Electricity, like water and oil, has its own way of measuring. Just like water or oil that are measured in litres and gallons, electricity also has its own measuring terms. Electricity is measured in units of power called watts. Electricity like weight is measured in kilowatt (KW), megawatt (MW) and gigawatt (GW).
Power is the rate at which energy is generated or consumed and hence is measured in units (e.g. watts) that represent energy per unit time. These different terms are used to convey different aspects of the performance of the National grid and quality of services delivered to electricity consumers. These acronyms which are often too technical to interpret are always confusing to those who are not too conversant with these terms used in the sector.
Generation Capability in millions of Watts or Mega Watts or MW (or in billions of Watts or Giga Watts or GW) refers to the ability of all the power stations that are actually connected to TCN’s transmission network and are ready and able to run and generate electricity that can be evacuated into the national grid. It does not include generating units that are out for repairs, maintenance or otherwise unable to run.
This is similar to stating that a particular building has a working 100 kW (kilo Watt or thousand Watt) generator, whether it is running at full capacity or not, or even switched on at any given moment. As long as it is in working order and ready to run it can be reported that 100kW of power is available to power that building.
The Generation Capability of the 28 power stations and 78 generating units connected to Transmission Company of Nigeria’s (TCN) transmission network as at October 31, 2017 stood at 7,343MW. This is up from a figure of 6,992MW on May 29, 2015.
Installed Capacity, also in MW, refers to the capacity of all the generating units that were at any time connected to the national grid, including units that are out for repairs or maintenance on minor or major faults. The installed capacity of Nigeria’s electricity system is currently 13,281MW, but many of the generating units that make up this figure cannot generate power until the current owners undertake major overhauls, that may not be economical.
The Transmission Capacity of the TCN’s transmission system is reported in million Volt Amps or MVA, or also in MW, which is derivable from the MVA rating. Transmission Capacity refers to the maximum power the national grid can deliver from power stations to the points were distribution companies receive the power for delivery to their consumers when all the transmission lines and substations are maximally loaded.
It is established by simulating the operation of the grid with different power stations generating at full capacity and assuming all the energy can be taken delivery of by the distribution companies. If you replaced a 5kW generator for a building with a 100kW generator but did not change the 5kW rated wiring that connects the generator to the building, you will not be able to draw more than 5kW from your new 100kW generator without burning the undersized wire connecting the generator to the building.
TCN’s current Transmission Capacity is 6,700MW. This means that 90 per cent of all the current generation capability of 7,343MW can be delivered to the distribution companies. However, there are specific power stations that cannot generate at their maximum Generation Capability without overloading particular components of the national grid, especially Ibom Power 190MW and Olorunsogo NIPP 676MW power stations.
Peak Generation, also in MW, is the highest level of generation recorded in a given period, such as a day. Peak Generation cannot be higher than Generation Capability. Peak Generation was 4,943.9 MW on October 31, 2017. The highest Peak Generation ever recorded on the national grid is 5,074 MW on February 2nd, 2016.
The total amount of Energy delivered over a given period, such as a day, is usually reported as the Average Generation times the number of hours in the period being reported, i.e. in MWh or GWh which is 1,000 MWh. Energy is what consumers pay for at their current tariff in Naira/kWh. 1,000 kWh is the same as 1 MWh.
Average Generation is reported in MWh/h in order not to confuse it with generation in MW. On October 31st 2017, the Average Generation was 4,038 MWh/h. Total generation was 96,907 MWh. When Average Generation is reported in MW instead of MWh/h it can create confusion. The figure of 4,038 MWh/h for Average Generation and 4,944 MW for Peak Generation are not the same for the same day, October 31, 2017, because they are reporting different quantities.
Energy and Average Generation are the best indicators of the amount of power made available to consumers connected to the national grid, because actual generation must equal power delivery to consumers since there is no storage for power anywhere on the national grid.
The primary driver of Average Generation at the moment is the ability of the distribution companies to off-take all the power made available by TCN at their trading points. While there are specific locations on the national grid where distribution companies want more power than TCN can make available; notably, Ikeja West, Kano and Port Harcourt Main; a rapid expansion of the 33kV infrastructure to off take power at the trading points and deliver it to consumers could increase Average Generation up to a ceiling imposed by the lower of Generation Capability of 7,343MW and TCN’s Transmission Capacity of 6,700MW.
Frequency of the grid is an important indicator of the stability of the grid. The nominal frequency on the Nigerian national grid is 50Hz. When generation suddenly exceeds load, the frequency increases. When load suddenly exceeds generation, the frequency decreases. If generation and load are not brought into alignment by TCN, the operators of the national grid, a grid collapse may occur which is when the components of the grid automatically shut themselves down to prevent damage to equipment and property. In recent months, TCN has improved its ability to enforce regulations that keep generation and load aligned in order to check incidents of grid collapse.
Etore Thomas (Mrs.)
Ag. Director, Press