How inefficient grid management is killing power generating plants

The power sector is made up of three mutually exclusive, but necessary parts – generation, transmission, and distribution. Nigerians are all very much conversant with the operations of the electric generator or generating set (I better pass my neighbour or other bigger ones) which is made up of three parts – the generator itself (machine), an electrical cable or wire (transmission) that connects the generator to a control panel or fuse box through which the generated power is distributed to equipment (distribution).

All electrical appliances have set conditions under which they function at optimal levels. Any fluctuations in these conditions can cause the appliances to run at a lower efficiency. Power generators,like the Hydros and thermals used in Nigeria, are no exception to this. Thermal power plants, like the gas turbines (GTs) are designed to operate optimally and efficiently at base load. Operations of these gas turbines at operating points, far away from their baseloads implies a reduction in efficiency or in other words an increase in consumption of gas by as much as 15-20%,a cost not recognized by NBET nor captured in the MYTO.

This reduction in operating efficiency is in addition to the huge fatigue damage leading to higher O&M cost meted out on turbines due to ramping up and down over wide temperature swings. It is common knowledge that GenCo power stations have been used by TCN, via its subsidiary SO/NCC to stabilise the national grid with no compensations.

Generally, the damaging effects includes: thermal stress on Steam Turbine Blades, creep of compressor and turbine blades, Cracks on exhaust sleeves, Irregular heating and cooling cycles of hot gas path components, Cracks in ceramic tiles of the combustion chamber, Defective gas control valves due to wear and tear etc.

It is a no brainer that the grid cannot conveniently take over 4500MW without rejecting load. Generation above 5,000 MW may either be lost or rejected either by DisCos or transmission service provider (TSP) due to their inabilities largely caused by infrastructural challenges (Line cuts, Transformer faults and unavailability etc.) causing grid frequency to be very high.

Furthermore, Power Generation Companies are increasingly facing lower capacity utilization (dispatch)being forced to operate their dispatched Turbines/machines far from the baseload settings  sometimes even lower than 50% of rated capacity. On the plant level, less than 53% of average available power capacity is dispatched to the grid. For the month of April, 2018 for instance, on a daily basis, GENCOS had an average available capacity of 7485 MW but TCN could only transmit an average of 3985MW which is about 53% of the available capacity. This data as published by TCN (SO/NCC) is presented in the table below.

It is inexplicable that a country of over 180 million, is unable to utilise the GenCos available capacity of 7500MW, what then is the incentive for further capacity recovery and expansion?

Despite GenCos efforts to increase their available capacity effectively nominating same on a daily basis, the SO has the “grid right” to instruct any GenCo to reduce or cut down on its nominated capacity. It should also be noted that for a GenCo to nominate any capacity, it means effective commitments has been made as per gas and other equivalent overhead costs. This is a legitimate cost that must be recovered!

Compelling a generator to ramp up and ramp down at unscheduled time affects it equivalent operating hours (EOH) and also stresses the internals of the machine thereby reducing the plants lifespan as well as attracts an associated costs, incurred in making such capacity available. Generating plants can no longer sustain these costs alone given the level of remittance in the market, which barely covers the operating cost.

The only sane thing to do and save the sector from collapsing is for GenCos to shut down until when the networks (transmission and distribution) are efficient enough to take power and fully pay for both outstanding and current liabilities to GenCos. Section 12.6.6 of the Grid code allows the Generator to disconnect the Generating Unit for reasons of safety of personnel, Apparatus, and/or Plant.