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High-availability assures productivity

Faults and failures of mission-critical components reduce productive times of machines and plants. Moreover they often result in consequential damages and protracted repairs. In this regard, high costs are incurred and the production downtime causes economic losses.

Redundancy solutions from Bachmann electronic specifically and sustainably increase wind turbine availability: Implementation variants that are tailored to each task reduce downtimes and optimize productivity and operational reliability. Seamless embedding in the existing and proven hardware, engineering, and programming concept, combined with the robustness of proven Bachmann components, guarantee maximum operational reliability and maximize profit. This optimal combination guarantees not only consistent single-fault tolerance, but in many cases it even guarantees multiple-fault tolerance.

CPU redundancy

CPU redundancy

If critical tasks are executed by a central master CPU, then a redundant design protects the master against the loss of these functions.

This CPU - or master redundancy can be implemented through different methods:
1) Hot-standby redundancy
2) Warm-standby redundancy

The main difference between the solution approaches is the behavior during the switchover between the two master CPUs when the active master fails. In this regard the key issues are the time required for the change, and whether the switchover can occur without impact.

Hot-standby redundancy

Hot-standby redundancy

In the hot-standby system the spare CPU (master B) works synchronously with the main CPU (master A). It gets the same input values and calculates the output values via the same application program. Integrated self-monitoring and external monitoring mechanisms of the master CPU guarantee the fastest possible reaction to deviations in the intended operation. Relevant process variables and inner status are cyclically compared between the master controllers and automatically calibrated if necessary.

The system environment and special extensions in the development tools support interruption-free programming, monitoring and online maintenance.

The illustration shows the diagram of a hot-standby redundancy implementation with cyclic calibration between the redundancy masters and time-synchronized stations.
Through the impact-free switchover, hot-standby redundancy is particularly well-suited for critical monitoring, control, and regulating tasks.

Warm-standby redundancy

Warm-standby redundancy

Warm-standby systems are characterized by the fact that the spare CPU (master B) is active in parallel with the main CPU (master A), and in the ideal case, receives and processes all data of the connected substations. Integrated self-monitoring mechanisms enable automatic fault detection. This results in autonomous switchover if the active master fails - an external trigger can be dispensed with. The switchover time relative to the comparable cold-standby system is significantly reduced in this process.

In spite of parallel reading and processing of input data status information, measured values and status between both master systems is not synchronized. Autonomy of the master controllers is a characteristic feature of warm-standby redundancy and stipulates that likewise only a hard, but temporally direct switchover is possible.

Application areas for warm-standby systems have the prerequisite of acceptance of loss of the processing history or a hard switchover of the master controllers. This particularly applies for applications that only have read access to network components and intelligent systems. Thus warm-standby redundancy is a cost-effective and reliable solution for alarm and monitoring systems, for example.

Network redundancy

Network redundancy

Network redundancy = communications + media redundancy
Frequently malfunctions can be attributed to disturbed or faulty data transmission channels. In this case the remedy is use of communication or media redundancy.

The core principle of communication redundancy is transmission of the information two or more times. If this occurs sequentially via the same signal line, a reduced effective bandwidth, as well as possible complete failure in the event of connection problems, must be taken into account. Individual errors in data packets can be reliably corrected through this method.

When using media redundancy the physical transmission channel is doubled. If, in this process, different cabling routes are implemented, the risk of total failure due to a single event is practically eliminated.

Only through concurrent application of both technologies can the best availability be achived. This combination of communications and media redundancy is summarized under the term, network redundancy.