Introduction to Underground Systems - SaskPower 3 Book 2/1. INTRODUCTION TO... · while providing reliable power to the customer and security to the system, the operator must fully

March 31, 2005

S T U D E N T M A N U A L

Introduction to Underground Systems

Copyright 2004 by the Training and Development Centre, SaskPower. All Rights Reserved

2 S T U D E N T T R A I N I N G M A N U A L

Prerequisites: • Maps and Surveys module

Objectives: Given the Construction Standards manual, you will be able to explain the major elements of an underground distribution line design.

Rationale: Understanding underground line design is necessary before constructing and operating an underground system. This requirement ensures that an underground system is constructed safely and operated in a reliable manner.

Learning Objectives• Describe the two main types of underground line design.• Explain the advantages of an underground system.• Explain the use of cable and apparatus identification markings.• Identify the codes and symbols used for underground mapping.

Learning Methods• Self-learning + On-the-job• Self-learning + On-the-job• Self-learning + On-the-job• Self-learning + On-the-job

EVALUATION METHODS

• Written test• Written test• Written test• Written test

STUDENT RESOURCES

• Construction Standards Manual• Occupational Health & Safety Regulations

I N T R O D U C T I O N T O U N D E R G R O U N D S Y S T E M S 3


Learning Steps1. Read the Learning Guide.2. Follow the steps outlined in the Learning Guide.3. Clarify any questions or concerns you may have.4. Complete the Practice and Feedback.5. Complete the Evaluation.



Lesson 1: Types of Underground Line DesignLearning Objective:Describe the two main types of underground line design.Learning Method:Self-learning + On-the-jobEvaluation Method:Written test

Introduction

SaskPower employs two types of systems with regards to the design ofunderground distribution. These types of systems are commonlyreferred to as:

• Radial system• Loop system

Radial

A radial circuit consists of a feeder capable of supplying power from oneend only. This type of feed is susceptible to relatively long interruptionsin the event of cable faults.

The radial system is the simplest and lowest cost alternative and can beboth single-phase or three-phase.



Loop System

The primary loop system is designed to provide an alternate source ofpower in the event of a fault, thus improving the reliability of the system.

Simply stated, the loop system consists of a circuit which runssuccessively to one or more individual loads and is then returned to itssource or another supply point.



This loop system provides supply options when a fault occurs on a lineor when a piece of line requires isolating for whatever reason. Thecircuit shown above is typical of that used in underground distributionsystems. It illustrates a loop circuit being fed from each end, with anormal open (N/O) in the centre.

By using a normal open, if a fault did occur in the loop, only one half ofthe circuit would experience a power outage. Also, the outage timewould be shorter than in a radial feed. With some relatively simpleoperating, the N/O could be closed to re-energize the part of the systemaffected. The normal open also enables the balancing of load, therebyoffering better voltage regulation to customers.



Lesson 2: Advantages of UndergroundLearning Objective:Explain the advantages of an underground system.Learning Method:Self-learning + On-the-jobEvaluation Method:Written test

Introduction

Even though underground distribution systems are more expensive thana comparable overhead system, there are many areas whereunderground is the preferred method of supplying power. This is due tothe numerous advantages an underground system possesses.

These advantages include:

• reduced line loss• far less danger to the public in comparison to the overhead system

(pole hits, high voltage line contacts)• more aesthetically pleasing• reduced maintenance costs• less susceptible to outages• much easier for farmers and landowners in their day to day

operations, with regards to pole obstructions



Lesson 3: Cable and Apparatus Identification MarkingsLearning Objective:Explain the use of cable and apparatus identification markings.Learning Method:Self-learning + On-the-jobEvaluation Method:Written test

Introduction

Underground primary systems use a variety of apparatus, devices andcables.

There are times when construction, maintenance or trouble shooting ofthe system is required. In order to carry this out safely and efficiently,while providing reliable power to the customer and security to thesystem, the operator must fully understand each step which needs to betaken to complete the task at hand. For this reason, a standard systemfor marking and identifying all apparatus, devices and cables must beused.

At SaskPower, there are two types of underground systems: ruralunderground distribution (RUD) and underground residentialdistribution (URD). Apparatus, devices and cable identificationmarkings differ between RUD and URD, so we will look at themseparately.

Rural Underground Distribution (RUD)

All RUD apparatus, devices and primary cable ends are identified withan eight character number.

Apparatus/Devices

All apparatus and devices such as padmounted or pole mountedtransformers, reactors, switching cubicles, and cable take-off structuresare labeled with an identification number.

In any section, the first apparatus or device is labeled A, the second Band so forth. Each will be followed by section, township, range (allthree are two digit numbers) and meridian (one digit). A single digitsection, township or range shall be preceded by a zero. For example,A0306092 is device A, in section 03, township 06, range 09, west of the



second meridian.

On construction maps, device identification is shown with a rectangle.

Primary Cable

Each end of every primary cable is identified with a tag indicating wherethe other end of the cable is terminated. For example, in section 14,device B, the cable with A1403132 tag is connected in section 14,device A. The cable with A1503132 tag is connected to the device insection 15, device A.

Underground Residential Distribution (URD)

All URD apparatus and devices are given a code number which must bedisplayed (designated by the area operating staff).

The inside of the door or hood is marked with permanent marking(yellow grease pencil or other permanent marking) to show the directionof cable feeds, normal opens or take-offs, if applicable. In three-phaseapplications, cables must also be marked using red, yellow, or bluephasing tape.

Reference

For additional information, refer to Drawing B-30-26 of theUnderground Construction Standards manual.

Reference

For additional information on primary cable, refer to DrawingB-30-26 of Underground Construction Standards manual.





Lesson 4: Underground MappingLearning Objective:Identify the codes and symbols used for underground mapping.Learning Method:Self-learning + On-the-jobEvaluation Method:Written test

Introduction

Before completing switching, become familiar with the undergroundsystems with regards to codes and symbols and how apparatus is labeledon the maps. Without knowledge of the mapping system, a switchingplan is almost impossible to employ.

Reading and understanding maps is a requirement when operating anunderground system. As well, the drawing of maps or asbuilts may berequired. Again, the current underground distribution codes andsymbols are a must.

When drawing a map, there are five points to keep in mind:

• Keep pertinent records• Keep the records clear• Keep the records concise• Keep the records on a minimum number of sheets• Keep the records up to date

Doing the above helps to:

• Assist in locating faults in the system at a later date (location of splices)

• Facilitate the locating of installed equipment

Reference

For further information on codes and symbols, refer to SectionB-02 in the Construction Standards manual.



• allow field personnel to intelligently design future extensions or additions to existing facilities

Underground asbuilts should include the following information:

• distance from the centre line of the trench to the property line, as well as measurements to permanent objects (measurements from power poles and other moveable objects should be avoided if possible)

• type, size, and quantity of wire in the trench• deviations from the original design• location of splices (a high percentage of primary cable failures occur

at the splice)• an accurate measurement of the cable length• location of spare duct, if any• transformer code numbers• location of cable markers which may assist in the locating of cables• directional indicator

---Note---Asbuilts must be completed and submitted to drafting as early aspossible to keep the system maps up-to-date.



Summary

To summarize this module, you have learned:

• Two main types of underground line design.• The advantages of an underground system.• The use of cable and apparatus identification markings.• To identify the codes and symbols used for underground mapping.

Practice Feedback

Review the lesson, ask any questions and complete the self-test.

Evaluation

When you are ready, complete the final test. You are expected toachieve 100%.



Review Questions

T / F 1. A radial system has one source of feed.

T / F 2. A radial system has a source of feed and an alternate source of feed.

T / F 3. A loop system has one source of feed.

T / F 4. A loop system has a source of feed and an alternate source of feed.

T / F 5. A loop system commonly has a normal open in the system.

T / F 6. A radial system commonly has a normal open in the system.

T / F 7. A radial system is susceptible to relatively long interruptions in the event of a cable fault.

T / F 8. A loop system is susceptible to relatively long interruptions in the event of a cable fault.

T / F 9. Underground distribution systems have lower maintenance costs than overhead distribution systems.

T / F 10. Underground distribution systems are cheaper to install than overhead distribution systems.

T / F 11. Underground distribution systems are more dangerous to the public because they can’t be seen as easily.

T / F 12. An underground system is advantageous because it has less line loss than an overhead line.

T / F 13. An underground system is more susceptible to outages.

T / F 14. All RUD apparatus, devices and cable ends shall be identified with an eight character number.

T / F 15. All URD apparatus and devices are given a code number.



T / F 16. Phasing tape must be used in all single-phase RUD applications.

17. The symbol shown indicates a:

(a) 100kVA transformer.(b) 100kVar reactor.(c) 100 amp switch.(d) 100 foot pole.


(a) Grain bin.(b) Three-phase transformer.(c) Switching kiosk.(d) Splice.


(a) Splice.(b) Secondary cut.(c) Switch.(d) Streetlight.


(a) Cutout.



(b) Stop sign.(c) Reactor.(d) Cable marker.


(a) Cable marker.(b) Reactor.(c) Splice.(d) Switching kiosk.


(a) Primary take-off.(b) Streetlight.(c) Cutout.(d) Reactor.

23. Keeping good asbuilts helps to:(a) Assist in locating faults in the system at a later

date.(b) Facilitate the locating of installed equipment.(c) Allow field personnel to intelligently design future

extensions or additions to existing facilities.(d) All of these



Review Question Solutions

1. T

2. F

3. F

4. T

5. T

6. F

7. T

8. F

9. T

10. F

11. F

12. T

13. F

14. T

15. T

16. F

17. 100kVar reactor.

18. Three-phase transformer.

19. Splice.

20. Cutout.

21. Cable marker.

22. Primary take-off.



23. All of these

Documents

Introduction to Underground Systems - SaskPower 3 Book 2/1. INTRODUCTION TO... · while providing reliable power to the customer and security to the system, the operator must fully