TSODS

TSODS Architecture Overview

The TSODS system includes three speed detection modules (SDMs), a management and communication module (MCM), and a module terminal interface (MTI) that provides the cage and backplane to accommodate and connect the MCM and SDM modules.

The MCM communicates with the three SDMs through the COM_BUS on the MTI backplane. The three redundant SDMs communicate with each other through the point-to-point SDM_BUS, which is also located on the MTI backplane. The TSODS interacts with external interfaces through Ethernet (Modbus TCP or OPC UA), an RS485 serial port, or Bluetooth BLE. Power for the TSODS is supplied by redundant 24vdc power supply terminations. The two power supply inputs are connected to the triple SDMs and MCM module through the MTI backplane.

The TSODS system provides two dedicated digital input interfaces for reset and start functions, and the reset and start signals enter the triple SDMs and MCM module, respectively, through the backplane. Each SDM module I/O includes (1) speed signal input, (1) forced trip signal input, (1) measured speed readout (4~20mA), and (1) alarm relay output. Each SDM provides 6 trip relay outputs, which are 2oo3 voted on the MTI backplane. The MCM I/O includes (1) dedicated clock synchronization signal input, (2) hydraulic trip block inter-valve cavity pressure feedback inputs (4-20mA), (4) test inputs, and (1) system alarm relay output, which are connected to the MCM via the MTI terminations and backplane.

SPEED DETECTION MODULE RELAY VOTING ARCHITECTURE

The TSODS achieves its extended proof test interval (20 years) in part by using relays with forcibly guided contacts (safety relays). Each of the three SDMs features force-guided relays for four out of the six trip outputs (two of the six trip outputs are intended to communicate trip status). All of the SDM relays are voted in a two-out-of-three schema on the TSODS MTI backplane. 

MAIN COMMUNICATIONS MODULE (MCM)

The MCM has two variations, one with and one without a touchscreen human machine interface. Both variations provide external communications (serial and Ethernet), as well as a Bluetooth BLE interface. The MCM communicates with each SDM via the Comm_Bus on the MTI backplane.

SPEED DETECTION MODULES (SDM)

The TSODS includes three independent speed detection modules. Each module compares its measured speed input with the configured overspeed trip threshold and drives its respective trip outputs accordingly. The three independent SDMs form the TMR architecture to achieve unparalleled safety and availability. 

Three Speed Detection Modules - typical for each TSODS

MODULE TERMINATION INTERFACE (MTI)

The MTI provides the cage and backplane to accommodate and connect the MCM and SDM modules. It also provides the electrical power connection, interconnected communications buses for the MCM and SDM, and the instrument wiring termination interface.

MTI Cage, Backplane, Field Termination Interface

TSODS MTI Connection Diagram

PC Windows™ based Configuration Interface 

The TSODS Configurator software is a "drop-down", menu-driven configuration and monitoring interface that runs on a Windows PC or notebook computer and connects with the TSODS through a proprietary communication protocol using an Ethernet communications interface.

• Status Monitor: Real-time monitoring of the TSODS status and diagnostics, graphical and contextual I/O operational data, and alarm information. 
  
  
• Configuration: Provides current configuration parameters in both graphically and contextually as well as the ability to modify configuration parameters both off and online (with appropriate credentials).
  
  
• Test: Access to conduct both manual and automatic overspeed testing as well as the automatic valve sequence test (for TetraSentry), and ODS indicator light test.
  
  
• Event Review: Access to read event logs, save event logs to micro SSD, save logs, clear logs (with proper access authority, clear peak speed (with proper access authority)

Acceleration Compensated Trip Setpoint (ACTS)

When the ACTS function is disabled, TSODS executes the overspeed trip function. Each SDM module detects the speed of the monitored equipment in real-time and compares it with the configured "normal overspeed trip setpoint" (nTSP)  to detect the overspeed event and generate a trip command.

When the ACTS function is enabled,  the TSODS executes the overspeed trip function based on a configurable acceleration-compensated overspeed trip setpoint (aTSP), effectively lowering the overspeed trip setpoint. The compensation is accomplished by comparing a configured acceleration value (Max_accel) to the actual measured acceleration, and adjusting the "calculated" overspeed trip setpoint between the normal trip setpoint and the acceleration compensated trip setpoint.  

If the current measured acceleration is equal to zero, the calculated trip setpoint is equal to the normal trip setpoint. If the measured acceleration is equal to or greater than the maximum acceleration, the calculated trip setpoint is equal to the acceleration compensated trip setpoint. 

The function for this compensation is:  
cTSP = nTSP − [nT𝑆𝑃−aT𝑆𝑃 / 𝑀𝑎𝑥_𝑎𝑐𝑐𝑒𝑙]∗𝐴𝑐𝑐𝑒𝑙

cTSP = calculated actual overspeed trip setpoint
nTSP = configurable normal overspeed trip setpoint (highest overspeed trip setpoint)
aTSP = configurable acceleration compensated trip setpoint (lowest overspeed trip setpoint)
Max_accel = configurable maximum acceleration
Accel = actual measured acceleration

Manual and Automatic Overspeed Trip Testing 

While the proof test interval for the TSODS is 20 years, the TSODS includes multiple overspeed testing schema. Depending upon the MCM configuration, the TSODS can have up to four different ways to accomplish overspeed testing. 

• Local Temporary Overspeed Setpoint Test: The turbine overspeed test is initiated from the MCM (with touchscreen. It typically involves temporarily lowering the ODS overpeed trip setpoint below the normal trip setpoint and testing the turbine trip using the actual turbine speed. 
  
  
• Local manual simulated overspeed testing: This test uses the speed signal generated by the frequency generator within a given SDM to test a given SDM's overspeed trip function. Through the MCM (with touchscreen), the operator can manually increase/decrease the frequency from the SDM's internal frequency generator to validate an SDM's overspeed trip function.
  
  
• Local automatic overspeed testing: This test also uses the speed signal generated by the frequency generator within a given SDM to test a given SDM's overspeed trip function. Through the MCM (with touchscreen), the operator can initiate an automatic test using the frequency from the SDM's internal frequency generator to validate each of the SDM's overspeed trip functions.
  
  
• Remote automatic overspeed testing: The remote automatic overspeed testing is similar to the local automatic overspeed test with the added functionality of using a dedicated "write command" from a remote interface (using Modbus RTU, Modbus TCP, or OPC UA)

Tri-Sen TetraSentry Hydraulic Trip Interface and Testing

When the TSODS is coupled with the TetraSentry hydraulic trip interface, the TSODS  "Auto Sequence Valve Test" function can be enabled to automatically test the TetraSentry online.  While the TetraSentry has TUV-certified SIL 4+ reliability, it's strongly recommended that the TetraSentry cartridge valves are "exercised" on a regular basis to ensure they don't become "sticky" due to contaminated system oil. The TSODS is able to provide perfectly integrated, complete automation of this recommended testing/exercising along with recording and logging performance metrics. 

This sequence valve test is intiated from the TSODS touch screen, by a dedicated write command on a communication port (Modbus RTU, Modbus TCP, OPC UA), or automatically by a configurable timer within the TSODS.