●Research Trends and Results

Towards the utilization of hydraulic energy inriver basins
TORII Kenichi (Phd. Eng.), HeadYAMAMOTO Yoko, Senior Researcher
River Department, Water Management and Dam Division(Key words) Generating electricity for dam management use, maintenance, inspection frequency
1. Introduction
The nationwide shortage of electric power causedby the Great East Japan Earthquake may continue fora long time, and hydroelectric power, which is areusable energy, is expected to be utilized andpromoted more than ever. Among dams managed bythe Ministry of Land, Infrastructure, Transport andTourism and by the Japan Water Agency, management
use electric power generation equipment which uses
maintenance discharge and water supply discharge
from dams had already been installed at 28 dams
nationwide (January 2011), and while they supply
electric power to be used for dam management, they
have further reduced the cost of dam management
through the sale of surplus electrical power. More than
30 years have passed since the start of operation of thefirst management use electric power generating
equipment, which was installed around 1980, and thecost of renewal and maintenance of the equipment ispredicted to increase in the future. And because thequantity of electric power will continue to increase, itis essential to increase the efficiency of maintenanceto boost the cost-benefits of installing new electric
power generating equipment.
This research studied measures to increase of theefficiency of maintenance of management use electric
power generating equipment in order to make greateruse of unused hydraulic energy of river basins.
2. Present state of maintenance of dam
management use electric power generating
equipment
When management use electric power generation isshut down, purchasing management use electric powerincreases maintenance cost while income from the saleof electric power falls, so it is necessary to absolutely
minimize system shut down time. A questionnaire
survey of inspections, renewals, and othermaintenance of electric power generating equipment
was carried out at the 28 dams equipped withmanagement use electric power generating equipment.
The results show that the systems are shut down forinspections or by malfunctions an average of 14.7
days/year, and of these, electric power generators areshut down for periodical inspections of the electricgenerators or gate equipment an average of 4.1 days.

But, if equipment is inspected by dismantling
maintenance, power generation is shut off an averageof 41.8 days. Electric generating equipment was only
shut down by a malfunction 16 times, but the impact
was severe, because the average length of time it was
shut down for restoration was an average of 41.3 days.
Electric power generating equipment was shut down
by malfunctions an average of 14.2 years after it
started operation. Renewal of equipment now almostentirely involves electric parts and occurs an averageof about 19 years after the start of operation.

Photo 1. Management Use Electric Power Generating
Equipment (Sagae Dam)
3. Efficient electric power generating equipment
maintenance methods
Through an analysis of maintenance costs revealedby the questionnaire, it was discovered thatapproximately 3/4 of inspection and maintenance costs
is the cost of dismantling maintenance. Looking at thereason for performing dismantling maintenance showsthat about 3/4 is carried out according to an ordinary
inspection cycle for each part (time plan). For thisreason, it is possible to further reduce maintenancecosts by performing dismantling maintenance at a low
frequency but often enough to prevent malfunctions
caused by insufficient maintenance. This researchclassified ways of renewing each type of part(preventive maintenance, post-maintenance) based on
degree of importance and restoration period. At thistime, data concerning past malfunctions and renewals
are limited, so in order to decide the appropriate
frequency of inspections and renewals, continuous
data must be accumulated in the future.

●Research Trends and Results
4. Future study guidelines
In the future, to explore further potential uses ofhydraulic energy, we will study measures to increaseelectricity by selecting new installation locations for
management use electric power generating equipment
and renewing the reservoir water level operation ofmulti-purpose dams, and study challenges such as theimpact of implantation on river environments andsystemic restrictions, etc.