Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission and Distribution
Slide 1
www.pnxa.com
PowerNex Associates Inc.
Module 3
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Module 3
Transmission and Distribution
Learning Objectives:
To gain an understanding of the following:

Transmission system overview (4A)

Protection Control and Metering (4B)

Concepts of Special Protection Systems (4C)

Distribution (4D)
 Components
 Types of transmission limits
 Major transmission limits in Ontario
 How it’s different to transmission
Slide 2
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Module 3A
Transmission
Slide 3
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Module 3A
Transmission
What will be covered

Basic Transmission Components

Overview of Transmission System

Limits - where do they come from & why do we need them

Internal Key Interfaces and effects on Generation

Normal, High Risk and Emergency Operation

Ontario Interconnections

Transmission Impactive Outages
Slide 4
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
 Basic Transmission Components
 Overview of Transmission System
 Limits - where do they come from & why do we need them
 Internal Key Interfaces and effects on Generation
 Normal, High Risk and Emergency Operation
 Ontario Interconnections
 Transmission Impactive Outages
Slide 5
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
The Single Line Diagram
 The Single Line Diagram is a simple representation of
the power system or a portion of it.
 It shows the system as only one phase rather than
three.
 Its purpose is to show the power system with minimum
detail, ie an overview of what’s connected to what.
Slide 6
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
Basic Transmission Components
Single Line Diagram
Slide 7
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
 SF6 Circuit
Breaker
Slide 8
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
 Air Blast Circuit
Breaker
Slide 9
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
Bulk oil circuit
breaker
Slide 10
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
Disconnect
switch
Slide 11
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
 What happens
when a disconnect
switch is used
instead of a circuit
breaker?
 Not pretty!
Slide 12
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
A 3 phase Transformer
Slide 13
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
Power Transformer
Slide 14
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
 Basic Transmission Components
 Overview of Transmission System
 Limits - where do they come from & why do we need them
 Internal Key Interfaces and effects on Generation
 Normal, High Risk and Emergency Operation
 Ontario Interconnections
 Transmission Impactive Outages
Slide 15
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
 Transmission Lines in parallel, if lose one, flow is
redistributed
 Generally not so for Distribution lines (radial)
 Parallel lines lower the impedance, the more parallel lines
the higher the reliability and the lower the losses (I2R)
 The higher the voltage, the greater the power carrying
capacity (proportional to V squared)
 Maximum power carrying ability at Surge Impedance
Loading (when reactive inductance and reactive
capacitance of line are equal and thus cancel each other,
leaving only the resistance).
Slide 16
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
Typical Power Grid System
Slide 17
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
Water Flow Analogy for Electricity Transmission System
Slide 18
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
Electrical Equivalent to Water Analogy
Electrical Bus (Bucket)
-Critical Voltage, Current, Frequency
& Short Circuit Level
Generator (tap - water supply)
-Provides Energy (MW), voltage support,
&frequency support
Transmission Lines (Pipes)
Impedance (Fixed Resistance to Flow)
Variable Loads (tap - water removal)
Absorb MW and Voltage Support,
Critical Voltage and Frequency Levels
Slide 19
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
 Typical Surge Impedance Loadings
 500 Kv - 1,000 Mw
 230 Kv – 200 Mw
 115 Kv – 50 Mw
 Ontario System made up of 500 Kv, 230 Kv, 115 Kv.
 Distribution voltages < 50 Kv
Slide 20
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
Double circuit EHV
Transmission line
Slide 21
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
 Basic Transmission Components
 Overview of Transmission System
 Limits - where do they come from & why do we need them
 Internal Key Interfaces and effects on Generation
 Normal, High Risk and Emergency Operation
 Ontario Interconnections
 Transmission Impactive Outages
Slide 22
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
Historical Note
1965 Northeast Blackout
 One 230 kV circuit at Beck (Q29BD) tripped
 Four other circuits at Beck cascade trip within 2.7s
 1700 MW power surge into New York causing a wide-spread
blackout
 NPCC formed to ensure utilities in the northeastern part of North
America adopt practices to prevent another blackout
Slide 23
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
Slide 24
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
 Three basic types of limits:
 Thermal
 Voltage Decline/ Rise
 Stability
 Also Short Circuit limits
Slide 25
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
Thermal Limits
Safe Ground
Clearance
 Lines designed to operate to
specific “ground” clearance
and maximum conductor
temperature
 Line clearance reduced as
conductor temperature rises
(sag)
 Ground clearance decreases
as




Current flow increases
Ambient temperature rises
Wind velocity decreases
Sunlight increases
Slide 26
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
Thermal Limits – Limited Time Ratings
Slide 27
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
Thermal Limits also apply to equipment other than
lines
 For example: Transformers
 Rated in MVA
 Require sufficient cooling to dissipate heating
 Hot spot and oil temp limits
 As with lines, limited time ratings
Slide 28
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
Voltage Limits
 Must be able to sustain Voltage levels both pre and post contingency
 Low or high voltages can cause equipment damage to Hydro One or
Generator assets and also customer equipment
 Under normal conditions, continuous voltages are to be maintained
within predefined levels.
 For example:
 115 Kv voltage must be between 127* Kv and 113 Kv
 230 Kv voltage must be between 250Kv* and 220 Kv
 500 Kv must be between 550 Kv and 490 Kv
* In Northern Ontario 132 Kv and 260 Kv
Slide 29
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
Voltage Limits
 Transformer Voltages
 Steady State Ratings, Maximum Acceptable Levels
 110% of Input Winding Rating,
 105% of Output Winding Rating at Full Load
Slide 30
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
Stability Limits
 These are the most complex limits
 Instability can cause cascading outages
 Affects generators, they go out of synchronism, “pole
slipping”, “out of step” are terms used.
 Stability usually a problem on a system with long transmission
lines
 If the receiving end voltage “angle” lags the sending end
voltage “angle” by 90 or more degrees, then unstable
Slide 31
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
Stability
Slide 32
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
Stability
Slide 33
Power System Operation/Electricity Market Operation Overview
Transmission
PowerNex Associates Inc.
Summary of Security Criteria
 Voltage Levels, meet customer and equipment voltage
limits
 Stability, acceptable damping
 Element Loading, operate to appropriate thermal
rating of equipment
 Short Circuit, breakers have capability of clearing
worst short circuit condition
Slide 34
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
“Bad Things happen”
 What bad things can happen?
 Virtually anything, but must be practical and reasonable.
 Following 1965 Blackout NPCC developed a practical list of “bad
things”
 All members of NPCC must operate their systems by being able to
recover from events on this list without having adverse effects on
the systems of other members.
 This costs money due to congestion. But the costs of a cascading
blackout far outweigh the congestion costs.
Slide 35
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
Recognized “Bad Things” (Contingencies) - NPCC
Criteria

Permanent 3-Phase fault (worst kind of fault) – with normal fault clearing

Simultaneous permanent phase to ground faults on adjacent circuits (same
tower) – with normal fault clearing

Permanent phase to ground fault on any generator, circuit, transformer or bus
section - with delayed fault clearing (Breaker Failure)

Loss of any element without a fault

Permanent phase to ground fault on circuit breaker - with normal fault clearing

Failure of a circuit breaker, associated with a Special Protection Scheme, to
operate
Slide 36
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
How are limits developed?





Limits are developed using computerised simulation studies.
A data base representing all of the power system components, their
electrical characteristics and their connectivity has been developed
and is constantly being updated when new equipment is added to
the system.
This data base also includes data on interconnected systems
(electrically it’s all one big system)
Application software is used by engineers to run fault simulation
studies and test the operation of the system following a particular
fault.
From the results of these studies operational security limits are
produced.
Slide 37
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
How are limits developed?



Thermal Limits
Fairly simple
Off line load flows predict the change in flows on
remaining elements post contingency, ie distribution
factors
In real time these distribution factors are used to predict
change in loading on the remaining elements following a
contingency
 Thus the operator can determine pre-contingency loading
on other lines
Slide 38
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
How are limits developed?
Voltage Limits
 Developed by off line simulation studies
 Use NPCC criteria to “throw” faults at the system
 Calculate the post contingency effects on voltage
 Are post contingency voltages within limits? If OK move on to next
simulation. If not OK then reduce pre contingency loadings (by
redispatch) in the simulation until can meet post contingency voltage
criteria.
 This then becomes the Operating Security Limit.
 Pre-contingency loadings not to exceed these.
Slide 39
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
How are limits developed?
Stability Limits
 Developed by off line simulation studies, simulating the system
dynamics
 Use NPCC criteria to “throw” faults at the system
 Calculate the post contingency effects on stability
 Is the system stable pre contingency, during the contingency and post
contingency? If OK move on to next simulation. If not OK then
redispatch system to reduce pre contingency loadings in the
simulation until post contingency stability achieved.
 This loading limit becomes the Operating Security Limit.
 Pre-contingency loadings must not exceed these.
Slide 40
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
How are Limits Developed?
 Some notes re simulation studies performed:
 time consuming
 only study a limited number of contingencies and system
conditions (eg winter peak, summer minimum, summer peak)
 study conditions set up for most severe contingency usually at
peak power transfers
 successful study results reduced (nominally10%) to provide
acceptable margins

results simplified for easier computer monitoring
Slide 41
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
Operating Security Limits
System needs to be secure

Pre-contingency

Post-contingency

Stable During Contingency (Transient Stability-non
faulted generators not removed from system, acceptable
equipment operation during/immediately after fault
clearing, non cascading outages)
Slide 42
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
 Basic Transmission Components
 Overview of Transmission System
 Limits - where do they come from & why do we need them
 Internal Key Interfaces and effects on Generation
 Normal, High Risk and Emergency Operation
 Ontario Interconnections
 Transmission Impactive Outages
Slide 43
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
Internal Ontario Key Interfaces
 Because of the dynamic nature of the power system and its
multiple parallel paths, limits generally are not expressed in
terms of individual line loadings (other than some thermal limits)
 Rather, limits are expressed in terms of interface flows and are
called Operating Security Limits.
 An interface is defined as a group of Transmission lines and the
limit is expressed as the sum of the flows on this group of lines.
Slide 44
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
Interface Limit Characteristics
 ‘Base’ limit
 All transmission facilities are in-service
 Directional
 Certain outages result in a penalty in MW
 Some limits simple constants;
 others more complex, and have multiple parameters including
other limits!
Slide 45
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
Historical Flows
Slide 46
Power System Operation/Electricity Market Operation Overview
Transmission
PowerNex Associates Inc.
Historical Flows
Slide 47
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
 Basic Transmission Components
 Overview of Transmission System
 Limits - where do they come from & why do we need them
 Internal Key Interfaces and effects on Generation
 Normal, High Risk and Emergency Operation
 Ontario Interconnections
 Transmission Impactive Outages
Slide 48
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Transmission
The End
Slide 49
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Module 3B
Protection, Control and Metering
Slide 50
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
What will be covered

Introduction to protection,

how and why.

Introduction to control

Intoduction to metering,

revenue metering, operational metering, telemetering
Slide 51
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
 All Elements of a power system must be protected from faults
 All Power system elements must be monitored (status, loading,
etc). Much of the power system is operated (switching, hydro
unit loading) under remote control.
 All generator output and all customer load must be metered
(revenue grade metering)
 Loading on lines, transformers etc must also be metered (non
revenue grade metering)
Slide 52
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
 To provide protection, control and metering, must
constantly take real time measurements of system
conditions
 Current, voltage and frequency measurements are
the basis of all protection and metering.
 Current and voltage provided with the help of
Instrument Transformers
 Not to be confused with Power Transformers
Slide 53
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
Instrument Transformers

On a 500kv line the voltage from line to ground is ~ 290,000 volts and
current can be in the hundreds of amps.

Use instrument transformers to get proportional volts and amps which
can be handled by relays, meters etc

These are called Voltage Transformers (VTs) and Current Transformers
(CTs).

Sometimes VTs are referred to PTs (Potential transformers), they’re
synonymous

VTs are connected between the line and ground and have a turns ratio
such that a secondary voltage of 120v represents rated primary voltage.

CTs are connected in series with the line and have various turns ratios
that can be selected. For example 1000:5,1600:5 etc
Slide 54
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
Voltage Transformer
Slide 55
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
Instrument Transformers
Examples

On a 500 kV line



500 Kv is equivalent to 120 volts
1000 amps is equivalent to 5 amps
On a 230 Kv line


230 Kv is equivalent to 120 volts
1000 amps is equivalent to 5 amps
Slide 56
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
Relays
 Relays are sensing devices which operate when the
monitored quantities reach certain thresholds.
 They then send a signal to operate a device such as
a circuit breaker
 Examples later
Slide 57
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
Meters

Read monitored quantities







Voltage
Current
Power (calculated in the meter)
KVA (calculated in meter)
KVAR (calculated in Meter)
Frequency
Display and/or store instantaneous quantities as well as integrated quantities

Instantaneous
 Current
 Voltage
 Frequency

Integrated
 Power Mw
 Reactive Power Mvar
Slide 58
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
Slide 59
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
 Operational Metering
 Used for
 Operating
 Statistics
 Loading trends
 All generators, transformers, lines have this
 ~ +/- 3 % accuracy
 Revenue Metering
 Used for
 Billing mainly but can also be used for above purposes
 Pre market only included customers, interties but not generators
 Now all generators (aggregates) have revenue meters
 High accuracy ~ +/- 0.3%, expensive
 Expensive because of CT and VT accuracy, especially High
Voltage
Slide 60
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
Telemetering
 To provide real time metered quantities at a
central location eg IESO, OPG, HydroOne
Grid Control Centre etc
 Meter outputs sent to Remote Terminal Unit
(RTU) and from there to central location via
communication channel.
Slide 61
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
 Metered data from Revenue Meters and
from Operational Meters are supplied to
various applications used by generators,
transmitters and IESO
 Confidentiality of information
Slide 62
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
 All Elements of a power system must be protected
from faults
 Must eliminate all sources of infeed to the fault
 Must be accomplished with high speed (within 2 to 3
cycles, 1 cycle = 1/60 of a second)
 Must not isolate more equipment than necessary
Slide 63
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
Fault Clearing Devices

Must be capable of Interrupting fault level (short circuit concerns)

Capable of Clearing only Faulted Zone (Zone tight relaying)

Fast Acting to Protect Equipment and Limit Cascading Faults

Must Interrupt all sources of fault infeed
Slide 64
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
Fault Clearing Devices
 Normally
accomplished with
- combination of protective
relaying scheme, 3
phase circuit breaker
and high speed
communication media to
send trip signals to
remote terminals
Slide 65
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
 Example of a transformer
protection.
 Differential Protection
 If I1 + I2 > 0 then a trip
signal is sent to the
circuit breaker to remove
transformer from service
Slide 66
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
 Fault Clearing Device – Concerns
 Fault Clearing Device Failures Mitigated by:
 Breaker failure schemes
 Duplicated protections on all major Transmission
elements (A and B protections, expensive!)
 Duplicate communication equipment
Slide 67
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
 Example of
differential
protection on a
transmission
line
Slide 68
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
Examples of protections on the power system

Generators







Overspeed (mechanical)
Reverse Power
Thermal
Stator Ground
Inadvertent synchronisation
Overcurrent
Transformers
 Differential
 Overcurrent
 Gas accumulation

Busbar
 Differential
 Overcurrent

Transmission Line
 Impedance
 Differential
Slide 69
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering

A ground fault on the
low voltage side of
this substation
creates an arcing
fault.

Unfortunately,
protection hardware
fails to open the high
voltage side.
Slide 70
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
 Protection panel in
a relay building
Slide 71
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
Slide 72
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
 IESO has no direct physical control of power system facilities
(switching, unit loading etc). It only give orders!
 However some switching is done automatically, such as fault
switching, generation rejection, capacitor and reactor switching,
transformer tap changes and such like.
 But by and large all physical control of power system elements
is performed by the transmitters and the generators.
 Examples: synchronising and desynchronising generating units,
switching at transformer stations, isolation of equipment for
maintenance
Slide 73
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
 Demarcation point between Hydro One and Generator
facilities generally at the high voltage disconnect
switch. Generator owns the switch.
 All upstream facilities in the switchyard and beyond are
owned and operated by Hydro One.
 There are exceptions
Slide 74
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
Transmitter
 All control of switching on the HV system now takes
place remotely from Hydro One’s Grid Control centre in
Barrie.
 Can remotely control all switching on 500 Kv, 230 Kv
and 115 Kv systems. Controls some 44 Kv where
parallel paths exist (non radial)
 Controlled by SCADA system (System Control and Data
Acquisition)
Slide 75
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
Generator
 Operators must be able to monitor and control
equipment remotely
 In staffed locations, eg Fossil stations, generator and
plant control systems may be hard wired to the control
room
 As most hydroelectric stations are now operated remote
from the site, digital control systems are normally used
Slide 76
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering

Data, metered quantities, status of equipment (open or closed) is fed from
device to a Remote Terminal Unit (RTU)

From RTU data is digitised and transferred to a local Central Processing
Unit (PU), basically a computer.

From there to a master CPU at the control centre where data is processed
and presented to the operator on his/her screen.

This is a two way street, Operator receives data and Operator can send
instructions (eg load a unit, desynchronise a unit, increase or decrease
VArs etc)

Susceptible to failures, some depend on a third party communication
path,

Alternative is to send agent to site to perform manual operations.
Slide 77
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
Slide 78
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection Control and Metering
Slide 79
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
Slide 80
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
 All Nuclear units controlled locally
 All Fossil units controlled locally
 All NW hydroelectric units controlled remotely from Thunder
Bay (NWCC)
 All NE hydroelectric units controlled remotely from Porcupine
(NECC)
 All Ottawa River and Madawaska River units controlled
remotely from Chenaux
 Saunders units controlled locally
 All Beck and Decew units controlled from Beck
Slide 81
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Protection, Control and Metering
The End
Slide 82
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Module 3C
Special Protection Systems
(SPS)
Slide 83
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Special Protection Systems
What will be covered
 What they are
 Why they are needed
 How they work
Slide 84
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Special Protection Systems
(Virtual Transmission)

Used to expand operating security limits, post contingency, therefore can
operate to higher limit pre- contingency

Fast acting, are triggered by the contingency

Generation rejection (used the most)

Load rejection

Capacitor switching (provides reactive compensation to raise voltage
levels and reduce phase angle between voltage and current)


can be switched automatically as part of special protection scheme
Reactor switching (provides reactive compensation to lower voltage
levels and can also be used to control short circuit levels)

often used pre-contingency to lower system voltages, switched out-of-service
post contingency
Slide 85
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Special Protection Systems
Generation Rejection
 Increase Power Transfer Capability of limiting
components of Grid,
 Stop Gap measure originally but continues in use
 Improve Generation Resource availability
Slide 86
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Special Protection Systems
 A 230 kV shunt
capacitor bank
 Is switched in to control
low voltage and out to
control high voltage
 Does not necessarily
have to part of an SPS,
can be normal daily
operation
Slide 87
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Special Protection Systems
Some Generation Rejection Examples







Beauharnois/Saunders
Chenaux/Mountain Chute G/R scheme
Stewartville G/R
Darlington G/R
Lambton G/R
Lower Notch G/R
Otto Holden G/R (Run Back)
 Bruce Power G/R
Slide 88
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Special Protection Systems
 P502X/D501P/L20D/L21S G/R & LR
 NE 115 kV L/R and G/R Scheme
 Abitibi Canyon G/R Scheme
 Lower Notch G/R Scheme
 Moose River Basin G/R for loss of ExV or XxE
Slide 89
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Special Protection Systems
The End
Slide 90
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Module #3D
Distribution
Slide 91
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Distribution
Interface with Transmission System
500 kV
Distribution lines
230 Kv
27.6 kV
Distribution lines
Slide 92
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Distribution
Interface with the transmission system

Distribution voltages generally assumed to
be < 115 kV

Various distribution voltages:

66 kV subtransmission – not common
in Ontario

44 kV subtransmission – common in
rural Ontario

27.6 kV subtransmission – very
common in Ontario, especially in
urban areas

13.8 kV

4 kV
Slide 93
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Distribution
 Transmission lines are connected in parallel, if one is lost then
flow is redistributed automatically
 Generally not so for Distribution lines (radial), especially in rural
areas.
 When there is a permanent fault then switching has to occur to
reroute power flow, will result in an outage (hopefully short)
 Most faults (>90%) are transient and protection will open the
feeder breaker, followed by an automatic reclosure. If the fault
was transient (eg caused by a lightning strike) then customer will
only see a momentary flicker.
Slide 94
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Distribution
Transmission Parallel, Distribution Radial
500 kV
Distribution lines
230 Kv
27.6 kV
Distribution lines
Slide 95
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Distribution
Typical Hydro One interface between
Transmission and Distribution
Double circuit 230
kV parallel
transmission lines
Each transformer is
capable of supplying
the entire station
Busbar 1
Normally open
Busbar 2
27.6 kV radial
distribution
feeders.
Normally open
To various customer
loads
To various customer
loads
Slide 96
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Distribution
Slide 97
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Distribution
 Distribution equipment is less complicated
 Maintenance of receiving end voltage is important; capacitor
switching used extensively
 Protection systems are simpler
 Overcurrent, over/under voltage the main protections
 Reliability of Distribution system is “local”, not a NERC or NPCC
issue, does not affect the interties
Slide 98
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Distribution
 Some large industrial
Customers are fed
directly from 230 kV to a
step down transformer.
 No intermediate
“subtransmission”
Slide 99
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Distribution
Structures for different voltages
500 kV
230 kV
115 kV
44 kV
13.8 kV
4 kV
Slide 100
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Distribution
 Subtransmission
and distribution
lines can be on
the same
structure
44 kV
4 kV
Slide 101
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Distribution
 Three phase
supply to a
commercial
facility
Slide 102
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Distribution
LDC’s and LSE’s
 LDC – Local Distribution Company
 LSE – Load Serving Entity
 In NYISO LSE’s are responsible for ensuring long term supply
for LDC’s in their area. This is supposed to ensure an adequate
supply.
 In Ontario we have the Ontario Power Authority, no LSE’s (yet)
Slide 103
Power System Operation/Electricity Market Operation Overview
PowerNex Associates Inc.
Distribution
The End
Slide 104