AEDC, TCN Disputes Over Cause Of Burnt 45MVA Transformer At Apo Transmission Substation

By CLEMENT NWOJI, Abuja

Trouble is brewing between the Abuja Electricity Distribution Company (AEDC) and the Transmission Company of Nigeria (TCN) over the actual cause of the fire outbreak at the Transmission substation on Sunday.

While TCN had attributed the preliminary cause of the fire outbreak to AEDC fault saying, “the fire resulted from a direct fault from one of Abuja Disco’s 33kV feeders which had a history of incessant trippings, the 33kV lacked protection”, AEDC disputed the TCN allegation saying, “the basic engineering explanation is that whereas the 33kV line belongs to AEDC, the protection system at the source belongs to TCN.”

AEDC maintained that the TCN claim was not true just as it lacked any practical engineering sense.

In a statement by the AEDC General Manager Corporate Communications, Fadipe Oyebode, AEDC said: “we are saddened by the fact that instead of doing a root cause analysis of the immediate and remote causes of the fire outbreak, which consumed such an expensive and critical asset with the intention of preventing a reoccurrence, the TCN has resorted to a blame game with a defense that is not in tune with standard engineering practice.

“The basic engineering explanation is that whereas the 33kV line belongs to AEDC, the protection system at the source belongs to TCN. For a transformer to go up in flames, both the line and transformer protection apparatus belonging to TCN failed completely. It is the reason for the total failure of their protection architecture that should be investigated. The transformer that caught fire belongs to TCN. The protection apparatus for it are in the custody of and under the maintenance and ownership of TCN.

“In any power system all over the world, tripping from outgoing circuits of feeders as a result of fault is an expected component of operations hence elaborate protection system is provided for such transformers against faults from outgoing feeders. These basic protection schemes are expected to fence the transformer from internal and external faults that usually occurs while in circuit.”

According to AEDC, “for such a facility, there are four levels of protection. There is the protection at the feeder level (feeder H13 accused of causing the fire and property of AEDC). The 2nd level of protection is the protection that exists on the 33kV incomer (property of TCN) and this exists between the secondary side of the transformer and the busbar in the control room of TCN.

“The 3rd level of protection which is in-built in the transformer are of various types and they include winding temperature, oil temperature, pressure relief, buckholz, standby earth fault and restricted earth fault. This also within the control of TCN. The 4th level of protection for such a facility is the protection on the 132kV side of the 45MVA, 132/33kV side of the transformer. This is also under the control of TCN. Of the four levels of protections, three of them which are the most critical are owned, controlled and maintained by TCN.

“The essence of these multilayer protection scheme is to ensure that where one of the protection devices fail, the others will come to the rescue of the electrical apparatus. But in the logic of TCN, the failure of one is the failure of others whereas the activation and performance of the other three, which is under its control is not dependent on the one (feeder H13) alleged to have triggered the fire incident.”

While commending the Fire Service of the NNPC and FCT for saving AEDC customers from what would have been a calamity of immense proportion, AEDC reassured its continuous investments in its network in order to provide customers with world class service.

This is even as it recommended a complete overhaul of the protection architecture of the TCN facility at Apo and elsewhere within AEDC’s franchise area to forestall occurrence of similar disaster.

On its part, the TCN through a statement by its General Manager Public Affairs, Mrs Ndidi Mbah, on the ill fated day, Sunday 28 April, 2019, said: “TCN is equally investigating possibility of transformer protection failure on its 45MVA power transformer. The 33kV feeder H13 circuit breaker and current transformer exploded while the 33kV outgoing transformer snapped causing the fire.”