Common Data Classes (CDC)

Basics

Common data classes (CDC) are structured variables defined in the IEC 61850-7-3. They are the building blocks for the definition of logical node and as such the basis for the data model.

There is a limited amount of CDC that IEC 61850 is defining in the IEC 61850-7-3. Since Edition 2 CDC cannot be extended. This means that any logical node but also any user-defined extension of a logical node is a composition of a limited set of common data classes.

Short	Long

Short	Long
SPS	Single Point Status
DPS	Double Point Status
INS	Integer Status
ENS	Enumeration Status
ACT	Protection activation information
ACD	Directional protections activation status
SEC	Security violation status
BCR	Binary counter reading
HST	Histogram
VSS	Visible string status
ORG	Object reference status
TCS	Time value status
MV	Measured Value
CMV	Complex Measured Value
SAV	Sampled value
WYE	Phase to ground related measured values of a three phase system
DEL	Phase to phase related measured value of a three phase system
SEQ	Sequence
HMV	Harmonic value
HWYE	Harmonic value for WYE
HDEL	Harminic value for DEL
SPC	Controlable single point
DPC	Controllable double point
INC	Controllable integer
ENC	Controllable enumeration
BSC	Binary controllable step position information
ISC	Integer controllable step down information
APC	Controllable analogue process value
BAC	Binary controllable analogue process value
DPL	Device name plate
LPL	Logical node name plate
CSD	Curve shape description
VSD	Visible string description

Each common data class in the IEC 61850-7-3 has a table describing the structure variable.

A CDC consists of data attributes (attributes name). Those can be basic types as defined in the IEC 61850-7-2 or can be structured types again. It is important to note that not each of the data attributes is mandatory (PresCond = M). Next to mandatory attribute, a CDC can have optional attributes or conditional attributes.

Although CDCs are defined by the standard, their implementation highly depends on users choices, because of optional and conditional attributes.

Modelling in SCL

In the SCL these CDC are implemented in two different ways:

The basic structure is implemented in the `DataTypeTemplates` section

Here the SCL elements DOType, DAType and EnumType are used to model the structured variable.

Example 1 (SPS - Single Point Status):

<DOType cdc="SPS" id="...">
  <DA name="stVal" bType="BOOLEAN" dchg="true" fc="ST" />
  <DA name="q" bType="Quality" qchg="true" fc="ST" />
  <DA name="t" bType="Timestamp" fc="ST" />
</DOType>

Example 2 (WYE - Phase to ground related measured values of a three phase system):

Used to model three pahse current or voltage measurement.

<DOType cdc="WYE" id="...">
  <SDO name="phsA" type="typeCMV"/>
  <SDO name="phsB" type="typeCMV"/>
  <SDO name="phsC" type="typeCMV"/>
  ...
</DOType>
...
<DOType cdc="CMV" id="typeCMV">
  <DA name="cVal" bType="Struct" dchg="true" dupd="true" fc="MX" type="vector" />
  <DA name="q" bType="Quality" fc="MX" />
  <DA name="t" bType="Timestamp" fc="MX" />
</DOType>
<DAType id="vector">
  <BDA name="mag" bType="Struct" type="AnalogueValue" />
  <BDA name="ang" bType="Struct" type="AnalogueValue" />
</DAType>
<DAType name="AnalogueValue">
  <BDA name="f" bType="FLOAT32" />
</DAType>

The second example is more complex as it consists of another CDC (CMV) and structure data attributes Vactor and AnalogueValue.

The IED section

Example 1 (SPS):

<DOI name="..." >
  <DAI name="stVal" >
    ...
  </DAI>
</DOI>

Example 2 (WYE):

Common Data Classes (CDC)

Basics

Modelling in SCL

The basic structure is implemented in the DataTypeTemplates section

The IED section

The basic structure is implemented in the `DataTypeTemplates` section