SA/SNZ HB 119:2019

Handbook

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[Current]

The objective of this Handbook is to provide a framework for the development and implementation of electrical protection at mines and quarries, thereby assisting electrical engineers tasked with protection of people and property from hazards occurring during electrical equipment failure at a mine.

Published: 20/12/2019

Pages: 208

Table of contents

Cited references

Content history

Table of contents

Header

About this publication

Preface

Introduction

1 Scope and general

1.1 Scope

1.2 Objectives

1.3 Referenced documents

1.4 Terms and definitions

1.5 Obligations

1.5.1 General

1.5.2 Detailed obligations

1.6 Abbreviations

2 Protection principles

2.1 General

2.2 Objectives

2.3 Safety

2.4 Primary system design and protection design

2.5 Key principles

2.5.1 General

2.5.2 Primary protection

2.5.3 Back-up protection

2.5.4 Fault clearance times and thermal limits

2.5.5 Fault clearance times and system stability

2.5.6 Fault clearance times and safety

2.5.7 Limitation of damage at fault location

2.5.8 Continuity of supply

2.5.9 Protection power supplies

2.5.10 Reliability of protection function

2.6 Further principles

2.6.1 General

2.6.2 Electrical interference

2.6.3 Protection against overloading

2.6.4 System state after protection operation

2.6.5 Circuit breakers

2.6.6 Proving of function

2.6.7 Validation of settings by injection

2.6.8 Avoiding common mode failures

2.6.9 Isolating facilities

2.6.10 Functional proving

2.6.11 Balancing of differential protection schemes

2.6.12 Directional testing and proving

2.6.13 Protective earthing

2.7 Batteries and DC supplies for protection — Principles

2.7.1 Independence from the power system protected

2.7.2 Voltage range

2.7.3 Battery capacity

2.7.4 Duplication and independence of battery and tripping supplies

2.7.5 Additional considerations

2.7.6 Capacitor trip units

2.8 Segregation of protection

2.9 Blind spots

2.10 Fuses or circuit breakers

2.10.1 Fuses

2.10.2 Circuit-breakers

2.11 “Open circuit” type faults

2.12 Arc energy

2.12.1 General

2.12.2 Determination of arc energy

2.12.2.1 General

2.12.2.2 Fault current

2.12.2.3 Time (duration of fault)

2.12.2.4 Arc voltage

2.12.2.4.1 General

2.12.2.4.2 Arc voltage in air

2.12.2.4.3 Arc voltage in oil

2.12.2.4.4 Arc voltage in SF6

2.12.3 Arc energy magnitude

2.12.4 Transformer tank rupture

2.12.5 Primary and back-up protection fault clearing times and arc energy

2.12.6 Low voltage arcing faults

2.12.7 Review of consequences of arcing faults

2.13 Delta-star transformation

3 Primary supply system

3.1 General

3.2 Single line diagram (SLD)

3.3 Fault study

3.4 Settings of all devices

3.5 Limitation of cable length

4 Distribution to mining plant and equipment

4.1 Earthing systems

4.1.1 General

4.1.2 IT — Network with impedance earthed source

4.1.3 Primary objectives of an IT earthing network

4.1.4 IT — Network with unearthed source

4.1.5 TN — Network with solidly earthed source

4.1.6 Earthing of 240 V supplies

4.2 Protection schemes

4.2.1 General

4.2.2 Protection devices

4.2.3 Directly supplied low voltage control circuits

4.3 Personnel protection

4.3.1 Direct contact

4.3.2 Indirect contact

4.3.3 Toroidal earth leakage for indirect contact protection

4.3.4 Capacitive coupling and inductive coupling voltage rise minimization

4.4 Residual voltage

4.5 Cross country faults in it networks

4.6 Earth protection scheme

4.7 Earth fault protection conforming with AS/NZS 2081

4.7.1 General

4.7.2 Earth fault current-limiting devices

4.7.3 Earth continuity protection devices

4.7.4 Earth leakage protection devices

4.7.5 Earth fault lockout protection devices

4.7.6 NER integrity protection devices

4.7.7 Frozen contact (failure to trip) protection devices

4.8 Insulation monitoring devices on unearthed elv ac networks in underground coal operations

4.9 Equipment protection

4.10 Fault overcurrent or short circuit protection

4.11 Hazardous area electrical supplies

4.12 Reclosing and autoclosing

5 Protection schemes

5.1 General

5.2 Overcurrent schemes

5.2.1 Timed overcurrent using inverse type time-current characteristics

5.2.2 Definite time overcurrent

5.2.3 Instantaneous overcurrent (high set)

5.2.4 Thermal — Magnetic circuit-breakers and their electronic equivalent

5.2.5 Directional overcurrent

5.3 Fuses

5.3.1 General

5.3.2 Standards for fuses

5.3.3 Current-limiting fuses, HRC fuses and cartridge fuses

5.3.4 Minimum breaking current

5.3.5 Expulsion fuses — High voltage

5.3.6 Re-wireable fuses — Low voltage

5.4 Earth fault protection

5.4.1 Timed earth fault using inverse type time-current characteristics

5.4.2 Directional earth fault

5.4.3 Sensitive earth fault (SEF)

5.4.4 Restricted earth fault (REF)

5.4.5 Earth fault protection for mines conforming with AS/NZS 2081

5.5 Distance protection

5.6 Differential protection

5.7 Back-up protection

5.8 Frame leakage protection

5.9 Intertrip and protection communication schemes

5.10 Earth fault indicators (EFIs) and fault indicators

5.11 Buchholz

5.12 Gas pressure and rate of change of pressure

5.13 Optical arc flash detection

6 Protection devices

6.1 General

6.2 Overcurrent operated protective devices

6.2.1 General

6.2.2 Accuracy and tolerance of time-current characteristics

6.2.2.1 General

6.2.2.2 Induction disc type relay

6.2.2.3 Digital/numeric type relay

6.2.2.4 MCBs

6.2.2.5 Fuses

6.2.3 Overcurrent relay and separate circuit-breaker systems

6.2.3.1 Relaying principle

6.2.3.2 Relay characteristics and ratings

6.2.3.3 Time-current characteristics

6.2.3.4 Overcurrent relays usage

6.2.3.5 Overcurrent relay application principles

6.2.4 Instantaneous overcurrent

6.2.5 Definite time overcurrent

6.2.6 Directional overcurrent scheme

6.2.7 MCBs for low voltage systems

6.2.7.1 General

6.2.7.2 Application

6.2.8 Selection of low voltage circuit breakers

6.2.9 Thermal-magnetic circuit breakers

6.2.10 Magnetic only circuit breakers

6.3 Fuses

6.3.1 High voltage (HV) fuses

6.3.1.1 General

6.3.1.2 Expulsion fuses

6.3.1.3 Expulsion fuses “boric acid” type

6.3.1.4 Current-limiting fuses (cartridge fuses)

6.3.1.4.1 General

6.3.1.4.2 Minimum breaking current

6.3.1.4.3 De-rating of current-limiting fuses

6.3.1.4.4 Loading of HV current-limiting fuses

6.3.1.5 Application of HV fuses to distribution transformer protection

6.3.2 Low voltage fuses

6.3.2.1 General

6.3.2.2 Low voltage fuse time current characteristics

6.4 Earth fault protection

6.4.1 Timed earth fault using inverse type relays

6.4.2 Directional earth fault

6.4.3 Sensitive earth fault (SEF) protection

6.4.4 Restricted earth fault (REF) protection

6.4.5 “Ground fault” protection

6.4.6 Earth fault protection conforming with AS/NZS 2081

6.4.7 Frame leakage protection

6.4.8 Neutral point displacement

6.4.9 Residual current devices (RCDs)

6.4.10 Residual current circuit breakers (RCCBs)

6.4.11 Voltage operated earth leakage circuit breaker

6.5 Distance protection

6.5.1 General

6.5.2 Operating characteristics

6.5.3 Distance with permissive and blocking schemes

6.6 Differential protection

6.6.1 General

6.6.2 Line differential or feeder differential

6.6.3 Transformer differential

6.6.4 Busbar differential

6.6.4.1 General

6.6.4.2 High impedance differential

6.6.4.3 Low impedance differential

7 Back-up protection

7.1 General

7.2 Key message

7.3 Legislative documents

7.4 Components

7.5 Fault types

7.6 System levels

7.7 Methods of achieving back-up protection

7.8 Remote back-up (RBU)

7.8.1 Concept

7.8.2 Advantages of RBU

7.8.3 Disadvantages of RBU

7.8.4 Rules of application/pick-up factor

7.8.5 Examples of RBU application

7.9 Local back-up (LBU)

7.9.1 Concept

7.9.2 Transfer trip circuit

7.9.3 Feeder intertrip

7.9.4 Independence of No. 1 and No. 2 protection schemes

7.9.5 Advantages of LBU

7.9.6 Disadvantages of LBU

7.10 Fuses and back-up

8 Application of protection schemes

8.1 General

8.2 Feeder protection

8.2.1 General

8.2.2 HV overhead lines — Radial (11 kV and 22 kV)

8.2.3 HV overhead lines in rings or closed networks (33 kV, 66 kV and 132 kV)

8.2.4 HV underground cables — Radial (11 kV and 22 kV)

8.2.5 HV underground cables in rings or closed networks (33 kV and 66 kV)

8.2.5.1 General

8.2.5.2 Translay protection

8.2.5.3 Solkor protection

8.2.6 LV overhead lines

8.3 Capacitor protection

8.3.1 General

8.3.2 Typical protection

8.4 Motor protection

8.4.1 General

8.4.2 Levels of protection schemes

8.4.3 Motor protection functions

8.4.4 Thermal overload

8.4.4.1 Purpose and application

8.4.4.2 Coordination

8.4.4.3 Coordination types

8.4.5 Start-up protection

8.4.5.1 Purpose and application

8.4.5.2 Features and limitations

8.4.6 Running stall protection

8.4.6.1 Purpose and application

8.4.6.2 Features and limitations

8.4.7 Asymmetry — Purpose and application

8.4.8 Unbalance protection — Purpose and application

8.4.9 Undercurrent protection — Purpose and application

8.4.10 Undervoltage

8.4.10.1 Purpose and application

8.4.10.2 Features and limitations

8.4.11 Overvoltage (over fluxing)

8.4.11.1 Purpose and application

8.4.11.2 Features and limitations

8.4.12 Self-excitation protection

8.4.12.1 Purpose and application

8.4.12.2 Features and limitations

8.4.13 Loss of phase protection — Purpose and application

8.4.14 Special protection for synchronous motors

8.4.14.1 Advantages

8.4.14.2 Protection

8.4.14.3 Motor protection discrete components

8.4.15 Pole slipping protection

8.4.16 Diode failure supervision

8.4.17 Rotor earth fault protection [64F]

8.4.18 Overload (motor protection) devices

8.4.18.1 General

8.4.18.2 Eutectic alloy overload relays

8.4.18.3 Bimetal overload relays

8.4.18.4 Solid state overload relays

8.4.19 Advanced motor protection

8.4.20 Motor trip class

8.5 Variable speed drive (VSD) protection

8.5.1 General

8.5.2 Principle of VSDs and mining electrical systems

8.5.3 Extension of electrical protection principles to systems with VSDs

8.5.4 Basic operating principles

8.5.5 Improving protection

8.5.6 The effects of frequency on touch potential and duration

8.5.7 Common misnomers and misconceptions

8.5.8 Wideband earth leakage protection

8.5.9 Guidance for identification of potential risks

8.5.10 Summary

8.6 Transformer protection

8.6.1 General

8.6.2 Transformer protection component schemes

8.6.2.1 General

8.6.2.2 Differential protection

8.6.2.3 Buchholz protection

8.6.2.4 High side overcurrent

8.6.2.5 Low side overcurrent

8.6.2.6 High side instantaneous overcurrent (high set)

8.6.2.7 High side earth fault

8.6.2.8 High side restricted earth fault

8.6.2.9 Low side earth fault

8.6.2.10 Low side restricted earth fault

8.6.2.11 Tapchanger protection

8.6.2.12 High temperature trip

8.6.2.13 Tank earth fault protection (frame leakage)

8.6.2.14 Rate of pressure rise

8.6.2.15 Loss of cooling flow

8.6.2.16 Pressure relief device

8.6.3 Typical examples of combinations of component schemes

8.6.3.1 Distribution transformer

8.6.3.2 Zone transformer

8.6.3.3 Subtransmission transformer

8.7 Generator protection

8.7.1 General

8.7.2 Protection against external faults

8.7.3 Protection against overloads

8.7.4 Protection against reverse power conditions

8.7.5 Protection against frequency variations

8.7.6 Protection against internal phase faults

8.7.7 Protection against undervoltages and overvoltages

8.7.8 Stator earth fault protection

8.7.9 Protection against loss of field

8.7.10 Check synchronizing

8.7.11 Multi-function generator protection relays

8.8 Busbar protection (BBP)

8.8.1 General

8.8.2 Busbar categories

8.8.3 Protection schemes for BBP

8.8.3.1 General

8.8.3.2 Remote overcurrent and earth fault only

8.8.3.3 Differential

8.8.3.4 Frame leakage protection

8.8.3.5 Optical arc flash

8.8.3.6 Blocking schemes

8.8.4 HV fuses

8.8.5 Earth fault restriction by NERs

8.8.6 Low voltage busbar faults

8.8.7 Back-up protection

8.8.8 Remote ends

8.9 Power frequency overvoltage and undervoltage protection

8.9.1 General

8.9.2 Application of voltage transformers (VTs)

8.10 Transient overvoltage protection (lightning and switching surges)

8.10.1 General

8.10.2 Lightning stroke currents

8.10.3 Principles

8.10.3.1 General

8.10.3.2 Shielding

8.10.3.3 Surge arresters

8.10.3.4 Earthing of arresters

8.10.3.5 Insulation coordination

8.10.3.6 Surge impedance and reflections

8.10.3.7 Power frequency voltage rating of the arrester

8.10.4 Surge arrester characteristics

8.10.5 Types of lightning arrestors according to class

8.10.5.1 Station class

8.10.5.2 Intermediate class

8.10.5.3 Distribution class

8.10.5.4 Secondary class

8.10.6 Additional points of application

8.10.7 AC surge arresters for low voltage installations

8.10.7.1 General

8.10.7.2 Application (low voltage installations)

9 Components in the protection system

9.1 General

9.2 Relays

9.3 Current transformers

9.3.1 General

9.3.2 What does a current transformer do?

9.3.3 How does a current transformer work?

9.3.4 Current transformer classifications

9.3.5 CT secondary wiring and connections

9.3.6 Post type current transformers (CTs)

9.3.6.1 General

9.3.6.2 Construction

9.3.6.3 Failures

9.3.6.4 Precautionary testing and monitoring

9.3.6.5 Oil

9.3.6.6 Earthed screen connection

9.3.6.7 Removal of post type CTs

9.3.6.8 Lightning and switching overvoltage protection

9.3.6.9 Temperature

9.4 Voltage transformers

9.5 Circuit breakers

9.6 Tripping energy source

9.6.1 General

9.6.2 Batteries for protection purposes

9.6.3 Capacitor trip units

9.6.3.1 General

9.6.3.2 Line side VT supplied cap trip

9.6.3.3 Short circuit fault current driven (SCFCD) cap trip

9.6.4 No volts coil tripping

9.6.5 Self-powered relays

9.6.5.1 General

9.6.5.2 Start-up

9.6.5.3 Blackouts

9.6.5.4 Internal batteries

9.6.5.5 Threshold current

9.6.5.6 Earth fault relays

9.6.5.7 Self-contained circuit-breakers

9.7 Wiring

9.8 Communications for protection functions

10 Lifecycle management

10.1 General

10.2 Planning

10.3 Design through to commissioning

10.3.1 Type testing

10.3.2 Purchaser testing

10.3.3 Testing after installation

10.3.3.1 General

10.3.3.2 Differential protection

10.3.3.3 Directional protection

10.3.4 Application of relay settings

10.3.5 Final pre-energization testing of protection

10.4 Routine items

10.4.1 Routine testing

10.4.1.1 General

10.4.1.2 Electromechanical relays

10.4.1.3 Digital and numerical relays

10.4.1.4 Earth leakage testing

10.5 Responses to non-routine events

10.5.1 Incident investigation

10.5.2 Fault finding of protection scheme

10.6 Ongoing management

10.6.1 General

10.6.2 Maintenance testing

10.6.3 Audits of settings

11 Worked calculations

11.1 General

11.2 Calculation of prospective busbar fault levels

11.3 CT secondary reference voltage

11.4 Core balance CT selection

11.5 Reactances expressed as a percentage

11.6 Reactances expressed an Ohmic value

11.7 X/R and power factor

12 Protection study

12.1 General

12.2 Purpose

12.3 Content and sequence of a protection study

12.3.1 General

12.3.2 Network or installation

12.3.3 Selection of the protection schemes

12.3.4 Scheme functions and circuitry

12.3.5 Selection of relays and devices

12.3.6 Relay settings

12.3.7 Overall considerations

12.4 Examples of data to be supplied for protection study

13 Industry learnings

13.1 General

13.2 Failure of tripping battery supplies

13.3 Arcing faults

13.4 Bolted cable couplers

13.5 Programmable output tripping relays

13.6 Minimum breaking current failure of HV fuses

13.7 Walking dragline on extended cables

13.8 CT secondary wiring and polarity issues

13.9 kV vacuum contactors fault interruption

Appendix A

A.1 General

A.2 Scenario

A.2.1 General

A.2.2 Single line diagram

A.2.3 Maximum and minimum fault levels

A.2.4 High voltage protection coordination

A.2.5 Low voltage protection coordination

A.2.6 High and low voltage protection coordination observation

Bibliography

Cited references in this standard

IEEE 399

Recommended Practice for Industrial and Commercial Power Systems Analysis (Brown Book)

ENA EG025

Power system earthing guide, Part 1: Management principles, Version 1

AS/NZS 4871.3:2010

[Superseded]

Electrical equipment for mines and quarries, Part 3: Substations

AS 60204

Safety of machinery — Electrical equipment of machines (series)

AS/NZS 4871.2:2010

[Superseded]

Electrical equipment for mines and quarries, Part 2: Distribution, control and auxiliary equipment

Content history

DR SA/SNZ HB 119:2019