LESSONS LEARNED OF IEC 61850 BASED FUNCTIONAL PROTECTION CONNECTED TO NCIT AND SAMU

Philippe Brun, GE Grid Solutions, France - philippe.brun@ge.com V. Leitloff , RTE, France - volker.leitloff@rte-france.com

S. de Langle , RTE, France - sabine.de-langle@rte-france.com

M.Z. Kentjie, GE Grid Solutions, Indonesia – muhammad-zulham.kentjie@ge.com

1. Abstract

The main objectives of the project “Postes Intelligents” is to design, test, commission and energize the next power grid “Smart Substation” in France involving full IEC 61850 and IEC 62439-3 process bus Intelligent

Electronic Devices (IED) with mixed analog quantities acquisition and digital signal for tripping. This paper describes operational experiences and lessons learned from integrations test to Factory Acceptance Tests (FAT)

and depicts first feedbacks of Site Acceptance tests (SAT).

Digital Substation, Process Bus, NCIT and SAMU, IEC 61850

2. Introduction

The “Postes Intelligents” project [1] [2] [3] [7] is a French Smart Grid Project held by a consortium of 6

industrial companies. This project is fully compliant with the Global Strategy of SMART GRID (Reduce environmental impact, network stability enhancement, energy efficiency, global demand increase) in which the Smart Digital Substation is one of the key technology, no Smart Grid without Substation digitalization.

In this context, “Postes Intelligents” project includes advanced smart features such as Local State Estimator, incident management, asset monitoring and management, substation asset protection and cybersecurity. This

digital substation and its related assets, HV primary equipment, IEDs and sensors, are digitalized and fully compliant with IEC 61850 standard. One of the major aims of the project is to design, test and commission a Protection, Automation and Control System (PACS) using IEC 61850 and IEC 62439-3 process bus both for the analog data acquisition of the protection functions and for tripping. The test strategy defined was to define Integration Tests to validate the

performances of the functional chain. The Factory Acceptance Tests then focussed on System Integration Tests to validate full interfaces and compliancy in the overall architecture.

The integration test of the complete functional chain, including Merging Unit (MU), switches, time synchronisation, protection IEDs and Switchgear Control Units (SCU) represents an important step of the validation of this concept. It has to be highlighted that the process bus is used both for the analog quantity data

acquisition (e.g: CT & VT) and for tripping. No conventional hard-wired back-up system is implemented, neither for analog acquisition nor for control and trip.

The test configuration used is aligned with the architecture which will be implemented in the substations. Most of these tests have been performed between March and May 2015 for all main protection functions, including distance protection, line differential protection and transformer differential protections, using both

Stand Alone Merging Units (SAMU) connected to Conventional Instrument Transformers (CIT) and Merging Units (MU) associated to Non-Conventional Instrument Transformers (NCIT). The NCIT current sensors used in

the project are based on the Faraday Effect and the voltage sensors are Low Power Capacitive Dividers [1]. Both are connected to a Merging Unit (MU) which publishes Sample Values compliant with IEC 61850-9-2 LE

guideline. The tests were performed at a test facility from General Electric Grid Solutions in Lyon for the functions involving NCIT (distance and line differential protection) and at RTE’s SMARte test platform in Paris [4] [5]

for the transformer differential protection. This paper describes the major findings and conclusions of these tests.

3. Integration test strategy

There are different bay configurations in the project which need to be taken into account in the integration test

strategy. A common configuration can be defined as the following test schemes:

1. NCIT connected to MU, MU publishing Sample Values on IEC 61850 Gbps HSR process bus

2. CIT connected to SAMU, SAMU publishing Sample Value on IEC 61850 Gbps HSR process bus 3. IED Protection connected to IEC 61850 Gbps HSR process bus publishing GOOSE trip

4. Switchgear Control Unit connected to IEC 61850 Gbps HSR process bus subscribing to GOOSE trip

A simplified architecture is shown in Figure 1.

Figure 1 : Simplified PACS architecture at Process level

A standard test platform has been established in order to perform integration tests with the real field devices, see Figure 2.

Figure 2 : Integration Test Platform

The overall test strategy was to perform a part of the generic functional test use cases defined by RTE for protection IEDs Qualification and Certification. The system in Figure 1 was then seen as a Black Box where

Inputs are Currents & Voltages and Outputs are trip contact.

It has to be noticed that some additional dedicated process bus tests were performed to disturb IEC 61850 Ethernet bus and to verify behaviour of Protection, Automation & Control System (PACS). Analog quantities are injected directly on primary side of Non-Conventional Instrument Transformer by a test

equipment, see Figure 3 . Same test equipment is used also to inject secondary analog quantities to the SAMU for #2 test scheme

Figure 3 : Multiple windings through NCIT core to get higher measured currents

3.1 Distance protection tests

3.1.1 Test setup

Due to the characteristics of the project, Distance Protections are used in two different configurations: connected to a Stand Alone Merging Units, connected to a Merging Unit associated with an NCIT

The test setup for voltage and current injection is shown in Figure 4 For convenience, both the SAMU and the NCIT/MU were connected, but only one of both was used for a given

test and only one protection IED was connected to the process bus. The photo Figure 2 shows the tested equipment and a part of the test setup.

The test included cases of emission or reception GOOSE for a blocking scheme.

Figure 4 : Test setup of the functional test of distance protection

It has to be mentioned that actual Distance protection IED has two IEC 61850 Mbps SAN ports. The “redbox” is an IEC 62439-3 compliant redbox switch and the Switchgear Control Unit (SCU) integrates also a redbox feature and high break high speed trip contact for Trip Goose Type 1A as defined in IEC 61850-8.1.

The NCIT Merging Unit and IEDs are PTP synchronised with a GPS Master Clock according to IEEE 1588 standard. Finally, a monitoring test equipment was connected into the test scheme to asses performances of Protections IED in Conventional mode (Relay trip contact) and in Distributed mode (Relay trip contact in SCU is operated by Protection Trip GOOSE).

3.1.2 Results and lessons learned

After some initial problems regarding the configuration of the NCIT MU due to the modified scale factor, the tests confirmed that the distance protection functions are interoperable with the SAMU and MU data acquisition and for the different tested configurations, even for fault scenarios including significant transient phenomena. The time difference between trip by protection contacts and the reception of the trip GOOSE by the test set was

initially high, in the range of 5-8 ms. No time difference between trip protection contacts and SCU trip contact was observed. The analysis made appear that an incorrect configuration of the VLAN was responsible for this situation. Additional tests were scheduled during FAT and confirmed a better stability and improvement of the operating time : 1-3 ms faster than in Conventional Mode. The test scenarios included the opening of the circuit breaker after trip. The voltage sensor is based on a

capacitive divider. If the circuit breaker opens when the voltage is not zero, which is usually the case, there can be trapped charges on the line if both line ends are equipped with this type of voltage sensor. This phenomenon is also known for lines equipped with conventional capacitive voltage transformers. In the case of the low power capacitive voltage divider, these trapped charges also appear on the secondary capacitance. The MU uses thus an

offset compensation algorithm in order to correctly restitute zero primary voltage in case of a trapped charge on the secondary capacitance and in order to correctly represent the phase-to-ground voltage after reclosing. In the configuration that was tested, this lead to a virtual oscillation and virtual voltage peaks in the line-to-ground voltage after injection of zero volt in the secondary circuit simulating the opening of the circuit breaker. Although this phenomenon did not adversely affect the protection operation, as the circuit breaker had already

opened, and there was no risk of unexpected trip, an improved compensation algorithm was implemented since several other PACS functions, including incident analysis, were potentially concerned.

In conclusion, the integration test scheme conducted on this single Protection IED were positive but confirmed

that VLAN configuration in process bus redbox switches needs dedicated configuration and appropriate skills by engineering team.

3.2 Line Diff protection tests

3.2.1 Test setup

« Postes Intelligents » digital substation is implementing different Current Line Differential protection schemes. They are used in several complex use case configurations where current line diff protections are :

1. Mixed Mode: Connected directly to CIT on one end (Conventional Bay) and to MU NCIT on remote end (Digital Bay inc. sensors)

2. Conventional Mode: Connected to SAMU on both ends. SAMU connected to CIT (Both ends are Digital Bays)

3. Non-conventional Mode: Connected to MU NCIT on both ends (Both ends are Digital Substation inc. sensors)

4. Hybrid Mode: Connected to SAMU on one end (Digital Bay) and to CIT on remote end (Conventional

Bay)

It is anticipated that in the future #1 will be frequently encountered when deploying NCIT in substations (refurbishment). This is a critical protection scheme that needs to be tested. In fact, analog quantities acquired are managed by different technologies and hence time synchronisation can have a direct impact on the

performances and stability of Current Line Diff protections. An additional protection scheme #4 with SAMU on one end and CIT on remote end will be met also very often, but this configuration is not in the scope of the “Postes Intelligents “ project. Nevertheless, Protection interfaces are standard interfaces (IEC 61850 9.2LE from SAMU or MU NCIT) which should mitigate potential deviations in term of performances between #1 and #2.

Based on the generic test platform described in §3 and the test platform for Distance protection described in §3.1.1, the Figure 5 shows the test setup that was used for the test use case #3. In the “Postes Intelligents” use case, this scheme aims to differentiate between a fault on overhead and underground sections of a line, in order to inhibit recloser if the fault is on the cable section. It involves two different types of optical current sensors

which did not have exactly the same transient behaviour. In this configuration, both MU are at the same substation, one being connected by an optical fibre with a length of several kilometers to the NCIT installed at the transition between overhead line and cable. This explains the common time synchronisation and the use of the same HSR process bus shown in figure 5. The test setup #2 for the SAMU/SAMU and #1NCIT/conventional protection tests were similar, with an

adaption of the analog injections and use of SAMU or a protection IED with analog inputs. As far as the functional environment of the protections is concerned, this arrangement is close to the architecture of the “Postes Intelligents“ PACS. In the substation, a Bay Controler Unit (BCU) would be in the HSR ring. This latter BCU is represented by the

second SCU which has identical process-bus interface requirements. The available MU, SAMU and protection IED could not be directly inserted in the HSR ring. Their 9-2 port was thus connected to a SCU or a switch, respectively. One objective for all cases was to verify reliable operation for faults involving significant transients, especially stability for external faults. A subset of test scenarios used by RTE for the qualification of differential line

protection was selected under this aspect. One of the main challenges of these tests was the requirement to inject primary current values for the tests involving NCIT. Conventional test sets and amplifiers are often limited to several 10A to around 100A and cannot inject neither a primary load current nor a primary fault current. Since the NCIT used in the project are torus and only the current in the cross-section is measured, it was possible

to wind the cable coming from the current output several times through the hole of the NCIT multiplying the primary current seen by the sensor by a factor of 20 or 30 (figure 2). More windings were not possible due to saturation of the current amplifier used in the test, and the current range was thus not sufficient for the selected test cases. It was therefore necessary to change the internal scaling factor of the merging unit in order to obtain Sampled Values in the required range.

This highly increased sensitivity of the NCIT allowed for correct testing, but artificially increased noise has been

observed as a consequence. There is a similar issue for the voltage injection. In the case of the NCIT used in the “Postes Intelligents” project, the voltage sensor is a low power capacitive voltage divider. The secondary voltage

range of the output connected to the proprietary Merging Unit is in the range of below 200V. It was hence possible to directly inject this voltage from the test set. Although voltage injection was not required for the tests of most differential protections use cases, it was implemented for the test of distance protection (cf. §3).

Concerning the process bus, its setup and configuration, namely the switches, but also the protection IEDs, has to be performed prior to the tests and requires specific knowledge. This caused some delay in the first test phases

before the issues were understood by the actors. This added complexity to the normal test setup of conventional protection testing has to be taken into account for process bus based tests.

Figure 5 : Test setup of the functional test of current differential protections – Use case #3

3.2.2 Results and lessons learned

Additionally to the experience feedback described in §3.1.2, there were initially issues related to the set up of time synchronisation of MU NCIT and Current Line differential protections. In fact, despite the fact that both IEDs are located in same area, it was required to set both protection IEDs to Global synchronisation. For easier test set-up, there is thus a trade-off to be made to perform the test either in a slightly different configuration of

the protection IED than that used in PACS after commissioning or to force the synchronisation signal to global. The latter is not always easily achievable depending on the test equipment. Delay of sample values and process bus disturbance forced by specific test equipment as mentioned in §3 have originally impacted the current line diff protection stability. It has requested more robustness of 9.2 SV frames control by IED protection to ensure: management of smpCNT, smpSync and maximum jitter allowable.

Moreover, due to some analog value range limitation of SAMU, it has been detected that management of the

attribute q.validity in the SMV frame can have a direct impact of the IED protection behaviour. Based on IEC 61850 9.2LE standard and IED configuration, protection was correctly inhibited when q.validity was set to

INVALID. Nevertheless, IEC 61850-7.3 standard §6.2.3 define some detailed conditions for the quality. Those conditions are not formulated in an accurate enough way to ensure interoperability between SAMU for any vendors., They mainly focus only on “Analog to Digital Conversation” issues which can be interpreted in

different ways. This has raised the question of what should be the behaviour of SAMU and protection in those cases [8].

Comparing to a conventional system, this is like a small CT saturation to cause the protection system to be disabled. It can be argued that, if the SAMU are properly designed and configured, their analog range will allow

for the highest possible fault current with a margin. Furthermore, the SAMU is an IED and so is a smart device. Its own function as described in IEC 61869 is t the acquisition of analog values coming from instrument transformer. In the conventional substation this function is embedded in protection IED for instance where some

additional features are mandatory e.g: CT Saturation detector, Current transformer Supervision, Voltage Transformer Supervision. In the digital substation, these functions may be distributed and hence SAMU may

include some of those functions. This expected behaviour might be used in utility specification and/or be introduced in the different relevant standards i.e IEC 61869 for SAMU and IEC 61850 for PACS [8].

Test use case #3 was played at first stage and after initial concerns mentioned above, the tests conferment that the differential protection are interoperable with the MU NCIT. This holds for different test configurations including fault scenarios with significant transient phenomena.

In order to evaluate the performance of the trip via GOOSE and SCU, the closing of the physical contacts of both the differential protection (grey points in Figure 6) and the SCU (blue points) were recorded. In addition to this,

the time of emission of the trip GOOSE was monitored (red points). The time reference was based on the fault inception (analog injection), which results thus in “absolute” trip times and makes comparison with conventional schemes without process bus possible.

Figure 6 : Differential line protection configuration: Trip times for AG fault (blue: SCU contact; red: protection trip GOOSE; grey: protection trip contact) – Use case #2

Figure 6 displays a plot of the initially obtained results for 30 tests of the same fault (single phase to ground)

before the mitigation mentioned above. The lines correspond to the mean values, which are resumed in the table of figure 6. The SCU contacts close in average about 1ms after those of the Protection. This delay can thus be identified as

the additional trip delay due to the transmission of GOOSE via the process bus. The time difference between reception of GOOSE by the recording device (which is delayed with respect to the emission of this GOOSE) and

the closing of the SCU contact is very stable, but some small dispersion of the time difference between closing of the contact of the differential protection and those of the SCU can be observed. They often close almost at the

same moment, but sometimes the difference is in the range of 2-3 ms. Given the characteristics of the network around the “Postes Intelligents” substations, this additional trip delay remains acceptable for RTE for this particular case. It has to be mentioned that the Differential Protection had normal trip contacts whereas the SCU has high break high speed contacts. This contributes to achieve an almost equivalent trip performance. These trip times have to

be compared with the trip times of a completely conventional scheme (analog inputs) in order to evaluate the

delay due to the sampling and transmission of 9-2 values. No such analog IED was tested in parallel during the

functional tests. The most constraint case tested corresponds to test use case #1: MU NCIT with a Digital IED on one end and

CIT connected to conventional IED. Both protections IED are connected by a direct protection link network. Grid simulations were performed for Overhead line fault and Underground cables with high capacitive current. It has been noticed that for any kind of fault, protection behaviour and stability was correct. In this worst case, real

different time synchronisation acquisition on both ends is managed by a specific mixed mode configuration in IEDs which add some delay in analog sample acquisition to resynchronise sample values on both end. The

impact of this workaround solution was a longer and more variable operating time (+-10 ms). Investigations are still ongoing to improve performances of this protection scheme. A special focus needs to be considered on this

kind of protection scheme in mixed mode because this use case is very important in the Digital Substation deployment.

3.3 Factory Acceptance Test strategy

In the "Postes Intelligents" Digital Substation architecture, Merging Units and Switchgear Control Units are installed in yard cabinets (ACN) close to the HV equipment. In order to perform a comprehensive FAT on the complete system, all cubicles of the central system and all external cabinets of the 225 kV switchyard have been

assembled on the test platform.

Figure 7 : Yard cabinets (ACN) closed to HV primary equipment

This enabled a classic FAT approach based on end-to-end testing until the terminal blocks of the ACN of the PACS. The usual test protocol had to be adapted, mainly for the same reasons and using the same tools as discussed in the previous section. Due to the number and size of the external cubicles, the capacity limit in terms of surface of the allocated test area has been attained. The system has been shipped on site in January, 2016.

Concerning the 225 kV system, several tests usually performed during FAT have been added to the SAT because they could not be performed in the FAT phase (especially for sensors connected in IEC 61850 or ModBus not available on the test platform) or have not been successful for various reasons.

3.3.1 Results and lessons learned

Testing of a protection scheme consisting of a Differential Line Protection and a Fault Detection System during

FAT has raised some minor concerns due to the integration test strategy. This scheme is based on a Differential Line Protection used to disable the reclose cycle if the fault is situated on the underground part of a mixed underground / overhead 225 kV line. All current sensors concerned were NCIT associated to different Merging Units. In order to perform the test of the complete scheme, it was thus necessary to inject two SV streams of the

same current form but originating from two different sources. Whereas this can be done with available 9-2 test

equipment, two issues arose: The test equipment had a 100Mbps Ethernet port whilst the HSR process bus expected a 1 Gbps

equipment to be connected. This problem was mitigated using a commercially available standard switch compatible for both network types a connection element.

In the first test, HSR process buses of the two systems were connected via a switch without any

particular configuration in order to inject the SV coming from the test equipment. This network connection has collapsed both process buses and SV were not received correctly by IEDS, generating a

“Digital Short Circuit” of measurements. Only a virtual separation of the two process buses using Ethernet test equipment made the test of the complete scheme in this configuration possible (See Figure

8).

Figure 8 : Parallel injection of test SV in redundant process bus

3.4 Site Acceptance Test outcomes

Site Acceptance Test and Commissioning tests include the verification of the connection between the PACS on one hand and the HV equipment, other site installations and the telecontrol centre on the other hand. As mentioned above, the scope for "Postes Intelligents" of these tests is extended for several reasons:

Impossibility to test a complete functional chain in FAT for some equipment (e.g. NCIT, monitoring sensors associated to HV equipment not available during FAT, circuit breaker with control functions

integrated in the PACS). Verification of the functional chain in case of system parts added later which could not be tested in their

final configuration during FAT. As mentioned above, this will be the case for the part of the PACS

associated to the 90 kV level. Complementary tests for functions with not conclusive test results in FAT.

The time required for this additional on-site tests has to be taken into account in the commissioning schedule of the PACS. Concerning the NCIT, the SAT also covers the verification of proper association of phase and orientation. It is of

major importance to make sure that a current or voltage coming from a measurement transducer installed on, e.g., phase A appears in the Sample Value published by the associated Merging Unit as a value associated to said

phase A. In addition, it has to be verified that the sign of the measurement is correct. With conventional current- and voltage transformers, these tests are well established and straight forward. They are based on injection of secondary analog values at the proper hard-wired terminal, either at the bay cubicle or, during SAT, at the

Switch

Switch

HSR System B

Test system - injection of SV

Configured Switch

SV A SV B

SV

SV

HSR System A

terminal of the CT / VT themselves. If NCIT requiring injection of primary values are used, this simple

verification becomes more complicated. As mentioned above, functional test are mostly based on injection of SV, bypassing the Merging Unit associated

to the NCIT. It is thus not possible to use these tests to verify the correct connection. One could argue that a visual verification of the connecting wires might be sufficient, but there might be errors in the labelling of the connection wires or in the connection themselves. For "Postes Intelligents", it was decided that it is acceptable to

skip this verification during FAT, but that it is mandatory to verify the complete chain during Site Acceptance Tests.

This implies an injection of primary values for the optical current sensors (cf. Figure 9). The SAT thus includes a step where a cable is wound several times through the torus of the optical current transformer. This cable is

connected to a test injection device with a capacity of several 10A, yielding a virtual current in the centre of the NCIT torus in the range of a primary load current. The direction of the winding has to be verified carefully in order to validate also the sign of the acquired primary current. A similar test setup was used to test the functional chain of the protection functions [6]. For the capacitive voltage divider, it was possible to inject a voltage of about 100 V AC at the contacts of the

secondary capacitance, which corresponds to about half the nominal primary voltage. Finally, a final test and verification of the phasors and signs of both currents and voltages has been added during the first energisation of the feeders. This test is also included in the standard commissioning tests of conventional PACS.

Figure 9 : Test setup for injection of current in the optical current sensors.

Other lesson learned was collected: weather conditions during SAT have to be taken into account for Distributed

Substation architecture where more IEDs are in the yard closed to HV primary equipment installed in Marshalling kiosk. For Conventional Substations, the majority of IEDs are installed in cabinets located in bay or

main control rooms. This means that more work has to be done in the switchyard and that a close coordination between the operator at the ACN and the operator at the central system / HMI is required.

It also calls for modified test procedures as the hard-wired signal test is basically limited to the switchyard whereas the proper acquisition and propagation of each analog and binary input has to be verified on station

level based on the interfaces provided by the PACS (system records, HMI, event recording). Tent-like shelters for work in the ACN after their installation on site have been designed and used during SAT (cf.Figure 10). They have to be designed in order to withstand adverse rain- and wind conditions. Those outside

conditions created lots of additional work constraints and some delay in the SAT.

Optical Current

Sensor

Test Injection

Device

Figure 10 : ACN with tent-like shelter in pre-SAT phase

4. Conclusions

The first batch of “Postes Intelligents” PACS concerning mainly the 225KV level has undergone comprehensive FAT in 2015. Erection and commissioning on site are under progress in a 225KV/90KV/MV substation in Northern France. Additional batches of features are planned.

The integration and functional tests of the protection scheme has given evidence that the tested full digital chain consisting of process bus interconnected elements including SAMU and NCIT is operational. This includes

stability and selectivity for any kind of fault and events. Main lessons learned are :

Time synchronisation: For some IED, time-sync is a mandatory feature. Difficulties for test setup and

configuration need to be addressed at early stage to ensure suitability of test use cases. There is Need for a coordination of time synchronisation on substation level between clocks and applications. It has to

be defined under which conditions the synchronisation DA of data is set to GLOBAL / LOCAL / NOT SYNCHRONISED. The behaviour of the different subscribing applications has to be specified consistent with the former requirement. There is a risk of malfunction or global under optimisation,

especially for differential protection functions, if this is not done correctly. Globally, it seems to be useful to establish a time synchronisation coordination between the acquisition

equipment for the global time reference (GPS), master clocks of the and the subscribing PACS functions.

Protection IED networking: Most of the protection IED have separated Ethernet ports between Goose

and SMV. Those ports are generally Mbps ports and may have no redundancy features according to IEC 62439-3. Point to point connections do not need to have faster bandwidth (e.g : PRP) but with the growth of efficient ring architecture, the development of 1 Gbps HSR ports has to be taken into account in IED protection roadmaps.

Mixed mode: next Digital Bays within next generation substations will have to be interconnected with Conventional/Legacy bays. It is important to validate the interoperability for protection communications to assess performances and stability.

Switch/Network configuration: Special attention needs to be done on Switch configurations within the substation (process, interbay and station bus). For instance, an incorrect configuration of VLAN may

collapse network data. Switch configuration has to be managed in System configuration like IED protection & control configurations and part of the Validation plan. This also calls to include this feature in the training of the PACS test- and maintenance staff.

Interoperability between SAMU and protections: An precise definition of the Quality bits is required in order to configure correctly IED protections. This definition can be part of user specifications and

should, in any case, be included in the documentation associated to the SAMU. The same holds for MU associated to NCIT.

SAMU features: SAMU is a smart distributed IED and may, in the future, include application functions related to the associated HV primary equipment (e.g : CT Saturation detection). This information may be included in the published quality bit data type.

Ethernet disturbances: Special test cases with special test equipment have to be established in order to

validate robustness of IED and related functions when Ethernet network fails. IEDs behaviour may be impacted strongly.

Distributed architecture: Digital substations and its related architecture are linked to Distributed/Decentralised Functions and hence "smarter" monitoring and operation functions will be associated to HV Primary equipment. More SAT and commissioning activities will be performed on the

field, it is then strongly recommended to anticipate in these activities outdoor working conditions with Electronic devices and specific test equipment, access to remote main control functions, …

5. References

[1] Th. Buhagiar, J-P. Cayuela, A. Procopiou, S. Richards: Poste Intelligent – the Next Generation Smart Substation for the French Power Grid. PS3-305 – CIGRE SC B5 Colloquium September 2015 Nanjing, China.

[2] Th. Buhagiar, Jean-Paul Cayuela, Denis Chatrefou, Jean-Luc Rayon, Simon Richards: The Smart Substation Project: Poste Intelligent – the Next Generation Digital Substation for the French Power Grid. MATPOST November 2015, Lyon, France

[3] Th. Buhagiar, G. Rebollar, G. Courcoux – “Postes Intelligents” SG Paris 2013

[4] V. Leitloff, S. Aupetit, Ch. Guibout, M Jobert: Qualification- and type Tests of Protections at RTE using a Real-Time Simulator. PS1-111 CIGRE SC B5 Colloquium, August 2013, Belo Horizonte, Brazil

[5] V. Leitloff, S. Aupetit, Ch. Guibout, M. Jobert, Ch. Bertheau: Validation of Test Procedures for Generic Qualification of Distance Protections using a Real-Time Simulator. DPSP April 2014, Copenhague, Denmark

[6] Th. Buhagiar, J-P. Cayuela, A. Procopiou, S. Richards: "Poste Intelligent – the Next Generation Smart Substation for the French Power Grid" DPSP March 2016, Edinburgh, UK

[7] V. Leitloff, S. Courtemanche, D. Baurand, A. Kurtz, B. Ilas, JP. Cayuela, G. Duverbecq, Ph. Brun, S. Vigouroux, Y. Leloup : Experience feedback of Qualitifcation Tests, FAT and SAT of completely Digital IEC 61850 based PACS.

PACW June 2016, Ljubljana, Slovenia

[8] V. Leitloff, Ph. Brun, S. de Langle, B. Ilas, R. Darmony, M. Jobert, Ch. Bertheau, P. Ferret, M. Boucherit, G. Duverbecq, JP. Cayuela, R. Bouchet: Testing of IEC 61850 based Functional Protection Chain Using Non-Conventional Instrument Transformers and SAMU. DPSP March 2016, Edinburgh, UK