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5.8 Alarm model ToC Previous Next

5.8.12 Exclusive Limit Types ToC Previous Next

5.8.12.1 Overview ToC

This clause describes the state machine and the base Alarm Type behaviour for AlarmConditionTypes with multiple mutually exclusive limits.

5.8.12.2 ExclusiveLimitStateMachineType ToC Model

The ExclusiveLimitStateMachineType defines the state machine used by AlarmConditionTypes that handle multiple mutually exclusive limits. It is illustrated in Figure 17.

readme_files/image019.png Figure 17 – ExclusiveLimitStateMachineType

It is created by extending the FiniteStateMachineType. It is formally defined in Table 61 and the state transitions are described in Table 62.

Table 61 – ExclusiveLimitStateMachineType definition

Attribute Value
BrowseName ExclusiveLimitStateMachineType
IsAbstract False

Subtype of the FiniteStateMachineType

References NodeClass BrowseName DataType TypeDefinition ModellingRule
HasComponent Object HighHigh   StateType  
HasComponent Object High   StateType  
HasComponent Object Low   StateType  
HasComponent Object LowLow   StateType  
HasComponent Object LowToLowLow   TransitionType  
HasComponent Object LowLowToLow   TransitionType  
HasComponent Object HighToHighHigh   TransitionType  
HasComponent Object HighHighToHigh   TransitionType  

Table 62 – ExclusiveLimitStateMachineType transitions

BrowseName References BrowseName TypeDefinition
       
Transitions      
HighHighToHigh FromState HighHigh StateType
  ToState High StateType
  HasEffect AlarmConditionType  
HighToHighHigh FromState High StateType
  ToState HighHigh StateType
  HasEffect AlarmConditionType  
LowLowToLow FromState LowLow StateType
  ToState Low StateType
  HasEffect AlarmConditionType  
LowToLowLow FromState Low StateType
  ToState LowLow StateType
  HasEffect AlarmConditionType  

The ExclusiveLimitStateMachineType defines the sub state machine that represents the actual level of a multilevel Alarm when it is in the Active state. The sub state machine defined here includes High, Low, HighHigh and LowLow states. This model also includes in its transition state a series of transition to and from a parent state, the inactive state. This state machine as it is defined shall be used as a sub state machine for a state machine which has an Active state. This Active state could be part of a “level” Alarm or “deviation” Alarm or any other Alarm state machine.

The LowLow, Low, High, HighHigh are typical for many industries. Vendors can introduce sub-state models that include additional limits; they may also omit limits in an instance. If a model omits states or transitions in the StateMachine, it is recommended that they provide the optional Property AvailableStates and/or AvailableTransitions (see OPC 10000-5).

5.8.12.3 ExclusiveLimitAlarmType ToC Model

The ExclusiveLimitAlarmType is used to specify the common behaviour for Alarm Types with multiple mutually exclusive limits. The ExclusiveLimitAlarmType is illustrated in Figure 18.

readme_files/image020.png Figure 18 – ExclusiveLimitAlarmType

The ExclusiveLimitAlarmType is formally defined in Table 63.

Table 63 – ExclusiveLimitAlarmType definition

Attribute Value
BrowseName ExclusiveLimitAlarmType
IsAbstract False

Subtype of the LimitAlarmType defined in clause 5.8.11.

References NodeClass BrowseName DataType TypeDefinition Modelling Rule
HasSubtype ObjectType ExclusiveLevelAlarmType Defined in Clause 5.8.14.3    
HasSubtype ObjectType ExclusiveDeviationAlarmType Defined in Clause 5.8.15.3    
HasSubtype ObjectType ExclusiveRateOfChangeAlarmType Defined in Clause 5.8.16.3    
HasComponent Object LimitState   ExclusiveLimitStateMachineType Mandatory

The LimitState is a sub state of the ActiveState and has an IsTrueSubStateOf reference to the ActiveState. The LimitState represents the actual limit that is violated in an instance of ExclusiveLimitAlarmType. When the ActiveState of the AlarmConditionType is inactive the LimitState shall not be available and shall return NULL on read. Any Events that subscribe for fields from the LimitState when the ActiveState is inactive shall return a NULL for these unavailable fields.

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