​This is the first visit and working session between EVNNPT and TEPCO leaders to find out, learn e🦹xperiences in management and operation of power transmission system.

Participation in the working session at TEPCO’s headquarters includes Mr. Toshiro Takebe – President and CEO of TEPCO Power Grid; Mr. Satoshi Niwa – President and CEO of TT Network Infrastructure Japan (TTNI), together with Directors of functional Departments of TEPCO, TEPCO Power Grid ꧒and TTNI.

Mr. Toshiro Takebe and Directors of functional Departments of TEPCO, TEPCO Power Grid introduced overview on organization structure, management and operation of power transmission system and results of TEPCO’s productio🥀n and business.

TEPCO was established in 1951, is the ꦇbiggest one among 10 power companies in Japan. It has 🔯functions to supply power to Kanto, Yamanashi province and Eastern area of Shizuoka province, including Tokyo.

TEPCO is a joint-stock company, of which 1.2% and 65.6% are occupied by Tokyo’s authorities and domestic cor🧔porations, while foreign investors accounted for 14%, domestic corporations accounted for 65.5%, the remaining are the holdings in free transaction in stock market, foreign investors accounted for 14%.

In 2016, TEPCO ha a total 42,855 employees;🅠 total asse🦂t of JPY 13,659.769 billion (equivalent to USD 121.3 billion), turnover of JPY 6,069.9 billion (equivalent to USD 53.9 billion), after tax revenue was JPY 140.783 billion (equivalent to USD 1.25 billion).

The power plants managed by TEPCO have a total capacity of 54,083 MW (exc🗹luding the 2 out-of-operation nuclear power plants), including:

♔- Hydropower: 07 plants of total ca✅pacity of 9,858 MW.

- Thermal power: 1⛦5 plants o꧒f total capacity of 44,225 MW.

- Nuclear power: 02 plants (Fukushima and Kashiwazaki) have a total capacity of 12,612 MW. However, the historical♍ earthquake in 2011 caused serious consequences in Fukushima nuclear power plant, these two plants have stopped working.

The power transmission system managed by TEPCO includes 21,208 km transmission line and 1,582 substations, with a total 269,570 MVA capacity, with fo♚llowing details:

In which, some transmission line sections have a 1,000kV design, but operate in 500 kV voltage. Besides, TEPCO manages a Shin-Shinano substati☂on – one of three Frequency converter substations in power transmission system in Japan (from 50Hz to 60Hz).

In 2016, TEPCO had a commercial power production of 247.075 billion kWh; ge🃏𓆏neral power loss of distribution and transmission grid was 4.8%.

From 2008 to 2016, all substations of TEPCO were changed into unmanned ones, except the substations of special importance such as the ones supplying power to airport.

TEPCO has 42 regiona🧜l maintenance divisions specialized in repair, maintenance, failures tackle, monitoring the operation of transmission lines and substations. The periodical maintenance is out-sourced. Each maintenance division includes ofꦫ 30 people, dividing into 2 sub-divisions: transmission line and substation. Maximum duration of accessing substation when failures occur will be 1 hour. The operation status, parameters must be checked periodically every month for every equipment.

EVNNPT mission and leaders, representatives of functional Departments of TEPCO, TEPCO Power Grid, 🃏TTNI

At the meeting, leaders of TEPCO Power Grid presented on TEPCO’s underground substation. It is an effective substation, intruding the 500kV, 275kV substations into big cities, especially Tokyo – the city of most dense population in the world, meeting the growing load demand, increasing the power supply reliability, reducing power loss. This solꦗution is suitable to the big cities where land acquisition and ground clearance for substation construction are very difficult. Cost of investment in underground substation is about 3 𝔍times of that of out-door tranditional substation. However, the building constructed over the underground substation can be used for business activities.

Proportion of underground substation compare𒊎d with total substations: in average 13%, but it is 39% and 86% ꦉin Tokyo and in 3 central districts of Tokyo, respectively.

After meeting in TEPCO headquarters, EVNNPT mission had a site visit to 500kV underground substation, this is an unmanned one named Sh🎶in-Toyosu. This is the first 500 kV underground substation in the world, which was put i🌠nto operation in November 2000. It is constructed in the centre of Tokyo city, playing a significant role in power supply for the city. It was changed into unmanned substation in 2016 and remote controlled by Shin-Keiyo centre which is 40 km from substation. Some main parameters of substation:

The building constructed over 500 kV Shin-Toyosu underground subsation, wi𝕴th equipment installed in 4th u๊nderground storey, the 1st ground floor is for substation office, the 2nd floor and higher ones are for rent

- Designed capacit🧸y was 6,480 MVA, current capacity is 6,300 MVA, including:

+ 500/275 kV transformer: 3x1.500 MVA.

+ 275/66 kV transformer: 6x300 MVA.

+ In case of increased load demand, 03 transformers at 66/22 kV (3x60 MVA) will be installed.    – Transmission lines: 02 circ💟uits aꦇt 500 kV, 06 circuits at 275 kV, 15 circuits at 66 kV, 14 circuits at 22 kV (spare, not yet installed).

- The substation has a circle shape to redu✨ce construction cost, divid🙈ing into 3 equal parts for equipment installation:

+ 01 on-ground floor and 4 underground storeys. Floor 1 is for substation’s office, equipment are installed in 4 underground substations. The g🧜round 2nd floor and higher ones are for rent.

+ Area of one floor: 30,000 m2 (equal to 1/9 of out-door tradition 🤪substation🤡).

- Apart from the GIS prꦏimary equipment, the transformers use GIT. Reactors installed in substation have a capacity of 3🀅00 MVA which is highest one in Japan.

500/275 kV GIT transformer

Photo of EVNNPT mission and TEPCO Power Grid expertsꦇ at 500kV GIS underground suꦐbstation

On behalf of the mission, EVNNPT Chairman Dang Phan Tuong honestly thanked leaders of TEPCO, TEPCO Power Grid for sharing informationꩲ and experiences in management and operation of 500♒kV underground substation and unmanned substations./.