Vietnam’s Circular No. 31/2019/TT-BCT: Guidance on restoration of transformer after fault

According to Clause 9 Article 1 of Circular No. 31/2019/TT-BCT of the Ministry of Industry and Trade of Vietnam amending Article 38 of Circular No. 28/2014/TT-BCT on cases of restoration of transformer after fault:

Firstly, in case a transformer is switched off for a protection action other than differential protection, gas protection, oil flow- or oil pressure-related protection, after the operating personnel conducts a check and reports the transformer’s physical appearance and does not detect any unusual signs, the dispatcher shall put the transformer back into operation if one of the following conditions:

- The dispatcher confirms that the protection circuit trips inadvertently;

- The operating personnel finds that the protection circuit trips inadvertently because it is damaged and the damage has been rectified. If the damage to the protection circuit fails to be rectified, the dispatcher shall permit the isolation of such protection circuit at the request of the operating unit and put the transformer back into operation provided that the remaining protection relays are capable of providing adequate protection against all types of faults and the prescribed fault clearing time is observed.

Secondly, in case a transformer is switched off for differential and gas (or oil flow or oil pressure-related) protection, the dispatcher shall put the transformer back into operation if the following conditions are met:

- The operating unit has conducted testing of parameters, analyzed gas and oil samples and take corrective actions against detected unusual signs;

- A written confirmation by the operating unit that the transformer is qualified for operation shall be provided for the dispatch level vested with controlling rights.

Thirdly, in case a transformer is switched off for differential protection or gas protection or oil flow or oil pressure-related protection, the dispatcher shall isolate the transformer and transfer it to the operating unit for testing and checking of the primary protection circuit that has tripped. The dispatcher shall put the transformer back into operation if one of the following conditions is met:

- During the testing, it is found that the transformer’s primary protection circuit trips due to damage to the protection circuit and such damage has been rectified;

- During the testing, it is found that the transformer’s primary protection circuit trips due to damage to a device in the primary protection zone (but it is not the transformer) and such damage has been rectified;

- No damage is found during the testing of the primary protection circuit and devices in the primary protection zone and the operating unit has met the conditions set out in clause 2 of this Article.

Fourthly, in case a transformer is shut down resulting in disconnection of electricity supply to important electricity consumers, the dispatcher shall put the transformer back into operation if the following conditions are met:

- The dispatcher conducts a check, confirms and informs that such transformer is only switched off for one of its internal protection actions and no external signs showing that the transformer is damaged are found;

- The operating personnel informs that the transformer is put back into operation with the consent of the leader of the operating unit.

View other provisions at Circular No. 31/2019/TT-BCT of the Ministry of Industry and Trade of Vietnam, effective from January 03, 2020.

Thu Ba

>> CLICK HERE TO READ THIS ARTICLE IN VIETNAMESE