FIELD OF INVENTION
The present invention relates to a Low Tension Compact Substation (LTSS).
More particularly the present invention discloses a substation, wherein low
voltage electric energy is converted to high-voltage electric energy, so that
distribution and consumption is achieved.
BACK GROUND ART
In the recent power distribution systems there have been recurrent complaints,
in some localities, regarding low-voltage in LT consumers' premises.
General trend of mitigating such issues are by either of the two ways:
i) Installing a new source.
ii) Laying of new MV cables, to reorganize the network.
But such initiatives have bottlenecks. Firstly, the number of affected consumers
must be handful and secondly, the Capital Expenditure is high. So, if the
number of affected consumer is less then undertaking such measure(s) isn't
economically viable.
In line with the applicant's organizational objective of value engineering and
developing cost effective sustainable solutions, keeping consumers at the core
of the affairs, we have developed a device to mitigate low voltage problems.

In a prior art problem, the voltage prior to installing the device was measured at
various premises at the remote end and at the mid span of the network and they
ranged between 180V to 210V. The load of this pocket was found to be around
70 Amp during peak period of the evening and early night hours. Voltage
complaints were related to nonfunctioning of Air conditioners in the night,
slower rotation of fans, fluctuation of TV sets etc.
Before going into the details of the set-up, a brief analysis of the complaint
should be done. During the analysis, low voltage pocket including loading of
the sections need to be carefully carried out, since these parameters are required
for computing the rating of VR as well as rating of capacitor(s). Moreover,
undersized conductor, loose contacts in the joints (/termination) add substantial
resistance to the current flow.
Earlier thoughts were to commission one DTR of capacity 315kVA as shown in
Fig 1, for which it was thought of mooting one Network Scheme. Thus we have
been able to defer the CAPEX if not eliminate the same.
The minimum cost of installing one DTR is around Rs 30 lac whereas the cost
of this device is much less than 1 lac. Hence this has the potential of huge cost
savings by the company.
To address such a situation, a very effective measure, so far, undertaken is
installation of MV AC Compact Sub-Station. Basically it comprises of two
units, a voltage-regulator and a capacitor -bank, installed in a combination or
individually at strategic nodal points, depending upon the loading.
Given below are snapshots of the problems faced in distribution:
OVERLOADING of DTR:
The distribution transformers are designed to operate at a regulation of 3% to
5% generally, under rated condition. When the loading is too high, there is

significant fall in the output voltage, because there will be internal voltage drop
in the series leakage impedance of the transformer, the magnitude of which will
depend upon the degree of loading as well as on the power-factor of the load.
Increase in REACTIVE Power Consumption:
It is known that voltage and reactive power are strongly coupled. So, increase in
inductive loads (motors, fans etc.) increases the reactive power consumption
resulting in an unnecessary loading of distributor and hence a fall in the voltage
level.
Voltage Drops in the Network:
An overloaded system will witness significant voltage-drops in the feeding
networks, which progressively increases towards the furthest connected
consumer(s).
Since the inherent distributed capacitance of O/H lines is less compared to U/G
cables, the line-drop is more in overhead network.
SUMMARY OF INVENTION
Therefore such as herein described there is provided a LTCSS (Low Tension
Compact Substation) which constitutes of a 50kVA 3 phase Dry type Y-Y
variable voltage Auto transformer embedded inside a cubicle and also fitted
with it one Jean Muller make 160A fuse strip unit at the incomer side of the
transformer and one 100A adjustable rating MCCB on the outgoing side of the
transformer.
In an embodiment there is provided heavy duty fans fitted inside the cubicle
which are controlled by a timer for alternatively switching the fans ON & OFF.

We have also fixed one Energy meter in the circuit for measuring & displaying
various electrical parameters of the Transformer load.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
Fig 1 illustrates the prior art installation;
Fig 2 illustrates the auto-transformer working in accordance with the present
invention;
Fig 3 illustrates the 3-phase Delta connected Cap-Bank Arrangement in
accordance with th present invention;
Fig 4(a) illustrates the Voltage Regulator with auto-transformer in accordance
with the present invention;
Fig 4(b) illustrates the CAP-BANK installed on an O/H line in accordance with
th present invention;
DETAILED DESCRIPTION
In the present invention there is discloses a LT transformer substation as shown
in Fig 4, comprises high voltage protective and operating equipment;
transformer and low-tension distribution board. This transformer station
constitutes a modularization compact apparatus and has eliminated the
connection between described parts. The operation of the installation of this
transformer station and distribution is simplified widely by this way, thereby the
electric power accident of this transformer station during installation, operation
and maintenance is minimized. All these are assembled in a module such that
size has been reduced, so the cost of transformer station also is minimized to a
great extent.

The disclosed Low Tension Compact Substation (LTSS) comprising of a
voltage regulator at the point on the distributor where the voltage falls below the
threshold value; a capacitor-bank fitted, at a nodal-point of the said incoming
distributor; a fuse strip unit of 160A rating connected at the incomer side of the
transformer; and an adjustable rating MCCB of 100A rating connected on the
outgoing side of the transformer.
The Modularized compact type of the present invention transformer station
constitutes a specially designed integral body, but form by the identical separate
part that in any transformer station, uses, these parts are called as transformer,
high-tension apparatus and low-tension distribution board, each of these parts
all keeps homogeneity separately respectively, just may remove this high-
pressure installation or low-voltage device by this way, each parts all remains
on intact user mode.Compare with design integral body or integrated, these
characteristic remarkable ground have increased the adaptability of this
transformer station.
LT Compact Substation (LTCSS)
As shown in Fig 2, the disclosed LTCSS (Low Tension Compact Substation)
constitutes of a 50kVA 3 phase Dry type Y-Y variable voltage Auto transformer
embedded inside a cubicle and also fitted with it one Jean Muller make 160A
fuse strip unit at the incomer side of the transformer and one 100A adjustable
rating MCCB on the outgoing side of the transformer.
There are variable taps in the autotransformer to produce output ranged at 7.5%,
15% & 20% of the input voltage. The autotransformer is dry type and the
cooling type is ANAF. There are heavy duty fans fitted inside the cubicle which
are controlled by a timer for alternatively switching the fans ON & OFF. There

is also provided a fixed Energy meter in the circuit for measuring & displaying
various electrical parameters of the Transformer load.
Post installation of this device at a suitable location by connecting the incomer
and outgoing circuits to the overhead mainline through 240 sqmm pole boxes,
the voltage of the area has improved tremendously. Every hourly readings wee
taken for the voltage and load of the outgoing circuit during early & late
evening hours and the average voltage were found to be (R-N-237 to 242V, B-
N-234 to 240V, Y-N-235 to 238V) and the maximum loading observed at
11PM in the evening with the light, Fan & ACs running in full swing (R-55A,
B-62A & Y-59A).
In another embodiment, there is installed Voltage boosters /Capacitor banks as
shown in Fig 3 in the disclosed MVAC network to combat low voltage
problems under certain conditions as a short term measure in some of our Mains
Districts.
In an embodiment an auto-transformer with discreet tap-settings to step-up the
voltage whenever it falls below a pre-determined threshold value. This method
is a temporary solution and shouldn't be used Lu rise the voltage beyond 20-
30V, otherwise there would be a serious drop in the upstream voltage.
Therefore, the Voltage Regulator cannot be used alone in sectors where the
power-factor is poor. It is because the auto-transformer itself consumes reactive
power for magnetization. To alleviate this issue, the regulator is integrated with
a lOkVAR capacitor bank. The capacitor bank would compensate the required
VAR.
The capacitor banks are the source of VAR in the network. The Cap-Bank
compensates the VAR loading in the network, which restricts the voltage-dips,
when placed at strategic location in the network.

50kVAR Cap-Bank is used.
During opreration, it has been found from site-observation that the installed
capacitor gets discharged instantly through the connected load, after the
distributor is de-energized. Still for additional safety, a standby time of around
10 minutes is allowed, after de-energizing the network, before commencing any
job on the circuit.
The applicant have so far achieved desired results post installation of such
devices. So far we have installed the devices in the following locations as listed
below.

Since the population of Capacitors are increasing and this may create safety
hazards as well as erratic voltage in the network during low load condition
especially in the winter the following SOPs need to be strictly adhere to.
Standard Operating Procedures for LT Network
• At the feeding Pillar box sign writing to be done as delineated below:
"DANGER: CAPACITOR BANK / VOLTAGE BOOSTER FITTED AT
LP XXXX/XXXX."
• Remove fuses for all the phases before undertaking any maintenance job.
• Wait for at least 10 minutes before applying earth / creating safe zones by
using shorting chains.
• Ensure that local earths are removed prior to insertion of fuses.
• During winter take voltage readings at the consumer premises and
accordingly de-energise the devices fitted in the network if required.
• This is in addition to safety protocols prevailing for maintenance and
breakdown jobs.
• The installed units have successfully met the customer satisfaction during
the summer.
• Installing a new DTR to meel Ihe consumer demands would have cost
around 20-30 lac for each installation, but this innovation has proved
economical and effective.
• During winter the loads might fall and the capacitor-banks might cause
over-voltage, so a review of the arrangements should be done during the
winter season.

Since, in real-time the active-power consumed by loads at consumer premises
cannot be controlled, therefore, in order to reduce the burden on the network the
inductive-load can be reduced only by installing the capacitors at strategic
location.
It would be worth to mention that the installed capacitors will also reduce the
line-loss (I2R) to an extent.
The subject matter of embodiments of the present invention is described here
with specificity to meet statutory requirements, but this description is not
necessarily intended to limit the scope of the claims. The claimed subject matter
may be embodied in other ways, may include different elements or steps, and
may be used in conjunction with other existing or future technologies. This
description should not be interpreted as implying any particular order or
arrangement among or between various steps or elements except when the order
of individual steps or arrangement of elements is explicitly described.

WE CLAIM
1. A Low Tension Compact Substation (LTSS) comprising of:
a voltage regulator at the point on the distributor where the voltage falls below
the threshold value;
a capacitor-bank fitted, at a nodal-point of the said incoming distributor;
a fuse strip unit of 160 A rating connected at the incomer side of the transformer;
and
an adjustable rating MCCB of 100A rating connected on the outgoing side of
the transformer.
2. The Low Tension Compact Substation (LTSS) as claimed in claim 1,
wherein the said voltage regulator includes a 50kVA 3 phase Dry type Y-
Y variable voltage Auto transformer.
3. The Low Tension Compact Substation (LTSS) as claimed in claim 2,
wherein the said Auto transformer is embedded inside a cubicle housing.
4. The Low Tension Compact Substation (LTSS) as claimed in claim 2,
wherein the said auto transformer includes variable taps in order to
produce output ranged at 7.5%, 15% & 20% of the input voltage.
5. The Low Tension Compact Substation (LTSS) as claimed in claim 2,
wherein the said autotransformer is dry type and the cooling type is
ANAF.
6. The Low Tension Compact Substation (LTSS) as claimed in claim 1,
wherein the said substation further includes heavy duty fans fitted inside

the.cubicle which are controlled by a timer for alternatively switching the
fans ON & OFF.
7. The Low Tension Compact Substation (LTSS) as claimed in claim 1,
wherein said substation further includes Energy meter in the circuit for
measuring & displaying various electrical parameters of the Transformer
load.
8. The Low Tension Compact Substation (LTSS) as claimed in claim 1,
wherein the said capacitor bank is configured to take care of the reactive
burden of both the VR as well as the load.
9. The Low Tension Compact Substation (LTSS) as claimed in claim 1,
wherein a standby time of 10 minutes is allowed, after de-energizing and
before commencing any job on the circuit.
10.The Low Tension Compact Substation (LTSS) as claimed in claim 1,
wherein the said capacitor bank id preferably of rating 50kVAR
congigured to compensate the VAR loading in the network, which
restricts the voltage-dips, when placed at strategic location in the
network.