Transcript ppt

If I were to give grades today…
> 80
78-80
76-78
70-76
68-70
66-68
60-66
58-60
56-58
50-56
48-50
<48
A
AB+
B
BC+
C
CD+
D
DF
8
2
4
7
5
4
7
1
1
8
1
2
=(0.2*Ex1+0.2*Ex2+0.15*HW)/0.55
1
Notes on security assessment
James D. McCalley
2
3
Types of security violations & consequences
Security
Overload
Security
Xfmr
overload
Line
overload
Cascading
overloads
Voltage
Security
Low
Voltage
Dynamic
Security
Unstable
Voltage
Slow
voltage
collapse
Fast
voltage
collapse
Earlyswing
instability
Oscillatory
instability
(damping)
Smalldisturbance
instability
Largedisturbance
4
instability
Types of security violations & consequences
Overloaded xfmr/line has
higher tripping likelihood,
resulting in loss of another
element, possible
cascading, voltage or
dynamic insecurity
Overload
Security
Xfmr
overload
Line
overload
Cascading
overloads
Dynamic security can
result in loss of generation;
growing oscillations can
Security cause large power swings
to enter relay trip zones
Voltage
Security
Dynamic
Security
Low
voltageUnstable
affects
EarlyOscillatory
Low
swing
instability
load
and generation
Voltage
Voltage
instability
(damping)
operation. Voltage
instability can result
in widespread loss
SmallLargeSlow
Fast
of
load.
voltage
collapse
voltage
collapse
disturbance
instability
disturbance
5
instability
Traditional assessment & decision
 The NERC Disturbance-Performance Table
 DyLiacco’s operational decision paradigm
 System operating limits
6
NERC Disturbance-Performance Table
7
NERC Disturbance-Performance Table, cont
8
NERC Disturbance-Performance Table, cont
9
Normal
One Element Out of
Service
Two of More Elements
Out of Service
Extreme Events (Two or More
Elements Out of Service)
Single Contingency (Forced or
Maint) Category B Event B
Results In:
•No Cascading
•No load loss
•No overload
•No voltage limit violation
•Possible RAS operation
Prepare for Contingency
•Implement Limits
Prepare for Next Contingency
•Limit Import/Export
•Curtail Generation
•Shed Load
B Single Line Ground
(SLG) or 3-Phase (3Ø)
Fault, with Normal
Clearing on:
1. Generator
2. Transmission Circuit
3. Transformer
Or loss of an element
without a fault.
4. Single Pole Block,
Normal Clearing of a DC
Line
Single Contingency (Category B Event) B
Category C event: A
first contingency,
followed by
adjustments, followed
by a second
contingency)
•No Cascading
•May Result In:
•Generation curtailment
•Load shedding
•Import/Export reductions
•Safety Net operation
Prepare for Next Contingency
•Limit Import/Export
•Curtail Generation
•Shed Load
10
Normal
One Element Out of
Service
Two of More Elements
Out of Service
Extreme Events (Two or More
Elements Out of Service)
Multiple Contingencies – Category C Event C1-8
C1-3 SLG Fault, with Normal
Clearing: 1. Bus Section
2. Breaker (failure or internal fault)
SLG or 3Ø Fault, with Normal
Clearing.
3. Category B (B1, B2, B3, or B4)
contingency, manual system
adjustments, followed by another
Category B (B1, B2, B3, or B4)
contingency
C4-8
•No Cascading
•May Result In:
•Generation curtailment
•Load shedding
•Import/Export reductions
•Safety Net operation
Prepare for Next Contingency
•Limit Import/Export
•Curtail Generation
•Shed Load
4. Bipolar (dc) Line
Fault (non 3Ø), with Normal
Clearing:
5. Any two circuits of a
multiple circuit towerline
SLG Fault, with Delayed
Clearing and (stuck breaker
or protection system failure):
6.Generator 7.Trans Circuit
8. Xmer 9. Bus Section
Extreme (Category D) Event – May originate from any Operating State D1-14
D12-14 12. Failure of a fully
D1 3Ø Fault, with Delayed Clearing
(stuck breaker or protection system failure):
1. Generator 2. trans Circuit
3. Xmer 4. Bus Section
3Ø Fault, with Normal Clearing:
5. Breaker (failure or internal fault)
6. Loss of tower line with 3 or more ckts 7.
All trans lines on a common right-of way
8. Loss of a subs (one voltage level +Xmer)
9. Loss of a switching st (one voltage + plus
Xmer) 10. Loss of all generating units at a
station 11. Loss of a large load or major
load center
redundant special protection
system (or remedial action
scheme) to operate when required
13. Operation, partial operation or
misoperation of a fully redundant
special protection system (or
remedial action scheme) for an
event or condition for which it was
not intended to operate
14. Impact of severe power swings
or oscillations from disturbances in
another Regional Council.
•No Cascading
•May Result In:
•Generation curtailment
•Load shedding
•Import/Export reductions
•Safety Net operation
Prepare for Next Contingency
•Limit Import/Export
11
•Curtail Generation
•Shed Load
DyLiacco’s operational decision paradigm
Normal (secure)
Restorative
Extreme emergency.
Separation, cascading
delivery point
interruption,
load shedding
Alert,
Not secure
Take corrective
actions
Emergency
12
System operating limits (SOLs)
The value (such as MW, MVar, Amperes, Frequency or Volts) that
satisfies the most limiting of the prescribed operating criteria for a
specified system configuration to ensure operation within
acceptable reliability criteria. System Operating Limits are based
upon certain operating criteria. These include, but are not limited to
applicable pre- and post-contingency…
•Facility Ratings
•Transient Stability Ratings
•Voltage Stability Ratings
•System Voltage Limits
There is a subset of SOLs that are known
as Interconnection Reliability Operating
Limits (IROL). IROLs are defined as, “The
value (such as MW, MVar, Amperes,
Frequency or Volts) derived from, or a
subset of the System Operating Limits,
which if exceeded, could expose a
widespread area of the Bulk Electric
System to instability, uncontrolled
13
separation(s) or cascading outages.”
Cascading outages – the public perception….
14
System operating limits
300 MW
Question 1: Is it
“secure”?
Bus 2
X23=1
X12=1
900 MW
X13=1
Bus 1
Bus 3
Continuous rating=1200MW
Emergency rating=1300 MW
1200 MW
Question 2: What is
maximum cct 1-3 flow
such that reliability
criteria is satisfied?
15
Treating power as if it is current….
V1
V2
P12
PG2
jx12
PG1
PD1
PD2
A very basic relation for power system engineers expresses the
real power flow across a transmission circuit as:
P12  V1 I12 cos 
(1)
Here, φ is the angle by which the voltage leads the current and is
called the power factor angle.
If we assume that electric loads are purely resistive, so that only
real power flows in the network, then φ≈0 (φ will not be exactly
zero because of line reactance). In this case, eq. (1) is:
P12  V1 I12
(2)
16
Treating power as if it is current….
A basic fact of power system is that the voltages usually do not
deviate significantly from their nominal value. Under a system of
normalization (called per-unit), where all voltages are
normalized with respect to this nominal voltage, it will be the
case that |Vk|≈1.0. As a result, eq. (2) becomes:
P12  I12
(3)
In other words, the numerical value of the real power flowing on the
circuit is the same as the numerical value of the current magnitude
flowing on that circuit (under the system of normalization).
If, again, the electric load is purely resistive, then all currents will have
almost the same angle, and one can treat the current magnitude as if it
were the current phasor.
Useful conclusion: If we assume voltage magnitudes are all unity, and
all loads are purely resistive, then whatever rules we have of dealing
17
with currents also work with real pu power flows! (or Sbase×pu pwr flws)
Two good approximations for parallel flows
1. Current division: For 2 parallel paths A and
B, power flows on path A according to
PTotal
XB
XA  XB
Bus 2
300
1
900
 300
2 1
X23=1
X12=1
900 MW
X13=1
Bus 1
2
900
 600
2 1
900 MW
Bus 3
18
Two good approximations for parallel flows
1. Current division: For 2 parallel paths A and
B, power flows on path A according to
PTotal
300 MW
300
XB
XA  XB
Bus 2
1
 100
2 1
300
X23=1
X12=1
2

2 1
200
X13=1
Bus 1
100
Bus 3
300 MW
19
Two good approximations for parallel flows
2. Superposition: Results of 2 independent
calculations will add
Bus 2
300 MW
300
100
Total=500
300
200
Total=200
900 MW
Total=700
Bus 1
600
100
Bus 3
1200 MW
Continuous rating=1200MW
Emergency rating=1300 MW
IS IT SATISFYING
RELIABILITY CRITERIA?
20
System operating limits
300 MW
Bus 2
The answer to
Question 1: Is it
“secure”?
Lose Cct 2-3!
900 MW
Total=1200
Bus 1
Bus 3
1200 MW
Continuous rating=1200MW
Emergency rating=1300 MW
IS IT SATISFYING
RELIABILITY CRITERIA?
YES!!!
21
System operating limits
Bus 2
300 MW
Total=500
Total=200
900 MW
Total=700
Bus 1
Bus 3
Question 2: What is
maximum cct 1-3 flow
such that reliability
criteria is satisfied?
1200 MW
Depends on how flow is
increased: assume stress direction
of Bus1/Bus3.
Desire precontingency limits to
22
reflect postcontingency effects
System operating limits
Bus 2
300 MW
333
100
Question 2: What is
maximum cct 1-3 flow
such that reliability
criteria is satisfied?
Total=533
333
200
Total=233
1000MW
Total=767
Bus 1
667
100
Bus 3
1300 MW
Continuous rating=1200MW
Emergency rating=1300 MW
IS IT SATISFYING
RELIABILITY CRITERIA?
23
System operating limits
300 MW
Bus 2
Lose Cct 2-3!
1000MW
Total=1300
Bus 1
Bus 3
Continuous limit=1200MW
Emergency limit=1300 MW
IS IT SATISFYING
RELIABILITY CRITERIA?
1300 MW
It is right at
the limit!
24
System operating limits
Bus 2
300 MW
Total=500
Total=200
900 MW
Total=700
Bus 1
SOL=767
Bus 3
Question 2: What is
maximum cct 1-3 flow
such that reliability
criteria is satisfied?
1200 MW
Answer
25
Illustration of real-time calculation of
operating security limits w/ DTS




What is dispatcher training simulator?
PTDF and OTDF
Automatic calculation of SOL
Sample system
26
What is the DTS?
 An off-line environment that:
Emulates an energy control center's EMS
 Simulates the physical power system
 DTS uses the same interfaces and is composed of
much of the same software as the real-time EMS

27
PTDF and OTDF
Power transfer dist. factors:
PTDFcct k
bus b
Change in Flow of cct k
[Change in injection of bus b]
Outage transfer dist. factors:
OTDFcct k
cct j

Change in Flow of cct k
Flow on outaged cct j
28
PTDF and OTDF
Power transfer dist. factors:
Change in Flow of cct k  PTDFcct k [Change in injection of bus b]
bus b
Outage transfer dist. factors:
Change in Flow of cct k  OTDF
cct k [Flow
cct j
on outaged cct j]
We will later show how to compute SOL using PTDFs ali and LODF dl,k
29
Automatic calculation of SOLs
 More than identifying contingencies that
result in violations, it identifies the LIMIT
 Overload security only
 Uses PTDFs, OTDFs, stress direction
 SOL for each cct computed as most
restrictive of
Normal condition, using continuous rating or
 All contingencies, using emergency rating

 Embedded in Areva’s DTS
 Updates SOL for all circuits every 8 sec
30
29
Outaged Line
24
25
26
30
27
28
Monitored Line
21
12
14
7
4
0
2
19
9
15
6
22
1
Outaged Line
17
23
20
16
10
3
18
31
310 MW
386 MW (7-28)
269 MW
825 MW (14-26)
37 MW
640 MW
269 MW (14-26)
797 MW (7-28)
143 MW
244 MW (27-28)
37 MW
269 MW (14-26)
195 MW
465 MW (21-24)
More than identifying
contingencies resulting in
violations, it identifies LIMITS
Current Time of DTS:
1/3/2000 3:01:01 AM
32
278 MW
319 MW (7-28)
139 MW
938 MW (14-26)
103 MW
301 MW (14-26)
610 MW
742 MW (7-28)
184 MW
280 MW (10-16)
103 MW
301 MW (14-26)
65 MW
457 MW (7-28)
More than identifying
contingencies resulting in
violations, it identifies LIMITS
Current Time of DTS:
1/3/2000 6:00:23 AM
33
89 MW
244 MW (7-28)
291 MW
716 MW (14-26)
163 MW
295 MW (14-26)
745 MW
834 MW (7-28)
267 MW
323 MW (10-16)
163 MW
295 MW (14-26)
75 MW
459 MW (25-26)
More than identifying
contingencies resulting in
violations, it identifies LIMITS
Current Time of DTS:
1/3/2000 8:00:05 AM
34
74 MW
224 MW (7-28)
311 MW
585 MW (14-26)
223 MW
839 MW
298 MW (14-26)
891 MW (7-28)
286 MW
341 MW (27-28)
223 MW
298 MW (14-26)
121 MW
438 MW (25-26)
More than identifying
contingencies resulting in
violations, it identifies LIMITS
Current Time of DTS:
1/3/2000 9:31:05 AM
35
56 MW
196 MW (7-28)
305 MW
759 MW (14-26)
325 MW
376 MW (14-26)
680 MW
779 MW (7-28)
392 MW
421 MW (10-16)
325 MW
376 MW (14-26)
285 MW
421 MW (25-26)
More than identifying
contingencies resulting in
violations, it identifies LIMITS
Current Time of DTS:
1/3/2000 11:01:31 AM
36
Flow vs. SOL (Picton:Brighton)
800
700
600
MW
500
400
300
200
100
0
1/3/2000 1/3/2000 1/3/2000 1/3/2000 1/3/2000 1/3/2000 1/3/2000 1/3/2000 1/3/2000
2:24
3:36
4:48
6:00
7:12
8:24
9:36
10:48
12:00
DTS time & day
Line Flow
SOL
Security Margin
Thermal Limit
37
SOL Equations:
f 0  f   f max
We want f 0 that along with f  would take the flow on the monitored cct to its max
Computing SOL
using PTDFs ali
and LODF dl,k
Following a P at node i and a - P at node j:
f   ai Pi  aj Pj  ai  aj Pi
Change on line k after a P on i and - P on j:
f k  aki  akj Pi
Outage of line k:
f   d  , k f k0  d  , k aki  akj Pi
Change on  after P at node i and a - P at node j and outage of line k:
f   ai  aj Pi  d ,k f k0  d  ,k aki  akj Pi
All the change on  will be set to f max
f 0  ai  aj Pi  d  ,k f k0  d  ,k aki  akj Pi  f max
f max  f 0  d  ,k f k0
Pi 
ai  aj  d  ,k aki  akj 
f OSL  f 0  ai  aj Pi
f
OSL

 f
0

a

i

 aj  f max  f 0  d  ,k f k0
ai  aj  d  ,k aki  akj 

38