Transcript Training - PowerWorld

1
How the Power Grid Behaves
Tom Overbye
Department of Electrical and Computer Engineering
University of Illinois at Urbana-Champaign
2
Presentation Overview
• Goal is to demonstrate operation of large scale
•
•
•
power grid.
Emphasis on the impact of the transmission syste.
Introduce basic power flow concepts through
small system examples.
Finish with simulation of Eastern U.S. System.
3
PowerWorld Simulator
• PowerWorld Simulator is an interactive, Windows
•
based simulation program, originally designed at
University of Illinois for teaching basics of power
system operations to non-power engineers.
PowerWorld Simulator can now study systems of
just about any size.
4
Eastern Interconnect Operating Areas
CORNWALL
NSP
NEPOOL
WPS
NYPP
ONT HYDR
DPC
SMP
MGE
DECO
WEP
WPL
CONS
IPW
PENELEC
PP&L
MEC
TE
NI
PSE&G
OE
CEI
NPPD
PJM500
DLCO
CILCO
MPW
NIPS
JCP&L
OPPD
PECO
AEP
LES
METED
IP
IESC
AE
CWLP
DPL
BG&E
IPL
Ovals
represent
operating
areas
AP
CIN
CIPS
STJO
MIDW
MIPU
DPL
PEPCO
HE
KACY
IMPA
OVEC
VP
KACP
WERE
SIGE
EMO
BREC
SIPC
INDN
EKPC
KU
LGE
EEI
ASEC
YADKIN
DOE
CPLW
EMDE
OMPA
GRRD
SPRM
CPLE
DUKE
WEFA
KAMO
SWPA
HARTWELL
SEPA-JST
OKGE
PSOK
SCE&G
SCPSA
SOUTHERN
ENTR
SEPA-RBR
AEC
SWEP
EQ-ERCOT
JEA
LAFA
SMEPA
TAL
CELE
SEC
Arrows
indicate
power flow
in MW
between
areas
5
Zoomed View of Midwest
WEP
WPL
CONS
TE
NI
CE I
CILCO
NIPS
IP
CWLP
DPL
IPL
CIN
CIPS
HE
IMPA
SIGE
EMO
SIPC
OVEC
BREC
6
Power System Basics
• All power systems have three major components:
•
•
•
Generation, Load and Transmission.
Generation: Creates electric power.
Load: Consumes electric power.
Transmission: Transmits electric power from
generation to load.
7
One-line Diagram
• Most power systems are balanced three phase
•
•
•
systems.
A balanced three phase system can be modeled as
a single (or one) line.
One-lines show the major power system
components, such as generators, loads,
transmission lines.
Components join together at a bus.
8
Eastern North American High Voltage
Transmission Grid
HAWTHORN
MASS 765
-210 MVR
BRUJB561
ESSA
BRUJB569
BRUJB562
CLAIRVIL
INDEPNDC
9MI PT1
JA PITZP
OSWEGO
MILTON
TRAFALH2
TRAFALH1
SCRIBA
VOLNEY
-202 MVR
MARCY T1
EDIC
CLAY
BECK B NIAG 345
BECK A
MIDD8086
KINTI345
676
50676
MW
MVR
50 MVR
MW
DEWITT 3
ELBRIDGE
PANNELL3
ROCH 345
146 MVR
LAFAYTTE
REYNLD3
ALPS345
N.SCOT99
250
0
45 MW
MVR
0 MW
MVR
145 MVR
STOLE345
GILB 345
250 MW
0 MW
45 MVR
0 MVR
NANTICOK
LONGWOOD
286 MVR
LEEDS 3
FRASR345
294 MVR
OAKDL345
HURLEY 3
WATERC345
PLTVLLEY
294 MVR
COOPC345
ROSETON
FISHKILL
348 MVR
MW
0 MVR
MW
262
0
ROCK TAV
143 MVR
RAMAPO 5
SUSQHANA
SUNBURY
WESCOVLE
ALBURTIS
HOSENSAK
KEYSTONE
ELROY
JUNIATA
LIMERICK
CONEM-GH
3 MILE I
01YUKON
250 MVR
1093
MW
HUNTERTN
PEACHBTM
KEENEY
1094MVR
MW
250
CNASTONE
BRIGHTON
W CHAPEL
8MT STM
08MDWBRK
8LOUDON
8CLIFTON
8OX
8POSSUM
8MORRSVL
BURCHES
CHALK500
CLVT CLF
273
829
828
293
MVR
MW
MW
MVR
07MEROM5
8VALLEY
8DOOMS
300
9300
MVR
MW
300
99
MVR
MW
MVR
MW
8BATH CO
300
9300
MW
MVR
9320
MW
MVR
9 MVR
MW
-114MW
893
MVR
8LDYSMTH
8NO ANNA
897 MW
-110
MVR
8ELMONT
8LEXNGTN
8MDLTHAN
8CHCKAHM
801 MW
-127
MVR
8SURRY
8CARSON
8ANTIOCH
8SHAWNEE
8MARSHAL
8PERSON 8MAYO 1
05NAGEL
8PHIPP B
8SULLIVA
0 MVR
8MONTGOM
8PARKWOD
8ROANE
8JVILLE
8PL GRDN
0 MVR
8VOLUNTE
8WILSON
8WEAKLEY
8BULL RU
8WAKE
8DAVIDSO
8MAURY
8WBNP 1
8MCGUIRE
1129 MW
0183
MVRMVR
8JACKSON
8FRANKLI
8SNP
8SHELBY
8CUMBERL
8RACCOON
8CORDOVA
340 MVR
8RICHMON
8JOCASSE
8BAD CRK
WM-EHV 8
8OCONEE
0 MVR
8WID CRK
8MADISON 8BNP 1
8BNP 2
8FREEPOR
8LIMESTO
8BFNP
8TRINITY
8UNION
8BOWEN
8BIG SHA
8VILLA R
8W POINT
8BULLSLU
8NORCROS
8KLONDIK
8UNIONCT
8MILLER
8WANSLEY
8LOWNDES
8S. BESS
8SCHERER
MCADAM 8
8HATCH8
8FARLEY
8SEPTA
8YADKIN
8FENTRES
8CLOVER
WHITPAIN
BRANCHBG
DEANS
SMITHBRG
Indian Point
Buchanan
Millwood
Pleasantville
Eastview
Shoreham
Port Jefferson
Wildwood
Riverhead
Dunwoodie Sprain Brook
Northport
Dvnpt.
Elwood
NK
Holbrook Brookhaven
Tremont Hmp. Harbor
Greelawn
Syosset
Pilgrim Holtsville
Shore Rd.
Rainey
Lcst. Bethpage
Grv.
Lake Success
Newbridge
Ruland Rd.
WE49th
E.G.C.
15thSt.
St.Corona
Farragut
Vernon
Jamaica
Cogen
Gowanus
Tech Valley Stream
Barrett
Greenwood
Goethals
Fresh Kills
Fox Hills
Figure shows
transmission
lines at 345
kV or above
in Eastern
U.S.
9
Zoomed View of Midwest
PAD 345
05BENTON
ZION ; B
ZION ; R
WEMPL; B
19MADRD
1115 MW
-185 MVR
WEMPL; R
LIBER; R
SILVE; R
05COOK
NB159;1M
NB159; B
CHERR; R
600 MW
-41 MVR
PH117; R
CHERR; B
03BAY SH
05KENZIE
53%
GOLF ; R
DP 46; B
DP 46; R
WAYNE; R
BYRON; R
BYRON; B
SK 88; R
GOLF ; B
19MAJTC
03DAV-BE
SK 88; B
05TWIN B
W407K; R
W407M;9T
W407K;9T
05OLIVE
ITASC;1M
05EELKHA
05JACKSR
17HIPLE
03LEMOYN
ELMHU; B
LOMBA; B
CRAWF; B
ELMHU; R
LOMBA; R
TAYLO; B
17MCHCTY
TAYLO; R
CRAWF; R
05DUMONT
?????
ELECT; B
H471 ;
17DUNACR
GARFI; B
ELECT; R
17STLWEL
BEDFO; R
MCCOO; B
NELSO; B
MCCOO; R
LISLE; B
CALUM; B
SLINE; B
SLINE; R
17CHIAVE
BEDFO;RT
BURNH; B
GOODI;3B
GOODI;1R
GOODI;4B
GOODI;2R
B ISL; R
17LKGORG
BURNH;4M
BURNH;0R
05COLNGW
05FOSTOR
G ACR; T
S JOH; T
LOCKP; R
PLANO; R
BLOOM; R
E FRA; B
E FRA; R
JO 29; B
JO 29; R
PLANO;
05S.BTLR
17TWR RD
17MUNSTR
BURNH;1R
LOCKP; B
PLANO; B
17BABCOK
17SHEFLD
LISLE; R
17LESBRG
17GRNACR
17BUROAK
17STJOHN
WILTO;
WILTO;
05ROB PK
05ALLEN
17SCHAHF
DRESD; B
DRESD; R
05SORENS
COLLI; R
COLLI;
DAVIS; B
LASCO; B
05E LIMA
DAVIS; R
LASCO; R
02GALION
08DEEDSV
BRAID; B
05REYNOL
BRAID; R
05SW LIM
05DEQUIN
08WALTON
56%
05GRNTWN
08WESTWD
02TANGY
PONTI;
?????
05HYATT
05MARYSV
TAZEWELL
05DESOTO
POWER; R
05CORRID
POWER; B
09NETAP
09CLINTO
05HAYDEN
DUCK CRK
05ROBERT
BROKA; T
09KILLEN
05BEATTY
08NOBLSV
?????
05FALL C
?????
08WHITST
16GUION
08NUCOR
CLINTON
RISING
SIDNEY
MAROA W
09BATH
BUNSONVL
16SUNNYS
05EUGENE
09GIVENS
08GRNBOR
16ROCKVL
08CAYUGA
MAROA E
08CAY CT
LATHA; T
16THOMPS
16HANNA
OREANA E
16STOUT
08GWYNN
08TDHNTR
09URBANA
?????
08WODSDL
KANSAS
08FOSTER
69%
08DRESSR
KINCA;
08P.UNON
07BLOMNG
08M.FTHS
62%
PAWNEE
NEOGA
PANA
CASEY
08OKLND
200 MW
6 MVR
08TERMNL
08M.FORT
08REDBK1
05TANNER
05BREED
60%
05SULLVA
05MARQUI
500 MW
25 MVR
08REDBK2
06DEARBN
07WORTHN
08SGROVE
62%
08COLMBU
RAMSEY
06PIERCE
?????
07MEROM5
08ZIMER
08EBEND
COFFEN N
COFFEEN
08BUFTN1
?????
NEWTON
?????
08ALENJT
05JEFRSO
08BEDFRD
12GHENT
06CLIFTY
70%
09CARGIL
Arrows
indicate MW
flow on the
lines;
piecharts
show
percentage
loading of
lines
10
Example Three Bus System
Pie charts
show
percentage
loading of
lines
Bus 2
-17 MW
3 MVR
17 MW
-3 MVR
Bus 1
1.00 pu
200 MW
100 MVR
Generator
1.00 pu
100 MW
2 MVR
150 MW
AGC ON
114 MVR AVR ON
-17 MW
5 MVR
-33 MW
10 MVR
33 MW
-10 MVR
100 MW
17 MW
-5 MVR
1.00 pu
Bus 3
100 MW
50 MVR
Bus
150 MW
AGC ON
35 MVR AVR ON
Circuit Breaker
Load
11
Generation
• Large plants predominate, with sizes up to about
•
•
•
1500 MW.
Coal is most common source, followed by hydro,
nuclear and gas.
Gas is now most economical.
Generated at about 20 kV.
12
Loads
• Can range in size from less than a single watt to
•
•
10’s of MW.
Loads are usually aggregated.
The aggregate load changes with time, with
strong daily, weekly and seasonal cycles.
13
Transmission
• Goal is to move electric power from generation to
•
•
•
load with as low of losses and cost as possible.
P = V I or P/V = I
Losses are I2 R
Less losses at higher voltages, but more costly to
construct and insulate.
14
Transmission and Distribution
• Typical high voltage transmission voltages are
•
•
•
•
500, 345, 230, 161, 138 and 69 kV.
Transmission tends to be a grid system, so each
bus is supplied from two or more directions.
Lower voltage lines are used for distribution, with
a typical voltage of 12.4 kV.
Distribution systems tend to be radial.
Transformers are used to change the voltage.
15
Other One-line Objects
• Circuit Breakers - Used to open/close devices; red
•
•
•
is closed, green is open.
Pie Charts - Show percentage loading of
transmission lines.
Up/down arrows - Used to control devices.
Values - Show current values for different
quantities.
16
Power Balance Constraints
• Power flow refers to how the power is moving
•
•
•
through the system.
At all times the total power flowing into any bus
MUST be zero!
This is know as Kirchhoff’s law. And it can not
be repealed or modified.
Power is lost in the transmission system.
17
Basic Power Control
• Opening a circuit breaker causes the power flow
•
•
to instantaneously(nearly) change.
No other way to directly control power flow in a
transmission line.
By changing generation we can indirectly change
this flow.
18
Flow Redistribution Following Opening
Line Circuit Breaker
Bus 2
-50 MW
11 MVR
50 MW
-9 MVR
Bus 1
1.00 pu
200 MW
100 MVR
1.00 pu
101 MW
6 MVR
150 MW
AGC ON
111 MVR AVR ON
-50 MW
16 MVR
0 MW
0 MVR
0 MW
0 MVR
No flow on
open line
100 MW
50 MW
-14 MVR
1.00 pu
Bus 3
100 MW
50 MVR
150 MW
AGC ON
36 MVR AVR ON
Power Balance must
be satisfied at each bus
19
Indirect Control of Line Flow
Bus 2
16 MW
-3 MVR
-16 MW
3 MVR
Bus 1
1.00 pu
200 MW
100 MVR
1.00 pu
2 MW
30 MVR
150 MW
AGC ON
118 MVR AVR ON
-82 MW
27 MVR
-66 MW
21 MVR
67 MW
-19 MVR
83 MW
-23 MVR
1.00 pu
Bus 3
Generator MW
output changed
100 MW
50 MVR
250 MW
OFF AGC
8 MVR AVR ON
100 MW
Generator change
indirectly changes
line flow
20
Transmission Line Limits
• Power flow in transmission line is limited by a
•
•
number of considerations.
Losses (I2 R) can heat up the line, causing it to
sag. This gives line an upper thermal limit.
Thermal limits depend upon ambient conditions.
Many utilities use winter/summer limits.
21
Overloaded Transmission Line
Bus 2
359 MW
179 MVR
150 MW
AGC ON
234 MVR AVR ON
-152 MW
37 MVR
154 MW
-24 MVR
104%
104%
1.00 pu
Thermal limit
of 150 MVA
58 MW
-16 MVR
-87 MW
29 MVR
1.00 pu
Bus 3
179 MW
90 MVR
150 MW
AGC ON
102 MVR AVR ON
1.00 pu
343 MW
-49 MVR
89 MW
-24 MVR
-57 MW
18 MVR
Bus 1
100 MW
22
Interconnected Operation
• Power systems are interconnected across large
•
distances. For example most of North American
east of the Rockies is one system, with most of
Texas and Quebec being major exceptions
Individual utilities only own and operate a small
portion of the system, which is referred to an
operating area (or an area).
23
Operating Areas
• Areas constitute a structure imposed on grid.
• Transmission lines that join two areas are known
•
•
as tie-lines.
The net power out of an area is the sum of the
flow on its tie-lines.
The flow out of an area is equal to
total gen - total load - total losses = tie-flow
24
Three Bus System Split into Two Areas
Initially
area flow
is not
controlled
Bus 2
-29 MW
6 MVR
29 MW
-6 MVR
Bus 1
1.00 pu
214 MW
107 MVR
1.00 pu
121 MW
-3 MVR
150 MW
AGC ON
124 MVR AVR ON
Home Area
-8 MW
2 MVR
-35 MW
11 MVR
35 MW
-10 MVR
8 MW
-2 MVR
1.00 pu
Bus 3
107 MW
53 MVR
Scheduled Transactions
0.0 MW
Off AGC
150 MW
AGC ON
41 MVR AVR ON
100 MW
Area 2
Net tie flow
is NOT zero
25
Area Control Error (ACE)
• The area control error mostly the difference
•
•
•
between the actual flow out of area, and
scheduled flow.
ACE also includes a frequency component.
Ideally the ACE should always be zero.
Because the load is constantly changing, each
utility must constantly change its generation to
“chase” the ACE.
26
Home Area ACE
Bus 2
-12 MW
2 MVR
12 MW
-2 MVR
Bus 1
1.00 pu
255 MW
128 MVR
20.0
1.00 pu
106 MW
-1 MVR
227 MW
OFF AGC -17 MW
5 MVR
135 MVR AVR ON
17 MW
-5 MVR
Home Area
Area Control Error (MW)
10.0
-10.0
Bus 3
-20.0
Scheduled Transactions
0.0 MW
Off AGC
-6 MW
2 MVR
0.0
6 MW
-2 MVR
1.00 pu
12806:30
MW AM
64 MVR
100 MW
Area 2
06:15 AM
Time
150 MW
AGC ON
57 MVR AVR ON
ACE changes with time
27
Inadvertent Interchange
• ACE can never be held exactly at zero.
• Integrating the ACE gives the inadvertent
•
•
interchange, expressed in MWh.
Utilities keep track of this value. If it gets
sufficiently negative they will “pay back” the
accumulated energy.
In extreme cases inadvertent energy is purchased
at a negotiated price.
28
Automatic Generation Control
• Most utilities use automatic generation control
•
(AGC) to automatically change their generation to
keep their ACE close to zero.
Usually the utility control center calculates ACE
based upon tie-line flows; then the AGC module
sends control signals out to the generators every
couple seconds.
29
Three Bus Case on AGC
Bus 2
-22 MW
4 MVR
22 MW
-4 MVR
Bus 1
1.00 pu
214 MW
107 MVR
1.00 pu
100 MW
2 MVR
150 MW
AGC ON
124 MVR AVR ON
Home Area
-22 MW
7 MVR
-42 MW
13 MVR
42 MW
-12 MVR
22 MW
-6 MVR
1.00 pu
Bus 3
107 MW
53 MVR
Scheduled Transactions
0.0 MW
ED
171 MW
AGC ON
35 MVR AVR ON
100 MW
Area 2
With AGC on, net
tie flow is zero, but
individual line flows
are not zero
30
Generator Costs
• There are many fixed and variable costs
•
•
•
associated with power system operation.
Generation is major variable cost.
For some types of units (such as hydro and
nuclear) it is difficult to quantify.
For thermal units it is much easier. There are four
major curves, each expressing a quantity as a
function of the MW output of the unit.
31
Generator Cost Curves
• Input-output (IO) curve: Shows relationship
•
•
•
between MW output and energy input in Mbtu/hr.
Fuel-cost curve: Input-output curve scaled by a
fuel cost expressed in $ / Mbtu.
Heat-rate curve: shows relationship between MW
output and energy input (Mbtu / MWhr).
Incremental (marginal) cost curve shows the cost
to produce the next MWhr.
32
Example Generator Fuel-Cost Curve
10000
7500
Fuel-cost ($/hr)
Y-axis
tells
cost to
produce
specified
power
(MW) in
$/hr
5000
Current generator
operating point
2500
0
0
150
300
450
Generator Power (MW)
600
33
Example Generator Marginal Cost
Curve
Incremental cost ($/MWH)
Y-axis
tells
marginal
cost to
produce
one more
MWhr in
$/MWhr
20.0
15.0
10.0
Current generator
operating point
5.0
0.0
0
150
300
450
Generator Power (MW)
600
34
Economic Dispatch
• Economic dispatch (ED) determines the least cost
•
dispatch of generation for an area.
For a lossless system, the ED occurs when all the
generators have equal marginal costs.
IC1(PG,1) = IC2(PG,2) = … = ICm(PG,m)
35
Power Transactions
• Power transactions are contracts between areas to
•
•
do power transactions.
Contracts can be for any amount of time at any
price for any amount of power.
Scheduled power transactions are implemented by
modifying the area ACE:
ACE = Pactual,tie-flow - Psched
36
Implementation of 100 MW Transaction
Bus 2
-31 MW
6 MVR
31 MW
-6 MVR
Bus 1
1.00 pu
Overloaded
line
340 MW
170 MVR
1.00 pu
1 MW
38 MVR
112%
150 MW
AGC ON
232 MVR AVR ON
Home Area
-130 MW
44 MVR
-159 MW
55 MVR
163 MW
-41 MVR
112%
Bus 3
170 MW
85 MVR
Scheduled Transactions
100.0 MW
ED
133 MW
-35 MVR
1.00 pu
466 MW
AGC ON
9 MVR AVR ON
Scheduled Transaction
100 MW
Area 2
Net tie flow is
now 100 MW from
left to right
37
Security Constrained ED
• Transmission constraints often limit system
•
•
economics.
Such limits required a constrained dispatch in
order to maintain system security.
In three bus case the generation at bus 3 must be
constrained to avoid overloading the line from bus
2 to bus 3.
38
Security Constrained Dispatch
Gens 2 &3
changed to
remove
overload
Bus 2
-22 MW
4 MVR
22 MW
-4 MVR
Bus 1
1.00 pu
340 MW
170 MVR
1.00 pu
-0 MW
37 MVR
100%
177 MW
OFF AGC -142 MW
49 MVR
223 MVR AVR ON
145 MW
-37 MVR
-122 MW
41 MVR
100%
Home Area
Bus 3
170 MW
85 MVR
Scheduled Transactions
100.0 MW
ED
124 MW
-33 MVR
1.00 pu
439 MW
AGC ON
15 MVR AVR ON
100 MW
Area 2
Net tie flow is
still 100 MW from
left to right
39
Multi-Area Operation
• The electrons are not concerned with area
•
•
boundaries. Actual power flows through the
entire network according to impedance of the
transmission lines.
If Areas have direct interconnections, then they
can directly transact up their tie-line capacity.
Flow through other areas is known as “parallel
path” or “loop flows.”
40
Seven Bus, Thee Area Case One-line
44 MW
Area
“Top”
has 5
buses
-42 MW
1.05 pu
1
3
79 MW
2
40 MW
20 MVR
1.00 pu
-32 MW
Case Hourly Cost
16933 $/MWH
32 MW
80 MW
30 MVR
4
110 MW
40 MVR
38 MW
-61 MW
1.04 pu
31 MW
0.99 pu
106 MW -37 MW
AGC ON
62 MW
-31 MW
Top Area Cost
5
-39 MW
40 MW
-14 MW
1.01 pu
-77 MW
8029 $/MWH
94 MW
AGC ON
ACE for
each area
is zero
130 MW
40 MVR
168 MW AGC ON
-40 MW
20 MW
-20 MW
40 MW
1.04 pu
6
200 MW
1.04 pu
20 MW
200 MW
Left Area Cost
0 MVR
4189 $/MWH
AGC ON
Area “Left” has one bus
7
-20 MW
200 MW
0 MVR
Right Area Cost
4715 $/MWH
201 MW AGC ON
Area “Right” has one bus
41
Seven Bus Case: Area View
Top
Area Losses
7.09 MW
40.1 MW
0.0 MW
-40.1 MW
0.0 MW
Left
Area Losses
0.33 MW
Right
40.1 MW
0.0 MW
Area Losses
0.65 MW
Actual
flow
between
areas
Scheduled
flow
between
areas
42
Seven Bus Case with 100 MW Transfer
Top
Area Losses
9.45 MW
4.8 MW
0.0 MW
-4.8 MW
0.0 MW
Left
Area Losses
0.00 MW
Right
104.8 MW
100.0 MW
Area Losses
4.34 MW
100 MW Scheduled Transfer from Left to Right
Losses
went up
from
7.09
MW
43
Seven Bus Case One-line
45 MW
Transfer 1.05 pu
1
also
60 MW
overloads
line in Top
40 MW
-60 MW
1.04 pu
-44 MW
3
27 MW
0.99 pu
106 MW -39 MW
AGC ON
36 MW
106 MW
80 MW
30 MVR
4
110 MW
40 MVR
106%
Top Area Cost
8069 $/MWH
1.00 pu
-35 MW
Case Hourly Cost
16654 $/MWH
2
40 MW
20 MVR
-27 MW
-102 MW
5
-4 MW
5 MW
97 MW
AGC ON
-24 MW
1.01 pu
130 MW
40 MVR
167 MW AGC ON
-5 MW
52 MW
-50 MW
1.04 pu
6
300 MW
5 MW
1.04 pu
52 MW
200 MW
Left Area Cost
0 MVR
5943 $/MWH
AGC ON
7
-50 MW
200 MW
0 MVR
Right Area Cost
2642 $/MWH
104 MW AGC ON
44
Transmission Service
• FERC Order No. 888 requires utilities provide
•
non-discriminatory open transmission access
through tariffs of general applicability.
FERC Order No. 889 requires transmission
providers set up OASIS (Open Access Same-Time
Information System) to show available
transmission.
45
Transmission Service
• If areas (or pools) are not directly interconnected,
•
•
they must first obtain a contiguous “contract
path.”
This is NOT a physical requirement.
Utilities on the contract path are compensated for
wheeling the power.
46
Eastern Interconnect Example
CORNWALL
NSP
NEPOOL
WPS
NYPP
ONT HYDR
DPC
SMP
MGE
DECO
WEP
WPL
CONS
IPW
PENELEC
PP&L
MEC
PSE&G
TE
NI
OE
CEI
PJM500
DLCO
CILCO
MPW
NIPS
JCP&L
OPPD
PECO
AEP
METED
IP
IESC
AE
CWLP
DPL
BG&E
IPL
AP
CIN
CIPS
STJO
MIPU
DPL
PEPCO
HE
KACY
IMPA
OVEC
VP
SIGE
KACP
EMO
BREC
SIPC
INDN
EKPC
KU
LGE
EEI
ASEC
YADKIN
DOE
CPLW
EMDE
GRRD
SPRM
CPLE
DUKE
KAMO
SWPA
HARTWELL
SEPA-JST
PSOK
SCE&G
SCPSA
SOUTHERN
ENTR
SEPA-RBR
AEC
SWEP
Arrows
indicate
the
basecase
flow
between
areas
47
Power Transfer Distribution Factors
(PTDFs)
• PTDFs are used to show how a particular
•
•
transaction will affect the system.
Power transfers through the system according to
the impedances of the lines, without respect to
ownership.
All transmission players in network could be
impacted, to a greater or lesser extent.
48
PTDFs for Transfer from Wisconsin
Electric to TVA
CORNWALL
NSP
WPS
19%
NYPP
DPC
10%
SMP
ONT HYDR
55%
54%
MGE
DECO
8%
CONS
22%
7%
MEC
8%
NPPD
55%
PENELEC
39%
16%
8%
CILCO
MPW
PJM500
DLCO
13%
PECO
AEP
METED
IP
IESC
6%
OE
CEI
7%
NIPS
OPPD
LES
PP&L
TE
NI
8%
7%
7%
WEP
10%
WPL
IPW
CWLP
6%
DPL
7%
9%
6%
IPL
BG&E
5%
AP
CIN
CIPS
STJO
MIDW
MIPU
PEPCO
HE
KACY
IMPA
OVEC
9%
11%
8%
WERE
VP
SIGE
KACP
BREC
EMO
INDN
EKPC
SIPC
KU
9%
LGE
EEI
13%
ASEC
19%
6%
7%
YADKIN
DOE
CPLW
10%
EMDE
OMPA
GRRD
8%
SPRM
DUKE
11%
7%
WEFA
KAMO
SWPA
11%
20%
25%
HARTWELL
SEPA-JST
OKGE
PSOK
SCE&G
SCPSA
SOUTHERN
6%
ENTR
SEPA-RBR
CPLE
Piecharts
indicate
percentage
of transfer
that will
flow
between
specified
areas
49
PTDF for Transfer from WE to TVA
NSP
WPS
19%
DPC
10%
54%
SMP
MGE
DECO
8%
10%
WPL
IPW
22%
7%
MEC
7%
8%
MPW
7%
WEP
CONS
55%
TE
NI
8%
8%
CILCO
16%
39%
NIPS
IP
IESC
CWLP
7%
9%
CIPS
MIPU
7%
13%
OPPD
STJO
100% of
transfer
leaves
Wisconsin
Electric
(WE)
55%
DPL
IPL
6%
50
PTDFs for Transfer from WE to TVA
SIGE
BREC
EKPC
SIPC
KU
LGE
EEI
6%
19%
7%
8%
YADKIN
DOE
CPLW
10%
DUKE
About
100% of
transfer
arrives at
TVA
T VA
11%
20%
25%
HARTWELL
SEPA-JST
SCE&G
SCPSA
SOUTHERN
SEPA-RBR
But flow
does NOT
follow
contract
path
51
Contingencies
• Contingencies are the unexpected loss of a
•
•
•
significant device, such as a transmission line or a
generator.
No power system can survive a large number of
contingencies.
First contingency refers to loss of any one device.
Contingencies can have major impact on Power
Transfer Distribution Factors (PTDFs).
52
Available Transfer Capability
• Determines the amount of transmission capability
•
available to transfer power from point A to point
B without causing any overloads in basecase and
first contingencies.
Depends upon assumed system loading,
transmission configuration and existing
transactions.
53
Reactive Power
• Reactive power is supplied by
– generators
– capacitors
– transmission lines
– loads
• Reactive power is consumed by
– loads
– transmission lines and transformers (very high losses
54
Reactive Power
• Reactive power doesn’t travel well - must be
•
supplied locally.
Reactive must also satisfy Kirchhoff’s law - total
reactive power into a bus MUST be zero.
55
Reactive Power Example
Bus 2
359 MW
179 MVR
-152 MW
37 MVR
154 MW
-24 MVR
104%
104%
Bus 1
1.00 pu
1.00 pu
343 MW
-49 MVR
150 MW
AGC ON
234 MVR AVR ON
Note
reactive
line losses
are about
13 Mvar
89 MW
-24 MVR
-57 MW
18 MVR
58 MW
-16 MVR
-87 MW
29 MVR
1.00 pu
Bus 3
179 MW
90 MVR
150 MW
AGC ON
102 MVR AVR ON
100 MW
Reactive
power
must also
sum to
zero at
each bus
56
Voltage Magnitude
• Power systems must supply electric power within
•
•
a narrow voltage range, typically with 5% of a
nominal value.
For example, wall outlet should supply
120 volts, with an acceptable range from 114 to
126 volts.
Voltage regulation is a vital part of system
operations.
57
Reactive Power and Voltage
• Reactive power and voltage magnitude are tightly
•
coupled.
Greater reactive demand decreases the bus
voltage, while reactive generation increases the
bus voltage.
58
Voltage Regulation
• A number of different types of devices participate
in system voltage regulation
– generators: reactive power output is automatically
changed to keep terminal voltage within range.
– capacitors: switched either manually or automatically
to keep the voltage within a range.
– Load-tap-changing (LTC) transformers: vary their offnominal tap ratio to keep a voltage within a specified
range.
59
Five Bus Reactive Power Example
1.00 pu
200 MW
100 MVR
1.000 pu
100 MW
143 MW
5 MVR
405 MW
96 MVR
12 MVR
61 MW
AGC ON
-2 MVR
AVR ON
Bus 4
LTC
Transformer
is
controlling
load voltage
100 MW
10 MVR
Bus 5
0.982 pu
-40 MW
24 MVR
Bus 3
3 L
0.994 pu
0.995 pu
100 MW
0 MVR
-60 MW
5 MVR
100 MW
79 MVR
50 MVR
100 MW
Voltage
magnitude
is
controlled
by
capacitor
60
Voltage Control
• Voltage control is necessary to keep system
•
•
voltages within an acceptable range.
Because reactive power does not travel well, it
would be difficult for it to be supplied by a third
party.
It is very difficult to assign reactive power and
voltage control to particular transactions.
61
Conclusion
• Talk has provided brief overview of how power
•
grid operates.
Educational Version of PowerWorld Simulator,
capable of solving systems with up to 12 buses,
can be downloaded for free at
www.powerworld.com
• 60,000 bus commercial version is also available.