Preparation of Transient Simulation Data for PSCAD Relay Case Study of Manitoba Hydro D72V Transient Relay Testing

Randy Wachal Manitoba HVDC Research Centre

Abstract: This efficiently preparingPSCAD Relay [1] ttesting. An existing 1based system model PSCAD Relay modelresults for both 3 phverify that the transequivalent. The traconfidence to generanot possible to devmethod. Transient investigate the operground directional oL-PRO line protection Keywords Relay TesRelay, System Equiva

1. Transient testing of the same quality and current waveforms thand CT is becoming especially as the spprotection system incbeen developed basedThe pre-fault, fault would be calculatedprogram like ASPENand post fault phasoconverted into time concatenated togethchanging time domaitesting ignores any applied or removed ahigh level of filtering A more accurate repris to simulate the psimulation program twaveforms. These weffects. One of the the data necessary simulation. In manyphasor based simudeveloped over a pillustrates the procesexisting phasor bas

Ding Lin Manitoba Hydro

paper presents the procedure for the data necessary to perform a ransient simulation study for relay 300+ bus ASPEN Oneliner [2] phasor was converted to an equivalent 4-bus . A comparison of steady state 60 Hz ase and single line to ground faults ient and phasor system models are nsient model can be used with te transient fault waveforms simply elop with phasor based simulation fault waveforms were used to

ations of the forward and reverse vercurrent elements of the Nxtphase relay.

ting, Transient Simulation, PSCAD lent, ASPEN Oneliner (ASPEN)

INTRODUCTION

protection relays with waveforms of frequency response of the voltage and e protection uses from the system PT increasingly important [3]. This is true eed and complexity of the digital reases. A form of dynamic testing has on the steady state phasor solutions. and post fault steady state phasors using a phasor based simulation or PTI PSS/E. The prefault, fault

rs for voltage and current would be domain waveforms and then simply er to create a type of dynamic n waveforms. This dynamic STATE transient effects when the fault was nd works reasonable well there is a

applied by the protection relay.

esentation of the transient waveforms ower system using a time domain o directly develop the transient fault aveforms include all of the transient difficulties encountered is developing for time domain or PSCAD Relay utilities there is a large database of lation models, which have been eriod of many years. This paper s of converting and validating the ed ASPEN system model into a

transient PSCAD Relay model. A series of transient fault cases to represent various fault conditions and current flows are described. In general, transient testing allows a much more complete suite of cases to be used for testing, including such items like applications of the fault at any phase angle, variation in telecommunication and breaker operating times. A set of fault cases was utilized for transient testing of line protection for a new 230 kV transmission line (D72V) recently commissioned in Manitoba Hydro system.

2. DEVELOPMENT OF SYSTEM MODEL 2.1 System Model PSCAD/Relay case for the system under investigation was developed from an ASPEN case. ASPEN is a fundamental frequency fault program, used routinely by Manitoba Hydro for protection studies. Manitoba Hydro maintains a relatively large (1300+ bus) system model in ASPEN. The conversion of a large system into a transient simulation can be a significant effort. For the D72V test program, the ASPEN system model was converted into a 4-bus PSCAD Relay case using equivalent voltage sources at each bus to represent the remaining system. A comparison between results from the PSCAD Relay case for three phase and single line to ground (SLG) faults at each bus and the ASPEN simulation was performed with matching results. This validation verified the system equivalence techniques used to reduce the system size and the system model conversion.

2.2 Procedure for ASPEN Equivalence Network and Conversion The Manitoba Hydro ASPEN system models consist of approximately 1300 busses. This system was converted to a 4-bus system including eight 3-phase transmission sections and three 6-phase transmission sections. A 6-phase line section includes the mutual coupling effects when two 3-phase circuits share the same tower. The PSCAD Relay Case developed for this testing is shown in Figure 1. A step-by-step illustration of the process of developing equivalent sources at the 4 bus locations within the ASPEN program is described in details in its on-line help menu as well as its user manual (Reference 2: Appendix

- 1 -

G). This process is relative easy and would require less than an hour of time for any user with some familiarity of using the ASPEN program. Prior to proceeding to conversion to PSCAD, it is important to ensure the faults results generated in the full ASPEN system are the same as the same fault case in the equivalence or reduced ASPEN system Once the equivalent electrical system is developed and validated in ASPEN, this data is used to develop the PSCAD Relay case. It is possible to develop a PSCAD Relay case from a blank sheet but it is much quicker to select a base PSCAD Relay from the prepared examples. This example case is then modified into the study case. Additional Transmission lines, breakers and voltage sources can be added by copy and paste commands. The following steps illustrate the process. Step 1: Select the appropriate PSCAD Relay Example

case. Step 2: Enter the Positive and zero sequence impedance for

each voltage source. Add additional voltages sources as required.

Step 3: Enter the transmission line data parameters either using the direct R, X, B values from the ASPEN model or if available, transmission tower geometry and conductor information in a PSCAD traveling transmission line traveling wave model. If mutual coupled transmission are utilized remember to input transmissions as 6 or more conductor elements.

PSCAD supports mutual coupling of up to 20 conductors. Add additional transmission lines as required.

Step 4:Add Coupled Pi branch sections to accommodate the fictitious branch data generated by the ASPEN Equivalence procedure. This data will have series R and X but no shunt B data.

Step 5: Run the PSCAD solutions with no faults applied and adjust the voltage source magnitude and angle to give the desired prefault bus voltages and power flow.

At this point the PSCAD Relay system model is ready for comparing steady state faults results with results from ASPEN case or to proceed with development of transient test waveforms. Permanent single and three-phase faults were applied and compared with steady state solutions with ASPEN results for the same case. 2.3 Validation of Transient System Model

In order to compare PSCAD and ASPEN results it is

important to remember ASPEN simulation results can be shown as phase or sequence quantities and that these results are steady state in nature. PSCAD provides a time domain voltage and current waveform similar to what can be measured on the power system. In order to compare ASPEN and PSCAD results, the time domain waveforms must be converted to a phasor equivalent. Within PSCAD there are “RMS” measurement blocks and 3 phase on-line

- 2 -

FT6F6

F2

F7FT7

F4

St. Vital 230 kVBus1

F5FT5

V Ph

230.0 [kV], 60.0 [Hz]100.0 [MVA]

Z1 = 71.73 [ohm] /_ 47.39 [°]

VPh

230.0 [kV], 60.0 [Hz]100.0 [MVA]

Z1 = 109.05 [ohm] /_ 62.52 [°]

Rosser 230 KV Bus 3

Dorsey 230 kV Bus 2

F1FT1

VPh

230.0 [kV], 60.0 [Hz]100.0 [MVA]

Z1 = 43.05 [ohm] /_ 63.9 [°]

VPh

230.0 [kV], 60.0 [Hz]100.0 [MVA]

Z1 = 6.11 [ohm] /_ 84 [°]

V4

V5F3

FT3

V1

FT4

3 PhaseRMSV4rms

B3

27.16 [MVAR]-94.01 [MW]

V6

Aspen1

B1

0.005922 [MVAR]-0.0001996 [MW]

15 kmD36R1

B2

0.01282 [MVAR]0.001017 [MW]

19.46 kmD5R

19.46 kmD13RD16R

B5

32.3 [MVAR]-150.7 [MW]

B6

-31.4 [MVAR]151.2 [MW]

B4

-32.35 [MVAR]95.48 [MW]V3rm

s3 Phase

RM

S

V3

FT8

Aspen2

Aspen4 Ridgeway 230 kVBus 4

19.40 kmR32VD72V

Aspen4

16.41 kmR23R

20.07 kmD36RD72V

16.4 kmD72V_1

3 PhaseR

MS

V5rms

3 PhaseR

MS

V1rms

3 PhaseR

MS

V6rms

3 PhaseR

MS

V2rms

V2

FT2

F8

19.43 kmR33V

Figure 1: PSCAD Relay System

SLG Fault at Dorsey

Voltage (V0) at: ASPEN PSCAD*

*

Difference

between ASPEN

& PSCAD**

% Error between ASPEN

& PSCAD*

* Dorsey Bus 2 12.6 13.18 0.58 4.6%

Ridgeway Bus 4 2.9 4.174 1.27 43.9% Rosser Bus 1 5.4 6.675 1.28 23.6% St Vital Bus 3 1.6 2.561 0.96 60.1%

Current (3I0): Bus 3 R33V I1 28 17.54 -10 -37.4% Bus 2 D36R I2 297 412.9 116 39.0% Bus 3 D72V I3 248 298.6 51 20.4% Bus 2 D72V I4 248 296.4 48 19.5% Bus 4 D36R I7 297 414.5 118 39.6% Bus 2 D13R I8 387 424.9 38 9.8%

I fault 34114 36250 2136 6.3%

I1a

I1b

I1c

1I1+

1I1+ph

1I1_0

1I10ph

XA

XB

XC

Ph+

Ph-

Ph0

Mag+ Mag- Mag0

(7)

(7)

(7)

(7) (7) (7)

dcA dcB dcC

F F T

F = 60.0 [Hz]

1

Figure 2: PSCAD FFT Block with Sequence Outputs

FFT processing blocks that can provide positive, negative and zero sequence information. Figure 2 shows the PSCAD FFT block.

The results for comparison between the full (1300+ Bus) ASPEN and the reduced (4-bus) PSCAD system illustrate a close match for the positive and zero sequence voltages, branch currents and fault currents. Samples of results for a SLG and 3-phase fault are presented for a fault on Dorsey bus are presented in Table 1 and 2. Results are presented in both absolute value and % error. Care in interpreting results is required. For example, in the SLG fault case the zero sequence voltages at the non-faulted busses show a large percentage error, while the absolute values are within a very acceptable 1.3 volts.

Table 1: Single Line to Ground Fault at Dorsey Bus

3 Phase Fault at Dorsey

Voltage (V+) at: ASPEN PSCAD

Difference between

ASPEN & PSCAD

% Error between Aspen & PSCAD

Dorsey Bus 2 0 0 0 0.0%

Ridgeway Bus 4 36.1 36.8 0.7 1.9%

Rosser Bus 1 23.4 24.5 1.1 4.7%

St Vital Bus 3 45.1 45.77 0.67 1.5% Current (I+): Bus 3 R33V I1 974 963 -11 -1.1%

Bus 2 D36R I2 2177 2223 46 2.1%

Bus 3 D72V I3 1759 1779 20 1.1%

Bus 2 D72V I4 1759 1782 23 1.3%

Bus 1 R23R I5 1600 Bus 3 R32V I6 963 933 -30 -3.1%

Bus 4 D36R I7 2177 2221 44 2.0%

Bus 2 D13R I8 2491 2609 118 4.7%

I fault 37484 37150 -334 -0.9%

The minor differences can be attributed to the following: 1.

2.

3.

4.

Equivalence: Results for ASPEN system are 1300+ busses, while PSCAD are for the 4 bus system. Note: When a 4-bus ASPEN system was solved the results between ASPEN and PSCAD are within 1%. Prefault load flow: ASPEN has fault calculations performed from a flat start position, while PSCAD solves the system. Even when the power flow is reduced to zero, or near zero, the effects of the transmission line charging are present. Transmission lines are not identically modeled. ASPEN uses a coupled pi model with lumped R, X and B values. PSCAD calculates the traveling wave parameters for the line based on geometrical conductor configuration and conductor data. The 60 Hz lumped parameters calculated by PSCAD are close but not precisely the value used in ASPEN.

Table 2: Three-Phase Fault at Dorsey Bus Mutual Coupling. The mutual coupling for some other transmission lines on the same right of way as D72V were not modeled in PSCAD but in ASPEN, because the geometry data for these lines was not readily available.

- 3 -

3. Development of Transient Test Cases 3.1 The Problem D72V is a new transmission line with portion of it constructed on the same towers of an existing line, and on the same right of way (ROW) with some additional existing lines. During state simulation testing of the relay, the directional ground overcurrent elements of the relay were giving some questionable results for some current reversal conditions due to mutual coupling effect. It was not clear whether the operation of these fast reacting elements is affected by the unrealistic simulation of the transition between states, or by different fault conditions such as fault inception angle or prefault line loading. The sensitivity of the forward and reverse ground overcurrent elements 67F and 67R of the Nxtphase L-PRO relay on the new D72V line was the focus of this transient testing program. 3.2 The Test Plan A number of PSCAD/Relay simulations were performed to generate the required testing waveforms. An “A” phase to ground fault was applied at the Ridgeway end of D36R, at Fault Location F3 on Figure 1, in order to produce a forward reverse current flow on D72V. The application of fault angle was modified from 0 to 180 degrees in 30-degree steps; and the power flow from Dorsey to St. Vital on D72V was adjusted from 0, 100 and 200 MW. In addition, the telecommunications delay between line D36R

breaker opening at the Ridgeway, B1 shown in Figure 1, and the breaker opening at the Dorsey end, B2 shown in Figure 1, was selected at 30 or 100 msec. This set of tests was performed using the multiple run feature of PSCAD, generating a total of 42 test cases. Each test case generated the three voltage and three current signals required for transient testing of the Dorsey and St Vital D72V protection system. An example of the waveforms is shown in Figure 3. Initially 200 MW is flowing on D72V. A SLG fault is applied at Ridgeway end of the D36R line. The voltage and currents presented are recorded at the Dorsey end of D72V. When the fault is applied, the D72V relay at Dorsey end sees reverse current. The Ridgeway breaker opens 50 msec (3 cycles) after the fault, changing the direction of the current as seen at the Dorsey end of D72V. The breaker on D36R remote from the fault opens 30 msec after the local end (approximately 2 cycles) and removes the fault current flow from D72V. These faults waveforms were used for real time transient testing of the D72V. The overall development time for PSCAD Relay Case development, validation with ASPEN steady state and transient case study plan was a couple of days, with the bulk of effort in the validation testing. 3.3 Results of the Testing Program The transient waveforms were played into a Nxtphase L-PRO relay configured with the appropriate setting D72V

- 4 -

DorseyD72V-2002-05-16_13.18.31.071 : 2002-05-16 08:18:31 .071 -- 51N Alarm

-10.0

6.0

Dorsey2002/May/16 08:18:31.071181Rosser

D72V Line Current A

-4.0

4.0

Dorsey2002/May/16 08:18:31.071181Rosser

D72V Line Current B

-4.0

4.0

Dorsey2002/May/16 08:18:31.071181Rosser

D729 Line Current C

-5.0

6.0

Dorsey2002/May/16 08:18:31.071181Rosser

3Io_Main

L

L

L

ProLogic 1

ProLogic 2

Comm. Scheme Send

Figure 4: Sample Relay Recording at D72V Dorsey Figure 3: Sample Transient Test Waveforms Voltage and Current at D72V Dorsey

files. Figure 3 illustrates the transient waveforms generated by PSCAD Relay, which were played into the relay. Figure 4 shows a set of sample waveforms recorded by the L-PRO relay. The operation of the 67F and 67R elements was verified over a large number of cases during a one-day testing period. The transient testing program confirmed that the relay operation was not dependent on the prefault loading, fault inception angle or the protection telecommunication delay on the faulty line, but the level of positive sequence component of the fault current has an effect on the operation of the directional ground overcurrent elements. 4. CONCLUSIONS Transient simulation testing of protection offers many advantages over the more traditional methods. Since the transient waveforms produced represent realistic voltage and current waveforms that the protection sees in service, the overall confidence in the testing results is greatly increased. The process to develop a transient system simulation model from a phasor-based system is not difficult. With PSCAD/Relay, it was possible to develop a study system that produced the same results as a fundamental frequency program. Once the positive and zero sequence networks were confirmed, the development of particular study cases of interest was performed. These PSCAD/Relay generated waveforms were injected into the protection system using a real time transient playback system, allowing a thorough confirmation of the relay

performance. The development of a transient test plan can be performed within PSCAD Relay with minimum effort. These transient test waveforms can be used to verify the relay performance with confidence for either single or GPS based end-to-end testing. The operation of the Nxtphase L-PRO relay was verified over a large number of cases during a one-day laboratory testing period. 5. REFERENCE [1] “PSCAD/Relay Installation and Operations

Manual”, Manitoba HVDC Research Centre, Aug 2001.

[2] “ASPEN Oneliner V2001 User’s Manual” [3] M.S. Sachdev, T.S. Sidhu, P.G. McLaren, Issues

and Opportunities for Testing Numerical Relays, IEEE Power Engineering Society Summer Meeting, Seattle, Washington, USA, 16 – 20 July 2000.

- 5 -