IEEE Grounding

7/30/2019 IEEE Grounding

1/9

IEEE TRANSACTIONS ON SMART GRID, VOL. 3, NO. 2, JUNE 2012 761

Online Monitoring of Substation Grounding GridConditions Using Touch and Step Voltage Sensors

Xun Long, Student Member, IEEE, Ming Dong, Student Member, IEEE, Wilsun Xu, Fellow, IEEE, andYun Wei Li, Member, IEEE

AbstractA grounding grid of a substation is essential for re-

ducing the ground potential rises inside and outside the substationduring a short-circuit event. The performance of a grounding gridis affected by a number of factors, such as the soil conductivityand grounding rod corrosion. Industry always has a strong desirefor a reliable and cost-effective method to monitor the condition

of a grounding grid to ensure personnel safety and prevent equip-

ments damage. In view of the increased adoption of telecom andsensor technologies in power industry through the smart grid ini-tiative, this paper proposes an online condition monitoring schemefor grounding grids. The scheme monitors touch and step voltages

in a substation through a sensor network. The voltages are createdby a continuously-injected, controllable test current. The results

are transmitted to a database through wireless telecommunication.The database evaluates the gridperformance continuously by com-paring the newly measured results with the historical data. Manyof the limitations of the offline measurement techniques are over-

come. Computer simulation studies have shown that the proposedscheme is highly feasible and technically attractive.

Index TermsOnline monitoring, step voltage, substationgrounding, thyristor, touch voltage.

I. INTRODUCTION

P ROPER grounding is thefirst line of defense against light-ning or other system contingency to ensure the safety ofoperators and power apparatus. A poor grounding system not

only results in unnecessary transient damages, but also causes

data and equipment loss, plant shutdown, as well as increases

fire and personnel risk. As a result, Utility companies are ac-

tively seeking techniques that can effectively and reliably eval-

uate the grounding grid conditions to ensure personnel safety

and prevent equipments damage.

The performance of grounding grid is affected by various fac-

tors such as unqualified jointing while building, electromotive

force of grounding current, soil erosion and theft of grounding

rods [1]. Thus, monitoring and diagnosing the conditions ofgrounding grid has been an active research field for many years.

However, almost all techniques implemented or proposed for

grounding monitoring are offline types where special instru-

ments are installed for grounding condition check on a regular

Manuscript received May 11, 2011; revised August 28, 2011; accepted Oc-tober 14, 2011. Date of publication February 13, 2012; date of current versionMay21, 2012. This work wassupported byiCORE. Paper no. TSG-00175-2011.

Theauthors are with theDepartment of Electricaland Computer Engineering,University of Alberta, Edmonton, AB T6G 2V4, Canada (e-mail: [email protected]; [email protected]; [email protected]; [email protected]).

Color versions of one or more of the figures in this paper are available onlineat http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/TSG.2011.2175456

or as-needed basis. These existing methods can generallybe cat-

egorized into two types: measurement of grounding impedance

and detection of grounding integrity.

Fall-of-Potential (FOP) method is the basic scheme for

grounding impedance measurement and it has been imple-

mented for many years [2]. Its key point is to correctly locate

the potential probe, which is quite time-consuming. A lot of

variations have been proposed to improve this scheme, such as

by using variable frequency source [3] or implementing mul-

tiple electrodes [4]. The methods taking account of current splitin transmission and distribution grounding system are further

developed in [5], [6] for accurately measuring the impedance

of in-service substations. However, the potential probes are still

indispensable in these FOP-based schemes. Several enhanced

grounding grid computer models are developed recently with

considering soil layer depth in [7], [8] or based on electro-

magnetic field methods [9], [10]. But, the accuracy of these

models relies on the soil resistivity measurement. Once the

soil condition is changed [11], potential electrode needs to be

relocated and it obviously increases the labor.

Monitoring the integrity of grounding grid is another way to

evaluate the performance of grounding grid [12], [13]. How-ever, the computation of this method depends on many uncer-

tain factors such as soil conductivity, humidity and climate [14].

A device based on measuring magnetic induction intensity is

designed to diagnose the grounding grid corrosion in [15]. It re-

quires the current injection between all possible grounding leads

on the ground surface to increase accuracy, which is not prac-

tical in a large scale substation.

All of the aforementioned methods are offline-based, which

at best give one-shot measurement results. If another set of

results is needed, the measurement system must be redeployed.

The offline-based methods have significant disadvantages.

Firstly, the results are largely dependent on the soil condition

at the time of measurement. Secondly, sudden changes of

the grounding grid such as those caused by theft cannot be

identified timely. To solve these problems, the methods that can

monitor the grounding condition on a continuous, i.e., online,

basis is highly desired.

This paper proposes an online substation touch and step

voltage monitoring scheme, which can continuously inject

testing current into a grounding grid and then measure the

corresponding touch and step voltages. The testing current is

created by a thyristor-based signal generator which is con-

nected between single energized phase conductor and ground

to stage a temporary and controllable fault. There is no extra

cable needed for current flow as power line is utilized as a path

1949-3053/$31.00 2012 IEEE


2/9

762 IEEE TRANSACTIONS ON SMART GRID, VOL. 3, NO. 2, JUNE 2012

Fig. 1. The process of the proposed online monitoring scheme.

for current injection. Touch and step voltages, which directly

reflect operational safety of substation, are used as indicators

of grounding condition. As the measurement of touch/step

voltages does not require long cables extending outside of a

substation [16], it is very suitable for long-term online moni-

toring. Supported by the historical data made available through

the online database which wirelessly communicate with the

voltage sensors, the variation of the measured data can be used

to infer the change of grounding grid conditions.

II. THE PROPOSED ONLINE MONITORING SCHEME

As shown in Fig. 1, the process of the proposed online mon-

itoring scheme includes a) testing current generation and in-

jection; b) touch voltage and step voltage measurement; and

c) safety assessment based on both data variation and actual

values. If the variation between the newly measured data and

historical data is below the preset threshold plus the measured

data does not exceed the safe value defined in the IEEE standard

[1], the grounding grid under test is considered to be in a good

condition and the next test will be made after a preset period.

Otherwise, a warning event will be created and then mandatory

inspections in the suspected spots with high touch voltage orstep voltage will be carried out.

A. Testing Current Generation and Injection

The signal generator for testing current generation consists

of a pair of thyristors connected to the supply via a single-

phase step-down transformer, which convert high voltage to low

voltage for the normal operation of the thyristors. When the

thyristors are fired under a preset firing angle, a testing current

will be injected into the system from the primary side of the

transformer [17]. The two thyristors are operated alternately to

create a sinusoidal waveform. To reliably measure the resulting

touch and step voltages, the duration of injected current cannotto be too short to establish stable potential profiles [18]. The

minimum time for tolerable touch or step voltage calculation is

30 ms according to [1]. On the other hand, the injected current

is required not to interrupt the normal operation of grounding

fault protection relay, in which the minimum trip time is about

100 ms [19]. In this work, the duration of current injection is

therefore setup as 50 ms, which is within the range between

30 ms to 100 ms. Not like grounding impedance measurement,

which needs square waveform to obtain various frequency com-

ponents to avoid the fundamental frequency interference from

power system or requires lightning waveforms to measure tran-

sient impedance, this paper focuses on safety evaluation at sub-

stations and the sinusoidal waveform is used to mimic a shot-cir-

cuit fault.

Fig. 2. The remote current injection scheme.

Fig. 3. The local current injection scheme.

This signal generator can be installed either remotely or lo-

cally. In the remote source scheme (see Fig. 2), the signal gen-

erator is installed at a downstream site far from the substation

to minimize the impact of the current injection to the ground

potential profile. As the ground can be utilized for current path

from the injected site to the substation grounding grid, the extra

current cable is not necessary [20].

In the local source scheme, the signal generator including a

step-down transformer is installed in the substation as shown

in Fig. 3. The current is directly injected from the substationand it returns from the remote power source. Since the device

is located in a substation, maintenance can be conveniently

achieved, which is important for long-term monitoring. How-

ever, a large transformer is needed as the signal generator has

to be installed at the high voltage side in a substation for the

local source scheme. This signal generator cannot be installed

at the grounded secondary side in a substation, since a current

loop is established by the grounded neutral and the test current

will not pass through the remote earth [21].

B. Touch/Step Voltage Based Sensor Network

The current injected into the grounding grid results in risesof touch voltage and step voltage, which directly indicate the

safety situation in and around the substation under test. Touch

voltage is defined as the potential difference between an exposed

metallicstructure within reach of a person and a pointwhere that

person is standing on the earth, while step voltage is defined

as the difference in potential between two points in the earth

spaced 1 meter (or a step) apart [22]. The measurement of touch

and step voltages can be easily conducted at many points of in-

terest in a substation, which is very suitable for long-term online

monitoring. Moreover, the interference with potential electrode

and long cable installation when conducting impedance mea-

surement is also eliminated.

We further proposed to use a wireless sensor network for

touch and step voltages monitoring (see Fig. 4). Typically, a


3/9

LONG et al.: ONLINE MONITORING OF SUBSTATION GROUNDING GRID CONDITIONS USING TOUCH AND STEP VOLTAGE SENSORS 763

Fig. 4. The sensors network of touch/step voltages measurement.

Fig. 5. (a) The voltage measurement (1-step voltage, 2-touch voltage). (b) Thestructure of the voltage sensor.

grounding grid is buried 0.5 m1 m under ground, which re-

sults in potential difference at the surface of ground. The touch/

step voltage sensors are distributed at corners of a grounding

grid and some other frequently visited spots with special con-

cern of human safety. All of these sensors can transmit signals

wirelessly to a computer which could be located indoors. The

computer is responsible to collect, classify and update the data

recorded in the database.

According to the IEEE Standard 81.2 [22], the simulated-

personnel method is recommended for touch and step voltages

measurement. This method utilizes a resistor with 1000 re-

sistance represents human body resistance and is connected be-

tween two feet. Each foot is made by a metallic plate with

200 cm surface area and 20 kg weight. A voltage meter is in-

stalled across the resistor with high internal impedance so as not

to influence the measurements. A device is designed to measure

either touch voltage or step voltage as seen in Fig. 5. Note that,

the distance between two feet is adjustable, which is 0.5 m

for measurement and 1 m for measurement, respec-

tively. Moreover, an extra probe is used to contact the exposed

conductive surface for touch voltage measurement.

It uses a voltage transducer to measure the voltage across ,

and then the measured value is converted to thedigital format byan ADC module. A MCU processes the data and the results are

finally transmitted to a central computer through a RF module.

In the project, Zigbee 2.4 GHz wireless signal transmission is

recommended and its range can be reach up to 300 ft, which

is adequate for a small or medium size distribution substation.

Moreover, it can be easily configured to handle wireless sensor

networking application at a low cost.

From the Thevenin equivalent circuit of the touch/step

voltage measurement as shown in Fig. 6, it is found that the

measured or is not the same as the potential difference on

the ground, and the touch or step voltage can be expressed as

(1)

Fig. 6. The Thevenin equivalent circuits of: (a) touch voltage measurement;(b) step voltage measurement.

(2)

where is the potential difference between the feet and the

touch point, is the touch voltage, is the foot resistance

when two feet are in parallel, is the human body resistance

(1 k ), is the potential difference between two feet, is

the step voltage, is the foot resistance when two feet are in

series.

However, the metallic plates installed on the surface of the

ground are likely to be corroded due to humidity or other fac-tors, which results in the increase of their resistance accordingly.

Equation (1) and (2) indicate that the measured voltage ( or

) decreases with the increase of the feet resistance ( or

) under the same potential difference ( or ). In this

case, the measured touch/step voltage will be lower than the

normal value and it may mislead the assessment.

To eliminate the effects of the feet resistance variation, the

voltages are measured twice, one in a close circuit during one

signaling period and the other in an open circuit during the next

signaling period. As the switching is operated after current in-

jection, it would not cause arcing and it also has no require-

ment on the switching speed. As shown in Fig. 6, an electrical

contactor is utilized for the switching purpose. Apparently, the

voltage or in an open circuit is equal to the potential

difference or . Resolve (1) and (2), the resistance of

or can be obtained.

(3)

(4)

If the variation between the estimated (or ) and its

nominal value is larger than a predetermined value, the mea-

sured (or ) cannot bedirectly used. Inthis case, the metallic

feet need to be replaced by a new pair of plates. Alternatively,

these voltages ( and ) can be adjusted according to the fol-

lowing equations:

(5)

(6)

where is the nominal value of is the nominal

value of .

From the study of the potential profile of a substation, it

is found that there are several suspected spots in or around a

substation, particularly in a substations corners or around the

fences. Therefore, before installing the measurement tools, it


4/9


is necessary to inspect those suspected points. One solution

is pretest. A workman walks across a substation with the test

device to record the locations where the measured voltages

exceed the preset threshold. Further measurements can then

be made by online monitoring in the suspected locations, thus

reducing the time and cost of measurements. Another solution

is to find the suspected spots in the potential profile from

a computer simulation results. In this case, the accuracy of

locating the danger points highly depends on the accuracy of

the simulation model.

According to [1], the limit of touch/step voltage is a function

of a) shock duration (i.e., fault clearing time); b) system charac-

teristics; c) body weight; and d) foot contact resistance as shown

in (7) and (8). The constant is 0.116 for a person with 50 kg

body weight, while it is 0.157 for 70 kg.

(7)

(8)

Since the injected current is much smaller than the maximum

fault current, the measured touch/step voltage is therefore much

lower than the limits defined in (7) and (8). Thus, the original

measured data is intentionally increased to maximum value by

(9) and (10) when the data transfer to the database. The decision

is then made by the comparison of the measured data with his-

torical data or with the maximum tolerable values provided by

(7) and (8).

(9)

(10)

For personnel safety evaluation, touch voltage is more se-

vere than step voltage [23]. The current caused by touching

an exposed conductorflows through the heart, whereas the one

caused by step voltage bypass the heart. Therefore, the tolerate

touch voltage is much lower than tolerate step voltage. Gener-

ally, satisfying the touch voltage safety criteria in a substation

automatically ensures the satisfaction of the step voltages safety

criteria. In this project, most areas in the substation are exam-

ined for touch voltage, and only the edges of the grid are exam-

ined for step voltage.

C. Intelligent Evaluation Techniques With Database

Another novel feature of the proposed scheme is the imple-

mentation of online database. It is known that the resistivity of

the surface soil layer would be changed in different seasons,

which may results in touch/step voltages moving to the hazard

side [14]. For example, if the thickness of the low-resistivity

soil layer in raining season is smaller than the buried depth of

the grounding grid, the touch voltage increase. In another case,

the high resistivity soil layer formed in freezing season would

cause the increase of the touch/step voltage with the thickness or

resistivity of the freezing soil layer. One major defect of the ex-

isting offline monitoring method is the inability of tracking sea-

sonal influences on the safety of substation grounding system.

With the support of database, we can continuously monitor and

record the change of touch/step voltage. Particularly, during the

severe conditions, like continuous raining or freezing seasons,

the frequency of online monitoring can be increased in order to

find the potential hazards in time.

Corrosion, which can damage the effective connections

among the conductors, is another factor affecting the safety of

the grounding system. The grounding grid corrosion is caused

by acid or alkali in soil and the corrosion rate can reach up to 8.0

mm per year according to statistic results [24]. This situation

becomes more serious as the steel-grounding or galvanized

steel-grounding system is widely used, which is more easily

corroded than copper so that it requires more accurate, timely

assessment of grounding grid.

While the corrosion of grounding grids may be detected by

regular off-line measurements as it is a slow process, the theft of

grounding rods, another major concern to utility companies, can

suddenly change the integrity of the grounding grid. Failing to

detect this change in a timely manner will cause serious conse-

quences. In the proposed online monitoring scheme, the change

of touch and step voltages at the same point are recorded, sothat synthesized and reliable estimation can be made not only

depending on the IEEE standard but also on the variation due to

seasonal influence, corrosion or theft.

Based on the above analysis, an intelligent evaluation (see

Fig. 7) can be made as follows:

1) Generate and inject a testing current into a grounding grid

periodically. Measure the resulting touch/step voltages

with the sensor network and transfer the data to the central

database.

2) Scale the measured touch/step voltages to the maximum

touch/step voltages.

3) Compare the maximum touch/step voltages with IEEEstandard under the same parameters, like fault clearing

time and the body weight, etc. If it exceeds the safe value,

a warning event is created and the suspected location is

reported to substation operators for further analysis.

4) Compare the measured touch/step voltages with the his-

torical data at the same location. If the variation is larger

than the preset threshold, a warning event is created even

though the actual value does not exceed the standard. A

mandatory examination will be taken around the suspected

point to check if the conductors are stolen or broken due to

corrosion.

5) If no suspected spot is found, the database is updated with

the new measured data and meteorological parameter, such

as temperature and humility. Then, after a preset period, go

back to 1).

III. STUDY OF CURRENT DISTRIBUTION

A simulation model is built in PSCAD to study current dis-

tribution of both remote and local injection schemes as shown

in Fig. 8. The distribution substation under test transfers power

from 125 kV to 25 kV via a Delta-Yg connection transformer.

An overhead ground wire, so called skywire, accompanies with

transmission lines and the ground resistance of a transmission

line tower is 32 . At the secondary side, the neutral line of

distribution system is multiple-grounded with 15 at each


5/9


Fig. 7. The evaluation process with database.

Fig. 8. Computer simulation for current distribution study.

Fig. 9. The structures of transmission line tower and distribution line pole.

TABLE IPARAMETERS OF COMPUTER SIMULATION FOR CURRENT DISTRIBUTION STUDY

grounded connection. The structure details of the transmission

line tower and the distribution line pole are illustrated in Fig. 9.Other parameters are listed in Table I.

In the remote injection scheme, a temporary fault is staged at

downstream of the under-test substation to create a fault current

flowing from the faulted phase to ground and back to the sub-

station. However, with the presence of the multiple grounded

points on the neutral, such as pole grounds and transformer

grounds, the current is divided before reaching the substation

grounding grid. As shown in Fig. 10, the current division of the

remote injection scheme depends on the distance between the

location of the staged fault and the substation. When the staged

fault is located 5 km away from the tested substation, only 37%

current flows back through substation grounding grid.

The local injection scheme requires a pair of thyristors

connected between a single phase of transmission line and the

Fig. 10. Current distribution of the remote scheme with respect to distancefrom subtation.

Fig. 11. Current waveforms of current distribution study.

grounding grid by a step-down transformer. Because of theexistence of overhead ground wires and neutral lines, not all

fault current flow through the grounding grid to the remote

earth [21]. The simulation results (see Table II) show that

73.58% current across the grounding grid, 26.70% current

in the skywire and 10.59% current in the neutral

line. Disconnecting the skywire and the neutral line can largely

increase the grounding grid current. However, it is impossible

to disconnect these ground wires for long time monitoring in

reality. From touch voltage simulation which will be discussed

later, 60 A grounding grid current can result in about 3 V13

V touch voltage, which is large enough for effective detection.

The current waveforms for the local injection scheme areshown in Fig. 11. Typically, there are relays implemented in the

substation for ground fault protection. These protective relays

have an inverse current/time characteristic, which suggests they

can tolerate high current with a short duration. As the duration

of the injected 60 A current is about 50ms, shorter than 0.1 s, it

does not interrupt the normal operation of the protective relays

[19].

The proposed local scheme is also applicable to the substa-

tions with Yg-Yg or Y-Yg connection. As shown in Fig. 12,

both the primary side and secondary side of the transformer

are Yg connection and the neutral points are connected in the

grounding grid. A staged fault is created at the primary side

when the thyristors are turned on for 50 ms. The computer sim-

ulation results are listed in Table III. If all the grounded wires


6/9


TABLE IICURRENT DISTRIBUTION OF THE LOCAL SCHEME WITH A DELTA-YG

CONNECTION TRANSFORMER

Fig. 12. Current distribution study of Yg-Yg connection substation.

TABLE IIICURRENT DISTRIBUTION OF YG-YG AND Y-YG CONNECTION

are connected, the current ratio of is 81.9% for Yg-Yg

connection and it is 76.8% for Y-Yg connection.

IV. COMPUTER SIMULATION OF THE PROPOSED ONLINE

MONITORING

SCHEME

Computer simulations have also been conducted in

CYMGRD [25] to measure touch/step voltages, illustrate

the process of intelligent evaluation scheme and analyze the in-

fluence of seasons, corrosion and theft. The designed grounding

grid as shown in Fig. 13 is 150 m long and 100 m wide. All con-

ductors are buried at a depth of 0.5 m. X-axis has 8 conductors

and Y-axis has 10 conductors. The diameter of all conductors

is 19.1 mm. Plus, 30 grounding rods are vertically connected to

the grounding grid. Each rod is 5 m long with diameter 2.858

cm. Moreover, the station surface is with crushed rock of 2500

ohm-meter resistivity at a thickness of 0.3 m and the exposure

duration is 0.36 s with 4000 A fault current.To begin touch/step voltages simulation, we firstly interpret

the soil resistivity measurements and obtain a soil model for the

subsequent analysis. A two-layer soil model is implemented in

this simulation. From the data provided by IEEE standard (see

Table IV), both the upper and lower layers resistivity can be cal-

culated and the depth of the upper layer can be estimated as well.

The result of soil model calculation is consistent with the IEEE

calculated values (see Table V), which proves the validity of

the designed two-layer soil model. Furthermore, the maximum

permissible touch and step voltages in accordance with the sub-

station surface and the shock time can be calculated by (7) and

(8), which is 1084.2 V and 3551.8 V respectively.

The potential profile of the grounding grid diagonal line is

shown in Fig. 14. Apparently, touch voltage at the corner is

Fig. 13. The designed grounding grid in the computer simulation.

TABLE IVTHE SOIL RESISTIVITY MEASUREMENTS DATA WITH THE FOUR-PIN METHOD

PROVIDED BY IEEE STANDARD

TABLE VCOMPARISON OF THE SIMULATION RESULTS AND IEEE VALUES

much larger than in the middle center. It is due to less conduc-

tors buried around corners than around center. The suspected

points can be clearly located from this potential profile, which

is very useful for installation of the voltage sensors. This pro-

file also confirms that the value of maximum permitted touch

potential has a dominant role in determining the design of the

grounding grid. If a grid satisfies the requirements for safe touch

potentials, it is very unlikely that the maximum permitted step

potential will be exceeded. In Fig. 14, the margin between thecalculated touch voltage and the permissible touch voltage is

about 200 V800 V, while this margin for step voltage is as large

as 3500 V.

As the injected current through the grounding grid is actually

about 50100 A, the concern here is if the 50100 A current

is able to result in detectable touch/step voltage. The profile in

Fig. 15 is obtained with 60 A grounding grid current, which

causes the touch voltage between 313 V. The voltage in this

range can be easily detected by the voltage sensors. For safety

evaluation, the actual voltages are scaled up to the maximum

values in the database according to (9) and (10).

With the support of database, synthesized and reliable es-

timation can be made depending on IEEE standard constraint

and recorded data variation. To better clarify the concept of the


7/9


8/9


Fig. 19. Three suspect spots are picked up from the diagonal line.

Fig. 20. Touch voltage of three suspect spots in different seasons.

for 50 ms. The current can be injected remotely or locally.

The local injection scheme has a larger portion of the injected

current flowing through the grounding grid, but it costs more

than the remote scheme due to high rating voltage and high

capacity of the step-down transformer.

The condition monitoring is achieved with a wireless

touch/step voltage sensors network installed at various lo-

cations of a substation. These sensors are connected to a

central database where an evaluation process is carried out by

comparing the newly measured data to the limits from IEEE

standard, or checking if the data variation at the same spot

exceeds safety thresholds. Furthermore, current distributionhas been studied with computer simulations, which verified the

effectiveness of the proposed local and remote schemes. From

the case studies of conductor theft and seasonal influences, the

advantage of online monitoring is very clear since some danger

spots cannot be found in time without continuous measurement.

With further research, the proposed scheme could be used to

locate broken section or missing grounding electrode based

on the step/touch voltage profile obtained from the sensors.

Compared to offline methods, which at best gives one-shot

assessment, the proposed online grounding grid monitoring

scheme is more effective and reliable, and it could become an

important component of a smart substation.

The paper has presented an overall concept of the proposed

monitoring scheme. A lot more research works are still needed.

For example, the proposed scheme is focused on touch and step

voltage indices which are related to personnel safety concerns.

Since grounding design has other objectives such as facilitating

equipment protection, the proposed scheme needs to be further

expanded to include sensors and indices that address equipment

protection concerns. It is possible that acceptable touch and step

voltages at sufficient locations in a substation may imply an ac-

ceptable grounding condition from equipment protection per-

spectives. But research is needed to verify this postulation.

The proposed scheme involves a sensor network and its data

collections. There are many challenges to build and maintain

such networks. The reliability of the network needs to be

confirmed as well. These are exactly the subjects of interest

to ICT- (information and communication technology) oriented

smart grid researchers.

REFERENCES

[1] IEEE Guide for Safety in AC Substation Grounding, IEEE Std.

80-2000, 2000.[2] IEEE Guide for Measuring Earth Resistivity, Ground Impedance, and

Earth Surface Potentials of a Ground System, IEEE Std. 81-1983,1983.

[3] I. Lu and R. Shier, Application of a digital signal analyzer to the mea-surement of power system ground impedances, IEEE Trans. Power

App. Syst., vol. PAS-100, no. 4, pp. 19181922, Apr. 1981.[4] A. Meliopoulos, G. Cokkinides, H. Abdallah, S. Duong, and S. Patel,

A PC based ground impedance measurement instrument, IEEETrans. Power Del., vol. 8, no. 3, pp. 10951106, Jul. 1993.

[5] J. Choi, Y. Ahn, H. Ryu, G. Jung, B. Han, and K. Kim, A newmethod of grounding performance evaluation of multigrounded powersystems by ground current measurement, in Proc. Int. Conf. PowerSyst. Technol., Nov. 2004, vol. 2, pp. 11441146.

[6] L. S. Devarakonda, J. Moskos, and A. Wood, Evaluation of groundgrid resistance for inservice substations, in Proc. 2010 IEEE Power

Eng. Soc. Transm. Distrib . C onf., Apr. 2010, pp. 14.[7] C. Chang and C. Lee, Computation of ground resistances and as-sessment of ground grid safety at 161/23.9-kv indoor-type substation,

IEEE Trans. Power Del., vol. 21, no. 3, pp. 12501260, Jul. 2006.[8] A. Puttarach, N. Chakpitak, T. Kasirawat, and C. Pongsriwat, Sub-

station grounding grid analysis with the variation of soil layer depthmethod, in Proc. IEEE Power Tech. Conf., Jul. 2007, pp. 18811886.

[9] L. Qi, X. Cui, Z. Zhao, and H. Li, Grounding performance analysis ofthe substation grounding grids by finite element method in frequencydomain,IEEE Trans. Magn., vol. 43,no. 4, pp. 11811184,Apr. 2007.

[10] J. Ma and F. Dawalibi, Analysis of grounding systems in soils withfinite volumes of different resistivities, IEEE Trans. Power Del., vol.17, no. 2, pp. 596602, Apr. 2002.

[11] R. Gustafson, R. Pursley, and V. Albertson, Seasonal grounding re-sistance variations on distribution systems, IEEE Trans. Power Del.,vol. 5, no. 2, pp. 10131018, Apr. 1990.

[12] B. Zhang, Z. Zhao, X. Cui, and L. Li, Diagnosis of breaks in sub-

stations grounding grid by using the electromagnetic method, IEEETrans. Magn., vol. 38, no. 2, pp. 473476, Mar. 2002.

[13] J. Hu, R. Zeng, J. He, W. Sun, J. Yao, and Q. Su, Novel method ofcorrosion diagnosis for groundinggrid, inProc. 2000 Int. Conf. PowerSyst. Technol., pp. 13651370.

[14] J. He, R. Zeng, Y. Gao, Y. Tu, W. Sun, J. Zou, and Z. Guan, Seasonalinfluences on safety of substation grounding system, IEEE Trans.

Power Del., vol. 18, no. 3, pp. 788795, Jul. 2003.[15] Y. Liu, X. Cui, and Z. Zhao, May 2010, A magnetic detecting and

evaluation method of substations grounding grids with break andcorrosion, [Online]. Available: http://www.springerlink.com/con-tent/f71631x2733n7158/fulltext.pdf

[16] A. P. S. Meliopoulos, S. Patel, and G. J. Cokkinides, A new methodand instrument for touch and step voltage measurements, IEEE Trans.

Power Del., vol. 9, no. 4, pp. 18501860, Oct. 1994.[17] W. Xu, G. Zhang, C. Li, W. Wang, G. Wang, and J. Kliber, A

power line signaling based technique for anti-islanding protection ofdistributed generatorsPart I: Scheme and analysis, IEEE Trans.

Power Del., vol. 22, no. 3, pp. 17581766, Jul. 2007.


9/9


[18] R. Verma and D. Mukhedkar, Fundamental considerations and im-pulse impedance of grounding grids, IEEE Trans. Power App. Syst.,vol. PAS-100, no. 3, pp. 10231030, Mar. 1981.

[19] P. Rush, Network Protection & Automation Guide, ALSTOM T&DEnergy Automation & Information 2002.

[20] J. Sarmiento, H. G. Fortin, and D. Mukhedkar, Substation groundimpedance: Comparative field measurements with high and low cur-rent injection methods, IEEE Trans. Power App. Syst., vol. PAS-103,no. 7, pp. 16771683, Jul. 1984.

[21] S. Patel, A complete field analysis of substation ground grid by ap-plying continuous low voltage fault, IEEE Trans. Power App. Syst.,vol. PAS-104, no. 8, pp. 22382243, Aug. 1985.

[22] IEEE Guide to Measurement of Impedance and Safety Characteristicsof Large, Extended or Interconnected Grounding Systems, IEEE Std.81.2, 1992.

[23] R. Kosztaluk, R. Mukhedkar, and Y. Gervais, Field measurements oftouch and step voltages, IEEE Trans. Power App. Syst., vol. PAS-103,no. 11, pp. 32863294, Nov. 1984.

[24] P. Sen and N. Mudarres, Corrosion and steel grounding, in Proc.1990 22nd Annu. North Amer. Power Symp., pp. 162170.

[25] Cooper, Dec. 2009, CYMGRDSubstation Grounding Program[Online]. Available: http://www.cyme.com/software/cymgrd/B1100-09079-CYMGRD.pdf

Xun Long (S08) received the B.E. and M.Sc degrees in electrical engineering

from Tsinghua University, Beijing, China, in 2004 and 2007, respectively, andis currently working toward the Ph.D. degree in the Electrical and ComputerEngineering Department, University of Alberta, Edmonton, Canada.

His main research interests include power line signaling, distributed genera-tion and fault detection.

Ming Dong (S08) received the B.Eng. degree in electrical engineering fromXian Jiaotong University, China, in 2004. He is currently working toward thePh.D. degree in electrical and computer engineering with the University of Al-berta, Edmonton, Canada.

His research covers smart grid, grounding systems, and power quaility.

Wilsun Xu (F05) received the Ph.D. degree from the University of British Co-lumbia, Vancouver, Canada, in 1989.From 1989 to 1996, he wasan Electrical Engineer with BC Hydro, Vancouver

and Surrey, respectively. Currently, he is with the Department of Electrical andComputer Engineering, University of Alberta, Edmonton, Canada, where he hasbeen since 1996. His research interests are power quality and distributed gener-ation.

Yun Wei Li (S04M05) received the B.Sc. degree inengineering from TianjinUniversity, China, in 2002 and the Ph.D. degree from Nanyang TechnologicalUniversity, Singapore, in 2006.

In 2005, he was a Visiting Scholar with the Institute of Energy Technology,Aalborg University, Denmark. From 2006 to 2007, he was a Postdoctoral Re-search Fellow in the Department of Electrical and Computer Engineering, Ry-

erson University, Canada. After working with Rockwell Automation Canada in2007, he joined the Department of Electrical and Computer Engineering, Uni-versity of Alberta, Edmonton, Canada, as an Assistant Professor. His researchinterests include distributed generation, microgrid, power converters, and elec-tric motor drives.

IEEE Grounding

Documents

Transcript of IEEE Grounding