By Shinsuke Ishihara
Editor’s Note: The Hydro Review editors have been inducting historic hydropower plants into our Hydro Hall of Fame since 1995. More than 40 plants in the U.S. and Canada have received this prestigious designation – awarded for their long-lasting and significant contributions, including clean renewable power, emission-free generation and reliability. For the first time this year, the editors expanded the criteria to include facilities outside North America. We are proud to announce that 250-kW Miyashiro No. 1 is the first “international” hydro facility to receive this award.
The Miyashiro Power Plant No. 1 was commissioned on Sept. 14, 1904, by Japan’s Azumi Electric Power Co. After more than 112 years, the original turbine-generator unit in the now 400-kW plant – Unit 2 was added in 1914 – is still running. Annually, the plant generates 3,024 MWh using an effective head of 50.72 m (166.4 ft) and a water flow of 1.11 m3/s (39.2 cubic ft per second) from the Hodaka River, a branch of the Shinano River.
The plant is now owned and operated by Chubu Electric Power Company Inc. (CEPCO) in Japan. In addition to its headquarters in Higashi-ku, Nagoya, Japan, the company has offices in Washington D.C.; London; and Doha, Qatar. CEPCO’s facilities have a total installed capacity of 34.1 GW, which includes 5,320 MW of hydropower in 189 locations.
Background to Miyashiro’s development
The beginning of electrification in Japan can be traced to March 25, 1878, when the arc light was introduced. At the time, 15 minutes of continuous lighting operation was regarded as successful. However, it is said the arc light at this first lighting went off soon after it was lit, before applause for the event concluded.
Some people foresaw the future profitability in the electric power industry and planned to conduct business. But, it was not until nearly 10 years later, in 1887, that Tokyo Electric Light Co. was established.
At that time, the company generated electricity from a small thermal plant that was distributed to about 130 consumers through overhead wires using low-voltage DC. Due to the popularity of electricity in the area, and all it afforded the populace, within a four-year span the company had more than 10,000 consumers, but the system faced the technical constraint of a low-voltage DC line.
During the same time period, Osaka Electric Light Co., established in 1889, adopted a high-voltage distribution system, which U.S.-based Westinghouse Electric recommended. Osaka Electric expanded the electricity supply into urban areas after realizing a low tariff because of the low distribution costs.
The price of coal used to fuel thermal plants in Japan surged, and the growing power industry began to focus on hydropower because the energy source had lower generating costs.
Against this background, Yokozawa Honei, a capitalist living in Nagano prefecture, partnered with 19 people and acquired permission to use water from the Chubou River to generate electricity. Honei founded Azumi Electric Power Co. in 1902.
|The original Voith turbine at Miyashiro No. 1 Power Plant.|
The Miyashiro No. 1 plant, the first built by this new company, was located at a site in which base rock layers existed and the civil engineering work took more time than initially expected. This is because compared with other sites in Japan, this site has an unusually high ratio of rock. The turbine, generator and speed governor were purchased from Voith Hydro in Germany and the generator was a 250 kVA, 500 V, 50 Hz AC rotating magnetic field type.
The Russo-Japan War broke out in 1904, causing delays in procuring the turbine and generator from Germany. However, these difficulties were overcome and the plant began operation in 1904, supplying electricity to more than 2,000 rural households.
According to a newspaper article at that time, “The instruments and switches look brilliant as they are Siemens design. The turbine and speed governor are made by Voith Hydro. Even though the performance shouldn’t be speculated from their appearance, the paint and the finished surface are glossy and look superb. I guess it must be the best turbine and generator in Japan.”
Another newspaper article written in 1905 says, “The speed is adjusted by a mechanical speed governor made and patented by Voith, which is invented by a German professor ‘Oscar G.’ The speed variation is within 3/100 when the load varies by 5/100, furthermore it is within 6/100 when the load varies from zero to full.”
However, it took a substantial amount of time to earn a profit in the electric power industry in Japan at that time because most people could not afford to pay the tariff. and it took several years before the plant returned a profit. Honei remained in business, but he was forced to spend large amounts of personal assets. He was dedicated to providing reliable electricity in rural areas. Even though there was greater profitability in supplying urban areas, Honei was committed to developing the local economies rather than only seeking profit.
Current status at Miyashiro No. 1
After Miyashiro No. 1 commenced operations in 1904, Azumi Electric Power added Unit 2 in 1914, increasing the total capacity to 400 kW. Currently, the capacity of Units 1 and 2 are 260 kW and 280 kW, respectively, and the generators are 250 kVA and 280 kVA, respectively. The generators were modified to adopt a rotating commutator and achieved a brushless structure. The generator voltage is 500 V and is uprated to 11 kV by a step-up transformer to transmit power to the grid.
After operation began, the major modifications required for Unit 1 were a runner and guide vane replacement in 1927, as well as runner replacements in 1940, 1967 and 1991. The Unit 2 runner was replaced in 1967 and the entire unit was replaced in 1991. The runners were so frequently replaced because Hodaka River water contains a relatively large amount of sand particles, causing the runner to suffer a heavy degree of frictional damage.
|Miyashiro No. 1 is part of a five-plant cascading system on the Hodaka River.|
The governor for each unit was modified from mechanical to speederless in 1987. The generator, a collector ring and a brush were replaced in 1955 and the winding of the exciter was replaced in 1980. The insulator stators of both units were replaced in 1983.
The facility also needs continual physical maintenance. Conduits at hydropower facilities in Japan sometimes become infested by Corixidae, an invasive aquatic insect, and the conduit of Miyashiro No. 1 is not immune. Corixidae reside at the inner surface of the pipe and form a nest, causing head loss and lowering the generation output. For this reason, the maintenance staff regularly has to venture inside a pipe that has a diameter of only 60 to 100 cm to scrub the inner surface.
To this day, the overall performance of the original Unit 1 has been successfully maintained with only partial equipment replacement, all the while not having suffered a major electrical accident.
Further hydropower development
Miyashiro No. 1 is now part of a five-plant cascading system CEPCO operates on the Hodaka River (see Figure 1, page 18)system that includes: 470-kW Miyashiro No. 2, 720-kW Miyashiro No. 3, 720-MW Chubou No. 4, and 220-MW Chubou No. 5.
Miyashiro No. 2 was constructed in 1918 with a similar design to Miyashiro No.1, in terms of water intake, and is located upstream. This way, the tailrace of Miyashiro No. 2 and the intake of Miyashiro No. 1 are connected.
Miyashiro No. 3 was constructed downstream of Miyashiro No. 1 in 1920 and it harnessed water discharged from its newly built weir and water from Miyashiro No. 1.
Chubou No. 4 was constructed in 1925 and is located further upstream from Miyashiro No. 2. The tailrace of Chubou No. 4 was connected to the intake of Miyashiro No. 2, resulting in the connection of all three plants to the tailrace and intake.
Interestingly for that time period, Chubou No. 4 was equipped with a regulating pondage within the conduit, enabling its operation to meet the daytime peak demand. Because Chubou No. 4 could operate as a peak supply, the other two connected plants could also operate as peak supply.
|Villagers manually transport a 250-kW turbine-generator to the Miyashiro No. 1 Power Plant, circa 1903. View a video about the project at http://bit.ly/2dmxCbE|
In 1927, Chubou No. 5 was constructed towards the upper stream of the Hodaka River, and it is located at the highest elevation among the five projects. Additionally, because all five were connected with the tailrace and intake, they could operate simultaneously with Chubou No. 5 and the lowest elevation facility, Miyashiro No. 3.
Although Miyashiro No. 1 is connected to Miyashiro No. 2 through No. 2’s tailrace, the maximum water usage at Miyashiro No. 2 (1.2 m3/s) exceeds that of Miyashiro No. 1 (1.11 m3/s). For this reason, the connecting conduit is equipped with a diversion tank, which returns excess water to the Hodaka River.
CEPCO was formed in 1951 after World War II. The demand for electric power accelerated due to postwar rehabilitation and special procurement for the Korean War. Under regulation from the government, electric power companies were reorganized to achieve an integrated power supply system at each region. This is when CEPCO acquired Miyashiro No. 1 and all of the plants in the system.
Balancing 50 Hz vs 60 Hz
In Japan, some of the power generating equipment procured from Germany, as was the case with units for Miyashiro No. 1, was 50 Hz. In contrast, equipment in other areas of the world was supplied by U.S. manufacturers and utilized 60 Hz generators. The different frequencies coexist in Japan, with the border located in Nagano prefecture (where Miyashiro No. 1 is located), dividing the land into a 50 Hz area in the east and a 60 Hz area in the west.
Most of CEPCO’s supply area, including Nagano prefecture, is supplied with 60 Hz. In 1951, a plan to unify the frequency to 60 Hz in all of Nagano prefecture was suggested, with a goal of realizing a rational and reliable power system. A 50 Hz and 60 Hz system cannot be connected together unless special equipment is used. For this reason, the 50 Hz system was independent and can easily be stopped if any small accident happens. If unified to either 50 Hz or 60 Hz, the system will be stronger and more reliable. The plan to change the frequency of Miyashiro No. 1 from 50 Hz to 60 Hz was also suggested around this time.
This change was an enormous challenge for CEPCO. Forming the 60 Hz power grid in some areas, including the area of Miyashiro No. 1, was geographically difficult. In addition, consumers who use the 50 Hz facility would have to change their facility because equipment that uses 50 Hz cannot be used under the 60 Hz power system (i.e., voltage transformer that use 50 Hz cannot be used in other frequencies). Considering all of these difficulties, CEPCO chose to leave the facility at 50 Hz.
During the postwar period, because the 50 Hz supply area (which included Tokyo) had so much demand and scarce supply, CPECO helped the 50 Hz area by converting the 60 Hz hydropower plant to 50 Hz.
Maintaining the legacy
When it was commissioned in 1904, the 250-kW Miyashiro No. 1 Power Plant played a vital role in supplying electricity in Azumino, Nagano. In honoring this spirit and maintaining the legacy facility, CEPCO organized a 100-year anniversary ceremony for Miyashiro No. 1 in 2004.
With a sense of respect and gratitude to the spirits of the great people from the past who built our nation, it is with humility and purpose of excellence that CEPCO continues to operate the oldest hydropower facility in Japan.
Shinsuke Ishihara is a hydropower engineer at Chubu Electric Power Company Inc.