VIABILITY OF PERMANENT SINGLE-PHASE OPENING OF LINES IN EXTRA HIGH VOLTAGE SYSTEMS PART I – SECONDARY ARC EXTINCTION F. A.T. Siha, Memb er IEEE J,A, Jardini, FellowMember IEEE e-ma ll fat s@!peauspbr e-mad Jarduu(j pea,usp.b r University of S50 Paulo Av, Prof. Luci ano Gualberto, 158 – trav.3 05508-900 – S2io Paulo, SP, Brazil A bs tr act : T his p ap er d is cu ss es th e v ia bil it y o f p erma nen t s in gl e- phase opening of lines in extra high voltage systems as a system planning criterion. To apply such criterion it is necessary that : (i) the secondary arc that appears after a single-phase fault clearing is quenched; (ii) after a single-phase opening, the current u nbalances of negative and zero sequence in the electric system are compensated. Power electronics are used to meet targets . Only the secondary arc extinction condition is analyzed in this part. Key words: si ngle-phase opening, secondary arc, unbalances I. I NTR OD UC TI ON The most common practice when a fault in a transmission l in e c au se s i ts t ri pp ing i s t he thr ee -p ha se o pe ni ng , e ve n i f t he problem is in one phase only. Once the fault is eliminated, the line reclosure occurs after a certain dead time when the extinction of the se condary arc current is expected. I f t he re a re mu lt ip le c ir cu it s i n a s ec tion a nd the p er ma ne nt fault is in one phase, there is no interruption in the flow of tran:jmitted power even when the three phases are opened. However, there will be a reduction o f the t ra ns mi tt ed p owe r during a the initial period after the line opening. This situation is even more critical when there is only one circuit, between section , becau e the three-phase opening will interr upt the power fl ow completely. The single-ph se opening can thus be seen as a way to minimize this problem, since most faults in Extra High Vo lt age (EHV) li nes are of single-phase type. However, the arc extinction conditions are mor critical at the single-phase opening than at the three-phase opening. In the latter there will be arc current due to oscillations of the t ra pp ed cha rg es in t he l in e c ap ac it an ce s wi th t he ir r ea ct or s; these oscillations decrease over the time. In single-phase opening, voltages in untripped phases may m intain the secondar y arc in values above the extinction li mit. If th permanent single-phase opening is chosen (a pra ct ice not fully established), t e load flow disturbance is smaller than three-phase opening; therefore, more favorable for the system stability. On the other hand, in the permanent single-phase opening, there will be distortions in the system (upstream and downstream the disconnected line), where n eg at iv e a nd z er o s eq uenc e cur re nt a nd v ol ta ge c omp on en ts will appear. The zero sequence components are b ocked in AY transformer; however, they might interfere in the protection s ys te m. T he n eg at iv e s eq uence c omp on en ts p as s through to generators and loads being responsible some ti mes for undesired heating at the machines that may be disc onnecte d by negative sequ ence protections. As a conclusion, there are two aspects to be considered in the use of a permanent single-phase opening (with or without recl osingj: (i) the extinction of the secondary arc in the faulty phase (even Z~ there is no reclosing), and (ii) the el imination of current dist or tions downstream and upst ream the faul ted line. 0-7803-5938 -0/00/$10.00 (c) 2000 IEEE
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Viability of Permanent Single Phase Opening of Lines in Extra High Voltage un s. Paulo
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8/3/2019 Viability of Permanent Single Phase Opening of Lines in Extra High Voltage un s. Paulo
‘Thisarticle discusses a methodology for the compensation
of the arc current. The compensation I minimization of the
distortions in the system upstream and dowmtrea~ the
disconnected line is discussed in another article pI also by the
use of Power Electronics.
‘This cmnpensation of the secondary arc k obtained by
inserting a voltage source in the reactor, in the same phase as
the faulty phase. This source is constituted by a capacitor and
power transistors, thus providing the control of the moduleand phase angle of generated voltage.
‘The simulations here reported were performed using the
ATP Alternative Transient Program. The test system has
similar characteristics to the real 6300 MV& 765 kValternating current (AC) system transmission from Itaipu to
Siio PauI~ Brazil, with”a detaded representation of the-first
section with an approximate length of310 km. An equivalent
impedance represents the two remaining sections and the
receiving system (Fig. 1).
IL FAULT AND ARC EVOLUTION
To have the phenomenon described, the following aspects
were considered:
- Singte-phase fault in bus B after 100ms steady state pre-fault condition;
- Single-phase opening (BI-B3) 50 ms after the fault
initiation, remaining the connection to earth in B;
- Elimination of the connection to earth in B, after 1000 ms
of the fault initiation instant;
The current value from B to earth is shown in Fig. 2 and
the voltage in B is shown in Fig. 3. The single-phase to earth
current peak r-s 16M* being high until the opening of
the circuit breakers at both ends of the faulty line. As fromthis instant there is still current from B to earth with muchlower level, the secondary arc. This swomlary arc current
results from the coupling of the sound phases with the faulty
phase and the transient of trapped charges at line
capacitances at the instant of the circuit breakers opening.
When the secondary arc extinguishes, a recovery voltage in
the faulty phase appears (Fig. 3). If this voltage is high the
arc regnishes.
*From this point ahead kV and A refer topeak values
D & ~>
-&l--+G’
a) Steadystate and short circuit– Oto 200 ms
‘ltl,
300 I
, “
‘I*,,!-..)m
1- ‘--,00
.,-
b)With uhme A of B1-B3 owned – 200to 1500~s.
Fi& 2. Clnnmt tiwmB to earth- single-phase fault am!s@le-phase opening
arc regnishes.
Note that this phenomenon is repeated at all arc current
crossing zero until extinction takes place, In Fig. 2 an arc
extinction was assumed at the instant 1100ms.
Fig. 4 shows the area as related to arc current and recove~
voltage, where the arc extinguishes [2].
III. TRANSIENT STADILI~Y
It is desired to comnare the effect in the system when a
single-phase or a three~phase breaker opening is adopted.
Therefore, the verification of influences of these types of
openings in power oscillations (transient stabili~), shall be
evaluated with proper program, However, a first insight can
“ ,,”,
O!---6,,
4,0
,00
20”
<“”
,0” J
r“-” ,..1Fig.3. Phaseto earth voltage at bus B
0-7803-5938-0/00/$10.00 (c) 2000 IEEE
8/3/2019 Viability of Permanent Single Phase Opening of Lines in Extra High Voltage un s. Paulo
[3]O. A. Ciniglio and D. P. Carroll “Improved power transfer during single
pole switching a symmetrical sequence filtering approach.” IEEETransactions on Power Delivery, v.8, n.1, p. 454-460, January
1993.
[4] E. W. Kimbark, “Suppression of ground-fault arcs on single-pole-switched EHV lines by shunt reactors”. IEEE Transactions onPower Apparatus and Systems, v.83, p, 285-290,March 1964.
[5] B, R. Shperling, A. Fakheri, and B. J, Ware. “Compensation scheme for
single-pole switching on untransposed transmission lines”. IEEE
Transactions on Power Apparatus and Systems, v.97, n.4, p.
1421-1429,July/August 1978.
[6]N. Knudsen “Single-phaseswitchingon transmis~ionlines using reactors
for extinction ofthe secondaryarc”, CIGRE, Report 310,1962.