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Preparation of Transient Simulation Data for PSCAD Relay Case Study of Manitoba Hydro D72V Transient Relay Testing Randy Wachal Ding Lin Manitoba HVDC Research Centre Manitoba Hydro Abstract: This paper presents the procedure for transient PSCAD Relay model. A series of transient fault efficiently preparing the data necessary to perform a cases to represent various fault conditions and current [1]PSCAD Relay transient simulation study for relay flows are described. In general, transient testing allows a [2]testing. An existing 1300+ bus ASPEN Oneliner phasor much more complete suite of cases to be used for testing, based system model was converted to an equivalent 4-bus including such items like applications of the fault at any PSCAD Relay model. A comparison of steady state 60 Hz phase angle, variation in telecommunication and breaker results for both 3 phase and single line to ground faults operating times. A set of fault cases was utilized for verify that the transient and phasor system models are transient testing of line protection for a new 230 kV equivalent. The transient model can be used with transmission line (D72V) recently commissioned in confidence to generate transient fault waveforms simply Manitoba Hydro system. not possible to develop with phasor based simulation method. Transient fault waveforms were used to investigate the operations of the forward and reverse 2. DEVELOPMENT OF SYSTEM MODEL ground ...
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Preparation of Transient Simulation Data for PSCAD Relay
Case Study of Manitoba Hydro D72V Transient Relay Testing
Randy Wachal
Manitoba HVDC Research Centre
Ding Lin
Manitoba Hydro
Abstract:
This paper presents the procedure for
efficiently preparing the data necessary to perform a
PSCAD Relay
[1]
transient simulation study for relay
testing. An existing 1300+ bus ASPEN Oneliner
[2]
phasor
based system model was converted to an equivalent 4-bus
PSCAD Relay model. A comparison of steady state 60 Hz
results for both 3 phase and single line to ground faults
verify that the transient and phasor system models are
equivalent. The transient model can be used with
confidence to generate transient fault waveforms simply
not possible to develop with phasor based simulation
method.
Transient
fault
waveforms
were
used
to
investigate the operations of the forward and reverse
ground directional overcurrent elements of the Nxtphase
L-PRO line protection relay.
Keywords
Relay Testing, Transient Simulation, PSCAD
Relay, System Equivalent, ASPEN Oneliner (ASPEN)
1.
INTRODUCTION
Transient testing of protection relays with waveforms of
the same quality and frequency response of the voltage and
current waveforms the protection uses from the system PT
and CT is becoming increasingly important
[3]
. This is true
especially as the speed and complexity of the digital
protection system increases. A form of dynamic testing has
been
developed based on the steady
state phasor solutions.
The pre-fault, fault and post fault steady state phasors
would be calculated using a phasor based simulation
program like ASPEN or PTI PSS/E. The prefault, fault
and post fault phasors for voltage and current would be
converted into time domain waveforms and then simply
concatenated together to create a type of dynamic
changing time domain waveforms. This dynamic STATE
testing ignores any transient effects when the fault was
applied or removed and works reasonable well there is a
high level of filtering applied by the protection relay.
A more accurate representation of the transient waveforms
is to simulate the power system using a time domain
simulation program to directly develop the transient fault
waveforms. These waveforms include all of the transient
effects.
One of the difficulties encountered is developing
the data necessary for time domain or PSCAD Relay
simulation. In many utilities there is a large database of
phasor based simulation models, which have been
developed over a period of many years.
This paper
illustrates the process of converting and validating the
existing phasor based 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 -
FT6
F6
F2
F7
FT7
F4
St. Vital 230 kV
Bus1
F5
FT5
V
Ph
230.0 [kV], 60.0 [Hz]
100.0 [MVA]
Z1 = 71.73 [ohm] /_ 47.39 [°]
V
Ph
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
F1
FT1
V
Ph
230.0 [kV], 60.0 [Hz]
100.0 [MVA]
Z1 = 43.05 [ohm] /_ 63.9 [°]
V
Ph
230.0 [kV], 60.0 [Hz]
100.0 [MVA]
Z1 = 6.11 [ohm] /_ 84 [°]
V4
V5
F3
FT3
V1
FT4
3 Phase
RMS
V4rms
B3
27.16 [MVAR]
-94.01 [MW]
V6
Aspen1
B1
0.005922 [MVAR]
-0.0001996 [MW]
15 km
D36R1
B2
0.01282 [MVAR]
0.001017 [MW]
19.46 km
D5R
19.46 km
D13RD16R
B5
32.3 [MVAR]
-150.7 [MW]
B6
-31.4 [MVAR]
151.2 [MW]
B4
-32.35 [MVAR]
95.48 [MW]
V
3
r
m
s
3
P
h
a
s
e
R
M
S
V3
FT8
Aspen2
Aspen4
Ridgeway 230 kV
Bus 4
19.40 km
R32VD72V
Aspen4
16.41 km
R23R
20.07 km
D36RD72V
16.4 km
D72V_1
3
P
h
a
s
e
R
M
S
V5rms
3
P
h
a
s
e
R
M
S
V1rms
3
P
h
a
s
e
R
M
S
V6rms
3
P
h
a
s
e
R
M
S
V2rms
V2
FT2
F8
19.43 km
R33V
Figure 1: PSCAD Relay System
SLG Fault at Dorsey
Voltage
(V0)
at:
ASPEN
PSCAD*
*
Differenc
e
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
1
I1+
1
I1+ph
1
I1_0
1
I10ph
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 -- 51NAlarm
-10.0
6.0
Dorsey
2002/May/16 08:18:31.071181
Rosser
D72V Line Current A
-4.0
4.0
Dorsey
2002/May/16 08:18:31.071181
Rosser
D72V Line Current B
-4.0
4.0
Dorsey
2002/May/16 08:18:31.071181
Rosser
D729 Line Current C
-5.0
6.0
Dorsey
2002/May/16 08:18:31.071181
Rosser
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 -
