Adjustment Test Operation and Precautions of High-Voltage Power Distribution Cabinets in Power Systems

1. Key Points for Debugging High-Voltage Power Distribution Cabinets in Power Systems

1.1 Voltage Control

During the debugging of high-voltage power distribution cabinets, voltage and dielectric loss show an inverse relationship. Insufficient detection accuracy and large voltage errors will lead to increased dielectric loss, higher resistance, and leakage. Therefore, it is necessary to strictly control the resistance under low-voltage conditions, analyze current and resistance values, and avoid excessive interference with voltage. After debugging, compare the results with existing data to ensure they meet the standards.

1.2 Control of Grounding Issues

Special attention should be paid to the grounding condition during cabinet debugging. Poor grounding of distribution cabinets often occurs during operation, accelerating the loss of transmission media. Abnormal grounding of the secondary circuit may cause deviations between actual values and nameplate values. In addition, due to the large capacitance between primary and secondary windings, improper grounding of the secondary winding will generate induced voltage and cause discharge.

1.3 Lead Wire Control

If the lightning protection system remains connected during lead wire operation or the lead wire joints are improperly handled, electrical faults are likely to occur. Conducting lead wire operations with faults will result in unreasonable dielectric analysis of voltage transformers and large errors in the obtained data. Therefore, when lightning protection equipment is in operation, useless lead wires should be removed, leakage problems caused by lead wires should be predicted, and insulation errors should be strictly controlled to ensure the debugging effect of the distribution cabinet. High-voltage power distribution cabinet debugging is susceptible to external interference; test parameter analysis can be performed in combination with median and data dispersion to improve data accuracy.

2. Precautions for Adjustment Test Operation of High-Voltage Power Distribution Cabinets in Power Systems

2.1 Conduct Pre-Test Inspections

Compared with other electrical equipment, high-voltage power distribution cabinets have different wiring methods and test standards. Therefore, thorough inspections must be carried out before each high-voltage test. Operators and supervisors should analyze the position of the voltage regulator, wiring method, and original state of instruments to ensure a certain distance from live parts. Safety protection measures should be used during inspections, and voltage can only be increased with the permission of the person in charge.

2.2 Strengthen Lead Wire Handling

During the adjustment test of high-voltage power distribution cabinets, staff should fully understand the function of lead wires and combine them with actual operations to standardize lead wire handling. When using lightning rods, unnecessary lead wires should be removed, leakage caused by lead wire problems should be predicted, and the error of the insulating tape should be controlled within a reasonable range using a microampere meter to improve the test effect of the high-voltage power distribution cabinet. 

The reverse wiring method and positive wiring method are used in high-voltage power distribution cabinet tests; the former is usually applied at construction sites, and the latter in laboratories. In addition, staff should use scientific measures to control voltage and analyze the impact of voltage and dielectric loss. Under low voltage, staff should control resistance values to ensure oxidation quality. In the measurement of absorption ratio, DC current should be analyzed to avoid affecting voltage stability. 

In the design of the double-arm bridge, the oxidation film and current conditions should be combined to determine the current value. Avoid oxidation film perforation, conduct reasonable analysis of resistance values, and prevent large voltage fluctuations. After the high-voltage power distribution cabinet test is completed, compare and analyze with actual data to improve the quality of high-voltage electrical tests. High-voltage power distribution cabinets are subject to external interference during tests, leading to errors in test data. In the process of analyzing test parameters, combine with median and percentile, analyze the numerical relationship with data dispersion, and obtain test data in combination with data distribution diagrams to improve data accuracy.

3. Adjustment Test Procedures for High-Voltage Power Distribution Cabinets in Power Systems

3.1 Carefully Check Design Drawings, Relevant Data, and Design Requirements

Before carrying out debugging operations on high-voltage power distribution cabinets, detailed review of design drawings is required to check whether the structural settings and component configuration of the high-voltage power distribution cabinets meet the standards. In previous work, component mismatches and shortages often occurred due to manufacturer errors, resulting in high-voltage power distribution cabinets failing to meet design requirements and affecting the exertion of their basic functions in power system operation. In addition, cases of distribution cabinets being inverted due to installation errors also occur from time to time, seriously affecting the normal operation of equipment. The above problems can be avoided through strict drawing review. During the review, focus on checking the model, capacity, voltage level, installation position, etc., of each component of the high-voltage power distribution cabinet, and promptly eliminate abnormalities to avoid affecting the normal operation of the distribution cabinet.

3.2 Transmission and Interlock Adjustment

High-voltage power distribution cabinets in power systems are divided into electrical parts, mechanical transmission, and mechanical interlock parts. The distribution of each part directly affects the operating performance of power equipment. Electrical installation technical specifications point out that the push-pull rods of handcart and withdrawable complete power distribution cabinets should move flexibly without obvious jamming. 

In addition to the advancement and retraction of the handcart, the interlock between the handcart's operating position and test position, the interlock with the grounding switch, and the interlock between the grounding switch and the cabinet door are common interlock problems of the operating mechanism. Slight improper mechanical transmission and interlock may cause mechanism jamming and collision, affecting the working quality of the entire mechanism. 

In modern power systems, high-voltage power distribution cabinets have a wide variety of types and models, with complex specifications and parameters. Mechanical transmission and interlock components produced by different manufacturers have obvious differences, increasing the difficulty of mechanism debugging. At this time, debugging personnel are required to carefully read the mechanism's factory instructions and carry out mechanism debugging in accordance with the requirements until all mechanical performances meet the requirements, with no jamming or collision problems, sensitive and reliable handcart movement, and accurate positions of electrical contacts. 

For example, the debugging requirements for isolating switches and grounding switches are that the cutting depth between the blade and the contact reaches more than 2/3 and meets the three-phase synchronization requirement; the handle opening and closing process is sensitive and smooth, and the interlock contacts are accurate; all bolts are firmly fastened, all pins are opened, and the functions of the mechanical transmission and interlock modules are fully exerted.

3.3 Safety Distance Inspection

With the rapid development of the power industry, a large number of innovative electrical technologies and equipment have been applied to power systems. In the past, oil-minimum circuit breakers and bulk oil circuit breakers have been replaced by advanced high-voltage switchgear such as vacuum circuit breakers. At present, it is rare to see large and bulky vertical high-voltage power distribution cabinets in power systems, and the popularization rate of handcart withdrawable power distribution cabinets is very high. 

Compared with traditional distribution cabinets, handcart withdrawable power distribution cabinets have limited volume, convenient operation, sealed cabinets, reasonable internal structure, and compact arrangement of components. However, the safety distance between phases and between phases and the cabinet is shortened, and blind spots are likely to occur during cabinet inspection. This requires relevant personnel to conduct detailed inspections before equipment commissioning to check whether the busbar configuration and connection in the cabinet, the lap joint between the busbar and each component, the arrangement of cable entry and exit, and the tightness of lap fixing bolts meet the requirements for safe operation.

 For example, check whether each internal lap bolt is equipped with a fastening washer; whether the safety distance between each line and component meets the standard, etc. In addition, the interior of the distribution cabinet needs to be cleaned to remove dust on the surface of insulators and other components, and debris at the bottom of the cabinet to avoid leaving any useless bolts or gaskets in the distribution cabinet.

3.4 Grounding Status Inspection

High-voltage power distribution cabinets operate under high-voltage conditions, and their grounding status directly affects the personal safety of relevant staff. Therefore, the grounding condition of the high-voltage power distribution cabinet body must be carefully checked before debugging. It is required that a certain distance be maintained between different cabinets, and the grounding busbar and the grounding main line in the power distribution room are reliably connected. Check whether the cabinet door of the high-voltage power distribution cabinet is connected by bare braided copper wire and the screws are tightly fastened to the standard. Check the status of the grounding knife switch to ensure reliable fixing of bolts. Analyze the grounding status of the secondary circuit to ensure reliable connection with the busbar. If poor grounding is found during the above inspection, it must be remedied in a timely manner.

4. Conclusion

In summary, the key points for debugging high-voltage power distribution cabinets in power systems are reflected in the control of grounding, voltage, and lead wires. In addition, design drawing review, component appearance inspection, grounding status inspection, safety distance inspection, and transmission and interlock debugging are all important contents of the high-voltage power distribution cabinet debugging procedures. Therefore, the debugging of high-voltage power distribution cabinets must be carried out in strict accordance with the requirements of the debugging procedures to ensure their high-quality operation.