Implementing a substation abstraction model
Outside of, but ready for, IEC 61850
Gerrit Dogger
Senior Product and Application Specialist
Cooper Power Systems
gerrit.dogger@cooperindustries.com
Jack Clarkson
Project Leader, Engineering
SaskPower
jclarkson@saskpower.com
Nicholas Dietrick
Engineer-In-Training, Substations
SaskPower
ndietrick@saskpower.com
Philip Tempel
Senior Substations Design Engineer
SaskPower
ptempel@saskpower.com
Sukhbir Sachdev
Senior Substations Design Engineer
SaskPower
ssachdev@saskpower.com
Abstract
SaskPower, a government-owned utility based in Regina, Saskatchewan, has
started a pilot project to renew their substation control panel design by replacing
the current mechanical switch/indicator design with state-of-the-art HMI control
panels. The project aims at installing a new architecture based on protection
IEDs that still has all the needed flexibility and modularity to accommodate the
traditional interfaces between SaskPower design groups; it must also
demonstrate the ability to incorporate both legacy and new technologies into new
or existing substations.
The selected solution is based on the abstract modeling of the substation
components, including - but not limited to - breakers, transformers, lines, and
buses. These models contain all the required information and logic that help the
creation of links between the IEDs and the local HMI, in addition to creating
groups that match SaskPower’s existing standards for SCADA and local alarm
interfaces. The initial stage of the pilot project included specifying the models
(with their required data items), the data naming standard, and the model internal
behavior.
Modeling substation equipment as logical devices has multiple advantages: the
resulting architecture is IED-independent; different protection schemes can be
implemented, so that single and dual protection is supported while still having
only one logical device instance for higher level actors to work with; data from
different IEDs or I/O modules can be combined easily for additional generated
data.
Another advantage of the standardized logical devices is perceived at the local
HMI level. Based on the abstract models, the single line diagrams and reports
use standardized objects that simplify the operational processes of the local HMI
operators.
As all substations share the same models, subsequent installations will require
less engineering effort and cost while at the same time providing a flexible
implementation.
SaskPower is aware of the industry trend towards IEC 61850; the abstract
models will give SaskPower the opportunity to easily integrate IEC 61850-based
IEDs or to implement an IEC 61850 substation proxy server based on these
models. Furthermore, abstract models created serve as a bridge between
SaskPower’s legacy functional paths and the newest object model, IEC 61850.
The first substation based on this architecture was energized in autumn 2010,
and will be followed by the energization of two other substations during spring
and summer 2011.
This white paper and presentation explore in detail this substation modeling, as
well as the issues and challenges that were encountered and solved for the first
substation.
Introduction
The primary role of the local HMI system is to provide safe, secure, and reliable
control and monitoring of transmission and distribution substations.
Historically, SaskPower’s local HMI was a panel interface using analog meters, a
single line diagram with hardwired lamps and switches, and a PLC-based
annunciator.
The remote interface from SCADA is done through an RTU. The protection
relays have no connectivity with the remote control system, except some
hardwired I/O and alarms to the RTU.
Even though this solution has proven itself, SaskPower wanted to optimize the
use of the installed protection IEDs. The new local HMI should communicate with
the IEDs for data acquisition and control. Small I/O modules are used for some
generic I/O that is not related to the IEDs.
As with other utilities SaskPower favored the separation of the data concentration
and the HMI functionality. SaskPower selected Cooper Power Systems’
SMP Gateway for data concentration, and Cooper’s Substation Processor with
Yukon Visual T&D as the HMI platform.
During the initial meetings on the architecture, SaskPower indicated that
protection IEDs in different protection schemes would be used. Some breakers
would have an A-B protection scheme, while others would just have a single
protection IED. At the same time, standard objects should be developed for the
local HMI to represent the switchyard equipment; these standard objects would
contain status, control, alarm, and SaskPower-specific alarm groups as
attributes.
The first substation to have the new system installed is a new transmission
station called Yellowhead. There, the system monitors and controls the
switchyard equipment used to connect the power plant to the SaskPower grid.
Standard Communication Architecture
The new system uses a data concentrator to communicate with all the IEDs and
IO modules. The new system makes use - where possible - of Ethernet links to
gain speed and to simplify the communication wiring between devices. The HMI
system will then connect to the data concentrator to obtain the gathered data.
The Yellowhead communication architecture is depicted in the underneath figure.
Com2
HMI – A Server/
client
HMI-B Client
Backup server
SMP GATEWAY
Com1
11B1/800B
11B1/808B
11S-1/803
11S-1/808
11S-1/809
11S-1/810
11L-2/807L
11L-1/807L
11L-2/809L
YH_87B1_0800$
YH_87B1_0808$
YH_11S1_0803$
YH_11S1_0808$
YH_11S1_0809$
YH_11S1_0810$
YH_11L1_0807$
YH_11L2_0807$
YH_11L1_0809$
YH_11L2_0809$
YH01$
YH02$
ABB REB670
ABB REB670
ABB REC670
ABB REC670
ABB REC670
ABB REC670
ABB RED670
SIEMENS 7SD52
ABB RED670
SIEMENS 7SD52
11L-1/809L
SMP I/O 1
COOPER IO
SMP I/O 2
COOPER IO
Title:
Yellowhead
Communication Architecture
Drawn by:
Gerrit Dogger
Designed by:
Gerrit Dogger
Drawing No:
Approved by:
Project:
Rev:
1.0
Yellowhead SAS
Energy Automation Solutions
Page:
1 of 3
The same communication architecture will be used in the next substations. In the
Yellowhead substation, the IEDs are using DNP3 to communicate with the data
concentrator; in the next substation, this might change to IEC 61850.
As the data concentrator solution is new to SaskPower, the Yellowhead station
still uses a RTU for SCADA communication. As with existing systems, there is
only some hardwired status contacts to check for device failures and other
alarms.
Abstraction model solution
As most utilities, SaskPower has its own naming convention to label all the data
points in the substation RTU and local alarm system. The naming convention will
group the data per switchyard device within the RTU. This works fine in a RTU
that does not obtain redundant additional data from the protection IEDs.
However, data is duplicated in the data concentrator, as multiple IEDs might be
reporting the same data such as the breaker status or bus voltages. Also, data
concentrators are IED-oriented and not switchyard-oriented.
The solution to this problem was found in creating an intermediate layer of data.
Within this layer, the data is organized based on switchyard apparatus, like
breakers, switches and transformers.
Local HMI
Data concentrator
Logical Breaker
model
Protection
IED A
master
Protection
IED B
master
General I/O
Master
The created abstracted models are generic enough to cover all different types of
switchgear. For example, the logical breaker model will contain alarms for SF6
breakers, as well as alarms for oil breakers. Data that is not applicable will be set
to FALSE or to a predefined analog value.
The abstraction model will increase the separation between the apparatus data,
and the communication protocols and IEDs. There are two advantages to this
approach: SaskPower has more flexibility in the selection of IEDs, as the model
will hide the IEDs; and configuration by a remote agent (be it SCADA, datamining, or even a local system) becomes easier, as the logical device data is
always the same entity.
Logical model - internal logic
Depending on the available data from the IEDs, different functions are used to
map the data from the IED masters to the logical device data map. For example,
the breaker status will use the status reported by IED A when the quality is fine. If
the quality becomes bad (because of a communication error, for example), the
status will be taken from IED B. The local HMI client will not notice any difference
as the logical breaker status never changed value.
While most of the data points in the logical devices will be a direct copy of the
reported data from the IEDs, it is also possible to do additional calculations, such
as scaling or the calculation of values resulting from the acquisition data, such as
power or reactive power.
Furthermore, SaskPower wanted the possibility to locally enable or disable local
alarm groups on the HMI, for commissioning purposes. This additional data is
added to the logical model, and binary logic is used to combine the enable
indications to the local alarm group point. A part of the logical breaker model is
depicted below. The closed and open statuses are based on the best value from
A and B. The breaker fail alarm is a logical OR of both incoming IED data points,
and it can be enabled with the ALARM_ENABLE point. The measured currents
are only available from IED A and a scaling is applied.
For switchyard equipment without any incoming data, such as manual switches,
abstraction models with only internal points were created. The operator can now
match the physical state by simply performing a logical open/close control
operation.
If needed, advanced logic for the logical devices can be implemented using the
IEC 61131-3 SoftPLC available in the gateway.
General station model
Besides the abstraction models for the switchyard equipment, additional models
were defined for:
• Station power transformer
• Station battery
•
Station general for other signals related to general substation functionality
In the Yellowhead station, only the Station general model was needed. This
object handles, for example, the station alarms to drive the alarm buzzer and the
alarm grouping for local and SCADA alarms that are not associated with specific
switchyard devices. Even though there is no link to the SCADA system through
the data concentrator at Yellowhead, the model includes the SCADA alarm
groups for future use or in other substations.
Abstraction model naming versus IED master naming
During the design phase, Cooper Power Systems’ personnel worked closely with
SaskPower to establish the naming convention for the abstraction models. As
these models are the interface to the local HMI, the data point naming convention
is based on SaskPower’s existing naming convention. The idea to base the
naming on the IEC 61850 standard was rejected as this naming is unknown to
operating, maintenance and commissioning staff.
As for the data naming of the IED data, it was decided to use the data naming as
indicated by the IED manufacturer. Within the prefix, the type of device is
indicated, like 11L1 for the primary line protection IED.
By using the abstraction models, it is now possible to have a point name close to
the IED documentation for easy identification by the protection engineer; at the
same time, the SCADA engineer can also easily find his way in the data point list
by linking SCADA targets to logical points.
Complete abstraction model
The complete implementation for Yellowhead is drawn below. The lower part
shows all the masters gathering the data from the IEDs and I/O modules; the
upper part displays all the created logical models, while the DATA MAPPING
ellipse represents the logic that links the master data and the logical models
together.
Displaying the data
For the single-line diagram on the local HMI, a library of standard objects was
created based on the logical models. From this library, a single-line diagram can
easily and quickly be created, as the engineer only needs to insert the required
object on the diagram and to name it properly; the internal logic will then link the
object to the correct data. Below are some screenshots of the single-line
diagram.
Main single-line diagram
Breaker control dialog box
Breaker alarm dialog box
The breaker alarm dialog box is created to show all logical device alarms. Alarms
that are not applicable to the specific breaker are set to False, so no alarm will be
raised. In all cases, the dialog box will be the same.
Conclusion
The aim of the abstraction model in the data concentrator was to implement a
uniform model of available substation equipment, so that different substations
could be implemented easily.
The most important work was the definition of the models. During this task, the
engineers of SaskPower and Cooper Power Systems worked closely together.
SaskPower staff’s knowledge of what the models should do, combined with
Cooper Power Systems’ expertise resulted in a well-defined and reusable
abstraction model.
The first substation was installed without any problem, although some minor
adjustments were needed.
The additional configuration effort to link the IED data to the models is
outweighed by the advantages of having standard equipment interfaces. More
time will be saved on subsequent installations.
Next steps
For SaskPower, the next step is to gain more experience with the models during
the installation of the second and third substations. This experience will be used
to finalize the abstraction model and HMI library objects.
At the same time, SaskPower is exploring the option of completely replacing the
RTU by the data concentrator. In this case, SaskPower’s main SCADA will link to
the data concentrator for data acquisition and remote control. The focus of the
local HMI system will then change from being only a local HMI to becoming a
Substation Automation System with more emphasis on redundancy and NERCCIP requirements.
Another avenue to explore is the use of an IEC 61850 server in the data
concentrator. In this case, the switchyard abstraction model will then serve as the
input for the server.