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Home / Technical Articles / Substation design choices and reasons for a new modern vs retrofit and upgrade an old one

Grid expansion and old substations

This technical article addresses some of the most important reasons, dos and don’ts in making the substation design choices between designing a new modern and digital substation or retrofitting the existing one and upgrading its aging assets. We’ll discuss pricing and factors influencing the price, substation safety concerns and conflicts in design decisions.

Substation design choices and reasons for a new modern vs retrofit and upgrade an old one
Substation design choices and reasons for a new modern vs retrofit and upgrade an old one

However, we must start from the point when it all started, and that’s around 140 years ago. The power grid was initially developed in the 19th century and underwent significant expansion throughout the 20th century. The National Academy of Sciences, acknowledging the grid’s complexity and importance, has designated it the largest “machine” in the world and ranked it at the top of the list of the most significant engineering accomplishments of the 20th century.

The difficulty that will be faced in the future by electricity systems is to keep the reliable and secure operation of this ever-expanding yet already complex machine.

The majority of advancements in electricity systems have been driven by needs in technology, the economy, and society. And in recent times, a significant amount of focus has been placed on the utilization of renewable energy supplies as well as the electrification of transportation, all of which influence the progression of the grid’s future development.

As a consequence of this, grid expansion is required; yet, the difficulties associated with maintaining reliability and safety in a networked globe also increase. This issue was brought to light over the course of the previous decade by a series of extensive power system failures that had a significant influence on the economy as well as the lives of people living in both industrialized and underdeveloped nations.

The substation, which is essential to the monitoring, control, and protection of the power system, is the target of many upgrades that aim to increase flexibility, increase dependability, and reduce the overall cost of the system over its lifecycle. It is the responsibility of the substation to connect significant components of the power system, such as transmission lines and power transformers, and to route power from one line to the next. In this way, the substation makes it possible for electric power to travel from the site of generation to the end users of the power.

Substations utilize power transformers to modify the voltage level between the transmission line and other sections of the system, such as distribution and generation, in order to reduce line losses. This is one of the many ways that substations work to accomplish this goal.

Substations feature switching devices (circuit breakers, disconnectors, switch-disconnectors, earthing switches, fuses, etc.), which are used to separate elements of the power system that have experienced problems. In addition, substations contain other control equipment, such as protective relays and voltage regulators.

This brings us to our last point.

Figure 1 – Single line diagram of a 33/11 kV power distribution substation

Single line diagram of a 33/11 kV power distribution substation
Figure 1 – Single line diagram of a 33/11 kV power distribution substation (click to expand the diagram)

Substations contain HV equipment, which is also commonly referred to as power apparatus or the primary equipment, as well as low-voltage monitoring, control, and protection equipment, which is typically referred to as secondary equipment. This allows substations to execute all of these functions.

The two different kinds of equipment are connected to one another in the same physical location; the main equipment can be found in the switchyard of the substation, and the secondary equipment can be found in a control house.

Just to mention that substations can range from a few hundred thousand dollars to tens of millions of dollars in price depending on their size, as well as the voltage levels they support.

Ok, let’s discuss each of the below factors which can influence substation design choices.

Table of Contents:

  1. Difficulties in Substation Design
  2. Various Aspects of Substation Price
  3. Advances in Technology
  4. Concerns Regarding Substation Safety
  5. Conflicts in the Substation Design
  6. Approaches to Future Substation Design
  7. BONUS: Substation Automation Systems Design & Implementation (PDF)

1. Difficulties in Substation Design

An examination of the requirements for substation design can illustrate the advantages of making improvements to substations. Because such design elements result in direct savings in money, it is important to highlight that cost, dependability, operational flexibility, and environmental effect give the greatest possibilities to enhance the design in order to get the largest returns on investment.

This is because improving the design in these areas results in the most opportunities.

The most important requirement is to offer integration along three major design goals, which are the application of enhanced design criteria, the utilization of cutting-edge technology, and the capacity to update in meaningful deployment stages. The obstacles that need to be overcome in order to attain enhanced design requirements include achieving numerous design aspects, such as operational flexibility and reliability, while simultaneously lowering costs and making the design interoperable.

Even while advanced technologies are easily accessible, it may not be simple to incorporate them into the design that is already in place because of fundamental incompatibilities. This underlines how difficult it is to continue in stages that allow both the upgrade of existing systems and the introduction of new designs in substations that are being built.

Figure 2 – Maintenance engineer standing in front of an advanced digital switchgear

Maintenance electrical engineer standing in front of an advanced digital switchgear
Figure 2 – Maintenance electrical engineer standing in front of an advanced digital switchgear

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2. Various Aspects of Substation Price

Taking costs into consideration is not a straightforward process because there are so many variables involved. Where exactly, in terms of both electrical and geographical location, is the substation situated? The substation’s relevance in terms of dependability of power system operation and environmental considerations, both of which can have a potentially enormous impact on costs, is determined by its placement.

How long has the substation been in operation? In general, the cost of upgrades will increase proportionately with the age of the legacy substation design. In order to obtain more operational flexibility, older substations may require not only a retrofitting, but also an improvement in the monitoring of their aging assets.

When a power delivery deal is made through the market, what role does the substation play in getting the power to the customer? Some substations have more complex connections to the transmission lines that are part of the system, which makes them potentially a large bottleneck and risk for the transfer of power among the connecting lines.

This can have a significant effect on the system’s reliability as well as the cost of operating the system. The improvement of such substations typically results in a greater return on the investment.

Figure 3 – An older power substation that needs upgradation

An older power substation that needs upgradation
Figure 3 – An older power substation that needs upgradation

When it comes to operations in the past, what kind of experience have you had? If a substation has had consistent problems with maintenance and reliability, it may be easier to justify the cost of updating it because a history of high expenses can be established. However, this justification will not apply to all substations. You absolutely must take the big picture into consideration.

Most contemporary substations are outfitted with more cutting-edge equipment, some of which is extremely reliant on rapidly advancing technologies like IoT, sensors, and various  relatively newly developed communications protocols.

These aspects unquestionably have an effect on the total cost of substation ownership over its entire existence, given that subsequent modifications could end up costing as much as the initial design did, and that such costs could become prohibitive in the future if they are not well handled.

In a similar vein, designs that do not allow for simple upgrades run the risk of producing stranded assets that will be difficult and expensive to replace in the future. These are very bad designs and should be avoided.

Good Reading – What will happen to digital substations once the internet drops dead?

What will happen to digital substations once the internet drops dead? Massive blackouts?

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3. Advances in Technology

In most cases, the technology for upgrading substations is well ahead of the capabilities of those who utilize the substations to make full use of the benefits offered by the technology. Typical examples include brand-new sensors and very clever electronic gadgets, all of which have the potential to give significant advantages in terms of increasing operational flexibility, reliability, and safety but also increase complexity and make it much harder to troubleshoot.

The rewiring of the substation, specifically the transformation of copper wires into multiplexed optical cables, is the primary area in which cost reductions can be made during substation upgrades. You can obtain a large cost advantage with optical sensors by directly transferring all measurements in digital form from the source to the destination using either optical or copper connection.

This can be accomplished by a direct transfer of all measurements.

When looking at the primary equipment, there are currently many new power apparatuses accessible to boost operational flexibility and fulfill needs for greater power throughput and improved controllability. These power apparatuses are available for some time now. For example, you can reduce the risk of environmental pollution and fire threats by using modern power transformers of the dry-type variety.

A static compensator is a regulating device that can either be a source or a sink of reactive power and, as a result, can be used to control the flow of power. It is also known as a “static synchronous condenser”, another name for this type of device.

In addition to its application for relieving congestion on transmission lines, the control device for the Flexible Alternating Current Transmission System (or FACTS) can also be put to use to control the flow of power.

Figure 4 – Flexible Alternating Current Transmission System (FACTS)

Flexible Alternating Current Transmission System (or FACTS)
Figure 4 – Flexible Alternating Current Transmission System (or FACTS)

Instrument transformers, such as voltage and current transformers used for relaying and revenue metering, may reduce the high-level voltages and currents from the power apparatus down to the low-level voltages needed by the control and measurement equipment.

This is accomplished by transforming the high voltages and currents into a lower level of energy.

Suggested Reading – Never underestimate how important it is to choose the right CT size in fault detection and protection

Never underestimate how important it is to choose the right CT size in fault detection and protection

Without the need for any isolating or auxiliary transformers, electronic instrument transformers may make use of electronic components and link directly to the fiber-optic cables in order to transport measurements from the substation switchyard to the control house.

The majority of the time, batteries are used to store energy; however, alternative technologies, such as ultracapacitors, may also be utilized. It is possible to utilize video cameras and infrared cameras to monitor the security perimeters of the substation. These cameras can also be used to watch potential heat sinks that could indicate potential equipment breakdowns.

Figure 5 – Substation battery room

Substation battery room
Figure 5 – Substation battery room

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4. Concerns Regarding Substation Safety

However, open-air substation designs that are exposed to the outdoors are also susceptible to malfeasance because it is quite simple to assault them and cause damage to them. When you take into consideration the cyber vulnerability that is exposed by the remote access to the all-digital secondary equipment in the substations, you will see that you need to exercise extra caution in order to protect this essential combination of physical and digital infrastructure for the power system.

In spite of the fact that a cyber attack might be neutralized with an efficient information technology solution, there is still a problem with the perimeter security of substations because they are visited by a wide variety of utility maintenance and technical support workers.

Figure 6 – 1 ½ circuit-breaker hybrid switchgear installation with PASS modules for Un to 550 kV

1 ½ circuit-breaker hybrid switchgear installation with PASS modules for Un to 550 kV
Figure 6 – 1 ½ circuit-breaker hybrid switchgear installation with PASS modules for Un to 550 kV

The introduction of a compact hybrid substation design is one approach that may be taken to lessen the susceptibility of a substation to physical assaults. With this design, the wiring of the power apparatus is less exposed, the circuit breaker and measuring transformers are enclosed, and the control building is where the secondary equipment is located.

Good Reading – Should we be concerned about the cybersecurity of modern digital substations?

Should we be concerned about the cybersecurity of modern digital substations?

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5. Conflicts in the Substation Design

A notable challenge arises from the need to simultaneously optimize the flexibility and complexity of substations, while adhering to rigorous placement permissions and environmental regulations. This frequently results in the development of designs for compact spaces, such as underground sheds or the lower levels of tall structures.

In order to get such designs, it may be necessary for the builder to employ a gas-insulated substation (GIS) utilizing sulfur hexafluoride (SF6) gas.

SF6 is the most potent greenhouse gas despite being an inert, harmless, colorless, odorless, and nonflammable gas. It is approximately five times as dense as air and gives two to three times the insulating properties of air at the same pressure.

The majority of the time, a GIS is utilized in locations where space is either too expensive or unavailable, or in places where the surrounding environment requires a protected enclosure from severe weather or surroundings.

Figure 7 – Gas-Insulated Switchgear (GIS)

Gas-Insulated Switchgear (GIS)
Figure 7 – Gas-Insulated Switchgear (GIS)

The issue of design conflict is also present in the mitigation of many factors such as power transformer noise, vibrations, and fire dangers. These factors often necessitate the confinement of equipment in isolated locations. However, achieving this confinement may require a more expensive strategy in order to ensure that the substation equipment can fit into dedicated enclosures or building structures while maintaining compactness.

Managing substations in rural locations is comparatively more convenient due to less rigorous space and environmental constraints. The accessibility of open-air substations with exposed equipment contributes to cost reduction in terms of equipment and maintenance techniques.

Suggested Guide (PDF) – Design Guide for Rural Power Substations

Design Guide for Rural Power Substations

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6. Approaches to Future Substation Design

Electric utilities may explore four distinct design methods and approaches when planning for the future, in order to effectively address diverse scenario requirements and accommodate developing needs. Let’s say a word about each approach.


Approach #2 – Keep the most of substation design as it is now

Select the most critical design requirements that must be satisfied right away. As the primary aging equipment needs to be monitored, this is typically the least expensive solution that will yield a return on investment through a longer lifespan for that equipment.


Approach #2 – Modernize an older substation design

This inquiry pertains to the projection of the most significant requirements that will be prevalent in a timeframe spanning 5 to 10 years in the future. To achieve an enhancement in operational flexibility, dependability, and security, a significant upgrade of the secondary equipment will be necessary for this design.

This upgrade will result in the incorporation of value-added applications, thereby ensuring a return on investment.

In order to achieve this objective, it is imperative to conduct a thorough examination of emerging technologies and do a detailed evaluation of their costs and benefits.

Special attention should be directed towards the utilization of wireless and optical fiber connection mediums during the incorporation of new equipment and the implementation of software integration for data management.

Figure 8 – IoT in power substations

IoT in power substations
Figure 8 – IoT in power substations

Approach #3 – Construct a new substation using the latest design

This approach would look at the replacement strategy that would occur within the next 20-40 years by assuming certain regulatory and technological improvements will take place. This design has the potential to push more power through the system in a more reliable manner, which will generate a return on the investment.

This strategy calls for a field implementation that is distinct from the standard procedure, and it is predicated on the availability of newly created software modules for the purpose of data gathering and information extraction.

It will contain new communication infrastructure to facilitate the exchange of information with control systems and nearby substations. Additionally, it will support the utilization of power flow controllers of various designs.

Good Reading – Design process for the new primary substation (structure selection and calculations)

Design process for the new primary substation (structure selection and calculations)


Approach #3 – Design modern substation from scratch

Attempting to forecast the design technologies and operational practices that would incorporate legislative limitations for environmental adherence over a span of 50 years is considered the most precarious technique. The primary basis for the return on investment of this design is regulatory and environmental factors. In the future, the proposed system will incorporate two innovative technologies, namely high temperature superconductor cable and solid-state transformers.

Additionally, an intelligent economic alarm processor will be integrated, merging the assessment of physical asset condition with the functionality of the electricity market. This has a potential for enhancing the correlation between market activity and the physical system in real-time, as well as facilitating the dissemination of such information among market players.

Future “intelligent” substations are expected to assume a significant role within the broader context of the smart grid, as they possess the capability to furnish pertinent information.

Figure 9 – Tests of the first phase of superconducting fault current limiter SuperOx at the Korean Electrotechnology Research Institute (KERI)

Tests of the first phase of superconducting fault current limiter SuperOx at the Korean Electrotechnology Research Institute (KERI)
Figure 9 – Tests of the first phase of superconducting fault current limiter SuperOx at the Korean Electrotechnology Research Institute (KERI)

The forthcoming designs of substations will be founded upon the utilization of superconducting technology, resulting in increased costs attributed to the implementation of a sophisticated insulation coordinating system.

The notable characteristics will encompass the following:

  • Superior efficiency in both transmission and distribution;
  • Boosted quality, dependability, and adaptability
  • Size reduction (between 50 and 70 percent);
  • Improved safety allows placement closer to loading docks; and
  • Improved visual appeal
One of the primary areas where cost reductions can be achieved in substation modifications pertains to the wiring infrastructure, specifically through the transition from copper wires to multiplexed optical connections.

Contemporary substations are equipped with sophisticated equipment, a portion of which relies heavily on dynamic technological advancements, including computers, sensors, and communication systems.

The substation, being the central component for power system monitoring, control, and protection, has garnered significant attention for its potential enhancements in terms of enhanced flexibility and heightened reliability.

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Suggested Course – Course to Relay Circuitry and Understanding Control and Protection Schematics

Course to Relay Circuitry and Understanding Control and Protection Schematics


7. BONUS: Substation Automation Systems Design & Implementation (PDF)

Download Substation Automation Systems Design & Implementation in PDF format (for premium members only):

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Resources:

  • Fundamentals of Modern Electrical Substations by Boris Shvartsberg, Ph.D., P.E., P.M.P.
  • The substation by Mladen Kezunovic
  • Transmission and Substation Design and Operation – Technical Papers – TSDOS
  • GIS substations by H. J. Koch
  • Gas Density Monitoring System (GDM) by Siemens
  • A Study on The Development of a Novel Coupler for GIS PD Detection by Jaegu Choi, Kwanghwa Kim, and Iksoo Kim

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Edvard Csanyi - Author at EEP-Electrical Engineering Portal

Edvard Csanyi

Hi, I'm an electrical engineer, programmer and founder of EEP - Electrical Engineering Portal. I worked twelve years at Schneider Electric in the position of technical support for low- and medium-voltage projects and the design of busbar trunking systems.

I'm highly specialized in the design of LV/MV switchgear and low-voltage, high-power busbar trunking (<6300A) in substations, commercial buildings and industry facilities. I'm also a professional in AutoCAD programming.

Profile: Edvard Csanyi

One Comment


  1. Zakari Garba
    Apr 13, 2024

    I have a really appreciated to joint the group of electrical engineering systems

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