Transformer substations in a system with distribution installations form the necessary nodes for voltage regulation in electric power delivery networks. This is a multicomponent infrastructure, which determines the stability of the supply of industrial, public and private buildings, as well as communications and equipment for various purposes. Maintaining the proper functioning of the network allows timely maintenance of the transformer substation and related working components. These activities are regulated by technical documentation and design recommendations developed for the operation of a particular facility.
Basic Maintenance Requirements
Documents for the operation of distribution electrical installations include the following provisions regarding the maintenance of repair and maintenance of transformer substations:
- Measures aimed at maintaining the working condition of the equipment should focus on protecting the object from premature wear. The same applies to the components and auxiliary parts of the substation.
- Repair operations should be aimed at restoring the primary operational performance of the equipment. These goals are achieved not only by technical means, but also by setting up and calibrating the equipment.
- Maintenance for transformer substations with a voltage of 10 / 0.4 kV should also include monitoring of building structures. In particular, the state of load-bearing platforms, walling and foundation sites is assessed.
- For the production of work, specialized brigades are allocated that have the appropriate qualifications and are provided with the necessary vehicles, installation tools, rigging tools, communication devices, protective devices, etc.
- If possible, work is combined with a routine inspection or repair of adjacent power lines.
Service schedule
There are regulatory requirements regarding maintenance intervals, but they can be adjusted depending on the current situation and the condition of the equipment. Possible adjustments to the schedule of maintenance activities are made by the chief engineer at the facility. As for the basic requirements for the frequency of maintenance of transformer substations, they set the following intervals:
- Regular scheduled inspections - once a year.
- Extraordinary inspection after a natural disaster - immediately after repair or the next day.
- Extraordinary inspection after the failure of the critical component - immediately after fixing the device or the next day.
- Seasonal inspection - before and after the heating season.
- Grounding check - every time during a scheduled check of the integrity of the substation elements.
- Measurement of network operating parameters - twice a year.
- Overhaul - once every 6 years.
- Checking the condition of the insulation winding - once every 3 years.
- Comprehensive screening of protective equipment - once every 3 years.
- Separate work arrangements (cleaning, tightening, lubricating, etc.) - as needed.
Service Event Admission Groups
In accordance with the rules of operation of electrical installations, five qualification groups according to the degree of electrical safety are allocated. Upon assuming office, service personnel are assigned a status according to their training and professional skills. Sole inspection of substations can be carried out by employees with an access group of at least 3. This qualification is available only to electrical personnel. In addition to inspection, employees in this category can connect and disconnect equipment from the network with a voltage of about 1000 V.
As for powerful installations working with substations on lines with a voltage of more than 1000 V, they can be serviced by employees of the administrative and technical personnel of the 4 access control groups for electrical safety, but only as part of a team. Workers are allowed to sole inspection of such substations only on the basis of a written order from the management.
Terms and conditions of work
Maintenance is carried out on the basis of an order for access-tolerance in accordance with the assigned list of operations within the framework of the current operational process. Before performing several work events at one facility, the organizers of the orders must first coordinate the actions of the employees. When servicing a transformer substation in a network with a voltage of up to 1000 V, the following conditions are required:
- The working area is enclosed, and live circuits are isolated as far as possible.
- Electricians perform technical operations on an insulating platform, in galoshes made of a dielectric material or on a rubber coating.
- Use the tool without insulation only with dielectric gloves.
- Work in clothes with rolled up or short sleeves is not allowed.
- When performing work, the provisions are excluded in which live parts are located behind the fitter.
Inspection of a transformer substation
Visual inspection involves checking the condition of the tires on the high-voltage bushings near the arresters and porcelain insulators. The master must determine the absence or presence of chips, cracks and dirt on the fuses of the transformer substation. Requirements for inspecting operating installations without shutting down also require evaluating the condition of thermometers, membrane elements on pipes, the position of automatic valves and indicator silica gel. The oil level is also checked and, if possible, with the help of measuring equipment, its flow rate is estimated.
Operational Maintenance Features
Based on the results of the initial visual inspection of the transformer substation, a decision can be made on the operational (unscheduled) maintenance of the equipment. Such work is permitted on-site brigades with the appropriate admission. Sole service, in particular, can be performed by employees with the 4th group of access for electrical safety, and as part of the brigade - with the 3rd group.
As part of an on-line maintenance, tuning or switching of electrical installations is usually done. For example, if you need to transfer the unit to full voltage when connected to the network after repair. In this case, the maintenance of the transformer substation will consist in alternately connecting the equipment to the network - with a jerk-like voltage supply and the unit idling for several hours.
Substation decommissioning
After inspection, a decision may also be made to decommission the equipment. Such decisions are made due to the physical obsolescence or wear and tear of a number of critical functional elements of the transformer system. But working installations are often written off. For example, if maintenance and repair of transformer substations is impractical due to high financial costs with the possibility of using less demanding, but equally productive models. Before the withdrawal of the substation based on the results of the technical examination, the expert commission draws up the relevant act. Further, based on the manufacturer’s recommendations, the operating organization can dispose of the unit. Moreover, for capacitors impregnated with trichlorodiphenyl, there are special disposal requirements.
Commissioning a transformer substation
One of the most important measures for the maintenance of electrical installations is the commissioning of the operational process. This set of measures provides for the commissioning and is carried out after the successful completion of the tests. Specialists check the equipment for performance under maximum load in various modes. Also, after servicing the transformer substation, grounding and lightning protection are provided. Dischargers connected to earth are connected to the tested installation. Typically, a short circuit is made to the metal housing of the transformer or to adjacent parts of the structure that are connected to ground.
Conclusion
The organization of servicing events at electric grid operation facilities is distinguished by technological complexity and versatility. The scope of such work may include directly installation operations that require high qualifications from the performers, and the simplest tasks of a prophylactic nature. For example, the initial access groups for electrical safety do not require special training and allow employees to perform simple verification procedures. In most cases, several groups are combined for complex equipment inspections. At the same time, various maintenance measures can be carried out, the general purpose of which will be to detect transformer substation failures and their subsequent elimination.