A power system collapse occurs when there are system disturbances and the grid is unable to withstand the stress. This can lead to blackouts or abnormally low voltage in the system.
In the case of Nigeria, such disturbances can be caused by a lack of investment in the dilapidated power network, obsolete substation equipment, overloading of certain transmission and distribution corridors, poor operations and maintenance of the grid, lack of power system protection and control, load rejection, sudden loss of generation, plant overloads, frequency fluctuations, generator pole–slipping and loss of synchronism, faults etc.
A total system collapse means total blackout nationwide, while partial system collapse is a failure of a section of the grid. Let’s examine the impact of frequency fluctuations on system collapse in the Nigerian Electricity Supply Industry (NESI).
The Nigerian power system operates at a nominal frequency of 50Hz. This means that all systems are locked and synchronised to operate at an angular rotational speed of 50 cycles per second.
According to the grid code, the statutory frequency limits are within the range 49.75 – 50.25Hz with the allowance for operational limits within the range 48.75 – 51.25Hz during times of system stress and significant disturbances. However, based on the relative amount of system generation compared to system load, the power system can go “over” or “under” the preferred limits. To avoid damaging expensive items of power system plants at such times, manual interventions and or automatic systems are normally employed to shut down power system plants.
Over-frequency occurs when the total generation on grid is far in excess of the load or demand. The generators “over-speed” and can get damaged if not tripped out. This will typically occur due to load rejection, sudden loss of load, distribution and or transmission corridors. Under-frequency on the other hand occurs when the total load is by far in excess of on-grid generation capacity. This may occur due to a sudden loss of significant amount of generation.
During this year in review, and as of the time of writing this piece of work, we have had 14 total power system collapses which resulted in blackouts, disruption of activities, untold suffering and hardship for the citizens of this country. Micro, Small and Medium Scale businesses have been the most hit. Their profits plummeted daily and their competitiveness in the market place waned drastically. We are all victims as we grapple with noise pollution from “I better pass my neighbour” and other generators. We suffer the profound effect of choking deaths from generator fumes that killed entire families overnight. We struggle to contend with estimated bills that have to be paid for whether we consume electricity or not.
Frankly speaking, 2019 is not the worst when it comes to the power sector experience of total system collapses in the recent past. From the statistics I have kept, the worst year, in terms of number of times the system collapsed, is 2010 with 22 total system collapses and 20 minor or partial collapses. However, it is significant to highlight this because as years go by, we have to be able to monitor and confirm, with detailed empiricism, whether we are making progress in specific areas of power systems and the number of total system collapses year-on-year, among other measures, is a good start.
It is imperative therefore, to review the reasons behind the incessant power system blackouts we had in 2019 with a view to drawing lessons from the gory situation and offering solutions where possible.
The nation was “baptised” and welcomed into the new year with the loss of the power system during the very first week of the first month of the year. On Wednesday January 2nd, the loss of the Escravos-Lagos Pipeline System (ELPS) due to maintenance works on the line by the Nigerian Gas Company led to the loss of gas-fired power generators all over the country. The system went into under frequency as would occur whenever there is a significant difference between load and generation levels based on power system stability design criterion.
But why will the loss of a single item of network lead to a total system shut down in the 21st century? It boils down to lack of planning, merit in appointments and absence of project management. The entire network in the electricity value chain should have some form of flexibility in design and implementation. Thus, I will advise the N-1 security standard for the gas, transmission, and distribution networks. This in simple terms means that the loss of a piece of network in the value chain should never result in the loss of the power system. The systems should have interconnections and mesh networks, not radial. This requires significant experience in power system planning, project management and regulation. On the commercial side of the problem, there is the issue of gas pricing. The price of gas used in the tariffs for electricity generation is not commercially attractive enough for gas suppliers and operators to invest in gas pipelines or networks to convey gas to power plants dotted round the country. The government has to see to this and declare an emergency in gas-to-power initiatives and make sure they work.
Another total power system collapse occurred at the Benin transmission substation when extreme overvoltages occasioned by a sudden loss of distribution network demand and lightning shattered and destroyed the 75MX Reactor permanently left in-service at the substation. The Benin transmission substation is a confluence of 330kV lines. There are twelve (12) number long lines with nine (9) of them directly connected to different power
stations. All the power stations generate onto this busbar. For a lightly loaded and long transmission line, the Ferranti effect is a permanent feature of this section of the transmission network with system voltage rising to as high as 400kV permanently. Hence, the shunt inductive reactors in Benin were left permanently in service as against the norm. Shunt inductive reactors are used to prevent transient overvoltages on lightly loaded or unloaded but charged transmission lines. They are not to be permanently switched-on but are used during system restoration after an outage or during extreme load shedding. In the Benin case, they were permanently left in service in view of the sustained overvoltage at this substation. This is an operational error!
To avoid a repeat, investment in transmission and distribution network infrastructure based
on power system studies that will identify the reason(s) for the sustained overvoltage at this substation since the commissioning of Omotosho NIPP power station is required. In addition, there is a dire need for a review of the entire protection and earthing system nationwide to prevent similar incidents in other parts of the country and to avoid deaths by electrocution.
To reduce the spate of incessant total or partial system collapses in the Nigerian Electricity Supply Industry (NESI), there is a dire need for frequency control with generators operating on free governor mode (FGM) in accordance with the grid code and the use of spinning reserve in the operation and management of the Nigerian power system. The Nigerian grid requires up to 400MW (at 10 percent operating margin) of spinning reserve and the system operator claims it is yet to secure NERC’s approval of its request to procure 260MW of spinning reserve from the electricity market to date. Also, a functional Supervisory Control and Data Acquisition (SCADA) system can help prevent future grid collapses by making operators aware of faults in the system to the extent that corrective measures can be taken in a timely ordered manner. It must be mentioned however that Nigeria has failed in three different attempts in the past to have a functional SCADA. The last one was financed by the World Bank between 2006 and 2007 and Nigeria spent about $46 million. But the SCADA that was implemented had significant deficiencies and poor visibility as it could not cover more than 40 percent of the network.
For every case of system collapse, total or partial, the industry practise is to have a full investigation and a report by the system operator made publicly available to all stakeholders including the consumers.
In general, the existing power generation assets are not operating optimally. More than 50 percent of the generation capacity is not available, either for technical reasons/planned maintenance or due to unavailability of gas or other unplanned outages. Truth be told, the collapse of the national grid has occurred one too many times in Nigeria. In the year in review, the national grid collapsed four times in January, once each in February, April, June, and August, thrice in May, twice in November and during the National Union of Electricity Employees (NUEE) organized strike action that took place on 11th of December, making a total of 14 times the country has been thrown into complete darkness in 2019. All the collapses but one are largely due to under-investment in critical gas, transmission and distribution infrastructure. On the hand, the electricity employees’ strike is as a result of fallout of outstanding issues from the privatisation process that took place in 2013. The last strike was avoidable in so far the electricity workers gave a 21-day ultimatum to the Federal Government before members downs tools and caused devastation throughout the country.
…concluded.
Engineer Idowu Oyebanjo is the MD/CEO, Idfon Power Engineering Consultants (iPEC) Limited. He is a UK trained Power Systems Professional.
