Electrical Substation and Switchyard Design

THE WORKSHOP

Electrical substations form important nodal points in all power networks. Substations can be of various capacities, voltages, configurations and types depending on what is the application for which the substation is being designed. Location and layout of a substation present a number of challenges to the designer due to a large variety of options available to a designer. There are ever so many constraints too that need to be kept in mind; technical, environmental and naturally financial. Arriving at an optimum design within these constraints is as much an art as it is a science. Designing a substation which will operate with utmost reliability for at the least three or four decades involves a thorough knowledge of the current state-of-the art equipment, emerging technologies, the tools for presenting and evaluating all available options and a good appreciation of power system operation and maintenance. This course will present a comprehensive capsule of all the knowledge essential for a substation designer and walk the participants through the substation design process using a set of interlinked case studies.

WHAT IS INCLUDED?

  • Receive a certificate of attendance in support of your continuing professional commitment
  • All workshops include the associated hardcopy technical manual
  • Printed workshop handouts
  • Lunch and refreshments
  • Interact and network with workshop attendees and experienced instructors
  • Practical, industry driven content to assist you in your continuing professional development (CPD)
  • Attendees automatically become IDC subscribers and receive exclusive deals and technical content every month

WHO SHOULD ATTEND?

This course is aimed at engineers who are already working as electrical system designers as well as those who belong to any of the fields listed below and wish to prepare themselves for moving into the role of a substation designer.

  • Utility engineers dealing with power transmission and distribution systems
  • Electrical engineers involved in power generating plants with utility scale generators
  • Electrical engineers in large industries who are associated with power distribution
  • Consulting engineers involved in design of substations
  • Contractors executing projects involving electrical HV substations
  • Electrical commissioning engineers

COURSE SUMMARY

ROLE OF SUBSTATIONS IN AN ELECTRICAL NETWORK, TYPES AND CONFIGURATIONS OF SUBSTATIONS

  • Networks-an introduction
  • Different voltages in a network
  • Substations as network nodes
  • Substation types based on their position in the network
  • Optimising the location of a substation
  • Substation options: Outdoor air insulated, GIS, Indoor air insulated
  • Configurations of HV substations based on their bus arrangement (typical SLD)
  • Data on the industrial loads required for the design of the electrical supply substation
  • Load assumptions for residential and commercial consumers
  • Environmental issues in the location of a switchyard and mitigation measures

Case Study Part-1

An electrical supply network is being extended to feed a new metallurgical industrial facility along with a residential township for people expected to be employed in the industry and its support facilities. The industries and residential premises will be fed at different voltages from a new substation with an outdoor switchyard. The first part of the study will be to generate a list of data to be obtained from the prospective consumers regarding the industrial loads.

Participants will then be required to work out an optimised location for the substation depending on the details obtained and also work out an appropriate substation configuration in form of a single line diagram. This hypothetical switchyard will form the basis of all subsequent case examples.

SYSTEM STUDIES REQUIRED FOR FINALISING EQUIPMENT RATINGS

  • Load flow study (active/reactive loads)
  • Short circuit study
  • Harmonic flow
  • Voltage profile and reactive power compensation
  • Stability study

Note: The objective/relevance of each of these studies to the substation equipment selection and specifications, the inputs required and outputs expected will be covered in this section. A broad overview of the studies will be provided without going into the actual calculations involved.

Case Study Part-2

The participants will compile a list of data needed to make the studies in the context of the hypothetical switchyard, the necessary formats for presenting the information, the different cases to be covered in each of the studies and finally the list of the outputs required to finalise equipment specifications.

OVERVIEW OF SWITCHYARD EQUIPMENT AND THEIR ORDERING SPECIFICATIONS

  • Main (primary) equipment
    • Busbars
    • Disconnectors
    • Circuit breakers
    • Instrument transformers
    • Lightning arrestors
    • Power transformers
    • Structures
  • Layout options
  • Sectional and Safety clearances and their influence on the layout
  • Design of busbars (strung/tubular) and interconnections between equipment
  • Interconnecting cables and use of marshalling kiosks

Case Study Part-3

The main equipment specifications required for the switchyard (transformers, disconnectors, CT/VT and circuit  breakers) will be finalised based on the configuration selected in case study part 1 and the studies mentioned in part 2. Details of bus conductors and insulators will be worked out. The layout of a typical bay will be developed showing all the equipment in plan and sectional views and the available clearances.

SUBSTATION EQUIPMENT FOR FAULT LIMITING, PFC AND HARMONIC CONTROL

  • Need for and application of:
    • Fault limiting reactors
    • Power factor compensation equipment
    • Static VAR compensators
    • Harmonic filters
  • Equipment design and selection of ratings
  • Layout of these equipment in a switchyard

Case Study Part-4

Based on available data, the participants will decide the parameters of equipment required for fault limiting, PF compensation and harmonic control as applicable and then work out the space requirements and possible location. The SLD and layout will be updated to include the above equipment.

PROTECTION DESIGN FOR SUBSTATION

  • Brief overview of protection
  • Over current protection
  • Protection coordination
  • Protection of transformers
  • Busbar protection
  • Feeder protection
  • Current transformers requirements for protection
  • Equipment requirements for substation automation
  • PLCC applications in protection and communication
  • PLCC hardware and integrating them with the switchyard equipment

Case Study Part-5

Based on available data, the participants will decide the protection requirements for the switchyard and its incoming and outgoing feeders and incorporate them in the single line diagram by showing the protective functions for each circuit and the busbars. A brief specification of the relays required taking into consideration the need for interfacing between the protection and substation automation will be framed.

The settings for current relays in the substation required to achieve coordinated operation will be worked out. Current transformer specifications for adequacy of protection will be reviewed based on CT burdens and relay settings.

EARTHING SYSTEM AND LIGHTNING PROTECTION OF SWITCHYARDS

  • Basics of functional and protective earthing
  • Touch and step voltages in substations
  • Earth grid and its role in safety
  • Switchyard fence-why it should be a part of the earth grid
  • Design of earth grid-basic considerations in conductor sizing and mesh spacing
  • Pros and cons of including the control building within the  switchyard earth grid
  • Earth mat laying and welding
  • Safety mesh at operating points
  • Role of gravel layer in safety
  • Transferred voltage hazards
  • Planning isolation of outgoing services to avoid transfer voltage
  • Basics of lightning and hazards
  • Role of shield wire and lightning masts
  • Typical configurations of lightning protection of switchyards
  • Analysis of hazard using cone of protection and rolling sphere methods
  • Selection of lightning arrestors-Types, class and ratings

Case Study Part-6

Based on available data, the participants will calculate the size of earth conductors and earth mesh spacing and superimpose the earth grid on the layout to make necessary adjustments. Using the rolling sphere method, the height, spacing and number of lightning masts to protect the switchyard equipment from direct lightning strikes will be calculated. Sketches showing the adequacy of protection offered by the lightning masts will be developed.

The points for location of lightning arrestors and mounting options will be determined and. the arrestor specification finalised.

SWITCHYARD CONTROL AND INTERLOCKING

  • Dc power requirements for switchyard equipment
  • Dc equipment configuration and specifications
  • Dc distribution for switchyard equipment
  • Battery calculations basis
  • Space planning and related facilities for a battery installation
  • Ac auxiliary power for switchyard systems-loads which require ac power
  • Possible source options
  • Ac auxiliary distribution for switchyard equipment and support systems
  • Control scheme of disconnectors and circuit breakers
  • Control interconnection approach
  • Use of optical fibre-based control scheme
  • Role and location of marshalling kiosks in different bays

Case Study Part-7

For the hypothetical switchyard a design document will be prepared to outline the control requirements, source, basis of sizing, a block diagram showing copper and optical fibre connections.

A cable trench layout for routing of auxiliary power, control and optical cables will be superimposed on the switchyard layout.

SWITCHYARD-FACILITY PLANNING

  • Site preparation, levelling
  • Earth resistivity measurement and its role in design verification
  • Civil works such as equipment foundations, cable trenches, control building, storm drains, transformer oil collection pit
  • Structures and their design requirements
  • Substation fence and physical security
  • Surveillance
  • Planning water requirements and supply arrangement
  • Fire protection, lighting and ventilation of control room and other equipment

Case Study Part-8

For the hypothetical switchyard a design document covering access security, fire protection, lighting and ventilation requirements for the switchyard and its control building will be prepared. A complete layout will be sketched showing the entire switchyard with fencing, space allocations of the feeder bays, transformers and other equipment for current limiting, pf compensation etc.

GAS INSULATED SWITCHGEAR (GIS) AS AN ALTERNATIVE TO OUTDOOR SWITCHYARD

  • Why gas insulated substation?
  • SF6 properties, advantages and environmental impact
  • Typical substation configurations in SF6
  • Indoor/outdoor options
  • Gas safety considerations
  • Equipment for handling SF6
  • SF6 substation layout planning
  • Cable terminations to SF6 equipment

Case Study Part-9

Reconfigure the hypothetical switchyard using a GIS alternative and work out a revised layout using indoor GIS equipment housed as an adjunct to the control building.

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