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Proceedings of the 14th International Middle East Power Systems Conference (MEPCON10), Cairo University, Egypt, December 19-21, 2010, Paper ID 220.

527

A Combined MODELS-TACS ATPdraw General Model

of the High Impedance Faults in Distribution NetworksKamal M. Shebl, Ebrahim A. Badran,IEEE Member, and Elsaeed Abdalla

Electrical Engineering Department,

Faculty of Engineering,Mansoura University,

Mansoura, 35516, Egypt

[email protected]

Abstract - The High Impedance Faults (HIF) are the faults

which are difficult to detect by overcurrent protection relays. In

this paper a generalized HIF arc model is presented. The

proposed model is based on the dynamic arc resistance. A

combination between MODELS and TACS as supported tools in

ATP will be used. The proposed arc model is validated by

comparing the simulated results with the published results. The

comparison shows a good agreement. Finally, the validated

model is used to analyse many fault scenarios on the IEEE 13-node radial distribution test feeder. The outputs confirm the

presented model validity..

Index Terms - Modeling, Arc Model, HIF, Distribution Network,

ATPdraw.

I. INTRODUCTION

Detection of high impedance faults (HIF) still presents

important and unsolved protection problem, especially in

distribution networks [1]. When a conductor such as a

distribution line makes contact with a poor conductive surface

such as an asphalt road or a tree, the resulting level of fault

current is usually lower than the nominal current of the system

at the fault location. Therefore, the conventional protection

relay system will not be able to detect the HIF and/or trip the

appropriate protection relay [2].

There are several models have been used for describing

the arcs. Most models are used for circuit breaker arcs and

several of them have been applied to long arcs or arcing faults

[3]. Furthermore, many software are used for analyzing this

phenomenon specially the transients programs. The

ElectroMagnetic Transient Program (Alternative Version)

EMTP-ATP is used through many literatures' methods of arc

modeling.

In [4] a realistic model of HIF incorporating non-linear

impedance, time-varying voltage sources and a controlled

switch -to yield the signal characteristics of arcing- is

presented. The main parts of this model were built using the

Transients Analysis Control System (TACS). Also, a digital

arc model which is derived from Hochrainer arc description is

used in [5]. It is based on energy balance in the arc. Whereas,

in [6], the arc is represented by two different components;

Thevenin-type and Iterated-type. It is simulated using

MODELS.

In [7] and [8] the HIF is modeled using a series of two

variable resistors; a transient arc resistor and a steady-state

higher fault-path resistor. The two series resistors have been

controlled using TACS. In [1] the diodes and polarizing ramp

voltages are used to control arc ignition instants. The arc

model consists of linear resistance, nonlinear resistance, andDC and AC sources. Whereas, in [2], [9] and [10] the arc

model is treated using anti-parallel diodes with non-linear

resistance and only DC source.

In [11] a HIF model using two time-varying resistances is

presented using MODELS. Finally, in [3] a universal arc

model is introduced to represent the HIF arc faults feature.

This model is based on TACS.

In this paper the arc is proposed to be modeled using a

combination between MODELS and TACS in ATPdraw.

This will make a better utilization for the benefits of the two

tools in ATP. This can lead to generalization of the arc model

using ATPdraw.

II. THE PROPOSED HIF ARC MODEL

The arc of the HIF is proposed to be modeled using

MODELS in combination with TACS in ATPdraw. This

proposed strategy is more flexible and easy to use. It will

provide a general purpose icon in ATPdraw to represent the

HIF arc.

The arc can be represented according to the principle of

thermal equilibrium using the following differential equation

[6]:

)(1 gGdtdg =

(1)

arcVi

G = (2)

where g is the time varying arc conductance, G is the

stationary arc conductance, |i| is the absolute value of the arc

current, Varc is a constant arc voltage, and is the arc time

constant. The time constant can be given by;


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BgAe= (3)

where A and B are constant parameters which represent

compromised values for positive and negative half cycles [3].

The steps of calculating of the arc conductance using

MODELS are arranged in the flowchart in Fig. 1. The

flowchart consists of; calculation of G, construction of the

main differential equation and its integration it. A feedbacksignal is used in calculation to initiate the differential equation

solution. The arc conductance is updated at each time step of

solution. The arc resistance is modeled in power network

using TACS controlled resistance type 91 [12].

Fig. 1: The Flowchart of the Proposed HIF Arc Model

Fig. 2 illustrates the general view of the resultant

ATPdraw basic HIF arc model using MODELS. It consists of

five inputs; simulation time, the measured arc current, a

feedback signal (g) and two additional signals; CTR and RES.

CTR is a control terminal to enable the user to input any

additional control signal. RES is a reset terminal to enable the

user to coordinate with control signal. The outputs of the arc

model are time varying arc resistance, Rarc, and arc

conductance, g. The three input variables; Time, CTR, and

RES can be simulated using TACS to give the required signals

Thus, the proposed HIF arc model combines between the

simplicity of MODELS and the flexibility of TACS.MODELS program is used in basic and iterative equation

processing. Whereas, TACS is used to enable the user to

input any type of control waveforms and/or reset signals.

This makes any type of faults, fault constants, and/or affected

power system constants can be manipulated through simple

terminals. So, the proposed model avoids the complexity of

existing TACS models and adds a flexible control to the

traditional black box MODELS subroutines.

It is evident that, the simulation time terminal is used to

enable the user to control the MODELS simulation time

regardless the overall ATP simulation step time. This makes

the MODELS solution very accurate. Furthermore, a

feedback signal is used to update the arc conductance.

Fig. 2: The ATPdraw HIF Arc Model using MODELS

III. VERIFICATION OF THE PROPOSED HIF ARCMODEL

The proposed HIF arc model is verified by comparing its

outputs with those published in [3]. The single line diagram

of the test system used for this verification is shown in Fig. 3.

The test system was picked from [3] and modeled using

ATPdraw as shown in Fig. 4 including the proposed HIF arc

model.

The test system operates at 20 kV. It consists of a 50 Hz

voltage source with 2.6% source impedance, Zs, and a 16

kVA, 0.234/20 kV transformer with 4.2% impedance, Ztr. A

capacitor divider of 100 pF and a calibrated resistance of

0.49 ohms are used with the system. For verificationpurpose, the HIF is applied using the following fault

condition, Rtree=140.5 K, A=5.6E-7, and B=395917 as

given in [3].

Fig. 3: Single Line Diagram for the Test System Used for Validation of the

Proposed HIF Arc Model

Fig. 5a illustrates the ATPdraw-TACS model for the

required control circuit for generating CTR signal. This

signal represents the arc duration. Also, Fig. 5b shows CTR

| i |

G=| i |/VarcVarc

)(1 gGdtdg =

BgAe= Integrator

1/g

Measured

Fault

current

Arc resistance, Rarc

Feedback

MeasuredCurrent

Simulation

Time

CTR

RES

Rarc

g

Inputs Outputs

HIF Arc

model using

MODELS

Rarc

Ztr

Rtree

Zs

I(t)

G

Feedback (g)

Time

CTR

RES

HIF Arc

model

using

MODELS


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The test system is supplied from 115 kV, 50Hz, with1100

MVA short circuit at 82 degree AC source. A 5 MVA,

115/4.16 kV, delta/wye grounded substation transformer, and

a 500 kVA, 4.16/0.48 kV in-line transformer are used. Many

lumped parameter and -equivalent, single phase and three

phase over-head and under-ground lines are used to connect

the system parts. Loads consist of wye and delta connected

spot, unbalanced, and distributed loads. They are mixture ofconstant kW, kVAR, and Z as given in the appendix. Also,

balanced three phase and single phase shunt capacitors are

connected.

Fig. 9 illustrates the ATPdraw model of the test system

including the HIF arc model. The analysis will based on

single-phase to ground fault, that most of HIF are single

phase to ground faults [14]. Many points were selected at

different locations that represent many types of loads in the

test system. The fault was applied at 20 ms and cleared at 95

ms at bus 646, bus 652, and bus 675, respectively. The buses

were selected due to their load type variety.

V

V

58

G uF

I

F

T

F

I

MODEL

dv

650

632645646

633

671

634

680

692 675

Fig. 9: The ATPdraw Model of the IEEE 13 bus test System Including the HIF

Arc Model

Fig. 10a shows the waveforms of the fault current for

single-phase to ground fault at bus 646. This bus is a single-

phase load with normal load current of 72 A. It is shown that

the bus current does not largely change during the fault. It is

shown that the fault current is 20 mA. This value is small

enough such that the over current protection does not sense it

compared with the rated current.

Fig. 10b shows the waveform of the fault current for

single-phase to ground fault at bus 675. This bus is a three-

phase unbalance load with normal load current of 97 A, 30

A, and 108 A for phases A, B, and C, respectively. The fault

is applied on phase C. It is shown that the fault current is

20.5 mA. This value is very small current compared with the

rated current.

Fig. 10c shows the waveform of the fault current for

single-phase to ground fault at bus 652. This bus is a two-

phase load with normal load current of 40.5 A and 43.8 A for

phases A and C, respectively. The fault current is 18 mA. A

new fault current profile can be notable.

0.00 0.02 0.04 0.06 0.08 0.10[s]-20

-15

-10

-5

0

5

10

15

20

[mA]

a. Bus 646

0.00 0.02 0.04 0.06 0.08 0.10[s]-25.00

-18.75

-12.50

-6.25

0.00

6.25

12.50

18.75

25.00

[mA]

b. Bus 675

0.00 0.02 0.04 0.06 0.08 0.10s-20

-15

-10

-5

0

5

10

15

20

[mA]

c. Bus 652

652

684611

Fig. 10: The HIF Current Waveform for IEEE Test System


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The change of the influence of the fault current waveform

is notable. This is due to the change in fault location which

leads to change in the impedance angle between the source

and the fault point. This change in the influence of the

waveforms and the values of the fault currents confirm the

proposed model validity.

V. CONCLUSIONS

This paper introduces a generalized HIF arc model using

ATPdraw. The presented model is based on the dynamic arc

resistance. A combination between MODELS and TACS in

ATPdraw are used. The presented HIF arc model combines

between the simplicity of MODELS and the flexibility of

TACS. MODELS program is used in basic and iterative

equation processing. Whereas, TACS is used to enable the

user to input any type of control waveforms and/or reset

signals. This makes any type of faults, fault constants,

and/or affected power system constants can be manipulated

through simple terminals. So, the proposed model avoids the

complexity of existing TACS models and adds a flexible

control to the traditional black box MODELS subroutines.

It is evident that, each part of the presented model can be

used separately in any other universal model. Also, the parts

of the model can be modified separately. So, the presented

model can be used as a generalized model for the HIF arc

using the ATPdraw.

The presented HIF arc model is validated by comparing

the simulated results with the published results. The

comparison has shown a good agreement. Finally, the model

is used to analysis the IEEE 13-bus radial distribution test

feeder through application of many faults scenarios. The

output waveforms of the analysis confirm the model validity.

REFERENCES

[1] M. Michalik, W. Rebizant, M. Lukowicz, S- Jae Lee, and S-Hee

Kang, Wavelet Transform Approach to High Impedance Fault

Detection in MV Networks, IEEE Power Tech., pp. 1-7, June

2005.

[2] T. M. Lai, L. A. Snider, E. Lo, and D. Sutanto, High-

impedance Fault Detection using Discrete Wavelet Transform

and Frequency Range and RMS Conversion, IEEE Transaction

on Power Delivery, Vol. 20, No. 1, January 2005, pp.397-407.

[3] Nagy I. Elkalashy, Matti Lehtonen, Hatem A. Darwish,

Mohamed A. Izzularab and Abdel-Maksoud I. Taalab,

Modeling and Experimental Verification of High Impedance

Arcing Fault in Medium Voltage Networks, IEEE Transactionon Dielectrics and Electrical Insulation, Vol. 14, No. 2, April

2007, pp. 375-383.

[4] David chan, Tat Wai, and Xia Yibin, "ANovel Technique for

High Impedance Fault Identification", IEEE Transaction on

Power Delivery, Vol. 13, No. 3, July 1998, pp. 738-744.

[5] M. Kizilcay and T. Pniok, Digital System Simulation of Fault

Arcs in Power Systems, ETEP, Vol. 1, No. 1, January/February

1991, pp. 5560.

[6] M. Kizilacy and P. La Seta, Digital Simulation of Fault arcs in

Medium-Voltage Distribution Networks, 15th PSCC, Liege,

22-26 August, 2005.

[7] S. R. Nam, J. K. Park, Y. C. Kang, and T. H. Kim, "A Modeling

Method of a High Impedance Fault in a Distribution System

using Two Series Time-Varying Resistances in EMTP", Power

Engineering Society Summer Meeting, IEEE-SM, Vol. 2, 2001,

pp. 1175-1180.

[8] F. M. Uriarte, Modeling, Detection, and Localization of High-

Impedance Faults in Low-Voltage Distribution Feeders,December 15, 2003, Blacksburg, Virginia, M.Sc. Thesis.

[9] S. R. Samantaray, P. K. Dash, and S. K. Upadhyay, Adaptive

Kalman filter and neural Network Based High Impedance Fault

Detection in Power Distribution Networks, Electrical power

and Energy System 31, 2009, pp. 167-172.

[10] S. R. Samantaray and P. K. Dash, ''High Impedance FaultDetection in Distribution Feeders using Extended Kalman Filter

and Support Vector Machine'',Euro. Trans. Electr. Power 2010,

pp. 382393.

[11] Tao Cui, X. Dong, Z. Bo, A. Kilmek, and A. Edwards,

"Modeling Study for High Impedance Fault Detection in MV

Distribution System'', Universities Power Engineering

Conference, UPEC 2008, pp. 1-5.

[12] Lszl Prikler and Hans Kristian Hidalen, "ATPdraw Version5.6 for Windows 9x/NT/2000/XP/Vista - Users' Manual",

November 2009.[13] IEEE Working Group on Distribution Planning, Radial

Distribution Test Feeders, Transactions on Power Systems,

Vol. 6, No. 3, August 1991.

[14] PSRC Working Group D15, "High Impedance Fault Detection

Technology", Report of PSRC, March 1, 1996.

APPENDIX

IEEE 13 Bus Test System Load Data

Ph-1 Ph-2 Ph-3Node Load

Model kW kVAr kW kVAr kW kVAr

634 Y-PQ 160 110 120 90 120 90

645 Y-PQ 0 0 170 125 0 0

646 D-Z 0 0 230 132 0 0

652 Y-Z 128 86 0 0 0 0

671 D-PQ 385 220 385 220 385 220

675 Y-PQ 485 190 68 60 290 212

692 D-I 0 0 0 0 170 151

611 Y-I 0 0 0 0 170 80

TOTAL 1158 606 973 627 1135 753

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