help about substation design project(acedemic project)

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    Vidhyut S.

    I am final year student.
    We are going to do a project based on Substation design but

    we don't know what to do something new..

    We will just analyse various substations and will make simply one report….

    Please help me to do some innovative work…..



    Electricity is generated in bulk at power
    stations, located at remote places. Location of power stations is governed by
    various factors, such as economy of generation, safety availability of
    resources. Electricity is to be continuously generated to meet the demand and
    is to be transmitted over long distances to load centres. For this purpose, a
    complicated power system has been developed. The modern electrical system forms
    a large interconnected network and covers a vast geographical area. This
    interconnected transmission and distribution network is divided into three
    hierarchical levels as shown in Figure 1.


    At generating stations, voltage level of power
    generated at 3.3 kV, 6.6 kV, 11 kV or 33 kV is stepped up and it is fed to the
    main transmission network, operating at 400 kV or above. The main transmission
    network forms a mesh or ring and is interconnected with neighbouring networks.
    This network delivers power to sub-stations where the voltage level is stepped
    down to 220 or 132 kV and the power is fed to the sub-transmission network.
    Power from local generating stations is also received at this level. This
    network transmits power to other sub-stations, where the voltage level is
    brought down to 33 kV and is delivered to the distribution network. The distribution
    network feeds directly to 33 kV consumers and delivers power to 33 kV
    sub-stations. At these sub-stations, the voltage level is further reduced to 11
    kV and consumers are supplied through 11 kV feeders. For medium and low voltage
    consumers, pole-mounted or indoor 11/0.4 kV sub-stations are installed on these
    feeders. The sole aim of this highly complicated and large-interconnected
    network is, to supply continuous, safe, reliable and good quality electricity
    to consumers. These aspects are considered separately as follows:

    Safety Aspects

    Frequency of occurrence of electrical accidents, gives an idea about the safety
    aspect of supply system. Table 1 gives number of electrical accidents occurred
    in last few years in Uttar Pradesh.

    It is seen from the above that nearly 750
    electrical accidents are being reported every year and about three-fourth of
    these are fatal, causing loss of human or animal lives. The Section 44A of
    Indian Electricity Rules, 1956, provides the details regarding the intimation of
    accidents which is described below.

    If any accident occurs in connection with
    generation, transmission, supply or use of energy in or in connection with, any
    part of the electrical supply lines or other works of any person and the
    accident results in or is likely to have resulted in loss of human or animal
    life or in any injury to a human being or an animal, such person or any
    authorised person of the State Electricity Board/Supplier, not below the rank
    of a Junior Engineer or equivalent shall send to the inspector a telegraphic
    report within 24 hours of the knowledge of the occurrence of the fatal and a
    written report within 48 hours of the knowledge of occurrence of fatal and all
    other accidents. Where practicable a telephonic message should also be given to
    the Inspector immediately the accident comes to the knowledge of the authorised
    officer of the State Electricity Board/Supplier or other person concerned.

    Unfortunately, public is not aware of this rule
    and it is frequently breached by the board’s of supplier’s officials. As a
    result, most of the electrical accidents remain unreported. Even though, the
    data shown in Table 1, clearly indicate that the supply of electricity is not
    satisfactorily safe.

    Table 1 Number of electrical accidents occurred
    in Uttar Pradesh


    Number of Accidents















    Continuous and Reliable Supply of Good Quality

    Presently, continuous supply of electricity to all the consumers is not
    feasible because of a large gap between demand and generation. To bridge this
    gap, high level planning is required which involves central as well as state
    governments. This is a well known fact and generally the consumers are not
    bothered about it. However, they are most seriously involved with the
    uninterrupted supply of available energy. Inability of the distribution system
    to ensure reliable supply of good quality power, during scheduled hours, has
    become a major concern and it has received considerable attention of various
    sections of society, such as politicians, professionals, businessmen and common
    people. Interruption during supply hours is caused mainly due to breakdowns,
    which occur frequently. Also the quality of power supplied, especially in rural
    areas, is not good, i.e., voltage and frequency vary beyond permissible limits.
    As a result, performance of appliances and equipments is adversely affected and
    damage to them is caused.

    Taking inspiration from the problems discussed
    above, a survey was conducted about the defects and shortcomings of 33 kV
    distribution sub-stations of UP Power Corporation Ltd. (previously the UP State
    Electricity Board), located in the Ghazipur district. Purpose of these
    sub-stations is voltage transformation, switching, metering and monitoring the
    condition of the system. In the survey, 20 sub-stations were covered during the
    period from September to December, 1999. The survey was conducted in the light of
    Indian Electricity Rules, 1956, made to regulate the generation, transmission,
    supply and use of electricity.


    Section 29(1) of Indian
    Electricity Rules, 1956 reads as: all electric supply lines and apparatus shall
    be of sufficient ratings for power, insulation and estimated fault current and
    of sufficient mechanical strength, for the duty which they may be required to
    perform under the environmental conditions of installation, and shall be
    constructed, installed, protected, worked and maintained in such a manner as to
    ensure safety of personnel and property. In general, observations are made on
    the basis of this Section, but wherever necessary, specific Sections of the
    said Rules are referred. Findings of the survey are as follows:

    1. Proper danger notices
      [Section 35], fire buckets filled with clean dry sand and fire extinguishers
      ready to use for dealing with electric fires [Section 43(1)], and first-aid box
      [Section 43(2)], were not found at any of the sub-stations. Also, instructions
      for restoration of persons suffering from electric shock [Section 44(1)], were
      not affixed in any of the centre. Further, acquaintance of authorised persons
      with these instructions and their competency to apply them [Section 44(3)] were
      not ensured. The situation worsens with the fact that these sub-stations do not
      have tools and accessories, such as handle for charging the oil
      circuit-breakers (OCBs), earthing chains, rubber mats, hand gloves, safety
      belts, etc. for proper working. Thus, safety of personnel and property is the
      most neglected concern at these sub-stations.
    2. At 17 of the
      sub-stations, the number of working oil circuit breakers (OCBs) were found to
      be less than the required ones [Section 50(1)(c)]. Thus, instead of proper
      connections of Figure 2(a), they were found connected as shown in Figure 2(b).
      Also, 19 of the sub-stations do not have load breaking isolators or TPMOs on
      all the outgoing feeders. Connection of two or more feeders to some of the
      OCBs, as shown in Figure 2(b), results in power cut for twice or more larger
      area in case of breakdown or during period of maintenance. Thus, supply to a
      large number of consumers is unnecessarily interrupted. Further, burden of
      these OCBs has increased considerably as they have to make or break twice or
      larger amount of current than they were intended for. As a result, melting,
      pitting or fusion of their contacts occur frequently. From the safety point of
      view, it is never advised to work on the feeders with only opening the circuit
      breaker contacts. But it is not always possible to follow the guidelines as
      TPMOs are not provided on most of the feeders. Further, at 8 of the
      sub-stations, some of the working OCBs have mechanical defects and at 17 of
      them, their mechanisms were found bare. Thus, persons on duty do not take
      interest in operating them unless there is an utmost urgency. In this way,
      during abnormal conditions, maximum damage to the system is caused. Clearly,
      switching operations are not being performed satisfactorily at these
    3. At 6 of the sub-stations,
      most of relays were found either removed or defective. Even the condition of
      the rest of the relays could not be judged as at none of the sub-stations
      periodical testing of them is being carried out and records thereof are being

    Consider the feeder A in Figure 2(a), assuming
    its full load current as 100% let its two over-current relays are set at 135%.
    When two more feeders are connected with the same OCB as shown in Figure 2(b),
    the full load current becomes 300% and for proper working of the OCB, the
    relays must be set at about 400%. Thus, even the healthy over-current relays
    will not be able to sense the abnormal conditions unless the current increases
    to a much larger extent.

    As far as earth fault relay is concerned, it is
    not expected to operate the OCB for earth faults occuring on the line as none
    of the overhead lines has continuous earth wire or proper earthing of
    non-current carrying metallic parts [Section 90]. Thus, even a healthy earth
    fault relay will be able to sense the earth fault occuring inside the control
    room and the switchyard only. Also, even this may not happen as at 4
    substations, earthing system inside the switchyard [Section 67] was found
    defective. Further, periodical testing of the earthing system is not being
    carried out and records thereof are not being maintained at any sub-station
    [Section 67(5)(b)]. In this way, neither the over-current not the earth fault
    relays are able to provide effective protection to the system. The problem is
    so severe that at some of the sub-stations, fuses on the 33 kV side of the
    transformers were found as the only effective means of protection.

    The situation worsens with the fact that at some
    of the sub-stations, all the outgoing feeders were found connected with a
    single OCB, as OCB of feeder A in Figure 2(b). In this case the OCB of the
    feeder, with settings of the relays changed accordingly, is in series with the
    OCB of the incoming feeder. Thus, one of the OCBs becomes redundant.



    One of the important functions of these sub-stations
    is that of metering the energy, but unfortunately none of them has the required
    number of energy meters in working order. Some of them were found either
    removed or defective. Also, periodical testing of energy meter is not being
    carried out regularly and records thereof are not being maintained. At some of
    the sub-stations, some of the energy meters have not been connected because of
    non-availability of current or/and potential transformers. Thus, proper
    metering of energy is not being performed at these sub-stations. Instead of
    metering the energy supplied, it is being allocated to different feeders,
    depending on the ingenuity and experience of the person involved. In this way,
    the actual data of energy supplied by these sub-stations is not available which
    results in failure of the schemes and damage to the system, designed on the
    basis of erroneous data, and makes it difficult to estimate the losses in the
    system due to theft. Thus, the energy theft is encouraged and preventative
    measures are inhibited.

    Another aspect of not metering the energy
    properly is the fact that it permits the manipulation by the officials
    responsible for the collection of corporation’s revenue. They lessen their
    burden by allocating maximum amount of energy to the sectors with unmetered
    supply and minimum tariff, such as agriculture sector, Kutir Jyoti scheme,
    Harizan Basti, and show a large amount of energy as losses in the distribution
    system. As a result, the revenue of the corporation is reduced considerably.
    Further, the state exchequer is adversely affected as the amount of electricity
    duty is significantly reduced.

    1. Indicators on the panel
      in the control room, such as ammeters, voltmeters, power factor meters, were
      found defective at 17 sub-stations. Also at 11 of them, indicators on the
      transformers were defective. Further, 19 sub-stations have defective alarm
      system. Thus, even a healthy Buchholz relay and oil temperature indicator will
      not be able to give remote warning of development of incipient faults or leakage
      of transformer oil and abnormally high oil temperature. So the operator would
      not be able to take preventive action. Thus, proper monitoring of the system
      condition is not feasible at all. The situation worsens with the fact that at 2
      sub-stations, unauthorised persons were on duty and logsheets were not being
      maintained regularly.
    2. As far as maintenance of
      transformers is concerned, their bushings were found broken at 2 sub-stations
      and oil leakage was seen at 8 of them. At 10 of the sub-stations, silica gel of
      the transformers was found old and ineffective. Also, at all the sub-stations,
      periodical testing of the transformer oil is not being carried out and records
      thereof are not being maintained.
    3. At 15 of the
      sub-stations, wiring inside the control room was found defective. Also, at 2
      sub-stations, unused or damaged cables were found in the cable trench and at 6
      of them, cable trenches were found not properly filled with sand and covered.
      Further, unused materials or defective equipments were found stored inside the
      control room at 7 sub-stations. Even spacing behind the panel was found
      improper at one sub-station, indicating flaw at the planning and designing
    4. At 11 sub-stations, some
      insulators were found broken in the switchyard and isolators were found
      defective at 11 of them. Also unused installations were found dangerously
      connected to the supply mains at 5 sub-stations and unused materials or
      defective equipments were stored inside the switchyard of 7 of them. Further,
      at 14 sub-stations, fencing of the switchyard was found either broken or
      ineffective, allowing entrance to unauthorized persons and animals. Even
      connections inside the switchyard and on the double poles and lines of the
      outgoing feeders were not found proper at 17 of the sub-stations.
    5. At 18 of the
      sub-stations, some or all the surge or lightning arresters were found broken or
      removed. The situation is so worse that at some of these sub-stations, healthy
      ones are provided on unused installations while installations in use do not have
      proper protection. Thus, temporary power frequency over voltages, lightning and
      switching surges are likely to damage the main 33/11 kV transformer, the
      costliest and inevitable equipment of the sub-station.
    6. Section 54 provides that
      the supplier shall not permit the voltage, at the point of commencement of
      supply, to vary from the declared voltage.
      in the case low and
      medium voltage, by more than 6%, or;
      in the case of high
      voltage, by more than 6% on the higher side or by more than 9% on the lower

      To maintain the voltage of supply within permissible limits, capacitor banks
      are provided for reactive power injection at these sub-stations, but at none of
      them these were found operational. Surprisingly, a consumer using energy at low
      power factor, is penalized with surcharge but the Corporation is completely
      negligent to its responsibility of providing good quality power. As a result,
      performance of equipments and appliances suffers and their life is also

    Parallel operation of transformers is not being
    used at any sub-station, having two transformers. Also, none of them is
    provided with OCB on the 33 kV side. Further, at one of the sub-stations,
    auto-reclosing circuit breakers were provided but the Corporation has failed to
    maintain them. Thus, better techniques, to improve system’s performance, are
    not being used and it seems that the Corporation doesn’t have sufficient
    expertise to cope up with these at this level.


    The survey indicates that the safety of personnel and property is the most
    neglected concern at these sub-stations, resulting in increase in occurrence of
    electrical accidents. It is found that the Corporation’s officials, instead of
    investigating the cause of accidents and taking precautions to avoid them in
    future, rely on hiding the facts. As far as switching is concerned, most of the
    sub-stations have defective OCBs and improper connection of feeders. Also,
    protective relays have rarely been found working properly. Thus, proper
    switching is not being performed at these sub-stations. Further, energy meters
    and indicators are defective at most of the sub-station, so the metering and
    condition monitoring are also not being performed satisfactorily. In this way,
    except the voltage transformation, these sub-stations have failed to perform
    effective and satisfactorily switching, metering or condition monitoring. In
    short, they have lost much of the purpose they were meant for. Thus, the
    Corporation has failed to maintain these sub-stations based on age-old
    technologies, and has not attempted seriously the incorporation of better
    techniques to improve the system’s performance at this level.

    Vidhyut S.

    Thanks for giving such a nice information.

    Your main concentration is on safety measures.
    It is right that accidents occur due to lack of technology but
    I live in ‘Gujarat’.We have very less chances of accidents.
    Rarely two or three accidents occur in a year.
    Can you suggest another idea..?

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