DEVELOPMENT OF RECLOSER COORDINATION PROGRAMMING FOR DISTRIBUTED GENERATION ISLANDING DISTRIBUTION NETWORK

Sujarit Muangchareon 1, and Atthapol Ngaopitakkul 1 1 Department of Electrical Engineering, Faculty of Engineering, King Mongkut’s Institute of Technology Ladkrabang,

Bangkok 10520, Thailand. (e-mail: knatthap@kmitl.ac.th)

ABSTRACT

When faults occur during islanding, faults should be eliminated before the power system is unstable. An islanding system is normally a weak system. The setting of protective devices should be completed before going back to the normal operation. This paper focuses on the impact of protective device when distributed generation is considered in islanding condition, then resulting in protection of the electrical system malfunctions. To overcome this problem, the setting of recloser coordination is investigated in this paper. The fault current and protection coordination is considered for protective device. The results show that the setting recloser for islanding condition, when recloser is set using proposed technique, it can reduce complexity and increase security of recloser.

KEY WORDS Distributed generation, Islanding, Protective device, Distribution System, recloser coordination 1. Introduction

Islanding operation is a condition that a main power system is interrupted, however, energized by DG units interconnected to the distribution system. Islanding operation can occur, when a part of distribution system is disconnected by unplanning. To supply some of the separated parts where DG is available, islanding operation of DG should be performed. In this case, the reliability of the power system is improved, and reduce customer outage costs. Likewise, where DG is available as islanding operation, it may cause negative impacts [1-5] such as large load rejection, voltage regulation, and etc.

The protection of the future is very strongly connected to the control and operation issues of distribution network. However, when the faults occur during islanding operation, the faults should be eliminated before the power system is unstable. An islanding system is normally a weak system. The frequency and voltage protections should be carefully set up when frequency and voltage deviations are high during a short period. The setting up of protective devices should be completed

before going back to the normal operation. The conventional protection in distribution networks is designed to operate for high fault current levels in radial networks, but during island operation of the distribution network, high fault-currents from the utility grid are not present. The several papers are research to detected islanding operation of DG using several techniques

[6-11]. A S-transform technique for islanding detection

based on spectral energy content of the time-frequency transform is proposed [6]. A combination of Wavelet Transform and S-Transform [7] have introduced to detection of islanding event and PQ disturbances in grid-connected hybrid power system. The negative sequence component of the voltage signal is used in islanding detection. A decision tree initialized fuzzy rule base classifier is proposed for islanding detection [8]. The intelligent relay, as introduced in [9], is viewed as passive islanding protection. This technique proposed relay setting by using both dependability and security performance indices, the latter being particularly important for minimizing nuisance tripping for larger DG penetration levels. The wavelet singular entropy [10] is proposed to detect islanding operation in distributed generation which is interfaced to the microgrid. A Fast Gauss-Newton algorithm [11] is proposed to detect islanding operation.

This paper focuses on the impact of protective device when distributed generation is in islanding condition, then resulting in protection of the electrical system malfunctions. The distribution system under investigations is a part of Provincial Electricity Authority (PEA). Under this research, DG data that connect to the PEA distribution are used. The simulations are performed using digital simulation and electrical network calculation software (DIgSILENT). The setting of recloser coordination is investigated in this paper. The fault current and protection coordination is considered for protective device.

Proceedings of the IASTED International ConferencePower and Energy Systems (AsiaPES 2013)April 10 - 12, 2013 Phuket, Thailand

DOI: 10.2316/P.2013.800-149 425

2. Power System Simulation using DIgSILENT

DIgSILENT powerfactory is employed to simulate and analyse recloser coordination when distributed generation (DG) operates as islanding condition as shown in Figure 1. The scheme under investigation is part of Thailand’s electricity distribution system.

Figure 1. A simple radial system with DG connected with

distribution system From the Figure 1, it can be seen that photovoltaic and

synchronous machine are distributed generation that are connected between substation and distribution sections. The protective devices including circuit breaker, over current relay, under voltage relay, over voltage relay, under frequency relay, and over frequency relay, are installed at B1, B2, B3, B4, B5 and B6. In addition, R1 and R2 are recloser in distribution system while F1 and F2 are fuses. Load of distribution system can be explained as shown in table 2.

3. Recloser Coordination Programming

Recloser coordination technique to find parameters

for setting coordination of protective device is shown by flowchart in Figure 2. From Figure 2(a), the data of setting line, transformer, DG, external grid parameter are considered, which depend on operation to calculated load flow and short circuit by user. The minimum current, rated current of fuse, and time- current curve (TCC) are assumed, then, operation time at the same short circuit current, is compared with standard. If operation time is faster than standard, then, parameter that is assumed will be setting as parameter of recloser and fuse. In order to verify set protective device, short circuit current is simulated to consider coordination between recloser (R1) and next recloser (R2). However, this technique is performed very slow and complex, so this paper is aimed to propose a technique to reduce time and complexity step of coordination protective device as shown in Figure 2(b) and Figure 3.

Under this research, the short circuit current and voltage including load current, load voltage at R1 and R2 bus is simulated in steady-state by DIgSILENT as shown in Table 3 and Table 4. From Table 4, it can be seen that the both DG will not inject current because of transformer connecting to DG, is vector group as Dyn0. The short circuit current as shown in Table 4, is employed in recloser coordination programming that generated “.local” file. The output “.local” file is set for recloser (R1 and R2) in DIgSILENT using DPL command as shown in Figure 4.

Table 1 DG type that connect with distribution system

Name DG Type Short Circuit Contribution

Local Controller Rate Power (MW)

DG PV Photovoltaic No Power factor 2 DG SM Synchronous Machine Yes Power factor 5

Table 2 Load of distribution system

Name Load Voltage Power Factor Load Type Power (MW)

LOAD SM 22 kV 0.85 lagging Synchronous Machine 3.5 LW1 22 kV 0.85 lagging Resident 1.0 LW2 400 V 0.80 lagging Resident 2.0 LW3 22 kV 0.80 lagging Resident 1.0 LW4 400 V 0.90 lagging Resident 1.0

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Development

1.Drawing circuit2.Setting line parameter

3.Setting transformer parameter4.Setting DG parameter

5.Setting external grid parameter

1.Load flow calculate2.Short circuit calculate

1.Assume minimum current and 2.TCC curve for recloser

Compare grading margin(> Standard)

1.Draw recloser 2.Setting recloser parameter

Simulate short circuit event verify setting

End

Yes

No

Pass

Not pass

1.Drawing circuit2.Setting line parameter

3.Setting transformer parameter4.Setting DG parameter

5.Setting external grid parameter

Execute fault report DPL command

1.Draw recloser and fuse2.Execute PS DPL command

Simulate short circuit event verify setting

End

Pass

Not pass

Run coordination recloser program(refer to figure 3)

(a) Conventional technique (b) proposed technique Figure 2. Setting of recloser in DIgSILENT PowerFactory (a) operation by conventional technique (b) by proposed technique

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1.Setting number of recloser (Nt)2.Setting sequence of recloser (N)

3.Setting Relay

Nt = N

SettingTCC1= curve 102TCC2 = curve 165

Sequence coordinate = deactivate

Setting TCC1= curve 105TCC2 = curve 165

Sequence coordinate = active

1.Setting maximum short circuit current2.Setting minimum short circuit current

3.Setting minimum current (IL)4.Setting minimum prefault voltage (V1)

5.Setting minimum voltage during fault (V2)

Pick up current = IL/2

Prepare grading marginAt minimum SSC to maximum SSC

> 0.1 sPick up current = Pick up current + 1

Generate File . Local

Nt = N

End

N = N+1

Pick up current > minimum SSC

Y se No

Yes

No

Yes

No

Yes

No

Figure 3. Flow chart of recloser coordination programming

Table 3 Load current of setting transformer and voltage at steady state

Position Load Current (A) Voltage R1 20 21.42 R2 30 21.72

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Table 4 Short circuit current and voltage when SLG short circuit at different positions

Position Short Circuit Current (A) Voltage (kV) Grid DG PV DG SM R1 R2

N2 264 0 0 23.45 22.73 R1 328 0 0 23.23 23.33 R2 301 0 0 23.34 22.47 B1 310 0 0 23.69 24.00 F2 261 0 0 23.42 22.66

Referring to Figure 4, and to the time sequence shown

in Figure 5, in case of single line to ground fault, it occurs at the nineth second at location node F2, when both recloser are set as follow in Figure 4. In the early stages of recloser, recloser (R2) was open by TCC1 with operating time of 9.2476 second, then, recloser was closed by time interval 1 with operating time of 14.2571 second. In this case, recloser (R1) will be operated. For this event, if the fault is not cleared, recloser continues to open again with operating time of 17.0719 second, then, recloser was reclosing by time interval 2 with operating time of 32.07992 second. Likewise, if the fault is not still cleared, then, recloser will be locked out by TCC2 with operating time of 34.01574 second. Result of recloser event sequence can be summarised in Figure 5. Referring to the time sequence shown in Figure 6, in

case of single line to ground fault, it occurs at the nineth second at location node F1, when both reclosers are set as conventional technique follow in Figure 2(a). In the early stages of recloser, recloser (R1) that was installed was open by TCC1 with operating time of 10.43448 second, then, recloser (R1) was closed by time interval 1 with operating time of 15.44291 second. In this case, the fault should be cleared by recloser R1 and R2, but recloser

(R2) will not be operated so that DG synchronous machine is failed by fault current. For this event, if the fault is not cleared, recloser continues to open again with operating time of 23.17694 second, then, recloser was reclosed by time interval 2 with operating time of 38.18446 second. Similar, if the fault is not cleared, then, recloser will be locked out by TCC2 with operating time of 43.70116 second. Result of recloser event sequence can be summarised in Figure 6.

Referring to the time sequence shown in Figure 7, In case of single line to ground fault, it occurs at the nineth second at location node F1, when both recloser are set as shown in Figure 4, recloser (R1 and R2) that were installed are open by TCC1 with operating time of 10.43448 second, then, recloser are closed by time interval 1 with operating time of 15.44291 second. For this event, if the fault is not cleared, recloser continues to open again with oprating time of 23.17694 second, recloser is reclosed by time interval 2 with operating time of 38.18446 second. For last event sequence, if the fault is not cleared, then, recloser will be locked out by TCC2 with operating time of 43.70116 second. Result of recloser event sequence can be summarised in Figure 7.

(a) Result of setting recloser R1

(b) Result of setting recloser R2

Figure 4. Result of setting recloser from recloser coordination programming

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Figure 5. Recloser R2 event sequence when single line to ground fault occurring at node F2

Figure 6. Recloser R1 event sequence when single line to ground fault occurring at node F1

Figure 7. Recloser R1 and R2 event sequence when single line to ground fault occurring at node F1

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4. Conclusion

This paper focuses on the impact of protective device when distributed generation is considered in islanding condition, then resulting in protection of the electrical system malfunctions. The short circuit current and voltage including load current, load voltage at each recloser bus are simulated in steady-state, then, fault current and protection coordination is considered for protective device. The results show that the setting recloser for islanding condition, in case of conventional technique is performed very slow and complex while when recloser is set using the proposed technique, it can be fast operated and simply for setting. As a result, the proposed technique can reduce time and increase security of recloser. Acknowledgements

The authors wish to gratefully acknowledge financial support for this research from the energy policy and planning office (EPPO), Ministry of Energy and the faculty of Engineering, King Mongkut’s Institute of Technology Ladkrabang (KMITL), Thailand. And also for the DIgSILENT presented in this paper, which is supported by Provincial Electricity Authority (PEA). References

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