Download Real Time Operations (Transmission)

Real Time
Operations
(Transmission)
Jarnail Bansal
David Gregory
1
Shift Structure
(19-21 shift staff positions)
National
Balancing
Engineer
Technical
Administrator
OPERATIONAL
ENERGY
MANAGER
Control 2
Zonal
Balancing
North
Transmission
Despatch
North 2/3
Transmission
Despatch
Scotland N&S
Zonal
Balancing
South
OPERATIONAL
TRANSMISSION
MANAGER
Transmission
Despatch
South * 3
Energy
Optimisation
Engineer
Energy
Scheduling
Engineer
Transmission
Analysis
Engineer
OPERATIONAL
STRATEGY
MANAGER
POWER
SYSTEM
MANAGER
Control 1
2
Future ENCC/TNCC Split
 Current Structure
ENCC (Wokingham)
NOC (Warwick)
TNCC
(Warwick)
Energy Balancing
Asset Monitoring
SO
Strategy
Network Security/
Network Control
Safety Management
SO/TO
Asset Monitoring
3
Future ENCC/TNCC Split
 New Structure
ENCC (Wokingham)
NOC (Warwick)
TNCC
(Warwick)
Energy Balancing
Asset Monitoring
Strategy
Network Security
SO
TO
Safety Management
Network Control
 ENCC role will focus on distinct SO challenges (energy balancing and system
security)
 TNCC role will focus on distinct TO challenges (Asset Management focused)
4
Constraint Management
Place your chosen
image here. The four
corners must just
cover the arrow tips.
For covers, the three
pictures should be the
same size and in a
straight line.
Jarnail Bansal
System Security
What the System may experience on average each year
4 busbar faults
5 cable faults
21 circuit
breaker faults
15 double cct faults
5 simultaneous faults
315 single cct faults
2000 protection or
Communication
failures
Transformer
10 faults
6
Operational Security Standards
 For any of the previous faults...
 There shall not be …
 A loss of Supply (exceptions apply)
 A permanent change in frequency below
49.5 Hz or above 50.5 Hz
 Unacceptable overloading of transmission
apparatus
 Unacceptable high or low voltage
conditions
 System Instability
7
Typical System Constraints
3000MW
7000MW
12000M
W
6000MW
 20-25 limits typically
active on any day
 Congestion will vary
with generation patterns
and transmission circuit
outages
 The system is not
geographically balanced
for generation and
demand
8
How are the risks managed? - Constraints
 Types of transmission constraint ...
 Thermal (Import or Export) - where there is a pre or post fault limit on
power imported or exported across a boundary
 Voltage - where voltage limits will be exceeded or voltage collapse
may occur post fault if limit across a boundary is exceeded
 Stability - where instability will result pre or post fault if a limit across a
boundary is exceeded
 Fault Level Limits - Limitation of number of machines that can be
synchronised in a localised area due to the potential to overstress
switchgear
 Response & Reserve Limits - Limitation on generation in a localised
area due to the potential for simultaneous loss of power infeed for a
credible fault
9
Circuit Thermally Overloaded
10
11
Thermal Constraint – example
4 x 500MW units
Circuit A
Thermal Export
Constraint
outaged
circuit
Circuit B
Full Load: 1500 MW
Drops req’d: 500
MW
MAX: 2000 MW
Rating
Pre-fault flow
Post fault
flow
Circuit A
2200
1100
Circuit B
1500
900
0
2000
Post-fault drops or
intertrip required
to contain
overload
12
Stability Limit
Limits the transfer of power
across relatively weak
interconnection of 2 sections
of the same AC system, ie
between Scotland & England
Stability
13
Stability - two types
Stability
Transient – a close up fault causes an
increasing oscillation which eventually shows
pole slipping. Factors include speed of AVR and
speed of protection.
Dynamic - steady state oscillation between
generators, either maintained or decreases at a
slower rate than is acceptable. Caused by
weak links to high generation export groups,
can result from system fault or normal switching. 14
Reactive Power and Voltage Control
Place your chosen
image here. The four
corners must just
cover the arrow tips.
For covers, the three
pictures should be the
same size and in a
straight line.
Reactive Power Control – Why?
Place your chosen
image here. The four
corners must just
cover the arrow tips.
For covers, the three
pictures should be the
same size and in a
straight line.
Reactive Power Control – Why?
 It’s all about voltage
 NGET has a licence requirement to
design, plan and operate the NETS in
accordance with the SQSS.
 The SQSS can be found here:
http://www2.nationalgrid.com/UK/
Industry-information/Electricitycodes/System-Security-andQuality-of-Supply-Standards/
 Licence requirement to design, plan
and operate the NETS safely and
securely
 The voltage limits in the SQSS mirror
those in The Electricity Safety, Quality
and Continuity Regulations
17
Reactive Power Affects the system voltage
Upper statutory limit
420 kV 303 kV 145 kV
MVAr sources increase
the system voltage
Nominal voltage
400 kV 275 kV 132 kV
MVAr sinks/demands
decrease the system voltage
Lower statutory limit
360 kV 248 kV 119 kV
18
What if NGET operate outside standards?
 At the very least we have to report this to OFGEM
…however
 It could have serious consequences
19
What if NGET operate outside standards?
 High voltages can lead to…
 Equipment damage
 NGET equipment
 Third party equipment
 Flashover
= safety implications
20
What if NGET operate outside standards?
 Low voltages can lead to…
 System instability
 Voltage collapse
 …blackouts!
21
Voltage Monitoring in Real Time
22
Voltage Monitoring in Real Time
23
Voltage Constraints
 Potential Voltage
Constraints
 Heavy concentration of load
in certain areas
 Power flow into these areas
activates constraint
 For security, plant in these
areas must run
24
Reactive Power Control – How?
Place your chosen
image here. The four
corners must just
cover the arrow tips.
For covers, the three
pictures should be the
same size and in a
straight line.
Reactive Power Control – How?
 NGET use a number of tools to manage the voltage profile on the NETS:
 Shunt connected plant (capacitors and reactors)
 Cable circuits
 Lightly loaded overhead lines
 SVC/Statcom
 Synchronous compensators
 Generators
 Offshore Transmission Systems
26
Future System Operation Challenges
Place your chosen
image here. The four
corners must just
cover the arrow tips.
For covers, the three
pictures should be the
same size and in a
straight line.
Future Operation
28
2013
Wind
Other
generation
2020
7GW
Wind
3G
W
69GW
Pumped
storage
2.7GW
Demand
58GW
7G
W
0.7GW
6GW
Interconnecto 4.2GW
rs
26GW
0.5GW
0.5GW
1GW
0.2G
10GW W
26GW
Other
generation
66GW
Pumped
storage
2.7GW
Demand
58GW
Interconnecto
rs
6.6GW
11G
W
7G
W
6GW
17GW
23GW
1.4GW
23GW
0.5GW
0.5GW
2GW 12GW
0.7GW
4GW
2G
10GW W
2GW
2GW 14GW
8GW
17GW
26GW
3.2GW
22GW
25GW
4.
0.3GW
29
Operating the system in 2020
Active Distribution
Networks
Variable generation
Synthetic
inertia
Smart
Grids &
meters
Variable generation
Distributed generation
Inflexible generation
Demand
60
1800MW loss risk
Electricity Demand (GW)
Variable generation
55
50
Peak Commuting Time
Active Demand
Large generation
Peak Commuting Time
Generation
ROCOF &
Robustness
issues
2020 Demand ~ 15
GWh (daily) - 1.5
million vehicles
45
Optimal Charging
Period
Typical winter daily
demand
40
12,000 miles p.a.
35
Time of Day
How to meet these challenges in the most economic
and sustainable way whilst maintaining security of
supply?
23:00
22:00
21:00
20:00
19:00
18:00
17:00
16:00
15:00
14:00
13:00
12:00
11:00
10:00
09:00
08:00
07:00
06:00
05:00
04:00
03:00
02:00
01:00
00:00
30
Time of use
tariffs
30
A complex system to operate
 More sophisticated operation needed to manage
uncertainty
 Needs
 better forecasting of likely outcomes
 analysing uncertainty more intensively
 improving economic cost of analysis for
delivering security
 maintaining flexibility to respond to changing
conditions
 More intensive planning and control process
focusing analytical effort to periods where
uncertainty is at its greatest requiring the rolling
Operational Plan to be updated
31
Reactive Power and Voltage Control
Place your chosen
image here. The four
corners must just
cover the arrow tips.
For covers, the three
pictures should be the
same size and in a
straight line.
Additional slides if required
Generator Reactive Power Dispatch
Place your chosen
image here. The four
corners must just
cover the arrow tips.
For covers, the three
pictures should be the
same size and in a
straight line.
Reactive Power Control from Generators
 The Grid Code defines two
broad types of generator:
 Synchronous
 i.e. conventional thermal
generators
 Non-Synchronous
 i.e. wind generators
34
Non-Synchronous Generating Unit
 Reactive power output governed
by the System voltage and the
Generator Setpoint Voltage and
Slope characteristic
 NGET instruct the Setpoint
Voltage and Slope values
 Instructions sent electronically
 Generator to change values and
maintain at that level until
otherwise instructed
35
Synchronous Generating Unit
 Reactive power output governed
by automatic excitation control
system and generator transformer
tap position
 NGET instruct either a MVAr
Output or, in exceptional
circumstances, a Target Voltage
Level
 Instruction sent electronically
 Generator to tap generator step
up transformer to achieve
instructed position and not tap
again unless otherwise instructed
or agreed
36
Synchronous Generating Unit
 NGET may also instruct a Tap
Change
 Tap generator step up
transformer to raise or lower
System voltage
 Normally used for a
Simultaneous Tap Change
instruction
 Simultaneous Tap Change
instructed via Fax and telephone
37
General Grid Code Requirements
 Reactive power instructions can be issued at any time (BC2.8.1)
 Assumed always available unless told otherwise (BC2.8.1) (MVAr
Redeclaration – BC2.A.3)
 They cannot be rejected, except on safety grounds, or where the
instruction would take the Genset outside of their notified operating
parameters (BC2.8.3)
 They must be acted on with within 2 minutes (BC2.8.4)
 Except changes to Slope settings which are not required to be
changed in less than one week (BC2.A.2.6)
38
General Grid Code Requirements
 The Grid Code specifies minimum Reactive Power
requirements for:
 Onshore Synchronous Generators
 Onshore Non-Synchronous Generators
Same requirements apply to Onshore DC Convertors,
Power Park Modules and OTSDUW Plant and Apparatus
at the Interface Point
 Generators connected Offshore
Applies to Synchronous Generators, Non-Synchronous
Generators, DC Convertors and Power Park Modules
 Details in CC.6.3.2
39
SO-TO Code Requirements
 Section K of the STC specifies minimum Reactive
Power requirements for Offshore Transmission
Systems at the Interface Point
 Mirrors the requirements in the Grid Code that apply to
Onshore Non-Synchronous Generators, Onshore DC
Convertors, Power Park Modules and OTSDUW Plant
and Apparatus at the Interface Point
 Details in STC Section K, part 2
40
Reactive Power and Voltage Control
Place your chosen
image here. The four
corners must just
cover the arrow tips.
For covers, the three
pictures should be the
same size and in a
straight line.
Minimum Reactive Power Requirements
Place your chosen
image here. The four
corners must just
cover the arrow tips.
For covers, the three
pictures should be the
same size and in a
straight line.
Onshore Synchronous Generator
 When supplying Rated MW,
must be capable of supplying
continuously between 0.85 pf
lagging to 0.95 pf leading
 At all other Active Power
outputs other than Rated MW,
must be capable of continuous
operation between the
Reactive Power limits defined
on the Generator
Performance Chart
43
Onshore Non-Synchronous Generator
 Defined in terms of Rated MW
or Interface Point Capacity
 A ≡ 0.95 pf leading
 B ≡ 0.95 pf lagging
 C ≡ -5% Rated MW in
MVAr
 D ≡ 5% Rated MW in
MVAr
 E ≡ -12% Rated MW in
MVAr
44
Offshore Generator
 At all Active Power output levels an Offshore
Generator should either:
 Maintain zero transfer of Reactive Power at the
Offshore Grid Entry Point at the LV Side of the
Offshore Platform; or
 Maintain a transfer of Reactive Power at the Offshore
Grid Entry Point … that will be equivalent to zero at the
LV Side of the Offshore Platform; or
 As otherwise agreed with the Generator, Offshore
Transmission Licensee and NGET
45
Offshore Generator
 SO-TO Code places
requirement on OFTO to
provide reactive power to the
Onshore Transmission
System
 Identical to Grid Code
requirement for Onshore NonSynchronous Generators
 Defined in STC Section K
46