2007 IEEE Canada Electrical Power Conference

Control and Protection of Distribution Networkwith Non-Utility Induction Generators

Hamidreza Bakhshi*l, Innocent Kamwa*2*]SNC-Lavalin T&D Inc.,

25th Floor, 41J-Jst Street S.E., Calgary, AB, Canada, T2G 4Y5Hamidreza.Bakhshi@snclavalin.com

*2Hydro-Quebec (IREQ),1800, Lionel-Boulet, Varennes, QC, Canada, J3X IS]

Kamwa.innocent@ireq.ca

transient stability program. In [8] the focus was to examine theAbstract-In this paper, some topics related to the dynamic induction generator's parameters influence using the

simulation and operations of Non-Utility Induction Generation PSCAD-EMTDC power systems electromagnetic transients(NUIG) are investigated. Various technical aspects related to the program. In the present work, the ElectroMagnetic Transientnetwork conditions were analyzed mainly by computersimulation cofnadistributionswere anetw d mainUI uni concted Program - Restructured Version (EMTP-RV) software is usedsimulation of a distribution network and NUIG units connected tor-xmnthsefxcainpeoeonnteilndgto it. The applied simulation tool was EMTP-RV, which is a to re-examine the self-excitation phenomenon in the islandingcommercial electromagnetic transient simulation program. condition with the same terminology as [7]. Based on the

This paper presents the guidelines to limit the self-excitation results, practical guidelines have been derived to limit thisphenomenon of NUIGs in islanding conditions and proposes phenomenon. It also proposes proper relay schemes forproper protection schemes for interconnection of NUIGs to the interconnection ofNUIGs to the distribution networks.distribution networks.

2. SYSTEM DESCRIPTION AND MODELING ASPECTSKeywords-Induction generator; dynamic simulation;

self-excitation; islanding; relaying; NUIG; NUG; EMTP-RV. Figure 1 shows the single line diagram of the studied 25 kVsystem as topology 1 (TOP1) with the same system parameters

1. INTRODUCTION as described in [7]. Modified system (TOP2) has been derivedrJ1He phenomenon of self-excitation of induction generators from TOPI with the connection ofbus 2513 to bus 251 insteadlhas been known for many years. It occurs when an of a connection to bus 257. The objective of the modified

isolated induction generator is connected to a system having network is to simulate a short-circuit case far away from thecapacitance equal to or greater than its magnetizing reactance NUIG units.requirements. Unintentional islanding ofNUIGs may result inpower-quality issues, interference to grid-protection devices,equipment damage, and even personnel safety hazards. Since islanding is either caused by feeder faults (which inProtective relay systems must be responsive to this condition turn can cause tripping of the feeder relay) or by an accidentaland remove the NUIGs themselves from the island. Depending tripping of the feeder relay, three scenarios have beenon the value of the capacitance and machine loading, terminal considered for simulation conditions:voltages of 1.5 to 2 per unit can be produced. i. Three-phase short-circuit at bus 259 (TOP1) at timeThis paper attempts to: t=1 s, followed at t= 1.1 s by opening of the line between1- Examine the self-excitation and resulting overvoltages on busses 251 and 250; and removing the short circuit atthe real 25 kV distribution network of Hydro-Quebec. This t=2s;network contains the NUIG power plant which could face a ii. Three-phase short circuit at bus 2511 (TOP2) at timefault and/or an unwanted network disconnection from the t=1 s, followed at t= 1.1 s by opening ofthe line betweenutility system. As a result, the problems likely to occur on the busses 251 and 250; and removing the short circuit atnetwork have been analyzed, and subsequently t=2s;recommendations in order to limit the self-excitation iii. Simple islanding of the studied network by opening ofphenomenon have been presented. the line between busses 251 and 250 at time t=1.1 s.2- Propose protection schemes and proper relaying criteria forinterconnection ofNUIGs to the distribution networks. 4. STUDIED CASES AND INITIAL POWER FLOW

The same local network system was used in [7, 8]. In [7] As described in section 3, all scenarios imply the openingthe focus was to examine the self-excitation phenomenon in ofthe line between busses 251 and 250. Therefore, the statusthe islanding condition using the Hydro-Quebec ST600

1-4244-1445-8/07/$25.00 ©)2007 IEEE 195

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of the sub-network located "below" this line on TABLE 1: INITIAL POWERFLOWFigure 1 (TOPI) is of primary importance. Forty-five cases Ref| PowerFlowhave been obtained by varying the load and compensation co Base Induction Generator Sub-Network 251 to 250levels and their positions in the sub-network, as well as by m

changing the load modeling. Case Comp. ProdJuction Comp. L.oad Pf QfMVAR MW MVAR MVAR MW MVAR MW MVAR

1 2 3 4 5 6 7 8 9 10

sO sl 0.59 3.08 -1.11 0 5.31 1.74 -2.07 -2.9Hydra-Quebec HQ sl - 0.64 3.27 -1.13 2.63 5.31 1.74 -2.07 -0.3315 kV source

s2 - 0.66 3.32 -1.13 2.7 3.24 1.65 0 0

Bus 3151 s3 s2 0.74 3.36 -1.06 3.01 3.24 1.49 0 0.44s4 s2 1.14 3.38 -0.65 2.65 3.24 1.49 0 0.25

"J)315-25kV |s5 sl 1.38 3.331 -0.4 1.92 5.31 1.74 1-2.02 -0.21315: 25 kVry "n s6 s2 1.6 3.44 -0.2 2.45 3.24 1.5 0 0.74

s7 - 0.65 3.26 -1.11 1.33 2.66 0.87 0.56 -0.7421 MW Bus 250 s8 s7 0.66 3.28 -1.11 1.34 1.63 0.54 1.58 -0.4

FauIt Locat l6.8MVAR l31.2 km S9 s7 0.67 3.32 -1.11 1.7 1.63 0.54 1.61 0.02(LossofLine) ~~~~~~Bus2510.295 MW slo - 1.78 3.39 0 0 0.53 0.17 2.78 -0.31

0.097 MVAR 5.35 km sll slo 0.89 3.26 -0.88 0 0.53 0.17 2.65 -1.2Bus 252

0.126 MW s12 slO 0.445 3.2 -1.29 0 0.53 0.17 2.59 -1.630.041 MVAR t 1.0 km s13 slO 2.225 3.47 0.47 0 0.53 0.17 2.84 0.14

Bus 253 s14 slO 0.3223 3.18 -1.4 0 0.53 0.17 2.57 -1.752.045 MW0.672 MVAR 0.7 km s15 s7 2.09 3.38 0.32 0 2.66 0.87 0.66 -0.63

Bus 254 s16 s7 2.09 3.36 0.3 0 3.22 1.06 0.01 -0.830.312 MW0.103 MVAR 6.56 km s17 s7 1.78 3.32 0 0 3.22 1.06 0.06 -1.12

L Bus 255 s18 sl 1.78 3.24 0 0 5.31 1.74 -1.99 -1.770.628 MW =-r1. MVAR

0.206 MVAW .9 krMw s19 - 1.78 3.26 0 2.63 10.6 3.49 -7.18 1.08Bus 256 s20 sl 2.05 3.38 0.28 1.32 5.31 1.74 -1.97 -0.2

1.6 km s21 si 1.78 3.39 0 2 5.31 1.74 -2 0.21Bus 2513 Bus 257 s22 slo 0.2 3.17 -1.51 0 0.53 0.17 2.55 -1.86

4.0km ~ 3. kT 9M\A s23 s7 0.65 3.21 -1. 1 0.665 3.19 0.87 o -1.3.9320 - 41kBus 258 s24 slO 0.5933 3.22 -1.16 0 0.53 0.17 2.61 -1.4925: 4.16kV 0.917MW. .[> ) 0.301 MVAR s25 s7 0.65 3.26 -1.11 1.33 3.22 0.87 0 -0.73

L1. Aj s26 slO 1.78 3.4 0 0 0.53 0.17 2.78 -0.32

Bus 51 25: 25 kV s27 slO 1.78 3.4 0 0 0.53 0.17 2.78 -0.320.6 M1VAR Tr | Fault Locatiorl \ ls28 slO 1.78 3.4 0 0 0.53 0.17 2.78 -0.33

2.80 MW (Three-phase Bus 259 s29 slO 0.41 3.19 -1.32 0 0.53 0.17 2.58 -1.66-1.51 MVAR Short-circuit) s30 slO 0.3223 3.18 -1.4 0 0.53 0.17 2.57 -1.76

GoryfaIls ~~~~3.5 kmGory falls | Bus2510 s31 slO 0.44 3.2 -1.3 0 0.53 0.17 2.59 -1.640.701MW 2 k s32 slO 0.41 3.19 -1.32 0 0.53 0.17 2.58 -1.67

Bus 2511 S33 slO 1.78 3.34 0 0 0.53 0.17 2.77 -0.190.286 MW S34 slO 1.78 1.68 0.74 0 0.53 0.17 1.11 0.57

0.094 MVAR535 sl 1.78 3.48 0 2.63 4 1.31 -0.68 1.3

Fig. 1: Real studied system (TOPI) s36 slO 1.78 3.4 0 0 0.53 0.17 2.78 -0.32S37 sl 1.78 3.34 0 0 5.31 1.74 1.32 -0.73

The result of performing simulations of the 45 cases for s38 sl 1.78 3.5 0 2 5.31 1.74 1.4 1.3100 ms is shown in Table 1. This table gives the initial power S39 sl 1.78 3.39 0 1.51 4 1.31 -0.69 0.16flow of all studied cases and is organized as described in [7]. s40 sl 1.78 3.35 0 2.63 4 1.31 -0.78 1.2

s41 slO0 0 3.22 -1.73 1.45 0.53 0.17 2.6 -0.62However, no numerical divergence is observed with S42 S7 0 3.2 -1.7 1.45 0.53 0.17 2.6 -0.62EMTP-RV in contrast to [7]. S43 s7 0.65 3.34 -1.14 1.33 2.66 0.87 0.59 -0.83

S44 s7 2.09 3.39 0.32 0.23 3.22 1.06 0.11 -0.57

5. RESULTS ANALYSIS

In the analysis of the results, we will pay attention to the 5.1 THREE-PHASE SHORT CIRCUIT FOLLOWED BY ISLANDINGbehavior of the 25 kV network after the occurrence of typical Figure 2.a demonstrates the typical examples of the voltageperturbation with reference to the: (a) topology, behaviors in the case of a three-phase short-circuit fault close(b) contingency, (c) system load level, (d) capacitive to the NUIG for five base cases (si, s2, s7, sO0 and s19). Theself-excitation level and position, (e) reactive compensation of results have shown that NUIG could not support thethe network, (f) load type, and (g) protection system. sub-network after three-phase fault inception at bus 259

Observations taken at bus 51 where the NUIGs are (TOP 1). However, in some cases the capacitor is sufficient forconnected include the voltage (p.u.), the frequency (Hz), the the self-excitation phenomenon (e.g. s10). Figure 2.b showsactive power (MW) and reactive power (MVAR). Only the voltage behaviors for two cases (s33 and s40) considered asanalysis ofthe voltage (p.u.) is presented in this paper. modified systems to simulate a three-phase fault far away

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from the NUIG. The results have shown that in the case of a 5.2.3 INFLUENCE OF THE COMPENSATION AND LoAD LEVELthree-phase fault at bus 2511 (TOP2), the voltage on the Figure 4.a shows the voltage behavior of two cases (s35,generator terminal is near the nominal rates and the fault and s39). Both cases have the load in sub-network higher thanrepresents only an additional load to the generator. After the NUIGs generation (see Table 1). In the case of s35 theseparation of the sub-network from the utility system in both sub-network is extremely over-compensated (Q-1..3 MVAR),conditions (at busses 251 and 2511), the voltage drops very whereas in case s39 the compensation is reduced. Figure 4.afast (the voltage drops to 0.2 p.u. in 3 cycles) and NUIG is no shows that the occurrence of self-excitation phenomenonlonger a source of load or fault current. depends more on the active load level in the sub-network

_________________ ~~~~~~rather than the compensation level.

oc< ~~~~~5.2.4 INFLUENCE OF THE LoAD MODEL

04~~~~~~~OA- ~~~~~~Cases s2 1 and s3 8 correspond to the same initial operation>0 L ~~~~~~~~~~~pointand respectively 000 and 700o of their loads are

12 __ ~~~~~~~~represented with constant power. Figure 4.b illustrates that as-OA~~ ~ ~~ the percentage of constant power load increases, the rate at

Time(s) Time(S) which the voltage collapses is quicker.Fig. 2.a: At bus 259 (TOPI) Fig. 2.b: At bus 2511 (TOP2)

Fig. 2: Short-circuit followed by network disconnection, voltage variations

5.2 ISLANDING CONDITION 9

Scenario iii of section 3 has been followed in this part.

5.2.1 INFLUENCE OF THE SYSTEm LoAD LEVEL

Figure 3 .a shows the voltage behavior of five base cases >S ~ ~ 2(s19, si1, s2, s7 and slO). With respect to the base case sI, the 3loads are divided by 1.64 in case s2, divided by 2 in case s7,/divided by 10 in case slO , and multiplied by 2 in case s19.In all five cases the reactive compensation is sufficient4(negative Qf in Table 1). Figure 3.a clearly illustrates that 7re()nnp

when th loadevel i reducd, sel-excittion ad overFig. 4.a: Influence of compensation level Fig. 4.b: Influence of load type

when th loadevel i reducd, sel-excittion ad over Fig. 4: Simple disconnection of Hydro-Qu6bec's source, voltage variationsvoltage is more likely to occur.

5.3 PLAN OF POWER RATios5.2.2 INFLUENCE OF THE COMPENSATION LEVEL The simulation results have shown that two important

Figure 3 .b shows the voltage behavior of six cases (s22, factors in the occurrence of self-excitation are: a) the actives14, s31, sItI, sI 0 and si1 3). With respect to the base case sI 0, load level (compared to the induction machine active powerthe cases sItI, s3 1, s14 and s22 correspond to a reduction in output), which determines the frequency variation afterthe value of the capacitor compared to case s 10, and case s 13 disconnection, and, b) the reactive compensation levelcorresponds to an increase in the value of the capacitor (compared to the system reactive consumption), which(see Table 1). Figure 3.b illustrates that by increasing the determines the voltage variation after disconnection. Thus, thecompensation of machine, the rise of voltage is faster (the following two power ratios have been considered:voltage reaches 2 p.u. in 0.35 s). PR; is the ratio between the initial active power

consumed in the sub-network and the initial active powerproduced by the generator.

PPgPj Pf: Active power flowed from busses 251-250R p ~~Pg Active power produced by generatorsS13 9~~~~~~~~~~QR; is the ratio between the initial reactive power

Lw ~ ~ ~~cnumed in the sub-network (including the machine777:,V~~~~~~~~~ consumption) and te initial reactive power produced bytte

three capacitors at busses 51, 255 and 257.

2007 IEEE Canada Electrical Power Conference4

which have been used to derive practical guidelines presented TABLE 2: COMPARATIVE TIMES AND DIAGNOSTICSbelow in section 6. These results are also consistent with those Case tv120 tv140 tf61.5 tf63obtained in [7]. No. (ms) (ms) (ms) (ms) lil

0 - - 151.76 191.99

1 331.63 379.14PR3.5 2 0

No self excitation 3

23~~~~ ~ ~ ~ ~~~~-357

3 1 Self-excitation

2.5- -- 1 1 346.74 395.04 *

16 15.2 236 0

---------07 1111 - 126.71 195.4 0

1.5COPAAT. T-IE A---8 153.17 312.43 87.4 131.23 0

- ~~ ~~~~~~ ~~~~~~~~~~~~~~~999.32238.64 92.03 143.73 010 68.61 136.29 62.92 82.06 0

0.5.-------NS- 1 193.98 329.13 62.92 91.75 0

0onsidering QRdro-Quebec srequirements[13]re g12 569.98 843.46 65.56 94.7 00 1 2 3 4 5 6 7 8 9 10 11 13 45.38 94.44 63.49 92.82 0

Fig. 5: Simple disconnection of Hydro-Qubhec's source, plan of power ratios 14 940.91 1084.3 65.82 94.820for 45 cases 15 664 - 125.01 197.97 0

16 - - 153.12 233.68 0

17 - - 136.38 198.37 *Results showA T TiMES afterPROTECTION SYSTEM the 18 - - 191.88 236.72 *CONSIDERATIONS 19 - - 246.19 274.49 *

Considering Hydro-Quebec's requirements [13] regarding 20 - - 351.88 400.721 - - 393.18 442.58 *the frequency and voltage thresholds and using the simulation 22 1384.2 1580 65.55 94.84

results of 45 cases, times to reach the assumed different 23 - - 127.95 181.82thresholds for the frequency (61.5 Hz and 63 Hs) and for the 24 340.27 559.28 62.91 92.04 0voltage (1.2 p.u. and 1.4 p.u.) in the islanding condition were 25 - - 168.41 255.62 0calculated and presented in Table 2. 26 63.39 130.12 62.61 91.28 0

3-RThesultsuencythataftereseparationoldthesub-network:27 63.16 129.71 62.61 90.97 0Results show thatafter separation of the sub-network: 28 68.93 136.16 63.15 91.810

1- In all cases the frequency, and in most cases the voltage, 29 704.33 909.21 65.55 94.53 0passes different thresholds very fast and reaches to the 30 959.21 1100 65.99 95.49 Ofrequency in which, as per Hydro-Que'bec's requirements, the 31 593.82 862.38 65.66 94.83 0

protection systems must trip instantaneously and disconnect 32 716.41 922.81 65.99 95.66 0

the sub-network from the NUIG; 33 70.6 138.57 63.54 92.83 034 88.32 215.15 111.27 174.51 0

2- The times needed to reach the different thresholds are 35 - - - - 1often very short, and their comparison shows that tf63 iS 36 69.39 136.81 63.58 92.41 0smaller than tV14 and tV2 in most cases and te61.5 is always 37 - - 189.27 225.94s*

smaller than tv12; ~~~ ~ ~ ~~~~~~~~~~~~~~~38--278.46 314.95 *

3- The frequency threshold of 61.5 iz permits the detection 40 - - 527ICA 638AYS-of all cases except 6 (s2, s3, 4, s6, s35, s40), but the voltage 41 77.87 151.79 64.4 95.18 0thresholds solely are not reliable to detect the islanding 42 - - 129.56 202.14 0

co. ........... ...... widelydependitions;g43908.4 o 120.27 183.19 0

4- Case s2, where the initial powers are altost balanced (see 4N sl-ea oS o D6.7 DTable 1), is a special case because it presents very smallvoltage and frequency deviations in the prohibited tripping 6 TYPICAL RELAYS IN INTERCONNECTION PROTECTIONzone; SYSTEMS5- For the other 5 cases, in which the voltage and the The functional levels of interconnection protection varyfrequency both drop, they could easily be detected with a widely depending on factors such as: generator size, point ofthreshold of 57 liz, for instance.. interconnection to the utility system (distribution or

The simulation results show that for the island'ng su-rnmsi),tpofnecnetonothuily,yecondition, if it were caused by a feeder fault (conclusion from s(induction) synchrconnectiontoitheutilnectionsection 5. 1), over/undervoltage relays could be used and if it is of gns ertor (inuction, scaused simply by an inadvertent trip of the substation breaker Tanoer couration.(conclusion from section 5.2 and 5.4), then Table 3 icludes a non-exhaustive list of typical protection

over/uderfreuency elays ould b requied. Threfore relays, which may be used in the interconnection protectionminimum protection requires over/undervoltage relays an systems of different types of Non-Utility Generations (NUGs).

over/uderferuencyelays n all UIGs.The specific objectives of an interconnection protectionsystem, as well as the relay functional requirements withrespect to each objective are shown in Table 3 [10, 14].

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TABLE 3: TYPICAL INTERCONNECTION RELAYS FOR DIFFERENT TYPE OFNUG ,

Interconnection Protection IEEE No. ApplicationObjective

50 instantaneous overcurrent NUIG RELAYING FOR INDUCTION GENERATORS

51 overcurrent with time delay SUSCEPTIBLE TO THE SELF-EXCITATIONCONNECTED THIROUIGH Wye-Wye

5ON neutral instantaneous overcurrent TRANSFORMER

|51N neutral overcurrent with time delay CT

51V voltage-restrained overcurrentFault Backfeed Detection _______ 1N

67 directional overcurrent yrT2 or 3VTs 1

67N neutral directional overcurrent

21 distance

59N neutral overvoltage 27 59 591 ou

27N neutral undervoltage Note 1

27 undervoltage_______ ZCTs ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~51Vl 51 46 51G271 instantaneous undervoltage

Detection of Loss of Parallel 81 O/U over and underfrequency Note 2 Note 3Operation with Utility System orDetection of Islanding Conditions 591 instantaneous overvoltage

59 overvoltage1

A E Notes,

TT transfer trip 1- Required only if271 ~~~~~~~~~~~~~~ferroresonance is possible.Detection of Damaging System 47 negative sequence voltage 1j B C

Conditions (1), 25 2- Required only if46 negative sequence current \ 27 operating time is to slowAbnormal Power Flow Detection 32 directional power l forfeed faults.

Restoration or Synchronization 25 synchronization 3- Use one or other\V\Jisilble LockabDle only if feeder unbalance can

0Switch cause transformer over loading.Figures 6 and 7 show single line diagrams of typical

interconnection protection relays for NUIGs respectivelysusceptible and not susceptible to the self-excitation and Fig. 6: Single line diagram ofNUtIG relaying, susceptible to theconnected through Wye-Wye transformers [2, 10, 14]. Relay self-excitation and connected through Wye-Wye transformernumbers and their functions in Figures 6 and 7 are explainedin Table 3.

7 INTEGRATION CRITERIA AND RECOMMENDED PROTECTIONSYSTEM

The following practical guidelines could be derived for the NUIG RELAYING FOR INDUCTION GENERATORSintegration of NUIGs to the Hydro-Quebec's distribution C EPTI TTHE SELF-Enetwork based on the simulation results presented in TRANSFORMERsection 5 and previous research presented in section 6: 1 CT1- Compute the ratio between the initial value of the

minimum active load that could remain connected to the 51Ngenerator after separation and, the nominal active power of ,the generator (PR);

2- If the ratio (PR) is smaller than 3, self-excitation 47phenomenon could occur. Hence, the total capacitive A

f

compensation should be between 10% and 50% of themachine reactive compensation; then the full complement 271of relays shown in Figure 6 with a minimum time delayshould be used. B c

3- If the ratio (PR) is higher than 3, the probability of havingself-excitation is very low. So, the total amount of L 1 Required only ifcapacitive compensation is not critical, but it should not ferroresonance is possible.exceed the machine reactive consumption; then thereduced complement of relays, shown in Figure 7 with 0usual settings can be used.

4- In cases when the compensation cannot be reduced due to Fig. 7: Single line diagram ofNUIG relaying, not susceptible to theoperation ~neesiis TrnfrTi. T)o h eeao self-excitation and connected through Wye-Wye transformer

could possibly be considered.

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[6] K. Kauhaniemi, L. Kumpulainen, "Impact of distributed generation on

8 CONCLUSION the protection of distribution networks" Developments in Power SystemProtection, IEE International Conference, 5-8 April 2004, Amsterdam,

This study was made of two parts. The first part focused pp. 315-318.mainly on the self-excitation phenomenon which resulting [7] R. Belhomme, M. Plamondon, H. Nakra, D. Desrosiers and C. Gagnon,"Case study on the integration of a non-utility induction generator to theovervoltages on an actual 25 kV distribution system. As a Hydro-Quebec's Distribution network" IEEE Transaction on Powerresult, practical guidelines to limit the occurrence of this delivery, Vol. 10, No. 3, July 1995.phenomenon have been derived from this phase of the case [8] R. Wamkeue, S. Moraogue and I. Kamwa, "Distribution network fed in

co-generation by induction generators: Incidence of self-excitationstudy. In the second part, the Impact of NUIGs on the phenomenon" IEEE International Conference on Electrical Machinesperformance and coordination of feeder's protective devices and Drives, ICEM 2001, 2001, pp. 594-603.during fault events was studied. Simulation results showed [9] R. M. Rifaat, "Critical considerations for utility/cogeneration inter-tie

protection scheme configuration", IEEE Transactions on Industrythat NUIGs contribute only 2 or 3 cycles of fault current, but Applications, Vol. 31, No. 5, September/October 1995, pp. 973 - 977.after an islanding condition, it is no longer a source of load or [10] Charles J. Mozina, "Interconnection protection of IPP generators at

fault current. This also proved that after an islanding commercial/industrial facilities", IEEE Transactions on Industrycondition, the power quality is not guarantied and anti- Applications, Vol. 37, No. 3, May-June 2001, pp. 681-688.

condition, the power quality Is not guarantied and anti- [1 1] IEEE Standard 1547-2003, "Standard for interconnecting distributedislanding protection for NUIGs is a more challenging problem resources with electric power systems".in comparison with the other type of faults. [12] IEEE Standard C37.95-1989, "Guide for protective relaying of utility-

Based on practical guidelines presented in section 7, the consumer interconnections".[13] Hydro-Qu6bec's Standard E.12-01-2005, "Requirements relating to the

NUIG owner must demonstrate that: connection of decentralized production to the distribution networks of> The NUIG protection systems are capable of detecting a Hydro-Quebec".

power island condition. [14] Charles J. Mozina, "Interconnection protection of dispersed generators",IEEE Transactions on Industry Applications, Vol. 5, 8-12 Oct., 2000, pp.> In the event of self-excitation, isolation of the NUIG will 3273-3280.occur quickly enough to preclude damage to other [15] G. Bizjak, D. Zvikart, "Behaviour of small hydroelectric power plantcustomers or utility system from the abnormal voltages generators during the fault in distribution network (digital simulation

study)", IEEE Transmission and Distribution Conference andthat may occur. Exposition, 2001 IEEE/PES, Vol. 1, 28 Oct.-2 Nov. 2001, pp. 481-485.

> The interrupting device used to separate the NUIGgenerator from utility system is capable of operating at the 11 BIOGRAPHIESelevated voltages which may occur followingself-excitation. Hamidreza Bakhshi received his B.Sc. from IranUnless the NUIG owner can demonstrate through the University of Science and Technology, Tehran, Iran,execution of analytical studies, that there is no risk of in 1993 and his M.Sc. from Laval University, QC,

self-excitationofthegenerator. ~~~~~~~~~Canada, in 2006, both in electrical engineering.self-excitationofthegenerator. ~~~~~~Heis a registered professional engineer withIn assessing the opportunity for the self-excitation over 10 years experience in the field of overhead

phenomenon, the presence of existing generators on the same power transmission lines in Iran and Canada. Sincefeeder along with the minimum load likely to be connectedto2006, hehas been with SNC-Lavalin T&D in thefeeder alongwith themiimum load lkely to be onnected toTransmission Line Division.the feeder must be taken into consideration.

9 ACKNOWLEDGMENT

The authors gratefully acknowledge the contribution of Innocent Kamwa (S'83-M'88-SM'98-F'05) receivedB. Khodabakhchian from Hydro-Que'bec, whose valuable

his Ph.D. degree in electrical engineering from LavalB. Khodabakhchianfrom Hydro-Qu~bec, whose valuableUniversity, QC, Canada, in 1988. Since then, he has

comments helped to improve this paper. been with the Hydro-Quebec Institute/IREQ, PowerSystem Analysis, Operation and Control, Varennes,

10 REFERENCES QC, where he is currently a Principal Researcher inbulk system dynamic performance. He has been an

[1] A. Borghetti, R. Caldon, S. Guerrieri and F. Rossetto, "Dispersed - Associate Professor of Electrical Engineering at Lavalgenerators interfaced with distribution system: dynamic response to University since 1990.faults and perturbations" Bologna PowerTech Conference, Bologna, Dr. Kamwa has been active for the last 13 yearsItaly, 2003 IEEE, June 23-26. on the IEEE Electric Machinery committee where as a Working Group Chair

[2] D. Dawson and W. E. Dugan, "Interconnecting distributed generation to and Secretary, he contributed to the latest standards 115 and 1110. A memberutility distribution system", Short Course, University of Wisconsin- of CIGRE and a registered professional engineer, Dr. Kamwa is a recipient ofMadison, June 1999. the 1998 and 2003 IEEE Power Engineering Society Prize Paper Awards and

[3] In-Su Bae, Jin-O Kim, Jae-Chul Kim and C. Singh, "Optimal operating is currently serving on the Adcom of the IEEE System Dynamic Performancestrategy for distributed generation considering hourly reliability worth", Committee.IEEE Transactions on Power System, Vol. 19, No. 1, February 2004.

[4] M. Begovic, A. Pregelij, A. Rohatgi and D. Novosel, "Impact ofrenewable distributed generation on power systems" System Science,Proceedings of the 34th Annual Hawaii International Conference on,Jan. 3-6, 2001, pp. 654-663, Maui, Hawaii.

[5] T. Ackermann and V. Knyazkin, "Interaction between distributedgeneration and the distribution network: operation aspect" IEEE/PESTransmission and Distribution Conf. and Exhibition 2002: Asia Pacific,Vol. 2, 6-10 Oct. 2002, pp. 1357-1362, Yokohama, Japan.

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