What are the Tests and Maintenances to be Done on Soil Separators (Soil Knife)?

Ground disconnectors are critical switchgear equipment that ensures the safe operation of maintenance personnel by safely connecting a circuit section that has been confirmed to be de-energized to the ground. For this reason, the tests and maintenance that need to be done on soil separators are not only done to see if the equipment turns on and off; The main purpose is to verify that the grounding function actually works reliably. An earth blade that looks solid from the outside; It may pose a serious risk in the field due to loose connection, surface oxidation, mechanical hardening, faulty interlock or incorrect position information.

The first step in maintenance is always safety. Before working on the earth separator, the correct maneuver sequence must be applied, the relevant section must be safely deactivated with the breaker and separator, tension must be confirmed and it must be made suitable for operation according to the field procedure. Especially in MV cubicles, not only the main circuit, but also the motor drive, auxiliary supply and signal circuits, if any, should be taken into consideration. Forgetting the control energy while performing maintenance on the soil separator may cause undesirable movements.

Visual inspection is the basis of soil separator maintenance. At this stage, blade surfaces, fixed contacts, insulators, mechanical arms, joints, spring elements, connection bolts, earth busbar connection and body parts should be carefully examined. Findings such as dirt, corrosion, moisture, surface cracks, darkening, overheating traces, current transfer traces, paint deterioration and oxidation should not be neglected. Soil separators, especially those working outdoors or in dirty industrial environments, may wear out faster due to environmental effects.

The cleaning process should be done in a controlled manner, not haphazardly. Earth separator blades, fixed contact areas, insulator surfaces and mechanical movement paths must be cleaned with an appropriate method. The accumulated dirt and oxide layer can reduce the contact quality, make mechanical movement difficult and weaken the safe grounding function in the long term. During cleaning, hard abrasives that will damage the surface should not be used, and if necessary, a cleaning and lubrication method should be chosen in accordance with the manufacturer's recommendations.

The condition of the contact surfaces in soil separators is very important. Because the task of this equipment is not only to move, but also to create a low impedance and reliable grounding path in the closed position. If there is dulling, pitting, oxidation, loss of pressure or unbalanced seating on the contact surfaces, this may lead to both overheating and inadequate grounding behavior. For this reason, contact surfaces should be carefully examined during maintenance, cleaned if necessary and lubricated at appropriate points according to the manufacturer's recommendations.

The tightness of electrical connections and mechanical fastening points should also be verified. The connections, flexible conductors, connection jumpers, terminal bolts and mounting points between the earth separator and the main earth busbar must be at the correct torque. A loose or oxidized connection may reduce the expected grounding performance in the event of an impact or fault. Especially in old facilities, connection loosening is more common due to repetitive mechanical maneuvers and thermal expansion.

Mechanical movement testing is an essential part of maintenance. It should be checked whether the earth separator reaches the final position clearly and without getting stuck during opening and closing. In types with spring or snap closing mechanism, sudden closing behavior, end position pressure and mechanical backlash should also be observed. A ground blade that does not fully reach the final position may appear grounded on the field but actually produce insufficient contact. Therefore, not only arm movement but also actual contact fit should be looked at.

Interlock systems are one of the most critical topics in soil separator maintenance. In many MV switchgears, the earth separator works in a mechanical or electrical interlocking relationship with the breaker and disconnector. The purpose of this arrangement is to prevent accidental grounding to an energized or inappropriately located section. These interlock structures should be tested one by one during maintenance; It must be verified whether key locks, padlock points, door interlock system, mechanical bolts and control permission logic are working correctly.

Position indicators and auxiliary contacts should also not be neglected. If the auxiliary contact gives incorrect information even though the ground separator is physically closed, SCADA, relay logics or field indicators may show incorrect status. Likewise, a piece of equipment that has not mechanically reached its limit position, even though it appears open, creates a false perception of security. Therefore, during maintenance, both the mechanical position indicator and the electrical feedback signals should be tested together.

Verifying ground continuity is one of the most meaningful electrical checks for this equipment. When the earth separator is in the closed position, the continuity and low resistance behavior between the main transmission path and the earth busbar should be evaluated. The goal here is to verify that the blade actually creates an effective dirt path. The low resistance approach is valuable for early detection of loose connections, poor contact or unexpected losses on the conductive path. If there is a significant difference between phases or similar cells, the equipment should be examined in detail.

If necessary, the insulation side should also be checked. While the earth separator is in the open position, it should be evaluated whether there is contamination, moisture or surface deterioration in the relevant insulation paths. These tests become more meaningful especially in cells that operate in a dirty environment, are out of commission for a long time, or have undergone mechanical revision. Insulation evaluation is not a decision-making test on its own, but a complementary control that should be interpreted together with visual control and mechanical findings.

In motorized or remote controlled earth separator applications, the drive mechanism and control circuit should be examined separately. It should be checked whether the motor carries it to the correct end position, whether the limit switch structures are working properly, whether the remote control commands are detected correctly and whether the position signals return reliably. In this type of systems, the fault often occurs in the control and drive chain, not in the main ground blade.

At the end of maintenance, on-off attempts must be repeated. The soil separator should not be tested alone but, if possible, within its own operating scenario. In other words, the interlock logic associated with the location of the breaker, disconnector, door lock and drawer equipment, if any, should be reviewed together. If it doesn't move without the correct sequence, this is a good sign; When the right conditions are met, maintenance can be considered successful if it reaches the clear final position without requiring excessive force.

In the final stage, all results must be recorded. Visual findings, cleaned areas, lubricated contact points, tightened connections, interlock attempts, auxiliary contact checks, continuity or low resistance results and detected nonconformities should be kept in maintenance records. Without trend monitoring, small problems may go unnoticed until they become bigger. In summary, the tests and maintenance that should be done on soil separators are; It consists of visual inspection, cleaning, contact surface and connection inspection, mechanical movement verification, interlock and position indicator tests, grounding continuity check, insulation evaluation where necessary and operating sequence confirmation. If you want to use soil separators, separators and MV/HV cell equipment together in your facility HV/MV testing, maintenance and repairfor system design LV/MV/HV project design and consultancy and business processes SA operation responsibility It is possible to progress in integration with services.