A new power opportunity

At 22m high, the Kyröskoski rapids are the biggest rapids of their kind in southern Finland. They are part of the Kyrösjärvi water route, which powers a number of hydro power plants on its way to the Gulf of Bothnia. This is where Kyro started a wood processing business in the 1870s, and began to operate hydro power generation in the 1880s. Today, Kyro no longer operates in wood processing but it has retained its interest in the hydro power business.

Kyro Power began a sizeable investment programme in 1994. The investment programme included a a gas-fired combined heat and power plant, which came on line in 1995, and a replacement hydro plant — an investment of FIM79M — that started up in December 1997. From these two plants the company will now sell over 800,000MWh of electricity, steam, and district heat per year.

The decision to build the new hydro power station in Kyröskoski was made in summer 1996 and construction began in July 1996 of that year. From its single turbine, the plant has an output of 12MW, generating an average of 43,000MWh a year. This is an increase of 60% over the output of the old facility: that plant has five turbines dating from between 1912 and 1936, totalling 4MW or 25,000MWh per year, and it will remain as a standby facility to be used during flood seasons.

As a private power producer Kyro Power had to find a reliable market for its electricity. To this end it has sold the entire output of the new plant, until the end of the year 2002, to Tampere Power Utility.

Tampere Power Utility is a power company fully owned by the City of Tampere. It is one of the oldest municipal power utilities in Europe, as marketing manager Juha Lindholm explains: the utility was founded in 1888 when electric street lighting began in Tampere. Out of a turnover of FIM714M/year the company supplies around 1600GWh of electric power and 1800GWh of district heat. Most of this electricity is generated in Tampere’s two heat and power plants, Naistenlahti and Lielahti. These plants are natural gas (64%) and peat (33%). The remainder of the company’s power arises from oil and biogas, apart from its hydro power capacity, which arises from the company’s hydro power plant at the Tammerkoski rapids in the centre of Tampere city. The utility’s own hydro power production offers peak capacity of only 15MW, Lindholm says, and a result, the utility had very little scope for power regulation.

According to Lindholm, when the liberalisation of the Finnish electricity market allowed third-party access to power grids, it became possible for Tampere Power Utility and other utilities to buy power from an independent power producer like Kyro Power.

The two companies’ co-operation began when Tampere Power Utility bought electricity from Kyro Power’s heating plant in Kyröskoski. The new hydro plant provided another interesting opportunity for Tampere, as Lindholm explains, so Tampere agreed to buy all the power generated by Kyro Power’s new plant from 1 January 1998 until 31 December 2002.

Lindholm notes that because the agreement nearly doubled Tampere’s water power capacity, it meant a significant improvement in power management.

Since the renewal of its own hydro power plant at the Tammerkoski Rapids, Tampere Power Utility has had a Valmet Damatic XD system consisting of process control stations at the Tammerkoski plant and in the control room centre. It was easy to connect Kyro Power’s power plant in Kyröskoski to the same system.

Now the power plant can be controlled either from Tampere or from Kyro Power. Usually, it is controlled from Tampere. Technical maintenance and service is carried out by Kyro Power, Lindholm explains; Tampere Power Utility just buys the electricity and drives the power plant.

The hydro plant uses the premises that were first built for hydro generation in the 1870s. Of the new plant, the only items visible above ground are a machine cabinet by Lake Kyröskoski, the lock house, surge pond and side channel opening by the head of the Kyröskoski rapids, and finally the switchyard and the doorway to the underground machine hall at the bottom of the rapids.

At the start, local environmentalists were opposed to the project because to make room for the new surge pond a section of the river bank with a number of wild plants had to be dredged. In response, Kyro Power involved the local municipality in landscaping the area: now, Kyro says, the new park has become a favourite target for Sunday walkers.

Water reaches the machine hall by two parallel routes, during which it drops 70m from its starting point at Lake Kyröskoski. The 1000m underground waterway originating from Lake Kyröskoski was built in parallel with the Pappilanjoki river route, which used to be the sole source of water for the old plant. Most of the water used by the new plant is delivered via this tunnel, while varying amounts of water from the river are used to regulate production.

Water from the river channel joins the tailwaters from the underground tunnel via a side tunnel which is located by the surge pond 50m above the turbine. The water level in the surge pond is controlled by an overflow wall, which allows water to be discharged into the natural channel in the event of a turbine trip.

At peak production, half the water used by the new plant is taken from the river and surge pond, while at times of low production this share drops to one quarter. The added capacity, according

to Kyro, has doubled production efficiency.

The investment decision was made in early June 1996. PVO-Engineering, a subsidiary of generation company Pohjolan Voima, was employed for general engineering and project management. Veli-Matti Jääskeläinen of PVO Engineering explained that one of the first tasks was to sign the excavation work contract with Finnish construction company Lemminkäinen just a couple of days later. Due to the very tight construction time schedule — the takeover target was 31 December 1997 — the excavation work teams arrived on site immediately.

The contract for civil construction works was awarded to another Finnish construction company: Teräsbetoni. Installation work started in summer 1997 and the first test run was in the beginning of December. Takeover of the plant was accomplished as planned and Tampere Power Utility took over the control of commercial energy production on 1 January 1998 as agreed.

During the project, some 60,000m3 of rock was excavated using conventional methods, of which about 40,000m3 came from the 50m2 head race tunnel, 10,000m3 from the power house and 10,000m3 from other waterways and auxiliary tunnels. The powerhouse was lined with concrete, with most of the tunnels left unlined. Excavation of the tunnel was held up at one point because in one section it passed through a clay region. The course of the route had to be changed and further reinforcement of the tunnel added in the form of concrete, up to 1m thick and 10m in length. For detection of possible movement measuring devices were installed on the reinforcement structures.

Within the powerhouse a four blade vertical Kaplan turbine, including auxiliary equipment, was supplied by Kværner Tamturbine of Finland. With a nominal head of 22m and flow of 60m3/sec it rotates at 214r/min and produces some 12MW. VEM Elektroantriebe from Germany supplied a brushless type vertical generator with rating of 14.5MVA/10.5kV. The generator was completely assembled and tested at the factory, including runaway test with threefold speed.

Operation

The electrical equipment and automation system was supplied by IVO Power Engineering on a turnkey basis. The plant automation system — Damatic XD — was supplied by Finland-based Valmet Automation. Originally designed for pulp and paper plant automation, this system has for some years been used for control of large thermal power plants. Now, as Risto Koivunen of IVO Power Engineering explains, even small-scale applications such as the Kyro hydro plant have become economically feasible - especially where existing Damatic control systems are in use.

Critical functions

The critical functions of Damatic XD include safe shutdown, even in the event of a malfunction in the automation system. Damatic also implements

the turbine governor function;

for this purpose a special intelligent

interface card with a fast response time is required. The plant ventilation and heating is controlled directly by the Damatic XD system, without the aid of conventional subordinate control systems. This aids preventive maintenance work and helps to speed up fault location.

To help reduce running costs, the hydro plant software is connected to the control room at Kyro Power’s gas fired plant, some 600m away. A distributed control system was chosen as an extension to the gas fired plant’s control system.

Both plants are controlled by the same operator, via uniform display windows. For local maintenance purposes, a simplified control room has been installed at the hydro plant. Maintenance is carried out by personnel who also work on the gas-fired plant, following additional training.

As well as local operation, day-to-day control and operation of the hydro power plant is carried out remotely. This is done via a remote-control interface of the DCS system from Tampere Power Utility, 40km away, which is the user of the power from the hydro plant.

The Damatic system is connected, through a serial data transmission link, to the similar hydro power production control system at Tampere. All the principal supervisory, control and data acquisition functions of the power plant are available through the link.