The detection of leaks is one of the most important and security-relevant topics within hydro power plants. Especially at high head plants leaks can cause hugh damage to environment and the plant itself. Beside leak detection the turbines should be operated with optimal efficiency. For both tasks reliable and precise flowmetering of penstocks and turbine lines is essential. systec’s ultrasonic multiple-path flowmeter fit’s both applications and offers accuracy of up to 0.5% according to IEC41 standard. Ultrasonic transducers for pressures exceeding 100bars are available.

With a nominal power of 420 MW the pump storage hydro power plant Gigel Gibe II in Ethiopia boosts the national power production. It mainly supplies the million-resident metropolis Addis Abbeba and is expected to give Ethiopia a significant economical boost.

The main contractor is the company Salini the Italian specialist for Hydro Power Plants. A famous German manufacturer supplied the 4 105MW turbines and the control and communication system.

Gigel Gibe II - Penstocks

Because of the high head of almost 500 meters and therefore the high pressure and flow rates leak detection is a essential part of the plant’s saftey structure. In case of detected leaks the Penstocks will be shut-off by valves.

Reliable leak detection and optimized turbine regulation are only possible if related flow rates are measured precisely. At Gigel Gibe II there are two balances each consisting of one Penstock and 2 Turbine measurements. Each balance is controlled independently. systec Controls supplied deltawave ultrasonic flowmeters for measuring 2 Penstock and 4 Turbine lines and a Leackage Master who is doing the leak detection of the two balances.

Mounted Ultrasonic Transducers at Turbine Lines

Both Penstocks has been equipped with 8 acoustic paths. Each of the 4 turbine lines with 4 acoustic paths. All 6 sites are in accordance to the international standard IEC41. The ultrasonic transducers are feed into the pipe via welding studs with ball valves (quick-lock system). With the quick-lock system the transcuers can be fully exchanged during pressurized conditions.
A interminable and expensive shut-down of the site is therefore not required.

deltawave electronic unit

The ultrasonic paths are connected to and controlled by the deltawave electronic unit which then does the flow calculation. Each acoustic path has an update rate of up to 128 per second which makes deltawave a ultra-fast meter for high dynamic situations. Each deltawave offers analogue (4…20 mA) as well as digital signal outputs (RS232, USB, Ethernet). At Gigel Gibe II signal are proceeded by Ethernet using fibre glass network. One deltawave unit can run up to 16 acoustic paths at 4 independent pipes. Thanks to this multi-channel technology price per site can be significantly dropped.

deltawave Leakage Master

The individual flow measurements are connected to the deltawave Leakage Master who is continuously comparing the inflow (penstock) with the two outlfows (turbine lines) of each balance. The connected deltawave flowmeters proceed their signals via Ethernet.
In case of leakage the leakage master will automatically activate a shut-off valve by digital output. To cope with the high flow dynamic (run-up, shut-down) and to avoid unplanned shut-offs different thresholds can be preseted at the Leakage Master

Beside leakage detection each of the 4 turbine flowmeters are also used for optimizing the efficiencies. In addition to that the deltawave system works according to the IEC41 standard and can be used for field acceptance tests of hydraulic turbines.

In total 6 different pipes are measured with the deltawave system. The combination of 8 paths (Penstocks) and 4 path arrangement (Turbines) means an affordable and precise solution for the customer. Despite the unfavourable inlet conditions a system accuracy of 0.3% has been achieved after calibration of the penstock measurement to the related turbine measurements. The additional leakage master compares the flow rates and will trigger a shut-off in case of detected leakage. Threee individually presettable thresholds meet the high dynamic of the flow of the hydro power plant.

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