FACTS Technical Compendium

Discover the World of FACTS Technology
Technical Compendium
Answers for energy.
Contents
Chapter
1
3
1.1
FACTS – What and why?
3
1.2
FACTS for supplying power – Now and in the future
3
1.3
Tasks of FACTS devices
3
Basics
4
Reactive power compensation
4
3
Parallel and Series
5
4
Parallel Compensation
6
4.1
Technology, theory, and basics
6
4.2
Mechanically switched compensation devices
7
4.3
SVC – Static VAR Compensator
8
4.4
Layout
16
Series Compensation
17
5.1
Technology, theory, and basics
17
5.2
Types
17
5.3
Layout
20
Protection and Control
21
6.1
Hardware for control and protection
21
6.2
Human Machine Interface
21
Converters for FACTS
22
LTT – Light Triggered Thyristors
22
Complete Solutions
23
Contacts, feedback, etc.
24
2.1
5
6
7
7.1
8
Contents
Page
Facts on FACTS – Theory and Applications
2
2
Theme
1. Facts on FACTS – Theory and Applications
1.1 FACTS – What and why?
FACTS is the acronym for Flexible AC
Transmission Systems and refers to a
group of resources used to overcome
certain limitations in the static and
dynamic transmission capacity of
electrical networks.
The IEEE defines FACTS as “alternating
current transmission systems incorporating power-electronics-based and other
static controllers to enhance controllability and power transfer capability.”
The main purpose of these systems is to
supply the network as quickly as possible
with inductive or capacitive reactive power
that is adapted to its particular requirements, while also improving transmission
quality and the efficiency of the power
transmission system.
1.2 FACTS for supplying power –
Now and in the future
The inevitable globalization and liberalization of energy markets associated with
growing deregulation and privatization
are increasingly resulting in bottlenecks,
uncontrolled load flows, instabilities, and
even power transmission failures. Power
supplies are increasingly dependent on
distributed power plants with higher voltage levels, a greater exchange within
meshed systems, and transport to large
load centers over what are often long
distances. This type of power transmission
must be implemented safely and costeffectively with a view to the future.
Implementing new transmission systems
and components is a long-term strategy
for meeting these challenges. Over the
short and medium term, modern transmission technologies can be employed
at comparatively little expense to rectify
or minimize bottlenecks and substantially
improve the quality of supply. Often, this
makes it possible to postpone investing
in new plants and, as a result, to achieve
critical advantages over the competition –
especially important in de-regulated
energy markets in which power supply
companies are subject to extreme pricing
pressure.
FACTS provide
■
fast voltage regulation,
■
increased power transfer over
long AC lines,
■
damping of active power oscillations,
and
■
load flow control in meshed systems,
thereby significantly improving the stability
and performance of existing and future
transmission systems.
This means that with FACTS, power companies will be able to better utilize their
existing transmission networks, substantially increase the availability and reliability
of their line networks, and improve both
dynamic and transient network stability
while ensuring a better quality of supply.
1.3 Tasks of FACTS devices
FACTS systems perform the following tasks:
■
Control voltage under various load
conditions
■
Balance reactive power
(voltage, transmission losses)
■
Increase the stability of power
transmission over long distances
■
Increase active power stability
As a world leader in the power transmission
and distribution industry, Siemens has
developed a number of modern, flexible,
high-capacity FACTS for efficiently and
reliably regulating voltage, impedance,
and phase angle when transmitting power
over high-voltage lines.
Facts on FACTS – Theory and Applications
3
∆V
V2 = V1 – ∆V
∆V
I
X
V1
∆V
V2
V1
V2
V1
I
I
(ind.)
(cap.)
V2
Fig. 2.1: Influence of reactive power flow on system voltage
2. Basics
2.1 Reactive power compensation
Consumer load requires reactive power
that varies continuously and increases
transmission losses while affecting voltage
in the transmission network. To prevent
unacceptably high voltage fluctuations
or the power failures that can result, this
reactive power must be compensated and
kept in balance.
This function has always been performed
by passive elements such as reactors or
capacitors, as well as combinations of the
two, that supply inductive or capacitive
reactive power.
4
Basics
The more quickly and precisely the
reactive power compensation can be
accomplished, the more efficiently
the various transmission characteristics
can be controlled. For this reason, slow
mechanically switched components
have been almost completely replaced
by fast thyristor-switched and thyristorcontrolled components.
2.1.1 Effects of reactive power flow
Reactive power flow has the following
effects:
■
Increase in transmission system losses
– Adding to power plant installations
– Adding to operating costs
■
Major influence on system voltage
deviation
– Degradation of load performance
at undervoltage
– Risk of insulation breakdown
at overvoltage
■
Limitation of power transfer
■
Steady-state and dynamic stability
limits
Type
Short-circuit
level
Transmission
phase angle
Steady-state
voltage
Voltage after
load rejection
Application
nearly
unchanged
slightly
increased
increased
high
voltage
stabilization
at heavy load
nearly
unchanged
slightly
increased
decreased
low
voltage
stabilization
at light load
nearly
unchanged
controlled
controlled
limited
by control
fast voltage
control reactive
power control
damping of
power swings
MSC
MSR
SVC
Static VAR
compensator
Fig. 3.1 shows today’s most common shunt compensation devices, their influence on the most important transmission parameters, and typical applications
3. Parallel and Series
FACTS are divided into two categories,
determined by the way in which they
are connected to the power system.
P
A distinction is made between parallel
compensation (which continues to be
the most common) and series compensation (Fig. 3.2).
U1 δ1
U2 δ2
G~
Fig. 3.2:
The active power/
transmission angle
equation illustrates which
FACTS components
selectively influence
which transmission
parameters
G~
P=
Series
compensation:
FSC, TPSC, TCSC
U1 U2
sin (δ1 – δ2)
X
Parallel
compensation:
SVC
Load-flow
control
Parallel and Series
5
ITCR
[pu]
1.0
0.8
0.6
0.4
ν=1
0.2
ν=3
ν=5
ν=7
0
90°
120°
150°
180°
firing angle of valve
Fig. 4.1: Harmonics typical of a thyristor-controlled reactor
4. Parallel Compensation
4.1 Technology, theory, and basics
4.1.1 Harmonics
Parallel (between a bus bar and ground)
reactive power compensation can be
used to selectively influence important
transmission parameters. Parallel capacitor banks support the voltage under
heavy load conditions. This protection
can increase maximum transmittable
power, regulate the voltage profile,
and prevent voltage instability. Parallel
reactors prevent overvoltages under low
load conditions. The key components of
a parallel reactive power compensation
system are thyristor-switched capacitors
(TSCs) and thyristor-controlled reactors
(TCRs), which can be supplemented with
filter branches as needed.
Harmonics are whole multiples of the
fundamental frequency (50 Hz/60 Hz)
that are superimposed on it. Harmonics
cause the system voltage to deviate
periodically from the sinusoidal shape,
resulting in voltage distortion. Harmonics
are caused by devices with nonsinusoidal
power input, including power converters,
frequency converters, rectifiers and TCRs.
A high harmonic content in the voltage
of an electrical network can result in an
unacceptable temperature rise in electric
machines and a voltage increase in capacitor banks.
6
Parallel Compensation
The 5th, 7th, 11th, and 13th harmonics
are characteristic of TCRs and are especially dominant, but maximum magnitudes decrease very fast with increasing
harmonic numbers. The occurrence and
effect of the intermediate, noncharacteristic harmonics, in contrast, are much
less pronounced. The magnitude and the
occurence of harmonics in a TCR branch
are given in Fig. 4.1.
4.1.2 Filter branches
Filters serve to absorb harmonics.
The number of filter branches and their
resonance tuning frequency depend
on the basic design of the Static VAR
Compensator (SVC) and the harmonic
distortions in the system. Filters can be
tuned either to a single frequency or
to multiple frequencies simultaneously.
High-pass and low-pass filters can also
be used. Filters are connected to the bus
bar via circuit-breakers to absorb their
harmonics where they are generated.
MSC/MSR
Mechanically Switched Capacitors/
Reactors
SVC
Static VAR Compensator
SVC PLUS® (STATCOM)
Static Compensator
Switchgear
Thyristor Valve(s)
IGBT (GTO) Valves
Capacitors
Control & Protection
Control & Protection
Reactors
Transformer
Transformer
Capacitors
DC Capacitors
Reactors
52 ≤ kV ≤ 800
52 ≤ kV ≤ 800
52 ≤ kV ≤ 800
50 ≤ MVAr ≤ 500
50 ≤ MVAr ≤ 800
50 ≤ MVAr ≤ 200
a
b
Further details can be found in separate SVC PLUS® brochure.
Fig. 4.2: Shunt-connected FACTS devices
4.2 Mechanically switched
compensation devices
4.2.1 MSC – Mechanically Switched
Capacitor
Mechanically Switched Capacitors (MSCs)
are a simple and low-speed solution for
voltage control and network stabilization
under heavy load conditions. Their utilization has almost no effect on the shortcircuit level, while it increases the voltage
at the point of connection.
4.2.2 MSR – Mechanically Switched
Reactor
Mechanically Switched Reactors (MSRs)
have exactly the opposite effect, and are
therefore preferable for achieving stabilization under low load conditions.
Key data of systems implemented:
UN ≤ 765 kV
QN ≤ 500 MVAr
Parallel Compensation
7
VHV
HV
U N, f
Restriction
to 150 MVAr
1
CH
LV
2%
2
Capacitive
design point
at 0.95 pu
5%
10%
1.3
pu
1.1
1.0
CL
0.5
R
L
3
1
2
3
4
5
6
Fig. 4.3: Simplified single line
of an MSCDN
As a more highly developed form of
mechanically switched capacitor, the
MSC with an additional damping circuit
provides essentially voltage support without
increasing existing system harmonics.
4.3 SVC – Static VAR Compensator
SVCs are a quick and reliable means of
controlling voltage on transmission lines.
With average response times ranging
from 30 to 40 ms, SVCs are much faster
than conventional mechanically switched
reactors and capacitors (100 to 150 ms)
and can also be used to actively damp
power oscillations.
When system voltage is low, the SVC
generates capacitive reactive power.
When system voltage is high, it absorbs
inductive reactive power.
Parallel Compensation
5
Minimum
operating
voltage
6
Step-down transformer
LV bus bar
Control
Thyristor Controlled Reactor (TCR)
Thyristor Switched Capacitor (TSC)
Fixed Filter Circuit (FC)
–2.0 –1.5
The reactive power is changed by switching on three-phase capacitor and reactor
banks connected to the secondary side
of the transformer. Each capacitor bank
is switched on and off by thyristor valves
(TSC). Reactors can be either switched
(TSR) or controlled (TCR). The main components of an SVC are shown in Fig. 4.4.
Key data of systems implemented:
UN ≤ 765 kV
QN ≤ 500 MVAr
–1.0
–0.5
Cap. Range
Fig. 4.4: The SVC system combines various components as a function
of the individual conditions in the power system to be optimized
4.2.3 MSCDN – Mechanically Switched
Capacitor with Damping Network
8
4
Fig. 4.5: V/I operating diagram of an SVC
(HV side)
4.3.1 Tasks of static compensation
systems
Static compensation systems perform
the following tasks:
■
Stabilize voltage
■
Control dynamic reactive power
■
Improve transient stability
■
Damp active power oscillations
■
Increase power transfer capability
■
Balance system voltages
The design and configuration of an SVC,
including the size of the installation, operating conditions, and losses, depend on
individual circumstances and the tasks
to be performed.
0.0
P
Sr
10%
0.01
5%
2%
Inductive
design point
at 1.02 pu
VBase = 400 kV
IBase = 100 MVA
Continuous
operation
Restricted
operation
0.5
1.0
a
P
= per-unit losses
Sr
0.05
Q
= per-unit reactive
Sr
power of compensator
b
Sr = rated reactive
power of compensator
IHV [pu]
–1.0
–0.8
–0.6
–0.4
–0.2
Cap. Range
Ind. Range
0.0
0.2
Q
Sr
Ind. Range
Fig. 4.6: Comparison of losses as a function of the reactive power output at the SVC
4.3.2 V/I characteristic
4.3.3 Losses
The design of the TCR/TSR and TSC
modules is determined by the desired
current-voltage characteristic of the
SVC. An SVC specification sets limits
for modes of operation on the system
side (Fig. 4.5).
In Fig. 4.6, the compensator losses (P/Sr)
are plotted as a function of compensator
reactive output (Q/Sr) for two different
compensator arrangements. The mean
losses of configuration (a), which consists
of a TCR combined with a Fixed Filter Circuit
TCR + FC
a
(FC), are distinctly higher in important
operating ranges than those of the
configuration with TCR, FC, and TSCs,
represented by curve (b). If compensator
losses in specific operating ranges are
estimated to be high, a TCR/TSC combination may prove more advantageous economically than a TCR/FC combination.
2 TSCs + TCR + 2 FC
b
Parallel Compensation
9
I
I
VC
Vsys
Vsys
Vsys
VC
I90
I
Ifund
Vsys
blocking
α = 90°
switch-in
I120
α = 120°
Fig. 4.7: Voltages and current of a TSC branch during valve conduction
and blocking
Fig. 4.8: Harmonics of voltages and currents of a TCR branch during valve
conduction and blocking (
shows the content of fundamental current
of a control angle of 120°)
4.3.3 Thyristor-switched and thyristorcontrolled devices (Fast VARs)
4.3.3.1 TSC – Thyristor Switched
Capacitor
4.3.3.2 TCR – Thyristor Controlled
Reactor
One of the most common FACTS
components is the parallel static
VAR compensator (SVC).
Due to transient phenomena at switch-on,
TSCs are not continuously controlled but
instead are always switched on and off
individually as required by the system.
Consequently, a TSC cannot inject a reactive current with variable amplitude into
the system, meaning that it supplies
either maximum reactive current or none
at all. Through the precise triggering
of thyristor valves, most of the transient
phenomena at switch-on can be avoided.
TSC branches do not generate harmonic
distortions.
TCRs are used to continuously regulate
the inductive reactive power from zero
to the maximum, depending on the
requirements, by means of current.
Normally, a SVC is a combination of
one or more of the following branches:
■
TSC: Thyristor Switched Capacitor
■
TSR: Thyristor Switched Reactor
■
TCR: Thyristor Controlled Reactor
■
FC: Fixed Filter Circuit
(single-, double- or triple-tuned)
10
Parallel Compensation
They do not generate transients; at the
increased fitting angles (above 90°),
however, they do generate harmonic
currents that must be absorbed by filters.
TCR, FC
TCR, TSC, FC
TCR, TSC
Fig. 4.9: Typical SVC configurations
4.3.3.3 TSR – Thyristor Switched
Reactor
In order to prevent all harmonic currents
when reactors are used, the reactors (like
capacitors) can also serve as switches only,
that is, as TSRs.
4.3.3.4 Configurations of SVCs
Fig. 4.9 shows some typical SVC configurations. The selection of the individual
configuration depends on factors like
investment costs, losses and availability
figures.
A
C
B
SVC
Net 2
Net 1
300 km
300 km
1300 MW
5200 MW
Fig. 4.10:
Block diagram
of the 500-kV
transmission system
Net 3
200 MW
Parallel Compensation
11
Voltage
Voltage
without SVC
with SVC
110
110
%
%
100
100
0
10 s
0
10 s
Fig. 4.11: Temporary overvoltage in System 3 caused by load rejection at A
4.3.4 Applications
The example 4.10 describes some of the
many options available for reactive power
compensation using static compensators.
A 600-km long, 500-kV double-circuit
line interconnects three networks with
a total load of 6700 MW (Fig. 4.10).
The charging power of the line is approximately 1300 MVAr cap.; 45 percent of
this power is compensated by four shunt
reactors of 150 MVAr ind. each.
220 kV
The reactive power of the compensated
line varies in operation by 500 MVAr ind.
The excess reactive power of 700 MVAr
cap. on no-load is reduced to 200 MVAr
cap. with maximum power transmitted.
An SVC with a rating of ± 200 MVAr
is connected at the middle of the transmission line.
For technical and economic reasons,
the line should be operated under varying
conditions at a constant voltage that is
as high as possible. This maximizes the
power that can be transmitted.
300 km
U2
Network
SVC
12
Parallel Compensation
Matching the reactive power necessary
to meet the operating conditions is
carried out by controlling the 500-kV
transformers in Power Systems 1 and 2
at the two ends of the lines. Such regulation is not possible in the middle of
the lines because Power System 3 has
no generating stations. Here, the static
compensator can keep the voltage constant with practically no delay. Sudden
changes in the reactive power – and
thus also the voltage – are caused by
switching operations.
When the double-circuit line between
System 1 and System 3 is switched off, the
voltage rises in System 3 by 10 percent
Un when one circuit is switched
on without the SVC in service. With
the SVC in service, the rise in voltage
is suppressed from a peak of 10 percent
Un to 3 percent Un within only a few
hundredths of a second and subsequently
regulated back to its original value
(Fig. 4.11).
Voltage
Voltage
130
130
without SVC
120
with SVC
120
110
110
100
100
0
10 s
line switched off in C
load rejection
0
10 s
line switched off in C
load rejection
Fig. 4.12: Temporary overvoltage in System 3 upon switching on one circuit of the
double-circuit line System 1 – System 3 at C
A second case addresses the conditions
occurring during load rejection by opening both the circuits at A. The voltage rises
to 133 percent Un without the SVC and,
except for a short peak, rises to only
120 percent Un with the SVC in service.
a
U2
U2N
b
c
d
1.3
1.2
Fig. 4.13 shows the effects on system
voltage at the end of a 220-kV line operating at full load (a), at partial load (b),
when a line segment fails at full load (c),
and when there is a load rejection at the
end of the line, with and without an SVC
(d).
1.1
1.0
0.9
0.8
Fig. 4.13:
Voltage ratios with/
without SVC under different
operating conditions
a
b
c
d
full load
off-peak load
failure of a line section (full load)
load rejection at line end
without compensator
with compensator
Parallel Compensation
13
P/MW
200
capacitive
Voltage
control
POD
control
Voltage
control
500
POD
control
QSVC/
MVAr
without
SVC
2
4
6
8
10 s
250
200
inductive
0
2
4
6
8
10
b) SVC output reactive power
a) Active power oscillation on OHTL
Fig. 4.14: Influence of the SVC with different control strategies
Siemens implemented an SVC system
whose primary task was to damp power
oscillations resulting from a system fault
followed by switching off the faulted
line section. Fig. 4.14 shows the performance curve, which is clearly stabilized following the installation of two
SVCs, each with a control range from
+150 MVAr (capacitive) to –75 MVAr
(inductive).
Additional to voltage control, POD
(power oscillation damping) control
is implemented.
High
Medium
Low
Permissible losses
TCR/FC
TCR/TS
Comb.
MSR/MSC
Dynamic
control range
TCR/FC
TCR/TSC
TCR/TSC
MSR/MSC
Comb.
MSR/MSC
Permissible
harmonic
distortion limits
TCR/FC
TCR/TSC
TCR/FC
TCR/TSC
MSR/MSC
14
Parallel Compensation
Summary
SVCs can be used to perform a wide
range of compensation tasks in large
transmission systems. Requirements
vary greatly and are sometimes contradictory. The control system can be
designed so that priorities can be flexibly
assigned to one task or another, depending on current conditions in the power
system.
Fig. 4.15:
Selecting the SVC
ILINE
FPOD
POD
evaluation
POD
controller
Limit
and initial
value FAMref
EPOD
Slope
+
VHV~
IHV~
SVC ON/OFF
VACT
System voltage
evaluation
+
∆Q
–
+
+
QSVC
evaluation
Qref
+
∆Q
QSVC
–
Q
controller
EQ
Kp
+
SVC ON/OFF
controller
BSVC
∆B
+
Vref
VHV
evaluation
VHV
Gain
controller
Gain
selector
Stability
controller
Normal/
Emergency mode
Fig. 4.16: Control structure of an SVC (contains POD, voltage control and reactive power control)
4.3.5 Selecting the SVC configuration
4.3.6 Control engineering (software)
Which SCV configuration will be chosen
depends on the application. Please see
Fig. 4.15 for details.
Siemens offers coordinated software
solutions tested in numerous applications
for the control of:
■
System voltage
■
System voltage balancing
■
SVC reactive power
■
Power oscillation damping (POD)
■
Gain of the controller for optimal
reponse times at various system
configurations
Parallel Compensation
15
10
9
1
2
2
3
4
5
6
7
8
4
9
11
10
11
12
5
SVC transformer
TCR reactors
TSC capacitors
TSC reactors
Filter capacitors
Filter reactors
Circuit-breaker
Arrester
Bushings
Valve and control building
Valve cooling
Transformer cooling
6
3
7
8
1
12
Fig. 4.16: A typical SVC layout
4.4 Layout
Typical SVC Layout
1x TCR, 1x filter, 1x TSC
Fig. 4.17:
SVC Bom Jesus da Lapa
16
Parallel Compensation
C1, C2 …
Series capacitor segments
MOV1, MOV2 …
ZnO Overvoltage protection
C1
D1, D2 …
Damping circuit
C2
SG1, SG2 …
Spark gap
MOV1
MOV2
D1
D2
SG1
SG2
CB1
CB2
CB1, CB2 …
Bypass circuit-breaker
Fig. 5.1: Main components and configuration of a Fixed Series Capacitor (FSC) with two segments
5. Series Compensation
5.1 Technology, theory, and basics
The transmission of active power is mainly
limited by the impedance of the transmission line, comprising the ohmic resistance
plus the capacitive and inductive reactance.
Tasks of series compensation
Series compensation provides the
following benefits:
■
Reduces line voltage drops
■
Limits load-dependent voltage drops
■
Influences load flow in parallel
transmission lines
■
Increases transfer capability
■
Reduces transmission angle
■
Increases system stability
For these tasks, Siemens offers various
solutions that have already been proven
in numerous applications.
5.2 Types
5.2.1 FSC – Fixed Series Capacitor
The simplest and most cost-effective
type of series compensation is provided
by Fixed Series Capacitors (FSCs).
Three high-voltage switches serve to
integrate the FSC into and isolate it from
the transmission line (e.g., for maintenance purposes).
Key data of systems implemented:
UN ≤ 765 kV
QN ≤ 800 MVAr
FSCs comprise the actual capacitor banks
and parallel arresters (Metal Oxide Varistors,
MOVs), spark gaps, and a bypass switch.
The surge arresters protect the capacitor
from overvoltages during and after transmission system failures. The spark gap
protects the arrester against excessive
energy absorption; the bypass switch,
in turn, protects the spark gap.
Series Compensation
17
7
8
7
1
2
3
1
4
5
6
4
7
8
Series capacitor
Thyristor valve as
fast bypass device
Current limiting
reactor
MOV
Bypass circuit-breaker
Bypass damping reactor
Platform disconnects
with grounding switch
Bypass disconnect
3
2
6
Platform
5
Fig. 5.2: Main components and configuration of a TPSC installation
5.2.2 TPSC – Thyristor Protected
Series Capacitor
When direct light triggered thyristors are
used, there is no need to install conventional spark gaps or surge arresters. Due
to the very short cooling times of the
Light Triggered Thyristor valves, thyristorprotected series capacitors can be quickly
returned to service after a failure, allowing the transmission lines to be utilized
to their maximum capacity.
Fig. 5.3 shows the sequence of events
for a thyristor-protected series capacitor
(TPSC) when a fault occurs in the line
segment in which the series capacitor
is operated. Whereas capacitor banks
protected by conventional means often
require several hours to cool after full
energy absorption – and, consequently,
until restart – the TPSC is fully operational within a fraction of this time.
18
Series Compensation
With TPSCs, network operators can
return to maximum power transmission
faster and reduce the follow-up costs
that were previously unavoidable.
TPSCs are the first choice whenever
transmission lines must be returned to
maximum carrying capacity as quickly
as possible after a failure.
Key data of systems implemented:
UN ≤ 500 kV
QN ≤ 401 MVAr
5.2.3 TCSC – Thyristor Controlled
Series Capacitor
Reactive power compensation by means
of thyristor-controlled series capacitors
(TCSCs) can be adapted to a wide range
of operating conditions. It is also possi-
ble to control the current and thus the
load flow in parallel transmission lines,
which simultaneously improves system
stability. Further applications for TCSCs
include load oscillation damping and the
mitigation of Subsynchronous Resonance
(SSR).
The equivalent circuit diagram in Fig. 5.4
shows the basic configuration, comprising a capacitor and a parallel thyristorswitched reactor.
Fig. 5.5 shows the operating range of a
TCSC. By variation of the firing angle alfa,
the effective impedance of a TCSC can be
varied. With alfa = 180°, the TCSC impedance equals the capacitor impedance,
at about 148°, it is three times the capacitor impedance. With firing at alfa = 90°
and higher, the TCSC provides an inductive impedance.
212 °C
TPSC valve
temperature
60 s after the 1st fault,
the valve temperature
rise is 2.2 K
50 °C
0.5
0.7
0.9
1.1
1.3
1.5
time/s
Thyristor
valve
Thyristor valve
bypass CB
Line
breaker
5 cycles
time to auto-reclosure
Fig. 5.3: Sequence of events in a TPSC installation when internal system faults occur
Advantages of the TCSC
The TCSC offers the following advantages
over conventional fixed series compensation:
■
Usable for load-flow control
■
Power Oscillation Damping (POD)
■
Higher degree of compensation
■
Better capacitor protection thanks
to thyristors
■
Replacement of the spark gap
C
TCR
CB
Fig. 5.4:
TCSC
These advantages apply not only to
brand-new installations but can also
be implemented in existing systems.
lzl
Operating
range
Key data of systems implemented:
UN ≤ 500 kV
QN ≤ 200 MVAr
Fig. 5.5:
Operating
range of a
TCSC
ind.
90° Control angle
cap.
180°
Series Compensation
19
Fig. 5.5: An aerial view of the TCSC PingGuo
5.3 Layout
TCSC PingGuo,
State Power Southern Company,
China
500 kV
350 MVAr (FSC)/55 MVAr (TCR)
20
Series Compensation
Fig. 5.6: Standard SIMATIC TDC control
and protection system
Fig. 5.7: All controls are fully tested with
a real-time digital simulator
6. Protection and Control
6.1 Hardware for control
and protection
Siemens offers the latest in control and
protection for FACTS – the tried and tested
SIMATIC TDC (Technology and Drive
Control) automation system. SIMATIC TDC
is used worldwide in almost every industry
and has been proven in both production
and process engineering as well as in
numerous HVDC and FACTS applications.
Operating personnel and project planning engineers work exclusively with
a standardized, universal hardware and
software platform, enabling them to
perform demanding tasks more rapidly.
One of the main considerations in developing this automation system was to
ensure the highest degree of availability
of the FACTS – which is why all control
and protection systems as well as the
communication links are configured
redundantly (if requested by the customer).
The new instrumentation and control
technology also permits the use of a highperformance fault recorder operating at
a 25 kHz sampling rate. This reduces the
period of time between fault recording
and the printout of the fault report from
several minutes (previously) to 10 seconds
(now).
To further improve redundancy management, special modules were developed that
supplement the standard SIMATIC TDC
automation system. Another new module
in the instrumentation and control cabinet
is responsible for issuing triggering signals
to the thyristor valves.
Altogether, SIMATIC TDC with its high
integration density takes up significantly
less space in the plant than the previous
technology.
Nevertheless, use of SIMATIC TDC is not
limited to new FACTS. With its flexible interface design, it can easily replace existing systems. In this case, the measured
values of existing plants are integrated in
and further processed by the new control
system. Because it requires so little space,
the new technology can even be configured in parallel with the existing C & P
system in order to integrate the FACTS
with as little delay as possible.
6.2 Human Machine Interface
The interface between the operator and
the plant (HMI = Human Machine Interface) is the standardized SIMATIC WinCC
visualization system, which further simplifies operation and facilitates the adaptation of graphical user interfaces to the
operator’s requirements.
Protection and Control
21
Fig. 7.1: Easily assembled direct light triggered thyristors (left) have prevailed over
electrically triggered models (ETT, right), especially in high-voltage thyristor valves
Fig. 7.2: Thyristor valve with wafer integrated
overvoltage protection
7. Converters for FACTS
7.1 LTT – Light Triggered Thyristors
Thyristors are a key element in controlling
(switching on and off) the passive components in reactive power compensation
systems (Fig. 7.1).
The system of direct light triggering
developed by Siemens activates the
thyristors with a pulse of light that lasts
for 10 microseconds and has a peak power
of 40 milliwatts. The device also incorporates overvoltage protection, so that it
is self-protecting if the forward voltage
exceeds the maximum permitted limit.
The light pulse is carried by fiber optics
at ground potential directly from the
valve control to the thyristor gate.
22
Converters for FACTS
Conventional high-voltage thyristor valve
technology uses electrically triggered
thyristors, which need a pulse with a
peak power of several watts. This pulse
is generated by complex electronic equipment placed alongside each thyristor.
In turn, this electronic equipment, which
needs an auxiliary power supply, is
activated at ground potential by optical
signals from the valve control. Substituting
direct light triggering for this electronic
equipment reduces the number of electrical and electronic components in the
thyristor valve – and, consequently,
the possibility of failure – by around
80 percent. This improves reliability and
eliminates problems associated with
electromagnetic compatibility. The other
important fact about the new thyristor
technology is that long-term availability
of electronic components for replacement
purposes over a period of at least 30 years
is no longer a problem.
Thyristor valves (Fig. 7.2) from Siemens
are assembled from 4-inch or 5-inch
thyristors, depending on the currentcarrying capacity/rated current required.
Thyristor technology has been under
constant development since the early
1960s. At the present time, thyristors can
safely and economically handle blocking
voltages of up to 8 kilovolts and rated
currents of up to 4,200 amperes.
Fig. 8.1: SVC TCR reactors
8. Complete Solutions
Complete solutions and services
from a single source
The goal of modern power quality management is to provide stable, distortion-free
voltage in a reliable manner. To this end,
Siemens provides a single source for all
the necessary FACTS equipment and a
comprehensive range of complementary
services (Fig. 8.2), including basic system
design, modeling, network analyses, civil
works, project management, functional
performance tests, delivery, and installation, as well as commissioning, on-site
tests, and training of operating personnel.
Siemens analyzes and calculates the
power system requirements, develops
customized solution concepts for complete system configurations and plants,
and quickly implements them as turnkey
systems. The delivery time for a typical
SVC plant is from 12 to 14 months;
FSC systems are ready to go in 10 to
12 months.
FACTS
system
design
Identification
of project
Fig. 8.2:
Complete turnkey
solutions and
corresponding services
from a single source
Customer
training
System
analysis
Component
supply
Civil
works
Installation
&
commissioning
Siemens
Project
management
Complete Solutions
23
Published by and copyright © 2010:
Siemens AG
Energy Sector
Freyeslebenstrasse 1
91058 Erlangen, Germany
Siemens AG
Energy Sector
Power Transmission Division
Power Transmission Solutions
Freyeslebenstrasse 1
91058 Erlangen, Germany
www.siemens.com/energy/facts
For more information, please contact
our Customer Support Center.
Phone: +49 180/524 70 00
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+49 180/524 24 71
(Charges depending on provider)
E-mail: [email protected]
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are the property of Siemens AG, its affiliates,
or their respective owners.
Subject to change without prior notice.
The information in this document contains general
descriptions of the technical options available, which
may not apply in all cases. The required technical
options should therefore be specified in the contract.
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