Insulation Coordination
in the Alberta Interconnected Electric System
Part 1
Ligong Gan, P.Eng.
Transmission Engineering & Performance
Alberta Electric System Operator (AESO)
AGENDA
• Why do we need insulation?
• What is insulation coordination?
• Recap of May 13/15 2014 Course by Dr. Peelo
– Temporary over-voltages
– Switching over-voltages
– Lightning over-voltages
• Typical approaches to insulation coordination
• IEEE and IEC standards
• Q&A
2
Before Lightning Rod was Invented…
• Lightning has always been a prominent part of all ancient religions
and mythologies in the world
• In the old days, lightning was considered an act of god(s) to
express their anger
• For example
 In the Middle Ages in Europe, it was common practice to ring church
bells during a lightning storm to break up thunderstorms and to avert
lightning
 The uneducated people believed that this would disperse evil spirits,
while the more educated believed that it would cause vibration in air
which broke up the continuity of the lightning path
 However, during a 33 year period, 386 church steeples were hit by
lightning, killing 103 bell ringers at the rope
3
Characteristics of Lightning
• 2000 lightning occurrences on the earth by
the time you finish reading this slide
• A lightning flash typically lasts for 0.2s
• Usually made of several shorter discharges,
each of which lasts for 10 to 50 µs
• Typical length of lightning path is 2-3 km
• Individual discharges are called “strokes”
• Most visible when return stroke occurs
• Lightning bolt can carry a potential
difference of >1000 kV and >100 kA with
>20 GJ
4
Lightning Facts of Alberta
• In an average year, 270,000 cloud-to-ground (CG)
lightning strikes occur in Alberta (in contrast, Manitoba
has only 70,000 per year)
• Most CG lightning occurs in the mountain and westcentral areas
• Virtually all CG lightning strikes occur in July (45%),
August (32%) and June (23%)
• On a typical day, most lightning strikes happen between
3:00 pm and 11:00 am
• Average lightning strike density in Alberta is only 0.8 to
1 s/km2
• The worst strike density is about 4
s/km2, mainly in two areas, one 20
km north of Edson, and the other
50 km southeast of Edson
Source – Alberta
Environment and
Sustainable Resource
Development (ESRD)
website
• The least density is 0.1 s/km2 in
the north and far southeast
5
Power Industry Structure in Alberta
Minister of Energy
(Appoints AESO Board Members, MSA & AUC Chair)
Electric Utilities Act
Balancing
Pool
Independent
System
Operator
(AESO)
Generators
Alberta Utilities
Commission (AUC)
Transmission
Facility Owners
Market
Surveillance
Administrator
(MSA)
Distribution
Facility Owners
Retailers
6
What is AESO?
The AESO –
• Was formed in 2003 under the Electric
Utilities Act (EUA)
• Contracts with TFOs to acquire transmission
services
• Develops and publishes binding ISO rules
and standards
• Develops and issues Functional
Specifications for projects
• Works closely with TFOs and market
participants on transmission projects
7
Why Do We Need Insulation?
1. Public and utility
personnel safety
2. Ensure current flows
only along conductors
3. Prevent damage to
equipment due to high
voltage. In particular,
prevent or reduce
permanent damage to
– Transformers
– Cables
8
How Insulation Breakdown Takes Place
• Chemical – Oxidation, hydrolysis, etc.
• Mechanical – Cracks, channels, tracks, deforming, etc.
• Thermal – Overheating (e.g., transformers are generally
limited to 2 seconds over-current)
Typical failure rate of equipment due to insulation breakdown
Failure Rate
Failure Rate
HV xformers
0.1%
Cables ≥ 25 kV
LV xformers
0.15%
CTs
0.35%
HV shunt reactors
0.4%
PTs
0.2%
HV breakers
0.09%
Surge arresters
0.01%
83% of all failures
Source: Research conducted by Bueno & Mak Group.
9
Insulation Coordination – Definition
IEEE 1313.1 – The selection of the insulation strength of equipment in
relation to the voltages, which can appear on the system for which the
equipment is intended and taking into account the service
environment and the characteristics of the available protective devices
IEC 60071-01 – Selection of the dielectric strength of equipment in
relation to the operating voltages and over-voltages which can appear
on the system for which the equipment is intended, taking into
account the service environment and the characteristics of the
available preventing and protective devices
Plain Language – Arrangement of insulation levels in such a manner
that an insulation failure, if one occurs, would be confined to the place
on the system where it would result in the least damage, be the least
expensive to repair and cause the least disturbance to the continuity
of supply
10
Insulation Coordination (cont.)
Keep in Mind
• It’s impossible to design a
system that is 100% protected
• No perfect solution – practicality
is the key
Number of insulator units
• Insulation coordination is both
an art and science
• Insulation coordination is often
an economic decision
Over-Voltage
11
An Example of Insulation Coordination
• Tower type  steel
• Shielding wire  Yes
• Line BIL = 1050 kV
• Transformer BIL = 850 kV
• Breaker BIL = 1050 kV
Breaker
Arrester
Transformer
Tower & Line
240 kV system
• Switch & post insulators BIL
= 900 kV
• Arrester
– Continuous voltage = 190 kV
– Discharge voltage = 600 kV
• Separation distance ≤ 3 m
between arrester & xformer
(as per IEEE C62.22)
12
Recap of May 13/15 2014 Course
“Insulation Coordination” by Dr. Peelo
• The following voltages are always phase-to-phase r.m.s.
values
– Nominal system voltage
– Minimum continuous operating voltage
– Maximum continuous operating voltage (MCOV)
• The following voltage is phase-to-ground r.m.s. value
– Short-duration low-frequency withstand voltage
• The following voltages are phase-to-ground (sometimes
phase-to-phase) peak values
– Lightning impulse insulation withstand voltage
– Switching impulse insulation withstand voltage
13
Recap of May 13/15 2014 Course
“Insulation Coordination” by Dr. Peelo
• Nominal system voltage – the phase-to-phase
r.m.s. voltage by which the system is designed. It’s
generally 10% below the maximum system voltage
as defined below
• Maximum continuous operating voltage (MCOV) –
the highest phase-to-phase r.m.s. voltage under
normal operating conditions
– AESO’s reliability standards (TPL and VAR in particular)
– AESO’s “Transmission Planning Criteria and Guidelines” specifies
Steady State Voltage Criteria (Table 8.2-1) for transmission elements
– MCOV = Extreme Maximum Voltage in AESO’s Functional Spec
14
What Is MCOV?
• Highest voltage under “normal” operating conditions
• Highest voltage for which equipment is designed for
satisfactory continuous operation without intended
derates
• In defining MCOV, voltage transients and short
duration temporary over-voltages are normally
excluded
• However, voltage transients and temporary overvoltages may affect equipment operating
performance and should be considered in design
15
Acceptable Range of Voltages in the AIES
Nominal
(kV)
Extreme
Minimum
(kV)
Normal
Minimum
(kV)
Normal
Maximum
(kV)
Extreme
Maximum
(kV)
69/72
62
69
76
79
138
124
135
145
152
144
130
137
151
155
240
216
234
252
264
260
234
247
266
275
500
475
500
525
550
Note: Extreme Maximum kV = MCOV (as mentioned previously)
16
Recap of May 13/15 2014 Course
“Insulation Coordination” by Dr. Peelo
• Over-Voltage – Any voltage that exceeds the MCOV.
Often expressed in p.u. with reference to the peak
phase-to-ground maximum voltage
1 p.u. = MCOV ×
2÷ 3
• Critical flashover (CFO) voltage – A voltage with a
given waveform that causes flashover on 50% of all
tests
The breakdown of most insulation materials is basically probabilistic in
nature. It often follows a normal (Gaussian) distribution. The CFO is
simply the mean value of the statistical distribution.
17
Recap of May 15/17 2012 Course
“Understanding Grounding” by Dr. Xu
At any point of a network,
•
3
If-1φ can be
times of If-3φ
𝐾+2
• TOV can be
Where 𝐾
When
𝐾
=
𝑍0
𝑍1
<3
3(1+𝐾+𝐾2 )
times of rated V (MCOV)
𝐾+2
Effectively grounded (as per IEEE and IEC)
18
Recap of May 13/15 2014 Course
“Insulation Coordination” by Dr. Peelo
• Representative over-voltage (Urp) – A voltage that
produces the same dielectric effect on insulation as overvoltages of a given class occurring in services
(There are up to four representative over-voltages in a power system)
• Coordination withstand voltage (Ucw) – for each class of
voltage, the value of the withstand voltage of the insulation
configuration in actual service conditions, that meets the
performance criteria
(Adjusted Urp considering inaccuracy of initial data)
• Required withstand voltage (Urw) – the test voltage that
the insulation must withstand in a standard withstand test to
ensure that the insulation meets the performance criteria
when subjected to a given class of over-voltages in actual
service conditions and for the whole service duration
(Adjusted Ucw considering the difference between standard test
conditions and real-life operating conditions)
19
Recap of May 13/15 2014 Course
“Insulation Coordination” by Dr. Peelo
• Coordination factor (Kc) – the factor by which the value of Urp
must be multiplied to arrive at the value of Ucw
Ucw = Urp x Kc
• Atmospheric correction factor (Ka) – the factor to be applied to
Ucw to account for the actual atmospheric conditions (applies
only to external insulation)
• Safety factor (Ks) – the factor to be applied to Ucw to account for
the actual service conditions
• Test conversion factor (Ktc) – the factor to be applied to Urw in a
given over-voltage class, in the case where the standard
withstand shape of the selected withstand test is that of a
different over-voltage class
20
Recap of May 13/15 2014 Course
“Insulation Coordination” by Dr. Peelo
• Conventional (deterministic) BIL or BSL – the insulation
strength expressed in terms of the crest value of a
standard lightning impulse (for BIL) or a standard
switching impulse (for BSL) for which the insulation shall
not exhibit ANY disruptive discharge (generally
applicable to non-self-restorable insulations)
– Applicable to non-self-restoring insulation
• Statistical BIL or BSL – the insulation strength expressed
in terms of the crest value of a standard lightning impulse
(for BIL) or a standard switching impulse (for BSL) for
which the insulation exhibits a 10% probability of failure
(generally applicable to self-restorable insulations)
– Applicable to self-restoring insulation
21
Recap of May 13/15 2014 Course
“Insulation Coordination” by Dr. Peelo
Basic Impulse Level (BIL or
BSL)
The crest voltage of a standard wave
(either a 1.2/50 impulse or a 250/2500
impulse) that will not (or in 90% of the
tests, will not) cause a flashover of the
insulation is referred to as “Basic Impulse
Level or BIL”
1.2/50
The insulation strength of equipment as
tested should be equal or above the BIL
as specified in an AESO’s Functional
Spec
250/2500
22
How the BIL (or BSL) is Determined
BIL or BSL
Test conversion
factor Ktc
Required withstand voltage Urw
Atmospheric factor Ka
Safety factor Ks
Coordination withstand voltage Ucw
Coordination factor Kc
Representative over-voltage Urp
MCOV
(between 5% and 10%)
Nominal voltage (138/144/240/500 kV)
Ground
23
Recap of May 13/15 2014 Course
“Insulation Coordination” by Dr. Peelo
Standard lightning impulse voltage waveform
Very fast front short duration over-voltage
Standard switching impulse voltage waveform
Temporary over-voltage
24
Magnitude of over-voltage pu
Margins of Protection
5
4
3
2
1
0
Fast-front over-voltage
(Lightning, µs)
Slow-front over-voltage
(Switching, µs to ms)
Temporary over-voltage
(seconds to minutes)
Continuous operating
voltage (life time)
25
Recap of May 13/15 2014 Course
“Insulation Coordination” by Dr. Peelo
26
Recap of May 13/15 2014 Course
“Insulation Coordination” by Dr. Peelo
Temporary Over Voltage (TOV)
• An oscillatory phase-to-ground or phase-to-phase over-voltage, at a
given location and of relatively long duration (1s to 10s), is undamped or
only weakly damped
• TOV level establishes the rating of surge arrestors
• The general rule is that surge arresters should not activate at TOV but
will activate when experiencing higher voltages
Major causes of TOV
• Load rejection
• Ground faults
• Resonance phenomena or harmonics
• Line energization/deenergization
Duration of TOV
• Typically 1s to 10s (or minutes in extreme cases)
27
Surges and Transient Over-Voltages
A short-duration highly damped,
oscillatory or non-oscillatory overvoltage, having a duration of a few
milliseconds or less. Transient
over-voltage is normally classified
as one of the following types
• Slow front
• Fast front
• Very fast front
28
Surges and Transient Over-Voltages (contd.)
• Slow front (20 µs to 5 ms)
– Line energization/deenergization
– Faults or load rejection
– Switching of capacitors/reactors
• Fast front (0.1 µs to 20 µs)
– Lightning
– Switching operations
• Very fast front (1 ns to 0.1 µs)
– Switching of disconnects or circuit
breakers (typically with GIS
applications)
29
Class and Shapes of Over-Voltage and Tests
Source: IEC 60071-2
30
Over-Voltages Amplitudes
Power-Frequency Temporary
Over-Voltage
• Generally ≤ 10s
Switching Over-Voltage
• Slow front 30-300 µs
Tail @ 50%: 100-2000µs
SLG faults
<1.5 pu
Ferranti effect
<1.3 pu
Energizing lines
1.5-2 pu
Load rejection
< 1.4 pu
Re-energizing lines
3-3.4 pu
Resonance
> 2 pu
Switching no-load xformr > 2 pu
Energization/re-energ.
< 1.5 pu
Switching reactor
> 2 pu
Stuck breaker pole
< 2 pu
Switching capacitors
1.5-2 pu
Fault interruption
1.5 pu
Lightning Over-Voltage
• Fast front 1-6 µs
> 5 pu
Tail @ 50%: 50 µs
31
Typical Insulation Coordination Studies
Transmission substation insulation coordination study
• Primary purpose is to determine the location of lightning masts, location and rating
of surge arresters, the mitigation techniques such as pre-insertion breakers, pointon-wave breaker control, current-limiting reactors, and to determine appropriate
protection relay settings
• Look at all sources of surge over-voltages: Temporary over-voltage, switching
surge and lightning surge
• Determine the probabilities and protection margins for all transients entering the
substation
Transmission line insulation coordination study
• Primary intention is to determine
– Location of arresters if back flashover is of a concern
– Necessity and location of arresters if the terminal breakers do not have pre-insertion
resistors
Power plant (including WAGF) or user-owned substation IC study
• Typically performed by the owner of the power plant or substations
• Similar to transmission substation insulation coordination study for the substations
• Primary intention is to determine grounding requirement and location of surge
arresters
32
Over-Voltage Protection Devices
Surge
arrester
Pre-Insertion
Resistor
Grounding
Shielding wire
Controlled closing
More insulation
33
Characteristics of SiC and ZnO Arresters
Characteristics
of different
surge arresters
34
Selection of Surge Arresters
• Location
• Maximum continuous operating voltage
• Amplitude and shape of over-voltages
• Nominal discharge current
• Residual voltage at the nominal discharge
current
• Energy absorbing capability (Arrester class)
• Surge impedance and/or capacitance of the
protected equipment
35
Selection of Surge Arresters
Example – Find a suitable lightning arrester for a 240 kV transformer.
For the transformer, MCOV = 264 kV (=240×110%) and BIL = 850 kV (as per AESO FS)
Therefore, the arrester’s voltage rating (Vr) and continuous operating voltage (Vc) is ≥153 kV
(= 264 ÷ 3)
The following arresters can be chosen:
Voltage Rating (kV rms)
Max Residual Voltage (kV peak)
Vr
Vc
TOV
(kV rms)
(10 sec)
210
156
231
417
433
469
494
240
191
264
476
495
536
564
276
221
303
547
569
617
648
SPL (1 kA)
30/60 µs
SPL (2 kA)
30/60 µs
LPL (5 kA)
8/20 µs
LPL (10 kA)
8/20 µs
Insulation strength (BIL) = 850 kV
Therefore, protective margin = (850/564 – 1) = 0.51
or 51% (which is >25%)
Assuming an effectively grounded system, and the power frequency over-voltage is limited
to no more than 40% at the arrester,
so MCOV × 140% = 153 × 140% = 214 kV (which is less than 264 kV)
36
Procedure for Insulation Coordination
•
•
•
•
•
•
•
•
Transient analysis & simulation
Origin and level of over-voltages
Statistical distribution of over-voltages
Protective level of arresters
Insulation characteristics
Determine contamination severity
Verification of data and assumptions
Determine coordination factor Kc
Determination of representative
over-voltage Urp

Kc

Determination of coordination
withstand voltage Ucw
• Determine altitude correction factor Ka
• Determine safety factor Ks
Ka Ks

Determination of required
withstand voltage Urw
• Determine test conversion factor Ktc
• Determine level and range of Uw (for
both internal and external)
Ktc
Rated or standard
insulation level Uw

37
Differences between IEEE and IEC
•
•
•
•
Both IEEE 1313 and IEC 60071 are excellent reference standards
Procedures and methodologies in both standards are same or similar
In many cases IEEE 1313 cites directly IEC 60071 recommendations
The differences are minor and subtle
Nomenclature
Detail
Performance criteria
MCOV
IEEE 1313
IEC 60071
BIL, SIL
LIWV, SIWL, ACWV
Tend to be concise
Detailed with more
examples
Generally more
“aggressive”
Generally more
“conservative”
≥ 15 kV
≥ 1 kV
38
Typical Nominal, Minimum, MCOV and BIL
Values in AESO’s Functional Specification
Nominal
(kV)
Minimum
(kV)
MCOV
(kV)
BIL
(kV)
25
23
28
150
69
62
79
350
138
124
152
650
144
130
155
650
240
216
264
1050
500
475
550
1800
39
Insulation Coordination for Transmission Lines
Transmission Line Insulation Coordination Involves
• Shielding angle of the shielding wire
• Clearance of conductors
• Selection of the type and length of insulators
Keep in Mind
• Shielding Failure Flashover Rate (SFFOR) and Back Flashover Rate (BFR)
are two typical design criteria – typical SFFOR is 0.05 f/100km-yr and BFR
is 1 f/100km-yr
• The higher the tower and voltage, the smaller the shielding angle
• BFR impacts substation insulation requirements
• Contamination influences creepage distance (mm/kV) and consequently
the number of insulator units
• Generally, from an insulation perspective, transmission line reliability
performance is 10% of substation reliability criterion
40
Insulation Coordination for Substations
Substation Insulation Coordination Involves
• Determination of BILs for major equipment or equipment group
• Location of shielding masts and/or shielding wires
• Clearance of conductors
• Surge arresters – Rating, number & locations
Keep in Mind
• MTBF (and BFR) determine if line-entrance arresters are required
• Transformers and cables should always be primary concerns
• Protective margin is generally for non-self-restoring insulation
• Cost of equipment failure generally determines sequence of failure
• Gap configuration can change CFO level by ±30%
• Lightning flash can be multiple strokes – longitudinal insulation
• There may be back-and-forth calculations/adjustments required
41
Protection and Insulation Coordination of
Substation Components
Substation Type
• Air-insulated substation
• Gas-insulated substation
Major Equipment
• Transformers
• Circuit breakers
• CTs and PTs
• Capacitors/Reactors
• Cables
42
Insulation Coordination between T and D
General Principles
• Similar to protection coordination between transmission
and distribution
• Should a surge result in insulation breakdown, it should
generally be on the distribution system first
• Interruptions to consumers are more confined and
localized, i.e., fewer customers impacted per event
• Distribution utilities are generally closer to the failed
equipment – faster response
43
Typical BIL Levels of Distribution Class &
Power Class
Voltage
(rms kV)
Distribution
Class BIL (kV)
Power Class
BIL (kV)
5
60
75
8.7
75
95
15
95
110
25
110
150
34.5
150
200
72
250
350
44
Insulation Coordination between T and G
Keep in Mind
• Rotating machines (incl. generators/motors) do not have BIL
ratings
• For conventional power plants, insulation coordination is primarily
between plant substation and TFO system
Wind Aggregated Generating Facility (WAGF):
• Most wind power plants in Alberta use 34.5 kV collector systems
• Most wind generators (WTGs) are not typically grounded
• Induction WTGs can continue to generate if sufficient capacitance
is present (self excitation) – voltage can be high
• As above, MCOV and TOV can become constraints for arresters
• Most WTGs use distribution class equipment (for economic
reasons) with up to 150 kV BIL
45
Insulation Coordination between
Transmission Lines and Substations
General Principles
• Insulation performance of overhead lines has a large impact on the
insulation performance of substations
– Re-energization operations
– Towers close to substations
• Transmission lines should be designed to enable no injection of
over-voltage in excess of the rated impulse withstand voltage of the
connecting substations into the substations
• In mountain areas, the reduction in Critical Flashover (CFO)
voltage due to higher elevations should be taken into account
• Substation insulation strength should be at least equal to line
insulation strength for switching surges if no line-side arresters
46
Things to Remember in Insulation Coordination
• The TFOs and Market Participants, not the equipment
manufacturers, are responsible for insulation coordination
studies
• There is nothing more important than “knowing your system
better”
• There is not always a “single best solution” to insulation
coordination
• Back-and-forth calculations and adjustments are often
needed in insulation coordination studies
• Deterministic approach should always be applied to nonself-restoring equipment
• Statistical approach can be applied to self-restoring
equipment
• Surge arresters are generally not used to limit temporary
over-voltages (TOVs)
47
Things to Remember in Insulation Coordination
(cont’d)
• Basically, the basic impulse level (BIL) is equal to the
Representative Over-Voltage Urp with many correction factors on top
• Insulation coordination is both an art and science, and is often an
economic decision. Many parameters or requirements are conflicting
in reality.
Example – To reduce BFR of a transmission line
Option: increase conductor spacing and insulator units  larger tower  higher
cost and increased surge impedance  increased BFR
• Power system insulation is an ever-evolving field. More research
needs to be done to more fully understand the transient behavior of
lightning, switching surges, etc.
IEEE 1243 – Guide for Improving the Lightning Performance of Transmission Lines
says
– The methods for estimating the lightning performance of transmission lines show
several approaches to a real‐life engineering problem that is ill‐defined. Precise
constants are rarely known and are often not really constant, input data is difficult
to describe mathematically except in idealized ways
48
THANK YOU
Questions?
Insulation Coordination
in the Alberta Interconnected Electric System
Part 2
Ligong Gan, P.Eng.
Transmission Engineering & Performance
Alberta Electric System Operator (AESO)
APIC Insulation Coordination – Agenda
• AESO’s role in transmission system
insulation coordination
• Evolution of BIL requirements in
Alberta
• Insulation Requirements in AESO’s
Functional Specifications
• Thoughts on Possible Future Changes
to Current BIL Levels
• Q&A
2
The Power Industry of Alberta
Competition
Generation
Retail
Regulated
Transmission
Distribution
AESO
3
Power Industry Structure in Alberta
Minister of Energy
(Appoints AESO Board Members, MSA & AUC Chair)
Electric Utilities Act
Balancing
Pool
Independent
System
Operator
(AESO)
Generators
Alberta Utilities
Commission (AUC)
Transmission
Facility Owners
Market
Surveillance
Administrator
(MSA)
Distribution
Facility Owners
Retailers
4
AESO’s Core Functions
Transmission System Access
System Operations
Provide access for both electricity
generators, large industrial
customers and distribution utilities
Direct the reliable 24/7 operation of
Alberta’s power grid
Market Services
Develop and operate Alberta’s
real-time wholesale energy
market to facilitate fair,
efficient and open competition
Transmission
System Development
Plan the transmission grid to
ensure continued reliability to
facilitate a competitive market and
investments in new supply
5
Alberta’s Bulk Transmission System
240-500 kV (now and near future)
 Virtually all 240 kV lines
 The KEG loop (500 kV)
Dover
Thickwood
 Two 500 kV HVDC lines between
Edmonton area and Calgary area
 Two 500 kV AC lines planned from
Edmonton area to Fort McMurray
area
 One 500 kV AC interconnection to
British Columbia
Wesley
Creek
Livock
Brintnell
Conklin
McMillan
Leismer
Christina
Lake
Heart
Lake
Mitsue
Little
Smoky
Louise
Creek
Marguerite
Lake
Heathfield
Heartland
WhitefishLake
Deerland
Josephburg
Clover Bar
Sagitawah
Wabamun
Sundance
Bickerdike
Sunnybrook
Keephills
Ellerslie
Genesee
Brazeau
Battle
River
Metiskow
Hansman Lake
Red Deer
Benalto
Cordel
Pemukan
 One 240 kV interconnection to
Montana
Sheerness
Anderson
Lanfine
Beddington
Crossing
Sarcee
Janet
E. CalgaryShepard
SS-65
Langdon
Bennett
Empress
Milo
 One 150 MW (HVDC)
interconnection to Saskatchewan
Jenner
SC2
Cassils
Foothills
Stavely
SC1
West
Brooks
Newell
Bowmanton
‘MATL’
Chapel Rock
Filder
Peigan
Windy N. Lethbridge
Flats
Goose Lake
Whitla
Etzikom
Coulee
6
Alberta’s Existing Transmission System
Voltage
Substations
(energized)
TFO
Xmission Lines (km)
(energized)
Customer
TFO
Customer
69/72 kV
70
11
2,246
21
138/144 kV
403
57
12,824
282
240 kV
101
23
10,361
223
500 kV
8
602
Note: Circuit length (km) includes both overhead lines and underground cables
Evolution of Insulation Requirements in
Alberta Transmission System
 First 138 kV line – 80L from Ghost
Substation to Edmonton was built in
1929
 MCOV of the first 138 kV line 80L was
set at 145 kV (105%)
 Today – the following MCOV and BIL
levels are used:
138 kV
144 kV
MCOV
152
155
BIL (1)
550
550
BIL (2)
650
650
8
Evolution of Insulation Requirements in
Alberta Transmission System
 First 230 kV line, between Wabamun
and Sarcee 42S was built in 1961
 MCOV of the first 230 kV line was set
at 242 kV
 Wabamun had to operate at 253 kV
in order to maintain acceptable
voltage at Sarcee
 Because of the circuit length (>450
km), special equipment with MCOV of
264 kV was installed at Wabamun
 The system was then classified as
“240 kV nominal voltage”
 BIL levels of 900 kV and 1050 kV
were chosen, assuming a grounding
factor of 1.4
9
Evolution of Insulation Requirements in
Alberta Transmission System
 In 1986, first 500 kV tie-line 1201L,
between Langdon and Cranbrook (B.C.),
was built
Thickwood
Dover
 In 1982, first intra-Alberta 500 kV line
1202L, between Keephills and Ellerslie,
was built but operated at 240 kV
Brintnel
l
Livock
Heart
Lake
Heathfield
Heartland
 In 2010, 1202L re-energized at 500 kV
Clover Bar
Sundance
Wabamun
Sunnybroo
k
Keephills
 MCOV of 1201L/1202L was set at 550 kV
Ellerslie
Genesee
Hansman
Lake
 BIL of 1425/1550/1800 kV chosen for
substations 89S/320P/102S
Pemukan
Lanfine
Crossing
Thermal Plant
Hydro Plant
 Since around 2011, 1550/1800 kV
became BIL levels for 500 kV system
WhitefishLake
Shepard
SS- 65
Existing 240 kV
Existing 500 kV
Future 240 kV
Future 500 kV
Future 500 kV HVDC
Bennett
SC2
Cassils
Foothill
s
Stavely
SC1
Newell
‘MATL
’
AIES
Transmission System
500 /240 kV System Overview
Chapel
Rock
Filder
Windy
Flats
Bowmanto
n
Whitla
Etzikom
Coulee
10
AESO’s Role in Transmission Insulation
Coordination
In general, AESO only defines functionality requirements
of transmission elements in its Functional Spec





Operating conditions of equipment
Input and desired output (for RASs etc.)
Provides a direction (or guidance) for design
Reference for equipment bidding and procurement
Requirements (or guidance) for compliance with standards
A Functional Specification does not




Define inner workings
Specify the manufacturer to be used or avoided
Dictate how equipment is procured
Provide details of how equipment is installed
11
AESO’s Role in Transmission Insulation
Coordination (cont’d)
Typically, AESO’s Functional Spec contains
 Purpose
 Interpretation and Variances
 Project Overview
 Scope of work

Standards

Scope of work for TFO and Market Participant
 Transmission System Operating Characteristics

Normal operating levels and constraints

Emergency operating requirement
 Appendices

Single line diagrams for substation configuration and SCADA
requirements
12
Some Relevant Rules & Standards
• ISO rule 502.1 – Wind Aggregated Generating Facilities Technical
Requirements
Section 21 provides lightning surge protection requirements for the collector
stations, and between collector substation and transmission line
• ISO rule 502.2 – Bulk Transmission Line Technical Requirements
Specifies the standards to be used in setting electrical clearances, the conditions
under which an insulation study is required, and the minimum insulation levels of a
bulk transmission line
The Information Document (ID) further provides detailed explanation as to how
insulation coordination is conducted, and the recommended BIL levels
• Generation & Load Interconnection Standard 2006
Section 2.3 sets out the general requirements for insulation studies and the
specific IEEE standard (P998) to be employed
• ARS FAC-001-AB – Facility Connection Requirements
Section R2.6 requires that the AESO’s interconnection requirement or project’s
Functional Spec must address insulation and insulation coordination
13
AESO’s Philosophy on Insulation Coordination
• AESO specifies rules & standards which set out
minimum technical requirements
• AESO provides minimum BIL levels without
distinguishing
– between BIL & BSL
– between conventional & statistical
• TFOs and market participants are required to
perform any and all insulation coordination
studies and determine appropriate insulation
levels
• TFOs and market participants are required to
coordinate with each other in setting equipment
insulation levels
14
AESO Rule 502.2 – Transmission Lines
• Section 14(2) – Shield wires must be installed on
138/240/500 kV AC or ±500 kV DC bulk transmission
lines
• Section 14(3) – Number and positioning of the shield
wires must be so as to produce lightning flashover rates
that are consistent with all reliability requirements of the
lines
• Section 17(5) – Electrical clearances for use with the
wind pressure values of Table 3 must be determined
from the application of the methodology outlined in IEEE
Standard 1313.2 “The Application of Insulation
Coordination”, for transmission line phase to ground
switching over voltages
15
AESO Rule 502.2 – Transmission Lines
• Section 21(7) – The minimum insulation levels for a bulk
transmission line and any 25 kV distribution line located on bulk
transmission line structures must be as set out in the following
table:
Nominal Voltage (kV)
Critical Impulse Flashover CIFO (kV)
25 kV
165
138/144 kV
715
240 kV
1,155
• ID 2010-005R, Section 21 – Insulation levels for 500 kV AC or
±500 kV DC lines are determined from insulation studies carried
out for each such line, as part of the design process.
16
AESO Rule 502.2 – Transmission Lines
• ID 2010-005R, Section 21 – 25 kV insulation requirement
applies only to those 25 kV distribution lines placed on bulk
transmission line structures. 502.2 recognizes the need for
insulation coordination between circuits of different voltages
located on common structures
• ID 2010-005R, Section 21 – Insulation levels for 500 kV AC
or ±500 kV HVDC lines are determined from insulation
studies carried out for each such line, as part of the design
process. Hence, 502.2 does not include insulation levels for
500 kV class lines
17
AESO Functional Specification
In the “Project Scope” section:
• (the legal owner of the transmission facility) shall
complete insulation coordination studies and coordinate
with the market participant as required to establish
appropriate insulation levels
• Undertake insulation, grounding, protection and
communication studies as necessary to accommodate the
proposed system additions and modifications
18
AESO Functional Specification
6.3 Insulation Levels
(1) The following provides the minimum required basic impulse levels for the
transmission system. Station equipment with lower insulation levels may be used
provided that protection and coordination can be maintained with judicious insulation
design and use of appropriate surge arresting equipment.
(2) For 25 kV circuit breakers where there is a grounded wye transformer and surge
arrestors are installed, a basic impulse level of 125 kV is acceptable.
Nominal Voltage (kV rms)
25
69/72
138/144
240
500
Station post insulators and airbreaks
150
350
550
900
1,550
Circuit breakers
150
350
650
1,050
1,800
Current and potential transformers
150
350
650
1,050
1,800
Transformer windings (with arresters)
150
350
550
850
1,550
19
Thoughts on Possible Future Changes to
Current BIL Levels
• Should we split the current basic insulation levels into BIL
and BSL levels?
• In some 500 kV projects, it has been suggested that the BIL
level for the 500/240 kV autotransformers be set at 1425 kV
for lower cost and easier transportation
• Should we create a new nominal voltage level of 260 kV
with MCOV of 286 kV (or 275 kV)?
• Should we raise the current BIL for 240/260 kV
transformers from 850 kV to 900 kV (or higher)?
• Should we differentiate GIS from AIS equipment, especially
for 500 kV equipment, on the BIL levels?
• Any other from you?
20
Upcoming AESO Rule for Substations –
502.11
• The AESO is now in the process of developing
a Substation Rule (502.11) which sets out the
minimum technical requirements respecting
design, engineering and construction of (new)
transmission substations
• Insulation coordination and grounding will be a
major part of Rule 502.11
• Proposed Process (2015-2016)
– Industry Workgroup (WG)
– Recommendation paper to WG & stakeholders
– Draft and post Rule for comments from industry
– Filing of Rule 502.11 with AUC
21
THANK YOU
Questions?
Over-Voltages and the
Distribution System
Thomas C. Hartman, P.Eng.
APIC – Professional Development
May 12 & 14, 2015
University of Alberta
Discussion Outline - OVERVIEW
• The Origin and Shapes of Distribution System Surges
• Insulation Systems – And How They Go Bad
• Where Surges Matter – And What They Do
–
–
Overhead Systems
Underground Systems
• Distribution Surge Arresters – Design and Application
• Reality Check
• Q&A
NOTE: References are in parenthesis - (xx)
1
University of Alberta
Disclaimer
I will mention many companies during this presentation.
Please keep in mind:
1 – I have NO financial interest or otherwise in any of the
companies I mention
2 – I work for ATCO Electric Distribution and that is my only
source of income
3 – This presentation is my opinion only and does not
necessarily reflect ATCO policy, practices, or standards
4 – I expect that you will use this presentation for illustrative
purposes only. Any arrester applications you design shall
be based on your own professional judgement
2
University of Alberta
The Origin and Shapes of
Distribution System Surges
• Overhead
(16)
(1)
(2)
• Underground – Mostly same as O/H,
(12)
but with some twists!
3
University of Alberta
What is a Surge?
Surge
• IEEE Std 100: “A transient wave of current, potential, or
power in an electric circuit. Note: The use of this term to
describe a momentary overvoltage consisting in a mere
increase of the mains voltage for several cycles is
deprecated. See also: swell.”
Temporary Overvoltage (TOV)
• IEEE Std 100: “. An oscillatory overvoltage, associated
with switching or faults … and/or nonlinearities … of
relatively long duration, which is undamped or slightly
damped.”
4
University of Alberta
TOV
It is NOT a Surge!
•
•
•
•
Accidental Grounding - Leg of Delta
Loss of Neutral
Fault Conditions
Comingling
“When Overbuild Meets Underbuild”
Surge arresters provide a simple solution to a complex overvoltage
problem
Daniel J. Ward, Dominion Virginia Power
T&D World Magazine - Mar 1, 2011
5
University of Alberta
World Ground Flash Density
www.arresterworks.com/resources/calculator_images/GFD_World.jpg
6
University of Alberta
A Natural Cause - Lightning
(13)
(14)
(3)
(15)
Lightning Current MIL-STD-464
7
University of Alberta
Vacuum Switch TRV Behavior (7)
Simulated TRV Response
Source Voltage: 3.4 kV (6 kV System)
Current at Opening: 4.7 A
8
University of Alberta
Shunt Capacitors
Effect of switching re-strikes on capacitor voltage
(6)
(5)
9
University of Alberta
Current Limiting Fuse Operation
(11)
10
University of Alberta
Current Limiting Fuse Arc Interruption Voltage
(34)
11
University of Alberta
Other Surge Waveforms
(37)
Switching Surge
(36)
(38)
12
University of Alberta
Surges and Their Waveforms
Just So YOU Know…
Lead Length can ADD up to 1500 Volts/Foot
Lead length is the physical wire distance between the
Apparatus and the Line Side of the Surge Arrester
PLUS (+)
The Line Length from the Ground of the Surge
Arrester to the Ground of Apparatus
AND for the Love of Goodness,
Please Don’t COIL the Leads!!!
13
University of Alberta
Insulation Systems
And How They Go Bad
If we lived in a perfect world, our insulation systems
would last forever. But…
We don’t.
All Insulation Systems are Doomed from the Start!
• Embedded Manufacturing Defects
• Environmental Contamination
• Shipping and Handling
• “Some” Field Assembly Required
(32)
14
University of Alberta
Insulation Systems– How Do They Fail?
External Sources
• Physical Damage – “Rocks and Rifles”, External Arc
• Contamination – Farming, Exhaust, Salt, etc.
Internal Sources
• Water Ingress
• Arcing under Oil or SF6
• “Built-In” Defects – Either from Vendor or Customer
15
University of Alberta
Insulation Systems
Contamination and Built-In Defects
Contamination – Surge Arresters Really Won’t Help
• The Failure Mechanisms Associated with
Contamination are Active at 60 Hz System Voltage
“Built-In” Defects – Surge Arresters May Help
• If the Failure Mechanism is Triggered by a Surge,
then a Surge Arrester will Delay the Trouble
• If the “Built-In’ Defect is Active at System Voltage,
then a Surge Arrester Won’t Help.
16
University of Alberta
Insulation Systems – Failure Triggers
Contamination
• Dry Band Arcing is the Beginning of the End
“Built-In” Defects
• It is All About Capacitance, Dielectric
Constants, and Dielectric Strength
• C = (k*e0*A)/d
where k: Air =1, Silicone = 4, EPDM = 2.6
Glass = 6, Polyethylene = 2.25, Porcelain = 6
Which Equals an Evil Voltage Divider
17
University of Alberta
Ceramic / Glass
• One Tough Insulation System!
• Can Last a Century or More
• Surges / Flashovers are Generally Benign
Failure Mechanisms
• Slow Clearing Times Crack Ceramic/Glass
• Susceptible to Point Pressures Resulting in Crack
Propagation
• Pin Threads (lead/nylon)
• Ice Expansion Forms Cracks
• External Contamination / Cleaning
18
University of Alberta
Polymers
Organic/Semi-Organic System
• Manufacturing Process
Sensitive
(31)
Failure Mechanisms
• Embedded
Manufacturing/Material Defect
• If Small Enough, the Defect
Lays Dormant Longer
• Surges Reduce PD Inception
Levels
• Ultimate Demise of Insulator
(30)
19
University of Alberta
Dielectric Fluid – Oil
(29)
1. Oxidation: Oxidation is the most common cause of oil deterioration, which is the reason
that transformer manufacturers are careful to seal the transformer from the atmosphere.
2. Contamination: Moisture is the main contaminant. Its presence can react with the oil in the
presence of heat. It also lowers the dielectric properties of the insulating oil.
3. Excessively high temperature: Excessively high heat will cause decomposition of the oil
and will increase the rate of oxidation. The best way to avoid excessive heat is to avoid
overloading the transformer.
4. Corona discharges: Arcing and localized overheating can also break down the oil,
producing gases and water, which can lead to the formation of acids and sludge.
5. Static electricity: The existence of an insulating fluid flowing past an insulating solid
(paper), results in charge separation at the interface of the two materials. Physically, these
charges separate at the interface of the oil and paper in any transformer; thus reducing the
dielectric strength of the insulating oil. This could also cause internal flashover.
6. Furans: Furan derivatives are a measure of degradation of paper insulation. When the
paper ages, the long-chain cellulose molecules (polymers) break down in smaller fractions
and its physical strength is reduced. The degree of polymerization can be directly related to
the concentration of furan derivatives, which are formed in the oil.
20
University of Alberta
SF6
(28)
Sulfur hexafluoride (SF6) is a relatively nontoxic gas used in a number of applications for its
inert qualities. The dielectric and other physical and chemical properties related to its lack
of reactivity have led to the extensive use of SF6 as an insulating medium in switching
equipment (e.g., circuit breakers) by electric utilities. While SF6 is inert during normal use,
when electrical discharges occur within SF6-filled equipment, toxic byproducts can be
produced that pose a threat to health of workers who come into contact with them.
SF6 can decompose into byproducts when exposed to four types of electric discharges
(CIGRE1 1997)
• partial corona discharges caused by insulation defects;
• spark discharges that occur at insulation defects or during switching operations;
• switching arcs that occur in load break switches and power circuit breakers; and
• failure arcs that occur due to insulation breakdown or switchgear interruption failure.
Each discharge can result in different mixtures and concentrations of byproducts.
21
University of Alberta
Where Surges Matter ~ OVERHEAD SYSTEMS
And What They Do There
Pin Insulator
Transformer
Regulator
Capacitor
Riser Pole
On the Secondary
22
University of Alberta
At the Pin Insulator
(16)
23
University of Alberta
At the Transformer
(9)
(24)
24
University of Alberta
At the Secondary
Transformer Secondary Protection
Surge Suppression Inc.
At the secondary bushing – Inside
(9)
EATON’s Cooper Power Systems
25
University of Alberta
At the Capacitor (17)
(18)
(17)
26
University of Alberta
At the Regulator
(19)
(35)
27
University of Alberta
Where Surges Matter ~ UNDERGROUND
And What They Do There
Underground Systems
• Riser Pole
• Cable
• At an “Open Point”
28
University of Alberta
At the Riser Pole
(20)
(22)
(21)
29
University of Alberta
In the Cable
(25)
(27)
(26)
(26)
30
University of Alberta
At an “Open Point”
(4)
(10)
31
University of Alberta
At ANY Place on your System
Just So YOU Know…
Lead Length can ADD up to 1500 Volts/Foot
Lead length is the physical wire distance between the
Apparatus and the Line Side of the Surge Arrester
PLUS (+)
The Line Length from the Ground of the Surge
Arrester to the Ground of Apparatus
AND for the Love of Goodness,
Please Don’t COIL the Leads!!!
32
University of Alberta
Distribution Surge Arresters
Design and Application
•
•
•
•
A Very Brief History of Surge Arrester Evolution
Explanation of Surge Arrester “Classes”
Which Class to Use
How Arresters Eventually Fail
• Surge Arresters have ONE Job – Protect Insulation
33
University of Alberta
A Brief History
• Air Gap – Beginning of Time to Now
• Silicon Carbide (SiC) – 1930 to Mid 1980s
• Metal Oxide Varistors (MOV) – 1975+
(41)
http://www.arresterworks.com/
http://www.arresterworks.com/
34
University of Alberta
Differences Between Manufacturers
• None Really
• Arresters are essentially COMMODITIES
• Purchase on your preferences such as:
• Price
• Vendor Service
• Availabilities
• Vendor Preference
• Etc.
• You will likely be satisfied!
• My Preference???
35
University of Alberta
Surge Arresters – Parameters
Critical Parameters (Minimum Needed)
1. MCOV – Maximum Continuous Operating Voltage
2. TOV – Temporary Over-Voltage Withstand
3. EFOW – Equivalent Front-of-Wave (0.5 uS, Lightning)
Lesser Parameters (May be hard to Coordinate)
4. Discharge Voltage – At: 1.5 kA, 5 kA, 10kA, & 20 kA
5. Switching Surge – 250 or 500 amps (Class Dependent)
6. Arrester Class – ND, HD, RP, Intermediate, Station
Only 6?!, Really?!
But What is a Surge Arrester RATING?!
36
University of Alberta
Critical Parameter #1 – MCOV
Nominal System
L-L Voltage
Maximum
L-L Voltage
Maximum
Line to GND
Voltage
kV rms
4.16
4.8
6.9
24.9
kV rms
4.37
5.04
7.25
26.2
kV rms
2.25
2.91
4.19
15.1
Solid MultiUni-Grounded
Grounded
Systems
Systems
(3-Wire)
(4-Wire)
MCOV
2.55
--15.3
MCOV
5.1
--22
Impedance
Grounded,
Ungrounded,
and Delta
Systems
MCOV
5.1
5.1
7.65
--
Do You See a RATING Here?
37
University of Alberta
Critical Parameter #2 – TOV
38
(41)
University of Alberta
Critical Parameter #3 – EFOW (BIL)
(39)
39
University of Alberta
Lesser Parameters 4 & 5
4. Discharge Voltage – At: 1.5 kA, 5 kA, 10kA, & 20 kA
5. Switching Surge – 250 or 500 amps (Class Dependent)
These two parameters will one used based on the type
of equipment you are protecting.
The Discharge Voltage is use at the “End” of Lightning
Protective Levels.
40
University of Alberta
Capacitors – Coordinate to Surge Arrester
Schneider Electric – Hong Kong
General Specification for Fixed Capacitor Bank for Electrical Network up to 36kV
According to network rated voltage, the insulation level of equipment is as follows :
(40)
Power Frequency Voltage
Withstand
(kV rms)
Impulse Voltage Withstand
(kV peak)
7,2
20
60
11000
12
28
75
15000
17,5
38
95
22000
24
50
125
33000
36
70
170
Rated Voltage (Vdim)
Insulation Level
(V)
(kV)
6600
41
University of Alberta
Insulators – Coordinate to Surge Arrester
PPC Pin Type Insulators
Catalog Number
Frequency
253-S
261-S
263-S
366-S
380-S
386-ST
ANSI Class
55-2
55-3
n/a
55-4
55-5
55-6
Neck Type
C
C
C
F
F
J
Typical Application (kV)
60 Hz
7.2
11.5
11.5
13.2
14.4
23
Dry Flashover Voltage (kV)
60 Hz
45
55
55
65
80
100
Wet Flashover Voltage (kV)
60 Hz
25
30
30
35
45
50
Puncture Voltage (kV)
60 Hz
70
90
90
95
115
135
Impulse Flashover Positive (kV)
Impulse
70
90
90
105
130
150
Impulse Flashover Negative (kV)
Impulse
85
110
110
130
150
170
Leakage Distance
5"
7"
7"
9"
12"
15"
Dry Arcing Distance
3 3/8"
4 1/2"
4 1/2"
5"
6 1/4"
8"
Cantilever Strength (lbs)
2500
2500
2500
3000
3000
3000
Minimum Pin Height
4"
5"
5"
5"
6"
7 1/2"
Net Weight per 100 (lbs)
183
225
260
390
500
890
Package Weight per 100 (lbs)
191
254
288
400
617
938
Standard Package Quantity
48
24
24
12
12
8
42
University of Alberta
Arrester Class - Parameter #6
•
•
•
•
•
Normal Duty (ND)
Heavy Duty (HD)
Riser Pole (RP) (Not a Real Class)
Intermediate Class
Station Class
Arrester Class size is Mostly Determined by the
Diameter of the MOV Disk
ND = 1”, HD = 2”, RP = 2”, Inter. = 3”, Station = 4”+
43
University of Alberta
Class Comparisons
0.5 μsec
10kA
MCOV
kV
EFOW
Normal Duty PDV65-Optima
18
15.3
62.8
46.4
Heavy Duty PDV100-Optima
18
15.3
60.6
Riser Pole
PVR-Optima
18
15.3
Intermediate
PVI-LP
18
Station
EVP
18
Hubbell
Product
8/20 Test Waveform
Maximum Discharge Voltage - kV
500 A
Rated
Voltage
kV
Switching
1.5 kA
Surge
10 kA 20 kA
Tempoary
Over-Voltage
1 sec 10 sec
40 kA
kV rms kV rms
3 kA
5 kA
50.1
53.8
57
63.3
72.6
91.2
22.7
21.7
43.5
45.4
48.4
51.3
56.4
63.5
75.5
23.5
22.2
53.4
35.5
38.9
41.9
44.3
48.9
56.1
66.2
22.2
21.0
15.3
51.6
38.3
40.9
43.2
45.2
48.8
54
60.9
21.4
20.5
15.3
51.6
36.1
38.5
40.4
42.4
45.5
49.1
56.1
21.7
20.8
44
University of Alberta
Protection Level
Protective Margin = ((Insulation Level / Arrester Discharge Voltage) – 1) * 100%
(33)
45
University of Alberta
Generic MOV I-V Curve
46
University of Alberta
(42)
47
University of Alberta
Which Arrester Class – What Purpose?
• Your Choice… In Alberta, a low lightning region Normal Duty is good enough for general purpose
protection
• Riser Poles – How important is the circuit?
• Capacitors
– Normal Duty is OK,
– Big Banks consider Heavy Duty or Intermediate
• Transformers
– Normal Duty is OK
– Big Expensive Transformers… Heavy Duty or Intermediate
48
University of Alberta
Surge Arresters – How Do They Fail?
• TOV is the Number 1 Killer of Surge Arresters in
Alberta (As reported on Global National, just kidding…)
– The Process is Simple: Overvoltage Physically Heats the
MOV disk, Heat Lowers the MCOV Which Increases the
Heat Generated, Which Lowers the MCOV More, Which
Increases th Heat Generated, until BOOM!
• Today’s Surge Arresters Rarely Fail Due to a Surge
in Alberta. The Quality is Really That Good!
49
University of Alberta
Surge Arresters – Disconnector
(41)
50
University of Alberta
~ Reality Check ~
Should You Be Worried about a Surge Armageddon?
(23)
51
University of Alberta
~ Reality Check ~
No, of course not.
Your own historical data is proof!
But, Asset Life would be Extended Significantly with
the Proper Application of Surge Arresters!
52
University of Alberta
Where to Focus Your Protection
•
•
•
•
•
•
•
Transformer Primaries – SHORTEST Lead Length!!!
Riser Poles – SHORTEST Lead Length!!!
UG Open Points
Regulators – Primary & By-Pass
Reclosers – Line AND Load Sides
Capacitors
O/H Dead Ends and N/O Switches
53
University of Alberta
Careful There, Electrical Current!
One Last Thing…
Be Careful Where You Place an Arrester
• Fuses – Surge Current Will Hurt a Fuse
• Capacitors, Regulators, Reclosers, etc
There is NO line or load on these devices,
at least as surge currents are concerned.
54
University of Alberta
Where to Focus your Protection
Just So YOU Know…
Lead Length can ADD up to 1500 Volts/Foot
Lead length is the physical wire distance between the
Apparatus and the Line Side of the Surge Arrester
PLUS (+)
The Line Length from the Ground of the Surge
Arrester to the Ground of Apparatus
AND for the Love of Goodness,
Please Don’t COIL the Leads!!!
55
University of Alberta
A Shameless Promotion
arresterworks.com
Jonathan Woodworth
Deborah Limburg
Principal Engineer
Web and Business Developer
Jonathan started his career at Fermi National Accelerator Laboratory in
Batavia, Illinois, where he was an integral member of the high energy
particle physics team in search of the elusive quark. Returning to his home
state of NY, he joined the design engineering team at McGraw Edison
(later Cooper Power Systems) in Olean. During his tenure at Cooper he
was involved in the design, development and manufacturing of arresters.
He served as Engineering Manager as well as Arrester Marketing Manager
during that time. Since 2008 he has been the Principal Engineer for
ArresterWorks.
Deborah is a long term veteran in the arrester industry having worked for
Cooper Industries for over 25 years. During that time she held a number of
positions in the product engineering department, including leader of the
Engineering Design Services group. One of her major accomplishments at
Cooper was the design and implementation of a virtual product drawing
systems for all major product lines. This lead to a considerable reduction in
the number of Designers and CAD operators required to maintain the
product documentation system. This database system also helped to
improve the overall documentation process due to the reduction in human
errors.
Though his entire career, Jonathan has been active in the IEEE and IEC
standard associations. He is past chair of the IEEE SPD Committee, he is
past chair of NEMA 8LA Arrester Committee, and presently co-chair of IEC
TC37 MT4. He is inventor/co-inventor on five US patents. Jonathan
received his Bachelor's degree in Electronic Engineering from The Ohio
Institute of Technology and his MBA from St. Bonaventure University.
Additionally she developed the software to handle disk selection process for
the tightly matched disk columns required for series capacitor banks and
the management of the varistor assembly process. Deborah received her
BS in Computer Software from the University of New York State and is a
co-inventor on several US patents.
Contact at 716-307-2431
Since 2010 Deborah has been the Web and Business Developer for
Arresterworks.
or Jonathan.Woodworth@ArresterWorks.com
Contact at 716-378-1419 or Deborah.Limburg@ArresterWorks.com
56
University of Alberta
Over-Voltages and the Distribution System
QUESTIONS?
57
University of Alberta
References
1 – http://www.picturesof.net/pages/090326-134616-923048.html
2 – www.wordy.photos/index.php?keyword=11%20kv%20fuse%20explodes&photo=0XVPcDxoV2g&category=people&title=electric+power+line+explosion
3 – http://www.satcomlimited.com/transparent_over_voltages.html
4 – http://www.hubbellpowersystems.com/cable-accessories/elbow-arresters/description/
5 – http://www.sandc.com/edocs_pdfs/edoc_024494.pdf
6 – “SURGE ARRESTER APPLICATION OF MV-CAPACITOR BANKS TO MITIGATE PROBLEMS OF SWITCHING RESTRIKES”
Lutz GEBHARDT - ABB – Switzerland, lutz.gebhardt@ch.abb.com & Bernhard RICHTER - ABB – Switzerland, bernhard.richter@ch.abb.com
7 – “COMPUTATION OF FAST TRANSIENT VOLTAGE DISTRIBUTION IN TRANSFORMER WINDINGS CAUSED BY VACUUM CIRCUIT
BREAKER SWITCHING”
Casimiro Álvarez-Mariño and Xosé M. López-Fernández, Dept. of Electrical Engineering, Universidade de Vigo, EEI,
Vigo, Spain, xmlopez@uvigo.es
8 – http://new.abb.com/products/transformers/distribution
9 – http://commons.wikimedia.org/wiki/File:37.5kVA_three_phase_utility_stepdown.jpg
10 – http://uqu.edu.sa/files2/tiny_mce/plugins/filemanager/files/4310333/traveling_wave.pdf
11 – http://revistas.unal.edu.co/index.php/ingeinv/rt/printerFriendly/25218/33722
12 – http://io9.com/photos-from-the-days-when-thousands-of-cables-crowded-t-1629961917
13 – http://www.edn.com/Home/PrintView?contentItemId=4426566
14 –http://www.ecnmag.com/articles/2011/07/advanced-tvs-construction-improves-lightning-protection
15 – http://www.nautel.com/support/technical-resources/tips-n-tricks/04-09-2012/
16 – http:// www.slideshare.net
17 – https://library.e.abb.com/public/a8c42d637aa10aa2c12577ee0055faad/ABB_DPDQPole_Qpole_revB_EN.pdf
18 – http://www.cooperindustries.com/content/dam/public/powersystems/resources/library/230_PowerCapacitors/23012.pdf
19 – http://www.cooperindustries.com/content/dam/public/powersystems/resources/library/225_VoltageRegulators/MN225008EN.pdf
20 – https://www.osha.gov/SLTC/etools/electric_power/illustrated_glossary/substation_equipment/potheads.html
21 – http://ecmweb.com/archive/applying-pole-mounted-overvoltage-protection
22 – http://www.cpuc.ca.gov/gos/Resmajor/SU6/GO95/SU6_GO95_rule_54_6-F.html
Continued on Next Page
58
University of Alberta
References - continued
23 – http://creepypasta.wikia.com/wiki/File:5178_apocalyptic_destruction.jpg
24 – http://en.wikipedia.org/wiki/Distribution_transformer
25 – http://www.icccable.com/company_product.html?cid=208
26 – http://www.powertechlabs.com/areas-of-focus/power-labs/cable-technologies/condition-assessment-the-whole-picture/
27 – http://www.ee.washington.edu/research/seal/projects/seal_robot/sensors.html
28 – http://www.epa.gov/electricpower-sf6/documents/sf6_byproducts.pdf
29 – http://cdn2.hubspot.net/hub/272197/file-251812186-pdf/white_papers/afi-wp-transoil1.pdf
30 – http://reliabilityweb.com/index.php/print/defects_in_nonceramic_insulators_can_they_be_detected_in_a_timely_manner1
31 – http://www.inmr.com/thermal-inspection-program-finds-failing-dead-end-polymeric-insulators-2/5/
32 – http://en.wikipedia.org/wiki/Fallout_shelter
33 – http://classicconnectors.com/wp-content/uploads/2012/07/Illustration.jpg
34 – “Electrical Distribution System Protection”, 3rd Edition, Cooper Power Systems, 1990
35 – http://www.cooperindustries.com/content/public/en/power_systems/products/voltage_regulators/32-step_single-phase.html
36 – https://fisitech.wordpress.com/2010/10/22/practical-issues-switching-surgeac-transcient/
37 – http://nepsi.com/services/power-systems-studies/
38 – http://file.scirp.org/Html/3-9800140_1113.htm
39 – http://electrical-engineering-portal.com/definition-basic-insulation-level-bil
40 – http://www.schneider-electric.com/download/hk/en/details/18865768-General-Specification-for-Fixed-Capacitor-Bank-for-Electrical-Network-up-to36kV/?reference=Fixed_capacitor_bank_36kV_specENv2
41 – http://www.hubbellpowersystems.com/catalogs/arresters/31_optima.pdf
42 – http://www.coe.montana.edu/ee/seniordesign/archive/SP13/150mwwindfarm/Data_Content/InsulationCoordination.pdf
43 - http://electrons.wikidot.com/semiconducting-ceramics:varistor-applications
59
University of Alberta