Design methodology of single line diagram, general layout, switchyard layout and additional design drawings are added to the document. International standards used in the design phases are also mentioned with their requirements. The scheme adopted and other consideration necessary are:

• Design Configuration (e. g. Break and a-Half system),
• Line Bay, Transformer Bay,
• Substation Services; AC & DC Distribution Systems,
• HV & MV Cabling,
• Civil Works:Substation Buildings, Drainages, Cable Ducts, Access Roads, Equipment Foundations, etc.
• Substation Automation; control/Relay and protection equipment.
• Substation equipment testing and commissioning.
  

Installation works of Power Transformer, Switchyard Equipment & Cable Trenches are major part of construction of substations. Foundation for all equipment, which mostly spread footing, have them mounted on steel structures.

Steel structures is designed and fabricated in accordance with the requirements of IEEE specifications for structural steel building. All structures / structural foundation of outgoing and incoming lines are designed for ± 30 degree angle of deviation in horizontal plane and ± 20 degree deviation in vertical plane in conjunction with the consideration of height and type of structure provided on electrical requirements. The critical loading combination causing higher stress is considered for design of structural foundation / structures.

The substation gradation design is carried out keeping in view the proper drainage of the rain water. Standing of water after rain and entrance / drainage of water into cable trenches is avoided.

A complete road design is constructed along with pavement and geometric design prepared on the basis of topographic plan, drainage system layout and grade levels and approved prior to construction.

The substation protection philosophy is to provide accurate recognition of a fault condition and to ensure rapid isolation of faulty circuit from the system. The protection schemes have following features:
• High reliability and security
• Fast operating times
• Ability to maintain system stability

Automation, Control and Protection equipment are mainly microprocessor type. Protection system of typical substation consisting of following Equipment:
• Breaker Control and Bay control;
• Line Protection (primary & backup);
• Transformer Protection (primary & backup);
• High Impedance Busbar Protection.

In addition to Protection, specialised equipment are used to provide fully integrated system for protection, automation and control and management of event reports, settings and sequential event recorder data.

In general terms, there are Standard Process and Procedures provided for Tests and Commissioning of EHV Substation. 

Various installed equipment that forms a project are subjected to tests to ensure conformity to its functions and specifications for electrical system safety and reliability. The purpose of electrical testing on systems and their components are: 

• The first is to check the installation of the equipment and perform component and systems tests to ensure that, when energised, the system will function properly. 
• The second is to develop a set of baseline test results for comparison in future testing to identify equipment deterioration.
  

Basically, the steps involved are develop specific equipment test plan, provide inspection and checks, perform component testing, verify and check the continuity of wiring, check control functions, calibrate instruments and relays.