WG draft 1A -17Feb 2009

ELECTRICITY SUPPLY —

QUALITY OF SUPPLY

Load Shedding Practices, System

Restoration Practices, and Critical &

Essential loads

WG draft 1A

This document is not a South African National Standard

N R S

NRS 048-9:2009

ISBN 978-0-626-21055-7 Edition 1

WG draft 1A -17Feb 2009

This specification is issued by

the Standardization Section, Eskom,

on behalf of the

User Group given in the foreword.

Table of changes

Change No. Date Text affected

Correspondence to be directed to Printed copies obtainable from

The NRS Projects Manager Standards South Africa

Industry Association Resources Centre

Eskom Private Bag X191

Private Bag X 13 Pretoria 0001

Halfway House 1685

Telephone: 012 428 7911

Fax : 011 651 6827 Fax : 012 344 1568

E-mail : nrs@eskom.co.za E-mail : sales@sabs.co.za

Website: http://www.nrs.eskom.co.za Website : http://www.stansa.co.za

COPYRIGHT RESERVED

Printed in the Republic of South Africa

by Standards South Africa

1 Dr Lategan Road, Groenkloof, Pretoria

NRS 048-9:2007

WG draft 1A -17Feb 2009

Foreword

This specification was compiled by representatives of the South African Electricity Supply Industry

(ESI), in a working group appointed by the Electricity Suppliers Liaison Committee (ESLC). The

working group membership included NERSA, Government, and customer representation - inter alia

representation of the Energy Intensive User Group (EIUG).

This specification specifies load shedding practices and associated practices for critical and

essential loads. The working group was guided by the experiences of utilities, customers, and the

public during the load shedding events of 2008, as well as subsequent measures taken to improve

load shedding practices.

This specification was prepared by a working group which, at the time of publication, comprised the

following members:

AJ Dold (Chairman) eThekwini Electricity

SA Adams Nelson Mandela Metropolitan Municipality

DK Bhana Eskom Holdings Limited (KSACS Division)

BG Chatterton Eskom Holdings Limited (Distribution Division)

G de Beer Sasol

M Dekenah Marcus Dekenah Consulting cc

S Delport Ekurhuleni Metropolitan Municipality

GM Dindi City of Cape Town

HJ Geldenhuys (Dr) Eskom Holdings Limited (IARC, Corporate Services Division)

A Hepburn Energy Intensive User Group (EIUG)

AC Kachelhoffer Tshwane Electricity

I Kekana Tshwane Electricity

M Kneen Glass Manufacturing Industry

RG Koch Eskom Holdings Limited (Corporate Services Division)

DA Kruger Chamber of Mines

J Maree Mondi Paper

RR McCurrach Eskom Holdings Limited (Transmission Division)

S Mda Department of Public Enterprises

M Mncube National Energy Regulator of South Africa (NERSA)

M Ngcamu Department of Public Enterprises

T Nortje Exxaro Resources

H Mostert Eskom Holding Limited (Distribution Division)

A Sayed City Power Johannesburg (Pty) Ltd

V Shikoana Eskom (Distribution Division)

M Shozi National Energy Regulator of South Africa (NERSA)

I Sigwebela Eskom Holdings Limited (Transmission Division)

T Thenga National Energy Regulator of South Africa (NERSA)

S Zimu Eskom (Technical Audit, Corporate Services Division)

Annexes A, B, and C are for information only.

Introduction

The country’s infrastructure, of which the power system forms an essential part, is exposed to a

wide variety of threats (for example: storms and the impacts of climate change, wilful damage to

infrastructure, key network/plant failures, load shedding required in the event of capacity shortage).

Unlike countries that are more regularly exposed to the impact of such threats, South African

society has been relative unprepared for the associated disruptions – and therefore when these

occur the impacts on society and the local/national economy can be significant. The increasing

dependency of society on the power system, and the potential for an increase in the frequency of

such threats materialising, implies the need for a country approach to enhancing societal resilience.

From a power system perspective, a comprehensive approach to addressing the requirements of

identified critical and essential loads needs to be developed so as to contain the impact from the

perspectives of safety, environmental impact, society impact, economic impact etc.

NOTE: The load shedding undertaken in South Africa in January 2008 highlighted significant shortcomings in the preparedness of the country for load shedding, and in associated load shedding practices. Key concerns were: (i) safety - people, impact on the environment, and plant; (ii) the predictability of load shedding; (iii) the level of equitable participation of different customers in load reduction - i.e. when and how often customers were shed; (iv) social impact (e.g. traffic during peak hours) and; (v) economic impact on the country.

This code of practice is aimed at preparing the country for greater resilience in the event of threats

to the power system materialising (including national load shedding due to an imbalance in supply

and demand, blackouts extending of over a significant area of the country, and local supply

interruptions).

Although a low system reserve margin implies an increased likelihood that load reduction may be

required to balance supply and demand, the need for a robust set of emergency load shedding

protocols exists even under healthy reserve margin conditions. Load shedding is also not limited to

generation capacity shortages, but could arise due to regional or local network constraints. The aim

of load shedding is to protect the network so as to ensure that the safety of the country as a whole

is addressed. The development of a robust set of emergency load shedding practices and

associated level of preparedness by stakeholders and the public, should be seen in the context of

overall measures undertaken to manage an imbalance in supply and demand (i.e. supply-side

interventions such as increased generating capacity and plant availability, as well as demand-side

interventions such as demand side management (DSM) programmes and energy rationing

programmed. Such imbalances are to be prevented as far as possible taking economics and

practicality into account.

An approach to dealing with critical loads that only addresses supply network considerations (e.g.

exclusion of these loads from load shedding schedules) may not be optimal - and in many cases

may be impractical. This brief therefore considers a more comprehensive approach to addressing

individual loads by addressing a range of interventions to make society in general more resilient to

possible load shedding, i.e.:

a) the time of day that loads should or should not be shed;

b) protocols for reacting when specific areas are shed;

c) the exclusion of some loads from load shedding schedules; and

d) load interventions such as backup supplies.

A blanket exception of any customer from load shedding schedules is neither practical nor optimal.

Ideally the approach to addressing critical and essential loads should be largely consistent on a

national level (i.e. the various supply authorities). It is the intention that a minimum set of critical

load sub-categories that should be addressed by the various supply authorities will be. Formalisation of the requirement for customers to provide the necessary essential load information

WG draft 1A NRS 048-2 17 eb 2009

WG draft 1A -17Feb 2009

required to the relevant electricity supply authorities. Ideally this could be legislated in terms of the

Occupational Health and Safety Act or the Factories Act – but may be more pragmatically

implemented in terms of demand management legislation currently being developed

The criteria considered in developing the code of practice are:

a) safety of people, the environment, and critical plant;

b) predictability of when and for how long a customer will be interrupted or required to reduce

demand;

c) equitable participation by customers, and how load reduction requirements are allocated

between various Eskom regions, metros, municipalities, key industrial customers, and

international customers (see note);

d) social impact of load shedding and/or curtailment;

e) economic impact on the country.

f) technical constraints on executing load shedding/curtailment or restoration (e.g. concerns about

equipment failure, resources for manual restoration, availability of SCADA/telecontrol)

NOTE Equitable participation refers to striving for general fairness in the manner in which customers are required to participate in load reduction schemes. The nature of load shedding, customer types, and system characteristics, however does not allow for equal participation (complete fairness).

Drafting note – explain that ELS is itself a last resort

Keywords

load reduction, load shedding, load curtailment, critical loads, essential loads, schedules.

1 NRS 048-9:2009

Contents Page

1 Scope .............................................................................................................................. 3

2 Normative references ....................................................................................................... 5

3 Terms and definitions ...................................................................................................... 5

4 Requirements ................................................................................................................. 11

4.1 Application by licensees ........................................................................................... 11

4.2 Application by customers .......................................................................................... 11

4.3 Principles .................................................................................................................. 11

4.4 Development of schedules ......................................................................................... 11

4.5 Communication ......................................................................................................... 11

4.6 Reporting requirements ............................................................................................. 11

5 Requirements – essential loads ....................................................................................... 11

6 Requirements – critical loads ........................................................................................... 11

7 Requirements – specific types of loads ............................................................................ 11

Annex A (informative) Load shedding data for planning curtailment schedules ................. 25

Annex B (informative) Essential load data for system restoration planning and load shedding

.............................................................................................................................................. 26

Annex C (informative) Example of the calculation of schedules taking automatic under-frequency

load shedding into consideration ............................................................................................ 28

Annex D (informative) Example of a time-based load shedding schedule............................. 28

Bibliography ....................................................................................................................... 29

NRS 048-9:2009 2

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3 NRS 048-9:2009

ELECTRICITY SUPPLY — QUALITY OF SUPPLY

Load Reduction Practices and Critical and Essential Loads

1 Scope

This code of practice:

a) Provides electricity suppliers (licensees) with best practice for developing load shedding

practices; [ensure that this includes operational issues, real time info sharing]

b) Provides electricity suppliers (licensees) with best practice for prioritising load restoration after a

major system event;

c) Defines and categorises critical and essential loads;

d) Provides electricity suppliers (licensees), customers, and national and local government with

best practice on how to address these loads in the context of load shedding or system

restoration practices;

e) Identifies the responsibilities that all stakeholders have in relation to information sharing on

critical and essential loads,

f) Identifies the responsibilities that the licensee utility has in terms of information sharing related to

load shedding schedules.

g) Provides standard definitions related to load reduction principles in order to facilitate common

understanding between stakeholders.

h) Defines the roles, responsibilities, and limitations of licensees and customers in addressing

various aspects of load shedding.

Reporting formats are provided as annexes to facilitate the collection of essential load data.

[NOTE where will this doc be referred to in regulations so that all stakeholders can be called to

account/comply??]

2 Normative references

The following documents contain provisions which, through reference in this text, constitute

provisions of this specification. All documents are subject to revision and, since any reference to a

document is deemed to be a reference to the latest edition of that document, parties to agreements

based on this specification are encouraged to take steps to ensure the use of the most recent

editions of the documents listed below. Information on currently valid national and international

standards can be obtained from Standards South Africa.

(DRAFTING NOTE ..to be included).

NRS 048-9:2009 4

3 Terms, definitions and abbreviations

For the purposes of this specification, the following terms, definitions and abbreviations apply.

3.1 Definitions

load curtailment

load reduction obtained from customers who are able to reduce demand on instruction.

NOTE: This load reduction is typically effected within 6 hours of the instruction being issued.

load shedding

load reduction obtained by disconnecting load at selected points on the transmission or distribution

system.

automatic load shedding

load that is shed by automatic defence schemes in response to a sudden threat to the

system (e.g sudden trip of several generation units)

manual load shedding

load that is removed by a human operator

load reduction

the reduction in system load that can be achieved by load curtailment and/or load shedding.

NOTE: This may be required in order to: (i) balance system demand in relation to the available generation capacity at the time; and/or (ii) prevent overloading of transmission or distribution networks in the event of a network emergency.

national load reduction

load reduction interventions required on a national level in response to national generation

capacity shortages

regional/local load reduction

load reduction interventions required to address local power system capacity constraints.

NOTE: Although in some cases national schedules can be applied on a regional basis, the nature of the local event will determine what load should be reduced.

rotational load reduction

regular shedding and/or curtailment required to manage demand over an extended period of

time or for several load reduction events over a period of time, which spreads the requirement

to reduce load over a wider customer base.

emergency load reduction

load reduction in response to an unplanned event or series of unplanned events on the

system.

NOTE: These unplanned events could occur even when a healthy system reserve margin exists, and could be rotational should the event(s) last a few days

planned load reduction

rotational load shedding / curtailment undertaken over an extended period of time to manage

the system

NOTE Planned load reduction is a last resort, after alternative demand reduction or energy

saving measures have been exhausted

essential load requirement

5 NRS 048-9:2009

minimum customer load requirement (e.g. MW, notification time, and duration) to avoid a direct and

significant impact on the safety of people, the environment, and physical plant/equipment, and

which has been specifically notified as such by the customer to the licensee (See essential load

requirements data format in Annex B)

NOTE 1: The load required is generally part of the total load that a customer installation normally requires. A customer will be required to demonstrate the potential impact on safety, the environment, and physical

equipment when notifying the licensee. The essential load requirement may be subject to verification by

the licensee in terms of the criteria in this CoP ].

Drafting note - in requirements - customer to regularly update if any changes to

processes/plan/envirnoment , etc

NOTE 2: The load may be part of a larger installation that will still be required to participate in load shedding or curtailment schemes. NOTE 3: Not contracted (as no guarantee can be given).

NOTE 4: These loads should receive priority during restoration of the system (e.g. in the event of a major local interruption, or of a regional or national blackout) and should as far as possible be excluded from at least the initial stages of load shedding/curtailment.

NOTE 5: These loads that in the past were categorised as SATEPSA loads under the Republic of South Africa Telecommunications and Electrical Power Supply Authority.

critical loads

loads that should as far as possible be protected from the impact of load shedding or loss of supply

in order to either maintain the operational integrity of the power system, or to avoid a cascading

impact on public infrastructure. (e.g. refineries, fuel pipelines)

NOTE: Protection from the impact of load shedding includes measures such as excluding from load shedding schedules, installing back-up facilities, or implementing specific response protocols.

interruptible loads

loads where customers have signed long term contracts with a licensee, whereby the licensee may

interrupt a certain amount of load for a particular time period as a planned load intervention.

NOTE: These loads can specifically be used earlier in the merit order to reduce the possibility of a load reduction event.

customer

person or legal entity that has entered into an electricity supply agreement with a licensee

Demand market participation customers

customers who have signed a contract with their supplier or with Eskom to offer a portion of

their load at a price, for the purposes of load reduction.

NOTE: Depending on their participation parameters, these customers may be categorised as Instantaneous DMP (IDMP), Emergency DMP (EDMP) or Supplemental DMP (SDMP) customers (DRAFTING NOTE: CONSIDER REMOVING)

extra high voltage network

EHV network

set of nominal network voltage levels that are used in power systems for bulk transmission of

electricity in the range 220 kV Un 400 kV

[SANS 1019]

high-voltage network

HV network

NRS 048-9:2009 6

set of nominal network voltage levels that are used in power systems for bulk transmission of

electricity in the range 33 kV Un 220 kV

[SANS 1019, modified]

interruption

phenomenon that occurs when one or more phases of a supply to a customer or group of

customers are disconnected for a period exceeding 3 s

[NRS 047-1]

planned interruption

interruption that occurs when a component is deliberately taken out of service (by the licensee

or its agent) at a selected time, usually for the purposes of construction, preventative

maintenance or repair

[NRS 047-1]

unplanned interruption

interruption that occurs when a component is taken out of service immediately, either

automatically or as soon as switching operations can be performed, as a direct result of

emergency conditions, or an interruption that is caused by improper operation of equipment or

human error

[NRS 047-1]

licensee

body, licensed by the National Electricity Regulator, that generates, transmits or distributes

electricity

NOTE Such a body can be a direct licensee, or an agent (subdistributor) of the licensee.

low-voltage network

LV network

set of nominal network voltage levels that are used for the distribution of electricity, the upper limit of

which is generally accepted to be an a.c. voltage of 1 000 V or a d.c. voltage of 1 500 V

[SANS 1019, modified]

medium-voltage network

MV network

set of nominal network voltage levels that lie above low voltage and below high voltage in the range

1 kV Un 33 kV

[SANS 1019, modified]

major system event

define (needed?) NOT same as for reporting in part6

point of supply

point at which the electrical installation of a customer (on any premises) is connected to the

transmission or distribution system of the licensee (undertaker)

power system frequency

fundamental frequency

7 NRS 048-9:2009

frequency of alternating voltage generated by power system generators

[SANS 61000-4-30]

3.2 Abbreviations

NERSA: National Energy Regulator of South Africa

NRS 048-9:2009 8

4 Requirements – load shedding and curtailment

4.1 Application by licensees

Licensees are required to develop load shedding schedules that take into consideration the

practices in this document (including the manner in which identified categories of critical and

essential loads are addressed).

4.2 Application by customers

Customers should take appropriate precautions or protective measures to prevent, or at least limit,

threat to life, danger to environment, or damage to equipment in the event of load shedding, an

interruption, or load restoration.

4.3 Principles – load shedding

4.3.1 Stages of load shedding

Load shedding shall be undertaken in accordance with published schedules. These schedules

shall be designed to be rotational, should the need for protracted load reduction arise. The

schedules are prepared for the different system requirements (determined by the severity of the

capacity short-fall at the time).

These requirements are defined by the following stages:

Stage 1 (Scheduled): 1000 MW of national (Eskom Distribution and Municipal) load shall

be scheduled for shedding, with customers impacted for predefined intervals. Schedules

shall be prepared from 06:00 – 22:00 daily. Customer loads are assigned to specific time

slots.

Example : Published schedules may indicate that customers are impacted for 2h every 2nd day

(excl. Sunday). In practice, each time slot may overlap its adjacent time slot by an additional 0,5h

to facilitate smooth change over.

Stage 2 (Scheduled): 2000 MW of national (Eskom Distribution and Municipal) load is

scheduled to be shed at 2 hr intervals every day, for example by doubling the frequency of

first 1000MW block.

Stage 3 (Scheduled): Emergency schedules are prepared or an additional 2000 MW, on a

24 hour basis, but might not necessarily be published.

Stage 4 (Unscheduled): The amount of load required to be shed in Manual Load

Shedding Stage 4 is greater than 4000MW. The management of manual load shedding

for Stage 4 is handled in accordance with the situation prevalent at the time.

NOTE: The above includes limited curtailment of Dx customers …. t

Load curtailment in the case of key industrial customers (isolatable loads) – Eskom Key Industrial

Customers …

4.3.1 Principles

A coordinated approach to load reduction shall be developed for the first 3 stages based on the

following principles:

Principle 1: Automatic under-frequency load shedding shall take precedence over manual load-

shedding or curtailment (see note 1).

Principle 2: All customers shall be considered for emergency (manual) load reduction (see note 2).

9 NRS 048-9:2009

Principle 3: Critical and essential load requirements shall be addressed in accordance with this

code of practice.

Principle 4: Time-based manual load shedding shall be applied (see note 3).

Principle 5: Load shedding schedules shall be developed and made available to affected

customers.

Principle 6: Customer reduction due to ECS shall not be considered as emergency load reduction

(see note 4).

NOTE 1: Although both automatic and manual load shedding initiatives respond to supply constraint problems, the conditions that they respond to and the consequences of their failure to respond are very different. Manual load shedding is pro-active, whilst automatic load shedding is an automatic reactive response to an unplanned loss of generation. The consequences of an inadequate automatic response can be catastrophic and widespread, which includes the complete loss of supply to the entire network. For this reason, continuous load shedding beyond 4000MW is not scheduled – as the impact of this on under-frequency schemes places the system at significant risk. NOTE 2: Manual load reduction is an unavoidable event to prevent the power network sliding into an unstable state. The financial implications associated with a national blackout far outweigh the economic cost of manual load shedding. Economic reasons alone are therefore not sufficient to justify exclusion from the emergency load reduction. NOTE 3: Time-based manual load shedding is chosen for the following reasons : (i) Customers generally prefer to know when their supply will be interrupted so that they can better plan their operations / arrangements, (ii) the communication of load shedding schedules is less onerous; (iii) less confusion exists amongst customers about when their supply will be interrupted. NOTE 4: Customers not achieving Energy Conservation Scheme (ECS) targets are penalised in terms of the ECS scheme. Load reduction requirements are demand (MW) driven, whilst ECS targets are energy-based (MWh). Emergency load shedding will require an instantaneous demand reduction.

The management of manual load shedding for Stage 4 of manual load shedding is explicitly

excluded from these principles and will be handled in accordance with the situation prevalent at the

time (see note below)

NOTE 5: For Stage 4 of manual Load shedding to be activated, the implication is that the implementation of all other mitigation actions and initiatives has been exhausted. This means that the supply constraint is extremely serious and bordering on a total collapse of the entire network load. Under these conditions, the focus is entirely on managing the network from a technical point of view ie. to avoid a total loss of load on the entire network. The consequence of a total loss of load is that cold start sequences will have to be initiated which could take many hours before any load is restored. Therefore technical considerations take preference over customer considerations.

4.4 Development of schedules

4.4.1 Calculation of load shedding quotas per region

In determining load shedding quotas for the various licensees, the following methodology shall be

applied:

The total Distribution Load, excluding key industrial customer load under the control of a

specific Eskom Distribution Control Centre is determined.

From this total load, load set aside for national load management by the National System

Operator is subtracted to obtain the base load on which the required reduction for that

Eskom Distribution Control Centre is determined.

The revised load of each Eskom Distribution Control Centre is summed to obtain a revised

load for overall Distribution.

NRS 048-9:2009 10

Each Eskom Distribution Control Centre’s base load is divided by the overall Distribution

base load to calculate it’s required contribution (as a percentage).

Each Eskom Distribution Control Centre’s contribution to the total load shedding

requirement at any point in time is determined by this percentage.

The same method of allocation will be applied to municipal and metro licensees, when

allocating the percentage of the Eskom Distribution Control Centre load.

NOTE: The above is equivalent to the allocation of an individual licensee being determined by the National System Operator, based on the national load reduction requirement.

The above calculation determines the load to be shed continuously over the full period of load

shedding. An individual licensee may choose be completely shed in lieu of implementing its own

rotation. This shall be undertaken in consultation with the upstream licensee supplying this

licensee. The final arrangement shall not negatively impact the integrity of the load shedding

schedule.

4.4.2 Time-based load shedding schedules

A licensee shall develop a time-based load shedding schedule.

Where manual load shedding occurs repeatedly at the same time of the day for successive manual

load shedding events, the manual load shedding schedule that is in force (Schedule A) should be

replaced by another manual load shedding schedule (Schedule B) where the planned customer

loads in any time slot are different.

Both schedules shall comply with the principles laid out in this document. When allocating a

customer to a particular time slot in the schedule, the impact to the customer and / or other affected

parties should be considered. As far as is practical, all possible options should be explored and

taken into account to minimise the impact to those affected by the interruption of the electricity

supply e.g. trying to avoid interruptions to city centres during peak traffic times, etc

NOTE: The purpose of this hybrid approach is to assist with equity in supply interruptions amongst customers.

4.4.3 Addressing under-frequency protection requirements in schedules

The integrity of automatic under-frequency protection schemes shall be maintained during load

shedding/curtailment.

To address the implications of load being shed or curtailed also being required for under-frequency

load shedding during a particular Stage, the following procedure shall be applied:

For the first 10% of system load required for automatic under-frequency load shedding, a

percentage of this total requirement may be allocated to various time slots on the load

shedding schedule.

A proportionate increase in the available load for under-frequency load shedding scheme is

then implemented to address the load that may not be available in any given time slot.

An example of coordinating under-frequency load shedding scheme requirements with load

shedding schedules is provided in Annex C.

4.4.4 Catering for special events

In the case of a special event (such as a national sporting event involving large numbers of people),

certain loads may be temporarily protected from load shedding. It shall be the responsibility of the

licensee to revise the schedules whilst still ensuring that the required load to be shed is available.

In exceptional cases of national or regional interest, an agreement may be reached between two or

11 NRS 048-9:2009

more licensees to revise load shedding schedule in a manner that does not compromise the overall

load shedding requirement.

NOTE: The implication is that more load shedding will be required in other parts of the network.

4.4.5 Customer load curtailment option

A licensee may identify specific customers that, in lieu of being shed, can provide a pre-defined

amount of load to be curtailed on instruction from the licensee.

These customers will typically be larger customers, for which the following criteria shall apply:

The required load curtailment can be measured.

Protection of this customer from load shedding shall not exclude other customers from load

shedding due to network limitations.

The reduction can be effected within an agreed time frame.

The essential load requirement is met.

Actual load curtailment events meet the requirement agreed on with the licensee.

A licensee shall use load curtailment information provided by such customers to develop a

coordinated load curtailment plan. (Annex A provides an example of an information gathering

sheet). A licensee cannot guarantee that the notified requirements for load curtailment can be

accommodated.

A licensee shall ensure that such curtailment is coordinated with automatic under-frequency load

shedding requirements.

4.4.6 International customers

Cross-border load to other utilities supplied by South African generators shall be treated equitably

with South African customers in the event of national or regional load reduction. Cross-border load

reduction requirements shall be at least the same percentage as the load reduction required in

South Africa.

NOTE: This requirement implies that energy sales from South Africa be reduced. In the event that this power is wheeled from one country to another, the reduction requirement would not apply.

4.4.7 Exclusions based on participation in load reduction

Interruptible loads, which contribute to load reduction on a regular basis, are generally excluded

from manual load shedding schedules. Under emergency conditions, specific agreement may be

reached with these customers on further load curtailment.

Where it is technically feasible to isolate such customers, demand market participation customers

who participate with a minimum of 25% of their total load shall only be included in Stages 3 or 4.

Emergency DMP customers who participate with a minimum of 40% of their total load shall only be

included in Stages 3 or 4.

4.4.7 Changes to load shedding or curtailment schedules

The ability to adjust schedules is important to limit societal impact of load shedding. Such

adjustments may be:

Planned – for example in the case of a major sporting event, certain sites may be removed

from the schedules

Unplanned – for example in response to a concern raised during load shedding w.r.t. to a

critical load.

4.5 Communication

NRS 048-9:2009 12

4.5.1 Information related to load shedding schedules

Licensees shall make load shedding schedules available to their customers. Such schedules may

be published in print media, available on a website, and/or attached to electricity bills.

An appropriate mechanism for communicating changes to schedules shall be implemented.

4.5.2 Prior notice of load shedding

Customers shall be notified when there is a high degree of certainty that load shedding may occur.

4.6 Reporting requirements

For a given load shedding event, a licensee shall be in a position to report:

The actual load shed in each time period

The time for which specific feeders / customers were shed.

NOTE: NRS 048-6 requires that load shedding events be removed from interruption performance reporting.

Use of contracted ILS and DMP customers to manage load shall not be reported as part of load

shedding or curtailment.

5 Requirements – essential loads

5.1 Application by licensees

Licensees are required to collect essential load data and to appropriately address customer

essential load requirements.

A licensee shall provide its upstream electricity supplier with the power supply requirements to meet

its essential load requirements (i.e. its own essential loads and that of its customers).

NOTE: A licensee cannot guarantee that these can be met for all supply emergencies.

5.2 Application by customers

Customers shall notify their licensee of their essential load requirements.

5.3 Identification

Essential loads are identified by customers within their own business environment. Ideally,

customers inform their supply authority of such essential loads by completing and submitting

standard forms designed for this purpose. The relevant supply authority shall collate such

information and compile a registry of essential loads within their area of supply.

Define three categories in detail

- requirements for load shedding vs restoration

- Add annexure

- Motivation required and

- what if customer does not have essential loads (do they need to )

- List responsibility re information

- Clear note on the legal limitation of liability

- Update requirements (every 2 years) or if customer aware of significant change

13 NRS 048-9:2009

- New customers and old customers with new plant

- Every “LPU” should provide

- Communication to customers – how do they know to fill in (one month a year on the

electricity bill)?

6 Requirements – critical loads

6.1 Application by licensees

Licensees are required to appropriately address critical load requirements as defined in section 7.

NOTE: A licensee cannot guarantee that these can be met for all supply emergencies.

6.2 Application by customers

Customers operating critical and essential loads should evaluate their level of preparedness in

terms of the practices in this code of practice (section 7).

4.8 General

All customers shall be entitled to provide licensees with essential load data. Customers in the

following categories shall be required to provide essential load details:

Deep level mines (life support systems)

Hospitals & medical centres with life support requirements

Sewerage

Prisons

Refineries

DRAFTING NOT ON Essential load requirements:

“Don’t know what is inside”

Restored first (before critical loads)

Must not be shed unless within agreed time-scales

Reduce to essential load requirement (in stage 4 – make safe)

The following loads shall be considered critical loads:

Public transport (e.g. rail, airports)

Water pumping (power station requirements)

Refineries

Fuel pipelines

Coal mines supplying power stations

Essential services (e.g. police, fire fighting)

Telecommunications infrastructure (exchanges)

Traffic lights

DRAFTING NOTE on Critical loads

House of cards / disproportionate impact on society / impact on power system

Do not shed or other measures

Do not have to restore

Keeping business as usual going

4.8 Requirements for specific types of loads

4.2.1 General

NRS 048-9:2009 14

The loads defined below are customers that should be specifically addressed to understand the

implications of load shedding.

NOTE – this information requires significant interaction with relevant stakeholders

NOTE – need to address relevant Regulators (civil aviation authority, road traffic authority, ICASA)

NOTE – set up meetings Eskom/AMEU joint

NOTE – drive each of these industries to develop dove-tail standards or regulations.

ACTIONS:

Pravind – Begin setting up meetings with customer groupings

Jose – EDNO staff nationally to identify “deal breakers”

All WG members: examples of critical loads and how they are dealt with in Metros’ etc.,

4.2.3 Airports

4.2.3.1 Category 1 – Airports

Look at requirements in Civil Aviation Act etc … Ciil Aviation Authority / ACSA

4.2.3.2 Category 2 – Metro Rail

Metro rail shall be excluded from schedules.

4.2.3 Rail

4.2.3.1 Category 1 – Metro Rail

Airports are …..

4.2.3.2 Category 2 – Goods Transport

Metro rail shall be excluded from schedules.

4.2.4 Traffic lights

The electricity supply infrastructure to traffic lights generally does not allow for isolation in the event

of load shedding.

All traffic light installations shall be fitted with reflective indicators in the event of an interruption in

supply during the night.

Three categories of traffic light installations shall be identified.

4.2.4.1 Category 1 – high impact intersections

These intersections are defined as those that would lead to significant congestion on major

highways, or in central business districts.

Backup systems shall be implemented at these intersections. These backup systems shall be able

to support supply for a minimum of 4 hrs following an interruption in supply.

Alternatively, contingency plans shall be implemented at tehse intersections to ensure that traffic

flow is maintained within 30 min of an interruption.

4.2.4.2 Category 2 – medium impact junctions

15 NRS 048-9:2009

Contingency plans shall be implemented at these intersections to ensure that traffic flow is

maintained. Plans may include the coordinated deployment of traffic officials, based on the

schedules.

4.2.4.1 Category 3 – low impact intersections

No specific interventions are required.

4.2.2 Water

4.2.4.1 Category 1 – supply to power stations

Water supply to power stations shall be excluded from load reduction requirements.

4.2.2 Sports Stadiums

4.2.4.1 Category 1 – supply to power stations

Sports stadiums.

4.2.2 Sewerage

x:

4.2.2 Refineries and fuel pipe lines

Refineries and fuel pipe lines shall be excluded from load shedding schedules.

4.2.2 Mines supplying power stations

Mines supplying power stations shall be excluded from load shedding schedules.

4.2.2 Educational facilities

Educational facilities shall be :

4.2.2 Essential services

Police fire fighting:

4.2.2 Telecommunications infrastructure

x:

4.2.2 Hospitals and medical centres

State and private hospitals shall be treated equitably.

4.2.2.1 Category 1 – tertiary hospitals

Hospitals shall be .

NRS 048-9:2009 16

Protocols shall be in place for hospitals to contact the local operations centre directly in the event of

an emergency.

4.2.2.1 Category 2 – secondary hospitals

d.

4.2.2.1 Category 3 – clinics and medical centres

d.

4.4.2 Category 1 – danger to life and safety

x

4.4.3 Category 2 - environmental or health hazard

Danger to life and safety

4.4.4 Category 3 – nationally critical product

Destruction or damage to plant, equipment, or facilities which would disrupt production of a

nationally critical product

17 NRS 048-9:2009

Annex A

Load shedding data for planning curtailment schedules

General information

Type of Plant e.g. Mining

(open cast) Mining (deep

level)Furnaces (open arc)

Max Power (in

MW)

Transmission Substation Distribution

Substation

Impact of opening breaker Supply Voltage

MW Category A load Comment

MW Category B load Comment

MW Category C load Comment

MW Category D load Comment

Section 1: Emergency reduction possible if required ―immediately‖

Please indicate amount of load

to be reduced, and how much of

this forms part of the UFLS

scheme

MW UFLS

CVA stage

UFLS

Mandatory stage

Load that can

be reduced

in:

10 min

20 min

30 min

1 hr

2 hrs

4 hrs

6 hrs

Section 2(a): ―Preferred load reduction time frame‖

Provide profile for 10% and 20% reduction

Minimum notification period

MW that can be reduced and time it can be reduced for

MW1 T1

MW2 T2

MW3 T3

Section 2(b): Restoration requirements – provide profile of ramp up

Provide profile for restoration of 10% and 20% reduction

MW1 T1

MW2 T2

MW3 T3

Conditions for restoration (e.g. no

interruption for 24 hours)

Section 2(c): Time between reductions

Time between interruptions

Section 3: ―Safe Mode‖ operation

Minimum MW required for operating

in ―safe mode‖

Notification (hours) required to get

into this mode of operation

Duration that plant can be run in this

NRS 048-9:2009 18

mode

19 NRS 048-9:2009

Annex B

Essential load data for system restoration planning and load shedding

ESSENTIAL LOADS IN CASE OF NETWORK COLLAPSE AND RESTORATION Details regarding requirements for return of electrical power supply & priority of restoration after a

national or regional large-scale network collapse to be recorded in this appendix. Typically, there would be a total loss of power and the details submitted are required to determine the

duration before which and extent of power that should be returned to the customers site. All production would be shut down, and minimal power will be made available for the purposes of

o Avoiding danger to life & safety of persons o Avoiding a potential hazardous condition from developing o Shutting plant down safely.

No provision to be made to continue with normal or reduced production until after the emergency has been concluded.

CATEGORY 1A: RETURN POWER TO PREVENT DANGER TO LIFE AND SAFETY

HOURS MVA Please describe plant in

the space below General comments

Maximum

permissible

duration of power

interruption before

dangerous

condition/s develop

(Explanation − the amount of time before conditions become life threatening)

Survival Load required

once power has been

returned after the

above interruption

(Explanation − the amount of load required torequired to effectively remove personnel or prevent the dangerous condition from developing. (Not intended for continuous use, but for purposes of a controlled and safe shutdown/ evacuation etc)

Details of

plant/equipment/facilitie

s which will be operated

by the power detailed

herein. (For example, Winders, vent fans, dewatering pumps, etc.)

CATEGORY 2A: RETURN POWER TO PREVENT A POTENTIAL ENVIRONMENTAL OR

HEALTH HAZARD

Maximum

permissible

duration of power

interruption before

potential hazard

develops

(Explanation − length of time before an outage (complete interruption) causes

damage to a resource

or results in a

legislated limit ( eg

environmental or

occupational hygiene

limits) to be

exceeded

Survival Load required

once power has been

returned after the

above interruption

(Explanation − the amount of load needed to bring the limits back to acceptable levels. If the load needs to be continuous, please indicate this ) (Not intended for continuous use, but for purposes of a controlled and safe shutdown if possible)

Details of

plant/equipment/facilities

which will be operated by

the power detailed herein.

(For example dust control plants, oil water separation units, sewer pumps etc.)

HOURS MVA Please describe in the space below

General commentsHow is it required?

NRS 048-9:2009 20

CATEGORY 3A: RETURN POWERTO PREVENT THE DESTRUCTION OF, OR DAMAGE TO,

PLANT/EQUIPMENT OR FACILITIES WHICH WOULD DISRUPT PRODUCTION OF A NATIONALLY CRITICAL PRODUCT.

Maximum

permissible

duration of power

interruption before

damage or

destruction occurs

(Explanation − the amount of time before plant/equipment/facilities will incur damage. This applies only to plant/equipment or facilities and not the product itself. If the plant/equipment/facility will be instantly damaged or incur irreversible damage, please describe in field provided)

Survival Load required (Explanation − the amount of power following an interruption that will be needed to prevent damage to the plant/equipment/facility. This may imply the need for continuous load but ideally should be the amount of load needed to ramp down the plant/facility in a non-damaging way. Please describe the load ( continuous or ramp-down) in the field provided)

Details of

plant/equipment/facilities

which will be operated by

the power detailed herein.

(For example smelters,, silting of pipelines, freezing of charge or chutes etc)

HOURS MVA Please describe in the space below

If the plant/equipment/facility will be instantly damaged or incur irreversible damage, please

describe in field belowGeneral comments

SUMMARY FOR ALL THREE CATEGORIES

Category

Time (hours) Survival Load (MVA)

1A1

2A2

3A3

TOTAL

NOTE: Categories 1, 2, and 3 should be mutually exclusive of each other.

21 NRS 048-9:2009

ESSENTIAL LOADS IN CASE OF CONTINUOUS LOAD-REDUCTION/LOAD-SHEDDING/CURTAILMENT Details regarding application forthe electrical power requirements during emergency situation where

load is curtailed to customers without an interruption are to be recorded in this appendix.. This is the power required to sustain life, prevent violation of legislated limits and prevent damage to

equipment/plant/facilities for a limited period during a limited emergency. Typically, the outage reduction would last a few hours, generally according to a schedule. Customers

to also supply details where extended durations could cause further damage, which may not be realised if the durations where confined to a few hours.

The numbers here refer to load needed to maintain the plant in stasis without a complete shutdown. No power will be available for production requirements, just for temporarily sustaining life until the

load shedding has been switched to another location. s, just for temporarily sustaining life until the load-reduction (load-shedding) has been switched to another location.

CATEGORY 3B: REDUCE POWER TO A LEVEL THAT PREVENTS THE DESTRUCTION OR

DAMAGE TO PLANT/EQUIPMENT/FACILITIES WHICH WOULD DISRUPT PRODUCTION OF A NATIONALLY CRITICAL PRODUCT

Minimum Notification

period required before a

reduction of power

supply

(Explanation − the amount of time required to ensure that plant/equipment or facilities can be shutdown or ramped down so that no destruction or damage occurs)

Minimum Load

required

(Explanation − the amount of power required to continuously operate plant/equipment/facilities such that damage or destruction does not occur – i.e after ramp down period – Amount of power required to maintain the status of the plant/equipment/facility

) (i.e. reduce to include CAT 1B and 2B)

Details of

plant/equipment/fa

cilities which will be

operated by the

power detailed

herein. (Please describe what plant will be run by the power required)

In the event of being

shed without being

reduced , is the amount

of load needed different?

(Explanation − Sometimes the amount of load needed to restart critical equipment-processes is greater than the running load – Please supply details.)

HOURS MVA Description of

minimum load MVA Please

give

details.

CATEGORY 2B: REDUCE POWER TO A LEVEL TO PREVENT A POTENTIAL ENVIRONMENTAL OR HEALTH HAZARD

Minimum Notification

period required before a

reduction of power

supply (Explanation − of the amount of time required to ensure that all activities are completed to avoid damage to a resource and/or to avoid exceeding a legislated environmental or health limit .)

Minimum Load

required

(Explanation − the amount of power required to continuously to keep the system from exceeding legislated contamination limits for the period of the scheduled load-shedding)

Details of

plant/equipment/fa

cilities which will be

operated by the

power detailed

herein. (Please describe what plant will be run by the power required)

In the event of being

shed without being

reduced, is the amount of

load needed different? If

so, how much is it?

(Explanation − Sometimes the amount of load needed to restart critical equipment-processes is greater than the running load – Please supply details.)

HOURS MVA Description of

minimum load MVA Please

give

NRS 048-9:2009 22

details.

CATEGORY 1B: REDUCE POWER TO A LEVEL THAT DOES NOT ENDDANGER TO LIFE AND SAFETY

Minimum Notification

period required before a

reduction of power

supply

(Explanation − the amount of time required to ensure that all activities can be performed to ensure that no

dangerous condition can

develop).

Minimum Survival

Load required

(Explanation − the amount of load needed to keep the conditions in the plant/facility habitable without performing any actual work or production. People should be able to stay where they are safely for the duration of the load-reduction (load-shedding)0 and will not have to be moved. Therefore, power required for evacuating personnel should not be included. Please include power required to restart critical equipment)

Details of

plant/equipment/fa

cilities which will be

operated by the

power detailed

herein. (Please describe what plant will be run by the power required)

In the event of being

reduced without being

shed, is the amount of

load needed different?

If so, how much is it? (Explanation − often the amount of load needed to restart critical equipment is greater than the running load. If load critical to sustaining life needs a high start-up power, please put into the below field, while continuous running values can be placed here)

HOURS MVA Description of

minimum survival

demand

MVA Please

give

details.

SUMMARY FOR ALL THREE CATEGORIES

Category

Time (hours) Time (hours)Minimum Survival load (MVA)

Reduced Load (MVA)Demand (MVA)

3B1

Power to maintain Life & Safety

2B2

Power to prevent Environmental or Health Incident

1B3

Power to prevent damage to equipment etc

TOTAL

23 NRS 048-9:2009

3. Official(s) to be contacted during emergencies related to power supplies: OFFICIAL(S) TO BE CONTACTED DURING EMERGENCIES RELATED TO POWER SUPPLIES

Official 1: (Primary Contact) Name

Designation

E-mail

Telephone

Fax

Cell phone

Official 2: (Secondary Contact) Name

Designation

E-mail

Telephone

Fax

Cell phone

Official 3: (Alternativee 1) Name

Designation

E-mail

Telephone

Fax

Cell phone

Official 4: (Senior Manager In charge – Last Resort Contact) Name

Designation

E-mail

NRS 048-9:2009 24

Telephone

Fax

Cell phone

Details of generally manned station such as the Mine Rescue Team ( Proto Team) or main security offices: Name

Designation

E-mail

Telephone

Fax

Cell phone

4 Do you have any other means by which the above persons may be contacted, for example , radio, satellite, etc? Give details: ……………………………………………………………………...............................................

5 REMARKS

Can you offer any further information or motivation that not captured elsewhere in this questionnaire that will be useful in identifying and evaluating your requirements during emergencies related to power supplies?

…………………………………………………………………………………………………………………

25 NRS 048-9:2009

Annex C

Example of the calculation of schedules taking automatic under-

frequency load shedding into consideration.

Given a UFLS 1st stage set of loads totalling 100MWs, 105% of the requirement, and a schedule of

10 time slots:

Time slot Manual

loadshedding

UFLS on

loadshedding

UFLS

available

UFLS %

available

6-8 200 11 89 93%

8-10 200 8 92 97%

10-12 200 12 88 92%

12-2 200 9 89 93%

2-4 200 10 90 95%

4-6 200 10 90 95%

6-8 200 11 89 93%

8-10 200 9 91 95%

10-12 200 10 90 95%

What can be seen is that the UFLS loads are split among all the various time slots. This means

that all the loads contribute to loadshedding, but the UFLS system is not materially affected. The

gap is only the amount of UFLS used at any one time, in this case the largest is 12MWs, which

reduces the scheme in the worst case to 92% of requirement. Therefore an additional installation of

12MWs of UFLS will cover the deficit.

The downside is a slight overshedding during a UFLS event, when not loadshedding, which is

likely.

Bibliography

NRS 048-4, Electricity supply – Quality of supply – Part 4: Application guidelines for utilities.

NRS 048-6, Electricity supply – Quality of supply – Part 6: Medium voltage network interruption

performance (In course of preparation.)

© Standards South Africa