In a few years, more national grid networks will take up renewables for electrification - are current transmission networks ready for the increase in generated capacity across the supply chain?

Currently, the transmission capacity of most African countries is inadequate to handle the available generation. Besides, the investments required for such a capital-intensive project of adding transmission capacity are extremely limited to most African governments. 

Thus, Africa has the option of exploring the off-grid addition of renewables to its energy mix by introducing mini-grids to the renewable end. This way, Africa can benefit from renewable technology as it builds its capacity to merge them with time. 

Surely, this approach will have its challenges but are surmountable. It is, therefore, worth trying to bridge the energy gap as the drive to bridge the digital gap intensifies.

Oghosa, adding renewable energy sources does not increasing grid network capacity. Engineers, in specific instances, are forced to increase capacity of transmission to avoid damage to the grid from sudden spikes in renewable generation. I think the real question is, "Are electricity customers ready for the increased costs of adding unpredictable wind and solar as sources of their grid's electricity?".

This is the reason why transmission planning process from ISO/RTO is very important which evaluates from time to time to identify the opportunities and challenges from the grid perspective. Then together working with government, utility partners (both at transmission and distribution) come up with a roadmap that is in alignment with the initiatives that are agreed upon. Bottom line, there is no one party can solve this, it requires more collaborative effort from regulatory bodies (such as NERC and FERC in United States), ISO/RTO, individual utilities and government

I believe that planners and engineers at the nation's utilities and ISO's have a great understanding of the need for EHV transmission projects across North America.  

 The financing is available.  Routing and permitting, while a lengthy process, is possible especially when underground and DC are options.  Design and construction resources are eager to compete and add value for incumbents or developers.  

The bottom line.....is there an off-taker ( a customer) for the power?  

Several big transmission projects that will bring renewables to load languish while waiting for a customer.  TransWest, Soo Green, the Hydro Quebec efforts to build through NH or ME. If these projects had complete PPA's for long term power, the routing and permitting would be done and design/construction would be underway.

In my opinion, when we need the transmission grid, we will build it.  There is no need to "Build it, and "see if they come"

All new generation whether renewable or conventional (gas, oil, etc) gets evaluated by the relevant RTO for their impact on the grid. If it is found that the new capacity causes loading issues locally or in some cases on distant facilities, they are charged an upgrade cost so that the grid expands along with the new capacity.

While some people believe this is a band-aid approach, however, given that more than half the projects that initially enter the queue drop out at some point and that it usually takes several years to build new transmission, there is little choice.

Fortunately a number of progressive utilities are increasing the capacity of their existing transmission lines by reconductoring with high-capacity, energy-efficient conductors like ACCC Conductor. While CTC Global can offer more than 1,000 project examples showing how well this works, please take a look at a T&D World article written by Mustafa Ali at Southern California Edison. A single reconductoring project virtually doubled line capacity and reconducting saved ratepayer $85 million USD and months of time. Article link: https://www.tdworld.com/overhead-transmission/article/21162860/reconductoring-vs-rebuilding-sce-experience