5.8.24 Discrete Alarms

5.8.24.1 DiscreteAlarmType

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 document is illustrated in Figure 22. It is formally defined in Table 105.

Figure 22 – DiscreteAlarmType Hierarchy
Table 105 – DiscreteAlarmType definition
Attribute Value
BrowseNameDiscreteAlarmType
IsAbstractFalse
References NodeClass BrowseName DataType TypeDefinition Modelling
Rule
Subtype of the AlarmConditionType defined in clause 5.8.2.
HasSubtype ObjectType OffNormalAlarmTypeDefined in Clause 5.8.22
ConformanceUnits
A & C Discrete
5.8.24.2 OffNormalAlarmType

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 106. 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 106 – OffNormalAlarmType definition
Attribute Value
BrowseNameOffNormalAlarmType
IsAbstractFalse
References NodeClass BrowseName DataType TypeDefinition ModellingRule
Subtype of the DiscreteAlarmType defined in clause 5.8.24.1
HasSubtype ObjectType TripAlarmTypeDefined in Clause 5.8.24.4
HasSubtype ObjectType SystemOffNormalAlarmTypeDefined in Clause 5.8.24.3
HasProperty Variable NormalStateNodeIdPropertyTypeMandatory
ConformanceUnits
A & C OffNormal

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.

5.8.24.3 SystemOffNormalAlarmType

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 107.

Table 107 – SystemOffNormalAlarmType definition
Attribute Value
BrowseNameSystemOffNormalAlarmType
IsAbstractFalse
References NodeClass BrowseName DataType TypeDefinition ModellingRule
HasSubtype ObjectType CertificateExpirationAlarmTypeDefined in Clause 5.8.24.7
Subtype of the OffNormalAlarmType, i.e. it has HasProperty References to the same Nodes.
ConformanceUnits
A & C SystemOffNormal
5.8.24.4 TripAlarmType

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 108. This Type is mainly used for categorization.

Table 108 – TripAlarmType definition
Attribute Value
BrowseNameTripAlarmType
IsAbstractFalse
References NodeClass BrowseName DataType TypeDefinition Modelling
Rule
Subtype of the OffNormalAlarmType defined in clause 5.8.24.2.
ConformanceUnits
A & C Trip
5.8.24.5 InstrumentDiagnosticAlarmType

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 108. This Type is mainly used for categorization.

Table 109 – InstrumentDiagnosticAlarmType definition
Attribute Value
BrowseNameInstrumentDiagnosticAlarmType
IsAbstractFalse
References NodeClass BrowseName DataType TypeDefinition Modelling
Rule
Subtype of the OffNormalAlarmType defined in clause 5.8.24.2.
ConformanceUnits
A & C InstrumentDiagnostic
5.8.24.6 SystemDiagnosticAlarmType

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 108. This Type is mainly used for categorization.

Table 110 – SystemDiagnosticAlarmType definition
Attribute Value
BrowseNameSystemDiagnosticAlarmType
IsAbstractFalse
References NodeClass BrowseName DataType TypeDefinition Modelling
Rule
Subtype of the OffNormalAlarmType defined in clause 5.8.24.2.
ConformanceUnits
A & C SystemDiagnostic
5.8.24.7 CertificateExpirationAlarmType

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 111 – CertificateExpirationAlarmType definition
Attribute Value
BrowseNameCertificateExpirationAlarmType
IsAbstractFalse
References NodeClass BrowseName DataType TypeDefinition ModellingRule
Subtype of the SystemOffNormalAlarmType defined in clause 5.8.24.3
HasPropertyVariableExpirationDateDateTimePropertyTypeMandatory
HasPropertyVariableExpirationLimitDurationPropertyTypeOptional
HasPropertyVariableCertificateTypeNodeIdPropertyTypeMandatory
HasPropertyVariableCertificateByteStringPropertyTypeMandatory
ConformanceUnits
A & C CertificateExpiration

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 Part 12 for definition of CertificateType.

Certificate is the certificate that is about to expire.