Presentation 0.1
Commissioning of a distributed busbar protection using a system-oriented test in the field Florian Fink, OMICRON electronics GmbH, Austria,
[email protected] Thomas Hensler, OMICRON electronics GmbH, Austria,
[email protected] Frank Trillenberg, NRM Netzdienste Rhein-Main GmbH, Germany,
[email protected] Jörg Köppel, ABB AG, Germany,
[email protected]
Abstract In a substation in Frankfurt the existing busbar protection is replaced by a new distributed numerical busbar protection. Therefore the new busbar protection is installed in parallel to the existing one and should replace it after commissioning. The new busbar protection provides a separate zero sequence differential protection. Since the 110kV network for the city of Frankfurt is low-impedance grounded, single phase to ground faults can cause fault currents on the busbars, which are only slightly higher than the load currents. Using a dedicated zero sequence differential element does avoid an over-stabilization of the differential protection. With a system-oriented approach for testing the distributed busbar protection it is possible to inject currents into all field units simultaneously and conduct a complete test of the whole protection system. Within a new application software the topology of the busbar is modelled, so that the all the transient currents (optional voltages) can be calculated for the different fault and operation scenarios automatically using a dynamic network simulation. These signals can be applied to the protection using multiple test devices, which are time-synchronized using GPS, and all the reactions of the binary signals from both the central protection unit and all field units can be analysed and assessed within the software immediately. Using an iterative closed-loop approach the test software can simulate fault scenarios, where a correct reaction of the protection system is considered in the transient simulation. A detailed analysis and assessment of the selective operation of the breakerfailure protection and the behaviour for faults in the dead zone between the CT and the circuit breaker in the coupling field is possible.
1 Introduction The utility Netzdienste Rhein-Main GmbH (NRM) did a retrofit project to replace a busbar protection in substation Kruppstraße in Frankfurt (Main), Germany. Within this project the existing busbar protection was replaced by a distributed busbar protection REB500 from ABB. Therefore first the new protection system was installed in parallel to the
existing one so that it could replace the old system finally. A big advantage of the new numerical busbar protection is its separate zero sequence current measurement and its dedicated zero sequence differential elements. The 110kV network for the city of Frankfurt (Main) is low-impedance grounded, so that fault currents for single-phase-to-ground faults on the cable network are only slightly higher than the high load currents on the busbars. Using a dedicated zero sequence differential element avoids an overstabilization of the protection behaviour.
Figure 1:
110kV GIS in substation Kruppstraße
With a system-oriented approach for the test of this distributed busbar protection it is possible to inject the test quantities into all distributed field units simultaneously using multiple test devices. So a complete system test of the whole protection system is possible. First in the new application software OMICRON RelaySimTest the topology of the busbar as a primary system has to be modelled (see Figure 2). Then the exact transient signals for the currents (optional even voltages) for all injection points for the different fault or operation scenarios are calculated from the test software using a network simulation. These transients can be injected to the protection system immediately using multiple OMICRON CMC test devices, which are time-synchronized using a GPS-receiver. The binary inputs of the test devices record the reactions of the central unit and all field units for all these simulation cases, so that this can be used for analysis and assessment in the application software immediately.
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2.1
Figure 2: Modelling of the busbar topology within the application software
2 Test setup The double busbar substation Kruppstraße has ten active bays, where one ABB REB500 field unit is installed each. Into each field unit a CMC test devices injects one current triple and records the binary signals for trip, annunciation busbar trip and annunciation breaker failure. Because the CMC test devices are capable to output two current triples, for some cases one test device was used to inject into two neighbouring field units.
Binary signals from the separate central unit
Since the central unit is calculating the overall assessment of the protection system, the binary signals annunciation alarm differential current, annunciation busbar protection trip and annunciation breaker failure were recorded there. The central unit is located about 20m from the next field unit, and from the next test device too. Therefore an additional binary inputs/outputs extension device OMICRON ISIO 200 was used. This devices allows the recording of binary signals which are forwarded as IEC 61850 GOOSE message using a simple network connection to a CMC test device, which are then, together with the information from all binary signals from the filed units, are accessible in the application software.
2.2
Communication to the test devices
For the communication between the test devices, the binary input/output extension device and the controlling PC, an Ethernet network was built up in the substation. The application software can control all 6 CMC test devices using this network, replay the calculated transient current signals on the corresponding test devices and record all binary signals.
ABB REB500 fild units
CMCs
PTP-Transparent Switch ISIO200 CMGPS588 PTP GMC
ABB REB500 central unit
Laptop with RelaySimTest
analog- and binary signals
Ethernet connections
Figure 3:
Scheme of the test setup
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Presentation 0.3
For the time synchronization of the CMC test devices a GPS-receiver CMGPS 588 was used, which provides a precise time synchronization using IEEE 1588 PTP (Precision Time Protocol) over the existing Ethernet connections. The CMGPS 588 device operates as an IEEE 1588 grandmaster clock, which forwards the time information to all CMC test devices over the network. For the Precision Time Protocol the IEEE 1588 power profile was used, which requires a PTPtransparent switch, so that the required time precision (± 100 ns) can be guaranteed between all switch ports.
2.3
Overview of the equipment used
In total the following equipment was used:
6 OMICRON CMC test devices 1 binary input/output extension device OMICRON ISIO 200 1 switch Hirschmann Mach 1040 1 GPS-receiver OMICRON CMGPS588 about 300 m Ethernet cable (including 5 Ethernet cable reels), more than 100 measurement leads, many with length of 6 and 10 m a huge number of power cables and extension socket outlets
Figure 5: The complete equipment for the protection testing did fit into a small van
2.4 Figure 4: CMC test device connected to one ABB REB500 field unit
The overall setup with the 6 synchronized injecting CMC test devices was distributed over a distance of more than 60 m within the substation (see Figure 8). Thanks to the support from the managing coach of the team of protection engineering, Uwe Weisenstein, the complete setup could be done within not much more than 3 hours.
Configuration of the binary input/output extension device ISIO 200
After all test devices were built up and connected, the GOOSE configuration for the ISIO 200 was done for the connected CMC device. Then the annunciations from the central unit could be recorded by the CMC test device.
The preparation of the overall test was very detailed and important. Within a table all the necessary equipment was listed and each test devices was already marked for its used location.
Figure 6: Binary input/output extension device ISIO 200 connected to the central unit
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3 Wiring check Next the check of the wiring had to be done. Therefore unsymmetrical currents were injected into one or two bays using only one test device. This should show, that the currents are measured correctly on the individual field units and that the corresponding binary signals can be recorded by the CMCs.
3.1
Simulation of CB and isolator positions
For the simulation of the circuit breaker and isolator positions NRM has developed a simulation box (see Figure 7). This box was connected with each field unit using a multi pin connector. Then it was possible to control all necessary operating positions for the complete substation almost as easy as within a control room. For the tests the same operating positions are taken over into the network topology of the test software accordingly.
Figure 8: Six CMC test devices injecting into the whole protection system in a synchronized way
4.1
Figure 7: Simulation box from NRM to simulate the isolator and CB positions
4 Simulation of fault scenarios After finishing the setup for the tests, the following tasks could be done quite easy. Within RelaySimTest the network simulation was adapted to the corresponding testing task, at the simulation box the corresponding isolator positions were set so that finally all the test shots could be executed. A rewiring or change of the configuration was not necessary anymore, which obviously eliminated a major source for errors.
Verification of the network simulation
The test document for RelaySimTest has been prepared in the office upfront. Therefore NRM provided all the relevant network data and parameters, such as the detailed topology of the substation, an overview of all the short circuit currents within the 110kV network as well as details of the low-impedance start point grounding. Using network infeeds and passive loads the load flow and maximum as well as minimum short circuit currents were adjusted within the software. With the possibility to input capacitances at the network infeeds, the capacitances of the remaining cable network and the resulting zero sequence currents could be simulated. These values were discussed once again on site and verified, because they are the basis for the following tests.
4.2
Extended wiring check using simulation of stable load flow
Next the standard operation positions of the topology was set with the simulation box and within the test software. The topology was documented within the test report as a comment for later tests. To verify completely, that all test devices are connected correctly and the configuration of the system fits to the network simulation, a stable load flow was put out for 30 seconds. Additionally is was possible to check the data from the network simulation with the data in the online monitor of the central unit. A wrong
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configuration of one of the CT star point directions could be found and fixed immediately. Additionally it could be verified, that the protection system stays stable for the various load flow scenarios.
4.3
Tested fault scenarios
Overall the following fault scenarios were tested: Different faults on both busbars Goal: Verification of the protection zone selectivity Faults on each busbar segment Goal: Verification of the protection zone selectivity Fault within the dead zone in the coupling field Goal: Verify that the fault in the dead zone is recognized correctly from the central unit and that the second busbar is tripped additionally with some time delay Faults outside of the protected area Goal: Verification of the stability for external faults Faults outside of the protection area with external start of the breaker failure function Therefore a breaker failure from an external protection relay was simulated using a binary output of the test device. This signal was then applied to the corresponding field unit during the simulation. Internal faults with breaker failure protection Goal: Simulation of the fault events with and without Iterative-Closed-Loop Faults with invalid position of the tie isolators Goal: Verification of the behaviour of the protection system when a busbar tie isolator has a different physical position then what is reported at the central unit
5 Analysis of fault scenarios For the fault scenarios the trip times of the corresponding field unit and of the central unit were analysed. Depending on the type of fault the assessment based on the trip time and/or no trip was done. The corresponding binary signals could be evaluated either visually directly or measured and assessed automatically. Therefore after a test case all the relevant information was available to do an assessment and document this within a report.
Figure 9: Simulation of the fault scenarios using RelaySimTest in the substation
Test of the circuit breaker failure protection using Iterative-ClosedLoop function The Iterative-Closed-Loop function of RelaySimTest has been proven as useful new test possibility for this case too. Since breaker events within the simulated primary system cannot be applied within the simulation in real-time, RelaySimTest does repeat the simulation until no more new changes of the CBs are done by the protection system. In this example the circuit breaker failure protection could be tested. If the Iterative-Closed-Loop function is active a “normal” trip of the protection system is received: Fault inception – trip command from the protection system – opening of the circuit breaker in the simulation – reset of the trip command from the protection system If the Iterative-Closed-Loop function is turned off, the following case occurs: Fault inception – trip command from the protection system – trip of the breaker failure protection Since here the circuit breaker is not opened by the simulation, the protection system will still recognize the simulated fault current which results in the correct trip of the breaker failure protection.
6 Problem of not selective trips for single-phase-to-ground faults During the protection testing the following two problems could be observed together with singlephase-to-ground faults on one of the busbars: the affected busbar was tripped with a delay time of about 70 ms additionally the not affected busbar was tripped too
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For other fault types this non-selectivity could not be observed. In the beginning this false behaviour could not be interpreted. After analysis of the fault recordings from the central unit of the protection it was obvious, that there was a wiring error in the Holmgreen-circuit within the coupling field. The terminals of the ground currents were connected wrong, so that the single-phase-to-ground fault currents over the coupling were interpreted wrong, which resulted in the false behaviour described above.
7 Advantages of a simulationbased test in addition to a parameter test The setting parameters of a protection relay are important and relevant for the function of a protection system. To verify that these values, calculated from the network calculation, work correctly within the protection relay and are set correctly, is the main task of a classical parameter test during commissioning. In a complex protection system, as within a busbar protection, these parameters are linked with a high number of logical functions, which makes the overall test of the whole system considerably more difficult. Therefore complex tables have to be made, where all the fault cases which have to be tested are described and where all the values to inject are calculated individually.
The network calculation within the software provides all the test quantities and using a complete setup with various test devices almost all substations can be tested. It could be shown, that smaller deviations, such as the wiring error described above, could not be found by a classical parameter test. If it is necessary to inject currents at three locations simultaneously, classical parameters tests are at its limits. For the utility NRM this was the first time to test a busbar protection in detail in the field. For the future it will be considered to apply this approach for every new commissioning.
Literature [1] Ziegler, G.: Numerical Differential Protection – Principles and Applications, Publicis Publishing, 2nd Edition, 2012 [2] ABB: Distributed busbar protection REB500 Operation Manual, 9th Edition (valid for software version V7.60), ABB, 2011
This process can take up to a whole week for a bigger substation and due to the numerous rewirings necessary and the manual calculation of the test quantities this is a huge effort and very prone to errors. RelaySimTest offers the possibility to automate this test. The effort to setup the test is quite high (see Figure 3), but if it is done correctly once, a complete system test can be conducted in a relatively short time, without the need to change the test setup.
Figure 10:
Simulation of an inside fault with RelaySimTest
Figure 11: © OMICRON 2015 – International Protection Testing Symposium
Figure 12:
Presentation 0.7
About the Authors Dipl.-Ing. (FH) Florian Fink was born 1983 in Bergisch Gladbach / Germany. He received his diploma in Electrical Power Engineering at the University of Applied Science in Cologne in 2009. From 2009 until 2012 he worked as project engineer for Cegelec / Germany and from 2012 to 2013 as planning engineer for InfraServ Knapsack / Germany. Since 2013 he is working for OMICRON electronics in product management as an application engineer for power system protection.
Dipl.-Ing. (FH) Jörg Köppel was born 1973 in Erzhausen / Germany. He studied Electrical Power Engineering at the University of Applied Science in Darmstadt / Germany, where he received his diploma in 1997. From 1997 until 2010 he worked for ABB Germany in the area of power system protection and control focused on busbar protection. Since 2010 he is working in project engineering for protection with a main focus on busbar protection.
Dipl.-Ing. Thomas Hensler was born in 1968 in Feldkirch / Austria. He received his diploma (Master’s Degree) in Computer Science at the Technical University of Vienna in 1995. He joined OMICRON electronics in 1995 where he worked in application software development in the field of testing solutions for protection and measurement systems. Additionally he is responsible for product management for application software for protection testing. Dipl.-Ing. Frank Trillenberg was born 1971 in Berlin. He studied Electrical Engineering at the Technical University in Berlin, where we received his diploma in 1999. From 1999 to 2010 he worked as a project engineer for Balfour Beatty Rail GmbH. Since 2010 he is working for Netzdienste Rhein-Main as a project and operations manager for secondary protection.
© OMICRON 2015 – International Protection Testing Symposium
