Pre – Line Design Considerations

 Pre – Line Design Considerations

There are certain basic requirements that have to be considered when designing overhead distribution power lines. These requirements fall within the broader National Standards and Guidelines (e.g. AS 7000). This blog has been put in place to facilitate the development of innovative project designs that will aim at:

(a) Reduced cost to customers;

(b) Reduced Life Cycle ( Maintenance) costs;

(c) Greater durability with due consideration to location in a cyclonic areas;

(d) Safety of workers and the General Public;

(e) Environmental Compatibility;

(f) Electromagnetic Field Compatibility;

(g) Favorable public acceptance ( aesthetics); and

(h) Increased network safety and reliability

When the requirement for a line has been established, the following factors need to be considered before the design can commence. They are:

a) Potential number of Customers and total load;

b) Estimation of potential load growth;

c) Availability/ and or requirement for interconnections;

d) Selection of Voltage for line operation;

e) Size and location of loads (Bulk supply, transformers)

f) Selection of Route

g) Length of line

h) Life Cycle costs

Introduction to Design of Distribution Overhead Power Line

Dear Readers the following blogs will be about designing distribution overhead power lines

So be with us to learn more have a good Read!!!

General

This blog describes the engineering process involved in designing distribution overhead power lines. These lines typically originate from Zone substations as Medium Voltage lines and are stepped down to Low Voltage through distribution transformers. Low Voltage overhead power lines then transmit power from transformers to customer installations. Some customers are supplied directly from the Medium Voltage network.

Overhead Power lines account for a significant proportion of  Power networks. These assets involve large amounts of capital expenditure, both by utility Power and customers. Also, these lines need to be properly designed and constructed and it is imperative that a high level of engineering input is put into their designs, particularly because these lines may be built in cyclonic areas. Effort expended here could avoid unnecessary expenses for utility Power and customers and ensure that the customer's requirements and all of utility Power's requirements are catered for.

Each overhead line requires different design considerations, configurations, layouts, etc. As such, there may be many different ways to approach a design.

The information contained in this blog will assist the designer to develop a structured design approach, and ensure that the optimum line configuration is selected at all times.

What Is Substation?

 A substation is a high-voltage electric system facility. It is used to switch generators, equipment, and circuits or lines in and out of a system. It also is used to change AC voltages from one level to another, and/or change alternating current to direct current or direct current to alternating current. Some substations are small with little more than a transformer and associated switches. Others are very large with several transformers and dozens of switches and other equipment. There are three aspects to substations:

Figure 1. Typical substation

• Substation Types: Although, there are generally four types of substations there are substations that are a combination of two or more types.
  • Step-up Transmission Substation
  • Step-down Transmission Substation
  • Distribution Substation
  • Underground Distribution Substation
  • Substation Functions
  • Substation Equipment

Unity Power Factor

What is meant by unity power factor in electrical systems?

Unity Power Factor = 1. When the Power Factor of electrical loads is Unity or One, it means there are no reactive component in the Load like pure resistance in Incandescent Bulbs, Electric Stoves, Flat Iron, etc.

When the loads are inductive like Fluorescent Lights with Ballasts, Induction Electric Motors, etc., the Power Factor is less than Unity which may be in the range of 0+ to 0.9999+. This range of Power Factor is the Cosine of the Angle between the True Power WATTs and Active Power VA in the Power Triangle. The opposite side to the Angle represent the Reactive Load in VAR. The longer this side of VAR the poorer is the Power Factor as it approaches a Power Factor of 0+ which means the Active Power WATTs is being minimized to ZERO and no Energy or KWH is registered by the electric meter which is the basis of the Power Company to bill the consumer.

When the Power Factor of the Electric System is Unity, it means a very efficient Power Generation and Distribution System, however it is rarely achievable and nearly impossible. 

MicroGrid

 A microgrid is a small-scale power grid that can operate independently or in conjunction with the area's main electrical grid. Any small-scale localized station with its own power resources, generation and loads and definable boundaries qualifies as a microgrid.

A microgrid is an electrical system that includes multiple loads and distributed energy resources that can be operated in parallel with the broader utility grid or as an electrical island.

IEEE Std 1547.4-2011 defines Distributed Resource (DR) island systems or microgrids as Electric Power Systems (EPS) that:

(1) have DR and load,

(2) have the ability to disconnect from and parallel with the area EPS,

(3) include the local EPS and may include portions of the area EPS, and

(4) are intentionally planned.

Digital Fault Recorders (DFRs)

 

What is a fault recorder in power systems?

Digital fault recorders (DFRs) are multi-channel devices that are designed to capture and record the waveforms and sequence of events associated with power system faults. They come in many shapes and sizes and look similar to this one:

The waveforms they capture look like this:

Ground

GROUND

What Is Grounding?

The term ground has a very important and specific meaning in the context of electric circuits: it is an electrically neutral place, meaning that it has zero voltage or potential, which moreover has the ability to absorb excesses of either positive or negative charge and disperse them so as to remain neutral regardless of what might be electrically connected to it. The literal ground outdoors has this ability because the Earth as a whole acts as a vast reservoir of charge and is electrically neutral, and because most soils are sufficiently conductive to allow charge to move away from any local accumulation. The term earth is synonymous with ground, especially in British usage. A circuit “ground” is constructed simply by creating a pathway for charge into the earth. In the home, this is often done by attaching a wire to metal water pipes. In power systems, ground wires, capable of carrying large currents if necessary, are specifically dug into the earth.