Standardisation Challenges for Digital Inputs and Outputs of Protection Functions in IEC 60255 series

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Conference: PAC World - June 2019, At Glasgow UK
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Abstract
The fast deployment of Fully Digital, process bus based, substation Protection, Automation and Control Systems (FD-PACS) gives raise to protection functions interfaced with digital secondary systems. The current IEC 60255 series standards, covering protections, need to take into account this evolution. The paper discusses the requirements and associated tests which need to be considered in this context and describes the findings and recommendations of IEC TC 95 AhWG3, which has been missioned to investigate this subject.
PAC World June 17-20 2019 Glasgow, UK - Paper PW02 - page 1
Standardisation Challenges for Digital Inputs and Outputs of Protection
Functions in IEC 60255 series
Volker LEITLOFF *), Hao CHEN, Dehui CHEN, Andrea BONETTI, Lei XU, Ahmed MOHAMED
Rte (FR), State Grid Jiangsu Electric Power Co., Ltd (CN), SGEPRI (CN), Megger Sweden AB (SE),
NR Electric (CN), SSE (UK) on behalf of IEC TC95 AhWG3
*) volker.leitloff@rte-france.com
Summary
The fast deployment of Fully Digital, process bus based, substation Protection, Automation and Control
Systems (FD-PACS) gives raise to protection functions interfaced with digital secondary systems. The
current IEC 60255 series standards, covering protections, need to take into account this evolution. The
paper discusses the requirements and associated tests which need to be considered in this context and
describes the findings and recommendations of IEC TC 95 AhWG3, which has been missioned to
investigate this subject.
Keywords
Standardisation, IEC 61850 process bus, IEC 60255, IEC 61869, interoperability, protection functions
1. Introduction
Fully Digital Substations using IEC 61850 process bus are being introduced all over the world.
Numerous utilities feature Pilot Projects, Demonstrators [11], [12] or even industrial scale deployment
of these Fully Digital substation Protection, Automation and Control Systems (FD-PACS).
Concerning applicable product standards, profiles for Instrument Transformers have been developed
and published by IEC TC 38 (Instrument Transformers), in particular:
IEC 61869-6 Additional general requirements for low-power instrument transformers [1]
IEC 61869-9 Digital interface for instrument transformers [2]
IEC 61869-13 covering Stand Alone Merging Units is in CDV stage [3] and is expected to be published
as International Standard (IS), in 2020.
This raises the question about product standards for protection functions interfaced with digital
secondary systems. In 2016, IEC TC 95 (Measuring relays and protection equipment) missioned
AhWG3 to investigate this subject and to elaborate recommendations concerning requirements and
testing of protection IED with digital inputs and outputs for protection standards covered by TC 95. This
concerns IEC 60255 standard, mainly the documents dedicated to the functional part, known as IEC
60255-1xx series.
For protection functions, published or subscribed data streams are supposed to comply with IEC 61850
and IEC 61869 standards. This holds in particular for Sampled Values (SV) representing energising
inputs of the protection function, and is also applicable to Generic Object Oriented Substation Event
(GOOSE) which can be used for input (for example signals indicating circuit breaker position or circuit
breaker failure) or output of protection functions (for example trip orders). The value of the data quality
attribute of published data depends on value of DO, health, on the connection status of the function and
on the hardware status of the hosting IED.
In addition to this, protection functions should take into account the time synchronisation status of the
received Sampled Values. They also may themselves need to be time synchronised, for example if the
protection device is working with conventional analog quantities and SV quantities at the same time, or
if supervision functions on the correct synchronisation of the sampled values are implemented in the
subscribing protection IED.
PAC World June 17-20 2019 Glasgow, UK - Paper PW02 - page 2
Figure 1 shows the functional chain of protection functions interfaced with a digital secondary system,
highlighting the different applicable product standards. Although several configurations are possible to
interface Instrument Transformers, the characteristics of their digital interface are described by IEC
61869-6 and IEC 61869-9 which is common to both
Stand Alone Merging Units (SAMU) connected to Convectional Instrument Transformers,
Merging Units associated to Low Power Instrument Transformers (LPIT).
Figure 1 - Functional chain of protection functions interfaced with digital secondary system
Regarding the fault clearance time, the acquisition time of the Merging Units and the transmission time
of SV and GOOSE have to be taken into account in addition to the time required for the protection
algorithm itself and the time for closing the trip contacts (Figure 2). With respect to a conventional PACS
with hardwired protection IED, this changes the definition, test and responsibilities for the fault clearing
time in a significant way.
Sensor
Transmitter
Merging Unit
Transmitter
Receiver
t
ps
Data
Processing
t
mu
Sensing
processing
Communication
network
t
st1
Receiver
Transmitter
t
p1
Receiver
t
sc1
IED
Protection
Data
Caching
Logic
SCU
Data
Processing
Trip
Relay
Transmitter
Receiver
t
p2
GOOSE
t
sc2
SVGOOSE
SV/GOOSE
t
p
t
tt
t
sc
scsc
sc
t
st2
Receiver
Transmitter
GOOSE
t
d
Communication
network
Figure 2 - Operate Time of the functional chain of a protection function (example: LPIT)
2. Considerations for Protection Functions interfaced with Digital Input / Output
An analysis of the functional chain of protection functions shows that the following elements also have
to be considered [7] (cf. Figure 1):
The characteristics, transfer function including anti-aliasing filter and accuracy of the analog
data (current / voltage) contained in the SV stream is covered by the IEC 61869 series (cf.
Figure 4).
The overall performance of a functional protection chain depends on the design and on the
characteristics of the protection itself and of the communication network. Even if partially
covered by IEC 61850 standards and guidelines or best practices, no general statements over
performance of the communication network can be given. A new or extended responsibility of
the user and/or integrator for the correct design of the protection schemes has thus to be
acknowledged. Probably, in the near future, the system integrators will be requested to provide
PAC World June 17-20 2019 Glasgow, UK - Paper PW02 - page 3
an engineering document addressing the communication network performances (latency, worst
case analysis, reliability).
The expected behaviour of the protection function, if subscribed data or time synchronisation
is in a non-nominal state or lost, has to be specified to avoid misunderstandings and minimise
tests at commissioning. The corresponding tests have to be defined.
No IEC standard covers, at this moment, the requirements for Binary input / output IED used
for interfacing binary inputs and outputs. This device can be used to interface circuit breakers,
disconnectors or other binary inputs (monitoring of auxiliary power supply contacts, etc). These
devices form part of the functional protection chain when interfaced with a conventional circuit
breaker.
Protection function requirements on Current Transformers (CT), which are mandatory in IEC
60255-1xx relay protection standards, need to be adapted and translated in requirements for
Merging Units.
On this base, the recommendations given by AhWG3 [7] can be separated in 2 types:
Recommendations for taking digital I/O into account in IEC 60255 series.
Recommendations for clarifications or amendments in IEC 61869 and IEC 61850 standards.
Performance characteristics have to be defined or adapted for protection functions with digital inputs
and outputs in the relevant functional standards (IEC 60255-1xx series). In principle, all tests of the IEC
60255-1xx series using ideal Instrument Transformers can be performed in a similar way and with the
same network model by injection of Sampled Values. This concerns:
Operate time: The operate time is defined as time between fault inception and relay operation.
For digitally interfaced protections, this corresponds to the instant the SV corresponding to the
fault inception is received by the device hosting the protection function and the moment it
publishes the trip GOOSE message.
Reset time,
Rest ratio,
Stability test,
Steady state accuracy tests (thresholds).
Figure 3 – Example of standardized CT Requirements in today’s IEC 60255-121
There is a subtle difference between tests with ideal CTs (and/or VTs) for conventional technology and
test with direct primary quantities in Sampled Value streams for IEC 61850 technology: the first tests do
include the performances of the analog input module and internal A/D conversion. The second tests do
not include this because this part has been moved to the Merging Unit. The difference can be quite
important, especially for protection functions that elaborate an instantaneous trip decision. This
characteristic has a direct relation with the transient performances of the merging units. The transient
performances of the analog input module and internal A/D conversion are already considered in the
protection relay algorithms.
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For these reasons, the part dedicated to the so called “merging unit requirements” will be a very
important part for the IEC 60255-1xx series, where guidelines will be given in order to have the definition
of the performances expressed in a standardized way, as it is today done for CTs (Figure 3), [10]. This
still needs to be discussed within TC 95.
In order to determine the current transformer requirements for a particular protection function, the IED
manufacturers need today to perform tests were the Instrument Transformers are not ideal. At the same
time, in order to be able to determine the MU requirements, it is necessary to implement models taking
into account the characteristics of the Merging Units in the power system network simulator publishing
the SV streams used for the test (cf. §3.1) [10], [13].
3. Requirements regarding subscribed Sampled Value Streams
3.1 Accuracy of the protection function
The accuracy declaration which can be found in IEC 60255-1xx series for protection IED with analog
inputs covers the complete functional chain, including
input analog module in the protection device,
the A/D conversion,
the protection function itself.
The accuracy declaration for a protection function subscribing to a Sampled Value stream will cover the
protection function itself, when responding to the standardized numerical SV stream(s). In order to
indicate the total accuracy, it is necessary to consider requirements on the accuracy class of the SAMU
or LPIT. In case of the SAMU, the accuracy class of the associated conventional Instrument
Transformers needs to be considered by the user as well, as this is already the case in protection IED
with analog inputs. A correspondence table will be provided in IEC 61869-13 [3].
In addition to accuracy requirements, the digitally interfaced protection function is supposed to verify
elements that are not available in conventional technology, but that, if well implemented, will contribute
to improve the dependability and also security of the protection system. This also enables automatic
substation supervision functionalities, allowing event driven maintenance of the substation with reduced
costs for routine maintenance tests. These elements include:
The synchronisation status of the incoming SV. Depending on the protection function, it may
be necessary to suspend the operation of the function if the SV is not globally or locally
synchronised. This is in particular the case for protection functions subscribing to SV streams
from more than one Merging Unit.
The quality data attribute (DA) and the detailed quality of the received SV. The expected
behaviour of the protection function in case of non-nominal values of these attributes needs to
be specified. It can depend on the nature of the protection function. For example, clipping may
be tolerable for overcurrent functions but may lead to a suspension (blocking) of the operation
of a differential protection function, similar to what is done today when the communication is
lost in line differential protection applications.
Regarding the analog acquisition chain, it has to be verified that the protection function is compatible
with
the protocol profile of the SV stream (IEC 61869-9 or legacy 9-2LE profile). Legacy 9-2LE
guideline is available in positions 1 and position 2 of Table 1.
the transfer function of the Merging Unit publishing the SV stream according to IEC 61869-
9:2016 [1] (cf. Figure 4).
In case of SAMU
o the saturation characteristics of the CT of the conventional current transforms.
o the time constant and transient behaviour of the SAMU, covering in particular its current
input circuit [13].
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As mentioned before (§2), for these characteristics (saturation, remanence, flux) a similar approach
as in IEC 60255-1xx series can be taken. In this case, the manufacturer indicates the required
characteristics for the upstream analog acquisition chain for if the protection function.
Figure 4 - Example of a MU transfer function for metering accuracy class 1(fr = 60 Hz, fs = 4 800 Hz)
according to IEC 61869-6:2016 [1] Copyright © 2016 IEC Geneva, Switzerland. www.iec.ch
Table 1 -
Sampled values protocol profiles according to IEC 61869-9:2016 Table 901
Copyright © 2016 IEC Geneva, Switzerland. www.iec.ch
PAC World June 17-20 2019 Glasgow, UK - Paper PW02 - page 6
3.2 Missed samples, time synchronisation, network latency and jitter
Based on requirements of IEC 61869-9, a jump of SmpCnt is possible if it is related to a
resynchronisation. This has to be taken into account by the input processing of SV of the protection
functions. For all protection functions in one IED or for each individual protection function, it has also to
be stated how many consecutive missing or invalid samples are acceptable. When this number is
reached, the operation of this protection function shall be suspended and publish its DO with invalid
quality attribute.
The standard of IEC61869-9 clause 6.902.2 [2] gives the maximum processing delay time limits of MU
for publishing the sampled data. For protection applications, this time delay is 2ms. The delay of the
PACS communication network has to be considered for the maximum time delay of the SV seen by the
input port of the protection function (cf. Figure 2).
The average transmission time delay (latency) and jitter caused by the communication network has to
be taken into account. These values can be obtained by communication network system studies (cf.
§2). For protection functions subscribing to one SV stream, the time delay has no impact other than a
shift of the processing time. It has, however, an impact on the total trip time. The size of the input
alignment table (input buffer) of the protection function is determined by the expected jitter.
For protection functions subscribing to more than one SV stream, the maximum relative time delay
between the SV streams also defines the size of its input alignment table (Figure 5). The worst case
would be a negligible time delay for the connection to one Merging Unit and a huge transmission time
delay for the connection to another Merging Unit.
Figure 5 - Operation of SV input buffer of a protection function
3.3 Meaning of SV values with non-nominal quality attributes
The interpretation given in IEC 61869-9 [2] for the detailed quality attribute is to be applied for protection
functions. Table 2 lists the DetailQual attributes as defined in IEC 61850-7-3, the corresponding
requirements for Sampled Values published by MU according to IEC 61869-9 and the recommended
application for protection functions.
PAC World June 17-20 2019 Glasgow, UK - Paper PW02 - page 7
Based on Table 2, the value range of analog energizing quantities subscribed by protection functions
and the associated detailed quality attributes are visualised in Figure 6. An analog value above the limit
of rated accuracy is thus published as “Questionable”. This holds also for the case when the analog
acquisition circuit is saturated and signal clipping occurs.
Table 2 – Interpretation of Detailed Quality for Sampled Values subscribed by Protection Functions
[IEC 61850-7-3:2010 ed2] IEC 61869-
9 :2016
[applicable to SV
published by MU]
Application for Protection Functions
DetailQual
Definition Invalid Question-
able Meaning of DetailQual for
subscribed data
overflow
Value beyond the
capability of
being
represented
properly.
Not Used. Always
set to FALSE X
Prohibited
by IEC
61850-7-3
(§6.2.3)
Even if not used in IEC 61869-
9:2016, may be applicable to SV
or PhV.
The protection application shall
decide how to process input.
outOfRange
Value beyond a
predefined range
of values.
True in case of
Clipping.
Publication with
validity attribute
"Questionable"
X
Publication with validity attribute
as "Questionable" preferred.
The protection application shall
decide how to process input.
Applicable to SV or PhV
inaccurate
The value does
not meet the
stated accuracy
of the source.
Applied Prohibited
by IEC
61850-7-3
(§6.2.3)
X Applicable to any type of
subscribed input data.
badReference
Value may not be
a correct value
due to a
reference being
out of calibration.
Not Used. Always
set to FALSE
X
Publication with as
"Questionable" preferred. The
protection application shall decide
how to process input.
Even if not used in IEC 61869-
9:2016, may be applicable to any
type of subscribed input data.
oscillatory
Signal changes in
a defined time
twice in the same
direction.
Not Used. Always
set to FALSE X
Publication with as "Invalid"
preferred.
Applicable only to binary input
data.
failure
Indicates that a
supervision
function has
detected an
internal or
external failure
Used for detected
errors.
X
Prohibited
by IEC
61850-7-3
(§6.2.3)
Applicable to any type of
subscribed input data.
oldData
If an update is
not made during
a specific time
interval.
Not Used. Always
set to FALSE Prohibited
by IEC
61850-7-3
(§6.2.3)
X Even if not used in IEC 61869-
9:2016, may be applicable to any
type of subscribed input data
inconsistent
Indicates that an
evaluation
function has
detected an
inconsistency.
Not Used. Always
set to FALSE Prohibited
by IEC
61850-7-3
(§6.2.3) X Even if not used in IEC 61869-
9:2016, may be applicable to any
type of subscribed input data
With reference to Figure 6, analog values transmitted via SV from a Merging Unit designed according
to IEC 61869-9, shall not produce invalid data upon any combination of “outOfRange” – “Inaccurate” (as
“overflow” is not used in IEC 61869).
Consistently with the behaviour defined in Table 2 and Figure 6, the expected functional behaviour of a
subscribing protection function has to be defined for each subscribed SV stream. This should be done
in a way aiming at a globally optimised performance of the PACS. A proper specification and validation
of this aspect is a basic requirement for functional interoperability between Merging Units publishing
Sampled Values and subscribing protection functions.
PAC World June 17-20 2019 Glasgow, UK - Paper PW02 - page 8
The functional interoperability between two or more units is when they are able to exchange information
with each other (i.e. they use the same communication protocol) and have a common understanding
about the exchanged message.
Figure 6 – Relation between Quality Attributes and range of analog energising values according to [2]
4. Requirements regarding subscribed GOOSE
Protection functions may also subscribe to GOOSE messages, for example circuit breaker position or
blocking or teleprotection signals. The requirements and tests for these inputs are very similar to those
for protection functions with wired binary inputs. Already today, IEC 60255-1xx series requires protection
IED manufacturers to publish the protection function operate time for contact output and GOOSE
publication, if applicable [10]. One big difference is however that, as for the SV described above, the
subscribed GOOSE messages may have a non-nominal quality attribute. It is required to specify the
behaviour of the protection function for this case.
A generic “simple suspension (blocking) of operation” of the protection function for these cases is not
acceptable, since this would potentially lead to a too low overall availability of protections in a PACS. In
addition, most GOOSE inputs are not critical for the core protection function and can be ignored by
substituting them by a value which also needs to be defined for this case. This has to be done for every
single GOOSE (and also SV) subscribed by the protection function. The Technical Report under
preparation by AhWG3 proposes a formal approach for the specification on this behaviour (cf. Table 3),
based on the Basic Application Profiles which are being defined under IEC 61850.
Table 3 - Table form to specify the expected behaviour of a protection function depending on the quality
of subscribed data
Overflow *)
Faillure
Other (not associated
to detailed quality)
Oscillatory **)
BadReference *)
OutOfRange *)
OldData
Inconsistent
Inaccurate *)
Other (not associated
to detailed quality)
PROCESS
SUSTITUTED
SV or PhV
other DO
Comments
INVALID QUESTIONNABLE
Detailed Quality SOURCE
Input
QUALITY
Meaning of
"Ignore
Input"
Interpretation
of input DA
PAC World June 17-20 2019 Glasgow, UK - Paper PW02 - page 9
5. Requirements regarding published GOOSE
DO published by a protection function also may have associated non-nominal quality values. As for any
other PACS function which is not directly interfaced with the process, most of the DetailedQuality
attributes are not applicable. Normally, a protection function is expected to publish its DO as “Valid”,
even if some of the subscribed data from the function itself is non-nominal. If this causes the protection
function to suspend (block) operation, its DO should be published as “Invalid”, and the suspended
(blocked) status of the protection function should also be reflected in the associated LLN0.health.
As for the subscribed GOOSE and SV, the expected behaviour of the protection function needs to be
specified and tested.
6. Requirements regarding implementation of IEC 61850 Communication Interface
The IEC 61850 communication interface is implemented on the IED level which hosts the protection
function. Multi-functional IED are by now very common. In order to be able to have a meaningful
separation of the functions implemented in one IED, it is recommended to associate each implemented
protection or automation function of the IED to one individual Logical Device. This facilitates
management and testing of each function, allowing, e.g., to switch off one single function or to put one
single function into test mode.
Most of the requirements for the IEC 61850 are driven by the architecture and characteristics of the
PACS and not by individual functions. Requirements of the IEC 61850 interface related to protection
functions may include
number of subscribed SV streams,
capacity of the communication interface (e.g. 100 MB/s, 1GB/s),
capacity to switch between several SV streams, e.g. a nominal stream and a test stream or
redundant stream,
implementation of test mode and/or Sim [8].
7. Testing
In addition to the "conventional" tests of the performance of the protection function, all the new features
described in the previous sections for protection functions interfaced with digital secondary systems
need to be tested [8].
This may require new features in test systems and the development of new tests in IEC 60255-1xx
series. Users have to be aware of the fact that also adequate testing of the other elements is required,
in particular SAMU and/or LPIT associated to their MU and the BIED.
8. Conclusions
IEC AhWG3 has published recommendations [7] for the next steps in order to elaborate requirements
for protection functions covered by TC 95 (IEC 60255 series) interfaced with digital secondary system.
These recommendations include:
Maintain AhWG3 in order to finalise the Technical Brochure describing the findings and
recommendations in detail. TC95 has decided in its TC meeting in 2018 to convert AhWG3 in
a permanent TC 95 WG (WG 2), with the intention to propose also participation to other relevant
IEC TC, in particular TC 38 and TC 57.
Define mandatory requirements and tests for a number of general features, possibly in a new
part of IEC 60255 (IEC 60255-1xx series) giving general requirements for protection IED with
digital interfaces.
For each functional part of IEC 60255, add the relevant requirements and tests for protection
functions. This can be done at the same time as an existing standard is revised or a new
standard is developed.
PAC World June 17-20 2019 Glasgow, UK - Paper PW02 - page 10
Create a new part of IEC 60255 for IED interfacing binary I/O (BIED).
Investigate if a part of IEC 60255 describing additional requirements for multifunctional IED
interfaced with digital secondary system is necessary. This should cover minimal requirements
for making functions independent from each other in order to be testable, e.g. using one
separate LD per function.
WG 2 is now formally installed and its work program has to be defined on the base of the above
recommendations.
9. Bibliography
[1] IEC 61869-6:2016 Instrument Transformers Part 6: Additional general requirements for low-
power instrument transformers
[2] IEC 61869-9:2016 Instrument Transformers – Part 9: Digital interface for instrument transformers
[3] Draft CDV2 38_599e IEC 61869-13 Instrument Transformers – Part 13 Stand Alone Merging Unit
[4] Draft IEC 61850-7-6 Guideline for definition of Basic Application Profiles (BAPs) using IEC 61850
[5] IEC 62271-3:2015 High-voltage switchgear and controlgear – Part 3: Digital interfaces based on
IEC 61850
[6] IEC 61850-9-3:2016 Communication networks and systems for power utility automation –Part 9-
3: Precision time protocol profile for power utility automation
[7] IEC 95/391/DC Technical Committee 95: Measuring Relays and Protection Equipment - AHG 3
Use case of digital sampled values instead of analog input - Recommendations for TC 95
[8] CIGRE WG B5.53: TB760 "Test Strategy for Protection, Automation and Control (PAC) Functions
in a Fully Digital Substation Based on IEC 61850 Applications" March 2019
[9] CIGRE WG B5.24: TB to be published "Protection Requirements on Transient Response of Digital
Acquisition Chain"
[10] A Bonetti, M Yalla, S Holst, " The IEC 60255-121:2014 Standard: its impact on distance relay
performance specification, verification and comparison", in IEEE/PES Transmission and
Distribution Conference and Exposition (T&D), 2016
[11] J.Y. Astic, V. Leitloff, Th. Buhagiar, A. Kurtz Ph. Brun, S. Vigouroux, J.P. Cayuela: "Postes
Intelligents" - Design, Test and Commissioning of Rte's first completely Digital Substation. PAC
World Magazine Sepember 2018
[12] PAC World Magazine - "Digital Substation" September 2018 issue
[13] S. Holst, J. Zakonjsek, Transient Behaviour of Conventional Current Transformers used as
Primary Transducers and Input Elements in Protection IEDs and Stand Alone Merging Units"
CIGRE Study Committee B5 Colloquium, August 25-31 2013, Belo Horizonte, Brazil,
Acknowledgement
The author thanks the International Electrotechnical Commission (IEC) for permission to reproduce
Information from its International Standards. All such extracts are copyright of IEC, Geneva, Switzerland.
All rights reserved.
Further information on the IEC is available from www.iec.ch. IEC has no responsibility for the placement
and context in which the extracts and contents are reproduced by the author, nor is IEC in any way
responsible for the other content or accuracy therein.
PAC World June 17-20 2019 Glasgow, UK - Paper PW02 - page 11
About the authors
Andrea Bonetti graduated as electrotechnical engineer at Sapienza University of Rome, Italy, in 1993,
after having studied the first two years of engineering at Universitá di Trento, Italy. After five years in
ABB Italy as protection engineer, Andrea worked 10 years as HV relay protection specialist at HV relay
protection manufacturer ABB Grid Automation Products in Västerås, Sweden, for relay post-fault
analysis, relay settings, commissioning support and training for distance protection line differential
protection, with IEC 61850 and conventional applications. From 2008 to 2013 Andrea worked at Megger
in Stockholm, as product manager and technical specialist for relay test equipment, dealing with the
development of IEC 61850 test set and tools, test algorithms for distance protection and transformer
differential protection relays. From 2013 to 2018 Andrea worked as consultant in Relay Protection and
IEC 61850 Applications: procurement specification for TSOs, IEC 61850 specification and attendance
for FAT/SAT, IEC 61850 troubleshooting in operative substations, trainings, IEC 61850 top down
specification and engineering process, development of IEC 61850 test equipment and tools. From April
2018, Andrea works at Megger in Stockholm, as senior specialist in relay protection and IEC 61850
applications. Andrea holds a patent in the area of IEC 61850 testing tools and algorithms. Active member
of the IEC TC 95/MT 4 since 2006, Andrea has been sub-group leader for the development of the IEC
60255-121 standard and has received the IEC 1906 Award in 2013. Since 2008 Andrea is a guest
lecturer at KTH (Royal Institute of Technology, Stockholm) for IEC 61850 for Substation Automation
applications.
Volker Leitloff (1965), studied Electrical Engineering at the university of Stuttgart/Germany from where
he earned the Dipl-Ing. degree in 1991. From 1991 to 1994 he has been preparing his PhD-thesis at the
Laboratoire d'Electrotechnique de Grenoble and received the Dr. INPG degree from the Institut National
Polytechnique de Grenoble (INPG) in 1994. From 1994 to 2002, he was with the R&D Division of
Electricité de France were he worked successively on network protection and on transformers and
network technology. Since 2003, he is with the French Transmission Network Operator Rte, where he
works on protection of transmission networks and substation control. He is chair of IEC TC38
(Instrument Transformers), convenor of IEC TC95 AhWG3 (now WG2) Digital I/O of protection IED, past
convenor of CIGRE WG B5.06 on DSAS Maintenance and actual or past member of IEC TC38WG37,
TC38WG47, TC95MT4 and CIGRE WG 34.10, B5.10, B5.13, B5.43, B5.53, B5.64, B5.69 and the SAG
of SC B5.
Hao CHEN (1980), studied Electrical Engineering at Southeast university/China from where he earned
the Bachelor of Engineering degree in 2002 and Master of Engineering degree in 2005. From 2005 to
2011, he was with the Nanjing power supply company where he worked on power grid protection and
control. From 2011 to 2015, he has been preparing his PhD-thesis at Southeast university and received
the PhD degree in engineer in 2015. Since 2011, he is with State Grid Jiangsu Electric Power Co., Ltd.
where he works on protection of transmission network and substation control. He is active member of
IEC TC95 AhWG3 (now WG2) Digital I/O of protection IED.
Lei XU (1976) received his Master’s degree in electric power system automation from State Grid Electric
Power Research Institute in 2001.Then he joined NR Electric as an R&D engineer. From 2001-2003 he
developed protection related products and from 2003-2007 he developed intelligent primary equipment
such as LPIT, MU CSD and BIED. From 2007 he worked as the project manager and now the principal
engineer in digital substation department. Being the team leader, he leads the development and
implementation of the first generation digital substations in China. He is member of IEC TC17MT2,
TC38WG37, TC95MT2/MT3/WG2, member of CIGRE A3.35, B3.39, B5/D2.67, B5.70 and convener of
B5.59.
PAC World June 17-20 2019 Glasgow, UK - Paper PW02 - page 12
Dehui CHEN (1977), received his bachelor and master degree in 1998 and 2007, and majored in power
system analysis and information telecommunication respectively. Now Dehui is a research engineer in
State Grid Electric Power Institute in Nanjing. From 1998 to 2003, as relay protection engineer, dealing
with testing, FAT, SAT and commission. From 2004 to 2007, Dehui enrolled as candidate for master
degree, engaging in study with how to implement protocol stack using graphic language. After
graduation from university 2007, he worked as a power system engineer, and was dealing with R&D
related to domain of relay protection, substation automation system. Meanwhile, as project leader, his
responsibility for system integration of Yan’an 750kV smart substation which include ECT/EVT, Merging
Unit, IEC 61850 process bus, relay protection with digital I/O, etc. which also was the highest voltage
pilot smart substation project in China. Additional, he is member of TC57WG10, TC57WG17,
TC57WG19, TC95WG2, CIGRE B5.59 and he is also leading the task force IEC TR 61850-90-22.
Additionally, Dehui is secretary of China IEC TC57 as well.
Ahmed Mohamed is graduated as an Electrical Power Engineer from Helwan University- Egypt in 2005.
He is working as Protection and Control Engineer since 2006. He started in Egyptian Electricity
Transmission Company (EETC) then moved on 2008 to Dubai Electricity and Water Authority (DEWA)
and from 2013 untill date is working in Scottish and Southern Energy Network (SSEN), Glasgow, UK.
He is working in the Transmission sector as a P&C Engineer for the large Capital Projects and is involved
in a different innovation project which is handling/utilising the digital Input for the protection relays and
Process bus implementation. He is a member of the IEC TC 95/WG2 “Protection functions with Digital
input/output".
ResearchGate has not been able to resolve any citations for this publication.
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  • Conference Paper
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    The transient behaviour of a conventional current transformer (CT) is characterized by the performance before and after CT saturation. Before saturation the transient behaviour is defined by the transfer function and the frequency response. The transient behaviour related to CT saturation is more or less decided by the time to saturation. Different types of CTs have different transient behaviour. Conventional CTs do not have the ability to continuously reproduce a DC component. However, the different types of CTs have more or less capability of reproducing the DC component for a limited time. Especially CTs with big airgaps have poor ability of reproducing DC components. Mixing this type of CT with other types of CTs for a differential protection can be a potential risk of unwanted operations.