What are the Tests and Maintenances That Should Be Done in Compensations?

Compensation systems are critical systems that improve the power factor by regulating the reactive power balance of the facility and help the electrical infrastructure operate more efficiently. For this reason, the tests and maintenance that need to be done in compensations are not done only to answer the question of whether the panel is working. The main purpose is to verify the healthy operation of capacitor stages, switching elements, reactors, protection components and measurement chain. Because a small fault in the compensation system may turn into a reactive penalty, overheating, resonance, capacitor damage or internal panel fault over time.

The first step in maintenance is always safety. Before working on the compensation panel, the system must be safely disabled, the appropriate discharge time must be waited, and it must be verified that there is no residual voltage at the capacitor terminals. Because capacitors can hold voltage for a while after the power is cut off. For this reason, compensation panel maintenance should not be considered as an ordinary panel cover opening task, but should be handled with the logic of energy storing equipment.

Visual inspection is the basis of maintenance. Panel body, covers, ventilation grilles, filters, busbars, cable entries, fuse holders, capacitor bodies, contactors and reactors should be inspected visually. Symptoms such as swelling, leaks, cracks, darkening, burn marks, rust, corrosion, loosening, insulation material deterioration, and insect or dust accumulation should be taken seriously. Most compensation failures show their first symptoms during visual inspection.

Cleaning inside the panel is one of the critical steps in compensation maintenance. Accumulation of dust, moisture, metal particles and dirt can weaken the insulation security over time, disrupt the contactor action and cause temperature rise. Particularly in panels with fans and filters, filling the air filter increases the internal temperature and reduces the life of the capacitor. For this reason, filters, ventilation paths and the inside of the panel should be cleaned regularly, and the frequency of maintenance should be increased in dirty environments.

The physical condition of capacitors requires special attention. If there is swelling, deformation, leakage, signs of rupture disk, darkening around the terminal or sheath deterioration in the body, the relevant stage should be evaluated in detail. Since capacitors are the main element that produces reactive power, any loss of capacity or internal damage will directly impair the compensation performance. For this reason, not only the existence of capacitors but also whether they actually produce healthy capacity should be monitored.

Capacitance drop in capacitor stages may develop silently over time. Even if the system appears to be working from the outside, the actual kvar production of a particular stage may have decreased. Therefore, during maintenance, current measurements on a stage basis, capacity checks if necessary and balance observations between phases should be made. Significant imbalance in phase currents or inappropriate deviations from nominal may indicate a problem with the relevant capacitor group.

Fuses and switches are also main components of compensation maintenance. Power circuit fuses, step protection elements, auxiliary circuit fuses and panel input protections should be checked both visually and functionally. A blown fuse doesn't always mean just a fuse problem; Most of the time, it is caused by capacitor failure, contactor problem or harmonic strain. Therefore, replacing the faulty fuse is not the correct maintenance approach.

Contactors are one of the hardest working parts in compensation systems. Especially in automatic cascade systems, contactors can open and close many times during the day. Therefore, symptoms such as darkening of plastic parts, wear on contact surfaces, deterioration of auxiliary contacts, coil heating, mechanical sticking or abnormal noise should be monitored. In dirty environments, cleaning and, if necessary, replacement of contactors is an important part of the maintenance plan.

In compensation systems with reactors used in harmonic facilities, reactors should be evaluated separately. If there is overheating, varnish smell, color change, mechanical loosening, increased core noise or terminal darkening in the reactor body, this is a sign of serious stress. Systems with reactors are chosen to reduce the risk of resonance; However, if the reactor itself is faulty, the system cannot provide the expected protection. For this reason, not only the capacitor but also the reactor health must be constantly monitored in harmonic plants.

The power factor relay or compensation regulator is the brain of the system. The cosφ target, step sequence, delay settings, CT ratio and measurement accuracy of this device should be checked. If the relay is not adjusted correctly, even intact capacitor stages may be activated in the wrong order, and overcompensation or undercompensation may occur. Therefore, when investigating compensation failure, not only the power circuit but also the control logic must be examined.

Current transformer connections also directly affect compensation performance. If the CT ratio, direction, secondary connection and identification on the relay are not correct, the system will incorrectly detect the actual load condition. As a result, the stages do not activate as required or cause unnecessary switching. Therefore, during compensation maintenance, CT polarity, secondary connection security and compatibility with the relay must be separately verified.

Connection tightness is very important in compensation panels. Capacitor terminals, busbar connections, reactor ends, contactor outputs, cable lugs and grounding points should be checked for torque. Loose connections can lead to increased contact resistance and serious hot spots over time. This both shortens the life of the capacitor and may pose a risk of fire. Therefore, in-panel torque control is one of the main parts of maintenance.

Thermal camera inspection is a very efficient tool for compensation maintenance. When stages, fuses, contactor terminals, reactor ends, main busbar connections and panel entry points are thermally examined, unnoticeable looseness and overloads can be seen early. What is important here is to evaluate the differences between similar phases and similar stages as well as the absolute temperature.

Harmonic evaluation is especially important in facilities where drivers, UPS, rectifiers and non-linear loads are intense. Even if the compensation system is correct, the harmonic level may change over time and this may create unexpected stress on the capacitors. If there is an increase in THD, resonance approach, frequent fuse blowing or repeated faults in the stages, the harmonic harmony of the compensation system should be re-evaluated.

At the end of the maintenance, all results must be recorded. Which stage is problematic, which fuse has been changed, which connection is loose, reactor temperatures, thermal images, power factor relay settings and measured current values ​​should be archived regularly. Because compensation problems often do not arise suddenly; grows over time. If trend monitoring is done, capacity loss, excessive switching and heating problems can be detected before failure occurs. In summary, the tests and maintenance that need to be done in compensations are; It consists of visual inspection, panel cleaning, capacitor and contactor checks, fuse/switch verification, temperature and resonance awareness in systems with reactors, regulator and CT compatibility, connection torque, thermal inspection and harmonic evaluation. If the compensation system, harmonic effects, panel modernization and general energy quality will be evaluated together in your facility. LV/MV/HV project design and consultancy For general site suitability with HV/MV testing, maintenance and repair services can support the technical decision process.