CHAPTER-10
DESIGN OF EHVAND UHV SUB-STTAION
10.1
Introduction
Large hydro-electric generating stations at remote feasible sites are being planned. Transmission at
EHV/UHV level may be required providing for heavy transmission ties for bulk loads transfer from remote
generating stations. Special considerations are involved in designing such substation for selection of single
line diagram, switching schemes and busbar arrangements, electrical clearances to be adopted and layout of
equipment in the switchyard. Shielding of control cables and other special problems in the design of
EHV/UHV substations are also briefly outlined. The discussion covers the step-up substation at generating
stations, step-down stations at load ends as well as switching stations sometimes necessary for paralleling
long EHV/UHV lines. Discussions are made with special reference to EHV substations of Beas Project.
10.2
Switching Schemes for EHV Substations
10.2.1
Types of Substations
EHV substations may be sub-divided into three types (Figure 10.1) as given below:
i)
ii)
iii)
10.2.2
Step-up substation at generation end
Transformer substation at load ends of the system
Switching substations located along the lines to parallel them.
Criteria for the selection
Major considerations for the selection of a suitable switching scheme for an EHV and
are given below:
i)
ii)
iii)
iv)
v)
UHV sub-station
The scheme should fit in the planning criteria used to design the connected transmission system. System
should be stable if a permanent fault occurs on a line. It is, therefore, important to limit as much as possible
the system un-stability caused by outage of line, transformer or generators due to sub-station faults.
Repair or maintenance of the equipment should be possible without interruption of power supply.
Expansion of sub-station should be easily possible.
Large clearances are required at EHV and UHV level. Therefore in order to obtain lower structures and
facilitate maintenance it is also important to design sub-stations, preferably with not more than two levels
of bus bar.
Practical site consideration at a particular location e.g. lack of adequate flat area for layout of equipment in
the sub-station may also sometimes influence the choice of layout. The switching schemes suitable for each
type of sub-station are discussed below.
Based on paper by Author in 44th Annual Research Session of Central Board of Irrigation & Power (1975)
Step-up Substations: Step-up substations at generation ends may have unit connected transformers or else
EHV transformers may be used to step-up the power from bus-bars at lower voltage in the switchyards of
generating stations. The later type of substation is similar to the transformer step-down substation at load
ends and will be discussed along with that type.
For generating units connected directly to their step-up transformers, discussions are made with special
reference to Dehar Power Plant of Beas Project where six units each of 165 MW are being installed and 4
units will be directly connected to their step-up 420 kV transformers. The other two units are connected to
245 kV system through unit connected transformer. An interlinking transformer 245/420 kV was proposed.
Main single line diagram is shown in figure 10.8.
437
GEN.
INTERLINKUNG
TRANSFORMER
1
1
STEU-UP SUB-STATION
2
SWITCHING SUB-STATION
3
TRANSFORMER SUB-STATION
2
3
Figure 10.1: Types of Substation
Figure 10.2 to Figure 10.5 show the single line diagram, plan views and elevation (one circuit only) for four
different schemes which were considered for this substation for 420 kV portion:
i)
ii)
iii)
A double bus single breaker scheme as shown in Figure 10.2 (scheme 1).
A single bus (sectionalized) with two generating units and one outgoing transmission line
connected to each bus section as shown in figure 10.3 (scheme 2).
A double bus one and a half breaker scheme, figure 10.4 (scheme 3).
438
iv)
v)
10.2.3
Incoming lines from generator transformers, connected to two 420 kV buses by single breakers.
The outgoing lines connected by two breakers to both the buses. The scheme corresponds to a
single sectionalized bus for incoming lines and a two bus two breaker scheme for outgoing lines,
figure 10.5 (scheme 4).
Other schemes ring bus and double bus double breaker schemes were not considered due to lack of
space and costs.
Discussion for Selection of Bus Scheme for Dehar Step-up Substation
Forced Outage of Generator-Transformer Unit: In all the schemes capacity equal to one unit is lost when a
generator transformer unit is forced out.
Bus Section Fault :Generating capacity to the extent of four units (660 MW) may be forced out under
certain conditions in case of a fault on 420 kV bus under scheme (1) Figure 10.2. Outage of this large bulk
of power amounting to about 22 percent of the maximum demand (3000 MW approximately) at that time
may cause frequency dips which may trip generating units, loads and inter-regional tie lines by the
operation of under frequency relays if installed and may upset system stability and was, therefore, not
considered desirable.
In schemes (2) Figure 10.3 and (4) Figure10.5 maximum power forced out will be to the extent of 2 units
(330 MW) while in case of scheme (3) Figure 10.4 circuit breaker connected with the bus will trip but
normally no outage of generating capacity will be caused.
Figure 10.2: 420 kV Double Bus Single Breaker Scheme Substation Layout
(Source: CBIP Paper by Author)
439
Figure 10.3: 420 kV Single Bus Single Breaker Scheme Substation Layout
(Source: CBIP Paper by Author)
440
Figure 10.4: 400 kV One and a Half Breaker Scheme Substation Layout
(Source: CBIP Paper by Author)
441
Figure 10.5: 420 kV Two Bus Two Breaker Scheme for outgoing Feeder and Single Breaker for Incoming
Two Generators
(Source: CBIP Paper by Author)
442
Transmission Line Outages: No power generating capacity is required to be shut down in case of a fault on 245 kV
line (245 kV Bus) while in case of fault on 420 kV feeder (during the first stage of operation) power generation to
the extent of about one unit may have to be shut down so as to achieve stability.
In case of a bus section or circuit breaker fault there is a forced outage of 420 kV transmission line under schemes
(1) Figure 10.2 and scheme (2) Figure 10.3. It is possible to re-energise the line through bus coupler in case of
scheme (1) but not so in scheme (2) Figure 10.3.
In scheme (2) figure 10.3, for carrying out maintenance of the 420 kV feeder breaker, the transmission line has to be
forced out.
In scheme (3) figure 10.4 when one of the generators is shut down, the advantage of second breaker for 420 kV line
is lost as only one breaker will be controlling the transmission line.
In scheme (4) figure 10.5 under first stage of operation when a 420 kV line is out due to line fault, power generation
to the extent of one unit (165 MW) is automatically switched off and gives stability to the system even in case of
limited rotating reserve available.
In view of the above discussions, scheme (1) figure 10.2 and (2) figure 10.3 were found to be unsuitable to our
requirements and were left out from further considerations.
Other Considerations for Adopting Scheme (4) (figure 10.5)
a)
b)
c)
d)
e)
Requirement of space for switchyard under scheme (4) figure 10.5 will be much less than that for scheme (3)
figure 10.4.
Requirement of control cables for relaying and inter-locking will be less for scheme (4) figure 10.5.
Switching operations for isolating a breaker or a bus section for maintenance in case of a fault are less under
scheme (4) figure 10.5.
Two levels of busbars are possible in a substation of this type by placing circuit breakers outside the busbars
(figure 10.5).
Number of breakers required for scheme (4) figure 10.5 are less as compared to scheme (3) figure 10.4.
Transformer Substations: For transformer substations at the generating end or the load end, a single breaker double
bus, a double breaker double bus (figure 10.6), a one and a half breaker (figure 10.4) or a ring bus (figure 10.7)
schemes can be considered.
However, only later three schemes generally meet the service continuity criteria.
443
Figure 10.6: 400 kV Double Bus Double Breaker Scheme Substation Layout
(Source: CBIP Paper by Author)
Figure 10.7: 420 kV Ring Bus Scheme Substation Layout
(Source: CBIP Paper by Author)
444
Ring bus scheme requires only one breaker per circuit and is most economical. It is quite common in
Canada and has been utilized in a slightly modified from for EHV/UHV system of Hydro-Quebec and that
of Peace River Systems in USA. In simple ring bus scheme provision of protection becomes more
complicated if number of circuits increase to more than six and its scope gets, therefore restricted. From the
point of view of future expansion of the sub-station, one and a half breaker scheme and double breaker
scheme is more suitable. Former requires lesser number of breakers and isolators and has been
Figure 10.8: Main Single Line Diagram (Dehar Power Plant) (As Designed)proposed for the ultimate
stage of receiving end transformers substation at Panipat. Initially, i.e. till more than 6 bays are required in
the substation, layout shall be that for one and a half breaker scheme but shall be operated in ring bus with
omission of some breakers and isolators and jumper connections of two circuits to the bus bars.
Single line diagram for Dehar Hydro Power Station is at Figure 10.8.
10.2.4
Switching Station
For a switching station all single line diagrams (sophisticated or otherwise) with only one busbar for
paralleling two or more lines figure 10.3 must be rejected because a fault on this bus or on any equipment
connected to it would put more than one line out of service.
Neither ring-bus nor one-and –a half breaker scheme meet the criteria for a switching station, because a
fault on one circuit breaker can cause two lines to be lost.
For a sub-station with incoming and outgoing lines, the double –breaker scheme (Figure 10.6) is the only
one that ensures the service continuity required by the criteria.
To construct this kind of substation with only two levels of busbras, the circuit breakers are placed outside
the busbars.
445
10.2.5
Single Line Diagram of a typical receiving end 420 kV Substation with shunt reactor installation is at
Figure 10.9.
10.3
Electrical Clearances for Installing EHV/UHV Equipment In Field
Space requirements and layout of electrical equipment in switchyard depends upon various types of air
clearances required to be provided for laying the equipment of different rated voltages. Following basic
clearances govern the sub-station design.
(i)
(ii)
(iii)
Earth clearance i.e. phase to ground clearance.
Phase clearance i.e. phase to phase clearance.
Safety clearance i.e.
(a)
Ground clearance.
(b)
Section clearance.
Initial designs of substations are based on the air clearances worked out in accordance with the then recent
CIGRE Study Committee Report which provides a correlation between the insulation levels and the
minimum air clearances to ground and between phases. Tentative clearances for Dehar and Panipat 420 kV
substations were, however, based on the similar test data as available earlier.
For transmission systems of nominal system voltage below 300 kV sub-station clearances is governed only
by lightning impulse over-voltages or BIL of the equipments and bus bars. For transmission system of 300
kV and above, sub-station clearances is mainly governed by internal over voltage i.e. switching impulse
over-voltage and dynamic
420kV
420kV
50MVAR
50MVAR
50MVAR
DETAILS AT A
4x105MVA
M-1
245kV
M-2
T
TRANSFER BUS
4x245kV
420kV SIDE
420kV AUX. BUS
33kV
SPARE
SINGLE
PHASE UNIT
36kV
245kV AUX. BUS
4x25MVAR
245kV SIDE
DETAILS 'A'
Figure 10.9: Single Line Diagram of a Typical 420 kV Substation
(Source: CBIP Manual on Sub-station)
446
over voltage. In order to reduce clearances and equipment insulation, internal overvoltage including
switching impulse over voltages, have to be limited by using one or two step preinsertion resistors, single
pole reclosing, synchronous closing of breakers, shunt reactors etc (Figure 10.9). The ratio of controlled
switching impulse over voltages to the peak value of highest phase to ground system voltage varies from
2.5 in EHV system to 1.5 in UHV system.
IEC publication 71 defines insulation levels for highest voltages for equipment of 300 kV and above as a
combination of two components. The rated switching impulse withstands voltages and the rated lightning
impulse withstands voltage.
Accordingly the minimum clearances shall be the higher of the following and the section clearance will
then be based on it.
i)
ii)
10.3.1
Minimum clearance from the consideration of the lightning insulation levels to be
adopted for the sub-station equipment.
Minimum clearance computed from switching surge requirements.
Minimum Phase to Ground Clearances
Clearances are discussed with special reference to 420 kV, based on the data available at the time of design.
For higher voltage i.e. 525 kV and 765 kV level substation similar considerations can be applied based on
the data available at the time of design.
Insulation Levels and Withstand phase to ground Air Clearances
Standard insulation levels for the highest voltage of 420 kV and above as per IS: 2165-1977 and IEC
recommendation are given in Table 10.1. In this voltage range the performance of insulation and ground
clearances are based on phase to phase switching impulse unless specifically required otherwise. Phase to
ground clearance for switching over-voltages in EHV range may be estimated using the following formula.
d 0.6 =
Uw
500 K (1 − 1.3σ )
Where, d is the clearance in meters Uw is the switching impulse withstand voltage in kV, K is the gap factor
characterizing the shape of electrodes and σ is the standard deviation equal to 0.6 for switching impulse
tests.
For the types of electrodes existing in sub-station design it is possible to associate a value of phase-toground air clearance to each value of rated switching or lightning impulse withstand voltage. the requisite
phase to ground clearance for switching and lightning impulse over voltages can be determined using the
above formulae and graphs given in the CIGRE Committee report. It is seen that impulse withstand voltage
of an air gap depends also on the shape of the electrodes and has been designated as gap factor K in the
committee report. The gap factor ‘K’ depends upon electrodes configuration and is influenced by
geometrical dimensions of the gap, including the grounded surroundings configuration are given in table
10.2.
10.3.2
Minimum Phase to Ground Clearances for various Insulation Levels
Sub-stations show mainly three types of phase to ground clearances.
i)
ii)
iii)
Distances between conductors and beam.
Distances between live parts of apparatus and beams.
Distance between conductor and ground.
447
The electrode configuration found for the first type of clearances is clearly identified, and can be regarded
as being of the “conductor structure”, type, associated with a value of about 1.30 for the gap factor k. As
regards the second type of air clearances, it is very difficult to identify a precise electrode configuration and
the value of K is varying between 1.10 and 1.30. Gap factor k=1.10 is characteristic for a configuration
similar to rod-structure, e.g. open disconnecting switches near structures. Gap factor k=1.30 corresponds to
the conductor-structure configuration, e.g. closed disconnecting switches near structures.
As regards the third type of air clearances, “conductor-ground” configurations, normally the clearances are
sufficiently high because bus-bar conductors are supported by metal supports and post insulators. In every
case, this configuration is covered by the gap factor 1.10.
Table 10.3 gives the correlation between the various combinations of insulation levels shown in Table 10.1
and corresponding to k-=1.10 and 1.30 the minimum air clearances which are the highest values for each
combination, calculated either for the switching or lightning impulse level. This table does not take into
account the possibility/ electrodes getting closer together e.g. because of short circuit or wind.
Minimum values of phase to earth clearances as per IS 3716-1978 based on switching impulse withstand is
given in table 10.3. These values may be used for first approximation.
Table – 10.1
Highest
voltage for
equipment
Um
kV
Base for
pu values
Um
kV
2
Rated switching
impulse
withstand
voltage (peak)
Rated lightning
impulse withstand
voltage (peak)
3
p.u.
kV
kV
1.11
1.24
1050
1175
950
2.76
420
Ratio between
lightning and
switching impulse
withstand voltages
1.12
343
3.06
1050
1.24
1300
1.12
2.45
525
1.36
429
1.21
2.74
765
625
1175
1425
1.10
2.08
2.28
2.48
Table-10.2
Electrode Configurations
Rod Plane
Rod-Structure (Under)
Conductor Plane
Conductor Window
Conductor Strcuture (Under)
Rod-rod (h-3 m, under)
Conductor struicture (over and laterally)
Rod-rod ( h – 6m, under)
448
K
1.00
1.05
1.15
1.25
1.30
1.30
1.35
1.30
Conductor-rope
Conductor crossarm end
Conductor – rod (h = 3m; under)
Conductor – rod (h = 6m; under)
Conductor rod (over)
1.40
1.65
1.65
1.90
1.90
Table-10.3
Insulation Level
Rated Switching
Impulse withstand
voltage (kV)
1050
1050
1175
1175
1175
1300
10.3.3
Minimum phase-to-Ground Air
Clearance (m)
K=1.30
K=1.10
Rated lightning impulse withstand
voltage (kV)
1300
1425
1300
1425
1550
1425
2.55
2.60
3.07
3.07
3.07
3.64
3.36
3.36
4.06
4.06
4.06
4.80
Phase-to-Ground Clearances for Dehar Sub-station
Lightning impulse level of 1425 kV with a corresponding basic switching impulse level of 1175 for power
transformers for Dehar 420 kV E.H.V. system was proposed for first stage installations. Lightning
insulation level for circuit breakers and other apparatus connected to the bus bars with the b us bars
themselves was proposed for Beas Project as for insulation class about 10% higher i.e. 1550 kV. Minimum
phase to ground air clearances for Beas Project sub-stations for initial designs based upon test data
previously available and according to procedure outlined is given in table 10.4.
Table 10.4
Clearance in meters
calculated as per
latest data
Adopted
3.07
3.50
3.07
to 4.06
4.06
3.50 or
more
9.0
3.90
5.2
5.9
-
4.7
6.07
6.7
5.5 to 7.0
-
7.00
(Meters)
(a) Minimum Phase to Ground Clearance
(i)
(ii)
(iii)
Conductors and Beams
Line parts of apparatus and beams.
Conductor and ground
(b) Minimum Phase to Phase Clearance
(ii) Minimum Rigid Bars Spacing
(iii) Minimum strain Bus bars spacing
(iv) Phase to Phase Spacing for
equipment
(v) Minimum spacing between 2 sets of
bus bars
10.4
SAFETY CLEARANCES
Safety clearance consists of ground clearance and section clearance. The ground clearance is the minimum
clearance from any point on or about the permanent equipment where a man may be required to stand
(measured from the position of feet) to the nearest part not at earth potential of an insulator supporting a
line conductor and the same was taken as 2.59 m, which is the dimension for a tall man with arms
outstretched below the conductor.
449
The section clearance is the minimum clearance from any point on or about the permanent equipment
where a man may be required to stand (measured from the position of feet) to the nearest unscreened live
conductor in air. The section clearance for 420 kV systems was determined as 6 m by adding 2.5 m to
minimum phase-to-ground clearance of 3.5 m.
10.4.1
Height of bus bars above ground within sub-station premises
The minimum conductor clearance from ground was obtained by adding ground clearance, earth clearance
(2.59 meters height of a tall man with outstretched hands) and height of bus bar supporting clamps on the
post insulator. In consideration to it, minimum height of bus bar was proposed to be 7.0 meters, which may
be raised to 9.5 meters to correspond to the terminal height of 420 kV circuit breakers (Air blast circuit
breakers). SF6 breakers are now used.
10.4.2
Conductor clearance from roadways within sub-station premises
Minimum clearance between over-head conductors and roadways within sub-station premises was
computed to be as “Ground Clearance plus 6.25 meters. This dimension provides for a truck with a man
standing on its top 4.05 + 6.25 meters = 10.30 meters.
10.5
PHASE TO PHASE CLEARANCES
10.5.1
Insulation levels
Phase to phase faults cause severe system disturbances and are, therefore, least desirable. As such phase
spacing adopted should be such as to cause flashover to ground instead of phase-to-phase. For this purpose
distance between phases is made to exceed that to ground to the extent that flashover can occur only to
ground. The distance between systems e.g. between two bays are not only determined by their electrical
strength the but also by necessity to carry out maintenance work.
Lightning surge stresses between phases will normally not be higher than the lightning surge stresses to
ground. Therefore, minimum phase to phase spacing are governed by switching impulse withstand voltage.
Owing to the fact that phase-to-phase over-voltage peak is subjected to considerable variations, depending
upon the following:
(i)
(ii)
The waves shape (time to crest) of the phase-to ground switching over voltages having opposite
polarity on adjacent phases.
The ratio and time delay between these two components.
It is possible to determine a ratio P between the maximum overvoltage between phases and the maximum
overvoltage to ground only by means of TNA or field measurements.
The theoretical maximum value of P is equal to 2, provided that the two-phase-ground components have
opposite polarity and synchronous peak values equal to maximum overvoltage to ground. In practice,
however, P will be lower because these conditions are not fulfilled. According to a number of TNA and
field measurements the control of the over voltages to ground increases the ratio P; the higher the control,
the higher the value of P,
The ratio P = 1.66 to 1.7 of the rated switching impulse withstand voltage to ground between 1050 and
1175 kV was chosen as this generally leads to conservative values of the clearance. With this factor P and
according to the standardized IEC values for the impulse levels, the switching impulse withstand voltage
between phases start-over characteristics of ring-ring and rod-rod gaps is shown in table 10.5, for 420 kV
voltage system.
450
Table 10.5
Rated
Switching
impulse
withstand
voltage to
ground
1050
1175
1300
10.5.2
Ratio
between
phase-to-phase and
phase-to-ground
switching
impulse
withstand voltage
Switching
impulse voltage
between phases
(kV)
1.71
1.66
1.73
1800
1950
2250
50%
switching
impulse flashover
voltage between
phases (kV)
1952
2115
2440
Minimum
phase-tophase air clearance (m)
ring-rod-ring rod.
ring-ring
rod-rod
3.40
3.90
5.20
4.20
4.75
6.20
Phase to Phase Air Clearances
In sub-stations mainly three types of phase to phase air clearances may be present depending upon
electrode configuration:
(i)
(ii)
(iii)
Clearances between conductors
Clearances between conductor and apparatus
Clearances between poles of apparatus
The first type of air clearances is found between the phases of line entrances and bus-bars. Occasionally,
the conductor electrode may be sub substantially modified by hardware. The second type includes the
“conductor-disconnecting switch” air clearances; the third type comprises the “between breaker-poles”,
“between disconnecting switch poles” and “between poles of current transformer” kind of air clearance and
clearances “between line-traps”. In general, the second and third type of air clearances presents electrodes
configurations that are difficult to define.
The rod-rod gap can be assumed to be representative for the practical geometrical conditions in the lower
voltage, range, whilst the ring-ring gap with a given geometrical dimensions may be considered to be
typical for the higher voltage range and be used for first type of air clearance.
Many of the second and third type air clearances (clearances between the poles of apparatus i.e.
disconnecting switches, breakers, etc.) might be considered proper to the apparatus, just as in the case of
phase-to-ground air insulations, even when the apparatus is essentially single phase. The minimum
clearance between phases, assuring a given insulation level, should, in this case, be specified by the
manufacturer and checked by a type test. It is, therefore unnecessary to fix the minimum air clearances
between the poles of apparatus which have the most widely varied electrode configurations.
Table 10.6 gives the recommended minimum clearances between phases for rod-rod and ring-ring
configuration in 420 kV in .E.H.V. range.
Corona shield ring was assumed to have a diameter of 630 mm. Strain bus spacing were obtained by adding
0.7 meters to the spacing for rigid bus as per American practice. Other spacing adopted is shown in figure
10.5.
10.6
ELECTRICAL CLEARANCES FOR INSTALLING EHV/UHV EQUIPMENT AS PER CBI & P
RECOMMENDATIONS
CBI & P manual Entitled “substation layout” stipulates that air clearances for 420 kV and higher voltage
switching over voltages are the governing factor.
For determination of phase-to-ground air clearance, the “rod-structure” configuration is the worst electrode
configuration normally encountered in practice; the “conductor-structure” configuration covers a large
range of normally used configuration. But the necessary inter-phase clearance is more related to the “rodconductor” and “conductor-conductor” configuration. The unsymmetrical “rod-conductor” configuration is
the worst configuration normally encountered in service. The “conductor-conductor” configuration covers
all symmetrical configurations with similar electrode shapes on the two phases.
451
The phase to earth clearances is the higher value of the clearances determined for the rod structure
configuration for the standard lightning impulse and for the standard switching impulse withstands
voltages. The phase to phase clearance is the higher value of the clearances determined for the rod structure
configuration for the standard lightning impulse and for the standard switching impulse withstands
voltages.
The CBI & P recommended values of clearance for substation up to 800 kV is as follows:
Highest
System
Voltage
(kV)
420
10.7
Lightning
impulse
voltage (kVp)
Table 10.6
Switching
Minimum Clearances$
Impulse
Voltage (kVp)
Between phase &
earth (mm)
3400*
6400*
1425
Safety
clearances
(mm)
Between
phase (mm)
4200**
9400**
1050 (Ph-E)
6400
1575 (Ph-Ph)
800
2100
1550 (Ph-E)
10300
2550 (Ph-Ph)
*
Based on Rod-structure air gap.
**
Based on Rod-Conductor air gap.
$
This value of air clearances are the minimum values dictated consideration and do not include any
addition for construction tolerances, effect of short circuits, wind effects and safety of personnel,
etc.
LAYOUT OF EQUIPMENT IN THE SUB-STATION
Layout of equipment for various types of single line diagram is shown in figure 10.2 to figure 10.7. Due to
practical considerations of space etc. the layout tentatively proposed for Dehar Sub-station is shown in
Figure 10.5. The layout of equipment at Panipat was proposed for one and a half breaker scheme.
10.8
SHIELDING OF CONTROL CABLES
In the control cables and the secondary wiring passing through E.H.V. Sub-station dangerous high voltages
are liable to be induced by opening and closing of E.H.V disconnects which may be especially dangerous
for static/numerical relays. Accordingly such cables are required to be properly shielded. One of the power
utility of U.S.A is using unarmoured cables and provides shielding by running heavy grounded conductor at
the top of each cable trench. The portion of control cables in air (outside trenches) is, however shielded by
armouring. Magnetic armouring has been used by C.E.G.B. in U.K. and is being adopted on Beas Project
on the advice of supplier of protective equipment although effectiveness’ of magnetic armouring is reduced
under short circuit conditions and may be examined in due course by site measurements.
452
REFERENCE
1.
Thapar, OD,: “Stability EHV system” CBI & P Annual Reasearch Session, Publication No. 121,
pp. 22-31,June 1973.
2.
R. Prourget “Selecting a single line Diagram” Hydro Quebec Symposium Extra High Voltage and
Ultra High Voltage. October 1973.
3.
R.H. Hill and J.C. Stevens “B.C. Hydro E.H.V. Transmissions System Design and construction
Line and Station”. Maintoba E.H.V. Symposium September, 1966.
4.
L. Paris, A. Taschini, K.H. Schneider and K.H. Weck “Phase-to-Ground and Phase-to-Phase Air
Clearances in Sub-stations” CIGRE No. 29, 1973l; PP 29.45.
5.
A.I.E.E. Committee Report “Interim Report-Minimum Electrical Clearances based on Switching
Surge Requirements” AIEE Vol. PAS 1963 PP.
6.
I.E.E.E. Committee Report “Second Interim Report-Minimum Electrical Clearances Sub-station
based on May 1965, PP 415-417.
7.
I.E.C. Publication 71 – “Insulation Coordination Chapters I & II” 5th Edition.
8.
Thapar, OD, and Saksena, RB,: “Equipment Insulation Coordination in Developing 400 kV EHV
System” 1974 Issues of Power Engineer.
9.
Thapar, OD and Saksena, RB,: “Relaying for 400 kV EHV System” Proceeding CBI & P Annual
Reasearch Session, Publication No. 116.
10.
Howard, J. Sutton: “Transients Induced in Control Cables Located in EHV Substation.” IEEE,
PAS-89, July-August 1970.
11.
Stanlay, H. Horowitz and Harold, T. Seeley: “Relaying the AEP 765 System.” IEEE, PAS July
1969.
12.
Central Board of Irrigation & Power – “Manual on Substations Pub. 299-2006
Appendix 1.1
List of Indian Standards, Guides, Codes etc. required for Reference
Colour for ready mix paints
IS: 5
IS: 13155
Method of test for carbon type (PNA) Analysis of Mineral oils by Infrared (1991)
Spectrophotometer
IS: 375
Marking & arrangement of swgr. bushbars main connections and auxiliary Wiring.
IS: 1367
Hot dip galvanized cooling on threaded fasteners.
IS:
2147
Degree of protection provided by enclosures for low voltage switchgear And control gear.
IS:
3347
Dimensions of porcelain transformer bushings for use in lightly polluted Atmospheres
IS:
3637
Gas operated relays
IS:
3639
Fitting & accessories for Power Transformers
IS:
6272
Industrial cooling fans
IS:
6600
Guide for loading of oil immersed transformers
IS:
8603
Dimensions for porcelain transformer bushing for use in heavily
Polluted atmosphere (36 kV class). Dimensions for oil filled porcelain transformer
bushings for use in medium polluted atmospheres.
IS:
9434
Guide for sampling and analysis of free and dissolved gas in oil filled Atmosphere.
453
IS:
10028
Code of practice for selection, installation and maintenance of transFormer
IS: 335
New insulating oils for transformer (Test procedure)
IS:325
Three-phase induction motors
IS:398(Pt-1)
Aluminium conductors for overhead transmission purposes; Pt 1- Aluminium stranded
conductors
IS: 398(Pt-2)
Aluminium conductors for overhead transmission purposes : Pt.2- Aluminium conductors,
galvanized steel reinforced
IS: 398(Pt-5)
Aluminium conductors - galvanized steel reinforced for extra high voltage (400 kV and
above)
IS: 692
Paper insulated lead sheathed cables for rated voltage up to and including 33 kV specification
IS: 694
PVC insulated cables for working voltages up to and including 1 100 volts.
IS: 731
Porcelain insulators for overhead power lines with a nominal voltage greater than 1000
volts
IS: 802
Use of structural steel in overhead transmission line towers - Code of practices.
IS: 875 (Pt 1-5)
Code of practice for design loads (other than earthquake) for buildings and structures
IS:933
Portable chemical fire extinguisher, foam type
IS:934
Portable chemical fire extinguisher, soda acid type
IS: 11 80
Three-phase distribution transformers up to and including 100 kVA, 11 kV, outdoor type
IS: 1248
Direct acting indicating analogue electrical measuring instruments and their accessories
IS: 1255
Code of practice for installation and maintenance of paper insulated power cables (Up to
and including 33 kV)
IS:1554(Pt-1)
PVC insulated (heavy duty) electric cables Part-1 , for working voltages up to and
including 11 00 volts
18:1 554 (Pt-2)
Specification for PVC insulated (heavy duty) electric cables Part-2, for working voltages
from 3.3 kV up to and including 1 1 kV
IS: 1866
Code of practice for maintenance and supervision of mineral insulating oil in equipment
IS: 2026
Power transformer
IS: 2062
Steel for general structural purposes - Specification
IS: 2099
Bushings for alternating voltages above 1 000 volts
IS: 2121
Conductors and earth wire accessories for overhead power lines
IS: 21 65
Insulation coordination
IS: 2190
Code of practice for selection, Installation and maintenance of portable first-aid fire
extinguishers
IS: 2309
Code of practice for protection of buildings and allied structure against lightning
IS: 2486
Insulator fittings for overhead power lines with nominal voltage greater than 1000V
454
IS: 2544
Porcelain post insulators for systems with nominal voltages greater than 1000 volts
IS: 2629
Recommended practice for hot-dip galvanizing of iron and steel
IS: 2633
Methods for testing uniformity of coating of zinc coated articles
IS: 2705
Current transformers
IS: 3034
Code of practice for fire safety of industrial building, electrical generating and distributing
stations
IS:3070(Pt.1)
Lightning arresters for alternating current systems non-linear resistor type lightning arrester
IS: 3070 (Pt.2)
Metal oxide surge arresters without gaps for alternating current systems
IS: 31 51
Earthing transformers
IS: 3156
Voltage transformers
IS: 3716
Application guide for insulation coordination
IS: 4004
Application guide for non-linear resister type surge arresters without series gap for AC
system
IS: 4146
Application guide for voltage transformers
IS: 4201
Application guide for current transformers
IS: 5082
Wrought aluminium and aluminium alloy bars, rods, tubes and sections for electrical
purposes
IS:5216(Pt.1&2)
Guide for safety procedures and practices in electrical work
IS: 5547
Application guide for capacitor voltage transformers
IS:5553(Pt.1&2)
Shunt reactors
IS: 5561
Specifications for electrical power connectors
IS: 5578
Guide for marking of insulated conductors
IS: 6005
Code of practice for phosphating of iron and steel
IS:8437(Pt.1&2)
Guide on effects of currents passing through human body
IS: 9921
Alternating current disconnections (isolators) for voltages above 1000 volt
IS:10028(Pt-1,Pt2&3)
Code of practice for selection, installation and maintenance of transformers
15:10118
Code of practice for selection, installation and maintenance of switchgear and control gear
13:10136
Code of practice for selection of disc insulator fittings for highest system voltages of 72.5
kV and above
13:10162
Spacers and spacer dampers for twin horizontal bundle conductors.
15:10561-
Application guide for power transformers
IS: 12032 (Pt-2)
Graphical symbols used in electro-technology : conductors and connecting device's
IS: 12032(Pt-4)
Graphical symbols used in electro-technology : Passive components
455
IS: 12032(Pt-6)
Graphical symbols used in electro-technology : Production and Conversion of electrical
energy
13:1 2032 (Pt-7)
Graphical symbols used in electro-technology : Switchgear, control gear and protective
devices
IS: 12360
Voltage bands for electrical installations including preferred voltages and frequency
IS: 12063
Classification of degrees of protection provided by enclosures of electrical equipment
IS: 13134
Guide for selection of Insulators in respect of pollution conditions.
1S:13118/IEC: 56
Specification for high voltage AC circuits breakers
IS: 13516
Methods of synthetic testing of high voltage AC circuit breakers
IS: 13947 (Pt.1 to 5)
LV switchgear and control gear
Appendix 1.2
List of IEC Standards
IEC:
60296
Fluids for electromechanical applications – Unused mineral insulating oils
for transformers and switchgear
IEC-60044-4
Instrument Transformers: Measurement of Partial Discharges
IEC-60051 : (P1 to P9)
Recommendations for Direct Acting indicating-analogue electrical
measuring instruments and their accessories.
IEC-60076 (Part 1 to Part 5)
Power Transformers
IEC-60076-10
Determination of Transformer and Reactor Sound Levels
I EC-60099-4 25
Metal oxide surge arresters without gaps
IEC-60129
Alternating Current Disconnectors (Isolators) and Earthing switches
IEC-1129
Alternating Current Earthing Switches Induced Current switching
IEC-60137
Insulated bushings for alternating voltages above 1000 V.
IEC-60168
Tests on indoor and outdoor post insulators of ceramic material or glass
for Systems with Nominal Voltages Greater than 1000 V
IEC-60183
Guide to the Selection of High Voltage Cables
IEC-60214
On-Load Tap-Changers
IEC-60233
Tests on Hollow Insulators for use in electrical equipment.
IEC-60255 (Part 1 to part 23)
Electrical relays
IEC-60265 (Part 1 & Part 2)
High Voltage switches
456
IEC-60273
Characteristics of indoor and outdoor post insulators for systems with
nominal voltages greater than 1000V
IEC-60289
Reactors
IEC IEC-60297 (Pt to P4)
Dimensions of mechanical structures of the 482.6mm (19 inches) series
IEC -60376
Specification and Acceptance of New Sulphur Hexafloride
IEC -60437
Radio Interference Test on High Voltage Insulators
IEC -60507
Artificial Pollution Tests on High Voltage Insulators to be used on AC
Systems
IEC -60694
Common Specification for High Voltage Switchgear & Control gear
Standards
IEC -6081 5
Guide for the Selection of Insulators in respect of Polluted Conditions
IEC -60865 (P1 & P2)
Short Circuit Current - Calculation of effects
IEC - 60354
Loading Guide for Oil - Immersed power transformers
IEC-62271-100
High Voltage Alternating Current Circuit Breakers
IEC -60427
Synthetic Testing of High Voltage alternating current circuit
Breakers
IEC-61264
Pressurized Hollow Column Insulators
IEC-60358
Coupling capacitors and capacitor dividers
IEC-60481
Coupling Devices for power Line Carrier Systems
IEC-60529
Degree of Protection provided by enclosures
I EC-60353
Line traps for A.C. power systems
IEC-60481
Coupling Devices for power line carrier systems
IEC-60495
Single sideboard power line carrier terminals
I EC-60683
Planning of (single Side-Band) power line carrier systems
IEC-60359
Expression of the performance of electrical & electronic measuring
equipment
I EC-60387
Symbols for Alternating-Current Electricity meters
IEC-60447
Man machine interface (MMI) - Actuating principles
IEC-60521
Class 0.5, 1 and 2 alternating current watt hour metres
457
IEC-60547
Modular plug-in Unit and standard 19-inch rack mounting unit based on
NIM Standard (for electronic nuclear instruments)
IEC-60305
Insulators for overhead lines with nominal voltage above 1000 V-ceramic
or glass insulator units for a.c. systems Characteristics of String Insulator
Units of the cap and pintype
IEC-60372(1984)
Locking devices for ball and socket couplings of string insulator units:
dimensions and tests.
IEC-60383 (P1 and P2)
Insulators for overhead lines with a nominal voltage above 1000 V.
IEC-60433
Characteristics of string insulator units of the long rod type
IEC-60471
Dimensions of Clevis and tongue couplings of string insulator units
IEC-60227 (P1 to P7)
Polyvinyl Chloride insulated cables of rated voltages up to and including
450/750V
IEC-60228
Conductors of insulated cables
IEC-60230
Impulse tests on cables and their accessories
IEC-60287 (P1 to P3)
Calculation of the continuous current rating of cables (100% load factor)
IEC-60304
Standard colours for insulation for low-frequency cables and wires
IEC-60332 (P1 to P3)
Tests on electric cables under fire conditions
IEEE:
IEEE standard requirement terminology and test procedure for neutral
Grounding device.
32
458