Transcript ps3-presentation

Study Committee B5 Colloquium
2005 September 14 – 16
Calgary, CANADA
Preferential Subject #3
Protection and Control of
Series Compensated Networks
SUMMARY
Special Reporter: Graeme Topham
South Africa
SUMMARY
 STUDIES
 SIMULATION
 DATA
Q1: Main utility considerations when deciding to
series compensate a transmission line and/or
what are the challenges faced?
 JP: Design considerations 275 kV double circuit SC line:
 Simulation study:
Degree of compensation vs. Stable transmission
capacity
 Special directional scheme for backup
 Large scale field tests
 GS: Introducing SC more economical than additional line
 CA: Must be careful in choice of relays. Tests important
 CA: SC reduces influence of Geo-magnetic induced
currents
Q2: What economic and/or environmental
issues deter the implementation of
series compensation?
 SE: Environmental issues can influence
preferred location of SC
Q3: Experiences of other unique SC distance
relay applications where special adjustments
to settings and/or logic are required?
 BR: Extensive simulation tests -> necessity to
refine logic and/or settings
At lower voltages tests expensive -> tools
needed
 CN: Deviation of power frequency component
relay. Zero sequence source impedance
artificially decreased. Adaptive functionality.
 JP: Special directional scheme. Based on
memory function -> operating time delay for V
inversion. Three directional distance elements
required for SC double-circuit lines. Numerical
technology allowed simplification.
Q3: Experiences of other unique SC distance
relay applications where special adjustments
to settings and/or logic are required?
 SE: Distance relay model – basis for problems for
dealing with SC
 UK:
 Special setting when accurate V measurement
unavailable
 Special polarizing V for direction decision
 Cross differential relay proposed as better
solution for double circuit lines
 Weak infeed not a problem
 New capacitor voltage calculation technique
Q3: Experiences of other unique SC distance
relay applications where special adjustments
to settings and/or logic are required?
 US: Formula based on gap voltage to come to a
security factor for setting Z1
 CA: Current diff relay better than distance relay
 SE: Margin for Z1 dependent on compensation
degree
Q4: What analysis tools are available to utilities to
assist in evaluating distance relay performance
on SC applications prior to the purchase or
choice of a particular relay type?
 BR: Use of RSim tool to ‘assemble’ a virtual relay.
Good results for relays where enough info available.
Cooperation between manufacturers and users
 SE: SS simulations (PSSE / CAPE) not suitable
EMTP - insufficient relay details
Only viable option is simulator tests
 US: Tools – relay manual; test report; test data base
(COMTRADE files); simulation
 US: Real-time simulation - system specific and must
be accurately
 CA: HyperSim
Q4: What analysis tools are available to utilities to
assist in evaluating distance relay performance
on SC applications prior to the purchase or
choice of a particular relay type?
 CN: Digital model for development. Physical models
for testing
 CA: Relay model info will allow users to see margin ->
added security
 US: DLL file for EMPT testing
Q5: Besides zero sequence current compensation,
what other techniques have been successfully
applied to distance relays to resolve the impedance
measurement inaccuracy on SC parallel lines?
 US: Supervise impedance measurement with
superimposed direction function
 SE: China – 4 x 500 kV systems on same
tower. Grounding switches?
Q6: What are the current experiences with using
the weak infeed protection function,
particularly in SC line protection applications?
 BR: Many problems with weak infeed
function. How to determine temporary weak
infeed terminals during long duration major
disturbance and restoration? 2006 Session?
 CA: Agree weak infeed trip insecure
Recommendation to separate WI from
permissive trip Echo function in POTT
schemes
Q6: What are the current experiences with using
the weak infeed protection function,
particularly in SC line protection applications?
 SE: WI important feature. Must consider
all necessary precautions to prevent unwanted
operations
Q7: What are the main technical difficulties with
accurate fault location on SC lines and what fault
location techniques are currently being
successfully employed?
 JP: Experience with one- and two-terminal
methods. Latter better than differential
equation based algorithm.
 SE: Impedance method inaccurate especially
when compensation degree switched.
Travelling wave method found to be most
accurate
Q8 a): What methodologies are used to
optimize settings for series compensated
line applications?
 SE: Real-time simulations to verify total
protection scheme
 SE: Thyristor controlled capacitor needs to be
correctly simulated when testing line protection
Q8 b): What are the requirements of utilities in
terms of certification tests for relays and/or
protection systems before applying
these to SC lines?
 AU: Distance relay problems
Transient fault studies essential
Automatic test tool very useful
 BR: Real-time digital simulation to verify
behavior and performance of relays. Also
used to optimize settings.
 US: High quality records to verify models
Q9: What are utility experiences with nondistance protection applications on series
compensated transmission lines?
 JP: FM current differential as main protection
with directional distance as back-up
Q10: What are the advantages, disadvantages,
technical challenges and cost implications of using
non-distance protection when compared to using
distance protection on SC applications?
 JP: Advantages of using current-based relay
as main protection
Operating time of back-up distance well coordinated
270 line faults cleared by Main. Backup not
involved and no misoperations
Q10: What are the advantages, disadvantages,
technical challenges and cost implications of using
non-distance protection when compared to using
distance protection on SC applications?
 UK: High charging current possible problem
for current diff. Cross differential relay
proposed option for double circuit lines.
Examples of new relay principles being
researched – surge impedance, noise
generated protection and boundary protection
techniques
Importance of dynamic tests and international
research and development collaboration
Q10: What are the advantages, disadvantages,
technical challenges and cost implications of using
non-distance protection when compared to using
distance protection on SC applications?
 US: Comparison of distance protection (with
and without comms) and directional
comparison and importance of performance
and cost assessment
 SE: Charging current compensation no longer
a problem. Trend towards current differential.
Q11 a): What are the current experiences with autoreclosing on series compensated transmission lines?
Q11 b): What are the technical challenges and
proposed solutions?
 SE: Duty cycles for thyristor controlled
capacitor bank elements outlined.
Challenge relating to multi-pole tripping and
sequential reclosing.
 SE: Good experience with ARC (3-pole
tripping) even on TCSC
Q12: Have there been any problematic
protection issues relating to the use of UPFCs
experienced by other utilities and what
solutions are available?
 BR: No UPFCs, but TCSCs successfully
applied – No particular problems. Line
protection set according to worst conditions
Q13: What other novel theoretical tools are
available to assist in the analysis and
understanding of SC networks?
 SE: Practical results of complex subject of
informational analysis in Russia
Q14: What influences of shunt capacitor banks
on protection measurement are reported and
how are the effects mitigated?
 CH: Large impact on the circulating currents
and transient behaviour during line faults
under weak infeed conditions.
Close-to-zero V faults make direction
determination difficult
More than 1 polarization signal for direction
decision recommended
PS-3
Concluding Comments
 Evidence of continued valuable work being
done to improve the performance of the
protection, control and monitoring of series
compensated networks
 New challenges in protecting series
compensated and adjacent transmission lines
are emerging and innovative techniques to
deal with such challenges and also to enhance
equipment performance continue to be
developed
PS-3
Concluding Comments
 Encouraging to see the high level of cooperation between manufacturers and utilities
(evident from the number of joint papers) to
solving application problems and also to
improve protection equipment
 It is also apparent that a thorough
understanding of the subject is advantageous
in order to ensure optimal use of the correct
equipment for particular applications
PS-3
Concluding Comments
 The importance and value added by
collaboration through international bodies and
working groups should not be underestimated