Overspeed protection is a key requirement in the power generation industry where failure of the turbine or pump speed governing system can lead to rotor damage with expensive consequences. Independent speed monitoring and protection is therefore an essential requirement to minimise these risks as far as practicable. Condition monitoring specialists SENSONICS have provided high integrity overspeed protection systems for over 20 years with proven field reliability. The design of the system and functions offered have been developed and enhanced in conjunction with our customers in both the conventional and nuclear power industry, resulting in a highly reliable hardware configuration with online test facilities.
Sentry G3 is Sensonics latest generation of protection equipment for overspeed protection applications. The four channel G3 module has been specifically designed with an independent digital signal processor (DSP) for each channel of measurement providing ease of scalability in combination with high integrity. The DSP can be software loaded with the specific measurement algorithm which not only controls the sensor selection, but also the protection relay status and analogue output levels. This provides complete hardware autonomy from sensor through to the protection relay combined with a high channel density (24 channels in a 3U format).
It is typical for overspeed protection to utilise a two out of three (2oo3) voted channel arrangement to meet with stringent spurious trip requirements. This is implemented in G3 by utilising 3 modules, each with a single DSP channel to maintain channel hardware segregation, and configured with the overspeed algorithm. G3 offers the advantage that the remaining module channels can be utilised for other machine measurements such as bearing vibration, shaft position or temperature. Alternatively the DSP cards can be removed for a more cost effective solution.
The rack based system operates on a dual +24V power supply backplane, either connected externally, or derived from the optional G3 dual redundant rack based power supplies. A voting module incorporating various test facilities is situated in the rack to perform the 2 out of 3 voting function.
When high integrity protection is required, the IEC61508 international standard for functional safety can be applied to ensure that sufficient integrity is designed into the electrical / electronic systems employed for the safety function. The Sentry G3 OSP achieves a SIL 3 rating in this respect.
Key elements of the Sensonics Overspeed Protection System:
- Voted arrangements - 2 of 3 and dual 2 of 3 as standard.
- On line test trip and signal injection facilities.
- Key lock inhibit.
- High visibility displays and lamps.
- Approval to IEC 61508.
- Dual redundant or module independent power supply option.
- Response time <20ms.
Sentry G3 for overspeed protection is another example of Sensonics dedication to developing affordable, high integrity machine monitoring and protection systems for all areas of industry.