The sudden loss of power supply from Gwagwalada and Katampe transmission substations during the evening rainfall on Saturday 25th April, 2020 has led to a debate between transmission company of Nigeria (TCN) and Abuja Electricity Distribution Company (AEDC), the distribution network operator in the franchise area of the power network. In its view, the management of TCN attributed the sudden loss of power supply to sudden drop in load by AEDC. “All AEDC 33kV feeders were out due to poor distribution network”, it says. In a widely circulated explanation, TCN contend that if nothing is done to quickly capitalize AEDC and indeed all the other distribution companies (DisCos), the power system will completely collapse.
In a swift reaction, AEDC management fired back asking rhetorically: “What does the power sector need – DisCo Capitalization or Expertise at TCN?”
The arguments quickly moved from blame game to a debate on whether capitalization of the DisCos is more urgent than the technical and operational efficiency of TCN in managing the transmission network as the system operator. The DisCo believes the problem occured largely because of lack of adequate protection settings and cordination of protection relays in adjacent zones of the network. To be sure, failures due to inadequate and improperly coordinated protection systems result in loss of power supply and makes power systems unreliable.
AEDC has challenged TCN to explain to the nation why it has consistently refused to allow the coordination of its protection relays with the DisCos. The cost required to do this is minimal compared to the call for capitalization and doing this will make the power system more reliable even at the levels of power generation that we have. To substantiate its claim, AEDC said “there are many instances where protection relays on TCN network do not trip during disturbances such as wire cut even when they rest on the ground thereby constituting serious danger to members of the public. On the 20th April, 2020, there was wire cut on feeder 5 from the Central Area transmission substation but the feeder did not trip. There is a litany of such cases like that”, it concludes.
Speaking in favour of capitalization, TCN reiterated that the least it could demand from AEDC was the recapitalization. “The incident of 25th April is a clear indication of how poorly AEDC’s 33kV network is constructed and the urgent need for AEDC to at least sanitize its lines”, it posited. On the shortcoming in the performance of protection systems, TCN maintained its protection systems operated correctly and as intended. “All the trippings of AEDC’s 33kV outgoing feeders at TCN were on fault, there wasn’t any spurious trippings at all”, it responded.
Clearly, the circuit breakers were tripped by TCN and not by AEDC. Furthermore, TCN alleged that AEDC’s injection substations are without functional protection schemes. To worsen the situation, it continues, “AEDC introduced 33kV autoreclosure circuit breakers which ideally is supposed to clear faults within its system”, but AEDC uses it for load management.
This blame game turn debate shows the extent of problem in the NESI.
The most important to deal with is the breach of safety of human lives caused by the manner of system operation of TCN if there are a litany of cases of live conductors on the ground as alleged.
When conductors snap and fall or hang, the protection should trip immediately. Where it does not, there is no protection. This has caused the deaths of many Nigerians in many parts of the country. University Students, passersby, pregnant women, men, women and staff of the utilities have died in several cases of hanging or fallen conductors. These deaths have to be probed and should not be swept under the carpet.
Another important matter requiring urgent attention is the fact that TCN, by its response, admits that it connects a DisCo to the power network knowing fully well that it is not having a functional protection scheme. In other words, TCN has breached its licence to operate a safe and reliable transmission network. A comprehensive audit of protection systems in the NESI is now mandatory before power network operators electrocute citizens at will.
The arguments and counter-arguments may continue but the end-consumers are the ones who suffer for the ineptitude and inefficiencies resulting from the shoddy privatization exercise that gave birth to the current impasse. This is a reminder that where meritocracy is not allowed, we pay more for ignoramus.
X-Raying TCN’s Position
AEDC admitted that its feeders tripped and apologised for the discomfort caused. However, TCN actually tripped them out.
The positions of TCN are only correct if the relays were set correctly. The only way to prove this is for a team of independent experts, not from TCN or AEDC, to investigate what the relays actually tripped on.
It is preposterous, to have the protection on the entire 33kV feeder circuit breakers tripped out at the same time on fault.
If TCN is happy, it should allow an unencumbered investigation of the protection settings at the time of trip. It should provide us now with the actual settings on each of the 33kV feeder circuit breakers at the time of trip, and the fault levels at which they tripped out. (This has to be provided within 24 hours for data integrity).
A poor protection settings on the outgoing 33kV feeders as installed by TCN will always make AEDC look bad. In the actual fact, since over 80% of the feeders are to directly connected (point) loads, it is more likely that the fault is from the lack of grading and inadequate protection settings from TCN. Think about it, AEDC protection is yet to be involved.
A comprehensive audit of protection scheme in the NESI is now urgently required.
This assertion that auto-reclose is supposed to be used to clear faults by TCN needs to be corrected. An autoreclose scheme is not to clear fault but to maintain system continuity after the occurrence of a transient fault. If TCN engineers do not know what an auto-reclose scheme is used for, they will prevent its use in the NESI. If anything, AEDC is more correct to install autoreclose schemes.
The protection relays which tripped are in the TCN substation. If the downstream 33kV protection of AEDC did not operate, the fault is due to the lack of grading and poor protection settings on the network. It is just that, playing the “big brother”, TCN has muzzled AEDC (and other DisCos) when it comes to the “BLACK ACTS” of protection.
If given the opportunity, I will provide an interface protection scheme that eliminates this problem in due course.
Back to the poser question: What does the power sector need- DisCo Capitalization or expertise of TCN?
We need both. We need technical and operational efficiency underpinned by massive capital investment in load and non-load related asset replacement schemes in the power system, the finance of which only the federal government can guarantee as the DisCos are struggling to balance their books.
Engineer Idowu Oyebanjo is a power system professional and writes from the UK.
