In accordance with the IEC 61362 standard of the International Electrotechnical Commission, hydraulic‑electrical servo control systems with redundant design are required for turbine governor units. Typically, such systems must ensure full‑stroke operation of at least three servomotors during both opening and closing actions, and they must be capable of fully closing the governor servomotors even under low‑oil‑pressure fault conditions. Furthermore, in normal operating mode, the accumulator can provide fine‑tuning to support the governor’s performance.
1. The accumulator system shall be equipped with an energy monitoring system to ensure the implementation of the shutdown function under emergency conditions.
2. When a low-pressure hydraulic control system is employed, an accumulator equipped with a liquid-level monitoring function—typically with a rated working pressure not exceeding 9 MPa—is generally used.
3. When a high-pressure hydraulic control system is employed, a piston-type accumulator system equipped with a liquid-level monitoring system shall be used.
4. In accordance with IEC 61362, clause 5.1.2, since the energy of bladder-type accumulators cannot be directly monitored and bladder rupture cannot be entirely prevented, such systems are, in principle, not recommended.
Compared with a medium-pressure hydraulic speed‑control system that uses a 6.3 MPa pressure‑mixing tank, the piston‑type high‑pressure hydraulic control system, equipped with a mature piston‑displacement monitoring device specially developed by SCHWERLL for hydro‑turbine power‑generation systems, not only ensures reliable monitoring of energy within the pressure‑tank system but also offers the following advantages:
1. There is no longer a need to install an air compressor system, which reduces the installed capacity and operating noise while significantly decreasing the maintenance workload of the hydraulically controlled power‑supply system.
2. High-pressure piston‑type systems offer greater energy density, accommodate a wide range of system sizes, enhance the compactness of system installation, and enable long‑term maintenance‑free operation.
Precautions for using high-pressure hydraulic systems:
1. Users must select high-pressure piston accumulators that comply with the special equipment regulations of the installation location. For example, in China, accumulators are required to have a type‑test report, a TS stamp, and a supervision‑inspection certificate issued by a qualified Chinese government agency.
2. Bladder accumulators are not suitable for high‑pressure hydraulic systems, as their design does not allow for effective monitoring of the compressed gas energy within the system and poses the risk of pressure surges entering the working system in the event of bladder rupture.
3. Piston-type accumulators equipped with a reliable energy-monitoring system should be selected to ensure that their gas-compression energy can be monitored.
