What are the Tests and Maintenances That Should Be Done on Breakers?

Breakers are one of the most critical equipment that trips in case of fault in electrical systems. The relay detects the fault, but the part that physically separates the circuit is the breaker. For this reason, the tests and maintenance that need to be done on breakers are not only to see whether the equipment is working or not; It is done to verify whether it will actually open at the right time in the event of a short circuit. A breaker that has been left in the field without any operation for a long time may cause unexpected malfunctions due to mechanical seizure, coil weakness, auxiliary contact failure or increased contact resistance if it is not maintained.

The first step in cutter maintenance is safety. The equipment must be completely de-energized, if the spring is installed, it must be discharged, the control circuit must be secured and the absence of voltage must be verified with suitable devices before starting maintenance. Visual inspection is then performed. The body, insulators, resin parts, interior partitions, primary contact surfaces, terminal connections, cable ends, secondary plugs, mechanical indicators and breaker position mechanism should be carefully reviewed. Symptoms such as burn marks, darkening, looseness, cracks, dust accumulation and overheating marks are the first signs that determine the direction of maintenance.

Cleaning is an essential part of cutter maintenance. Dust, dirt, metal particles and surface residues accumulated inside the cell can negatively affect both insulation and mechanical movement over time. However, cleaning should not be done haphazardly; Methods that will leave moisture and chemicals that may damage the equipment surface should be avoided. Especially after cleaning the primary contact areas and rail systems, light lubrication should be applied at points in accordance with the manufacturer's recommendations and excess grease should not be left. Otherwise, the lubricated surfaces may collect dust and become a new source of problems.

On the mechanical maintenance side, the opening-closing mechanism should be considered as a separate topic. The spring cocking system, lockings, latches, friction surfaces, pulleys, rails and moving links should be reviewed. It should be checked whether the breaker responds properly to the on and off commands and whether there is any abnormal noise, delay or lag in manual and electrical operation. The business meter is also important here. Because many manufacturers recommend detailed inspection and relubrication after a certain number of maneuvers. Mechanical life monitoring should not be neglected in frequently operating cells.

Opening coil, closing coil and spring winding motor are among the most critical auxiliary elements of breaker maintenance. The coils must produce sufficient force when receiving a command, the motor must charge the spring mechanism correctly, and the supply voltage must operate within the lower and upper limits. For this reason, during maintenance, it is not only checked whether the coil is energized or not; opening and closing chain, control voltage, coil current and operating stability are evaluated together. The minimum operating voltage test gives important results, especially in scenarios where the station battery is weak.

One of the most valuable tests to be performed on breakers is the timing test. Opening time, closing time, synchronism between poles, contact bounce and, when necessary, movement curves are evaluated with this test. The cutter may appear normal from the outside; However, timing testing may indicate early stiffness, spring weakness, damping problem or pole mismatch in the mechanical system. Especially in medium voltage vacuum breakers, the on-off times and the close behavior of the three phases are very important for protection reliability.

Main circuit contact resistance measurement is also an indispensable part of the maintenance program. This measurement indicates the health of the main contact surfaces, the quality of the connection points and whether there is any unwanted increase in resistance in the transmission path. This check, known as the micro-ohm or contact resistance test, is very effective in identifying problems such as loose primary contacts, contamination, wear or contact surface degradation. A significant difference between phases or an increase incompatible with previous records indicates that the breaker should be examined in detail.

Insulation tests are also necessary to understand not only the on-off operation of the breaker, but also its dielectric health. Measurements made in primary-soil, phase-phase and other isolation paths deemed necessary; It provides important information about contamination, moisture effect, surface deterioration or insulation weakening. Insulation checks become even more important, especially after internal cell maintenance, disassembly and assembly operations, and in equipment that is disabled for a long time. The insulation value becomes more meaningful when interpreted together with past measurements rather than alone.

Auxiliary contacts, interlock structures and position signals must also be tested. Because in many areas, the problem does not occur in the main contacts, but in mechanical locks that prevent opening permission, auxiliary contacts that give incorrect status information, or secondary plug non-contact. If there are situations such as test location, service location, and reserved location, they should all be verified in turn. Cell doors, ground separator, racking mechanism and electrical interlocks are also natural parts of the maintenance chain.

On the primary circuit side, busbar connections, primary fixed contacts, primary tulip or finger contact structures in withdrawable breakers and connection torques should be checked. Slight dulling on the surface does not always mean a problem; However, findings such as significant darkening, traced contact, overheating color or weakness of spring force are serious warnings. Cleaning and lubrication of primary contact surfaces, especially in breakers that are installed and removed from the switchgear, directly affects circuit resistance and reliable operation.

The maintenance approach also varies depending on the cutter type. Most of the time the main focus in vacuum cutters is; The aim is to evaluate the mechanism, contact resistance, on-off timing and, if necessary, the condition of the vacuum cutting cell by indirect tests. In SF6 breakers, in addition to these, gas pressure, gas density, leakage control and related alarm-lock logics also become part of the maintenance. In other words, the same checklist should not be used for every breaker; A maintenance scenario appropriate to the technology of the equipment should be selected.

Function verification after major maintenance, overhaul or cell renewal is of particular importance. Electrical on-off trials, auxiliary contact feedback, relay command chain, remote control scenario and, if necessary, primary injection or holistic circuit verification should be performed in the test position of the breaker. Because most of the time, the error that occurs after maintenance is not seen in the equipment itself, but in the reconnected control cables, secondary plugs or interlock settings.

In the final stage, all results must be recorded. Opening and closing times, pole differences, contact resistance values, insulation results, coil tests, minimum voltage behavior, lubrication and replaced parts should be archived regularly. Thus, not only the current situation but also the trend analysis can be performed during the next maintenance. In summary, the tests and maintenance that must be done on the breakers are; It consists of visual inspection, cleaning, mechanism control, coil and motor tests, timing analysis, contact resistance measurement, insulation checks, interlock verification and special inspections according to type. If you want to use breakers, relays and switchgear equipment together in your MV/HV facility HV/MV testing, maintenance and repair, on the project side LV/MV/HV project design and consultancy and business processes SA operation responsibility It is possible to progress in integration with services.