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transcript
Transient Recovery Voltages (TRVs)for High-Voltage Circuit Breakers
Part 1
Denis DufournetChair CIGRE WG A3.28 & IEEE WG C37.011, Fellow IEEE
San Antonio (USA), 19/09/2013
GRID
TRV HV Circuit Breakers P 2
Page
• Introduction & General Considerations 4 &13• Capacitive Current Switching TRV 29• Types of Fault TRVs 45• TRV Modification 63• Terminal Fault TRV 72
− First-pole-to-clear factor 73− TRV rating & testing 88− TRV & arcing times 120− TRV for generator circuit breakers 138
• Short-Line Fault TRV 148• ITRV (Initial TRV) 187
Content (1/3)
TRV HV Circuit Breakers P 3
Page
• Out-of-Phase TRV 194• Three-Phase Line Faults TRV 199• Shunt Reactor Switching TRV 217• Transformer Limited Fault TRV 229• Series Reactor Limited Fault TRV 264• Influence of Series Capacitors on TRV 271• Harmonization of TRVs in IEC & IEEE 282
Content (2/3)
TRV HV Circuit Breakers P 4
Page
• Annexes 306− A: First-pole-to-clear factor 307− B: Second-pole-to-clear factor 316− C: Complement on line faults 321− D: Equivalent circuit for 3-phase to ground fault 326− E: Test circuit for kpp = 1.3 329− F: Bibliography 333
Content (3/3)
Introduction
GRID
TRV HV Circuit Breakers P 6
• The TRV is a decisive parameter that limits the interrupting capabilityof a circuit breaker.
• The interrupting capability of a circuit breaker was found to be stronglydependent on TRV in the 1950’s.
• When developing interrupting chambers, manufacturers must verifyand prove the TRV withstand specified in the standards for differenttest duties.
• Users must specify TRVs in accordance with their applications.
• Type tests in high-power laboratories must be performed inaccordance with international standards, in particular with rated valuesof TRVs.
Importance of TRV
TRV HV Circuit Breakers P 7
1993-1996: CIGRE-CIRED WG CC03 “Medium Voltages TRVs“
1994-1998: IEC SC17A WG21 “Revision Circuit Breaker Standard”
1997-2002: IEC SC17A WG23 “Harmonization TRVs Circuit Breakers ≥ 100kV”
2002-2006: IEC SC17A WG35 “”Revision TRVs Circuit Breakers < 100kV”
2001-2009: IEEE C37-04 & 06 ”Harmonization TRVs Circuit Breakers”
2002-2005: IEEE C37-011 “Revision Application Guide HV Circuit Breakers”
2004-2008: CIGRE WG A3-19 ”Implications of Three-phase Line Faults”
2007-2009: CIGRE WG A3-22 ”Technical Requirements for UHV Equipment”
2009-2011: IEC SC17A MT36 TF ”Introduction UHV TRVs in IEC 62271-100”
2008-2011: IEEE C37-011 ”Revision Application Guide HV Circuit Breakers”
2011-2013: CIGRE WG A3-28 ”Switching Phenomena for UHV & EHV Equipment”
“Recent” TRV Studies in International Bodies
• TRV Studies by International Working Groups
TRV HV Circuit Breakers P 8
• A.Greenwood, Electrical Transients in Power Systems. (book) 2nd
edition, John Wiley & Sons (1991).
• R.Alexander, D.Dufournet, IEEE Tutorial on TRVs (2003-05) http://www.ewh.ieee.org/soc/pes/switchgear/presentations/trvtutorial/TutorialTRVAlexander-Dufournet.pdf
• D.Dufournet, TRVs for High-Voltage Circuit Breakers, Presentation at IEEE Switchgear Committee meeting in Calgary (2008-10)http://www.ewh.ieee.org/soc/pes/switchgear/presentations/2008cbtutorial/Part4_IEEETutorialonTRVHVCircuitBreakers-Dufournet.pdf
• CIGRE Technical Brochure N°134, Transient Recovery Voltages in Medium Voltage Networks (1998-12)
• CIGRE Technical Brochure N°408, Line fault phenomena and theirimplications for 3-phase short and long-line fault clearing, (2010-02)
Main References
TRV HV Circuit Breakers P 9
• A.Janssen, D.Dufournet, “Travelling Waves at Line Fault Clearing and Other Transient Phenomena”, CIGRE Session 2010, Paper A3-102.
• CIGRE Technical Brochure 456, “Background of TechnicalSpecifications for Substation Equipment Exceeding 800kV AC”, byCIGRE WG A3-22 (2011-04).
• D.Dufournet, A.Janssen, “Transformer Limited fault TRV”, Tutorial atIEEE Switchgear Committee Meeting in San Diego (2012-10)
Main References
• Denis Dufournet, Joanne (Jingxuan) Hu, High-Voltage CircuitBreakers Seminar Part 2 Transient Recovery Voltages, University ofManitoba, Winnipeg (2012-06)
TRV HV Circuit Breakers P 10
• IEC 62271-100, High-Voltage Circuit-Breakers (2012-09)• IEC 62271-101, Synthetic testing (2012-10)• IEC 62271-110, Inductive load switching (2012-09)• IEC 62271-306, Guide to IEC 62271-100, 62271-1 .. (2012-12)• ANSI/IEEE C37.04, 04a, 04b, IEEE Standard Rating Structure for AC
High-Voltage Circuit Breakers.• IEEE Std C37.06-2009, Draft AC High-Voltage Circuit Breakers Rated on
a Symmetrical Current Basis-Preferred Ratings and Related Required Capabilities
• IEEE Std C37.09, 09b-2010, IEEE Standard Test Procedure for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis.
• IEEE C37.011, Application Guide for TRV for AC High-Voltage Circuit Breakers” (2011).
• IEEE C37.013, IEEE Standard for AC High-Voltage Generator Circuit Breakers Rated on a Symmetrical Current Basis.
Standards & Guides
TRV HV Circuit Breakers P 11
• In the second edition of IEC 56 published in 1954, the TRV, defined as"restriking voltage”, was of single frequency.
The amplitude factor (or crest value) and the TRV frequency (related tothe rate-of-rise) were not specified but had to be evaluated during thetests.
• In the third edition of IEC 56, published in 1971, IEC introduced for thefirst time the term “TRV” and its representation by two or fourparameters. The short-line-fault tests were also introduced in thisedition.
• TRVs requirements were also introduced in 1971 in ANSI C37.072-1971 (IEEE Std. 327), with TRV ratings in C37.0722-1971 and TRVApplication Guide C37.0721-1971 (IEEE Std. 328).
Historical Perspective
TRV HV Circuit Breakers P 12
• In the fourth edition of IEC 56, published in 1987, a first-pole-to-clearfactor of 1.3 is the only factor specified for rated voltages ≥ 245 kV.
− the rate of rise of recovery voltage (RRRV) is doubled to 2.0 kV/µsfor terminal fault test duty T100.
− ITRV is introduced for rated voltages ≥ 100 kV.
• ITRV is introduced in ANSI C37.04 and C37.09 in 1991 (amendments04i and 09g).
• ANSI C37-06 (1997) harmonize partly TRV parameters with those inIEC (e.g. RRRV = 2.0 kV/µs for T100).
• As in IEC, line surge impedance is 450 Ω for all rated voltages inANSI/IEEE C37.04-1999 (instead of 450 Ω for Ur ≤ 242 kV and 360 Ωfor Ur ≥ 362 kV).
Historical Perspective
TRV HV Circuit Breakers P 13
• Further Harmonization of TRVs between IEC and IEEE leadto
− Amendments 1 and 2 of IEC 62271-100 (respectively in 2002 and2006)
− Amendments of IEEE C37.04b (2008), IEEE C37.06 (2009) andIEEE C37.09b (2010).
Harmonization of IEC and IEEE standards for high-voltage circuitbreakers is presented in detail in a specific chapter.
Historical Perspective
General considerations on Transient Recovery Voltages
GRID
TRV HV Circuit Breakers P 15
Xs
U
A B
Recoveryvoltage
• The recovery voltage is the voltage which appears across theterminals of a pole of circuit breaker after current interruption.
CURRENT
TRANSIENT RECOVERYVOLTAGE
RECOVERY VOLTAGE
General Considerations
TRV HV Circuit Breakers P 16
• Current Interruption Process in SF6 Circuit Breakers
Two contacts areseparated in eachinterrupting chamber.An arc is generated, it iscooled and extinguishedwhen current passesthrough zero.
General Considerations
Simulation arc interruption
TRV HV Circuit Breakers P 17
TRV
TRV (kV)I (A)
• During the interruption process, the arc loses rapidly its conductivity asthe instantaneous current approaches zero.
• During the first microseconds after current zero, the TRV withstand isfunction of the energy balance in the arc: it is the thermal phase ofinterruption.
Gas circuit breakers:Within a few microsecondsafter current zero, arcresistance (RARC) rises toone million ohm in a fewmicroseconds and currentstops flowing in the circuit.
General Considerations
Interruption when current passes through zero
TRV HV Circuit Breakers P 18
• Later, the voltage withstand is function of the dielectric withstandbetween contacts: it is the dielectric phase of interruption.
• During type tests, standards require that the recovery voltage isapplied during 300 ms after current interruption.
General Considerations
The breaking operation is successful if the circuit breaker is able towithstand the TRV and the power frequency recovery voltage.
The TRV is the difference between the voltages on the source sideand on the load side of the circuit breaker.
TRV HV Circuit Breakers P 19
• The nature of the TRV is dependent on the circuit being interrupted,whether primarily resistive, capacitive or inductive, (or somecombination).
• When interrupting a fault at the circuit breaker terminal (terminal fault)in an inductive circuit, the supply voltage at current zero is maximum.
The circuit breaker interrupts at current zero (at a time when the powerinput is minimum) the voltage on the supply side terminal meets thesupply voltage in a transient process called the TRV.
TRV frequency is
with L = short-circuit inductance
C = supply capacitance.
CL21
General Considerations
Fault
TRV HV Circuit Breakers P 20
Current and TRV waveforms during interruption of inductive current
CURRENT
TRANSIENT RECOVERYVOLTAGE
Supply voltage
General Considerations
TRV during inductive current breaking
Note: voltage polarity not respected on Figure
TRV HV Circuit Breakers P 21
TRV and recovery voltage in resistive, inductive and capacitive circuits
-2
-1,5
-1
-0,5
0
0,5
1
1,5
2
2,5
0 0,005 0,01 0,015 0,02 0,025 0,03 0,035
RESISTIVE CIRCUIT
INDUCTIVE CIRCUIT (with stray capacitance)
CAPACITIVE CIRCUIT
General Considerations
TRV HV Circuit Breakers P 22
• Combination of the former basic cases are possible, for example theTRV for mainly active load current breaking is a combination of TRVsassociated with inductive and resistive circuits.
• They are specified for high-voltage switches only as circuit-breakersare able to interrupt with more severe TRVs (in inductive circuits).
General Considerations
TRV HV Circuit Breakers P 23
• Fault interruptions are often considered to produce the most onerousTRVs. Shunt reactor switching is one of the exceptions.
• TRVs can be oscillatory, triangular, or exponential and can occur as acombination of these forms.
• The highest peak TRVs are met during capacitive current and out-of-phase current interruption,
• TRVs associated with the highest short-circuit current are obtainedduring terminal fault and short-line-fault interruption.
• In general, a network can be reduced to a simple parallel RLC circuitfor TRV calculations.
This representation is valid for a short-time period until voltagereflections return from remote buses (see IEEE C37.011-2011)
General Considerations
TRV HV Circuit Breakers P 24
R C
(Vcb)
L
Real network Equivalent circuit
N Lines, each with surge impedance
clZ
NZR
L: source inductance, lines exceptedC: source capacitance, lines excepted
General Considerations
TRV HV Circuit Breakers P 25
− The TRV in the parallel RLC circuit is oscillatory (under-damped) if
− The TRV in the parallel RLC circuit is exponential (over-damped) if
CLR /21
CLR /21
R C
(Vcb)
L
General Considerations
TRV HV Circuit Breakers P 26
0
0,2
0,4
0,6
0,8
1
1,2
1,4
1,6
1,8
2
0 1 2 3 4 5 6 7 8 9
TRV (p.u.)
R / (L / C)0.5 = 10
4
2
1
0.75
0,5
0,3
t / RC
General Considerations
Damping of the oscillatory TRV is provided by R, as R is in parallel to L and C (parallel damping) the damping increases when the resistance decreases (the TRV peak increases when R increases).
t/RC
TRV HV Circuit Breakers P 27
• Reflection from end of lines
When longer time frames areconsidered, typically several hundredsof micro-seconds, reflections on linesmust be considered.
0
100
200
300
400
500
600
700
800
900
0 100 200 300 400 500 600 700 800 900 1000
TIME (µs)
VOLTAGE (kV)
SYSTEM TRVTRV CAPABILITY FOR A STANDARD BREAKER
REFLECTED WAVE
Lines or cables must then be treated as components with distributed elements on which voltage waves travel after current interruption.
These traveling waves are reflected and refracted when reaching an open circuit or a discontinuity.
General Considerations
TRV HV Circuit Breakers P 28
• The most severe TRV occurs across the first pole to clear of a circuitbreaker when it interrupts a three-phase terminal fault with asymmetrical current and when the system voltage is maximum (seesection on Terminal fault).
(arc resistance changes from zero to an infinite value at currentzero).
General Considerations
• By definition, all TRV values defined in the standards are inherent,i.e. the values that would be obtained during interruption by an idealcircuit breaker without arc voltage.
Capacitive Current Switching TRV & Recovery Voltage
GRID
TRV HV Circuit Breakers P 30
-1,5
-1
-0,5
0
0,5
1
1,5
2
2,5
0,005 0,01 0,015 0,02 0,025 0,03 0,035
Recovery voltage
Supply voltage
Load voltage
U (p.u.)
Time (s)
current interruption
Example of a single phase interruption at
50 Hz
Capacitive current interruption: recovery voltage has a (1 – cos) waveshape
Capacitive Current Switching
TRV HV Circuit Breakers P 31
Capacitive Current Switching
Supply-side voltage
Load-side voltage
Recovery voltage
Current
Current interruptionContact separation
Restrike
Final current interruption
TRV HV Circuit Breakers P 32
-1,5
-1
-0,5
0
0,5
1
1,5
2
2,5
3
3,5
0,005 0,01 0,015 0,02 0,025
Recovery voltage
U (p.u.)
Time (s)
instant of current interruption
Reignition Restrike
Overvoltage 3 p.u.
no overvoltage overvoltage
2 p.u.
2 p.u.
Capacitive Current Switching
TRV HV Circuit Breakers P 33
• Two cases can be distinguished, depending on when the restrike happens:
− When it is less than 1/4 of a cycle after current interruption: it is called a reignition,
no overvoltage is produced on the circuit during the transient period when the load voltage tend to reach the supply voltage.
− When it is more than 1/4 of a cycle after current interruption, it is called a restrike,
there is an overvoltage on the circuit during the transient period following the restrike.
Capacitive Current Switching
TRV HV Circuit Breakers P 34
"1-Cos" Waveshape
• Special case of series capacitor switching by by-pass switches
− By-pass switches must be able to withstand the reinsertion voltage without restrike during the transfer of reinsertion current.
TRV HV Circuit Breakers P 35
− Several transient reinsertion voltagewaveshapes can be obtained in service.
− The reinsertion voltage waveshape should be determined bysystems studies.
− For standardization purposes, and in order to cover the greatestnumber of practical cases, IEC 62271-109 recommends a "1-cos"waveshape having a preferred first time-to-peak of 5,6 ms.
− A restrike happens if there is a resumption of current 2.8 ms orlater after the initial current interruption.
"1-Cos" Waveshape
• Special case of series capacitor switching by by-pass switches
TRV HV Circuit Breakers P 36
Circuit with capacitive and inductivecomponents.
• The recovery voltage is the sum a 1– coswave-shape and a high-frequency voltageoscillation on the supply side due to atransient across the short-circuit(inductive) reactance at the time ofinterruption (explanation on next slide).
• There is an initial voltage jump.
• It tends to increase the minimum arcingtime and therefore to increase the shortestduration between contact separation andthe instant of peak recovery voltage.
• Interruption is easier when the voltagejump is higher
Capacitive Current SwitchingVoltage Jump
E
A
TRV HV Circuit Breakers P 37
1- Supply-side voltage aftercurrent interruption, withvoltage jump2- Load-side voltage aftercurrent interruption3- Recovery voltage acrosscircuit-breaker terminals
0
Voltage beforecurrent interruption
1
Capacitive Current SwitchingVoltage Jump
2111
CLE
LC
ECC
IUs
s
A
TRV HV Circuit Breakers P 38
N
A BER
ES
ET
EN
CR
CS
CT
Three-Phase Capacitive Current BreakingCapacitor Bank with Isolated Neutral
TRV HV Circuit Breakers P 39
-1,5
-1,0
-0,5
0,0
0,5
1,0
1,5
2,0
-0 ,005 -0,003 -0,001 0,001 0 ,003 0,005 0,007 0 ,009 0,011 0,013 0 ,015
V B
V A
V N
2.5 p.u.
Three-Phase Capacitive Current BreakingCapacitor Bank with Isolated Neutral
Recovery voltage for the first pole to interrupt
Due to neutral voltage shift (VN) after interruption by the first pole, the peak recovery voltage is 2.5 p.u. instead of 2 p.u. for single-phase interruption.
TRV HV Circuit Breakers P 40
The recovery voltage is higher on the first pole to clear
Three-Phase Capacitive Current BreakingCapacitor Bank with Isolated Neutral
Recovery voltage (RV) on each pole
RV on first-pole-to-clear
uc= 2.5 p.u.kc= 1.25
TRV HV Circuit Breakers P 41
TRV 3-PHASE CAPACITIVE CURRENT SWITCHING (50Hz) Capacitor bank with isolated neutral
0
0,5
1
1,5
2
2,5
3
0 0,5 1 1,5 2 2,5 3 3,5 4 4,5 5 5,5 6 6,5 7 7,5 8 8,5 9 9,5 10T (ms)
TRV
(p.u
.)
Single-phase test with kc= 1,4
Three-phase test
Single-phase test with kc= 1,25
The three-phaserecovery voltage isconsidered to becovered during asingle phase testwith a supplyvoltage equal to thephase to groundvoltage multipliedby 1.4
Three-Phase Capacitive Current BreakingCapacitor Bank with Isolated Neutral
TRV HV Circuit Breakers P 42
In the case of line switching
The recovery voltage isinfluenced by phase-to-ground and phase-to-phasecapacitances
Equivalence during single-phase test is obtained with asupply voltage equal to thephase-to-ground voltagemultiplied by a factor = 1.2(U is 2.4 p.u.).
Three-Phase Line-Charging Current Breaking
TRV HV Circuit Breakers P 43
Three-Phase Cable-Charging Current Breaking
• Types of cables & equivalent circuits
Same case as capacitor bank with grounded neutral
Similar case as overhead lines
Screened cable Belted cable
C1/C0=3 Ur ≤ 52kV
C1/C0=2 Ur > 52kV
TRV HV Circuit Breakers P 44
Three-Phase Capacitive Current Breaking Single-phase tests to simulate three-phase conditions
• Test voltage for single-phase tests:
• Voltage factors in case of effectively grounded neutral systems− Line-charging current kc = 1.2− Cable-charging current kc = 1.0 (screened cable)
= 1.4/ 1.2 (belted cable ≤52kV / >52kV)− Capacitor-bank current kc = 1.0/1.4 grounded/isolated neutral
• Voltage factors in case of non-effectively grounded neutral systems− Line-charging current kc = 1.4− Cable-charging current kc = 1.4− Capacitor-bank current kc = 1.4
• Voltage factors in the case of fault on another line(s)− Effectively grounded neutral systems kc = 1.4− Non-effectively grounded neutral systems kc = 1.7
3r
ctestUkU
Types of Fault TRVs
GRID
TRV HV Circuit Breakers P 46
R C
(Vcb)
L
Real network Equivalent circuit
N Lines, each with surge impedance
clZ
NZR
L: source inductance, lines exceptedC: source capacitance, lines excepted
Types of Fault TRVs / Reminder
TRV HV Circuit Breakers P 47
Types of Fault TRVs / Overdamped TRV
• The exponential part of a TRV occurs when the equivalent resistanceof the circuit with N connected lines in parallel
R = Zeq = is lower or equal to
where Z1 = positive sequence surge impedance of a lineZ0 = zero sequence surge impedance of a line
N = number of lines,
Leq = equivalent inductance, Ceq = equivalent capacitance.• It typically occurs when one or several lines are on the unfaulted sideof the circuit breaker and when the fault is cleared at the circuitbreaker terminals.• The rate of rise of recovery voltage is RRRV = Zeq x (di/dt)
NZ1 eqeq CL /5.0
Exponential (overdamped) TRV
01
0
23
ZZZ
TRV HV Circuit Breakers P 48
Types of Fault TRVs / Overdamped TRV
• Equivalent inductance
when
• Equivalent capacitance
R C
(Vcb)
L01
10eq 2
3LL
LLL
Leq ZeqCeq
32
3)(2 1001
0eqCCCCCC
Three-phase to ground fault
see Annex D: 3-phase network representation
11
10
3.17
93
LLL
LL
eq
TRV HV Circuit Breakers P 49
Types of Fault TRVs / Overdamped TRV
• Equivalent surge impedance (first pole to clear)
01
10eq 2
3ZZ
ZZN
Z
Three-phase to ground fault
3
2
10
1
0
ZZZ
ZZZZZZ
M
MS
MS
ZS: self value
ZM: mutual value
01
0
23
ZZZ
see Annex D: 3-phase network representation
See section on SLF for the calculation of line surge impedance
TRV HV Circuit Breakers P 50
• TRV for parallel RLC circuit
with
ucb is the voltage across the open circuit-breaker
u1 =
= 2 f = 377 rad/s at 60 Hz and 314 rad/s at 50 Hz
I is the short-circuit current (rms)
=
=
Types of Fault TRVs / Overdamped TRV
))sinh(cosh1(1cb tteuu t
eqω2 LI
eqeq21
CZ
)/(1 eqeq2 CL
TRV HV Circuit Breakers P 51
• TRV when Ceq can be neglected
where
• RRRV
Types of Fault TRVs / Overdamped TRV
)1( /1cb
teuu
eq
eq
ZL
dtdIZZI
tu
eqeqcb ω2
dd
TRV HV Circuit Breakers P 52
• Special case of three-phase ungrounded faults
− Equivalent inductance
− Equivalent capacitance
with C1= C0
Types of Fault TRVs / Overdamped TRV
11
eq 5.12
3 LLL
5.132 11
eqCCC
TRV HV Circuit Breakers P 53
• This exponential part of TRV is transmitted as traveling waves oneach of the transmission lines. Reflected wave(s) returning from openlines or discontinuities contribute also to the TRV.
Types of Fault TRVs / Overdamped TRV
TRV HV Circuit Breakers P 54
• As an example, the following figure shows the one line diagram of a550 kV substation. The TRV seen by circuit breaker (A) when clearingthe three-phase fault is shown in the next slide. Circuit breaker (B) isopen.
Types of Fault TRVs / Overdamped TRV
TRV HV Circuit Breakers P 55
0
100
200
300
400
500
600
700
800
900
0 100 200 300 400 500 600 700 800 900 1000
TIME (µs)
VOLTAGE (kV)
SYSTEM TRVTRV CAPABILITY FOR A STANDARD BREAKER
REFLECTED WAVE
A reflection occurs from the end of the shortest line after 2 x 81 / 0.3 = 540 µs
System TRV with reflected wave
Types of Fault TRVs / Overdamped TRV
TRV HV Circuit Breakers P 56
• The exponential part of TRV is transmitted as traveling waves on each of the transmission lines.
• When a wave reaches a discontinuity on the line (another bus or a transformer termination) a reflected wave is produced, which travels back towards the faulted bus.
• It takes 6.67 µs for a wave to go out and back to a discontinuity 1km away as the wave travels at 300 000 km/s (speed of light).
• At a discontinuity transmitted and reflected waves can be described by the following equations:
ba
bit
2ZZ
Zee
ba
abir ZZ
ZZee
Za
Zb
Types of Fault TRVs / Reflected Waves
TRV HV Circuit Breakers P 57
• A wave that reaches a short-circuit point (Zb= 0) is reflectedwith an opposite sign
• A wave that reaches an openpoint (Zb is infinite) is reflectedwith the same sign.The voltage at this point is thendoubled.
ba
bit
2ZZ
Zee
ba
abir ZZ
ZZee
ZaZb
Types of Fault TRVs / Reflected Waves
TRV HV Circuit Breakers P 58
• Example of TRV resulting from several traveling waves
Types of Fault TRVs / Reflected Waves
From CIGRE WG A3-22/28 tutorial in Rio de Janeiro (2012-02)
Times in µs and not in ms
TRV HV Circuit Breakers P 59
• An oscillatory TRV occurs generally when a fault is limited by atransformer or a series reactor and no transmission line (or cable) surgeimpedance is present to provide damping.
Types of Fault TRVs / Underdamped TRV
Oscillatory (underdamped) TRV
TRV HV Circuit Breakers P 60
• To be oscillatory, the equivalent resistance of the source side has tobe such that
Leq = equivalent source inductance
Ceq = equivalent source capacitance.
• To meet this requirement, only a low number of lines (N) must beconnected on the source side.Therefore oscillatory TRVs are specified for− terminal fault test duties T10 and T30 for circuit breakers in
transmission systems (Ur 100 kV),− all terminal fault test duties in the case of circuit breakers in
distribution or sub-transmission systems (Ur < 100 kV).
eq
eqeq C
LNZR 5.0
Types of Fault TRVs / Underdamped TRV
TRV HV Circuit Breakers P 61
• Transmission systems (Ur 100 kV)In the large majority of cases, TRV characteristics (peak value andrate-of-rise) for faults with 10% or 30% of rated short-circuit currentare covered by the rated values defined in the standards for testduties T10 and T30.
Types of Fault TRVs / Underdamped TRV
TRV HV Circuit Breakers P 62
• Triangular-shaped TRVs are associated with short-line faults (seeseparate chapter on SLF).
• After current interruption, the line-side voltage exhibits a characteristictriangular waveshape.
• The rate-of-rise of the saw-tooth shaped TRV is function of the linesurge impedance and current. The rate-of rise is usually higher thanthat experienced with exponential or oscillatory TRVs (with the samecurrent), however the TRV peak is generally low.
line
Circuit breaker
Types of Fault TRVs / Triangular wave-shape
TRV Modification
GRID
TRV HV Circuit Breakers P 64
Current Asymmetry and Circuit Breaker Influence on TRV
TRV HV Circuit Breakers P 65
• When interrupting asymmetrical currents, TRV is less severe (lowerRRRV and TRV peak) than when interrupting the relatedsymmetrical current because the instantaneous value of the supplyvoltage at the time of interruption is less than the peak value.
TIME
CURRENT
SUPPLY VOLTAGE
TRV Modification / Current Asymmetry
TRV HV Circuit Breakers P 66
• Correction factors of the TRV peak and rate of rise of recovery voltage(RRRV) when interrupting asymmetrical currents are given in
− IEEE C37.081 “IEEE Guide for Synthetic Fault Testing of AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis”.
− IEEE C37.081a “Supplement to IEEE Guide for Synthetic FaultTesting 8.3.2: Recovery Voltage for Terminal Faults; AsymmetricalShort-Circuit Current”.
− IEC 62271-100 “High-Voltage Circuit-Breakers” (2012-09).
− IEC 62271-101 “Synthetic testing” (2012-10): Annex I
TRV Modification / Current Asymmetry
TRV HV Circuit Breakers P 67
TRV Modification / Current Asymmetry
• The RRRV is proportional to the slope of current before interruption(di/dt). Factor F1 gives the correction due to current asymmetry:
with D degree of asymmetry (p.u.)
- D interruption after a major loop of current
+ D interruption after a minor loop of current
X / R short-circuit reactance divided by resistance
• When time to peak TRV is relatively short (< 500 µs), the correctionfactor for the TRV peak is also F1.
RXDDF/
1 21
TRV HV Circuit Breakers P 68
TRV Modification / Current Asymmetry
• Correction factor for the TRV peak in case of long time to peak TRV(> 500 µs) :
TRV HV Circuit Breakers P 69
• During current interruption, the circuit TRV can be modified by acircuit breaker:
− by arc resistance,
− by the circuit breaker capacitance or opening resistor (if any).
• The TRV measured across the terminals of two different types ofcircuit breakers under identical conditions can be different.
• To simplify both rating and application, the power system TRV iscalculated ignoring the influence of the circuit breaker.
The circuit breaker is considered to be ideal i.e. without modifyingeffects on the electrical characteristics of a system,
− when conducting its impedance is zero,
− at current zero its impedance changes from zero to infinity.
TRV Modification / Circuit Breaker Influence
TRV HV Circuit Breakers P 70
• When a circuit breaker is fitted with grading capacitors or with line-to-ground capacitors, these capacitors can reduce significantly the rate-of-rise of TRV during short-line faults.
• Opening resistors (R) are used to assist interruption by air blast circuitbreakers, they are used on some SF6 circuit breakers (Japanese550kV 1 break & 1100 kV 2 breaks).
The RRRV (rate of rise ofrecovery voltage) is reducedas follows
The resistor (R) is in parallelwith the surge impedance ofthe system (Z). Air blast Generator Circuit Breaker
with opening resistor
2IRZRZ
dtdi
RZRZ
dtdu
TRV Modification / Circuit Breaker Influence
TRV HV Circuit Breakers P 71
Interruption with Opening Resistance
Arc extinction is facilitated by reducing the voltage stress (RRRV) after current interruption, a parallel resistance is used for this purpose
R
TRV Modification / Circuit Breaker Influence
Terminal Fault TRV
GRID
TRV HV Circuit Breakers P 73
Terminal fault TRV First pole to clear factor
TRV HV Circuit Breakers P 74
Current - TRV - Recovery Voltage
CURRENT
TRANSIENT RECOVERYVOLTAGE
RECOVERY VOLTAGE
Terminal Fault TRV
TRV HV Circuit Breakers P 75
• First Pole to Clear Factor (kpp)− During 3-phase faults interruption, the recovery voltage is higher on
the first pole to clear. − The first-pole-to clear factor is the ratio of the power frequency
voltage across the first interrupting pole, before current interruptionin the other poles, to the power frequency voltage occurring acrossthe pole after interruption in all three poles.
− It is the ratio between the recovery voltage (RV) across the first pole to clear and the phase to ground voltage of the system.
3
VoltageRecoverypp Urk
Terminal Fault TRV
TRV HV Circuit Breakers P 76
• First Pole to Clear Factor (kpp)
A BER
ES
ET
3rpp
Uk
3rU
Terminal Fault TRV
TRV HV Circuit Breakers P 77
• When tests are performed on one pole (single-phase tests), the supplyvoltage must be multiplied by kpp in order to have the recovery voltagethat would be met on the first pole during a three-phase interruption.
• The first–pole–to-clear factor (kpp) is a function of the groundingarrangements of the system and of the type of fault.
Note: for UHV systems (rated voltages 1100 & 1200kV) the ratio X0/X1is close to 2 and the standardized value of kpp is 1.2.
• For three-phase ungrounded faults, kpp is 1.5.
Terminal Fault TRV
For systems with non-effectively grounded neutral, kpp is 1.5.
For three-phase to ground faults in systems with effectively groundedneutral, kpp is 1.3 (see Annex A).
TRV HV Circuit Breakers P 78
Three-phase faults in non-effectively grounded systems or three-phase ungrounded faults
In these cases, kpp is 1.5
Terminal Fault TRV
TRV HV Circuit Breakers P 79
Terminal Fault TRV Example of First-Pole-To-Clear Factor (kpp)
3-phase ungrounded fault in effectively-grounded neutral
When pole A interrupts.
voltage eA is maximum = 1 p.u.
eB = eC = - 0.5 p.u.First-pole-to-clear
factor is 1.5
5.1)5.0(1
5.02
2
2
02
PA
CBP
CBBBP
CB
CB
ee
eee
eeedtdiLee
eedtdiL
edtdiLeL
L
Li
i
TRV HV Circuit Breakers P 80
A BER
ES
ET
First-pole-to-clear factor is 1.5
When the first pole interrupts: Voltage at neutral point N:EN + ES = Xsc IEN + ET = - Xsc IEN = – (ES + ET)/2ER is maximum = Emax cos(0°) = 1 p.u.ES = Emax cos (120°) = -0.5 p.u.ET = Emax cos (240°) = -0.5 p.u.then EN = 0.5 p.u.Voltage EA = EN + ER = 1.5 p.u.
N
Xsc
Xsc
Xsc
kpp= 1.51 p.u.
Terminal Fault TRV Example of First-Pole-To-Clear Factor (kpp)
3-phase to ground fault in non-effectively grounded system
TRV HV Circuit Breakers P 81
E I3
I2
I1
V3
V2
V1
Single-phase fault in an effectively grounded system
• In this case, kpp is 1.0 as the circuit breaker interrupts under the phase-to-ground voltage.
Terminal Fault TRVFirst-Pole-To-Clear Factor (kpp)
TRV HV Circuit Breakers P 82
Three-phase to ground fault in effectively grounded neutral systems
• The value of kpp is dependent upon the sequence impedances from the location of the fault to the various system neutral points (ratio X0/X1).
where X0 is the zero sequence reactance of the system,
X1 the positive sequence reactance of the system.
For systems up to 800 kV, the ratio X0/X1 is taken to be 3.0.
Hence, for systems with effectively grounded systems kpp is 1.3.
Terminal Fault TRVFirst-Pole-To-Clear Factor (kpp)
01
02
3XX
Xk pp
TRV HV Circuit Breakers P 83
Equations for the other clearing poles• In systems with non-effectively grounded neutral, after interruption of
the first phase (R), the current is interrupted by the last two poles inseries under the phase-to-phase voltage (ES – ET) equal to timesthe phase voltage
ER
ES
ET
I
I
ES - ET
3
Terminal Fault TRVPole-To-Clear Factor
TRV HV Circuit Breakers P 84
It follows that, in systems with non-effectively grounded neutrals,for the second and third pole to clear:
87.023ppk
Current in each phase TRV in each phase
Terminal Fault TRVPole-To-Clear Factor
After interruption of the 3 poles, the recovery voltage is 1 p.u.
TRV HV Circuit Breakers P 85
In systems with effectively grounded neutrals, the second pole clearsa three-phase to ground faultwith a factor
If X0 / X1 = 3.0 the second pole to clear factor is 1.25.10
2110
20
23
XXXXXX
k pp
Currents TRVs
Terminal Fault TRVPole-To-Clear Factor
See Annex B
TRV HV Circuit Breakers P 86
E I3
I2
I1
V3
V2
V1
In systems with effectively grounded neutral, for the third pole-to-clear:
1ppk
Terminal Fault TRVPole-To-Clear Factor
TRV HV Circuit Breakers P 87
Pole-to-clear factors (kp) for each clearing pole3-phase to ground case
Note: values of the pole-to-clear factor are given for X0/X1 = 1.0 toindicate the trend in the special case of networks with a ratio X0/X1 ofless than 3.0.
kpp= 1.5 is taken for all systems that are not effectively grounded, itincludes (but is not limited to) systems with isolated neutral (it is alsotaken for three-phase ungrounded faults).
Neutral X0/X1
first pole 2nd pole 3rd pole
isolated infinite 1.5 0.87 0.87
effectivelygrounded 3.0 1.3 1.27 1.0
see note 1.0 1.0 1.0 1.0
Pole to clear factor
Terminal Fault TRVPole-To-Clear Factor
TRV HV Circuit Breakers P 88
Terminal fault TRV Rating & Testing
TRV HV Circuit Breakers P 89
CURRENT
TRANSIENT RECOVERYVOLTAGE
Supply voltage
Terminal Fault TRV Rating
Current
Transient recovery voltage
Supply voltage
TRV HV Circuit Breakers P 90
• The TRV ratings for circuit breakers are applicable for interruptionof three-phase faults with− a rated symmetrical short circuit current− at the rated voltage of the circuit breaker.
• In IEC− While three-phase ungrounded faults produce the highest TRV
peaks, the probability of their occurrence is very low.Therefore, in IEC 62271-100 the TRV ratings are based onthree-phase to ground faults.
− TRV parameters are given in subclause 4.102 of IEC 62271-100.
− For values of fault current other than rated and for line faults,related TRV capabilities are given in subclause 6.104.5 of IEC62271-100.
Terminal Fault TRV Rating
TRV HV Circuit Breakers P 91
• In ANSI/IEEE− TRV withstand capabilities are given in ANSI/IEEE C37.04 and
IEEE C37.06.− In the case of terminal faults, for circuit-breakers of rated
voltages equal or higher than 100 kV, separate Tables giveTRVs for three-phase to ground and three-phase ungroundedfaults.
Terminal Fault TRV Rating
TRV HV Circuit Breakers P 92
• ANSI/IEEE C37.06 – Table 10
Terminal Fault TRV Rating
TRV HV Circuit Breakers P 93
• ANSI/IEEE C37.06 – Table 11
Terminal Fault TRV Rating
TRV HV Circuit Breakers P 94
• For circuit breakers applied on systems 72.5 kV and below, the TRVratings assume that the system neutrals can be non-effectivelygrounded.
• For circuit breakers applied on systems 245 kV and above, the TRVratings assume that the system neutrals are effectively grounded.
• Standard TRV are defined by two-parameter and four-parameterenvelopes.
• These envelopes are used to compare
− System TRVs
− Standard TRVs
− Test TRVs
Terminal Fault TRV Rating
TRV HV Circuit Breakers P 95
Terminal Fault TRV Rating
• A two-parameter envelope is used for oscillatory (underdamped)TRVs specified in standards for:
− circuit breakers rated less than 100 kV, at all values of breakingcurrent,
− circuit breakers rated 100 kV and above if the short-circuitcurrent is equal or less than 30% of the rated breaking current.
3/'
23
c
afppr
c
uu
kkUu
),2(05.0),1(15.0
3
3
systemslineSClassttsystemscableSClasstt
d
d
The test TRV must not cross the delay segment defined by (td , 0) and (t’, u’)
TRV HV Circuit Breakers P 96
• A four-parameter envelope is specified for circuit breakers rated 100 kVand above if the short-circuit current is more than 30% of the ratedbreaking current (cases with over-damped TRVs).
1211 42/'23
75.023
ttuukkUukUu afppr
cppr
Terminal Fault TRV Rating
TRV HV Circuit Breakers P 97
The peak value of TRV is defined as follows:
where
kpp is the first pole to clear factor
kaf is the amplitude factor (ratio between the peak value of TRV andthe peak value of the recovery voltage at power frequency).
In IEC 62271-100 and IEEE C37.04, kaf is 1.4 at 100% rated breakingcurrent.
32 r
ppafcUkkU
Terminal Fault TRV Rating
TRV HV Circuit Breakers P 98
TRV envelopes for terminal fault (Ur < 100 kV)
I is the rated short-circuit current TIME
VOLTAGE
1.0 I0.6 I0.3 I0.1 I
Terminal Fault TRV Rating - Ur < 100 kV
TRV HV Circuit Breakers P 99
• Cable systems and line systemsIn order to cover all types of networks (distribution, industrial and sub-transmission) and for standardization purposes, two types of systemsare introduced:− Cable systems
Cable systems have a TRV during breaking of terminal fault at100% of short-circuit breaking current that does not exceed theenvelope derived from Table 24 in Edition 1.2 of IEC 62271-100.TRV values are those defined in the former editions of IECstandard for high-voltage circuit breakers.
− Line systemsLine systems have a TRV during breaking of terminal fault at 100% of short-circuit breaking current defined by the envelope derived from Table 25 in Edition 1.2 of IEC 62271-100. Standard values of TRVs for line systems are those defined in ANSI/IEEE C37.06 for outdoor circuit-breakers.
Terminal Fault TRV Rating - Ur < 100 kV
TRV HV Circuit Breakers P 100
• Comparison of TRVs for cable systems and line-systems
The rate of rise of recovery voltage (RRRV) for line systems is approximately twice the value for cable systems
Envelope of Cable system TRV
Envelope of Line system TRV
t3
Uc
Terminal Fault TRV Rating - Ur < 100 kV
TRV HV Circuit Breakers P 101
• Classes of Circuit breakersCircuit breaker Ur < 100 kV
Cable-system
Line-system
Cable-system
Direct connection to OH line
SLF ?
No
Yes
YesDirect connection
to OH line
Class CS
Class LS
Class LS
Class S1
Class S2
Class S2Short-line fault breaking performance is required only for class S2
Terminal Fault TRV Rating - Ur < 100 kV
TRV HV Circuit Breakers P 102
1,2
1,3
1,4
1,5
1,6
1,7
1,8
1,9
Am
plitu
de fa
ctor
(p.u
.)
T10 T30 T60 T100
Amplitude factor for terminal fault (Ur < 100 kV) Class S2 circuit breakers
10% I 30% I 60% I 100% I
Terminal Fault TRV Rating - Ur < 100 kV
TRV HV Circuit Breakers P 103
0,4
0,6
0,8
1
1,2
1,4
1,6
12,5 22,5 32,5 42,5 52,5 62,5 72,5
RRRV for terminal fault T100 (Ur < 100 kV) Class S2 circuit breakers
Terminal Fault TRV Rating - Ur < 100 kV
RRRV (kV/µs)
Ur(kV)
15kV24kV
38kV
52kV
72.5kV1.47
1.33
1.21
1.05
0.91
TRV HV Circuit Breakers P 104
Terminal Fault TRV Rating - Ur < 100 kV
• Calculation of standard RRRV: circuit breaker 72.5 kV class S2
− Time to peak TRV was taken from ANSI C37.06:
− Time t3 is 88% of T2 (1-COS waveshape): t3 = 93 µs
− TRV peak uc is calculated from Ur, kpp and kaf
− RRRV is the ratio of uc and t3 :
it is the present value in IEC and IEEE standards.
kVuc 1373
25.7254.15.1
µskVVATR /47.193
137
µsT 1062
TRV HV Circuit Breakers P 105
0,4
0,6
0,8
1
1,2
1,4
1,6
12,5 22,5 32,5 42,5 52,5 62,5 72,5
RRRV for terminal fault T100 (Ur < 100 kV) Class S2 circuit breakers
Terminal Fault TRV Rating - Ur < 100 kV
RRRV (kV/µs)
Ur(kV)
305.04.0 rURRRV
15kV24kV
38kV
52kV
72.5kV1.47
1.33
1.21
1.05
0.91
20kV
1kV/µs
TRV HV Circuit Breakers P 106
Terminal Fault TRV Rating - Ur < 100 kV
• RRRV at reduced short-circuit current (Class S2)
− Time t3 for T100 is multiplied by the following factors
0.67 for T60
0.40 for T30 and T10
− Compared with the standard value for T100, the RRRV atreduced short-circuit current is divided by the multiplier for timet3 and multiplied by the increase of amplitude factor.
− Example: T60 72.5 kV
µskVRRRV /35.254.165.1
67.047.1
TRV HV Circuit Breakers P 107
TRV envelopes for terminal fault (Ur 100 kV)
I is the rated short-circuit currentNote: time to peak for T60 is shown here according to IEEE, it is half the IEC value
Terminal Fault TRV Rating - Ur ≥ 100 kV
TRV HV Circuit Breakers P 108
Amplitude factor for terminal fault (Ur 100 kV) according to IEC and IEEE C37.06
Terminal Fault TRV Rating - Ur ≥ 100 kV
1
1,1
1,2
1,3
1,4
1,5
1,6
1,7
1,8
10 20 30 40 50 60 70 80 90 100
IEEE k pp=1.5
IEC & IEEE k pp=1.3kaf (p.u.)
% Isc
Case 10 % Isc: kpp x kaf = 2.46 (IEEE kpp=1.5) and 2.29 (IEC & IEEE kpp=1.3)
TRV HV Circuit Breakers P 109
Rate-of-rise-of-recovery-voltage for terminal fault(Ur 100 kV)
1
2
3
4
5
6
7
8
RR
RV
(kV/
µs)
T10 T30 T60 T100
Terminal Fault TRV Rating - Ur ≥ 100 kV
TRV HV Circuit Breakers P 110
• A circuit breaker TRV capability is considered to be sufficient if the twoor four parameter envelope drawn with rated parameters is equal orhigher than the two or four parameter envelope of the system TRV.
System TRV envelope
Circuit breaker rated TRV envelope
time
Voltage
Terminal Fault TRVApplication
TRV HV Circuit Breakers P 111
• The parameters that define the circuit breaker TRV capabilities varywith the circuit breaker voltage rating and short-circuit currentinterrupting level.
• The circuit breaker TRV capabilities at 10%, 30%, 60% and 100% ofrated short-circuit interrupting current (Isc), corresponding to terminalfault test duties T10, T30, T60 and T100, are given in IEEE StdC37.06.
• The circuit breaker TRV withstand capability envelope at any othershort-circuit interrupting current below rated can be derived using themultipliers given in Table 1 of IEEE C37.011-011.
• TRV studies are sometimes carried out to determine if a system TRVis covered by the circuit breaker TRV capability demonstrated by typetests, either when new circuit breakers are to be installed or followinga system change.
Terminal Fault TRVApplication
TRV HV Circuit Breakers P 112
• It is not uncommon that the maximum short-circuit current falls inbetween 30% and 60% of the circuit breaker rated short-circuit current.
• To allow comparison of system TRV and circuit breaker TRV withstandcapability and to avoid additional testing, a method of interpolation ofTRV capabilities demonstrated by type tests was introduced in theformer editions of IEEE C37.011.
• Following the introduction of the two-parameter and four-parameterdescription of TRVs, this method of interpolation in the current rangebetween T30 and T60 (terminal faults with respectively 30% and 60%of Isc) was not clearly stated in the 2005 edition of IEEE C37.011.
• Thus, the method of interpolation has been further developed in IEEEC37.011-2011 to define the circuit breaker TRV withstand capability forshort-circuit currents in this range between T30 and T60.
Terminal Fault TRVApplication
TRV HV Circuit Breakers P 113
• In standards, it is considered that 30 % of Isc is the maximum short-circuit current for which a two parameter TRV is applicable for circuitbreakers rated 100 kV and above.
• The related TRV capability for short-circuit currents between 30 % of Iscand 60 % of Isc is then necessarily a four parameter TRV.
• The Working Group in charge of IEEE Guide C37.011 has defined thatthe TRV capability between T30 and T60 can be considered to have arate-of-rise (u1/t1) and a first reference voltage (u1) that haveintermediate values between those of T30 and T60.
Terminal Fault TRVApplication
TRV HV Circuit Breakers P 114
• TRV parameters (u1, t1, uc, t2) for any terminal fault current between 30 % and 60 % of Isc can be obtained as follows:
− u1 and t1 are linearly interpolated between u1 and t1 of T60 and ucand t3 of T30
− uc and t2 are linearly interpolated between uc and t2 of T60 and ucand t3 of T30
• The method of interpolation is illustrated by the Figure shown on the next slide.
Terminal Fault TRVApplication
TRV HV Circuit Breakers P 115
Terminal Fault TRVApplication
245kV Breaker TRV Envelope
0
50
100
150
200
250
300
350
400
450
500
0 50 100 150 200 250
Time (µs)
kV
T100
T75
T60
T55
T50
T45
T40
T35
T30
T10
u1,t1
Example of TRV interpolation for a 245kV circuit breaker
TRV HV Circuit Breakers P 116
* When the system TRV has an initial slope that is higher than the valuespecified for terminal fault type tests, Guide IEEE C37.011 authorizesto combine the TRV withstands demonstrated during terminal fault andshort-line-fault (same range of currents).
Terminal Fault TRVApplication
Voltage withstand by a 550kV circuit breaker at 75% rated breaking capability
TRV HV Circuit Breakers P 117
• Tests are required at 100% (T100), 60% (T60), 30% (T30) and 10% (T10) of rated short-circuit current with the corresponding rated TRVs and recovery voltages.
• In IEC 62271-100, 3 tests are required with a symmetrical current for each test duty, except T100 that is performed as follows− 3 tests with symmetrical current and− 3 tests with asymmetrical current (when interrupting asymmetrical
currents, the rate-of-rise and peak value of TRV are reduced but the energy in the arc is higher).
• In IEEE Std C37.09− for each test duty T10, T30, T60: 2 tests are required with
symmetrical current and 1 test with asymmetrical current.− test duty T100 is performed as in IEC
Terminal Fault TRVTesting
TRV HV Circuit Breakers P 118
• During testing, the envelope of the test TRV (in red) must be equal or higher than the specified TRV envelope (in blue).
This procedure is justified as it allows to compare TRVs in the tworegions where a restrike is likely: during the initial part of the TRV wherethe RRRV is maximum and in the vicinity of the peak voltage (uc).
U(kV)
t (µs)t2t1
uc
u1
u'
t'
Reference line of specified TRV
Envelope of prospective test TRV
Prospective test TRV
Delay line of specified TRV
0 td
A
B
C
Terminal Fault TRVTesting
TRV HV Circuit Breakers P 119
• In a network, the initial part of the TRV may have a high-frequencyoscillation of small amplitude.
• This ITRV (Initial Transient Recovery Voltage) is due to reflectionsfrom the first major discontinuity along the busbar.
• It may influence the thermal phase of interruption.
• In most cases the ITRV withstand capability is proven during short-line-fault tests.
Terminal Fault TRVInitial TRV
More information is given in the chapter dedicated to ITRV
TRV HV Circuit Breakers P 120
Terminal fault TRV & Arcing Times
TRV HV Circuit Breakers P 121
Arcing time
-1,5
-1
-0,5
0
0,5
1
1,5
0 0,005 0,01 0,015 0,02 0,025 0,03 0,035 0,04 0,045 0,05
Contacts separation
Time
Interruption at 2nd passage through zero
1st passage through zero
Arcing time = 13 ms
Current
Terminal Fault TRV & Arcing Time
TRV HV Circuit Breakers P 122
Terminal Fault TRV & Arcing Times
In the case of periodicphenomena, durationscan be expressed inmilliseconds or inelectrical degrees.For a system frequencyof 50 Hz, the duration ofone half loop is 10 ms, itcorresponds to 180° el., itfollows that 18° el. = 1ms
For a system frequencyof 60 Hz the duration ofone half loop is 8.33 msso 18° el. = 0.83 ms
-1,5
-1
-0,5
0
0,5
1
1,5
0 0,002 0,004 0,006 0,008 0,01 0,012 0,014 0,016 0,018 0,02
One period at 50 Hz
10 ms
TRV HV Circuit Breakers P 123
Contacts separation
1st pole clears
last poles clear
Arcing time 1st pole
Arcing time last poles
Terminal Fault TRV & Arcing Times
Current
One period (360°) at 60Hz is 16.7 ms
One period (360°) at 50Hz is 20 ms
TRV HV Circuit Breakers P 124
Minimum & Maximum Arcing Times
• Case 1: Reference case with contact separation at 29.67ms
Arcing time pole 3 = 8.4ms (minimum arcing time)
Example three-phase fault interruption
Fr = 50 Hz
Pole 3 interrupts first
System with non-effectively grounded neutral
TRV HV Circuit Breakers P 125
Minimum & Maximum Arcing Times
• Case 2: Contact separation advanced by 3.33ms (60°) = 26.34ms
Arcing time pole 1 = 8.4ms
Pole 1 interrupts first with the same arcing time as in Case 1 by pole 3
i.e. same breaking conditions in terms of arcing times
TRV HV Circuit Breakers P 126
Minimum & Maximum Arcing Times
• Case 3: Contact separation advanced by 2.33ms (42°) = 27.34ms
Pole 3 interrupts first with the longest arcing time for a first pole to clearArcing time pole 3 = 10.7ms = 8.4ms + 42°
Arcing time pole 1 = 15.7ms= 8.4ms + 7.3ms= 8.4ms + 132°maximum arcing time
The range of arcing times for the first pole to clear is 42°
TRV HV Circuit Breakers P 127
Minimum & Maximum Arcing Times
Example with fr = 50 HzThree-phase faults in non-effectivelygrounded systems or three-phaseungrounded faults
-50000
-40000
-30000
-20000
-10000
0
10000
20000
0 5 10 15 20 25 30 35 40
Time (ms)
Cur
rent
(A)
Iarc
Iarc
Contact separation
Contact separation
tarc min = 12 ms
tarc max = 19,33 ms
18°
-50000
-40000
-30000
-20000
-10000
0
10000
20000
0 5 10 15 20 25 30 35 40
Time (ms)
Cur
rent
(A)
Iarc
Iarc
Contact separation
Contact separation
tarc min = 12 ms
tarc max = 19,33 ms
18°
TRV HV Circuit Breakers P 128
Minimum arcing time (blue phase) Tmin = 12 ms
Contact separation delayed by 18° el. (or 1 ms)
Maximum arcing time (blue phase) = 19.33 ms(14.33 ms + 90°= Tmin + 132°)
Arcing time 1st phase (red phase) = 14.33 ms(Tmin + 60° - 18°
= Tmin + 42°)
-20000
-15000
-10000
-5000
0
5000
10000
15000
200000 5 10 15 20 25 30 35 40
time [ms]
curr
ent [
A]
18° el.
-20000
-15000
-10000
-5000
0
5000
10000
15000
200000 5 10 15 20 25 30 35 40
time [ms]
curr
ent [
A]
Three-phase faults in non-effectively grounded systems orthree-phase ungrounded faultsTmin = 12 ms
T max = 19.33 ms
Contact separation
Iarc
Iarc
Contact separation
Minimum & Maximum Arcing Times (50Hz)
TRV HV Circuit Breakers P 129
-20000
-15000
-10000
-5000
0
5000
10000
15000
200000 5 10 15 20 25 30 35 40
time [ms]
curr
ent [
A]
-20000
-15000
-10000
-5000
0
5000
10000
15000
200000 5 10 15 20 25 30 35 40
time [ms]
curr
ent [
A]
Minimum arcing time (blue phase) Tmin = 12 ms
Contact separation delayed by 18° el. (or 0.83 ms)18° el.
Maximum arcing time (blue phase) = 18.1 ms
(13.94 ms + 90°= Tmin + 132°)
Arcing time 1st phase (red phase) = 13.94 ms(Tmin + 60° - 18°
= Tmin + 42°)
Three-phase faults in non-effectively grounded systems orthree-phase ungrounded faults
Tmin = 12 ms
T max = 18.1 ms
Contact separation
Iarc
Iarc
Contact separation
Minimum & Maximum Arcing Times (60Hz)
Breaking Tests HV Circuit-Breakers – Denis Dufournet
Three-phase fault in network with isolated neutral (Ur < 245kV)
A BER
ES
ET
Interruption of current in a first pole, followed ¼ cycle later by interruption of the two other poles in series
Terminal Fault Arcing timesThree-Phase Short-Circuit Current Interruption
Current
Time
Contact separation
Breaking Tests HV Circuit-Breakers – Denis Dufournet
Three-phase fault in network with effectively grounded neutral (Ur ≥ 245kV)
A BER
ES
ET
The three poles interrupt at separate current zeros withdifferent arcing times
CurrentsVoltages
Terminal Fault Arcing TimesThree-Phase Short-Circuit Current Interruption
Contact separation
TRV HV Circuit Breakers P 132
Three-phase faults innon-effectively groundedsystems or three-phaseungrounded faults
Three-phase faults ineffectively groundedsystems
Currents TRVs (pole factor)
1.5
0.87
0.87
1.3
1.27
1.0
90°
120°
Maximum arcing time= Tmin + 132°
= Tmin + 6.1 ms
Maximum arcing time= Tmin + 162°
= Tmin + 7.5 ms
Arcing Times and TRVs / Fr = 60 Hz
TRV HV Circuit Breakers P 133
Three-phase faults innon-effectively groundedsystems or three-phaseungrounded faults
Three-phase faults ineffectively groundedsystems
Currents TRVs (pole factor)
1.5
0.87
0.87
1.3
1.27
1.0
90°
120°
Maximum arcing time= Tmin + 132°
= Tmin + 7.3 ms
Maximum arcing time= Tmin + 162°= Tmin + 9 ms
Arcing Times and TRVs / Fr = 50 Hz
TRV HV Circuit Breakers P 134
Minimum arcing time + 180° -18°
Pole to clear factor
° el.
Terminal Fault TRV & Arcing Times
Arcing time
Reference = Minimum arcing time first pole
TRV HV Circuit Breakers P 135
Reference = Minimum arcing time first pole to clear
Pole to clear factor
° el.ms
Terminal Fault TRV & Arcing Times at 60Hz
Arcing time
7.55.53.55 6.14.151.95
Arcing times in ms FR = 60 Hz
0
5.55
TRV HV Circuit Breakers P 136
Minimum arcing time + 180° -18°Reference = Minimum arcing time first pole
Single-phase "umbrella" test with kpp=1.3
Increased stress
Pole to clear factor
° el.
Terminal Fault TRV & Arcing Times
TRV HV Circuit Breakers P 137
Single-phase tests with minimum & maximum arcing time
-1,5
-1
-0,5
0
0,5
1
1,5
0 0,005 0,01 0,015 0,02 0,025 0,03 0,035 0,04 0,045 0,05
Contacts separation
Time
Minimum arcing time = 13 ms
Current
-1,5
-1
-0,5
0
0,5
1
1,5
0 0,005 0,01 0,015 0,02 0,025 0,03 0,035 0,04 0,045 0,05
Contacts separation
Time
restrike with arcing time 12 ms
Mximum arcing time = 22 ms= 13 ms + 10 ms - 1 ms = 13ms + 180° el. - 18° el.
Current
Terminal Fault TRV & Arcing Times
Example with F=50Hz
TRV HV Circuit Breakers P 138
Terminal Fault TRVGenerator Circuit Breakers
TRV HV Circuit Breakers P 139
• Special TRV requirements are applicable for generator circuit breakers installed between a generator and a transformer.
• Two types of faults need to be considered
A1 System-source fault B1 Generator-source fault
Generator Circuit Breakers TRV
TRV HV Circuit Breakers P 140
• For the two types of fault, the TRV has an oscillatory waveshape andthe first-pole-to-clear factor is 1.5 in order to cover three-phaseungrounded faults.
• TRV parameters, i.e. peak voltage uc, rate-of-rise (RRRV) and timedelay, are listed in ANSI/IEEE C37.013.
TRV for system-source faults• RRRV for system-source faults is 3 to 5 times higher than the value
specified for distribution or sub-transmission circuit breakers ANSI/IEEEC37.04.This is due to the fact that the TRV frequency is dominated by thenatural frequency of the step-up transformer.
• IEEE has defined TRV parameters in several ranges of transformerrated power.
Generator Circuit Breakers TRV
TRV HV Circuit Breakers P 141
• TRV parameters for System-Source FaultsTable 5a– TRV parameters for system - source faults
Inherent TRVTransformer
Rating T2 -Time to - Peak E2 -Peak Voltage TRV Rate
(MVA) (µs) (kV) (kV / µs)
Line Column 1 Column 2 Column 3 Column 4
1 10 - 50 0.68 V 1.84 V 3.2
2 51 - 100 0.62 V 1.84 V 3.5
3 101 - 200 0.54 V 1.84 V 4.0
4 201 - 400 0.48 V 1.84 V 4.5
5 401 - 600 0.43 V 1.84 V 5.0
6 601 - 1000 0.39 V 1.84 V 5.5
7 1001 or more 0.36 V 1.84 V 6.0
Generator Circuit Breakers TRV
TRV HV Circuit Breakers P 142
Generator Circuit Breakers TRV
• TRV for system-source faults (Cont’d)In IEEE C37.013-1993, the WG introduced time t3 (coming from IEC) todefine precisely the determination of the TRV rate.
E2 is equal to 1.84 V where V is the rms value of the rated maximum voltage and the value 1.84 is equal to
x 1.5 (= first-pole-to-clear-
factor) x 1.5 (= amplitude factor)32
rateTRVEtT
85.085.023
2
TRV HV Circuit Breakers P 143
TRV for system-source faults (Cont’d)• The RRRV can be significantly reduced if a capacitor is installed
between the circuit breaker and the transformer. It is also reduced inthe special cases where the connection between the circuit breakerand the transformer(s) is made by cable(s) [29].
TRV RATE FOR SYSTEM FED FAULTS TRANSFORMER 50MVA<<=100MVA
2
2,2
2,4
2,6
2,8
3
3,2
3,4
3,6
0 2000 4000 6000 8000 10000 12000
CABLE CAPACITANCE (pF)
TRV
RA
TE (k
V/µs
)
100MVA81MVA
65,5MVA
Generator Circuit Breakers TRV
TRV HV Circuit Breakers P 144
TRV for system-source faults (Cont’d) • When a capacitance is added between the circuit breaker and the
step-up transformer, the TRV peak is increased (explanation: seegeneral considerations).
Generator Circuit Breakers TRV
TRV peak increase (p.u.)
Capacitance (pF)
E2 MULTIPLIER FOR SYSTEM FED FAULTS TRANSFORMER 50MVA<<=100MVA
1
1,05
1,1
1,15
1,2
1,25
1,3
0 2000 4000 6000 8000 10000 12000
CABLE CAPACITANCE (pF)
E2 M
ULT
IPLI
ER (p
.u.)
100 MVA
81 MVA
65.5 MVA
TRV HV Circuit Breakers P 145
Generator Circuit Breakers TRV
• TRV for generator-source faults
RRRV for generator-source faults is roughly 2 times the valuesspecified for distribution or sub-transmission circuit breakers.
“Table 6a – TRV parameters for generator - source faults
Inherent TRVGenerator
Rating T2 -Time - to – Peak E2 -Peak Voltage TRV Rate
(MVA) (µs) (kV) (kV / µs)
Line Column 1 Column 2 Column 3 Column 4
1 10 - 50 1.44 V 1.84 V 1.5
2 51 - 100 1.35 V 1.84 V 1.6
3 101 - 400 1.20 V 1.84 V 1.8
4 401 - 800 1.08 V 1.84 V 2.0
5 801 or more 0.98 V 1.84 V 2.2
TRV HV Circuit Breakers P 146
• TRV in case of asymmetrical currents
− Due to the large time constants of generators and transformers(high X/R), generator circuit breakers are required to interruptcurrents with a high percentage of dc component (high asymmetry).
− The rate-of rise and peak value of TRV during interruption ofcurrents with large asymmetry are significantly reduced.
− In this case, the stress is mainly due to the current amplitude andthe energy in the arc (mechanical and thermal stresses), and to alesser extent to the TRV.
− The more severe TRV stress is obtained during interruption ofsymmetrical currents.
Generator Circuit Breakers TRV
TRV HV Circuit Breakers P 147
• First-pole-to-clear factor− Effectively earthed systems kpp = 1.3 (1.2 for UHV)− Non-effectively earthed systems kpp = 1.5
• Rating− TRV with 2 or 4 parameters− Classes S1 and S2 for rated voltages < 100 kV
• Testing circuit breakers ≥ 100 kV− RRRV: 7 – 5 – 3 – 2 kV/µs for resp. T10, T30, T60, T100s− Interrupting window: 162° (kpp = 1.3) or 132° (kpp = 1.5)
• Generator circuit breakers higher RRRV for T100s
Terminal Fault TRV / Summary
TRV HV Circuit Breakers P 148
Short-Line-Fault (SLF)
TRV HV Circuit Breakers P 149
• The severity of SLF with its associated very fast rate-of-rise-of-recovery-voltage (RRRV) was identified at the end of the 1950’s.
• First SLF tests were performed in 1956-1958 in the USA (G.E.), alsoat Mettlen substation (CH), Fontenay (EDF High Power Laboratories)and CESI. The aim was to compare theoretical studies andexperiments.
• The first published paper on SLF is considered to be by W.F. Skeats,C.H. Titus, W.R. Wilson (G.E.) in Transactions AIEE, submitted inApril 1957 and published in February 1958.
• In Europe, a paper by Michel Pouard (EDF) was published in theBulletin de la Société Française des Electriciens in Nov. 1958.
Introduction
TRV HV Circuit Breakers P 150
Introduction
Paper in Power Apparatus andSystems, Part III, Transactions ofthe American Institute ofElectrical Engineers. Publicationin February 1958
Test laboratory line used by GeneralElectric in 1957 to test air-blastcircuit-breakers. It was 1.6km long,short-circuit power of the source was50kA under 31kV.
TRV HV Circuit Breakers P 151
• During the general meetings of CIGRE, SLF was first mentionedduring the session of 1958.
Two reports were presented during the CIGRE session of 1960 (byFrance and Switzerland).
• IEC introduced for the first time short-line-fault (SLF) requirementsin 1971.
• SLF TRVs were introduced also in ANSI/IEEE C37.072 in 1971.
Introduction
TRV HV Circuit Breakers P 152
• The requirement of a SLF interrupting capability had and still has agreat influence on the design of high-voltage circuit breakers.
It was already the case with air blast type that had to be fitted withopening resistors for SLF interruption.
• SLF is also a critical test duty for SF6 type circuit breakers.
Sufficient pressure build-up and mass flow rate are necessary for SF6circuit breakers to interrupt at current zero.
Introduction
TRV HV Circuit Breakers P 153
• Short-line faults occur from a few hundred meters up to severalkilometers down the line.− L90: short-line fault with 90% of rated short-circuit current− L75: short-line fault with 75% of rated short-circuit current
• After current interruption, the line-side voltage exhibits a characteristictriangular waveshape.
line
Circuit breaker
Short-Line-Fault (SLF)
U
TRV, neglecting the contribution from the supply-side
TRV HV Circuit Breakers P 154
• The circuit-breaker interrupts the current, at a passage through zero,the supply voltage and the di/dt are both maximum (in amplitude). Thevoltage on the circuit-breaker terminals (U0) is a fraction of the supplyvoltage Us0.
line
Line sideVoltage (point C)
Supply sideVoltage (point B)
At the time of interruptionUs0 = (LS + LL ) di/dt
U0 = LL di/dt
where di/dt is the current derivative at current zero
Example Ur = 245kV
LLLS
Us0
U0
U0
kVUUL
kVUU
s
rs
20100901:90
2003
2
00
0
Short-Line-Fault (SLF)
TRV HV Circuit Breakers P 155
• As the TRV is at high frequency, the line must be treated as atransmission line with distributed elements.
• The line side voltage oscillates as travelling waves are transmitted withpositive and negative reflections at the open breaker and at the fault,respectively.
Short-Line-Fault (SLF)
After current interruption
The supply voltage varies much more slowly than the line-side voltage
The TRV is mainly due to the voltage variation on the line side.
Supply sidevoltage (point B)
Line-sidevoltage (point C)
TRV HV Circuit Breakers P 156
• Supply-side and line-side voltages
Um: supply voltage at the time of interruptionUo: voltage on circuit breaker terminals at the time of interruptionExample L75: Ur = 245kV : Um= 200 kV, Uo= 50 kV, UL= 80 kV
Current
Supply-side voltage
Line-side voltageUo
Um
U = 0UL
t
t
Short-Line-Fault (SLF)
TRV HV Circuit Breakers P 157
SLF / Evolution of Line Voltage
Voltage profile at current zero (t=0), Voltage decreases linearly towards 0 at the fault pointIt is considered to be sum of two voltage waves moving in opposite directions.TL = Travel time for wave to travel from one end of line to the other and back.
TRV HV Circuit Breakers P 158
Traveling waves thatreach the fault point arereflected with an oppositepolarity.
Traveling waves thatreach the open point, atthe circuit breakerterminal, are reflectedwith the same polarity.
Voltage at any locationon the line is the sum ofeach component.
SLF / Evolution of Line Voltage
TRV HV Circuit Breakers P 159
SLF / Evolution of Line Voltage
TRV HV Circuit Breakers P 160
Voltage on the line after current interruption
SLF / Evolution of Line Voltage
Voltage at circuit-breakerTerminal x = 0
Voltage half-wayto the fault x = 0.5 L
Voltage at x = 0.75 L
TIME
VOLTAGE (p.u.)
0
2
- 2
tL0.5 tL tL/4 3 tL/4 1.5 tL
TRV HV Circuit Breakers P 161
Voltage on Circuit Breaker line-side terminal
-1,5
-1
-0,5
0
0,5
1
1,5
0 0,25 0,5 0,75 1 1,25 1,5 1,75 2
Line side Voltage(p.u.)
Time / TL
SLF / Evolution of Line Voltage
Damping is neglected, in practice at time TL voltage is -0.6 to -0.8 p.u.
TRV HV Circuit Breakers P 162
Supply voltage
Line voltage
TRV
SLF TRV
Voltage (kV)
Time (µs)
TRV HV Circuit Breakers P 163
SLF / RRRV
• The rate-of-rise of recovery voltage (RRRV) on the line side is function of the slope of current before interruption and of the surge impedance of the line:
Z is the surge impedance of the line (450 ohm)
L and C are respectively the self inductance and the capacitance of the line per unit length
I fault current (kA)
ω pulsation
s multiplier = 0.20 (f = 50Hz) or 0.24 (f = 60 Hz), du/dt in kV/µs
CLZ
IsIZdtdiZ
dtduRRRV 2
6102.0250 ZHzat
TRV HV Circuit Breakers P 164
SLF / Line Surge Impedance
• Assumptions: conductors of infinite length, the electrical field and magnetic field do not penetrate the ground.
• Self surge impedance D = 2 h with h = height of line r = radius of conductorLn = natural logarithm µ0 = magnetic constant = 4π×10−7 H/m
= electric constant = 8.854×10−12 F/m
with (1)
• Mutual surge impedance (ZM) between 2 conductors is given by (1) where D isthe distance between one conductor and the image of the other conductor, and rrepresents the distance between the two conductors (see next slide).
• A matrix equation is done in case of multi-conductors circuits with self andmutual couplings. Modal analysis done by digital calculations gives the relevantmodes of travelling waves (see Annex C in [39] and [47]).
rhLn
rDLn
CLZ 26060
TRV HV Circuit Breakers P 165
SLF / Line Surge Impedance
• Distances to consider for mutual surge impedance calculation
d12
D12
Ground
Image of bundle of conductors 2
Bundle 1
Bundle 2
Bundle 3
12
1212 60
dDLnZM
TRV HV Circuit Breakers P 166
SLF / Line Surge Impedance
• Factors that influence the surge impedance− Geometry of a conductor
− Arrangement of the conductors in relation to the towers and the ground(single or double circuits..)
− Frequency of the TRV: Z decreases by 4% when the frequency increasesfrom 1 to 100 kHz.
− In case of bundled conductors, they can clash if the current is high enough.The surge impedance is higher after conductor clashing and reach thevalue for a single conductor: 450 Ω.
− Line height: the surge impedance of lines increases with the conductorheight above ground.
− Earth resistivity: the surge impedance increases by 5.7% at 1kHz and3.2% at 100 kHz when earth resistivity changes from 10 to 1000 Ω-m.
− Tower footing resistance: if it rises from 0 to 10 Ω the surge impedanceincreases by about 2%.
TRV HV Circuit Breakers P 167
Short-line-fault
• Percentage of SLF (or M)
S
LGS X
VI LS
LGL XX
VI
TRV HV Circuit Breakers P 168
• The transmission line parameters are given in terms of the effective surge impedance ( Zeff) of the faulted line and a peak factor (d)
XL is the line reactance per unit lengthv is the velocity of light (0.3 km/µs), is the line length is 2 system power frequency (314 or 377 rad/s for 50 or 60 Hz)
vXZ
dL
eff2vdtdiZu effL /2/
2LLo IXu
uLuO
O
L
uud
Short-line-fault
TRV HV Circuit Breakers P 169
SLF / Voltage at Current Zero
U0
SSL
LS
S
SL
SSS
LL
XMXXMorXX
XM
IMIIXUIXU
0
SSS
SSS
SL
UMIXMUIXMXU
IMXU
110
0
0
SUMU 10
US
TRV HV Circuit Breakers P 170
• The rated values for the line surge impedance Z and the peak factord are defined in standards as follows:
• The line side voltage contribution to TRV is defined as a triangularwave as follows (where IS is the rated short-circuit current) :
the first peak UL decreases when M increasesthe rate-of-rise of recovery voltage increases with M
• There is a critical value of the short-line-fault current for which thecircuit breaker has more difficulty to interrupt.
• The critical value of M is close to 90% for SF6 circuit breakers(generally in the range 90%-95%). it is between 75% and 80% forair blast circuit breakers.
rL UMU32)1(6.1
6.1/450 0 UUdZ L
2SIMZdtdiZ
dtdu
SLF / Line-side Contribution to TRV
TRV HV Circuit Breakers P 171
• The following Table gives the comparison of current and voltagestresses during test duties L90 and L75, respectively at 90% and 75%of rated short-circuit current, for a circuit-breaker 245kV 40kA 50Hz.
• The current and RRRV are higher during L90, but the (first) peakvoltage is higher during L75.
• In practice, L90 is usually the most severe test duty.
RRRV: rate of rise of recovery voltage UL= first peak voltageVoltage on the line side only is considered
L90 L75
Current (kA) 36 30
RRRV (kV/µs) 7.2 6
UL (kV) 32 80
Short-line-fault
TRV HV Circuit Breakers P 172
Ur = 245kV
Isc = 40kA
fr = 50Hz
0
20
40
60
80
100
120
140
0 5 10 15 20 25 30 35
T (µs)
U (k
V)
7.2 kV/µs
6 kV/µs
4.8 kV/µs
L90
L75
L60
When current decreases (longer line), the slope decreases but the peakvalue increases. It is generally considered that for SF6 circuit breakersinterruption is more influenced by the voltage slope (RRRV).
SLF / Comparison of Test Duties
TRV HV Circuit Breakers P 173
• The TRV seen by the circuit breaker is the sum of a contributionfrom the line side (eL) and a contribution from the supply side (eS):
with (in a first approximation)
where
2 M = RRRV (T100) x M = 2 kV/µs x M
TL is the time to peak of the line side TRV
td is the time delay of TRV on the source side
SL eee
)(2 dLS tTMe
Short-line-fault
TRV HV Circuit Breakers P 174
• Example of calculation of SLF TRV : L90 245 kV 50 kA 50 HzFault current = 0.9 x 50 = 45 kA (assuming time delay tdL= 0 µs)
Short-line-fault
TRV HV Circuit Breakers P 175
• This rate-of-rise of TRV during SLF is much higher than the valuesthat are met during terminal fault interruption:
Test duty RRRV (kV/µs)
I(kA)
F(Hz)
SLFL90 50 kA 10.8 45 60
SLFL90 50 kA 9 45 50
SLFL90 40 kA 8.64 36 60
Terminal faultT60 3 30 50/60
Terminal faultT100 2 50 50/60
For SLF, this table gives the RRRV of the line side voltage
Short-line-fault
TRV HV Circuit Breakers P 176
• Standard values of lines characteristics for SLF
SLF / Line Characteristics
IEC values are shown, ANSI/IEEE values cover rated voltages up to 800kV
TRV HV Circuit Breakers P 177
Short-Line-FaultInfluence of an Additional Capacitor
TRV HV Circuit Breakers P 178
• The SLF performance can be increased by adding a capacitor, either between terminals or phase to ground (see figure).
• A capacitor has two effects:− it decreases the oscillation frequency and the RRRV of the line
side contribution to TRV;− it increases the time delay of the line side contribution to TRV.
VLG
XS XLC.B.
SLF / Influence of an Additional Capacitor
TRV HV Circuit Breakers P 179
(f ile t r v2 .pl4 ; x- var t ) v :P 0 0 v :P 1 v :P 4 v :P 1 0 0 4 8 1 2 1 6 2 0[ u s]
0
1 0
2 0
3 0
4 0
5 0
6 0
[ kV ]
TRV without capacitor
TRV with capacitor(capacitance increase from 1 to 3)
1 2 3
SLF / Influence of an Additional Capacitor
TRV HV Circuit Breakers P 180
− Equation of the line-side contribution to TRV up to the first peak:
− If the capacitor is connected phase to ground on the line side, the reduction of the line side RRRV can be estimated by a simple calculation, as detailed in the next slide, withCadd additional line-to-ground capacitance;
L line inductance;
Z line surge impedance;
CL total line capacitance = L/Z2;
Ce equivalent line capacitance: capacitance which, together with the inductance L, gives the line frequency of oscillation
CZteCZCZtdtdiZte /)/()(
SLF / Influence of an Additional Capacitor
TRV HV Circuit Breakers P 181
− By definition of Ce
− The period of oscillation is equal to with
and
− It follows that
and
If an additional capacitance is added at the line entrance, the RRRV on the line side is reduced in the same manner as the line frequency of oscillation.
eL LC
f2
1
L
L
dtduu
*2 22*LLL IXu
2LL
IZdtdu
LL X
Zf4
LL
e CCZ
LC 4.044222
SLF / Influence of an Additional Capacitor
TRV HV Circuit Breakers P 182
− The RRRV on the line side is then
)(22
adde
eL CCL
LCIZ
dtdu
adde
eL CC
CIZ
dtdu
addL
LL CC
CIZdtdu
5.22
SLF / Influence of an Additional Capacitor
TRV HV Circuit Breakers P 183
Short-Line-FaultInfluence of an Opening Resistor
TRV HV Circuit Breakers P 184
SLF / Breaking with Opening Resistor
• Some circuit breakers, mainly air-blast, have an opening resistor to assist a short-circuit interruption.
• It was introduced to improve the SLF breaking capability of air-blast circuit breakers, but it has been used also to facilitate the interruption of fast TRVs by some SF6 circuit breakers.
TRV HV Circuit Breakers P 185
SLF / Breaking with Opening Resistor
• In case of SLF, the RRRV (or du/dt) is modified as follows:
where R = value of opening resistor
Z = line surge impedance
I = short-circuit current
2IRZRZ
dtdi
RZRZ
dtdu
TRV HV Circuit Breakers P 186
• Very fast RRRV (rate-of-rise of recovery voltage)− Product of fault current derivative by surge impedance− Standard value of surge impedance = 450 Ω
• Triangular waveshape due to travelling waves• Test duties L90 and L75 (+ L60 is some cases)
− Single-phase tests that cover all SLF conditions• SLF performance improved by
− additional capacitor (or opening resistor)
Short-Line--Fault TRV / Summary