Detailed Explanation of Power Supply Process for High and Low Voltage Switchgear Project

In the construction of power systems, the power supply process of high and low voltage cabinets is a crucial step for ensuring the safe and stable operation of power equipment.

A standardized power supply process not only enhances project efficiency but also effectively avoids potential risks. The following is the standardized power supply process and key precautions for conventional high and low voltage cabinet projects.

I. High-voltage cabinet power-on procedure

Equipment positioning and container assembly
Position the high-voltage cabinet precisely according to the design drawings, and adjust its level and verticality.
The cabinet body is assembled using bolts or welding to ensure a stable structure.
Installation of the bushing and connection to the busbar
Install the high-voltage bushing, and connect the high-voltage incoming and outgoing cables.
The connection of the busbars must strictly follow the electrical drawings to ensure that the contact surfaces are smooth and the tightening torque meets the standards.
Chain line and functional testing
Complete the inter-cabinet interlock lines (such as the interlock between circuit breakers and disconnectors) and the internal interlock lines in the electrical room (to transformers, AC/DC screens, etc.);
Test the functions of the internal components (such as relays, instrument displays, and protection device action logic) of the power-on test cabinet.
Third-party testing and acceptance inspection
Entrust professional institutions to conduct high-voltage switch withstand voltage tests, transformer insulation tests, and verification of the protection functions of the secondary circuit;
The problems identified during the rectification test (such as incorrect wiring, mismatched component parameters).
Fixed value input and power supply
Input protection device settings (such as overcurrent and instantaneous protection parameters);
Step-by-step power supply: First, supply power to the high-voltage side. After confirming there are no abnormalities, supply power to the low-voltage side. Finally, put the load side into operation.

II. Power Supply Process for Low-Voltage Switchgear

Connecting the panel assembly to the main busbar
After the low-voltage cabinets are positioned, they are assembled into rows, and the main busbars and branch busbars are connected to ensure the electrical conductivity and mechanical strength.
Chain line and functional testing
Complete the inter-cabinet interlock lines (such as the linkage between the incoming cabinet and the bus tie cabinet) and the feeder circuit tests;
Test the functions of circuit breaker opening and closing, instrument indication, and fault alarm.
Third-party testing and rectification
Carry out tests on the characteristics of low-voltage switches and insulation tests for cable withstand voltage.
Rectify the problems such as poor grounding and incorrect phase.
Power Supply and Acceptance Inspection
Low-voltage side is gradually energized to verify the operating status of each circuit.
After passing the acceptance inspection, it will be put into use and the operation manual and maintenance records will be transferred simultaneously.

III. Key Points to Note

Principles of Safe Operation
Sequentially strict: Always follow the principle of “high voltage first, low voltage later, power supply side first, load side later”, and perform reverse operations during power outages.
Electrical testing and grounding: Before powering on, use an electrical tester to confirm that there is no residual voltage. The high-voltage cabinet must be reliably grounded.
Critical point inspection
PT cabinet (voltage transformer cabinet): Focus on inspecting the secondary circuit wiring to prevent false connections that could lead to measurement errors or protection malfunctions;
Temperature control and ventilation: After the box transformer is energized, it is necessary to check the temperature control system, the operation status of the fans, and the three-phase temperatures of the transformer.
Screw tightening: The screws of the busbars in the high-voltage cabinet and the connection terminals of the plastic-case circuit breakers in the low-voltage cabinet need to be rechecked twice to prevent loosening and overheating.
Special Scenario Prevention
Prefabricated module project: If no metering devices are installed, the current circuit should be short-circuited in advance to avoid the risk of open circuit.
Historical lesson: Based on the case of the Nenjiang project, strengthen the inspection of PT (voltage transformer) installation procedures to prevent explosion accidents.

Conclusion：

The standardized power transmission process is the cornerstone of power quality. Through rigorous testing, strict acceptance, and meticulous inspection, the failure rate can be minimized to ensure the long-term stable operation of the power system.

It is recommended that the engineering team keep complete records during the implementation process to provide data support for subsequent maintenance.