Power System / Maintenance / Maintenance of a Potential Transformer and Capacitive Voltage Transformer

Maintenance of a Potential Transformer and Capacitive Voltage Transformer

The maintenance of a potential transformer is some what similar to the maintenance of a current transformer.

The potential transformer performs vital role in voltage measurement and distance protection scheme of the system.

The number of potential transformer in an electrical substation is limited not as much as current transformer.

The capacitive voltage transformer is a kind of potential transformer used for dual purposes. The CVT also performs the PLCC carrier protection of transmission lines. In other sense, it also performs as a coupling capacitor.

We need to act the followings for maintenance of a potential transformer or a capacitor voltage transformer.

  1. We need to check the oil leakage of electromagnetic unit tank of a PT very often.
  2. For oil filled PT or CVT, we need to watch the oil level of the equipment often. The oil level is visible on the oil level indicator glass fitted on the upper portion of the PT or CVT.
  3. We also need to measure the tan S value of PT, and CVTs to judge the condition of insulation oil of the PT. It the value of tan S comes more than recommended, we need take necessary step to rectify it or simply replace the equipment by a good one.
  4. Like other pieces of equipment like current transformer circuit breakers, PTs or VTs and CTVs need clean insulator to maintain its proper creep-age distance. We clean the insulator with clean, dry and fluffy free cloths.
  5. Visual checking of HF point in case of CVTs needs to be done in yearly basis.
  6. Thermovision scamming is also required if any high temperature found in any power connection of the body of the PTs, we need to take proper action.
  7. We also check the PT junction box checking the connections of all points including the earthing connections. If any loose connection found, we need to re-tight it immediately.
  8. We need to keep the box clean. If any point work deteriorates, we need to repoint the portion or entire box immediately.
  9. If gasket of the junction box cover becomes damaged, need to be replaced without waiting. Because it prevent the moisture entry inside the junction box.

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