement is temporarily focused on the circuit breaker and electrical connection terminals. The circuit breaker should not exceed its standard specified value, and the electrical搭接 parts should not exceed 10 micro-ohms. Use the DC voltage drop method for measurement, applying a 100 A DC current and measuring the voltage drop;

⑦ Test the insulation strength of the secondary circuit. Apply an AC 50 Hz, 2000 V voltage between the conductor and the enclosure for 1 minute. There should be no breakdown or discharge. For parts of the secondary circuit with electronic devices, the test voltage should be negotiated between the manufacturer and the user;

⑧ Perform the power frequency withstand voltage test on the main circuit. Apply AC 50 Hz between phases and between phase and ground. According to the rated voltage of the switchgear, apply 85% of the value specified in GB311.1—83 for 1 minute. There should be no breakdown or flashover.

(2) Preparations for Commissioning

① Lubricate moving friction and transmission parts;

② Connect the control, signal, and lighting power sources;

③ With the isolating switches and circuit breakers of other switchgear in the open position, energize the main busbar and commission the incoming line cabinet according to the specified operating procedures;

④ Close the isolating switch of the voltage transformer cabinet and check whether the voltmeter indicates correctly. If correct, proceed;

⑤ Close the isolating switches of the lightning arrester and station transformer, and commission related auxiliary devices;

⑥ Close the isolating switches and circuit breakers of the feeder cabinets in sequence and check whether the ammeter indicates correctly.