ESKOM HOLDINGS SOC LIMITED CONTRACT NUMBER: __________________

PART 3B: TUTUKA PS MV SWITCHGEAR REPLACEMENT PROJECT

PART 3B: PROTECTION SCHEMES

Document Title No of
reference pages
This cover page 1
C3.1 Employers Works Information 31

C3.2 Contractors Works Information

Total number of pages 32

PART C3: SCOPE OF WORK 1 C3 ECC3 COVER PAGE

ESKOM HOLDINGS SOC LIMITED CONTRACT NUMBER: __________________
PART 3B: TUTUKA PS MV SWITCHGEAR REPLACEMENT PROJECT

C3.1: EMPLOYERS WORKS INFORMATION

TABLE OF CONTENTS

Part 3B: PROTECTION SCHEMES ................................................................................................................. 1

C3.1: Employers works Information ............................................................................................................. 2
LIST OF DEFINITIONS ..................................................................................................................................... 4
LIST OF ABBREVIATIONS .............................................................................................................................. 4
1 Reference Documents ............................................................................................................................ 5
2 Drawing Convention ............................................................................................................................... 5
3 General Requirements ............................................................................................................................ 5
4 Power Supplies ....................................................................................................................................... 7
5 Protection Devices .................................................................................................................................. 8
5.1 Intelligent Electronic Devices ............................................................................................................. 8
5.1.1 Design and Construction.............................................................................................................. 8
5.1.2 Functions...................................................................................................................................... 9
5.1.3 Software ..................................................................................................................................... 10
5.1.4 Analogue Voltage and Current Inputs ........................................................................................ 11
5.1.5 Output Contacts ......................................................................................................................... 11
5.1.6 Testing of Devices ..................................................................................................................... 11
5.2 Buszone Protection Relay ............................................................................................................... 12
5.3 Arc Detection System ...................................................................................................................... 13
5.3.1 Protection Relays ....................................................................................................................... 13
5.3.2 Light Sensors ............................................................................................................................. 13
5.3.3 Monitoring .................................................................................................................................. 14
5.3.4 Auxiliary Relays ......................................................................................................................... 14
6 Protection Schemes ............................................................................................................................. 15
6.1 Numbering System .......................................................................................................................... 15
6.2 Motor Protection Scheme 4PA0100 (Motors 1 MW) ................................................................. 15
6.3 Motor Protection Scheme - 4PA0400 (Motors < 1 MW) .................................................................. 16
6.4 Transformer Feeder Protection Scheme - 4PA0700 (Transformer > 10 MVA) ............................... 18
6.5 MV Interconnector Protection Scheme - 4PA0800 .......................................................................... 19
6.6 Transformer Feeder Protection Scheme 4PA1000 (Transformer < 10 MVA) .............................. 20
6.7 MV Incomer Protection - 4PA1200 .................................................................................................. 20
6.8 Bus Section (4PA1400) and Maintenance Isolator (4PA1400A) Control Schemes ........................ 21
6.9 Diesel Generator Protection Scheme 4PA1500 ........................................................................... 22
6.10 Arc Protection Scheme .................................................................................................................... 23
6.10.1 General ...................................................................................................................................... 23

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PART 3B: TUTUKA PS MV SWITCHGEAR REPLACEMENT PROJECT

6.10.2 Current Detection Methods ........................................................................................................ 23

6.10.3 Circuit Breaker Failure Protection .............................................................................................. 23
6.10.4 Busbar Chamber Protection....................................................................................................... 24
6.10.5 Protection of Circuit Breaker Compartment ............................................................................... 24
6.10.6 Protection of Cable Termination Compartments........................................................................ 24
6.11 Buszone Protection Scheme ........................................................................................................... 25
6.12 DC Fail Function .............................................................................................................................. 25
7 IEDs Provided Free Issue by the Contractor .................................................................................. 26
8 Control Circuit Design Philosophy ..................................................................................................... 27
9 Protection Algorithms and Settings ................................................................................................... 29
10 Interface with Control and Communication Systems ....................................................................... 29
11 List of Reference Procedures, Standards and Specifications ......................................................... 31
12 List of Drawings .................................................................................................................................... 32
13 List of Appendices ...................................................................................... Error! Bookmark not defined.

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PART 3B: TUTUKA PS MV SWITCHGEAR REPLACEMENT PROJECT

LIST OF DEFINITIONS

The definitions as per Part 3A Works Information apply.

LIST OF ABBREVIATIONS

Abbreviation Meaning given to the abbreviation

AC Alternating Current

C&I Control and Instrumentation

COMTRADE Common Format for Transient Data Exchange

CT Current Transformer

DC Direct Current

DCS Distributed Control System

HMI Human Machine Interface

HVAC Heating Ventilation and Air-Conditioning

IDMTL Inverse Definite Minimum Time Lag

IED Intelligent Electronic Device

I/O Input / Output

IPC Interposing Close

IPO Interposing Open

ISO International Standards Organisation

LAN Local Area Network

LCD Liquid Crystal Display

LV Low Voltage

MV Medium Voltage

OHS Act Occupational Health and Safety Act

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PART 3B: TUTUKA PS MV SWITCHGEAR REPLACEMENT PROJECT

TCS Trip Circuit Supervision

VT Voltage Transformer

1 Reference Documents

The Contractor Provide the Works in strict accordance with the contract, this Works
Information. In addition to the requirements of this Works Information, the Works conform to the
documents and drawings listed in section 11 and 12 of Part 3B of the Works Information, as
well as other documents forming part of the references.

The applicable revisions and amendments of the reference documents are the latest versions
in force at the time of the contract award.

Unless specifically stated in section 11 of Part 3B of the Works Information (Part 3B), the
Contractor proposes the specifications required for the detail engineering, fabrication,
installation and commissioning. Such specifications are supported by International
specifications, standards; codes, practices and their use are accepted by the Project Manager.

2 Drawing Convention

Where reference is made in this Works Information to the normal position of auxiliary contacts,
the convention is such that the contacts are in the normal condition when:

a) Circuit breaker truck is in the service position

b) Circuit breaker shown in open position
c) Power and control supplies are "off"
d) Spring not charged

Circuit diagrams produced by the Contractor comply with this convention.

3 General Requirements

The Contractor provides all the protection devices and auxiliary equipment required to perform
the functions defined for the different protection schemes. The main protection functions are
implemented by the use of IEDs.

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PART 3B: TUTUKA PS MV SWITCHGEAR REPLACEMENT PROJECT

Other protection functions required, such as internal arc and bus zone protection are performed
by separate IEDs. The Contractor designs a comprehensive protection scheme that defines the
interfaces between all relays as well as the other related systems.

The Contractor makes provision for the supervision and indication of the status of wiring and
signals from all the tripping relays to the external trip coils.

The design of the protection schemes are presented in the form of Protection & Control
Functional & Interface Diagrams and detailed design drawings together with the related
documentation describing the functions of the different devices used.

Protection & Control Functional & Interface Block Diagrams for typical circuits defined in
section 12 of Part 3B are submitted with the tender documentation for evaluation. All indicated
optional functionalities are catered for and tendered for separately on an individual basis.
Preliminary designs for the 4PA0100, 4PA0700, 4PA0800 and Buszone protection schemes
are required.

Although the Contractor is permitted to alter the designs of the circuits to suit their products, no
functionality may be omitted after Design Freeze without the written consent of the Project
Manager.

All IEDs are pre-programmed with the respective logics that enable the protection scheme to
comply with the specification as provided during the engineering phase. The programmable
logics are also aligned with the relevant design drawings that define the functionality of the
scheme. No logic programming is required after delivery of the equipment, but the application
of conventional functional settings is necessary.

The Contractor also supplies all IEDs for LV switchgear reticulation in accordance with
Appendix 3 of part 3B of the Works Information as highlighted in Part 3A, and section 7 of Part
3B of the Works Information. The supplied LV IEDs are free-issued to Others, for installation
on the LV switchgear panels. Engineering, in the form of logic development and the
programing of the IEDs in accordance to the LV switchgear philosophies is the responsibility of
the Contractor. The Contractor is also responsible for testing and commissioning of the IEDs
after installation by Others.

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PART 3B: TUTUKA PS MV SWITCHGEAR REPLACEMENT PROJECT

The Contractor supplies at least two licences for the software as a minimum for application of
settings and for IED logics.

All IEDs and auxiliary relays provided by the Contractor are type tested by an independent
laboratory and these results are made available to the Project Manager for evaluation and
acceptance. In addition to independent laboratory tests, the protection and associated
equipment offered are evaluated, tested and approved by the Project Manager as per 240-
56227589 and 32-333 prior to offer.

All IEDs, auxiliary relays and their modules have a proven service record of at least five years
and a combined effective service life of one hundred years. An international and national relay
reference sales list is provided by the Contractor with tender submission.

Tendered equipment is designed for a working life-span of at least 15 years in a controlled

environment which is in accordance with 240-56355731 whereby temperature is controlled at
22 oC 2 oC. All common and outside plant substations are pressurised and their ambient
temperature can be taken to range between 5 oC to 40oC. Written guarantees to this effect are
provided. The Contractor also states the maximum allowable operating temperature to achieve
a 15 year life span of the devices.

The Contractor provides the information regarding re-calibration of the electronic devices
necessary to keep them in perfect working order or any other required intervention by the
OEM, subsequent to the sale of equipment that has a financial impact on the Employer.

All future upgrades and modifications of the electronic devices are communicated timeously to
the Employer. Any malfunction of the same device experienced by other users or known to the
Contractor is communicated to the Employer.

4 Power Supplies

Auxiliary power for the protection systems will be provided from an external DC power supply
system provided by the Contractor in accordance with part 3D of the Works Information, except
for the unitised (i.e. Unit 1 to 6) switchgear which will be provided by the Employer. The
nominal rating of the voltage supply will be 220V DC.

IEDs, auxiliary relays and other DC equipment are capable of operating continuously at
extreme tolerances of the DC supply voltage, which is 220V DC 20%. The equipment is

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PART 3B: TUTUKA PS MV SWITCHGEAR REPLACEMENT PROJECT

therefore capable of operating at either 176V or 264V continuously without detriment to the
protection system.

All indications are non-volatile i.e. if the DC supply fails, then on restoration of the DC supply
the indication resumes the status that it had before the supply failed.

5 Protection Devices
The Contractor supplies protection devises that conforms to the requirement stated below in
the following subsections.

5.1 Intelligent Electronic Devices

5.1.1 Design and Construction

The Contractor designs and provide Protection schemes for all the power circuits (i.e.
incomers, feeders and others) consisting of IEDs constructed as a 19 inch rack mountable
unit or according to Contractor's standard arrangement. No terminals are provided on the
19 inch rack. Where required, the tails are suitably ferruled with a minimum length of two
meters.

All IEDs are equipped with screen or display facility to allow for human interface. The
contents are clearly visible from a distance of 2 m and at an angle of 30 from either side.
This display is of the Liquid Crystal Display (LCD) with anti-glare and non-blinking
properties. The IEDs display makes it possible for the mimic of the circuit protected by the
device to be illustrated on the display. The mimic shows as a minimum the status of circuit
breakers (ON or OFF), status of earth switches, position of circuit breaker (connected or
disconnected) and electrical parameters (voltage, current, power, etc.) for a particular
circuit. The mimic should also display an interlock on a device if present.

Provision is made for the local control of the breakers to be performed from the associated
IED using an integrated control pad for local test purposes during maintenance only.

LEDs are required for indication of the operation of the alarm and protection functions
within the IED and are an integral part of the device. The allocation of the LEDs to the
different functionality is configurable to allow for flexibility during the engineering phase.

Split face IEDs, whereby the digital display is mounted on the door of the LV compartment
and connected to the main processing unit by means of fibre optic cable, are preferred.

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PART 3B: TUTUKA PS MV SWITCHGEAR REPLACEMENT PROJECT

The devices are equipped with ports to allow for access to information via a communication
link. These ports have the capacity that matches the data transfer requirements for the
associated communication bus.

A label stating the firmware version is fixed to all IEDs. Information regarding the estimated
data retention time of the storage medium used in the IEDs is provided to the Employer.

5.1.2 Functions

The protection, control, indication and data capturing functionalities are provided by the
IEDs. All functions, settings and internal logic are programmable through the IED software
and a personal computer (PC), except where otherwise stated.

The Contractor specifies and gives written details of protection functionalities that are
inherently part of their IEDs but are not required by the performance specification.

A single IED is able to provide all the required main and back-up protection functions for the
scheme in question as a minimum. The control and indication functions are also
incorporated in the IEDs.

IEDs have measurement functions with analogue outputs as described under section 6 of
Part 3B for each protection scheme. These analogue outputs are configurable by the user
for ranges between 4 and 20mA. Response time for signals is 500msec for a step input of
80%.

The integration of the auxiliary functions such as the DC Fail and Trip Circuit Supervision
(TCS) functions within the device is preferred. The IEDs have a self-monitoring function of
both integral hardware and software that is done on a continuous basis. Any fault or
irregularity is immediately alarmed to an output contact.

The random switching of the DC auxiliary supplies at high rate does not affect the
functionality of the IED. Where required, the internal battery requirements for numerical
IEDs (i.e. battery lifetime, type of battery etc.) is stated on a label attached to the front of the
numerical device.

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PART 3B: TUTUKA PS MV SWITCHGEAR REPLACEMENT PROJECT

Unless otherwise specified, all IED are provided with manual-reset operation indicators for
each function of the IED. These do not operate until the IEDs have operated. Resetting is
accomplished without opening the case.

The IEDs have disturbance or event recording and data logging capability with the integral
storage media. The information stored in the IED is accessible via the communication port.
Information regarding the estimated data retention time of storage medium of the IEDs is
provided to the Employer.

All IEDs have the capability to perform control, indication or monitoring, interlocking and
data transfer functions via a communication bus. The IEDs communication capability
complies with IEC 61850 standard.

5.1.3 Software

Software installed on the IEDs for event or disturbance recordings, data logging, settings
and marshalling or configuration is accessible via a dedicated communication link using
engineering tools. This software allows information to be downloaded in COMTRADE
format in accordance with IEEE C37.111-1991. All software required to perform the
marshalling and settings of the IEDs is contained in one package.

The Contractor supplies evidence, on request, in the form of reports from a mutually
acceptable third party that an adequate formal specification for the software has been
produced at no additional cost. The specification is based on a requirement document and
comprehensive risk analysis. The software is formally verified to ensure that it matches its
specification.

All software purchased on this contract and subsequent software upgrades supports the
latest Microsoft Windows operating system. The Contractor informs the Employer of any
and all new releases. The latest software version is always compatible with the installed
base of IEDs, which originally were compatible with the previous version of software that
was compatible with the previous Microsoft Windows operating system. For example, if the
existing software is only compatible with Windows 95, it is upgraded to Windows 7 (the
latest Microsoft supported operating system).

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PART 3B: TUTUKA PS MV SWITCHGEAR REPLACEMENT PROJECT

All software and firmware are backward and forward compatible (i.e. the software on this
contract is such that all future versions of software will be compatible with the installed base
of IEDs).

5.1.4 Analogue Voltage and Current Inputs

The current inputs of the devices are rated at 1A. Where required, the voltage inputs are
rated at 110V AC, unless otherwise stated.

The IED is also provided with the digital inputs for the control and indication functions as
determined by the schemes described in section 6 of Part 3B.

The configuration of the inputs is programmable. The minimum number of inputs required is
provided in the C&I Interface Signals for MV Switchgear found in Appendix 4A of Part 3B.

5.1.5 Output Contacts

The Contractor designs all protection schemes such that all output contacts of the IEDs
have self-resetting capabilities, except for those linked to master trip and lockout functions,
which have manual-reset capabilities.

Each protection scheme has at least two output contacts for tripping. The IED is also
provided with the digital outputs for the control and indication functions as determined by
the schemes described in section 6 of Part 3B.

The configuration of the devices outputs is programmable. The minimum number of

outputs required is provided in the C&I Interface Signals for MV Switchgear found in
Appendix 4A of Part 3B. Where required, some of the trip, alarm and indication outputs are
channelled via the communication ports.

DC Fail and under voltage protection functions are facilitated by normally closed contacts.
All other relays have normally open contacts.

5.1.6 Testing of Devices

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The Contractor submits certificates and report stating that protection devices offered have
been subjected to routine and type tests which cover at least the tests recommended in
standard 32-333. The program of routine and type tests is submitted to the Project Manager
for acceptance.

Unless otherwise specified, all IEDs are provided with suitable test facilities for VT and CT
circuits to enable tests carried out on the IEDs while in position inside the panel without
disconnecting any wiring or links. Test facilities are provided in accordance with standard
32-333.

Two copies of all test certificates are submitted to the Project Manager for acceptance once
the tests have been completed.

5.2 Buszone Protection Relay

Bus zone protection is implemented by utilising a numerical differential relay. These devices
comply with the requirements of 32-333 standard as a minimum.

Only a low impedance scheme is acceptable. The Contractor provides details of the CT
requirements. CT selection methodology is required to be submitted to the Project Manager
for acceptance.

All devices are fitted with contacts which are self-resetting with exception of the tripping
function.

The devices are provided with hand-reset operation indicators for each of the functions. The
indicators do not operate until the relays have closed their contacts. Re-setting is
accomplished without opening the case.

The protection schemes are provided with suitable test facilities to enable tests to be carried
out on the device while in position on the panel without disconnecting any wiring.

The bus zone protection equipment is housed in separate panels designed to accommodate
482.6 mm (19 inch) type racks or the Contractors standard arrangement. The panels are
constructed in accordance with Eskom Standard number 32-333.

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Auxiliary power for the bus zone protection device will be provided at 220V DC nominal
voltage rating from an external DC power supply system provided by the Contractor in
accordance with part 3D of the Works Information, except for the unitised (Unit 1 to 6)
switchgear which will be provided by the Employer. The AC power supply for the cubicle
lighting will also be provided by the Employer.

DC line filters are installed in the bus zone system such that it protects the electronic
components against voltage spikes.

5.3 Arc Detection System

The Contractor designs and supplies arc protection schemes that are integral part of the
switchgear as described in part 3A of the Works Information.

The arc detection system conforms to the requirement stated below in the following
subsections.

5.3.1 Protection Relays

The arc protection function is provided by a device that accepts both light and current
signals as input. These signals are detected simultaneously to initiate a trip and alarm.

The arc protection relay performs the high speed tripping of the supply circuit breaker in the
event of an arc fault when the current exceeds a pre-set reference value. The device have
a maximum sensor detection function pulse delay time of less than 5 ms and subsequently
issues a breaker trip pulse in a time of less than 10 ms from fault inception. The total
(including breaker and arcing time) fault clearance time required is less than 100 ms from
fault inception.

All devices are fitted with contacts which are self-resetting with exception of the tripping
function.

DC line filters are installed in the arc detection system such that they protect the electronic
components against voltage spikes.

5.3.2 Light Sensors

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PART 3B: TUTUKA PS MV SWITCHGEAR REPLACEMENT PROJECT

Arc detection is performed with light sensitive type elements located in the respective
switchgear chambers (including segregated busbars between panels). The elements are
installed in such a way that they completely cover the space to be protected.

The light sensors are not triggered by external light sources such as camera flashes or
welding arcs.

The sensor has the degree of protection to operate within the boards internal
environmental conditions.

5.3.3 Monitoring

The internal arc protection system has a self-diagnostic (self-monitoring) function that
prevents the relays from operating if a system (i.e. devices and sensors) fault is detected. It
clearly indicates by means of an alarm indicator the fault and the location thereof.

The system gives an indication of the fault location (i.e. which compartment faulted) locally
at the switchgear panel through an IED and remotely on the dedicated engineering station.

The power supply modules are continuously monitored and should provide an alarm in the
event of failure.

5.3.4 Auxiliary Relays

Where required, the auxiliary relays are provided with the desired trip or indication function
with the operation time of less than 50 ms. The auxiliary relays must comply with the
requirements of 32-333.

Unless otherwise specified, all the relays are provided with manual-reset operation
indicator/s for the dedicated function. The indicator/s does not operate until the relay has
operated. Resetting is accomplished without opening the case.

Each relay has at least two output contacts for tripping and two output contacts for external
alarms.

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PART 3B: TUTUKA PS MV SWITCHGEAR REPLACEMENT PROJECT

6 Protection Schemes
Description of circuit protection schemes to be supplied by the Contractor.

6.1 Numbering System

The PA numbering is a numbering system dating back to the 1980's. The first numerical
represents the protection technology, 4 signifying phase 4 (an Eskom description meaning
an IED). PA stands for Protection Auxiliary. The last four numbers signify the type of circuit
being protected.

6.2 Motor Protection Scheme 4PA0100 (Motors 1 MW)

Protection scheme is provided for all feeders to the MV motors with power rating larger or
equal to 1MW. Each scheme includes the following functions:

a) motor differential protection,

b) three-phase thermal overload protection,
c) three-phase definite time overcurrent protection,
d) three-phase IDMTL overcurrent protection,
e) definite time earth fault element,
f) IDMTL earth fault protection.
g) negative phase sequence protection,
h) three phase undervoltage protection,
i) motor stall protection element.

In addition, the schemes have binary Input/output (I/O) facilities as well as analogue outputs.
These input facilities are for external trip and close signals and to enable thermistors to
decrease the tripping time of the overload elements. The trip outputs are latched.

The protection elements have setting ranges as detailed in Schedule A in Appendix 2 of Part
3B. The characteristic curves of IDMTL overcurrent and earth fault protection elements
conform to IEC standards.

Thermal overload protection monitors the current flowing into the motor. Based on these
currents, it models the temperature inside the motor.

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Negative phase sequence protection function is made available in the motor protection
scheme. This function protects the motor against overheating caused by induced double
frequency currents. The negative phase protection has an inverse and a definite time
characteristics.

Motor stall protection function is available in the motor protection scheme. This function is
preferably an overcurrent protection element set below the locked rotor current and a time
delay set to the stall capability time of the motor. The time delay is adjustable over the range
specified in Schedule A in Appendix 2 of Part 3B.

Three-phase definite time undervoltage protection function is made available in the motor
protection scheme. This function does not operate for the loss of a single-phase VT supply
but only operates for the loss of all three phases after a predetermined period. The
undervoltage protection function trips the motors for a sustained under voltage condition. The
protection elements are energized from voltage transformers with secondary of 110 V phase-
to-phase and 63.5 V phase-to-neutral. The elements are adjustable to operate in the voltage
ranges specified in Schedule A and have drop-off/pick-up ratios greater than 95%. Setting
adjustment is preferably continuously variable, but if adjusted in steps, these do not exceed
10%. The time delay is adjustable over the range specified in Schedule A in Appendix 2 of
Part 3B.

Other functions required in the motor protection scheme such as current interlock, long
starting time, etc. are indicated in Schedule A in Appendix 2 of Part 3B.

Provision is made for output analogue signals (i.e. current and power) from the IEDs. The
Contractor provides separate measurement modules (i.e. transducers) for both current and
power. Alternatively, the measurement modules are provided as an integral part of the
protection IED. The Contractor also provides in the Rates Price Schedule both the take out
price for having separate measurement modules, as well as the price for transducers
provided as an integral part of the IED.

6.3 Motor Protection Scheme - 4PA0400 (Motors < 1 MW)

Protection scheme is provided for all feeders to the MV motors with power rating smaller than
1MW. Each scheme includes the following:

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PART 3B: TUTUKA PS MV SWITCHGEAR REPLACEMENT PROJECT

a) three-phase thermal overload protection,

b) three-phase definite time overcurrent protection,
c) three-phase IDMTL overcurrent protection,
d) definite time earth fault element,
e) IDMTL earth fault protection.
f) negative phase sequence protection,
g) three-phase undervoltage protection,
h) motor stall protection element.

In addition, the schemes have binary I/O facilities as well as analogue outputs. These input
facilities are for external trip and close signals and to enable thermistors to decrease the
tripping time of the overload elements. The trip outputs are latched.

The protection elements have setting ranges as detailed in Technical Schedule A in

Appendix 2 of Part 3B. The characteristic curves of IDMTL overcurrent and earth fault
protection elements conform to IEC standards.

Thermal overload protection monitors the current flowing into the motor. Based on these
currents, it models the temperature inside the motor.

Negative phase sequence protection function is made available in the motor protection
scheme. This function protects the motor against overheating caused by induced double
frequency currents. The negative phase protection has an inverse and a definite time
characteristics.

Motor stall protection function is made available in the motor protection scheme. This
function is preferably an overcurrent protection element set below the locked rotor current
and a time delay set to the stall capability time of the motor. The time delay is adjustable over
the range specified in Schedule A in Appendix 2 of Part 3B.

Three-phase definite time under voltage protection function is made available in the motor
protection scheme. This function trips the motors for a sustained under voltage condition and
is provided for protection of MV motors. They are energised from voltage transformers with
secondary of 110 volt phase-to-phase and 63.5 volt phase-to-neutral. The measuring
elements are adjustable to operate in the voltage ranges specified in Schedule A and have
drop-off/pick-up ratios greater than 95%. Setting adjustment are preferably continuously

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PART 3B: TUTUKA PS MV SWITCHGEAR REPLACEMENT PROJECT

variable, but if adjusted in steps, these do not exceed 10%. The time delay is adjustable over
the range specified in Schedule A in Appendix 2 of Part 3B.

Directional earth fault is required if the option of a zero sequence current balancing
transformer is considered across the motor feeder cables since the MV system is resistive
earthed with the MV motor neutral unearthed.

Other functions required in the motor protection scheme such as current interlock, long
starting time, etc. are indicated in Schedule A in Appendix 2 of Part 3B.

Provision is made for output analogue signals (i.e. current and power) from the IEDs. The
Contractor provides separate measurement modules (i.e. transducers) for both current and
power. Alternatively, the measurement modules are provided as an integral part of the
protection. The Contractor also provides in the Rates Price Schedule both the take out price
for having separate measurement modules, as well as the price for transducers provided as
an integral part of the IED.

6.4 Transformer Feeder Protection Scheme - 4PA0700 (Transformer > 10 MVA)

Protection scheme for the feeders of the transformer with the power rating larger or equal to
10MVA includes the following functions:

a) transformer differential protection,

b) three-phase definite time overcurrent protection,
c) three-phase IDMTL overcurrent protection,
d) definite time earth fault protection,
e) IDMTL earth fault protection.

The IDMTL overcurrent and earth fault are set as back-up protection for the transformer
differential protection as well as protection for downstream circuits.

In addition, the IEDs have binary input facilities. These input facilities cater for external alarm
and trip signals such as Buchholz, winding temperature, oil temperature and pressure relief
protection. A minimum of eight binary inputs are required.

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The protection elements have setting ranges as detailed in Technical Schedule A found in
Appendix 2. The characteristic curves of IDMTL overcurrent and earth fault protection
elements conform to IEC standards.

6.5 MV Interconnector Protection Scheme - 4PA0800

Interconnector protection schemes include the following functions:

a) line differential protection,

b) three-phase definite time overcurrent protection,
c) three-phase IDMTL overcurrent protection,
d) definite time earth fault protection, and
e) IDMTL earth fault protection.

The overcurrent and earth fault elements (i.e. IDMTL or definite time) are set as main
protection for the interconnector and back-up protection for downstream circuits.

The Contractor specifies and supplies the fibre optic or pilot wire cables, which are suitable
for the cable differential protection, to be installed by Others. Fibre optic links are preferred
for differential protection application.

A synchronism check facility is provided for the changing of power supplies on a MV board,
which is feeding from different sources. The synchronism check facility measures the three
phase voltage quantities from the cable and busbar VTs. Once the three voltages are the
same, in phase, magnitude, phase rotation and frequency, a closing signal is issued to the
breaker of the normal supply and an open to the alternative supply after a period not
exceeding 100 ms. This is done to ensure the make-before-break operation. Different set
parameters are required.

A typical switching or operating procedure for the power transfer is as follows: Close the unit
supply breaker (with unit supply cable VT alive) to energize the busbar (busbar VT dead and
station supply breaker opened with station supply breaker cable VT dead). Vice versa is also
applicable. This is a Live line, dead bus charge.

The protection elements have setting ranges as detailed in Technical Schedule A found in
Appendix 2 of Part 3B. The characteristic curves of IDMTL overcurrent and earth fault
protection elements conform to IEC standards.

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The Contractor provides output analogue signals (i.e. current and voltage) from the IEDs.
These measurement modules are an integral part of the protection IED. The Contractor also
provides a take out price for having separate measurement modules (i.e. transducers) in the
Rates Price Schedule.

6.6 Transformer Feeder Protection Scheme 4PA1000 (Transformer < 10 MVA)

Protection scheme for the feeders of the transformer with the power rating smaller than
10MVA includes the following functions:

a) three-phase definite time overcurrent protection,

b) three-phase IDMTL overcurrent protection,
c) definite time earth fault protection, and
d) IDMTL earth fault protection.

The IDMTL overcurrent and earth fault are set as main protection for the transformer / feeder
and back-up protection for downstream circuits.

In addition, the IEDs have binary input facilities. These input facilities cater for external alarm
and trip signals such as Buchholz, winding temperature, oil temperature and pressure relief
protection. A minimum of eight binary inputs are required.

The protection elements have setting ranges as detailed in Technical Schedule A found in
Appendix 2 of Part 3B. The characteristic curves of IDMTL overcurrent and earth fault
protection elements conform to IEC standards.
The Contractor provides output analogue signals (i.e. current) from the IEDs. These
measurement modules are an integral part of the protection IED. The Contractor also
provides a take out price for having separate measurement modules (i.e. transducers) in the
Rates Price Schedule.

6.7 MV Incomer Protection - 4PA1200

Incomer protection scheme have the following functions:

a) three-phase definite time undervoltage protection,

b) three-phase definite time overcurrent protection,

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c) three-phase IDMTL overcurrent protection,

d) definite time earth fault protection,
e) IDMTL earth fault protection.

The overcurrent and earth fault protection is utilised to provide the required current input for
the arc detection interlock and also act as back-up protection for downstream circuits.

A synchronism check facility is provided for the changing of power supplies on a MV board,
which is feeding from different sources. The synchronism check facility measures the three
phase voltage quantities from the cable and busbar VTs. Once the three voltages are the
same in phase, magnitude, phase rotation and frequency, a closing signal is issued to the
breaker of the normal supply and an open to the alternative supply after a period not
exceeding 100 ms. This is done to ensure the make-before-break operation. Different set
parameters are required.

A typical switching or operating procedure for the power transfer is as follows: Close the unit
supply breaker (with unit supply cable VT alive) to energize the busbar (busbar VT dead and
station supply breaker opened with station supply breaker cable VT dead). Vice versa is also
applicable. This is a Live line, dead bus charge.

In addition, the IEDs have binary input and output facilities in accordance with the scheme
requirements for external trip signals.

The protection elements have setting ranges as detailed in Technical Schedule A found in
Appendix 2 of Part 3B. The characteristic curves of IDMTL overcurrent and earth fault
protection elements conform to IEC standards.

The Contractor provides output analogue signals (i.e. current and voltage) from the IEDs.
These measurement modules are an integral part of the protection IED. The Contractor also
provides a take out price for having separate measurement modules (i.e. transducers) in the
Rates Price Schedule.

6.8 Bus Section (4PA1400) and Maintenance Isolator (4PA1400A) Control Schemes

The bus section and maintenance isolator schemes are used as control and indication
device only without protection functions.

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The details on the requirements of the scheme are given in Technical Schedule A in
Appendix 2 of Part 3B.

6.9 Diesel Generator Protection Scheme 4PA1500

Protection scheme provided for an incomer from a 3.3 kV diesel generator includes the
following functions:

a) generator differential protection,

a) three-phase definite time overcurrent protection,
b) three-phase IDMTL overcurrent protection,
c) definite time earth fault element,
d) three-phase IDMTL earth fault protection,
e) negative phase sequence protection,
f) three-phase undervoltage protection,
g) three-phase overvoltage protection,
h) three-phase under-frequency protection,
i) three-phase reverse power protection.

In addition, the scheme has binary I/O facilities as well as analogue outputs. These input
facilities are for external trip and close signals. The trip outputs are latched.

The protection elements have setting ranges as detailed in Technical Schedule A in

Appendix 2 of Part 3B. The characteristic curves of IDMTL overcurrent and earth fault
protection elements conform to IEC standards.

Negative phase sequence protection function is made available in the diesel generator
protection scheme. This function protects the diesel generator against overheating caused
by induced double frequency currents. The negative phase protection has an inverse and a
definite time characteristics.

Three-phase definite time undervoltage protection function is made available in the generator
protection scheme. This function does not operate for the loss of a single-phase VT supply
but only operates for the loss of all three phases after a predetermined period. The
undervoltage protection function trips the generator for a sustained under voltage condition.
The protection elements are energized from voltage transformers with secondary of 110 V

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phase-to-phase and 63.5 V phase-to-neutral. The elements are adjustable to operate in the
voltage ranges specified in Schedule A and have drop-off/pick-up ratios greater than 95%.
Setting adjustment is preferably continuously variable, but if adjusted in steps, these do not
exceed 10%. The time delay is adjustable over the range specified in Schedule A in
Appendix 2 of Part 3B.

Other functions required in the diesel generator protection scheme such as current interlock,
long starting time, etc. are indicated in Schedule A in Appendix 2 of Part 3B.

6.10 Arc Protection Scheme

6.10.1 General

The system protects the segregated breaker, busbar and cable chamber respectively in the
case of an internal arc fault for air insulated MV switchgear.

The main protection device is mounted on the board incomer panels with the auxiliary
devices in different panels as required.

6.10.2 Current Detection Methods

A three-phase CT connection from the board incomer or upstream feeder overcurrent

and/or earth fault function is provided together with an arc sensing device (two-out-of-two
measuring criteria). The current rating of the input to the device is 1 A.

An overcurrent or earth fault signal is activated once the current on any one phase exceeds
the reference values. This function has the capability to capture and display the three
phase currents that caused the protection operation. The system is able to provide arc
protection with low fault currents as well (i.e. smaller than 4 kA fault current).

Detection of overcurrent conditions is implemented to increase the stability of the detection

system under normal conditions. This feature ensures that the system does not act on
incidents where light is emitted without the existence of excessive current in the circuit
concerned.

6.10.3 Circuit Breaker Failure Protection

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The circuit breaker failure protection facility is provided by the arc protection system to trip
the upstream feeder circuit breaker in case of an incomer breaker failure. A time delay of
100 ms is allowed for the main circuit breaker to operate before the breaker fail protection
operates the upstream circuit breaker. The total tripping time does not exceed the
switchgear internal arc test time, Tt (as defined in IEC 62271-200).

6.10.4 Busbar Chamber Protection

The function of this application is to detect and clear internal arc faults in the busbar
chamber on a particular board. When any of the light sensors on the board detect an arc
together with an overcurrent or earth fault current on the incomer feeder, it trips the incomer
feeder, bus section breaker and all the feeder circuit breakers of the relevant zone.

The internal arc detection devices are applied to overlap in the bus section chamber, thus
tripping only the faulty zone for an internal arc fault in the bus section chamber.

6.10.5 Protection of Circuit Breaker Compartment

The function of this application is to detect and clear internal arc faults in the circuit breaker
chamber. Where multiple tripping is required the arc sensing devices detect an arc together
with an overcurrent or earth fault current from the incomer feeder, it trips the incomer
feeder, bus section breaker and all the feeder circuit breakers of the relevant zone.

6.10.6 Protection of Cable Termination Compartments

6.10.6.1 Feeders

The function of this application is to detect and clear internal arc faults in the feeder
cable chamber. Where multiple tripping is required the arc sensing devices detect an
arc together with an over current or earth fault current from the incomer feeder it trips
the incomer feeder, bus section breaker and all the feeder circuit breakers of the
relevant zone.

6.10.6.2 Incomers

The function of this application is to detect and clear internal arc faults in the incomer
cable chamber. Where multiple tripping is required the arc sensing devices detect an

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arc together with an over current from the upstream feeder it trips the upstream feeder
circuit breaker.

6.11 Buszone Protection Scheme

The bus zone protection scheme is designed to protect the breaker, busbar and cable
chamber respectively in the case of a three phase bolted fault for air insulated MV
switchgear. The protection scheme is based on basic operation principles of low impedance
differential current measuring system.

The function of the bus zone protection system is to perform fast clearance of phase to
phase and phase to earth faults. The supply breaker and all feeder breakers are tripped in
the event of a fault and current exceeding a pre-set reference value.

A check feature such as integral circuit supervision is included to prevent tripping of bus-
zone protection if any of the current transformer circuits become disconnected during normal
load conditions. Alarm contacts operate under these conditions to initiate a remote alarm.

A testing system, consisting of current isolation and measuring facilities at the input from
each current transformer, and facilities for short-circuiting the current transformer circuits,
when they are isolated from the protection system, is included.

The detailed system description (i.e. specification, layouts and circuit diagrams) and test
procedures for the bus-zone protection system is provided in the tender documents.

The Project Manager may request the Contractor to check whether the bus zone protection
is stable under external fault conditions.

The protection CT core is fed onto standard switchgear terminals and then to the CT test
block and protection device measuring elements with overlapping of the bus section CT
cores.

The boards requiring single or double zone tripping are indicated in the Appendix 3 of Part
3B.

6.12 DC Fail Function

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DC Fail function is provided to monitor the DC supplies of all the protection schemes at the
last supply point. This functionality can either be incorporated in the IED, if a separate power
supply is available, or a dedicated auxiliary relay.

The function allows for operating on loss of DC voltage. Alarm output signal is also
transmitted to the DCS system and indicated on the IED, if separate suppliers are used.

7 IEDs Provided Free Issue by the Contractor

In addition to IEDs provided for MV Switchgear, the Contractor supplies the IEC 61850
compliant IEDs for incomer and bus section circuits of the following LV Switchgear Boards:

400V FFP Cleaning Air Equipment Boards A & B

690V DHP Compressor House Boards A & B
400V DHP Compressor House Boards A & B
400V FFP Boards 1A & 1B
400V FFP Boards 2A & 2B
400V FFP Boards 3A & 3B
400V FFP Boards 4A & 4B
400V FFP Boards 5A & 5B
400V FFP Boards 6A & 6B
400V Ash Bunker Boards 1A, 1B & 1C
400V Ash Bunker Boards 2A, 2B & 2C
400V Ash Bunker Boards 3A, 3B & 3C400V Brine Concentration Plant Boards 1A &
1B

Generic technical requirements of these IEDs are as per section 3 and 5.1 of this Works
Information (Part 3B). However the design functionality, descriptions, schematic drawings and
protection settings for the specific circuits are provided by Others. The Contractor uses the
information provided by Others to design, program and configure IEDs in such a manner that
they function according to the design. The Contractor also configures the IEDs to interface
with SAS network. Physical installation of these IEDs into the LV Switchgear panels is the
responsibility of Others. The configuration of the IED, FAT, SAT, routing and termination of
SAS fibre optic cables are the responsibility of the Contractor.

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8 Control Circuit Design Philosophy

The standard circuit design facilitates the integration of signals from the CTs and VTs and the
interface with circuit breakers to perform various functions such as protection, control, alarm
and monitoring. The IED that can perform at least control, indication and protection
functionalities is used. The IED is also linked to the circuit breakers and earth switches for
inter-tripping and interlocking functions where required.

The control circuit design for the different types of feeders is described by Typical Schematic
Diagrams listed in section 12 of Part 3B. The typical design includes functions for Supply
Point, Control Trip, Control Close and Indication and DCF as shown in Figure 1 below.

Figure 1: Typical Schematic Diagram for Control Circuit

The 220V DC control circuit design has the following functions as a minimum:

a) Control Trip - Trip signal to circuit breaker

b) Control Close - Close signal to circuit breaker
c) Indication and DC Fail - Circuit breaker indication and DC fail alarm.

The control circuit is protected as per proven Eskom practice. The Contractor ensures that
there is adequate co-ordination grading between the mcbs in the control circuit and also the
feeder from the DC supply. Example of the graded system of the mcbs used for the protection
of the control circuit is as follows (as shown in Figure 1):

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a) Supply point = 32A.

b) Control Trip = 16A.
c) Control Close = 6A.
d) Indication, spring charge and DC Fail = 2A.

The designs of the components in the circuit breaker control circuits takes into account the
control philosophies for closing and tripping the individual devices. The circuit is typically
supplied from a 32 A power supply fed from the 220V DC external supply.

The control trip is the most important function of the control circuit and is supplied first,
protected with a 16A protection device. Should a fault downstream in the close or
indication and DC fail function appear, the protection would protect the control trip from
losing power. Typical trip coil inrush current is 2.8A (maximum), which will give a safety factor
of 5 on the 16A circuit protection rating.

The control close is more important than the indication and should a downstream fault in the
indication and DC fail function appear the protection would protect the control close from
losing power. Typical close coil inrush current is 2.8A (maximum), which will give a safety
factor of 2 on the 6A circuit protection rating.

The indication and DC fail have the lowest protection rating. Should any upstream mcb
operate, the DC fail operates and a DC fail alarm is activated but no operation of any
protection function should take place.

The control circuits is designed to make allowance for the alarm signals to be sent to the C&I
system in accordance with the requirements described by the C&I Interface Signals for MV
Switchgear in Appendix 4A of Part 3B.

External 220V DC power supply is provided for the switchgear control circuit. This is used to
provide power to the protection devices as well as the spring re-charge motors.

The design of the switchgear is such that a failure and restoration of the 220V DC control
supply voltage would not cause the complete isolation of the switchgear. It is required that two
trip coils are used on each of the Unit Transformer Incomer Breaker and other panels as
indicated in the Switchgear Schedules in Part 3A Appendix 3 of this Works Information.

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Application of surge suppression units for control circuits, where required, is in accordance
with 240-56227573.

9 Protection Algorithms and Settings

The Contractor provides a detailed description including formulas and diagrams of the
algorithms used to perform the protection functions to the Project Manager. This information is
treated as strictly confidential. This information is provided for all protection scheme
developments.

The Contractor provides a comprehensive set of blank forms and example setting details to
cover all user settable configurations/functions in the module to the Employer.

The IED marshalling is seen as part of the scheme as it is imperative that it is in accordance
with the scheme design in order for the scheme to function correctly. All settings/marshalling
related to the different protection schemes is pre-programmed at the factory and all IEDs are
delivered pre-programmed in accordance with the scheme design.

The final protection settings for the relays will be provided by the Employer for the Contractor
to implement. In case the settings are not available at the time of Factory Acceptance Tests
(FATs), the Contractor develops the preliminary settings for the purpose of testing. These
settings are accepted by the Project Manager.

The settings/marshalling are seen as integral parts of the scheme documentation. They are
provided as part of the documentation as well as in software format in the file type as required
by the associated IED.

10 Interface with Control and Communication Systems

The different operating conditions (i.e. normal and abnormal) that are monitored by the
protection schemes initiate different alarms. These alarms are communicated between IEDs,
SAS and DCS via dedicated hardwired and communication bus links. The description of the
concept proposed for the communication network is described on Part 3C of this Works
Information.

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The interface between the IEDs on the switchgear and the operating and engineering stations
are facilitated by an Ethernet based Local Area Network (LAN) using IEC 61850 protocol as
described in Part 3C of this Works Information.

Data transfer between IEDs and DCS is done using hard wiring method and in accordance
with C&I Interface Signals for MV Switchgear spreadsheet provided in Appendix 4A of Part
3B. The signal descriptions can be found in Appendix 4B of Part 3B.

Safety trip signals (e.g. Boiler trip, conveyor trip, etc.) issued from the DCS are done via
interposing relays with potential free contacts. The operating voltage of the interposing relays
is 24V DC. The interposing relays are designed to withstand the rated current of the closing
coil for two times the longest possible closing time. SIL 3 rating interposing relays in
accordance with the requirements of IEC 61511 are required. The interposing relay is also
designed to withstand the making of the closing coil current at maximum system voltage
rating.

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11 List of Reference Procedures, Standards and Specifications

The Contractor complies with all standards, specifications and regulations as part of 240-
56227573 and the following standards as highlighted within this Works Information:

Table 1: Standards, Specifications and Regulations

32-333 Standard for Electronic Protection and Fault Monitoring
Equipment for Power Systems.

List of Approved Electronic Devices to be used on Eskom

240-56227589 Power Stations.
IEC 61850 Communication networks and systems in substations.
240-56355731 Environmental Conditions for Process Control Electronic
Equipment used at Power Stations.
240-56227573 AC Metal-Enclosed Switchgear and Controlgear for
Voltages above 1kV up to and including 52kV.
IEEE C37.111-1991 Standard Common Format for Transient Data Exchange
(COMTRADE) for Power Systems.
IEC61511 Safety Instrumented Systems For The Process Industry
Sector

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12 List of Drawings

This is the list of drawings issued by the Employer.

Table 2: List of Typical Protection Functional & Interface Block Diagrams

Drawing Number Title

0.52/30478 Motors >1MW Protection Scheme
0.52/30479 Motors < 1MW Protection Scheme
0.52/30482 Transformers > 10MVA Protection Scheme
0.52/30481 Interconnector Protection Scheme
0.52/30483 Transformers < 10MVA Protection Scheme
0.52/30476 Incomer Protection Scheme
0.52/30477 Bus Section Protection Scheme
0.52/30474 Maintenance Isolator Protection Scheme
0.52/30489 Diesel Generator Protection Scheme
0.52/30475 Double Buszone Protection Scheme
0.52/30480 Arc Protection Scheme (selective and multiple tripping)

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13 List of Appendices

Appendix 1: Compliance Schedule for Part 3B

Appendix 2: Technical Schedules A and B for Part 3B

Appendix 3: Quantity of Protection Schemes Required

Appendix 4A: C&I Interface Signals for MV Switchgear

Appendix 4B: C&I Interface Signals for MV Switchgear Description

Appendix 5: Typical Protection Functional & Interface Block Diagrams

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