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Antun Foškulo, dipl.ing.el.
Končar – Power Plant and Electric Traction Engineering Inc.
antun.foskulo@koncar-ket.hr
COMPLETE UTILIZATION OF BAY WIDTH IN A DOUBLE BUSBAR HV SWITCHYARD
OF LOW-RISE (CLASSICAL) LAYOUT
ABSTRACT
Complete utilization of bay width in a double busbar switchyard of low-rise (classical) layout
is achievable by means of adding an additional bay inside the space that was left unused and therefore
empty according to a classical layout. By doing so switchyard area reduction can be achieved meaning
lower cost for the investment.
This article lists conceptual differences between these two layouts by limiting only on primary
equipment types and its position and function. Additional equipment that is necessary for layout
realization is also listed.
Apart from giving graphical illustrations for both concepts some of the basic advantages and
disadvantages are mentioned.
Key words: switchyard, low-rise classical layout, diameter, complete utilization
1.
INTRODUCTION AND OBJECT OF THE ANALYSIS
Usual way for developing double busbar HV switchyards involves installation of HV
equipment inside the bay width while at the same time such bay width is only used for one HV bay
which may be oriented either towards power transformer or towards overhead line. The rest of the
space with the same width is left to be empty and therefore unused. Possible usage of such an empty
space not only does potentially reduce the switchyard area but may also reduce potential investments.
For the purpose of graphical illustrations a 110 kV substation shall be used with its general
layout given inside the figure 1. Orientation equipment alignment and positions were defined inside
the Tender. Investor / Client and its Consultant / Representative leave the possibility of defining and
offering such alternative solutions as long as the orientation of OHLs defined inside the Tender are
respected. Additional requirements for providing space for two future bays were stated of which one
has already prepared infrastructure while for another an extension of busbar system need to be
provided.
Figure 1. Top view of classical low-rise layout
2.
OBJECTIVES
Intention of this article apart from proposing another way for obtaining switchyard area
reduction is to present this concept to a wider audience. Such a concept was detected during the
bidding stage for substations in Iraqi region of Kurdistan and can be viewed upon as a rare concept
since it is not covered or even mentioned inside the manuals provided by leading manufacturers of
electric equipment. Furthermore, such a concept is not even mentioned inside the essential literature
required on faculties when dealing with power engineering.
3.
SOLUTION CONCEPT
3.1
Basis of the solution
In order to reduce switchyard area, using of empty space inside the bay's width is proposed by
means of installing HV equipment that forms another HV bay. Single line diagram representing such a
solution is given by figure 3. while top view of such a solution can be seen on the figure 4.
Figure 2. depicts single line diagram for a classical low-rise layout concept which is fully
consistent with a substation top view that is given as figure 1.
This kind of conceptual solution enables the definition of a diameter (if indeed preferred),
otherwise already known inside the breaker-and-a-half and breaker-and-a-third switchyards.
According to the existent bay types inside the case given by figures 2. and 3., a diameter could be
comprised of the following combinations :
•
•
•
•
Transformer - transformer bay
Transformer – coupling bay
Transformer – OHL bay
Transformer – empty bay
Figure 2. Single line diagram of existing
switchyard concept
•
•
•
•
OHL – OHL bay
OHL – coupling bay
OHL – empty bay
Coupling – empty bay
Figure 3. Single line diagram of
proposed switchyard concept
Empty bays defined just above as empty spaces can be upgraded to become :
•
•
•
Generator bays (is generator exists nearby)
Compensation bays
Metering bays (if they contain disconnectors and are not placed beneath and at the end of
the busbars)
Figure 4. Top view for proposed switchyard consisting of 6 diameters
A diameter that is comprised of just one bay is given by figure 6. while a completely filled diameter
can be seen on the figure 7.
3.2
Conceptual differences
Low-rise (classical) layout for HV switchyard is characterized by the existence of a branch
line which leads toward the circuit breaker and at the same time is risen above the busbar system. For
such a concept to be feasible, high portals are required to be made, [1]. One portal must be placed
between the busbar systems and another one represents outgoing (terminal) portal. This can be seen on
the figure 5.
Figure 5. Top view and side view for a classical low-rise layout
Since the existence of the busbar systems (including the gantry in-between) and a terminal
gantry is not questionable within the new concept, still by comparing it with a classical concept some
differences were detected.
3.2.1
Quantities and types of primary equipment
There are no differences in quantities of primary equipment between these two concepts.
However, differences in primary equipment types are present and are manifested only on busbar
disconnectors. While a classical low-rise layout required the presence of two busbar disconnectors of
parallel type per bay, new concept requires substitution of one parallel disconnector with one line type
disconnector per bay. Such line type disconnector is used to establish collection points on its poles and
for continuation of line towards the circuit breaker. Types for other primary equipment can be left
unchanged.
3.2.2
Position and function of primary equipment at bay level
If we take into account that the primary equipment’s position within the bay are optimized for
both concepts, only difference can be noticed in the position of busbar disconnectors.
Both of busbar disconnectors of parallel type within the classical concept are placed opposite
one another with the busbar centerline in between them and both of them must be moved in one or the
other side of diameter thus losing their function for providing the joint connection point through
connection of their nearer poles. These disconnectors shall serve another purpose by establishing
connection on the same busbar system. Which busbar system they shall connect to depend on their
position (under which busbar system are placed).
Further poles on parallel disconnectors once used for providing connection towards different
busbar systems now are used for providing current connection towards line disconnectors.
Figure 7. OHL bay and transformer bay inside the diameter
Figure 6. One OHL bay inside the diameter
3.2.3
Realization and the function of jointing / suspension equipment
While classical layout involves cambering of only one busbar system, within the proposed
concept cambering of both busbar systems is included and is independent of the number of bays which
are installed within the diameter.
Connection (branch) line between the central portal and the outgoing (terminal) portal inside the
classical concept was uninterrupted thus forming the single circuit. However, new concept proposes
the splitting of the same branch line on two parts by installing the insulator string somewhere in the
middle of the branch line. Same rule applies on the branch line located on the opposite side of the
central gantry.
Both parts of such a divided line in-between connected with the rope of the same cross-section
are enabling the transfer of the voltage from the busbars towards the poles of the line disconnector. By
enabling so, voltage is taken from the busbar system that is not the nearest one. Everything described
and mentioned above is illustrated on the following figure.
Figure 8. Connections to be realized
Connection between the other bay’s disconnector within the diameter can be made by means
of tubular conductors or by rope.
3.2.4
Symmetry of phase conductors
An overall symmetry of phase conductors cannot fully be achieved due to the presence of line
disconnector. Positional variations of phase conductors and the variations in distance between the
phases can be seen on the figure 4. and be visually compared with figures 1. and 5. representing the
classical concept.
Figure 9. Isometric view on an overall switchyard proposed
4.
COMPARISON, ADVANTAGES AND DISADVANTAGES
As any concept has its own advantages and disadvantages, this one is no exception. Some of
the advantages and disadvantages of the proposed concept were detected and are given in the
following text after the comparison. Proposed concept and its impact on a look of a whole substation
can be seen on the figure 9.
4.1
Comparison
For comparison purposes substation dimensions (length and width) are of prime importance
along with the substation area information. Information of secondary importance for comparison can
be defined as high portal columns number and number of spare bays that are available.
Table 1. Table of comparison between two concepts
PARAMETER
CLASSICAL CONCEPT
PROPOSED CONCEPT
DIFFERENCE (%)
Length (m)
Width (m)
Substation area (m2)
No. of high portal columns
No. of spare bays available
184
116
21344
30
2
130,5
117
15268,5
21
3
-29,1%
+0,85%
-28,5%
-30%
+50%
4.2
Concept advantages
Some of the noticed advantages of the proposed concept are:
•
•
•
•
•
4.3
less total substation area
lesser operational substation costs in regards to outdoor lighting due to lesser lamps installed
possible maintain of overhead line continuity regarding the incoming and outgoing OHL bays
(inside the same diameter)
less number of portal columns with their own foundations
higher number of spare bays
Concept disadvantages
Some of the noticed disadvantages of the proposed concept are :
•
•
•
5.
higher switchyard complexity
harder maintenance due to the proximity of installed primary and jointing / suspension
equipment especially when performing tasks in the proximity of live voltage
disparity in range between the phases inside the diameter
CONCLUSION
Presented concept even though more complicated in its concept than the classical one is
feasible and therefore outdoor HV switchyard area can be reduced.
Switchyard area reduction leads towards some other savings, mainly some operational savings
due outdoor lighting, some constructional savings due to the reduced length of earthing system, less
excavations tasks are needed to be performed (either manually or by mechanization) and so on.
Savings based upon the number of gantry columns of high portals and their own foundations
are mainly due to better planning and better alignment.
Additional diameter can deliver two spare bays instead of one what was the case with classical
layout.
6.
[1]
LITERATURE
Požar, H. Visokonaponska rasklopna postrojenja. Zagreb : Tehnička knjiga, 1990.