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5.8 Alarm model ToC Previous Next

5.8.17 Discrete Alarms ToC Previous Next

5.8.17.1 DiscreteAlarmType ToC Model

The DiscreteAlarmType is used to classify Types into Alarm Conditions where the input for the Alarm may take on only a certain number of possible values (e.g. True/False, running/stopped/terminating). The DiscreteAlarmType with sub types defined in this standard is illustrated in Figure 20. It is formally defined in Table 71.

readme_files/image022.png Figure 20 – DiscreteAlarmType Hierarchy

Table 71 – DiscreteAlarmType definition

Attribute Value
BrowseName DiscreteAlarmType
IsAbstract False

Subtype of the AlarmConditionType defined in clause 5.8.2.

References NodeClass BrowseName DataType TypeDefinition Modelling Rule
HasSubtype ObjectType OffNormalAlarmType Defined in Clause 5.8.15    

5.8.17.2 OffNormalAlarmType ToC Model

The OffNormalAlarmType is a specialization of the DiscreteAlarmType intended to represent a discrete Condition that is considered to be not normal. It is formally defined in Table 72. This sub type is usually used to indicate that a discrete value is in an Alarm state, it is active as long as a non-normal value is present.

Table 72 – OffNormalAlarmType Definition

Attribute Value
BrowseName OffNormalAlarmType
IsAbstract False

Subtype of the DiscreteAlarmType defined in clause 5.8.17.1

References NodeClass BrowseName DataType TypeDefinition ModellingRule
HasSubtype ObjectType TripAlarmType Defined in Clause 5.8.17.4    
HasSubtype ObjectType SystemOffNormalAlarmType Defined in Clause 5.8.17.3    
           
HasProperty Variable NormalState NodeId PropertyType Mandatory

The NormalState Property is a Property that points to a Variable which has a value that corresponds to one of the possible values of the Variable pointed to by the InputNode Property where the NormalState Property Variable value is the value that is considered to be the normal state of the Variable pointed to by the InputNode Property. When the value of the Variable referenced by the InputNode Property is not equal to the value of the NormalState Property the Alarm is Active. If this Variable is not in the AddressSpace, a NULL NodeId shall be provided.

5.8.17.3 SystemOffNormalAlarmType ToC Model

This Condition is used by a Server to indicate that an underlying system that is providing Alarm information is having a communication problem and that the Server may have invalid or incomplete Condition state in the Subscription. Its representation in the AddressSpace is formally defined in Table 73.

Table 73 – SystemOffNormalAlarmType definition

Attribute Value
BrowseName SystemOffNormalAlarmType
IsAbstract True
References NodeClass BrowseName DataType TypeDefinition ModellingRule
HasSubtype ObjectType CertificateExpirationAlarmType Defined in Clause 0    
Subtype of the OffNormalAlarmType, i.e. it has HasProperty References to the same Nodes.          

5.8.17.4 TripAlarmType ToC Model

The TripAlarmType is a specialization of the OffNormalAlarmType intended to represent an equipment trip Condition. The Alarm becomes active when the monitored piece of equipment experiences some abnormal fault such as a motor shutting down due to an overload condition. It is formally defined in Table 74. This Type is mainly used for categorization.

Table 74 – TripAlarmType definition

Attribute Value
BrowseName TripAlarmType
IsAbstract False

Subtype of the OffNormalAlarmType defined in clause 5.8.17.2.

References NodeClass BrowseName DataType TypeDefinition Modelling Rule
           

5.8.17.5 InstrumentDiagnosticAlarmType ToC Model

The InstrumentDiagnosticAlarmType is a specialization of the OffNormalAlarmType intended to represent a fault in a field device. The Alarm becomes active when the monitored device experiences a fault such as a sensor failure. It is formally defined in Table 74. This Type is mainly used for categorization.

Table 75 – InstrumentDiagnosticAlarmType definition

Attribute Value
BrowseName InstrumentDiagnosticAlarmType
IsAbstract False

Subtype of the OffNormalAlarmType defined in clause 5.8.17.2.

References NodeClass BrowseName DataType TypeDefinition Modelling Rule
           

5.8.17.6 SystemDiagnosticAlarmType ToC Model

The SystemDiagnosticAlarmType is a specialization of the OffNormalAlarmType intended to represent a fault in a system or sub-system. The Alarm becomes active when the monitored system experiences a fault. It is formally defined in Table 74. This Type is mainly used for categorization.

Table 76 – SystemDiagnosticAlarmType definition

Attribute Value
BrowseName SystemDiagnosticAlarmType
IsAbstract False

Subtype of the OffNormalAlarmType defined in clause 5.8.17.2.

References NodeClass BrowseName DataType TypeDefinition Modelling Rule
           

5.8.17.7 CertificateExpirationAlarmType ToC Model

This SystemOffNormalAlarmType is raised by the Server when the Server’s Certificate is within the ExpirationLimit of expiration. This Alarm automatically returns to normal when the certificate is updated.

Table 77 – CertificateExpirationAlarmType definition

Attribute Value
BrowseName CertificateExpirationAlarmType
IsAbstract False

Subtype of the SystemOffNormalAlarmType defined in clause 5.8.17.3

References NodeClass BrowseName DataType TypeDefinition ModellingRule
HasProperty Variable ExpirationDate DateTime PropertyType Mandatory
HasProperty Variable ExpirationLimit Duration PropertyType Optional
HasProperty Variable CertificateType NodeId PropertyType Mandatory
HasProperty Variable Certificate ByteString PropertyType Mandatory

ExpirationDate is the date and time this certificate will expire.

ExpirationLimit is the time interval before the ExpirationDate at which this Alarm will trigger. This shall be a positive number. If the property is not provided, a default of 2 weeks shall be used.

CertificateType – See OPC 10000-12 for definition of CertificateType.

Certificate is the certificate that is about to expire.

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