wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

IEC 61850 for Distributed Energy Resources 59-3
Table 59.1
Logical Node
LPHD
LLNO
DPVC
XCBR
ZINV
XSWI
CSWI
MMTR
Description of the Logical Nodes Classes
Description
Describes the object for the control of a physical
device, which is the microcontroller itself
Describes the object for a logical device
Describes the object for the photovoltaic array
Describes the object for the DC circuit breaker
Describes the object for the inverter
Describes the object for the AC switch
Describes the controller for the operation of the
AC switch
Describes the object for the electric meter
• An AC-switch
• A three-phase circuit breaker and
• An electric meter
For the integration of such a system into a communication network, a microcontroller is required.
According to the IEC 61850 this computer is named as Intelligent Electronic Device (IED). The IEC
61850 provides standardized object classes to describe the information produced and consumed by the
automation functions of such an IED. The most important object classes are the logical node (LN) classes.
For the example shown in Figure 59.2 the Table 59.1 presents the logical node classes that were used.
The communication services required in an IED is described in a communication model by the
so-called ACSI-services (ACSI—abstract communications service interface) defined in IEC 61850-7-2.
These abstract services must be implemented using existing concrete communication protocols
(SCSM—specific communication service mappings). At this stage of the standard, this mapping may be
realized with Ethernet, TCP/IP, and MMS protocols.
59.3 Modeling the Automation Functions
In general, the automation functions in electrical power grids can be classified into three categories:
• Protection functions prevent hazard to people, damage to power network components, and breakdown
of the power grid. Such functions have to be performed within 10 ms.
• Monitoring functions supervise the status of devices and primary equipment (circuit breakers,
transformers, etc.) within the power grid.
• Control functions allow a local or remote operation of the devices.
These automation functions can be divided into subfunctions and functional elements. For modeling
the automation functions in the communication model, objects are standardized on the level of the
functional elements. They are named as LN. The LNs can be grouped to logical devices (LD).
An example of how LNs are built is shown in Figure 59.2. The LN CSWI1 is used in the example presented
in Figure 59.2 in conjunction with XSWI1 for the control of the AC-switch. The corresponding
LN-class CSWI consists of data objects (DO) that have standardized common data classes (CDC). As
an example, the data object Pos (shown circled in Figure 59.3), has the CDC controllable double point
(DPC). Each CDC contains a series of data attributes. As an example, the data attributes corresponding
to data class DPC are shown in Figure 59.4. Some of this data attributes are mandatory, some are
optional, and some can be mandatory or optional if certain conditions are fulfilled.
In our example, the data attributes corresponding to the LN CSWI1 are used to operate the switch
while the LN XSWI1 is used to model the information received from the switch. The IED accesses
the switch through binary inputs/outputs. Firstly, an operate command is sent from a client to the
© 2011 by Taylor and Francis Group, LLC