What causes national grid collapse and how it occurs - explained in layman terms

Let us take a look at what causes national electricity grid collapse and how it occurs.

What will happen before a grid collapses. I will try to explain in a layman way.

There are 26-grid connected power plants currently. These power plants generate the power that the entire country uses, and it's synchronised and distributed across the country by the TCN.

TCN are the ones that handle the distribution of power by sending it to Discos.

TCN is a government owned entity that majorly operates in three (3) different departments.

1. Transmission Service Provider (TSP)

2. System Operator (SO)

3. Market Operator (MO)

TSP are the ones in charge of maintaining the cables and towers that transmit the light.

MO are the ones that handle market processes, rules, enforcement, finances, etc.

SO are the ones in charge of maintaining and stabilising our national grid.

National grid is the interconnections of high transmission wires/cables across the country.

The national grid stabilisation and maintenance is done by two methods:

1. Grid frequency

2. Voltage

The most common item that causes the national grid collapsed is measured by grid frequency.

Let us look at how it works.

Grid frequency measures the demand and supply of electricity despatch to consumers from the Gencos.

Frequency meters are measured in hertz (Hz).

Based on the grid code, our normal frequency level is supposed to be 50Hz.

Example.

If the current power generation is 4000MWh and people are using all the 4000MWh, then supply is equal to demand, and frequency should be 50Hz.

This is a perfect condition that is highly unlikely.

If we are generating 4000MWh and People are using 3700Mwh, then obviously supply is higher than demand, and for that reason, the frequency will show you 51Hz.

If we are generating 4000MWh and people are trying to use 4200MWh, demand is higher than supply, and for that reason, the frequency will show 49Hz.

I know you will ask me how you can be generating 4000MWh and be trying to use 4200MWh

Take, for instance, your using I-pass-my-neighbour generator, and you're trying to connect 2HP A.C. with microwave on the generator, the generator will just automatically shut down. That's how it happens, too, on the national grid.

Nigerian national grid is set to operate on a designated frequency level

Upper limit = 51.25Hz

Lower limit = 48.75Hz

The job of an S.O. is to make sure that the frequency movement is in between these 2 levels.

Any significant deviation from these 2 levels, i.e., if it exceeds the threshold above or below it, such might trigger a national grid collapse.

A grid collapse is not like a collapse that something bad happens, no. The 26 grid connected generators will automatically shut down because of safety and security reasons.

In your houses, if you have a serious electrical fault, the circuit breaker will trip off to shut down the entire supply and protect everyone from potential injury or damages.

This is also how it works on a national level.

The demand for electricity is not static.

For example, let's say you have 10 ACs in your house and other appliances. In full capacity, your house is consuming 500Kwh, and average capacity can be 300Kwh or less.

Let's say in this hot weather, they only allocate 250Kwh to your house, and you're trying to use it in full capacity, if you switch on everything the demand will exceed the available supply and for that reason the light will automatically go off.

These are all examples of how a demand is trying to exceed supply and how the system will protect itself. On the flip side, when supply exceeds demand, the system will equally go off for safety reasons.

In Nigeria, supply does not always exceed demand unless there is an adverse event that occurs. I will explain.

In 2022, when TCN unions (NUEEE) decide to go on strike, they just off the light abruptly without notice nor following the normal process, this trigger imbalance between the demand and supply.

They off the electricity around Abuja axis and co areas without the S.O. necessarily transferring the load somewhere. This resulted in higher supply, less demand because the generators are working, but nobody to pick load. It means For E.g,

there is 4000MWh being generated from GenCos. You went ahead to shut down almost 500MWh without channelling that MWh somewhere else. It becomes a redundant, and the system does not accept redundancy. For that reason, the entire power plants go off to protect itself.

The frequency will be showing something more than 52Hz in some cases because supply is higher than demand.

This is why you will see that they will bring light now and take it off again. The demand is not static, and as its changing, the S.O. will also be making sure that the supply is reasonable enough to maintain frequency reading within the allowable limit.

TCN will ask a disco to take 200Mw, and within a short time, they will reduce that 200Mw to 190Mw depending on how generation and demand are behaving.

This is all done to protect the grid and maintain balance. If TCN asks Disco to reduce the MW, that's when you see discos taking light off, or maybe if there is a major repair. Also, if there is a repair and a disco can not offtake power, then either the disco rechannel it somewhere or the TCN will do it themselves.

What causes grid collapse is not a deflection of small MW in the generation pool. It has to be a major disruption that is SIGNIFICANT enough to create imbalance within short time, making it impossible for the S.O. to react immediately.

You have a generation pool of 4000MW, and a sudden problem occurs at the transmission line, which takes out almost 500MW off. This is significant enough to cause grid collapse. Even that 500MW, it has to be so fast that the S.O. cannot react at the immediate point. Disruption like 10MW, 20MW is not significant enough, and it's usually handled by the S.O. or even the disco.

Other ways to maintain the grid without collapsing is to have the full and complete use of Supervisory Control and Data Acquisition (SCADA). This will make it easy for the S.O. to react faster and save the grid from collapsing.

Spinning reserve is also another option But we do not have enough generation talkless of having a spinning reserve

Reserve means a situation where demand is increasing, and you're matching up the demand by increasing supply immediately.

After grid collapses, the S.O. will immediately order the restoration or start off of power plants again. They usually call it black start. They initiate the power plant and begin to give electricity to strategic discos gradually. It usually takes less than an hour depending on the situation at hand.

It's a normal process, just like when your circuit breaker trips off, then you fix it and on your light again. This is why the grid will collapse, and they will restart it before the news even go out. By the time its in the news, some people will be saying, but we have light.

Need to also mention that some power plants are not connected to the grid, and there is partial collapse and system-wide collapse. These can also be the reason why someone from a far away remote location can be claiming to have light when the grid collapses.

Let me stop here.

Maybe another time we can discuss the second cause of collapse, which is even rare, i.e. the voltage method.

I hope we learn something today.

Cheers.