Examples Ferroresonance in High Voltage Power System: N. Jacobson, Membec IEEE
Examples Ferroresonance in High Voltage Power System: N. Jacobson, Membec IEEE
Examples Ferroresonance in High Voltage Power System: N. Jacobson, Membec IEEE
I. INTRODUCTION
OUCHEROT [2] originally coined the word ferroresonance In 1920 to describe the phenomenon of two stable
fundamental frequency operating points coexisting in a series
resistor, nonlinear inductor, capacitor circuit. The first
published work, a 1907 paper by Bethencd [I], simply
described the phenomenon as transformer resonance. Today,
the term ferroresonance is firmly established in the power
system engineers vocabulary and is used to not only describe
the jump to a higher current fundamental frequency state but
also bifurcations to subharmonic, quasi-periodic and even
chaotic oscillations in any circuit containing a nonlinear
inductor.
A special publication is being prepared by the Practical
Aspects of Ferroresonance IEEE Working group. One of the
tasks of the Working Group is to provide a comprehensive
survey of the ferroresonance issues reported in the literature.
To date, 129 papers have been reviewed and categorized as
practical. The following categories or classes of ferroresonant
circuits have been reported:
1. Transformer supplied
accidently on one or two phases (39
..
papers) [31-[51,
2. Transformer energized through the grading capacitance of
one or more open circuit breakers (25 papers) 161, 171,
3. Transformer connected to a series compensated transmission line (15 papers) [8], [9],
4. Voltage transformer connected to an isolated neutral system
(14 papers) [IO]-[131,
5. Capacitor voltage transformer (11 papers) [14], [ H I ,
6. Transformer connected to a de-energized transmission line
running in parallel with one or more energized lines (6
papers) U61, 1171,
7. Transformer supplied through a long transmission line or
@mail: dajacobsanehydro.mb.cu).
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B. Description of Disturbance
The Dorsey HVdc converter station 230 kV ac bus is
comprised of four bus sections on which the converter valves
and transmission lines are terminated. At 22:04, May 20, 1995,
bus A2 (Fig. I ) was removed from service to commission
replacement brcakers, current transformers and to perform
disconnect maintenance and trip testing. At approximately
22:30, a potential transformer (V13F) failed catastrophically
causing damage to equipment up to 33 m away. The switching
procedure resulted in the deenergized bus and the associated
ITS being connected to the energized bus B2 through the
grading capacitors (5061 pF) of nine open 230 kV circuit
breakers. A station service transformer, which is normally
connected to bus A2, had been previously disconnected. A
ferroresonance condition caused the failure of the IT.
I .n
Time (sec.)
0.0
0.0
0.2
0.n
0.6
i i m e (sec)
0.8
1 .o
D. Mifigation Options
Revised manual bus clearing guidelines were implemented to
reduce the risk of ferroresonance by minimizing the grading
capacitance coupling the two buses. Disconnects on all but two
breakers are opened thus limiting the maximum grading capacitance to 1500 pF. Damping resistors are not required in this
case if the SST is in-service.
grading
equivalent source:
Z , = .212+j4.38.n
(12wO MVA)
p:?
(325-75rXIpF)
.....
ac filters
.....
BI
[ V13F
[ V33F
stray capacitance
14mOPFI
AI
C. Typical Oscillations
"."
....._I-.,
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D. Mitigution Options
Since the May 20, 1995, destruction of wound potential
transformer V13F 141, all wound potential transformers of
concern at the Dorsey Station have been replaced with
capacitor voltage transformers. Permanently connected 200-R
loading resistors are installed on the 4.16-kV secondary bus of
station service transformers SSTl and SST2.
The manual de-energizing operating procedure described
earlier in the paper is no longer required with the addition of
loading resistors and replacement of wound PIS.
grading
A2
(a)
B2
capacitance
B2
B2b
1.44 pu
B20
bus capacitance
mavlr
x,= 12.2%
?C?!P.N
(h)
1.04 pu
suay capacitance
(6003 PF)
Xo= 10.9%
A2b
iron-core
loss model
Fig. 4.
mzb
..... 200 n
R,
R m=
=~312'
.11 M R
'Wp
R, = 2.4 Cl
Z b = 10.124+j1.620R
Fig. 5. Single-line diagram of the Augllst 5. 1995, Dorsey dismbance showing (a)
main circuit components and (h) model of station service msfomer.
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B. Nehvork Parameters
A typical 33 kV or 66 kV station single line diagram with
two radial feeders is shown in Fig. 8.
The critical elements IO be modeled are:
potential transformer (F'I)
* stray capacitance
* grounding bank (GB)
The purpose of the GB is to provide zero sequence current
during single line-to-ground faults for ground fault protection
relays to operate. The open-delta 'I
serves
'
as a backup to
allow the GB to be taken out-of-service for maintenance.
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D.Mitigation Options
There are several possible solutions. Crane and Walsh [ I l l
recommend one of the following:
1. replacing ITS with capacitive coupled voltage
transformers (CCVTs).
2. installing FTs that are rated for line-to-line system
voltage. Minimal saturation occurs during ground faults, thus
limiting the susceptibility to ferroresonance.
3. installing a resistor in the broken-delta. The paper
discusses a calculation method. A 3 ohm resistor (43 kJ) was
recommended for their application. Under worst case
conditions, up to twice rated current could flow in the PT.
However, the IT is designed to handle twice rated current for
up to 30 seconds which is must greater than a typical fault
clearing time of I second. The damping resistor is expected to
eliminate any ferroresonant oscillations within 0.1 to 0.2
seconds.
Ritz instrument transformers recommend installing an
inductor in parallel with a resistor. The inductor is used to
eliminate subharmonic oscillations and the resistor is used to
damp period-l ferroresonance. It's not clear what thermal
rating corresponds to each I T they discuss, however, the
damping resistors are in the range 500-2000 watts with a 5
second rating (IO kJ max).
Damstra [I21 also recommends a saturable reactor-resistor
scheme. At KEMA labs in the Netherlands, several Holec ITS
in the 50, 100 and 150 kV classes were tested. The saturable
reactor tended to eliminate subharmonic modes and a 50-100
ohm resistor eliminated period-1 modes of ferroresonance.
Van Craenenbroeck ef al. [I31 are investigating modern
techniques of analysis and their application to a 6.6 kV
ungrounded network. Energizing the PT through a cable feeder
could excite ferroresonance oscillations. Their analysis
techniques can determine a minimal value of damping
resistance.
For typical 33 kV and 66 kV delta stations, Manitoba Hydro
installs ballast resistors across the open-delta of all ITS and
installs grounding banks. The ballast resistor has a power
rating of 25%. Specialized studies are used to determine
appropriate ferroresonance mitigation when the stray
capacitance becomes excessive (i.e. due to underground
cables).
V. CAPAClTOR VOLTAGE TRANSFORMER
A. Network Problems
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WI.
Specialized equipment may require more stringent specifications than CSA. For example, a CVT used for voltage
measurement at an SVC terminal may he required to damp
transients within 2 cycles (151. Because of the deviation from
the actual commutating bus voltage, only wound PTs are
permitted to he used for valve timing at Manitoba Hydro's
HVdc converter stations. High speed protective relays can be
impacted by the transient response which can cause
overreaching, underreaching or directional errors 1271.
Nonlinear burdens such as auxiliary potential transformers
can impact the CVT. For the circuit shown in Fig. 10, a
230230 volt auxiliary PT is chosen in the 115-volt circuit to
avoid any problems. Smaller auxiliary W (i.e. 115:115 volt)
have gone into ferroresonance before the intermediate
transformer leading to overvoltages and protective gap
flashovers.
00
02
04
06
08
10
Time (s)
I
(b)
-0.6f
0.0
B. Network Parameters
-0 6
I,
0.2
,
0.4
0.6
0.8
10
Time (s)
Simulations of a ferroresonance test (i.e. secondary shortcircuit test) for the circuit in Fig. IO is given in Fig. 11. The
impact of the ferroresonance suppression circuit (FSC) is
clearly seen.
D.Mitigation Options
Manufacturers are aware of the ferroresonance problem and
install various types of suppression circuits. The FSC shown in
Fig. 10 has a constant burden and a saturable reactor. Tuned
RLC filters are also used but this type of circuit affects the
frequency response of the CVT. Special arrangements of triacsl
spark-gaps can he used to achieve ferroresonance suppression
within 2 cycles.
seriesreaclnr
capacitors
drain coil
(used with
I
Fig. 11, CSA femmnance test campmison with, (a) ferrorcsomoee suppression
circuit (FSC) enabled and with, (b) FSC disabled.
VI. CONCLUSIONS
Four examples of circuit configurations that can experience
ferroresonance have been presented. The impact of ferroresonance can vary from relay or control misoperation to
catastrophic equipment failure. By being aware of the various
situations where ferroresonance can occur, appropriate
mitigation strategies can be designed before equipment is put
into service and problems develop.
As the first two examples show, an innocent circuit breaker
replacement project created a ferroresonance situation where
there was none prior. Advances in circuit breaker interrupting
medium technology led to an effective increase in the amount
of grading capacitance connected to a de-energized voltage
transformer and station service transformer. Loading resistors
and replacement of the voltage transformers with capacitor
voltage transformers were required to mitigate the problem.
Open-delta voltage transformers are well protected with
loading resistors across the open delta or by nearby grounding
transformer hanks in most situations. However, high values of
capacitance due to the presence of underground cables requires
special studies to determine if additional facilities are required
to mitigate ferroresonance.
Capacitor voltage transformers are protected by ferroresonance suppression circuits installed by the manufacturer.
Depending on the application, high speed suppression of the
transient ferroresonant oscillations may he needed, which
requires a more sophisticated FSC.
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V11. REFERENCES
111
I21
[31
141
151
161
171
181
,91
.1101.
Ill1
1121
1131
I141
I151
1161
[I71
1181
1191
1201
1211
Bethenod. 1.. "Sur le Transformateur A Resonance". L ' t c l a i r m e Electrique, vol. 53. NOV.
30. 1907, pp. 289-96.
Bouchemt. ,P.."Existence de Deux Regimes en Ferrar6sonance". Reii
Gen.de ~ ' E f e ~ . , v 8.o lno.
. 24, December 11, 1920. pp. 827-828.
Hopkinson, R.."Fcrroresonant overvoltage control based on TNA tests
an three-phase delta-wye transformer banks". IEEE Trans. on Power
App. & Systems, Vol. 86, No. IO. pp. 289-293, Oct. 1967.
Young, F.. Schmid. R.. Fergestad. P.,"A lab~mloryinvestigation o i ferroresonance in cable-connected transformers'', IEEE Trans. on Power
App. & Syrtems. Vol. 87, No. 5,pp. 1240-1249. May 1968.
Walling. R.. Barker, K.. Compton. T.. and Z i e n n a n , L.,"Ferroresonant overvoltages in grounded wye-wye padmount transformers with
low-lass silicon Sled cores". IEEE Trons. on Power Deliverv, Val. 8. No.
3, pp. 1647.1660, July 1993.
Jacobson. D.A.N.. Swutek, D.. and MZUL R.. "Mitigating
. .Potential
Transformer Fenoresananee in a 230 kV Convener Starion". Computer
Analysis of Electric Power System Transients: Selected Readings, IEEE
Press: Fiscatawuy, N.J.. 1997. pp. 359-365.
Jacobson. D.A.N., and Menzies, R.W.,"Investigation of Station Service
TransformerFerroresonance in Manitoba Hydro's 230-kV Dorsey Convener Station". Proceedings of the 2001 Intl. Con$ on Power Systems
Transients, June 24-28, Rio de J ~ K ~ o .
Wwdford, D.A.."Solving the ferroresonance problem when COmpenSating a dc convener station with a series capacitor", 1995 IEEUPES Summer M e l i n g , paper 95 SM 528-0 PWRS.
P,M,, and
R,G,. Series Compensation ofpower sys.
tems. PBLSH!. pp. 325-328, 1996.
Shntt. H.S.. and Peterson.. H.A.."Criteria
for neutral stahilitv of wve.~
gr0unded.pri-y
bmken.d&.=condary
uansformercircuits',, rmns.
actionronAIEE, Vol.6O.pp.997-1002. 1941
Crane, D.R., and Walsh, G.W.,"Large Mill Power Outages Caused by
Potential Transformer F K X O ~ ~ S O ~ ~IEEE
K C "Trow.
,
on Industrial
Application?, Val. 24. No. 4, pp. 635-640, JulyIAug. 1988.
Damstra. G. C.,'Ferroresonance in Gas-Insulated Substation Voltage
Transformers". Power TKChnOlOgy Intematianal, pp. 87-91, 1994.
Van Craenenbraeck. T.. Van Dammelen, D., Janssens, N.. "Damping
circuit design far fKrr0reSonance in floating power systems", European
Transactions on Electrical Power (ETEP),Vol 10 nD 3, Muyllune ? O W .
Bolduc, L., Bouchard. B., and Beaulieu, G.,"Capacitor divider substation", IEEE Tram. Power Deliver): Val. 12, No. 3, pp. 1202-1209, July
1997.
Iravani, M.R.. Wang, X.;Polishscuk. I., Ribeim, J., Sarshar, A.."Digital
Tme-Domain Investigation of Transient Behaviour of Coupling Capacitor Voltage Transformer", IEEE Tram. on Power Deliverv, Vol. 13, No.
2 pp. 622-629, April 1998.
Brierlev. R.H.. Morched, A.S., and Grainger. T.E.."Commct
. right-of.
ways with multi-voltage towers", IEEE Trons. on Power Deliwry, Vol.
6.No.4.p~. 1682-1689,Oct. 1991.
Jacobson, D.A.N., Mani. L.. and Menzies, R.W.."Modelling ferroresonance in a 230 kV transformer-terminated double-circuit transmission
line". Pmc. of the 1 9 9 h r l . Coni on Power System Tranansients (IPST).
pp. 451-456, June 1999.
Gish. W.B., Feero, W.E., and Greuel, S.,"Ferroresonance and loading
relationships for DSG installations', IEEE Tram. on Power Deliver),
VOI. 2, NO. 3, pp.953-959, JUIY 1987.
Dick, E.P., Gupta B.K., Poner, J.W.. Greenwood, A.,"Practical design
of generator suge protection", IEEE Trans. on Power Delivery, Vol. 6,
No. 2,pp. 736743. April 1991.
Kieny, C.,"Application of the bifurcation theory in SNdying and understanding the global behavior of a fcrroresonant electric power circuit".
IEEE Tron~.on Power D d i w r y , Vol. 6. No. 2. pp. 866-872, April 1991.
Shon, T.. Burke. I., Mancao, R.,"Application of MOVs in the distribution environment", lEEE Trans. on Power Delivery, Vol. 9 No. 1, pp.
293-305. Jan. 1994.
~
~~~
1231 Mark, B.A.. Morched, A.S., and Walling. R.,"Mcdeling and Analysis
Guidelines for the Investigation of Slow Transients in Power SystemsPan Ill:SNdy of the Phenomenon of Ferroresonance". Slow Transients
Task Force of IEEE Working Group on Modeling and Analysis of System Transients Using Digital Programs, IEEE Tranr. on Power Delivery,
Vol. 15, No. 1, pp. 255-265,Jan. 2000.
1241 ANSlnEEE C37-011-1979. Application Guide for Tmnnsient Recovery
Volrogefor AC High Voltags Circuit Breakers Rated on o Symmerrical
Current Bar1.V.
1251 CSA Standard CAN3-C13.1-M79. Capacitor Voltage Transformers.
March 1979.
1261 ANSIINEMA C93.1, Requirementr for Power-Line Carrier Coupling
Capacitors and Coupling Capacitor Voltage Tronfomers ( C C W J .
May 1999.
IEEE Committee Repon,"Trannsient Response of Coupling Capacitor
Voltage Transformers". Working Group of the Relay Input Sources Subcommittee of the Power System Relay Committee", IEEE Trans. on
PowerAppSysi., Vol. PAS-100, No. 12, pp.4811-4814. Dec. 1981.
VIII. BIOGRAPHlES
David A. N. Jacobson (S'84-M'W) received the B.Sc. degree in electrical
engineering (with distinction) and the MSc. and Ph.D. degrees fram the University of Manitoba Winnipeg. MB. Canada, in 1988. 1990, and 2000 respectively. He joined Manitah Hydro. Winnipeg. in 1990. where he i s currently the
Interconnections and Grid Supply Planning Engineer. He was a visiting
researcher with the Siemens Power System Planning group in Erlangen. Germ a w in 1994. His research interests include nonlinear dvnamics.. mwer
svsr
tem~&Zrol and FACTS devices. He is active in CIGRE Study Committee k6
Distribution Systems and Dispersed Generation. Dr. Jacobson has been a registered Professional Engineer in the province of Manitoba since 1992.
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