Journal of Power and Energy Engineering, 2014, 2, 244-251
Published Online April 2014 in SciRes. http://www.scirp.org/journal/jpee
http://dx.doi.org/10.4236/jpee.2014.24035
How to cite this paper: Zhang, K.J., Chen, L., Xia, Y.J., Lei, Y., Shu, X., Li, H.X., Wang, T. and Du, Z.N. (2014) A Smart Substation
Field Secondary Device Testing Technique Based on Recurrence Principle. Journal of Power and Energy Engineering, 2,
244-251. http://dx.doi.org/10.4236/jpee.2014.24035
A Smart Substation Field Secondary Device
Testing Technique Based on Recurrence
Principle
Kanjun Zhang1*, Lei Chen2, Yongjun Xia1, Yang Lei1, Xin Shu1, Hengxuan Li1, Ting Wang1,
Zhenan Du1
1State Grid Hubei Electric Power Research Institute, Wuhan, China
2Wuhan Fangyuan Dongli Electric Power Technology Center, Wuhan, China
Received December 2013
Abstract
According to the demand of substation secondary device dynamic performance testing, a smart
substation field testing technique based on recurrence principle is proposed in the paper, and the
characteristics of smart substation secondary device digitization and information sharing are
used by the technique. The principle of testing technique is as follow: the digital simulation model
is constructed on the basis of the substation’s actual construction, then the simulating data highly
similar to substation’s actual electric quantity transient process is generated, at last, the substa-
tion digital secondary device can be tested by using data “recurrence” technique. The testing tech-
nique is verified and applied by constructing testing system, the application results show that the
technique can effectively perform field test on the dynamic performance of digital secondary de-
vice , and the technique has good engineering implementation and application value.
Keywords
Smart Substation; Secondary Device; Dynamic Performance; Data Recurrence; Field Testing
Technique
1. Introduction
In conventional substation, the performance of secondary equipments (e.g. relay protection and automatic de-
vices) is usually tested by using protective relay test device, but the method is only for secondary equipments’
static performance, and in some cases (e.g. fault analysis), the dynamic performance of secondary equipment
needs to be tested [1,2]. Using digital-analogical hybrid simulation system (e.g. RTDS, ADPSS) can test the
dynamic performance of secondary equipment effectively [3,4], but the test can only be carried out in laboratory,
the test period is usually long, and the number of tested equipments is also limited, in short the method cannot
perfectly fit the requirements of actual operation. Using portable testing simulation devices is another method,
*Corresponding author.

K. J. Zhang et al.
245
the device contains digital simulation models, can output voltage, current and switch signals which can test the
dynamic performance of secondary equipments [5,6], moreover the device can be carried to substation feasibly.
However, the portable testing device can only stor e certain fixed simulation model which may be different from
the actual structure of power grid, the limitation lead to negative effectiveness of dynamic tests, so how to test
the dynamic performance of secondary equipments according to engineering need is a technical issue to be re-
solved.
Although the field testing methods and modes of secondary equipment in smart substation are not essentially
different from that of conventional substation, the signal transmission modes of secondary equipment in smart
substation are vary from conventional substation extremely [7-9]. So based on the features such as secondary
equipment digitalization and information sharing in smart substation , testing the secondary equipment’s dynam-
ic performance in substation can be done.
On the basis of above idea, a new field testing technology of se condary equipment in smart substation is pre-
sented in the paper, and its validity will be verified by corresponding test system.
2. Field Dynamic Testing Analysis of Secondary Equipment in Smart Substation
In conventional substation, the signals inputted to secondary equipment are electrical and switch (Figure 1(a) ).
During dynamic performance testing, the change of input signals’ value and phase may very complex in order to
comply with power grid transient process, in this case the manual operation is difficult to simulate effectively.
But because of the change of signal transmission modes in smart substation, manual input dynamic signal during
the test becomes possible. At present, the relay protection and automatic devices in smart substation generally
use the “point-to-point sampling and tripping” method for transmissing signals [10], the process is shown in
Figure 1(b).
In Figure 1, whether the transformers used in smart substation are conventional or electronic, the signals in-
putted to relay protection and automatic devices are all digital message. So if the dynamic test signals are
changed into corresponding digital messages (SV, GOOSE message), and input the messages to the secondary
equipments, then dynamic testing can be done.
In total, the conditions of secondary equipments dynamic performance field testing in smart substation are as
follows:
1) Similar to actual operating condition s of sub station. The output test signals should simulate the co rr e s-
ponding operating conditions in substation, that is to say, the transient process of test signals should be similar to
that of actual electrical and switch quantities.
2) The format of test signals complies with the requirement of digital secondary equipment. Test signals’
format complies with IEC61850 standard digital message, and the signals can be directly used to test.
3) Test signals can be carried or transmitted to substation to test secondary equipments.
4) Test signals have synchron ic output function. As to transformer protection and bus differential protection
which may require signal outputted from more than one test equipment, the output signal of each test equipment
should be synchronized.
Conventional current
and voltage
transformers
Switch
signal
Secondary
electrical
quantities singal
Communication
message
Telecontrol equipment
Relay protection and
automatic devices
Conventional or
electronic
transformer
Merging unit
Intelligent
terminal
Relay protection and
automatic devices
Switch
signal
FT3 message
SV
message
GOOSE
message
MMS message
Station control layer device
(a) (b)
Figure 1. Schematic diagram of substation secondary device
signal transmission comparison. (a) Conventional substation;
(b) Smart substation.

K. J. Zhang et al.
246
3. New Field Test Technology of Secondary Equipment in Smart Substation
3.1. Principle of New Test Technology
The new field test technology of smart substation secondary equipment (new test technology in short) proposed
in the paper is composed of five parts, they are generating, conv er sion, storage, output, and synchronization of
the dynamic signals. The specific principle is: Step 1, generate dynamic test signals by simulating substation’s
operating conditions, and the trans ient process of signals is similar to the actual electrical quantities. Step 2,
convert the signals to data messages which meet requirements of IEC61850 protocol. Step 3, store the messages
in test devices. Step 4, test the dynamic performance of digital secondary equipment by output the messages in
substation. And during the test, the test signals outputted by multiple test dev ices can be synchronized by coor-
dination of clock signal.
3.2. Implementation of New Test Technology
The implementation principle of new test technolog y is shown in Figure 2.
The test system in Figure 2 is composed of five parts: signal source unit, signal converting unit, signal sto-
rage unit, test output unit and signal synchronizing unit. The specific implementation scheme of each part is as
follows.
3.2.1. Signal Source Unit
Constitute the signal source unit by using digital simulation syste m. The implementation procedure is as follows:
Firstly, establish the corresponding digital simulation model of power grid and substations, Secondly, calculate
by electrical-electromagnetic transient hybrid simulation mode [11-13]. Specifically, the model of substations
and nearby power grid is used by electromagnetic transient simulation model, the other part of power grid uses
electromechanical transient simulation model. The above technical can reduce the negative influence of model
simplifying on the calculation results accuracy. At last, produce the simulation results which are similar to the
actual electrical quantities by simulatin g various operating conditions of substation.
3.2.2. Signal Conversion Unit
Convert the output signals to messag es which meet the requirements of IEC61850 protocol, there are two con-
version methods can be chosen.
1) Method 1: convert the output signals directly, this conversion method requires less links, but need to de-
velop a special signal conversion equipment.
2) Method 2: convert the output signals to normal secondary electrical and switch quantities by using physical
interface devices and power amplifiers, and then turn the quantities to data messages which meet the require-
ments of IEC61850 protocol by merging units and smart terminal. This conversion method has more links, but
more mature and easy to imply.
Method 2 is chosen based on above analysis.
3.2.3. Signal Storage and Output Unit
Recurrence output the data messages in substation, reproduce the electrical quantities’ transient process during
actual operating condition of substation, and test the secondary equipment. The “recurrence” output of messages
Signal
synchronization
unit Test messages
Test output
unit
Digital secondary
equipment
Smart
substation
Signal
generating
Signal
converting
unit
Signal
Source
unitData
messages
Signal
storage
unit
Figure 2. Principle diagram of new testing
technique.

K. J. Zhang et al.
247
can be achieved in two ways:
1) Convert the data messages to recorded data (COMTRADE format), store the data into digital relay test de-
vice. And then convert the recorded data to IEC61850-9-2 data messages by using the recorded data recurrence
function of digital relay test device.
2) Recurrence output the data messages after edit. This method does not need conversion, but need to develop
a special data processing software.
The first method is used because it is easy to implement.
3.2.4. Signal Synchronizing Unit
When carry out test of the secondary equipments which need multi-interval messages, single test equipment may
not meet the requirements. Then multiple test devices will be used, and the test signals outputted by these test
devices can be synchronized by the alignment time signal which is outputted by signal synchronization unit. The
alignment time mode such as IRIG-B or IEEE1588 can be used [14,15].
3.3. Test System
Building test system which is shown in Figure 3.
In Figure 3, the signal source unit is consisted of advanced digital power system simulator (ADPSS) and
physical interface device (PID-B1). Signal conversion unit includes power amplifier (PW60A), merging unit
(MU) and smart terminal (ST). Signal storage unit contains network analyzer (ZH-5N) and portable computers
(PC). Output unit is digital relay protection device (PNF801). Synchronization unit uses clock synchronization
device (ZH-502).
3.4. Validation of New Test Technology
The test process has multiple links, so validity of signals transmitting needs to be verified. In addition, the syn-
chronization of signals outputted from different test equipment needs also to be verified. The test model is
shown in Figure 4. The main component of model is a three winding transformer, the test system has three in-
tervals, it includes three Merging units, electronic current and voltage transformers (ECT, EVT), three sets of
digital relay test device are used.
Figure 3. Schematic diagram of test system structure.
Figure 4. Schematic diagram of testing model 1.

K. J. Zhang et al.
248
1) The Validity of Signal Recurrence
Take phase A ground fault (Figure 4, K1) of transformer 220 kV side for example, compare the output sig-
nals of ADPSS and test output unit (Figure 3, link (1) and (2)), then the accuracy of recurrence data can be
checked. The comparison results are shown in Table 1 and Figure 5.
In Figure 5, red dashed and solid black lines represent the output data of digital relay test device and ADPSS
respectively. From the comparison results in Table 1 and Figure 5, the error is very low, then the validity of re-
currence output signal results is verified.
2) Verification of Signal Synchronization
Take phase A and B metallic short circuit fault (Figure 4, K2) of transformer 110kV side for example to test
the synchronization of output signals, IRIG-B method is used, the transformer differential current around the
fault time is shown in Figure 6.
Because K2 is located out of transformer differential protection zone, the differential current is approximately
zero when the output signals of all digital relay test devices are synchronous. The differential current of three
phases in Figure 6 is less than 2.4 × 10−3 Ie (transformer rated current), so the synchronization of test messages
is verified.
4. The Application of New Test Technology
Testing the transformer protection device of a 220 kV smart substation with the new test technology. Building
the test model according to the actual structure of substation, the model and associated test equipment is shown
in Figure 7.
In Figure 7, the test model includes 220 kV double bus bar, a three winding transformer and a 220 kV trans-
mission line. So test system has seven intervals, it contains seven combined unit (MU1-MU7), six sets of intel-
ligent terminals (ST1-ST6), six sets of electronic current transformer (ECT1-ECT6), electronic voltage trans-
former (ETV1-ETV6) and corresponding collector. The output unit consists of seven same type digital relay test
devices. K1-K5 is short circuit fault point.
Table 1. Comparison of transformer phase A current value.
No. Measuring points Pre-fault Post-fault
Simulation Recurrence Error Simulation Recurrence Error
1 220kV Side Current (A) 380.7 380.1 0.17% 3323.1 3321.4 0.05%
2 110kV Side Current (A) 575.4 574.9 0.09% 557.6 557.4 0.03%
3 10kV Side Current (A) 1941.0 1941.4 0.02% 1846.9 1846.1 0.04%
Tag: The current in Table 1 is RMS of one cycle pre-fault and post-fault.
Figure 5. Comparison of phase A current waveform.

K. J. Zhang et al.
249
Figure 6. Effective value of transformer differential current.
Bus
connection
breaker
220kV line
220kV busⅠ
ECT5ECT4
ECT3
EVT5
EVT3
ECT6
220kV bus Ⅱ
MU3
EVT4
EVT6
220kV
breaker
110kV
breaker 10kV
breaker
Line breaker 2
Line
breaker 1
MU2MU1
110kV bus10kV bus
EVT1EVT2
ECT1ECT2
MU4
Transformer
MU5
MU7
ST2ST1
ST3
ST5
ST6
ST4
Infinite bus
system
K3
Load Load
K4
K1
K2
MU6
Figure 7. Schematic diagram of testing model 2.
The test items include: metallic short circuit which occurs in and out of transformer differential protection
zone, transition resistance short circuit, transitional fault, power grid oscillation and short circuit during oscilla-
tion etc. The last three types in above faults can better test the dynamic performance of secondary equipment,
the testing results are shown in F igures 8 and 9.
In F igures 8 and 9, UA, UB and UC are three-phase voltage of 220 kV bus bar, IA, IB and IC are three-phase
current of transformer 220 kV side, T1 is protection starting signal (switch signal), T2 is protection operating
signal, the starting time is 0ms.
In Figure 8, during power grid oscillation, phase A ground fault occurred on 110 kV bus bar (Figure 7, K3,
outside of transformer differential protection areas) is simulated. 507 ms after the fault occurring, the multiple
voltage over-current protection segment I of transformer 110 kV side operates (protection delay setting is 500
ms), and the breakers of transformer three sides trip, other protections have not operated.
In Figure 9, a transitional fault is simulated. At first, Phase A ground fault (Figure 7 K3) occurs during pow-
er grid oscillation, and then after 60 ms, phase B (Figure 7 K2, inside of transformer differential protection
areas) occurs ground fault. During the test, 79 ms after the protection start (T1), the transformer ratio differential
protection operates, and the breakers of transformer three sides trip.
Above experiment results show that the dynamic performance of digital secondary equipment can be tested
effectively by the new testing technology.

K. J. Zhang et al.
250
Time/ms
-600 -400 -2000200400 600
-100
0
100
UA / V
-600 -400-2000200400 600
-100
0
100
UB / V
-600 -400-2000200400 600
-100
0
100
UC/ V
-600 -400-200 0200400 600
-10
0
10
IA/A
-600 -400-2000200400 600
-10
0
10
IB/A
-600 -400-2000200400 600
-10
0
10
IC/A
-600 -400-2000200400 600
0
20
40
T1
-600 -400 -2000200400 600
0
20
40
T2
Figure 8. Transformer out-area fault during power grid oscil-
lation.
Time/ms
-400 -300 -200 -100 0100 200 300
-100
0
100
UA / V
-400 -300 -200 -100 0100 200 300
-100
0
100
UB / V
-400 -300 -200 -100 0100 200 300
-100
0
100
UC/ V
-400 -300 -200 -100 0100 200 300
-10
0
10
IA/A
-400 -300 -200 -100 0100 200 300
-10
0
10
IB/A
-400 -300 -200 -100 0100 200 300
-10
0
10
IC/A
-400 -300 -200 -100 0100 200 300
0
20
40
T1
-400 -300 -200 -100 0100 200 300
0
20
40
T2
Figure 9. Transitional fault during power grid oscillation.
Acknowledgements
According to the dynamic performance test requirements of secondary equipment in substation, and considering
the features of smart substation secondary equipment such as digitization and informatization, a new field test
technology of smart substation secondary equipment based on recurrence principle is proposed in the paper, and
the technology is verified and applied. The application results show that the technology can test the dynamic
performance of secondary equipment in substation effectively, and easy to be implemented. The new technology

K. J. Zhang et al.
251
can be used to do routine maintenance and fault analysis of smart substation, so it has good application value. At
present, the new technology also needs to do further studies for the application in coordination test of multiple
protective device.
References
[1] Ye, Y.B. and Chen, S. (2010) Analysis of Successive Trips of Transformer Differential Relay and Bus Differential Re-
lay. Ele ctric Power Automation Equipment, 30, 146-148.
[2] Overman T M, Sackman R W. (2010) High Assurance Smart Grid: Smart Grid Control Systems Communications Ar-
chitecture. Smart Grid Communications, IEEE International Conference, 19-24.
[3] Mao, P., Duan, Y.Q., Xu, Y., et al. (2006) Realization of Dynamic Detecting Relay in High Voltage Line Protection
Devices. Automation of Electric Power Systems, 30, 86-89.
[4] Kuffel, R., Winnipeg, B.C., Giesbrecht, J., Maguire, T. and Wierckx, R.P. (1996) A Fully Digital Power System Simu-
lator Operating in Real Time. Electrical and Computer Engineering, 733-736.
[5] Liang, Z.C., Ma, X.D., Wang, H.X., et al. (1999) Small-Sized Real-Time Digital Simulator for the Test of Protective
relay. Automation of Electric Power Systems, 23, 27-30.
[6] Wang, Z., Zhang, M., Sun, L.S., et al. (2001) Research on DSP-Based Digital Test Equipment for Protection Relay by
Dynamic Simulation. Electric Power Automation Equipment, 21, 8-10.
[7] Reddy, M.H., Kishor, G., Satheesh, G. and Reddy, T.B. (2012) Digital Simulation of Hybrid PWM Inverter Fed Induc-
tion Motor Using Two Inductor Boost Converter. Advances in Engineering, Science and Management (ICAESM), 361-
366.
[8] Minami, Y., Yamanaka, N., Imahori, T. and Tanaka, T. (2004) Substation Architecture with Protective Relays Using
Digital Instrument Transformers and Digital Interface Technol ogy . Developments in Power System Protection, 810-
813.
[9] Feng, J. (2011) Smart Subatation Principle and Testing Technique. China Electric Power Press, Beijing.
[10] Q/GDW 441-2010 (2012) Technical Specifications of Protection for Smart Substation. State Grid Corporation of China,
Beijing.
[11] Yue, C.Y., Tian, F., Zhou, X.X., et al. (2006) Principle of Interfaces for Hybrid Simulation of Power System Electro-
magnetic-Electromechanical Transient Process. Power System Technology, 30, 23-27.
[12] Dube, B., Varennes, Q., Lefebvre, S., Perocheau, A. and Nakra, H.L. (1988) Comparative Hybrid and Digital Simul a-
tion Studies of the Behaviour of a Wind Generator Equipped with a Static Frequency Converter. Electrical Engineer-
ing Journal, 39-44.
[13] Zhu, X.K., Zhou, X.X., Tian, F., et al. (2011) Hybrid Electromechanical-Electromagnetic Simulation to Transient
Process of Large-Scale Power Grid on the Basis of ADPSS. Power System Technology, 35, 26-31.
[14] Zhao, W.G. and Ren, X.Y. (2010) Time Synchronization with IRIG-B Code in Smart Electronic Devices. Automation
of Electric Power Systems, 34, 113-115.
[15] Shi, X.H., Gao, H.L., Xian g, M.J., et al. (2011) Application of IEEE1588 Time Synchronization Protocol in Digital
Substation. Electric Power Automation Equipment, 31, 132-135.