How to Maintain Installation of Medium Voltage Electrical Equipment

How to Maintain Installation of Medium Voltage Electrical Equipment
How is maintenance for effective electrical facilities, for example maintenance of Medium Voltage transformers, LVMDP, capacitor banks, secondary panels and other electrical equipment so that they can guarantee a continuous supply of electrical energy for industrial processes?

The key is implementing work instructions for maintaining electrical equipment as the implementation of the procedure for maintaining electrical equipment.

Work instructions for maintaining electrical equipment are step by step in carrying out maintenance of electrical equipment according to technical and safety standards carried out by the operator of the electrical section.

For more details about the work instructions (WI) for maintaining electrical equipment, you can see an example of work instructions below for maintaining electrical equipment from an industry that has implemented OHSAS 18001.

Example of Work Instructions (WI) Maintenance of Electrical Equipment
  1. Prepare maintenance equipment as needed including multi testers, screwdrivers, keys, vacuum cleaners, electric contact cleaners and PPE.
  2. Treatment time at least once a week.
  3. Electrical operators ensure the cleanliness of all electrical facilities using a vacuum cleaner.
  4. Measure the incoming 3-phase LVMDP voltage as well as the secondary panel using a multi tester and ensure that the voltage is appropriate, there is no voltage drop either due to the wiring voltage supply or abnormal medium voltage transformers.
  5. Check the tightness of the cable connections to prevent sparks from sparks due to lose cable connections. Tighten the bolt connections and cable terminals using a screwdriver but previously the electricity had been turned off. Give treatment to the connection using an electric contact cleaner to remove rust and dirt.
  6. Coordination with electricity supply company officers inspecting medium voltage main panels including ensuring the quality of insulation of medium voltage conductors so that corona (electricity emission) does not arise.
  7. Electric operators always wear PPE to avoid the risk of work accidents during maintenance of electrical facilities.
Medium Voltage Transformer Maintenance (Medium Voltage 20 kV)

Medium voltage transformer is a transformer that functions to change the 20 kV 3-phase voltage to 380 V. Medium voltage transformers must be protected from rainwater so that it is placed in a closed room equipped with air conditioning as air conditioning, lighting and floor drainage if needed.

The door to medium voltage transformer room is free from obstructions to entry or exit and is affixed with a "high voltage, only authorized personnel may enter" sticker. The door to medium voltage transformer room is always tightly closed to prevent animals from entering.

The main maintenance of medium voltage transformer is to test the breakdown voltage of the transformer oil (purification) every 4 years or depending on the usage load using a dielectric strength tester oil gauge, the higher the electricity usage load continuously every day, the shorter the time interval for purifying medium voltage transformer oil.

Medium voltage transformer oil purification aims to restore the breakdown voltage of medium voltage transformer oil above 60 kV / 2.5 mm according to IEC standards because the breakdown voltage of medium voltage transformer oil decreases over time electricity is used.

In addition to main maintenance, there is periodic maintenance of the medium voltage transformer every year when there is no electricity consumption.

What is the maintenance of this annual medium voltage transformer?

Examination of the outside of the transformer such as the condition of the transformer tank, including all bolts, nuts and welded parts, the condition of the cable connection terminals and grounding, silica gel breather at least 3/4 of the silicagel must still be blue, if it is lacking then the silica gel is replaced completely or reactivated.

Check the oil level and make sure it is still above the oil level indicator/gauge limit. Checking the nitrogen pressure refers to the standard between +2 Psi and +3 Psi.

Cleaning the terminal insulator using a dry-cleaning cloth. Attempt to use compressed air to blow away the dust and dry it again with the wind and cleaning the rusty parts.

In addition to periodic maintenance of transformers every year, there is daily maintenance of medium voltage transformers in the form of work instructions for daily maintenance of medium voltage transformers.

Example of Medium Voltage Transformer Daily Maintenance Work Instructions
  1. Check transformer oil temperature, especially when the transformer is operating at full load. If equipped with a special thermometer or winding thermometer, check the indicators, whether there are signs of heavy loads.
  2. Oil level level according to level.
  3. Check the silica gel breather if the transformer is equipped with a conservator. A change in the color of the silica gel indicates that the silica gel will soon be replaced or reactivated.
  4. Make sure there are no leaks, tighten all bolts and nuts and re-check the condition of the transformer equipment.
  5. Hermetically sealed type transformer with nitrogen (without conservator) does a pressure vacuum gauge check referring to standard pressure 2 Psi to 3 Psi
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