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STUDY AREA :
TO achieve the above objectives, one substation namely Medi city has been taken. Medi city area is a part and parcel of Hyderabad in Andhra Pradesh state, which lies in the Survey of India Toposheet 56k/16.This total substation is having three feeders namely, Raja Bollaram, Medicity Hospital and pudur. The area covered for medicity substation is 56 kms. From this 33/11kv substation levels, consumers can directly take electricity through the Transmission Network System. So the study of one full substation and its network has been taken.


The Figure shown in this page explains the flow of electricity from the Generation to the Consumers.

Materials and Methodology

GPS Observations
GPS receivers that are capable of recording co-ordinate data for post-processing.

• GPS Receiver (wgs-84 coordinate or longitude, latitude, altitude)
• Better accuracy in case of PDS

Attribute information from Electricity department.
Medicity substation attribute data which has three feeders have been collected from electricity department. For each feeder, distribution and power transformer details,HLVpoles,HV poles,LV poles,circuit breakers information has been collected.

The details about the Consumer name, Plot Number, The transformer code and its poles codes from where the consumer is drawing power, Usage category, Meter number, Meter Make and the Meter readings of the consumer have been collected from deparment. The information details about the transformers have been surveyed and updated.

Systems and Software:

• ARC INFO 3.5
• ARC VIEW 3.2.a
• VISUAL BASIC 6.0
• MAP OBJECTS
• MS-OFFICE-ACCESS AND EXCEL

Methodology
The first process that includes the collection of pole and transformer locations for all the three feeders of Medicity substation, with the help of GPS instrument. The second process that includes the development or generation of network(point and line) by using the GIS software. The final process involves an application development using with Visual Basic and Map Objects.

GPS Survey:
The process that involves while collecting the data from GPS is as follows.
Static GPS surveys:
Static GPS survey procedures that allow various systematic errors to be resolved when high accuracy positioning is required. Static procedures are used to measure baselines between stationary GPS receivers by recording data over an extended period of time during which the satellite geometry changes.

Satellite Geometry:
Satellite geometry factors which must be considered when planning a GPS survey are:

1. No. of satellites are available.
2. Minimum elevation angle for satellites
3. Obstructions limiting satellite visibility
4. Position Dilution of Precision(PDOP)

Network Design:
Base lines (vectors): Base lines developed by processing data collected simultaneously by GPS receiver at each end of a line. For each observation session, there is one less independent base line than the no of receivers collecting the data simultaneously during the session. The Base lines should be the series and continuous connection e.g. power supply. The diagram shows the connectivity of the vectors, each individual line is connected to a single continuous network. As power is continuous in connection with its supply the network and each vectors location is also continuous up to where it ends the line.

Networks: Each station in a network must be connected, with atleast two independent base lines. Avoid connecting stations to a network by multiple baselines to only one other network station.

Field Procedures:
Proper field reconnaissance is essential to the execution of efficient and effective GPS surveys. Reconnaissance should include:

• Station setting or recovery
• Checks for obstructions and multipath potential
• Preparation of station descriptions (monument description, to- reach descriptions for azimuth pairs, etc.)
• Development of a realistic observation schedule.

Station Site Selection:
The most important factor for determining GPS station location is the project’s requirements (needs). After project requirements, consideration must be given to the following limitations of GPS:

• Stations should be situated in locations that are relatively free from horizontal obstructions. In general, a clear view of the sky is required. Satellite signals do not penetrate metal, buildings or trees and are susceptible to signal delay errors when passing through leaves, glass, plastic and other materials.
• Locations near strong radio transmissions should be avoided because radio frequency transmitters, including cellular phone equipment, may disturb satellite signal reception.
• Avoid locating stations near large flat surfaces such as buildings, large signs, fences etc., as satellite signals may be reflected off these surfaces causing multipath errors. With proper planning, some obstructions near a GPS station may be acceptable.

Weather Conditions:

• Generally weather conditions do not affect GPS survey procedures with the following exceptions:
• GPS Observations should never be conducted during electrical storms.
• Significant changes in weather or unusual weather conditions should noted in the observation log(field notes). It is generally be avoided during periods of significant weather change.
• In general a clear view of sky is required to collect the satellite data with in its locations and without having any errors.

Documentation: Generally, survey report includes the project requirements. The final field survey report should include this following information:

• The X,Y,Z co-ordinated locations must have been collect and mention in its Longitude, latitude and altitude respectively., in the columns mentioned from the GPS observations.
• No. of satellites that are visible at the time of data collection.
• The existing features such as transformer and its code details and pole information should mention in the description part.
• Each pole and its connectivity towards the transformers and feeders and substations like wise...and poles connectivity should be clearly mentioned. And a rough diagram or mapping of poles network should be drawn for clear understanding of the field, which would be later more useful when generating its Locations on Arc Info.
• Locating Transformers, HV Poles, LVPoles, HLV Poles, Plots

GPS is the best tool available for positioning and can economically replace the existing practices of survey, monitoring and therefore should be adopted by Central Power Distribution Company early. GPS system is controlled by the United States and is capable of even selective degradation in accuracy.

GPS Integration with GIS for Network
The GPS survey data has been processed in ms-excel. The X,Y locations i.e longitude and latitude, which is the important feature has been converted from degrees, minutes seconds to decimal degrees, that which Arc Info supports the creation of co-ordinated network. The mapping of point and line features has been generated separately and editing has been done for its proper and exact location of poles and transformers in Arc Info. Like wise, all H.Ts and L.T lines under each feeder has been created and converted them into shape files. Medi city Substation which is having three feeders namely Raja Bollaram , Medicity Hospital and Pudur have been converted into shape files which were be the supporting files to the ArcView and Map Objects.

In Arc View, Transformers both of H.Ts and L.Ts located with unique symbols. The important work that incude here the database creation. Codes given for identification of substation, feeders, each feeder transformers and its codes, pole codes was given and updated. These codes are main source in developing the application in Visual Basic.

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