Chapter10
DLMS/COSEM/OBIS/IDIS
The events are logged in the event log usually as objects.
Definition
The standard, how all the data (not only events) are organized in the smart meters provides the DLMS/COSEM set of standard. DLMS stands for Device Language Message Specification and COSEM for COmpanion Specification for Energy Metering.
Interesting
The DLMS User Association maintains a set of four main specification documents:
  • Blue Book - describes the COSEM meter object model and the OBIS (OBjectIdentificationSystem) – which assigns logical names to the COSEM objects. OBIS is specified in the IEC 62056-61
  • Green Book - describes the architecture and protocols
  • Yellow Book – describes conformance testing
  • White Book - contains the glossary of terms.
Interesting
OBIS codes identify data using a hierarchical structure with dot notation and six groups of values in the form: A-B:C.D.E*F. There are 4 different separators present (“-“, “:”,”.”,*) to support group identification in case that only sub-identifier is preset.
Note
This is often this is three-group sub-identifier such as “1.8.0”, it maps to C.D.E). More detailed descriptions of the groups are:
  • A – defines media (energy type), e.g. 0=abstract, 1=electricity, 5=cooling, 6=heat,7=gas, 8=cold water, 9=hot water, …
  • B – identifies the measurement channel by number
  • C- identifies abstract or physical data, such as current, voltage, power, … for given channel, e.g. 1= positive active power, 2= negative active power, 11=current, 12=voltage, 99=Abstract data profiles (if A=0), or Electricity data profile (if A=1)
  • D – identifies the type of data processing result, e.g. 3=minimum, 6=maximum, 8=time integral
  • E – identifies further processing, if A=1 then e.g. 0=total, 1=rate (tariff) 1, 2=rate (tariff) 2, but e.g. if C= 11 or 12 the meaning of E changes ot 0=total, 1=1st harmonics, 120=120th harmonics, 124=Total Harmonic Distortion (THD)
  • F - identifies historical data
Example
Table 1. Example explanations of selected OBIS codes are presented in the table.
OBIS code
Explanation
1.8.0
Positive active energy (A+) total [kWh]
1.8.1
Positive active energy (A+) in tariff T1 [kWh]
2.8.0
Negative active energy (A+) total [kWh]
2.8.1
Negative active energy (A+) in tariff T1 [kWh]
99.98.x
Event log
99.1.x
Load profile with recording period 1
99.2.x
Load profile with recording period 2
Note: “x” means any value within the valid range 0-255
In the table we see more examples of profiles, that are objects that are used to hold series of measurements (objects) of one or similar quantities and/or to group various data. For basic measurements the recording period is usually set to 15 min and DSO company fetches it once a day.
Note
In addition to mentioned standards describing DLMS/COSEM and OBIS, there is a great help of IDIS (Interoperable Device Interface Specification) Association, which aims to reach pan-European interoperability. Supports various use cases such as automatic meter registration, remote tariff programming, disconnection and reconnection of electricity supply, system wide clock synchronization, demand/load management, remote firmware update.
Example
For example, IDIS specifies in more detail event code classification such as:
  • event code 7: Replace battery - Battery has reached expected end of lifetime and must be replaced
  • event code 40: Meter cover removed – Indicates, that meter cover has been removed.