power plant: Electrical Works ( low voltage Switchgear & Switchgear)

 power plant
LOW VOLTAGE SWITCHGEAR & MCC

SCOPE OF SPECIFICATIONS

These specifications cover the design, manufacture, assembly, inspection, and testing in the manufacturer workshop, as well as packing, supply, delivery, unloading, storing, erection, painting, testing and commissioning, trial operation, and performance test of the Low Voltage AC Switchboards and Motor Control Centers (MCCs) complete in every respect and suitable for safe, efficient and reliable operation.

DISPOSITION

                       The various low voltage switchgear and MCC’s shall be located in the following areas:

               -         Turbine Hall (Low bay area) / Switchgear room

               -        Fuel Gas Electrical Building

              -    Fuel treatment.

                   -    Fuel unloading and forwarding.

                 -     Fire building.

               -   Transmission building.

                -     Water Treatment building.

                -    Main control room building.

              -       Administration and other facilities.

               -      Workshop.

          -       Any other relevant area.

   The CONTRACTOR shall calculate the required number of AC Switchgears/Switchboards, and Motor Control Centers in his detail design and layout. The arrangement must be well designed, reliable, redundant as required, and adequate for the safe operation of the plant.

DESIGN AND CONSTRUCTION REQUIREMENTS

                                     -    This section describes the features and requirements of an enclosed dead front freestanding LV Switchgear and Motor Control Centers for each gas turbine unit and station auxiliaries to be furnished in these project.

                                    -   The 480V switchgear will  be controlled from the DCS, whereas the MCC will be controlled from the gas turbine control system and / or DCS. 

                                    -    The low voltage switchgear and motor control center shall be provided with its own controller and interface/integrate with DCS through fiber optic cables.

                                 -    Busbars shall be copper and shall comply with IEC 60439-2.

 

                                  -     Busbar identification shall be in accordance with the relevant phase color.

                               -     All auxiliary switches shall be wired to a fixed terminal board. 

                                -      Circuit breakers shall be SF6/air brake and horizontally withdrawable.

                              -      All motor starters and feeder cubicles shall be fully withdrawable.

                               -     The short time the rating shall be in accordance with the results of fault studies. 

                               . -       Contractor shall be capable of withstanding the motor stalled current until the associated protection device operates.

 

 Contactors shall comply with IEC 60439-4, including Type ‘2’ coordination.

                              -       Composite fuse and switch equipment in the form of either a fuse-switch or switch-fuse shall comply with IEC 60439-3.

                   -       Mechanical or electrical safety interlocks shall be provided for isolation and maintenance and to avoid unsafe switching conditions.

                           . -       Suitable handling equipment shall be provided for circuit breakers or starters which weigh more than 25 kg.

                      -      Each gas turbine shall be provided with unit switchgear, which shall normally be fed from generator output through a unit auxiliary transformer with hot transfer switch. 

 In case of failure normal supply from the unit, the switchgear shall remain supplied without tripping the machine through the 480 V essential switchboard allocated from auxiliaries of different sections or blocks and the interconnections between different boards shall be selected to prevent tripping of a turbine generator unit in case of any single electrical fault.

                         -    All main distributions shall be fed by 2x100% feeds. These distributions shall be coupled via a normally open bus-sectionalized, with 2 out of 3 logic.

                           -   The rated insulation level and one-minute power frequency withstand voltages shall be in accordance with the applicable IEC Standards and the specified voltage classes.

                        -     The minimum fault levels shall be calculated by the CONTRACTOR on the basis of the design data of components with consideration of the maximum acceptable tolerances according to standards and the maximum system voltages to be anticipated.

                       .   -     Current ratings for standardized products shall be referred to 50°C ambient temperature. Such equipment, however, shall be selected with due regard to the environmental conditions at the Site i.e. if upon the increased ambient temperature a duration of the standard current rating becomes necessary.

 Such duration shall be restricted to such an amount that a margin of 10 % is still maintained ahead of the actual circuit requirement. In all such cases, the CONTRACTOR shall state the permissible current ratings for both IEC and site conditions.

                           -     All LV switchgear/switchboards and MCCs shall have voltmeters with selector switches (for phase to phase & phase to neutral voltage measurement) for each incomer as well as busbar section and all main outgoing feeders compartment shall be equipped with suitable ammeters along with selector switches.

 Outgoing feeders’ cabinets, supplying power to unit auxiliaries shall be equipped with energy meters for measurement of energy consumed.

                            -    Lamp test the facility shall be provided on all LV switchgear/switchboards and MCC’s.

                          . -       The transparent insulating barrier shall also be provided on live busbar parts in order to protect personnel from sudden touch or any mishap.

                          .-        The CONTRACTOR shall be required to submit a load calculation for each individual LV switchgear/switchboard, MCC, and each transformer.

                          -      The CONTRACTOR shall submit complete motor and load list for each board and MCC for review of the COMPANY Engineer.