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6

I/O Redundancy

6.1

Dual Redundancy

A basic dual redundant control has a sensor connected to an I/O module with one I/O pack that communicates data to two
IONET switches (Refer to the following figure). Each IONET switch transmits the data to both controllers, which are online
and running the same application software.

This configuration has the advantage of network and controller redundancy but no redundancy for the sensor or I/O module.
Another option is adding a second sensor and a second I/O module. This increases the fault tolerance and the ability to
perform online repair at least to the module and possibly to the sensor assuming that the sensor can be replaced while the
process is running. Note that online repair is at the I/O pack level. Therefore, replacement of I/O has minimal impact on
monitoring and control of the overall control system. An extension of this is to add a third sensor whose value can be voted in
the application software. This is an example of triple redundant sensors and I/O modules with dual networks and dual
controllers.

An example of this configuration is in a heat recovery steam generator (HRSG) control that has minimal critical I/O except
for the drum level. Triple redundant sensors can be added just for the drum level control to optimize system availability for
the least cost.

One Sensor & Dual Controllers

Sensor A

+24Vdc

Supports on -line repair 

of IONET switches and 

controllers

Designated Controller

1. Provides the master clock

2. Supplies initialization data

3. Provides recovery data

4. Receives external commands

5. Creates process alarms

8

GEI-100728A

Mark VIe Controls System Redundancy Options

Public Information

Summary of Contents for Mark VIe

Page 1: ...nt contains non sensitive information approved for public disclosure GE may have patents or pending patent applications covering subject matter in this document The furnishing of this document does no...

Page 2: ...Controller 7 5 I O Network Redundancy 7 6 I O Redundancy 8 6 1 Dual Redundancy 8 6 2 Triple Modular Redundancy 11 7 Tripping Reliability 15 8 Digital Bus Reliability 17 8 1 FOUNDATION Fieldbus 17 8 2...

Page 3: ...ting the process Field components for example sensors actuators and wiring cause over half of forced outages Therefore redundancy of field components is an important consideration in the overall contr...

Page 4: ...one component is out voted by the other two In the case of three lube oil pressure switches the protective system performs a simple logical vote with no need to predict in advance a probable failure m...

Page 5: ...ing Blocks Controller 3 IONET Ports 2 Control Network Ports 1 COM Port IONET Switch I O Module I O Pack Local Processor Data Acquisition Terminal Block Typical Mark VIe Architecture Instruction Guide...

Page 6: ...ther the controllers are redundant or non redundant But they can be supplied in redundant pairs too if required Additional redundancy options are available Internal Power Converters Create 28V dc for...

Page 7: ...board rack or mounted inside the rack with communication on the backplane The I O network consists of active electronics at both ends and multiple failure modes so its redundancy is just as important...

Page 8: ...at the I O pack level Therefore replacement of I O has minimal impact on monitoring and control of the overall control system An extension of this is to add a third sensor whose value can be voted in...

Page 9: ...ovides recovery data 4 Receives external commands 5 Creates process alarms Data outputs from dual redundant controllers are normally implemented with each controller sending its signal to its switch a...

Page 10: ...ollers IONET switches and Ethernet ports on a common I O pack which controls a relay driver and a relay Level 2 also provides dual redundant controllers and IONET switches but extends the redundancy t...

Page 11: ...ed or transmitted individually Fanned inputs are transmitted on the IONET with three I O packs on the I O module Therefore a failure of an I O pack does not inhibit any controller from seeing all of t...

Page 12: ...les 3 Less IONET switches Non critical data that is being used for non essential monitoring is usually implemented without redundancy Redundant and non redundant I O coexists in most control systems T...

Page 13: ...nt sharing circuit Analog Voting occurs with a3 coil servo Extended Voting at Field Device Example 3 Coil Servo Valve Actuator Typical nuclear configuration Valve Regulator Valve Ref Valve Regulator V...

Page 14: ...Requirements for no single point failures must be evaluated on a case by case basis to determine the best way to approach this from the system level The preceding figure displays a variation of outpu...

Page 15: ...responding I O control protect and monitor the turbine Primary protection includes a full set of all trip functions and backup protection includes a small subset of the protection functions to backup...

Page 16: ...control valves and de energize the trip solenoids from the primary side Another example the backup protection monitors communications from each controller so it can be configured to initiate a trip o...

Page 17: ...the designated controller and a secondary controller Therefore the primary linking device is the one connected to the primary controller Less common are applications with a single controller and redun...

Page 18: ...al Controllers Supplies Switches Simplex Non redundant Dual with Redundant I O Full Triple Redundant Dual Redundant Triple Relative Contributions to Reliability and MTBFO Adding redundancy to the elec...

Page 19: ...Public Information...

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