The interconnection of grids across countries and regions represents the future of the global power system. We see a trend of grids in major countries and regions expanding in scale, increasing in voltage levels, and broadening in scope.

Interconnected synchronous grids bring considerable benefits. First, ensuring the development and utilization of large-capacity units, hydropower, nuclear power, and renewable energy; improving energy efficiency and reducing operation costs; Second, reducing system reserve capacity, promoting complementarity of various power sources; Third, facilitating large-scale optimal allocation of energy resources; Fourth, contributing to enhancing the overall efficiency and safety reliability of the grid.

Interconnection is a blend of cooperation and competition. There can be no interconnection without cooperation, and no real competition without interconnection. When establishing a cross-border interconnected power system, government intervention is often needed, focusing on the usage of national resources, cross-country energy exchange, and long-term interests.

North American grid

Comprising two major synchronous grids — the Eastern grid and Western grid, the Texas grid, the Alaska grid, and the smaller Quebec grid in Canada.

The Eastern grid extends from central Canada eastward to the Atlantic coast, and it serves the central and eastern states of the United States along with five provinces of Canada. The highest voltage level of the Eastern grid is 750 kilovolts, with a total installed capacity exceeding 700 gigawatts, catering to about 300 million people. The load peaks in the US and Canada, occurring in summer and winter respectively, provide a counterbalance; the hydropower-centric power structure in Canada complements the thermal power-centric structure in the US. Over 100 North-South contact lines exist between the two countries, allowing a power exchange capacity of about 20 million kilowatts. In 2009, the cross-national electricity exchange reached 726 billion kilowatt-hours.

The Western grid spans from western Canada southward to the Baja California Peninsula in Mexico, and eastward across the Rocky Mountains to the Eastern Plains, covering an area of 1.8 million square miles. It provides electricity to 14 western United States, two provinces in Canada, and a part of a state in Mexico, serving a total of 71 million people.

Australian grid

Australia's grid is split into two significant sectors: the National Electricity Market (NEM) and the Western grid. The NEM grid, functional since 1998, is founded on five interconnected regional grids, stretching from Queensland in the north to Tasmania in the south, nearly spanning the entire Australian continent from the north to the south. It is recognized as one of the world's longest interconnected grids. The total length of high-voltage transmission lines reaches about 40,000 kilometers. The Western Grid, with its total length approximating 7,000 kilometers, stands separately due to the vast uninhabited distance between them.

However, plans for connecting the two are already under consideration.

European grid

It is primarily constituted by the European Continental grid, the Nordic Power grid, the Baltic Sea grid, the UK/Ireland grid, and the Russia/CIS Countries grid.

European Continental synchronous grid The European Continental grid is the largest transnational synchronous interconnected grid globally, with nearly 300 cross-border interconnected lines. It boasts a power exchange capacity that exceeds 100 gigawatts, providing the physical foundation for the European unified power market. Looking forward, the European synchronous grid might be connected with Turkey, Ukraine, Moldova, Albania, and further expanded to construct the Mediterranean grid. This will connect the grids of more than twenty countries in North Africa, the Middle East, and beyond to achieve complementary advantages.

Russia/CIS Countries grid (IPS/UPS) The IPS/UPS, composed of grids from selected CIS countries, operates on the same mode and unified centralized scheduling. It has a total installed capacity of about 300 gigawatts, producing 1.2 trillion kilowatt-hours of electricity annually. It serves a population of 280 million, spanning 8 time zones, and is known as the synchronous grid with the world's largest coverage area.

The formation of the IPS/UPS started in 1956, and by 1978, the system enveloped all Soviet countries except the Central Asian ones. From 1979 to 1993, the grids of countries now part of the European Continental Power Grid remained synchronous with the Russian grid. Central Asian nations, with the exception of Turkmenistan, integrated into the PS/UPS synchronized grid in 2001 and Uzbekistan and Tajikistan seceded in 2009.

The IPS/UPS grid is harmonized with the Baltic grid via a high-capacity (1,420 megawatts) high-voltage direct current back-to-back transmission system, it links to the Nordic grid in Finland. Russia and the EU are contemplating unifying the IPS/UPS grid with the ENTSO-E grid, potentially creating a single, vast synchronized grid spanning 13 time zones.

Other transnational grids in Europe The British National Grid holds connections with Northern France, Northern Ireland, the Isle of Man, and the Netherlands. The grids of Britain and Ireland have interconnections with the European mainland grid. The Nordic grid includes Finland, Sweden, Norway, and the Eastern Denmark grid.

Grid across ASEAN countries

In 2007, ASEAN member countries, Australia, China, India, Japan, South Korea, and New Zealand inked the Cebu Declaration on East Asian Energy Security, committing to investments in regional energy infrastructure, including the ASEAN Power Grid and the Trans-ASEAN Gas Pipeline, to ensure stable energy supplies. The ASEAN Power Grid aims to boost transnational power transactions among ASEAN countries, catering to the increasing electricity demand and enhancing the accessibility of energy services. To establish this interconnected network, 15 new power transmission projects are slated for implementation. Beginning with bilateral transnational interconnection, it will gradually evolve into a sub-regional interconnection, and ultimately, an interconnected system for the entire Southeast Asian power system. Four interconnected grid projects are currently under construction, and 11 are in the pipeline, with completion expected by 2015.

                                                                                                                                                                （Source: Energy Review）