DETAILED DESCRIPTION OF THE PROPOSED - Kappa/5 Final...  3 DETAILED DESCRIPTION OF THE PROPOSED ACTIVITY

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    33 DDEETTAAIILLEEDD DDEESSCCRRIIPPTTIIOONN OOFF TTHHEE PPRROOPPOOSSEEDD AACCTTIIVVIITTYY

    3.1 Project Description and Infrastructure

    Eskom propose to construct a 765/400 kV Substation with two new 765kV line bays; Kappa-Gamma and Kappa-Omega, with only Kappa-Gamma requiring a line reactor, near Ceres in the Western Cape. This substation will cover an area of approximately 150 ha. This project as part of the 765 kV super-grid scheme is required to strengthen the power supply to the fast growing Western Cape (Western Grid) regional loads that cannot be provided by the existing Transmission and Distribution networks. The proposed infrastructure to be constructed as part of the 765 / 400 kV Substation will comprise the following:

    1 x 765/400kV 2000 MVA transformer;

    765kV busbar and a 400kV busbar;

    The following feeders:

    - 765kV feeder with line 400MVA line reactor bay to Gamma;

    - 765 kV feeder bay to Omega;

    - 400kV feeder bay to Drorrivier No1;

    - 400kV feeder bay to Drorrivier No2;

    - 400kV feeder bay to Bacchus No1; and

    - 400kV feeder bay to Muldersvlei.

    The following reactors:

    - 400kV 100MVAr busbar reactor;

    - 765kV 400MVAr busbar reactor; and

    - 765kV 400MVAr line reactor for the Gamma feeder.

    The following 400 kV loop-in loop-out lines are also proposed to be constructed:

    Drorrivier/ Muldersvlei loop-in and out lines for Kappa (15 km, depending on the site); and

    Bacchus/ Drorrivier loop-in and out lines for Kappa (15 km, depending on the site) line.

    3.1.1 The 765 kV System

    The Kappa 765 kV high voltage (HV) yard is to be constructed as part of the 765 kV super-grid development to the Western Cape areas to provide for the large load growth that is expected to occur in the near future.

    Due to the immense size and large dimensions required for phase-to-earth and phase-to-phase clearances required for 765 kV AIS layouts, a tubular construction is to be employed to minimise the visual impact of the substation on the surrounding area. In addition, correctly sized bus tubing will

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    minimise the corona discharge at these ultra-high voltages. It is also necessary to cater for the level of injected and through power the busbar system will be required to support once the Medupi and other power station projects are completed.

    The 765 kV busbar configuration is to depart from the conventional double busbar selection with bypass, in favour of a more reliable One-and-a-half Circuit Breaker philosophy, with an added benefit in that the length of the busbar is reduced to less than half that of its counterpart. The system still employs two normal running busbars (No.1 and No.2), but with a three circuit breaker system servicing two circuits. This arrangement eliminates the need for the bypass facility due to the sharing of the so called Tie circuit breaker that allows automatic re-routing of power flow under live conditions if a busbar fault occurs. The arrangement inherently provides for access to all circuit breakers, which is not the case with the current double busbar selection with bypass. The possible future expansion of the Kappa 765 kV system also provides for two bus sections to facilitate the removal of smaller zones of busbar for maintenance purposes.

    In order to minimise the initial work required to establish the first phase of the 765 kV system at Kappa, future Feeder 4 Reactor position is to be used for Busbar Reactor 1.

    The section of the Reactor Transfer Busbar servicing the above bays is to be constructed with the connections to it. The rational behind this is that it will be difficult of retrofitting it later due to limited outages that are granted and the large electromagnetic fields that are involved when working in the HV yard.

    The 765kV Kappa system will be comprised of the following bays:-

    2 x fully equipped feeder bays tied back-to-back with the appropriate circuits through a Tie circuit breaker bay to provide for the 1 circuit breaker arrangement (Gamma 1 and Omega 1);

    1 x fully equipped switch-able line reactor bay tied back-to-back with the appropriate circuits through a Tie circuit breaker bay to provide for the 1 circuit breaker arrangement (Gamma 1);

    1 x fully equipped switch-able busbar reactor bay tied back-to-back with the appropriate circuits through a Tie circuit breaker bay to provide for the 1 circuit breaker arrangement (Busbar Reactor 1);

    1 x fully equipped transformer bay tied back-to-back with the appropriate circuits through a Tie circuit breaker bay to provide for the 1 circuit breaker arrangement (T1); and

    2 x partially equipped bus section bays with a set of CVTs and an isolator each (No.1 Bus Section 1 and No.2 Bus Section 1).

    3.1.2 The 400 kV System

    The 400 kV yard will be built with tubular busbars in order to minimise the visual impact of the substation on the surrounding area as well as to coup with the amount of injected and through power the busbar systems will be required to support in the future.

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    As with the 765 kV busbar configuration, the 400kV busbar system is to depart from the conventional double busbar selection with bypass, in favour of a more reliable One-and-a-half Circuit Breaker philosophy. The system still employs two normal running busbars (No.1 and No.2), but with a three circuit breaker system servicing two circuits. This arrangement eliminates the need for the bypass facility due to the sharing of the so called Tie circuit breaker that allows automatic re-routing of power flow under live conditions if a busbar fault occurs. The arrangement inherently provides for access to all circuit breakers, which is not the case with the current double busbar selection with bypass. The possible future expansion of the Kappa 400kV system also provides for two bus sections to facilitate the removal of smaller zones of busbar for maintenance purposes. However, depending on the growth of the 400kV network, it is possible to have a staggered bus section arrangement to further improve on flexibility and security of supply, to cater for double zone outages.

    The 400kV Kappa system will be comprised of the following bays:-

    4 x fully equipped feeder bays tied back-to-back with the appropriate circuits through a Tie circuit breaker bay to provide for the 1 circuit breaker arrangement (Drorrivier 1, Drorrivier 2, Bacchus 1 and Muldersvlei 1);

    1 x fully equipped transformer bay tied back-to-back with the appropriate circuit through a Tie circuit breaker bay to provide for the 1 circuit breaker arrangement (Transformer 1);

    1 x fully equipped switch-able busbar reactor bay tied back-to-back with the appropriate circuits through a Tie circuit breaker bay to provide for the 1 circuit breaker arrangement (Busbar Reactor 11); and

    2 x partially equipped bus sections with a set of CVTs bays and isolator with busbar earth-switches each (No.1 Bus Section 1 and No.2 Bus Section 1).

    3.2 Infrastructure

    3.2.1 Description of a Substation

    The proposed substation will act as a switching station for the existing transmission lines in the Ceres area. The fact that the substation will need to act as a switching station for several existing power lines means that it needs to be situated near the convergence of these lines. Figure 1 and Figure 3 below provide an example of what a substation looks like and the proposed layout of the substation respectively.

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    Figure 1: Example of a substation

    3.2.2 Description of Associated Infrastructure

    Earthworks

    New terraces will be constructed for the 400 kV and 765kV yards.

    Main Substation Switchgear

    The term switchgear refers to the combination of electrical disconnects, fuses and/or circuit breakers used to isolate electrical equipment. Switchgear is used both to de-energize equipment to allow work to be done and to clear faults downstream.

    Power is brought to the substation on 765 kV transmission lines that end on a large steel structure called a terminal tower. Power is then transferred into the main electrical switchgear inside the substation perimeter.

    Figure 2: Example of a switchgear.

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    Figure 3: Proposed Substation Site Layout.

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    Foundations, plinths and trenches

    Main column, tubular bus, equipment foundations for the 765 kV system , 1 x 2000MVA, 765/400kV transformer plinth (3 x single phase units), 3 x 400MVAr, 765kV reactor plinths (3 x single phase units per line reactor), and cable trenches in the 765kV yard must be provided.

    Transformers

    A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors. The transformer is based on two principles: firstly, that an electric current can produce a magnetic field (electromagnetism) and secondly that a changing magnetic field within a coil of wire induces a voltage across the ends of the coil (electromagnetic induction). Changing the current in the primary coil changes the magnitude of the applied magnetic field. The changing magnetic flux extends to the secondary coil where a voltage is induced across its ends.

    MVA stands for mega-volt-ampere which in electrical terms, is the amount of power in an alternating current (AC) circuit equal to a current flow of one ampere at an electromotive force of one volt. It is equivalent to