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Mobile Grid Station Paper By Obaid Ur Rahman


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Mobile Grid Station Paper by Obaid-ur-Rehman

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Mobile Grid Station Paper By Obaid Ur Rahman

  1. 1. BISM-ALLAH AR RAHMAAN AR RAHIM In the name of Allah, the compassionate, the merciful
  2. 2. MOBILE GRID STATION <ul><li>The paper discusses the detail of Mobile Grid Station Technology and its application being done by almost all the utility companies in the world. The two utility companies within Pakistan also possess the Mobile Grid Stations which not only serve the purpose of support/improve the existing power transmission bottlenecks but also is an immediate restoration of supply to consumers in case of any major fault occurrence. </li></ul><ul><li>The Mobile Grid Station Technology provides a short term as well as a long term solution to specific network problems, which are discussed in detail under this paper. To immediately make-up for the fault emergency of permanent nature it is a very efficient means to restore the distribution supply within 24 hours period. </li></ul>
  3. 3. MOBILE GRID STATION <ul><li>The Mobile Grid Station Technology is available in two kinds; one with generator as prime source of supply and the other having High Voltage equipment installed on two trailers to be connected with high voltage network of the utility company and step down the voltage to consumer voltage level. The supply to different consumers is provided by a group of 11 kV switchgear panels installed within the Mobile Grid Station. </li></ul><ul><li>In WAPDA (NTDC) and KESC the general requirement of Mobile Grid Station is of 15/20 MVA, three phase, 50 c/s, 132 kV/12 kV having outdoor type HV equipment and transformer on one semi-trailer and LV equipment, control and relay panels, auxiliary service panel, battery and battery charger on the other semi-trailer. </li></ul>
  4. 4. MOBILE GRID STATION <ul><li>The outdoor type mobile grid station is intended to meet general emergency situation on or serve as a temporary grid station for local distribution. In KESC Network one long term case example is of Pakistan Refinery Limited (PRL) where the mobile type grid station is un use for a number of years and is about to be relieved in couple of months as soon as the commissioning of PRL G/S is accomplished under the Govt. of Pakistan Financial Investment Plan. </li></ul><ul><li>On the next slide is shown the layout of the mobile grid station, where all components are suitably dimensioned both as regards size and weight and arranged in compact layout as necessary to meet the particular requirements of the intended application as well as the highway regulations of Pakistan. </li></ul>
  5. 5. MOBILE GRID STATION Layout Plan
  6. 6. MOBILE GRID STATION <ul><li>The high voltage equipment in the incoming section is outdoor type as per the single line diagram and comprise of the following: </li></ul><ul><ul><li>132 kV Circuit Breaker </li></ul></ul><ul><ul><li>120 kV Lightning Arrestor </li></ul></ul><ul><ul><li>132 kV Disconnecting Switch or Disconnector </li></ul></ul><ul><ul><li>132/12 kV, 15/20 MVA Power Transformer </li></ul></ul><ul><li>The operating mechanism of Circuit Breaker is preferred to be of spring type, the charging motor voltage and control/trip coil shall also operate at 48 V DC. </li></ul><ul><li>The Lightning Arrestor is specified to be of metal oxide type and is braced to withstand shocks and avoid vibration during transit. </li></ul>
  7. 9. MOBILE GRID STATION <ul><li>The number of 11 kV switchgear is required by KESC as six number outgoing panels. The 11 kV switchgear is housed inside a canopy. The canopy walls are heat insulated made of PVC sandwich panels with polyurethane insulation. Special roof insulation against sun protection preferably in grey color. The canopy is to be provided with detachable steps. It is also equipped with folding table or desk and seat for operator. </li></ul><ul><li>The 11 kV connection between the power transformer 11 kV terminals (on one of the trailer) and the 11 kV incoming panel termination pad (on another trailer) is made by means of 630 Sq. mm single core, XLPE insulated, copper conductor power cable. Two cables are used per phase. </li></ul>
  8. 10. MOBILE GRID STATION <ul><li>When the grid station is out of service, the cable shall be disconnected from the transformer and stored on the 11 kV switchgear trailer. Necessary arrangement for securely holding it in safe position is provided. </li></ul><ul><li>The mobile grid station is provided with the same earthing facilities as the normal or a permanent grid station. Each semi-trailer of the mobile grid station is provided with effective grounding through the metallic design of chasis and by independent mats. All apparatus and devices will be firmly connected to the mat in such a manner as to prevent loose connections during transport. </li></ul><ul><li>Grounding pad on both sides of the semi-trailer are provided to permit connections to external grounding devices. Such pad shall be provided with clamp to accommodate copper cables of appropriate size. Particular care is taken for the effective grounding of Lightning Arresters and Power Transformer neutral terminal. </li></ul>
  9. 11. MOBILE GRID STATION <ul><li>All high voltage equipment is connected by means of flexible connectors to a copper earthing bar that runs along the trailer on one of the longitudinal beams. On this bar, the provision is made at three places to connect the mobile grid station to an existing earthing network, if the grid station is set-up in an existing earthing network. </li></ul><ul><li>One earthing device consisting of a voltage indicator and one earthing bridge and three earthing plugs shall be supplied with each semi-trailer. </li></ul><ul><li>All above mentioned specified requirements are more or less common for both types of mobile grid stations available i.e. one with prime source being system high voltage of the utility network an the other being a self contained mobile grid station having 11 kV self generation capability; details of which are shown in the following slides. </li></ul>