HIERARCHIES OF ALARMS FOR LARGE DISTRIBUTED SYSTEMS

The control systems of most of the infrastructure at CERN make use of the SCADA package WinCC Open Architecture by ETM*, including successful projects to control large scale systems such as the Large Hadron Collider (LHC) accelerator and associated experiments.). Each of these systems features up to 150 supervisory computers and several millions of parameters [1]. To handle such large systems, the control topologies are designed in a hierarchical way (i.e. sensor, module, detector, experiment [2]) with the main goal of supervising a complete installation with a single person from a central user interface. One of the key features to achieve this is alarm management (generation, handling, storage, reporting). Although most critical systems include automatic reactions to faults, alarms are fundamental for intervention and diagnostics. Since one installation can have up to 250k alarms defined, a major failure may create an avalanche of alarms that is difficult for an operator to interpret. Missing important alarms may lead to downtime or to danger for the equipment. This paper presents the features and benefits of hierarchical alarms.