TOPOLOGICAL INTERLOCKING OF OPERATIONAL SWITCHING
I. A. Golovinskii,1 M. Yu. D’yachenko,2 M. I. Londer,3 and A. V. Tumakov3
Translated from Gidrotekhnicheskoe Stroitel’svo, No. 7, July 2018, pp. 29 – 37.
Positions of interconnected switching devices determine the topological interlocks of switching operations at
substations. The paper reviews two approaches for implementing programmable topological interlocks:
offline and online. The paper highlights the disadvantages of offline and flexibility of online solutions. A new
object-topology approach to modeling of electrical networks is described. It allows applying the standard rules
of topological interlocking automatically, both offline and online. An example of such automation is provided.
Keywords: operational dispatch management; switching control; interlocking of switching operations; topo-
logical interlocking; digital substation; switching diagram topology analysis; object-topology approach.
Interlocking of operational switching at substations is
one of the most important means of ensuring reliability,
safety and accident-free real-time control of electrical net-
works. Interlocking prevents operations, which can cause ac-
cidents or lead to a dangerous decrease in reliability of the
electrical network operating mode, as well as result in health
problems in people.
Most often, to interlock an operation means to eliminate
a physical possibility of performing such operation, which is
achieved by activating a special interlocking device. Such in-
terlocking devices can be called hardware or automatic inter-
locks.
At the same time, the technology of operational switch-
ing within electrical networks imposes a number of prohibi-
tive rules, which are not implemented in the hardware. These
rules are listed in the regulatory technical documents con-
cerning real-time operations control [1 – 5]. They are exe-
cuted by the operating and dispatching personnel when mak-
ing decisions on whether the considered operation can be al-
lowed. Such prohibitive rules are called logical interlocks.
Based on the technological content, interlocks can be di-
vided into switching and performance interlocks. The former
are defined by the position of the interconnected switching
devices (SD) and circuit configuration, and can also be re-
ferred to as topological. The latter depend on the electrical
mode parameters.
The interlocking requirements for SD switching opera-
tions, which are defined by standard switching procedures
and standards, are not tied to specific substation devices.
They are of generalized nature. These are the standard in-
terlocking rules. Along with them, individual interlocking
rules are used, which are related to specific devices. An indi-
vidual interlocking rule can be a logical customization of a
standard rule, but can also be introduced independently of
the standard rules to supplement them as dictated by the local
conditions.
When applied to a specific switching operation, the stan-
dard interlocking rule is subject to customization. It repre-
sents a logical conclusion of the individual interlocking rule
after it has been customized from the standard rule. This con-
clusion can be derived mentally by a person, or logically by a
logic device.
Hardware (automatic) interlocks in principle are more re-
liable than logical. Ideally, all interlocks acting as logical
should be implemented as hardware. Currently, the hardware
implementation of interlocks means that they have to be pro-
grammed into controllers and computers.
Offline and online solutions for interlocking switch-
ing operations. There are two approaches to algorithmiza-
tion of the solutions related to interlocking of operations:
offline and online. When using an offline approach, the inter-
locking solution is not generated at the moment when it is re-
quired, once the switching command is issued, but ahead of
time. For each operation subject to control, all actual combi-
nations of switching and other device conditions should be
considered in advance. For each such combination, a de-
cision of whether to allow or deny an operation is selected.
The decision is saved in the controller or computer memory.
To configure and store a variety of such decisions, special
decision tables are used [6]. When the personnel enters a
command for operational switching, a ready interlocking
Power Technology and Engineering Vol. 52, No. 5, January, 2019
605
1570-145X�19�5205-0605 © 2019 Springer Science+Business Media, LLC
1 North-Caucasus Federal University, Stavropol, Russia;
2 JSC “IMPEDANCE”, Stavropol Territory, Kislovodsk, Russia.
3 JSC “IMPEDANCE”, Moscow, Russia.
DOI 10.1007/s10749-019-01000-4
decision is automatically retrieved from the decision table
and executed.
Traditional hardware interlocks (mechanical, electrome-
chanical, electromagnetic) represent one type of offline inter-
locks.
When utilizing an online approach, interlocking decision
are not generated in advance. Situation analysis and decision
making are conducted upon entering commands by the per-
sonnel. In case of topological interlocks, decision making co-
mes down to analyzing a current circuit configuration graph.
Each of the two approaches have their own advantages
determining which one of them is the most preferable for a
specific situation. For topological interlocks, an offline ap-
proach is useful when the number of interlocking or permit-
ting configurations of the circuit is low.
Let us use a very simple example to analyze offline inter-
locking of closing an earthing switch depending on the posi-
tion of two adjacent disconnectors (Fig. 1a). In this example,
a number of options, which must be considered in order
to completely describe all the interlocking decisions, is equal
to four. This is determined by the fact that each disconnector
can be in one of the following two positions — “closed” or
“open.” In order to implement such interlocking in a pro-
grammable controller, it makes sense to create a one-time
description of these four options and save it in the form of
a decision table (Fig. 1b). All possible combinations of the
D1 and D2 positions are shown in the first two lines of the
decision table. These are the “controlling” elements. The
open disconnector position is designated as 0, and closed po-
sition — as 1. In the third line, symbol “+” indicates a per-
mission to close an open earthing switch ES, and symbol “–”
indicates that such opening is prohibited. Here, ES represents
a “controlled” element.
A decision table for interlocking switching operations of
a switching device (controlled element) is configured in a
similar manner for any switching diagram containing any
number of controlling elements subject to switching. As-
suming that N is the number of controlling elements subject
to switching on the diagram, the complete decision table for
interlocking a controlled element should contain N + 2 rows
and 2N + 1 columns. The first column contains the element
names. All columns, except for the first one, will contain
in the first N lines different combinations of the positions
of the controlling elements. For each such combination, the
last two elements in the column will express the interlocking
decisions with respect to opening and closing of the con-
trolled element. Symbol “+” will indicate a permission to
switch, and symbol “–” will indicate that such switching
is prohibited.
A decision table can be created only for the “opening”
operation with respect to controlled SD (as shown in the ex-
ample in Fig. 1b), or just for the “turning off” operation. In
this case, it will contain N + 1 lines, and only the last line
will contain the decision symbols (“+” and “–”). In such ta-
ble, it is enough to show only those columns which represent
switching permission options, i.e. contain the “+” sign in the
last line. Then, any missing combination of the controlling
element positions will be interpreted as prohibitive. Or vice
versa, it is possible to show only prohibiting combinations in
the table, in which case the missing combinations will imply
a permission to switch. A method containing the lesser num-
ber of combinations is considered more favorable.
If the number of permitting and prohibiting combinations
in the decision table is equally high, the use of such Table is
unproductive. Another major disadvantage of the decision ta-
bles is their lack of transferability and invariance relative to
the circuit topology. Generally speaking, one standard inter-
locking rule produces different decision tables for different
circuits. For example, the standard interlocking rule for clos-
ing a busbar earthing switch in absence of the visible circuit
breaking by open disconnectors produces a decision table for
busbar BB1 of the switchgear (Fig. 2), which cannot be ap-
plied to any other switchgear. Such disadvantage of the deci-
sion tables cannot be eliminated in principle.
But the decision tables simply represent a way to record
the offline interlock-related decisions. Therefore, the appli-
cability of the offline approach is not universal.
The online approach is free of the disadvantages typical
for offline approach, however its implementation requires a
special mathematical tool to analyze the topology of the
switching diagrams. Such tool is equally suitable for both,
online topological interlocking and automated creation of the
offline decision tables relative to topological interlocking.
Developments in the field of topological interlocking.
The requirements concerning implementation of operational
interlocking in programmable controllers are stated in the
document entitled “Operational interlocking organization
procedure at new generation substations” [2]. Specifically, it
is established that permission of the switching operation of a
switching device must be generated “by using logic algo-
rithms programmed into controllers according to the logic of
conventional relay-contact circuits” (clause 3.1.6.1).
Majority of the programmable interlock developers com-
ply with this requirement by utilizing a computer simulation
of relay-contact circuits [7, 8]. Using of LD (Ladder Dia-
gram) programming language helps realizing this approach.
This is a graphic language of the relay-contact circuits em-
bodied in the form of “ladders” enclosed one into another.
Same as the decision tables, interlocking programs in LD
606 I. A. Golovinskii et al.
P1P1
P2
P2
ES
ES
a
b
Fig. 1. Connection between earthing switch and two disconnectors
(a) and decision table for interlocking the opening of the earthing
switch (b).
language are not invariant relative to circuit topology. The
decision tables are mathematically based on Boolean alge-
bra, and LD programs — on the theory of relay-contact cir-
cuits. The fundamentals of these methods were developed in
the second half of the 1930s by A. Nakashima, K. E. Shan-
non and V. I. Shestakov [9]. Boolean algebra was applied to
creating contact circuits of hardware interlocks for the first
time in 1940 by an engineer from Leningrad V. A. Rosenberg
[10].
It is possible to overcome the disadvantages of the above
approaches only by using the methods directly operating the
circuit topology of electrical networks and substations. The
first topological method for analyzing contact circuits was
developed in the second half of the 1940s at the Leningrad
Electrotechnical Institute (LETI) by B. I. Aranovich and A.
G. Lunts [11 – 15]. This method utilized the algebra of
Boolean matrices as its mathematical tool. However, this
method did not find application in electrical network opera-
tions control systems.
Standard topological interlocks were implemented for
the first time in the operational switching simulator devel-
oped in the 1980s at the All-Union Electric Power Research
Institute (VNIIE) [16]. For this purpose, a query language of
the graph-type database management system was used.
Revealing a mathematical structure of the graph analysis
algorithms used in the simulator led to the development of
algebraic methods of analyzing circuit topology, including
those for interlocking solutions [17 – 19]. A special algebra
of graphs was developed, which is briefly described below.
Based on its software implementation, topological interlock-
ing of operational switching was developed by DECIMA in
the form of SCADA�EMS KOTMI-14 software package
[20].
Figure 3 shows a portion of the tested electrical network
diagram (green — 500 kV equipment, red — 220 kV equip-
ment, blue — 110 kV equipment; closed switches are filled
with green, and open switches are filled with red).
The topological interlocking KOTMI-14 software ana-
lyzes the incoming command to open the switch S-10 at the
Zapadnaya substation (SS). This switch is marked with
dashed red contour. Prior to this, switch S-11 was opened at
the Zapadnaya substation. The diagram displays the message
generated by the situation analysis program.
The program has checked the interlocking rules designed
to prevent the following three technological faults, which
may occur as a result of switch opening:
— consumer blackout;
— disturbance of (auto)transformer switching sequence;
— top-down network division based on the voltage rat-
ings.
The program has detected that the first technological
fault does not occur: none of the network nodes lose voltage
as a result of opening switch S-10. The second fault does not
occur either: transformers at Zapadnaya substation (voltage
fed from the lower-voltage side) do not lose voltage from the
higher-voltage side upon opening switch S-10. Only the third
of the possible faults is detected: in case of opening switch
S-11, the connection between Zapadnaya substation and
Prirechnaya State District Power Plant (SDPP) will be inter-
rupted along the 500 kV line, while the connection between
them via a 220 kV network through Petrovskaya and Velinka
substations will still remain. As can be seen from Fig. 3,
Topological Interlocking of Operational Switching 607
TVr1
VTrD1
ES1
BBD11
BBS1 220 kV
BBD12 BBD13
BBS2 220 kV
BBSD1
BBD14 BBD15
Fig. 2. Example of a switchgear diagram illustrating topological interlocking.
there is an additional bypass of the part of the 220 kV net-
work via a 110 kV network through Tsentralnaya substation,
Central Heating and Power Plant CHPP-1 and Osinskaya
substation. This configuration is dangerous in the way that
the total capacity of the lines rated for voltage below 500 kV
can be insufficient for providing a power overflow from
Prirechnaya SDPP to Zapadnaya substation.
Object-topology modeling of electrical network. In or-
der to model and analyze the electrical circuits in KOTMI-14
software package, a new conceptual approach was used. It is
based on the synthesis of object-oriented modeling and to-
pology processor [21].
An object-oriented model of the subject domain, such as
electrical network, is created. Objects of this model form a
system of classes. Object associations represent binary rela-
tions between the classes. Then, a non-oriented graph is cre-
ated, the vertices of which represent one-to-one model
objects, while edges represent associations between the ob-
jects (Fig. 4). This graph is subject to analysis by means of
the topology processor.
Such model of subject domain is called a graph-object
or object-topology model, or also an “objects-associations”
model. We call the system of methodical, mathematical and
software tools, used to create and analyze such model, a
graph-object simulation.
If subject domain is an electrical network, then the ob-
ject-oriented model of its detailed switching diagram can be
created, for example, by using CIM (Common Information
Model) class objects. Developing interlocking solutions gen-
erally requires analysis of the condition of the detailed
608 I. A. Golovinskii et al.
Fig. 3. Automatic detection of dangerous operation in SCADA�EMS KOTMI-14: top-down division of network upon switch opening.
switching diagram considering the position of all SDs. The
object-topology model required for this purpose is created
based on the CIM profile formed by the following classes:
ConductingEquipment — main current-conducting de-
vices of the electrical network: power lines, power trans-
formers, sections of busbars, shunt reactors, switches,
disconnectors, etc.;
ConnectivityNode — connection points between adja-
cent devices;
Terminal — device connection points; these are used to
describe relations between objects of the ConnectivityNode
and ConductingEquipment classes.
Definitions of these classes are provided by the standard
in [22].
Figure 5 shows a fragment of the object-topology model
of the detailed switching diagram created from the objects of
these classes. The left column on this diagram is occupied by
the ConductingEquipment class objects. This class is basic
for a number of the specialized subclasses describing spe-
cific types of current-conducting devices. When implement-
ing a specific model, such devices must be described as ob-
jects of such specialized subclasses: switch — as a Breaker
class object, disconnector — as a Disconnector class object,
transformer — as a PowerTransformer class object, etc.
Each object of the Terminal class is related by means of
associations with one object of the ConductingEquipment
class, and one object of the ConnectivityNode class.
The diagram analysis for topological interlocking is of-
ten limited by the boundaries of a substation or even switch-
gear. In case of the interlocks used in case of the power line
switching, the analysis involves two substations connected
by this power line. When interlocking the switching opera-
tion of switches, the analysis can cover an extensive portion
of the electrical network. In this case, for simplification pur-
poses, instead of detailed switching model, a generalized one
should be used. For example, a graph portion of the model
intended for calculating electrical modes can be used.
Calculation of sets and graphs in object-topology
model. Solution of the majority of problems associated with
topological analysis of electrical circuits can be centered
around a set of a small number of operations with graphs.
When applying a standard rule of topological interlocking, it
needs to be customized. Such customization usually comes
down to combining the following operations with non-ori-
ented graphs:
A + B — union of graphs A and B;
A& B — intersection of graphs A and B;
A – B — difference of graphs A and B;
A * B — increment of graph A by graph B;
A ^ B — closure of graph A by graph B. (1)
Operation A ^ B is defined as a union of graph A with all
connected components of graph B having a nonempty inter-
section with graph A. This operation allows calculating the
“distant” electrical connections between the circuit nodes.
To calculate the “close” connections, operation A * B is used.
Its definition is as follows: graph A * B is a union of a
non-oriented graph A with all those edges of a non-oriented
graph B, in which at least one end belongs to graph A. Spe-
cifically, a union of graph A with edge e is understood as a
union of graph A with the graph actually consisting of the
edge e and two of its ends.
The result of performing each of the operations (1) is
again a non-oriented graph. Due to this, operations can be
combined, while composing formulas of different complex-
ity. As a result, topological interlocking solutions come
down to calculating graphs.
Topological Interlocking of Operational Switching 609
Ob
je
ct
s
Ob
je
ct
s
Associations
Associations
Associations
Class P Class Q Class ... Class X
Fig. 4. Object-topology model of subject domain.
Switch
Disconnector
Transformer
Fig. 5. Fragment of the detailed object-topology model of the elec-
trical network based on CIM classes.
Symbols of the basic operations (1) were chosen based
on the fact that they can be “re-loaded” (re-defined) in C++
programming language. This, perhaps, is the easiest way to
program them. Decima has developed a library of programs
performing operations (1) [23].
The use of operations (1) allows concisely expressing the
solution of, for example, the following problem. Let S repre-
sent a set of graph nodes of the diagram, which represent the
sources, and let P represent a set of nodes, which represent
consumers. Find the set of consumers under voltage. The tar-
get set is expressed by the formula:
(S ^ G) & P. (2)
Figure 6 shows the example of graph G, part of the verti-
ces of which constitutes a set of sources S (red circles), and
another part constitutes a set of consumers P (blue circles).
Graph G contains a marked subgraph S ^^ G (its edges and
also vertices not belonging to sets S and P are shown in red);
and the remaining edges and vertices of graph G not belong-
ing to sets S and P are shown in black. Subgraph S ^^ G rep-
resents a union of those connected components of graph G,
which contain at least one vertex from set S. These compo-
nents include those and only those vertices contained by the
set of consumers P, which are connected with the sources.
The set of such consumers is expressed by formula (2).
Example of using a graph-object approach to algo-
rithmization of standard topological interlocking. The ac-
tion logic of the operational interlocking of switching opera-
tions relative to switching devices is strictly defined by the
regulatory technical documents. The completeness and clar-
ity of these requirements provide basis for attempting to au-
tomate the creation of the interlocking algorithms of SD
switching based on the given primary circuit diagrams. This
problem is formulated, for example, in [24]. Approaches to
solving this problem are suggested in [7, 8]. However, an ex-
haustive procedure for finding a solution of this problem was
already published in [17, 18]. It is based on the described al-
gebra of graphs, which allows creating algorithms that are in-
dependent on the topology of the primary circuit diagrams.
Size restrictions of the paper prevent us from demon-
strating all the possibilities of graph-object calculations for
algorithmization of topological interlocking with the due
completeness. Let us provide just a single example of finding
an interlocking solution, which is invariant with respect to
the diagram topology. It can be applied both offline, and
online.
Let us consider a problem of interlocking the opening of
an earthing switch while the disconnectors connected to it
are in the closed position. Standard interlocking rules pro-
hibit the closing of the earthing knives (if it is not intended
for grounding a neutral) within the section of the circuit,
which is not isolated by the open disconnectors from all di-
rections, from where the voltage can be supplied [2 – 5]. The
circle of open disconnectors forms a “visible break” around
the grounded section.
We will explain the solution by using earthing switch
ES1 as an example in the switchgear circuit (Fig. 2). In this
switchgear, the voltage can be supplied to ES1 from the
220 kV busbar system BBS1, as well as the voltage trans-
former VTr1, if it is not disconnected from the secondary cir-
cuit side. To create a visible break around ES1, it is necessary
to open the following elements: busbar disconnectors
BBD11, BBD12, BBD13, BBD14, BBD15; disconnector of
the busbar connecting switch BBSD1; and also a disconnec-
tor of the voltage transformer VTrD1.
A detailed object-topology model of the switchgear
shown in Fig. 2 needs to be created.
For this purpose, we will be using CIM classes. Let us
denote the graph of this model as G. The vertices of this
graph will represent the objects of the CIM classes, and the
edges will represent the associations between the objects.
Figure 7 shows a fragment of this graph-object model. It
contains the object ES1 and other objects associated with it,
which must be considered in the interlocking solution related
to opening ES1.
610 I. A. Golovinskii et al.
Fig. 6. Finding consumers connected with sources.
VTrD1
ES1
ES1
BBS1 220 kV
BBSD1
BBD1
BBD2
BBD3
BBD4
BBD5
Fig. 7. Object-topography model of the connection between
earthing switch ES1, disconnectors and busbar system in the switch-
gear diagram shown in Fig. 2.
The vertices of graph G represent the objects of CIM
classes shown in the form of blocks. The same color blocks
represent the objects related to the same CIM class. Classes
Disconnector, GroundDisconnector, BusbarSection, and
Ground are subclasses of the class ConductingEquipment.
Green circles represent the Terminal class objects. The
dashed lines show associations between the objects belong-
ing to the shown fragment and the objects outside of it. Fig-
ure 8a shows this graph in more compact form.
If the substation equipment and device connections are
described in the relational database, it becomes possible to
retrieve the sets of devices of a certain type, which exist at a
substation (busbar sections, power transformers, switches,
disconnectors, etc.) by means of inquiries compiled using
SQL language. This does not contradict the use of the CIM
model.
Let us find in the database a set of all disconnectors of
the considered switchgear. Let D represent the set of all verti-
ces of graph G representing disconnectors. Let us also desig-
nate the vertex of graph G representing a given earthing
switch ES1 as z.
The vertices of graph G representing disconnectors,
which must be opened, form a ring around vertex z. We need
to find this ring. It can be easily calculated by using graph
operations (1).
Let us subtract set D from graph G. Figure 8b shows the
result of subtracting set D (as a graph) from graph G. When
subtracting a vertex, all graph edges, which are incidental to-
wards this vertex, are removed.
Graph G – D represents a set of portions of the substation
diagram, which are separated by disconnectors. Let us desig-
nate the portion that contains vertex z (ES1) as S. It is shown
in Fig. 8c and can be expressed by the formula:
S = z ^ (G – D).
The increment operation S * G adds to graph S all the
edges of graph G, in which at least one end belongs to graph
S. The result of this operation is shown in Fig. 8d. A ring of
disconnectors has been added to graph S, which isolates S
from the remaining portion of graph G. Let us designate this
ring as R. It represents a set of disconnectors that we had to
find. This ring can be obtained by subtracting graph S from
graph S * G:
R = (S * G) – S.
The result of this subtraction is shown in Fig. 8e.
Although for illustration of the described algorithm we
used the switchgear diagram shown in Fig. 2, we did not use
in the algorithm any topological features of this diagram dis-
tinguishing it from other switchgear diagrams. The algorithm
is applicable not only to busbar earthing switches, but gener-
ally to any switches. The only condition associated with the
specifics of the diagram is that graph G must invariably in-
clude all disconnectors having an effect on interlocking the
opening of this earthing switch. If this is not a power line
earthing switch, then it is sufficient for graph G to only rep-
resent the switchgear, to which this earthing switch belongs.
Otherwise, graph G must contain a power line and both
switchgears at two substations, which are connected by this
power line. Accordingly, D should then denote the set of all
disconnectors at both substations.
The described simple graph calculations can be per-
formed either offline, or online. In both cases, they provide a
customized interlocking rule, which lists all disconnectors
which must be opened to provide a visible break. In the
offline mode, these calculations are only performed once for
each earthing switch, and the obtained customized rule is
saved to the knowledge base. On the other hand, the online
calculation are performed every time when exercising con-
trol of a command for closing of any earthing switch.
Readers familiar with the conventional methods of pro-
gramming the switching interlocks, can easily see how much
simpler the proposed method of graph calculations is. Other
standard rules of topological interlocking may require more
complex calculations. But regardless, this approach certainly
provides more simple algorithms compared to the conven-
tionally used methods of Boolean algebra and relay-contact
circuits.
CONCLUSIONS
1. Operational switching interlocks in the electrical net-
works should include not only the hardware (automatic) in-
terlocks, but also the rules prohibiting switching operations
Topological Interlocking of Operational Switching 611
BBD11
BBD11
BBD11
BBD12
BBD12
BBD12
BBD13
BBD13
BBD13
BBD14
BBD14
BBD14
BBD15
BBD15
BBD15
VTrD1
VTrD1
VTrD1
ES1
ES1
ES1
ES1
BBS1
BBS1
BBS1
BBS1
BBSD1
BBSD1
BBSD1
a b
c
d
e
Fig. 8. Graph calculations when interlocking the opening of the
earthing switch.
of the switching devices, which result from the requirements
of the regulatory technical documents concerning real-time
operations control. These standard interlocking rules are not
associated with any specific equipment and must be custom-
ized when applied to a switching device subject to switching.
2. Topological interlocks are defined by the condition of
the interconnected switching devices. In this paper, two ap-
proaches for implementing the standard topological inter-
locks are considered — offline and online. When offline ap-
proach is used, the interlocking decisions are generated one
time outside of the real-time control loop, then saved to the
memory of the control system and applied once the com-
mand for switching of a corresponding switching device is
issued. The online interlocking solutions are generated auto-
matically once the command for switching of a correspond-
ing switching device is received.
For certain standard rules of topological interlocking, the
offline implementation is either inefficient, or practically im-
possible. The offline approach cannot be applied at all times,
while the online approach is universal and is based on auto-
matic customization of the standard rules of topological in-
terlocking by analyzing the electrical network model.
3. The implementation of programmable controllers at
substations and transitioning to programmable interlocks
have expanded the capabilities of hardware interlocking
quite significantly. However, in practice, stereotypic ap-
proaches are still being used during the design process,
which are based on decision tables or simulation of the re-
lay-contact circuits. Such methods have certain disadvan-
tages, including the need for sorting through all possible
combinations of SD positions, as well as general inability to
transfer interlocking algorithms from one diagram to another
having a different topology.
4. This paper describes the topological interlocking
algorithmization procedure based on a new simulation
method associated with the object-topology (graph-object)
approach. The latter consists in analyzing the topology of the
graphs describing the structure of the object-oriented model
of subject domain. The object-topology approach allows
overcoming the disadvantages of the conventional methods
of topological interlock programming. The typical interlock-
ing solution algorithms, resulting from using such approach,
are independent of the specific topological features of a spe-
cific substation. They are equally applicable offline and on-
line. The paper offers an example of such algorithm.
5. The object-topology approach provides a natural for-
malization of the standard topological interlocking. In the
object-topology model, images of the diagrams mentally
navigated by a person are replaced with corresponding
graphs, and verbal definitions of the switching configura-
tions are replaced with mathematical formulas. Based on
these formulas, switching characteristics of the circuits are
calculated, which determine the interlocking solutions. As a
result, logical reasoning performed by a person when making
interlock-related decisions is replaced by calculating graphs.
6. With regards to the simulated switching modes, such
as testing the switching formats and automated simula-
tor-based control of operating and dispatching personnel, in-
terlocking is carried out by using computer models of electri-
cal networks. The object-topology approach allows for a sig-
nificant reduction in simulation costs due to the use of
mathematical models of standard interlocking. As a result, a
labor-consuming process of creating a number of individual
interlocking models is eliminated.
7. The object-topology approach is in-line with the CIM
principles and complies with the IEC 61968 and IEC 61970
standards. It was used to implement topological interlocking
into the SCADA�EMS KOTMI-14 software package. The
practical experience provides evidence showing that the ap-
plication of such approach simplifies the development of
topological interlocking and improves its reliability.
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Topological Interlocking of Operational Switching 613