Preventive Maintenance Technology for Electrical Endurance Test Equipment

1. Plan Background

On the basis of the overall preventive maintenance plan for the switchgear test laboratory of Xi’an Weisi Automation Engineering Co., Ltd., and in light of the laboratory’s operational needs, this technical implementation plan is proposed for the preventive maintenance of part of the electrical endurance test equipment. Electrical endurance and operating performance test equipment play an important role in the switchgear test laboratory. The electrical endurance of switchgear is typically long-term, frequent, and highly transient, with each test possibly involving thousands to millions of operations and lasting from several hours to several months. The test equipment must therefore work reliably for long periods under frequent switching at high voltage and large current to ensure that tests proceed normally. Once a test is interrupted due to equipment problems, it may cause a significant waste of investment and time. This imposes very high requirements on the reliability and durability of the equipment.

Because electrical endurance test equipment operates under harsh conditions and for long hours, its accident rate is relatively high within the test laboratory, and accidents that interrupt tests have considerable impact. It must therefore be a key focus of preventive maintenance work to improve equipment reliability and extend failure-free operating time, thereby increasing the overall utilization rate of the laboratory.

During the implementation of preventive maintenance for electrical endurance test equipment, special attention should be paid to improving the maintenance system: establishing complete work procedures, record forms, implementation specifications, data analysis methods, and continuous improvement plans. This will support the laboratory’s overall preventive maintenance program.

2. Maintenance Measures

Dividing the fault stages of electrical endurance test equipment is the basis for maintenance. According to the specific conditions of the laboratory’s equipment, when planning maintenance work we divide it into several types—route maintenance, proactive maintenance, non‑proactive repair, and spare parts replacement—and implement them by category to ultimately achieve comprehensive maintenance.

2.1 Route Maintenance

Route maintenance for electrical endurance test equipment refers to regular inspections of test equipment by patrol or maintenance personnel, who use their portable tools during inspections to address any maintenance issues found. For equipment in normal use, the inspection frequency is set at twice per week. For equipment not running during inspection, the focus should be on cleaning, fastening, and insulation resistance; for equipment in operation, attention should be paid to temperature rise, current, voltage, operating status, alarms, and similar items. Route maintenance personnel should be equipped with a standard inspection tool trolley containing the instruments and meters required for route inspections, as well as appropriate tools and consumables, so that minor repairs can be performed at any time during inspections and routine checks.

To ensure that all major equipment is inspected, a detailed patrol inspection management plan must be drawn up in advance. By combining forms with a software system, the inspection process and work practices are standardized. Inspectors follow the inspection route to check each unit and promptly record any problems or observations. Records are organized and archived via forms or the software system, and each inspection cycle concludes with the generation of a corresponding inspection record sheet.

To ensure efficiency and safety, route inspections are carried out by teams of two people: one responsible for inspection, the other for recording and safety monitoring. During route maintenance inspections, the LHSTT method should be thoroughly implemented to improve efficiency. The LHSTT method is introduced in the following table:

2.2 Proactive Testing (Preventive Testing)

Preventive testing is an effective maintenance method for electrical equipment prescribed in the power system. Professional personnel use specialized test instruments or tools to measure the performance and operating condition of equipment, analyze the test data to identify potential problems during operation, and detect and remedy them in time to ensure safe use. Professional preventive proactive testing of equipment provides a more scientific and reliable basis for equipment operation.

Proactive testing should be carried out regularly. The power system requires preventive testing of transformers and other electrical facilities once a year. Compared with transformers and other conventional distribution equipment, electrical endurance test equipment operates under much harsher conditions, subject to frequent switching and overload impacts. Therefore, it is recommended that proactive testing of test equipment be carried out twice a year.

Preventive tests involve high‑voltage test items and are inherently hazardous. The work procedures must be strictly followed and safety signs must be in place. During preventive testing, special care must be taken to disconnect the transformer’s outgoing circuits to prevent backfeeding of high voltage to the high‑voltage side and thereby avoid accidents. A reference proactive testing workflow is as follows.

Different test devices require different proactive test items. Preventive proactive tests for electrical endurance test equipment involve multiple categories and items, mainly including:

2.3 Non‑Proactive Repair (Accident Handling)

Non‑proactive repair is part of the preventive maintenance program for electrical endurance test equipment. It refers to repairs carried out after an accident has inevitably occurred and when no effective proactive measures are available. It includes fault investigation, redesign, and post‑incident repair. Fault investigation after an accident is still very meaningful. From the standpoint of preventing future faults, detailed fault investigation helps to avoid recurrence of the same type of accident and may reduce other hidden or multiple faults. If the cause of the accident lies in equipment defects, it may be necessary to redesign the test equipment and system, including hardware modifications and software changes. Only after the preparatory work is completed can post‑incident repairs to the equipment be carried out.

Due to the lack of historical fault and operating records for the test equipment, non‑proactive repair work constitutes the greatest risk during the implementation of this project and must be fully prepared and assessed in advance. Non‑proactive repair is also an important indicator of equipment reliability. All non‑proactive repair work carried out during the project must be coded and recorded in detail as a basis for subsequent reliability‑oriented maintenance.

A sample fault characteristics record sheet is as follows:

Random equipment failures can affect the laboratory’s normal operation. Therefore, before the project starts, contingency plans should be drawn up for the covered equipment to ensure that accidents can be dealt with promptly and quickly. Based on possible accident risks and their impact, different preventive and emergency measures should be adopted. For risks due to computer system or control system crashes, the relevant equipment should first be backed up after the project starts. For computer programs without source code, whole‑system backups may be used. Common electrical components should be supported by general, interchangeable spare parts for emergency use. A reference accident emergency response flow is shown below:

2.4 Spare Parts Replacement

Effective spare parts management can greatly improve maintenance efficiency in the laboratory. Normally, at the time of equipment delivery, manufacturers are required to provide necessary spare parts or a spare parts procurement list. However, in actual laboratory operations, this rarely receives sufficient attention from management, resulting in a lack of unified management and planning for spare parts.

In this project, spare parts replacement work focuses primarily on establishing a sound spare parts management system. As far as possible, unified, standard‑specification, or modular products should be used. This helps reduce spare parts inventory, increase repair response speed, and improve equipment utilization and efficiency.

3. Implementation of Maintenance and Servicing for Electrical Endurance Test Equipment

3.1 Scope of Work

This project focuses on the maintenance of five sets of electrical endurance test equipment in the switchgear laboratory constructed by Xi’an Weisi Automation Engineering Co., Ltd. While carrying out maintenance during this phase, we will also gradually improve maintenance and operation standards, work procedures, and process forms, and preliminarily establish a computer‑based maintenance information system, thereby laying the foundation for subsequent overall preventive maintenance of the laboratory. Electrical endurance test equipment is chosen as the project scope for two reasons: on the one hand, the number of such devices in the laboratory is relatively large and their operating time long, which is conducive to data collection and comparison; on the other hand, they experience the most frequent current surges and longest operating time, leading to the highest reliability requirements. Starting standardized maintenance as early as possible will help rapidly improve the reliability of electrical endurance test equipment and thus have an immediate positive effect on the sound operation of the laboratory.

The implementation cycle for the preventive maintenance of the five sets of electrical endurance test equipment is 24 weeks, i.e., one complete preventive test period. The scope of work includes route inspections, preventive testing, accident handling, and spare parts replacement. Given the high value of electrical endurance test equipment, accidents covered in this project are limited to local incidents caused by faults in electrical components or systems, including component damage, abnormal equipment function, and cable faults.

Damage to major equipment such as transformers, main circuit breakers, main contactors, test loads, and thyristors caused by short‑circuits or overloads, as well as full replacement of equipment, if they occur during project execution, will be addressed separately by the maintenance provider and the user through supplemental contracts based on the actual extent of equipment damage.

The scope of this project also includes preliminary refinement of the preventive maintenance system for test equipment and the initial deployment and implementation of a computer‑based information system.

3.2 Work Standards

3.2.1 Cleaning Standards

The following figure shows a schematic of a complete equipment cleaning process. Test equipment is electrical equipment, so during cleaning the power supply must be disconnected and an obvious isolation point must be ensured. For equipment with energy storage units, the stored energy must be fully released. Electrical equipment should be cleaned with dedicated solvent‑based cleaning agents; ordinary water‑based, conductive, or corrosive cleaners must not be used, nor should chlorine‑containing cleaners, trichloroethylene, or carbon tetrachloride‑based cleaners.

Cleaning begins with the use of a vacuum cleaner combined with compressed air nozzles to remove dust and debris from the top and interior of the test equipment, followed by cleaning of electrical components and beams. A brush is then used to clean internal corners and dead spots, while the vacuum cleaner is used simultaneously to maintain negative pressure in the work area and prevent secondary pollution. After dry cleaning, rags with electrical cleaning agents are used to clean electrical components and the internal and external surfaces of the test equipment over large areas and to carefully clean dead‑corner areas.

Finally, clean dry rags are used to perform the most thorough cleaning of all corners and the inside and outside of the test equipment.

Besides cleaning the equipment itself, the cleaning process is also a complete visual inspection during which potential hazards such as local overheating or insulation damage may be discovered. This has a positive effect on overall preventive maintenance. Operators are therefore required to strictly follow the operating procedures during cleaning, carefully fill in the relevant forms, and upload photos of equipment status.

3.2.2 Fastening Standards

Proper fastening reduces equipment failure rates, prevents accidents, and lowers losses. Vibration or temperature changes can cause bolts to loosen; loosening leads to more vibration, which further accelerates loosening. This is a serious hazard for key equipment primarily secured with bolts, such as busbars, load impedances, and cables. It may cause arcing and even short‑circuit faults. Our statistics on past test load failures show that nearly 60% were caused by bolt issues (most of the remainder were due to high current and long‑duration energization resulting from protection failure), including loose bolts, bolts not tightened, or incorrect use.

However, tighter is not always better, especially for switchgear. In addition to the pressure of the bolt itself, proper fastening must make use of the elasticity and pressure of the electrical materials. When the two are in balance, fastening is optimal. Over‑tightening may actually reduce the contact area of switching devices and make them more prone to loosening.

The following measures should be taken to ensure proper fastening. Bolts and screws must be tightened using torque tools, and the torque limits must strictly comply with fastening requirements. After tightening, a prominent, durable color marking should be drawn across the nut so that its position can be checked during inspections. Any movement of the marking indicates loosening and must be investigated. The correct size and type of bolts and the appropriate spring and flat washers must be selected, and the use of non‑compliant or non‑standard fasteners is strictly prohibited.

Before implementation, work standards for tightening forces at different fastening positions must be drawn up based on the actual on‑site equipment, and torque wrenches must be used to strictly enforce these standards during fastening.

3.2.3 Lubrication Standards

Lubrication mainly concerns mechanical fixtures and moving parts such as motors, linear motors, and cylinders in the test equipment. Improper lubrication may cause equipment failures and major losses, and incorrect lubrication may lead to catastrophic accidents. Once a lubrication route is established, a mistake in the lubricant can affect all associated components. In practice, there is a common tendency to emphasize repair over lubrication, assuming that lubrication will not cause serious problems. With the advent of maintenance‑free cylinders and similar products, maintenance and technical staff have become even less focused on lubrication and often lack understanding of specific lubrication requirements for equipment.

In the overall preventive maintenance plan, every lubrication point on the test equipment must be clearly identified, including the required quality indicators or grades of lubricants, quantities, lubrication intervals, oil change intervals, and different requirements for winter and summer oils. Maintenance‑free components must also be clearly labeled to avoid negative impact from unnecessary lubrication.

3.2.4 Testing Standards

Inspection and evaluation of test equipment is the most important part of the laboratory’s overall preventive maintenance program. Its importance lies in the fundamental difference between preventive maintenance and routine maintenance: the former is performed beforehand, the latter afterward. Preventive maintenance aims to minimize potential faults before they occur through various maintenance measures, and these preventive actions largely rely on observation and testing.

In daily inspections, staff often simplify patrol work to the point that problems that should have been found are missed, existing abnormalities are not taken seriously, and intrinsic safety of the equipment is not ensured. Therefore, when implementing a patrol inspection system, inspectors must receive effective guidance and stringent requirements both in mindset and in practice to properly fulfill the critical inspection tasks.

Conventional preventive electrical tests for test equipment include insulation resistance testing, leakage current testing, dielectric loss factor testing, withstand voltage testing, transformer oil testing, voltage testing, current testing, operating temperature testing, fault waveform recording, partial discharge testing, and others. All these tasks must be performed in strict accordance with national and industry standards and codes.

3.3 Schedule

The preventive maintenance work for the five electrical endurance test devices in this project will be implemented by the project team of Xi’an Weisi Automation Engineering Co., Ltd. (http://www.weisiauto.com). The implementation period is 24 weeks, i.e., one complete preventive test cycle. Equipment inspections will be conducted twice a week. Preventive tests will be carried out once per cycle, while other work such as spare parts replacement and accident handling will be performed as needed according to actual laboratory conditions. Xi’an Weisi Automation Engineering Co., Ltd. is a professional supplier of automated testing and production equipment, serving sectors such as power, energy, and automotive. It is committed to providing users with the most competitive products and services. Its main products include electrical endurance test equipment, mechanical endurance test equipment, and temperature‑rise test equipment.