SG APPTC 2014 10 Paper 06 Presentation

New Age of Electric Energy System brings a New Set of Challenges for Protection and Automation

Hans-Joachim Herrmann, Siemens AG, Energy Automation Division, Germany

Development of numerical protec-tion and automation

The available technology has a big impacted on the development of protection and automation de-vices. The electromechanical technology was over some decades the dominated technology. The de-velopment of the transistor as well as low integrat-ed circuits lead to the analog static technology, where the operational amplifiers, the comparators and timer circuits were the main measuring ele-ments. The development of the microprocessor technology in 1971 was the basis of a very new design of protection and automation devices as well as automation systems. Software determines the functionality of the equipments and can be found in all application areas like protection, con-trol, measurement and metering. The processing of algorithms (e.g. modeling of the electric system) is the basis of the functionality.

Figure 1 gives an overview of the different technol-ogy and the principal design of the devices.

Fig. 1 Development of protection technology

The series production of numerical protection as well as bay controller devices started close to 1990. Before this time some pilot installation and the first devices went into operation. Figure 1 show clearly that the numerical technology is under con-stant improvement and development. Technology, manufacturing aspects (cost reduction) and stand-ardization influences the further development. A couple of important aspects will be discussed in the following chapters.

Intelligent and multifunctional bay units

Microprocessor evolution will be the defining tech-nology in future. The necessities for real time pro-cessing as well as severe environmental require-ments (e.g. EMC) lead furthermore to embedded devices. Further development of technology toward

higher processor performance (several 100 MHz are available), larger memory size and higher memory density (from Mega to Gigabytes), high resolution and fast analog/digital converters (e.g. 24-bit resolution) as well as the utilization of cus-tomer specific circuit technologies (e.g. FPGAs) are apparent. A further trend is the rapid develop-ing communication technology.

Due to the current as well as the new structures, the electrical power system will become even more heterogeneous, so that the classic interfaces such as binary in- and outputs as well as voltage, cur-rent and analog inputs will be still required espe-cially for refurbishments. A flexible and a modular hardware design meet the application require-ments. Figure 2 shows such a possible system. The basis housing is a so called base module (1/3 19”) which can be extent by expansion modules (1/6 19”). The robust and special designed housing increases the safety (excellent heat dissipation and EMC design avoids interference). Depending on the application different front plates for visualiza-tion are available. With such a modular design high degree of flexibility can be reached.

Fig. 2 Hardware kit – Modular hardware meets applica-tion requirement

With the introduction of the IEC61850 substation automation standard, the object oriented approach for the selection of protection and control technol-ogy started. Depending on the requirements, the desired functionality is selected and assigned to the relevant device. This leads to a further func-tional integration. Figure 3 shows a possible func-tional scope. There are no longer classical protec-tion and control devices. Future devices will be re-ferred to an IED (intelligent electronic device), a name introduced by IEC61850.

Presentation 6.1

© OMICRON – Asia-Pacific Protection & Testing Conference 2014

However functional integration does not mean that all functions shown in Figure 3 have to be always contained in one device. Depending on the appli-cation and the requirements, functionalities can be combined in different ways. When selecting a de-vice, the classic design criteria apply, such as the adherence to the n-1 principle. For protection ap-plications in the transmission networks, a main pro-tection 1 and a main protection 2 with different functional principles is required. This means for example the application of distance and line differ-ential protection.

Fig. 3 Overview functional integration

Flexible communication is a key feature

Introduction, Basic design

Flexibility in communication is one important re-quirement of modern IEDs. On the application side there is a requirement that different hardware inter-faces as well as protocols are supported. In sub-station automation Ethernet was adapted as the preferred communication medium several years ago; since then there has been constant develop-ments in network technologies yielding higher throughputs (from Mbit to Gbit). On the protocol side a large number of protocols must be support-ed. The install-base influences the decision of the users, so migration towards new protocols (e.g. IEC61850) is progressive.

There are two main communication streams: Communication of the IEDs with a substation au-tomation system or control centre and the commu-nication between the devices (e.g. line differential protection via protection communication interface or Goose-Communication between different IEDs) as well as communication with intelligent sensors

(process bus). These requirements influence the hardware design of the communication hard-ware/Interfaces and the handling of different proto-cols. Figure 4 gives an example for design of the communication interfaces in modern IEDs. Like a Laptop there are different plug-in modules with dif-ferent designs.

Fig. 4 Flexible communication via plug-in module and protocol selection during the engineering

Benefits of standard IEC 61850

IEC 61850 is more than a substation control proto-col. It comprehensively defines functions, data and the communication systems for communication in networks of the power supply industry. Edition 2 extends the influence of the standard to further branches of the power supply industry. Where the standard is at present still mostly being used as a classic substation control protocol, the new pro-cesses will in future be used at the communication and engineering level.

The dynamic reporting establishes itself in com-munication between Client and Server. Using a configuration file (ICD or SCD – file) or online, by establishing a connection to the server, the client is able to subscribe to all data points, which the serv-er can potentially publish. The Client can read spe-cific monitoring data, alarms or measured values of a Server for a certain period of time. It is customary to establish and transmit data records via fixed communication links today; however this will be re-placed by dynamic processes in the near future. Setting values of functions can also be changed via the protocol. With super ceding systems, set-ting values can be checked and adapted to the condition in the Smart Grid.

With the GOOSE – Message the IEC 61850 de-fines the interoperable communication between Servers in the network. Not only binary values can be exchanged, measured values can also be transmitted. GOOSE – Messages are also ex-changed between substations. New protection philosophies, which will require peer to peer com-munication across wide area networks, will be a reality. The GOOSE – Message will replace propri-etary point to point connections for signal compari-son or directional comparison, and facilitates the data exchange between devices of different manu-facturers, including between substations.

Developments in Network technology

Network components with a very high availability are a prerequisite for IP based protocols both with-

Presentation 6.2


in a substation and outside the substation. Today different forms of ring or star shaped network to-pologies and well as various methods to achieve redundancy are applied. These methods lack in-teroperability and will result in an interruption in the range between 30 ms to several hundred millisec-onds in the event of component failure. For critical applications such as the transfer of trip commands via GOOSE or the transfer of sampled measured values according to IEC 61850 9-2 for process bus applications these interruption intervals are not ac-ceptable. In the IEC 62439 ‘Highly Available Auto-mation Networks’ standard, now being adopted by IEC 61850 Edition 2 the High availability Seamless Redundancy Protocol (HSR) and the Parallel Re-dundancy Protocol (PRP) is described. It allows for interruption free switching (bumpless transfer) in the network with ring or star configurations. This technology will become established as standard for substation networks and process bus applications.

Furthermore there is a trend towards higher band-widths (from 100 MBit/s towards 1 GBit/s).

Cyber Security as Basis for secure operation of Networks

Because of the application of network technology the security within the network becomes a critical task. Security against internal threats and security against external attacks must be considered. Also in private networks it is possible that as a result of an accidental mal-operation the functioning of the network is placed at risk. The BDEW – Whitepaper [11] and NERC – CIP [12] address these topics. With IEC 62351 a standard is made available that describes methods for the end to end encryption as well as authentication between participants on the network in substation automation systems.

Development of electrical energy system The present changing in the primary system have a strong influence on protection and automation technology. Typical aspects will be discussed in the following pages.

The expected shortage of energy resources and the increasing environmental burden are a booster for a global change of thought in the field of energy politics. These changes of thought toward renewa-ble energy resources and new modes of usage have a deciding impact on the electrical-power-system. Electrical energy is developing into a de-ciding energy resource for the user.

Therefore a change is taking place in the naturally grown power system of the last decades, where energy production took place in close proximity to the user as well as according to user requirements, thereafter fed into the transmission network, and was then distributed. A structure of this kind is typi-cal for Central Europe.

The intention to effect a change is shown by the SMART GRID Initiative [1], [2], which deals with the new challenges regarding the individual voltage levels. The electrical power system is developing into a network, comparable to the Internet. The main difference to the Internet is the transmission of electrical energy instead of information. This constitutes an entirely different quality, as the bal-ance between production and use has to be main-tained. An imbalance necessarily leads to reduc-tion in the reliability of supply, which may result in local blackouts or supply shortages.

Alongside conventional power plants, renewable energy sources play a deciding role. They can however only be used where they are available. Considering the resource wind, it is available with certain constancy only close to shores and in the ocean. In the case of Offshore Windfarms, the en-ergy has to be transported on-shore and to the consumer. This makes a network expansion with combined transmission via cable and overhead line necessary, and possibly leads to an increase in DC current transmission, which requires intelligent en-ergy management. The deregulation and the trade with the commodity “electricity” result in a diverse power flows, which the systems have to control. Furthermore in the future there is a diversity of power producers. Producers may be found at all voltage levels, so that each network quasi as-sumes transmission tasks. In order for everything to work properly, intelligent control and monitoring solutions are essential. The protection and control technology makes a deciding contribution to this.

Figure 5 illustrates the contribution of renewable energy resources on consumption of electricity as well as the goal until the year 2020. Additional fig-ure 6 shows the distribution of the different renew-able resources [3].

Fig. 5 Development of renewable energy shares in Germany [3]

Presentation 6.3


Fig. 6 Distribution of renewable energy sources [3]

Especially the altered form of electrical energy generation has an essential impact on the automa-tion solutions as well as on protection. These as-pects are discussed in the paper.

Four main subjects are selected and the challeng-es are addressed in the following chapters.

Large distances between genera-tion and load centers

Transportation of power via long dis-tances

The energy system is growth organically in the last century. Close to the generation stations (e.g. thermal as well nuclear power plants) the large load centers are established. Due to strategy of shut down of conventional power stations (e.g. coal, nuclear) the balance between generation and load is changed. The wind energy Onshore as well as Offshore is mainly available in the northern re-gion of Germany. Due to this situation there is a new necessity of electrical energy transportation. One technical solution is the application of the pre-sent transmission routes and the substitution of an AC line through a DC line. Figure 7 shows a planed transmission route concept. The transmis-sion of DC and AC on the same tower is an un-known technical territory. The planed DC transmis-sion will have a length of 340 km and the transmit-ted power is designed with 2.2 GW [4]. The voltage level is ±400 kV.

Fig. 7 AC and DC system on the same tower

A lot experiences are available since years regard-ing protections concepts separately for both sys-tems. If AC and DC are on the same tower the challenge is the detection of intersystem faults. That means faults between the DC and AC sys-tem. Figure 8 describes the situation. The faulty segment of the AC line system must be switched off selectively, because there are a lot of intersec-tions in the AC system. Line length of the AC sys-tem is between 50 km and 100 km. The DC line has a total length of 340 km without any interrup-tions. The protection challenge comes from the fast tripping time (< 1ms) of the DC protection and the fast disconnection of the DC line. For the following question an answer must be found. Do we have a change to find the faulty section in the AC system? To answer this question new technical solutions are required as well as practical test for present ideas are necessary.

Fig. 8 Possible fault scenarios

Results of practical testes showed, that the inter-ference of the AC system because of the Corona effect (resistive coupling from DC to AC) is uncriti-cal. This interference can have an influence on power transformers. At dry weather condition the current which can be coupled into the AC system is approximately 1mA/km. At rainy weather this cur-rent will be then times higher [4].

Voltage stability problems

A further problem ensures due to the lack of power generation close to the load centers. The required reactive power must be delivered by other sources, which can be synchronous condensers, switched capacitor banks (MSCDN, VSC, reactors) and oth-ers. A 400-kV-AC-line with a length of 100 km and a transported load of 1400 MW requires a reactive power of 310 Mvar to guarantee a constant voltage of 400 kV. At a transmission limit of approximately 1800 MW the need for reactive power raises pro-gressive to 560 Mvar.

A missing reactive power generation leads to volt-age dips and can finally result in a voltage col-lapse. Figure 9 shows exemplary the actual volt-age shape for one day in a load center region. The rated voltage level is 400 kV.

Presentation 6.4


Fig. 9 Voltage shape in the Amprion region at one day [5]

Protection of capacitor banks

The voltage stability problem leads to an increased number of capacitor bank installations and the pro-tection gets more attention. In the past different devices are used for the protection tasks. With the modular devices design a high degree of flexibility can be reached and one device has the capability to protect a capacitor bank.

Typical protection functions for a capacitor bank are:

Overcurrent (OC) protection (50, 51, 50N, 51N)

The OC protection detects phase-to-phase or phase-to-ground short circuits and is mainly used as a backup function.

Differential protection (87)

The differential protection protects across the whole bank or sub-component against short cir-cuits within the installation. The function provides very fast and selective fault clearance.

Phase unbalance protection (46)

The phase unbalance protection will detect chang-es in the impedance of a phase. The function eval-uates the negative sequence current (I2).

Overload protection (49)

The overload protection monitors the thermal state of the capacitor, a coil or a resistor. Depending on the application requirements harmonics need to be considered. Typical requirements are the consid-eration of up to the 13th or 25th harmonic at SVC AC transmission systems and even up to the 50th harmonic at high-voltage direct current transmis-sion systems (on the AC side).

Capacitor peak overvoltage protection (59C)

The capacitor peak overvoltage function protects the capacitor-dielectric against too fast aging and even damage due to peak over-voltages. Voltage peaks caused by harmonics will also stress the ca-pacitor-dielectric. Consequently harmonics in the power system need to be considered by this func-tion. The peak voltage is obtained by the integra-tion of the phase current. The main reason is that a

current transformer damps harmonics much less than a voltage transformer.

Capacitor unbalance protection (60C)

The capacitor unbalance protection detects inter-nal faults of single C-elements within the capacitor. The specific function to be applied depends on the capacitor design. An operational unbalance current caused by tolerances, aging or environmental con-ditions shall be eliminated by compensation to in-crease the pickup sensitivity. Applying several un-balance overcurrent elements in parallel is stand-ard. A further application is the counting of single defective C-elements. Counter elements will also be applied in parallel with different counter thresh-olds for alarming, delayed tripping and fast tripping.

Circuit-breaker (CB) failure protection (50BF)

The CB failure protection function monitors the tripping of the CB and generates a backup trip sig-nal if the CB fails.

Circuit-breaker restrike protection (50RS)

A useful add-on is the restrike protection, which monitors the phase current regarding restriking af-ter CB pole separation. The probability of restriking increases at capacitors since a fully loaded capaci-tor causes a double voltage amplitude over a CB pole after the pole separation.

The design of a compact capacitor bank protection shows figure 10. The used functions are described by ANSI numbers. Main 1 and main 2 require-ments are fulfilled by duplicating the devices.

Fig. 10 Example: protection of a MSCDN [13]

Presentation 6.5


Supervision of the stability

The transmissible power of an overhead line has a limit which can by described with the PU character-istic (Nose curve). Such a curve shows figure 11. A critical situation for the voltage as well the risk of a voltage collapse exists at transmission lines with a heavy load. In such a case the actual operating point is right on the nose curve. If during heavy load a power plant is switch off due to a fault (see figure 11) two harmful effects can occur. The transmissible power in the resulting transmission line increases and operating point in the nose curve moves to right. The off power station doesn’t deliver the required active power and this leads to a new PU curve with a limited transmission capa-bility and finally to a risk of a voltage collapse. To avoid this control of load and generation fluctuation as well as the fast reactive power generation be-comes more and more important.

Fig. 11 Formation of a voltage collapse

The voltage as well as the power can be monitored with modern automation solutions and the PU curve can be evaluated. This is a possible applica-tion for the phasor measurement technology (PMU). On the load points the necessary data are measured very precise (GPS time synchronized) and transmitted to the evaluation center (e.g. SIG-URD PDC, [10]) which gives alarm and visualizes the actual load situation. Figure 12 illustrates such an evaluation.

Fig. 12 Nose curve evaluation with SIGUARD PDC [10]

The left side of the picture shows the location of phasor measurement units and the right side an example of a graphical analysis. The phasor

measurement function can be an add-on function in a protection or bay controller device and the measured values are transmitted via a local Ether-net infrastructure to the phasor data concentrator SIGUARD PDC.

Increased contribution from re-newable energy in generation

Due to the renewable energy generation the struc-ture of power generation is changed. Figure 13a shows the well known structure over one century. Synchronous generators supplies into the grid. The transient behavior during a fault is known (sub transient, transient and steady state fault current) and the protection devices consider this. For the fault clearing a sufficient fault current is available. The first step of changing came with windfarm and photovoltaic power stations. There is now a supply with converter stations. The power flow as well as the current during a fault depends on the design of the control function. The controller software con-siders grid requirements (e.g. fault ride through, contribution on voltage stability). Figure 13b illus-trates this changed situation. Due to the design of the converter station the short circuit current is lim-ited. The fault current is close to the rated current of the power station or can be smaller depending on the preload situation (less windfarms in ser-vice). In the case of a fault in the network the fault current contribution is much smaller compared with the conventional supply.

Due to the installation of Offshore windfarm there can be a very new situation which is shown in fig-ure 13c. There are AC sea cable connections be-tween the windfarms and the Offshore HVDC sta-tion. On both sides converter station are installed. In the case of a short circuit on the AC side the fault current is limited and can only reach values close to the rated current. This must be considered during design of the protection concept and the setting of the protection functions.

Fig. 13 Different network topologies

Presentation 6.6


With the installation of the converter station an ad-ditional question arises up.

Which fault current will be delivered in the case of an unsymmetrical fault?

In the grid code is the fault ride through behavior specified. So the interpretation of the injected fault current is not really clear. Let us assume the sup-ply situation according figure 13c. HVDC converter station delivers a positive as well as negative se-quence fault current in the case of an unsymmet-rical fault. In the specification for the design of the controller for windfarms only a supply of a positive sequence current is required and this is realized in practice [6]. The technical consequence is no fault current in the case of unsymmetrical faults. Without negative sequence impedance the current path according figure 14 is not closed. Figure 14 de-scribes a simplified replica in the symmetrical components for a phase to earth fault on the cable side. The zero sequence impedance comes from earthed Wye side of the power transformer. The positive sequence source of a converter station is a current source. In contrast at synchronous gen-erators this is a voltage source.

Without any fault current there is a limited or no re-action of the protection. The controller for windfarm must be adapted and negative sequence source impedance must be provided. This subject is dis-cussed in the technical paper [7].

Fig. 14 Symmetrical components for a phase to earth short circuit

Figure 15 shows a record from a real fault in a transmission network. The network configuration was according figure 14b. On the left side was a supply from a windfarm and a phase to earth fault occurs in the HV network. The fault was cleared by a distance protection (see figure 15). In the record a pure zero sequence current on the Wye side of the transformer is visible. This effect is well known as the “Bauch paradox”. The same record will be possible, if there is an open circuit (no supply) on the delta side of the transformer. As conclusion

there was no relevant fault contribution from the windfarm side, because no negative sequence im-pedance was available (compare with figure 14). Only a positive sequence current close to the rated current was supplied from the windfarm.

Fig. 15 Fault record of a single phase fault on a high voltage line

Changed network topology

Additional challenges come with the changed net-work topologies. One point was addressed in figure 13c. The connection of windfarm via sea cable to HVDC station is now a typical application. Due to the large cable capacitances shunt reactors for compensation are necessary. During switching of LC circuits transients occurs. To understand all the effects a lot of simulation were performed. An ex-cerpt of test results shows the following pictures in figure 16. Figure 16a gives an overview of the sim-plified replica. The first interesting effect visualizes figure 16b. The cable is energized from one side. Due to the shunt reactors an inrush occurs. But the large time constant as well the switching conditions lead to an inrush current with no zero crossing. In that case a delayed trip is necessary to avoid stress with the circuit breakers. This must be con-sidered during the engineering or special function-ality must be developed. The next interesting topic illustrates figure 16c. There was a phase to earth fault simulated in the cable. The fault curve with the short circuit current shows a typical trend. But the faultless phases are influenced too and a large DC offset is visible. The current in both faultless phases have for some cycles no zero crossing. That means a delayed trip of faultless phases is necessary. In the protection devices an extension is required.

A further discussed example shows a three phase fault current. During this test the controller was not optimal adapted. The consequence was a supply of a fault current with harmonics.

These harmonics must be tolerated by the protec-tion. Finally the reaction of the protection must be evaluated.

Presentation 6.7


a) Simplified replica

b) Inrush current curve

c) Phase to earth fault in the cable

d) Three phase fault without optimized control

Fig. 16 Simulation of different transient conditions

A total new situation occurs with the requirement from energy line extension act (from 2009) in Ger-many. With this act a transmission corridor with cable sections is required. That means there is now a series connection of overhead lines, cable section and overhead line which is called a hybrid system. This is a new situation for transmission line protection. Single phase to earth faults during thunderstorm are the most fault types. A temporary arc fault is cleared with an auto reclosing. But if a single fault occurs in the cable section an auto re-closing must be avoided.

Figure 17 shows the protection concept which is preferred in the German utility Amprion [8]. The transmitted power via the overhead line is approx-imately 1800 MW. The length of such cable section is between 3 and 10 km and in sum 12 cables are in parallel connected. That means 4 times 3phase single-conductor cable. The necessary area for such an implementation is 25 m.

For each three phase cable a separate differential protection plus an overall differential protection with an integrated distance protection is chosen. A signal for blocking the auto reclosing function is send to the overhead line protection (distance pro-tection) in the case of a fault in the cable.

A second challenge was the design of the power supply for the protection devices. Figure 17 illus-trates the basic concept. One source is the redun-

dant voltage transformer on which the rectifier equipment is connected. Another path is the sup-ply from a local 400-V-AC source.

Fig. 17 Protection concept for a hybrid transmission sys-tem [8]

Unpredictable load flow due to fluctuating generation

Due to the volatile network the load flow is not any more constant and can be close to the thermal lim-its. The maximum load influences the protection functions. This situation has for example an impact on the setting of overload, overcurrent as well as distance protection. For the overload protection the critical hot spot temperature must be considered in the thermal model. Therefore a distributed temper-ature measurement is necessary on transmission lines. For overcurrent protection applications a dy-namic setting adaption is possible. A new parame-ter set can be activated as a simple solution. The reset value of an overcurrent stage shall be 0.95 or higher.

One big advantage of the distance protection is the back-up functionality. In this context the possible operating distance of protection is the main dis-cussed subject. To avoid an overfunction the im-pedance characteristic has a load cut out (see fig-ure 18). Figure 18 shows the calculated limits for a typical German 400 kV transmission line [9]. From practical experiences a typical fault resistance of lower than 30 Ω was found. The minimum voltage is 0.85* 400 kV with a maximum angle of 37°. With this assumption the maximum load limit is 3730 A. The selected relay setting value considers an addi-tional safety margin which is also illustrated in fig-ure 14 (small circle).

The necessity of load cut out was also discussed in Northern America during the blackout analysis and is known under the name “Zone 3 problem” (dotted circle in figure 18).

The question is now: Is there any possibility to in-crease the load range?

As figure 18 shows there is the conflict between the maximum load range and sensitivity at high-resistance fault. Well known is the impedance measuring problem if there is a fault with a fault re-sistance and the fault current is supplied from two sources.

Presentation 6.8


To answer this question additional research work is necessary. One idea is the implementation of an adaptive characteristic. Another idea is the devel-opment of a new impedance measuring algorithm. This algorithm shall eliminate the resistive part and lead to a reduced setting in the R-direction.

Fig. 18 Impedance characteristic and load cut out

Summary and conclusion

The installation of renewable energy systems in Germany has a big impact on the electrical energy system. It influences the design as well as the op-eration of the primary system and has also an im-pact on protection and automation. In Germany there is now also the situation of large distances between generation and load centers. In this con-text a new concept for transmission of electrical energy was presented. AC and DC lines will be on one tower. This is a new design and the challenge for protection is the selectivity at intersystem faults.

Another addressed topic was the voltage stability. The necessary reactive power must be delivered from other resources such as synchronous con-densers, switched capacitor banks (MSCDN, VSC, reactors) and others. The protection of capacitor banks was shown. The phasor measurement tech-nology (PMU) is a possible method for voltage sta-bility supervision. If the limit of the nose curve is exceeded an alarm will be given.

With installation of renewable energy in generation the supply is realized by converter stations. This technology has limits in fault current contribution. In the case of a short circuit the supplied current is close to the rated current or sometime lower de-pending on the preload situation. The present technical realization follows the general require-ments of Grid code. For that reason only a sym-

metrical current is supplied. In the paper the situa-tion during unsymmetrical faults was discussed. The analysis showed the need for extension of the requirements. That means negative sequence im-pedance is required from renewable energy gen-eration.

With the installation of offshore windfarms a new network topology was discussed. It consists of windfarms with converter stations and an offshore HVDC station. The connection between both is re-alized via sea cable. In the paper transient phe-nomena are discussed during energization of the cable and short circuits. The possibility of currents without zero crossings must be considered in the design concept. The best solution is an intelligent tripping functionality in numerical devices. Another effect can be happen if the control system for the converter station is not correct adapted or compo-nents fail. During a fault in the cable a harmonic fault current can occur and that must be tolerated by the protection devices.

A further challenge for protection occurs if the transmission system becomes a hybrid system. Hybrid means the combination of overhead lines and short cable sections. A protection concept with available devices was presented.

The last addressed topic was the unpredictable load flow. That means the system reaches the thermal limits of primary equipments. This has an impact on new functions, like temperature meas-urement on overhead lines as well as the protec-tion concept. The distance protection is one main protection for overhead lines. One advantage is back-up functionality and in this regard the operat-ing distance of protection is a discussed subject. There is a conflict between the fault resistance (sensitivity) and the maximum possible load. The present technical solution is the load cut out in the impedance characteristic. Under discussion are new ideas like adaptive distance protection which considers the source impedance or new algorithm which eliminates the resistive part.

Smart grid influences the transmission grid and has an impact on protection and control. As shown in the introduction the numerical technology (flexi-ble hardware, powerful communication and modu-lar software structure) of modern intelligent elec-tronic devices (IED) is ready to fulfill the new chal-lenges. In some case only engineering work as well as testing is necessary. Other applications need additional investigation as well as research work to understand the new phenomena and to develop new additional functions or the modifica-tion of present functions. Summing up one can emphasize the following: To guarantee the system stability of Smart Grids additional investment in protection and control is necessary.

Presentation 6.9


Literature

[1] www.smartgrids.eu, see folder documents of interests.

[2] Electric Transmission and Distribution Program. Five year program plan (2008 – 2012) US Department of Energy, August 2006

[3] Development of renewable energy sources in Germany 2012 (version December 2013). Working group on Renewable Energy-Statistics (AGEE Stat)

[4] Rusek,J;Jürgens, I.; Braun, A. Kleinekorte, K. Joswig, R.: Technik für das Ultranet (Technology for the Ultranet), EW Jg. 112 (2013), Heft 3, S. 52-56

[5] Kamanenschikow, D.; Lösing, M.; Vennemann, K.: Spannungshaltung und Blindleistungsbereitstellung in hochaus-gelasteten 380-kV-Netzen (Voltage stability and reactive power supply in high loaded 380-kV networks), 11. ETG/GMA Fachtagung, 11.06-12.06.2013, München (Germany)

[6] BMU - Ordinance on System Services by Wind Energy Plants (System Service Ordinance – SDLWindV), Germany, 27.05.2009, http://www.bmub.bund.de/en/service/publications/downloads

[7] Erlich,I.; Schegner P.: Wind turbine negative sequence current control and its effect on power system protection. IEEE PES GM Vancouver 2013

[8] Wührmann, B.: Anforderungen an die Sekundärtechnik bei teilverkabelten EnLAG-Leitungen und einer HGÜ-Übertragung (Requirement on protection at hybrid systems (OHL + cable sections) and a HVDC-Trans-mission). Omicron User Conference 11.06 -13.06.2013, Ulm (Germany)

[9] Oechsle, F.; Kühn;H.; Föhring, H.; Hausschild, J.: Höherauslastung der Über-tragungsnetze. Gibt es Grenzen für das Distanzschutzprinzip? (Increased load in transmission networks. There are limits for distance protection) 7. ETG/FNN Tutorial „Schutz und Leittechnik“, 14.02.-15.02. 2012, Mainz (Germany); www.schutz-leittechnik.de

[10] Wache, M.: Monitoring-System mit Synchron-zeigern (Monitoring system with synchronous phasor). 8. ETG/FNN Tutorial „Schutz und Leittechnik“, 05.02.-06.02. 2014, Düsseldorf (Germany); www.schutz-leittechnik.de

[11] White Paper – Requirements for Secure Control and Telecommunication Systems”, BDEW, June 2008, Version 1

[12] CIP–002–1 through CIP–009–1, “Critical Infrastructure Protection (CIP) Cyber Security Standards”, NERC¸ June 2006,

[13] SIPROTEC 5 Overcurrent Protection 7SJ82/ 7SJ85 V5.00 , Siemens AG, Device manual C53000-G5040-C017-4

About the Author

Hans-Joachim Herrmann stud-ied electrical engineering and electronics on Technical Universi-ty of Dresden. From 1977 to 1991 he was an assistant professor on the Technical University of Zittau in the relay protection depart-ment. During this time he wrote

two theses with the subject “Algorithms of line pro-tection” (1984 Dr-Ing.) and “Protection and meas-uring technique” (1991 Dr.-Ing. habil.). In 1991 he joined Siemens as a member of the product man-agement protection in energy automation division. He is a principal key expert protection and was in-volved in all developments of the numerical SI-PROTEC devices. He did a lot of trainings in nu-merical protection with main topics transformer and generator protection. In 1997 he published a book with the title “Numerical Protection” (in German) and in his carrier more than 90 contributions on conferences and technical papers. From 2004 to 2012 he was the chairman of German national SC B5 (protection and automation) CIGRE committee and a member of different working groups (relay testing, transformer and generator protection, pro-tection requirements on transient response of volt-age and current digital acquisition chain (process bus)).

Presentation 6.10


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rest

rict

ed ©

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s A

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013

All

rig

hts

res

erve

d.

An

swer

s fo

r in

fras

tru

ctu

re a

nd

cit

ies.

New

Ag

e o

f E

lect

ric

En

erg

y S

yste

m

bri

ng

s a

New

Set

of

Ch

alle

ng

es f

or

Pro

tect

ion

an

d A

uto

mat

ion

Pre

sent

er: H

ans-

Joac

him

Her

rman

n, G

erm

any

/ 15-

16 O

ctob

er 2

014

2014

Oct

ober

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16

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ed ©

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hts

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erve

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Pag

e 2

Dr.

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. Her

rman

n / I

C S

G E

A P

RO

Tab

le o

f C

on

ten

t

R

evie

w o

f d

evel

op

men

t in

P

rote

ctio

n

T

ec

hn

olo

gy

of

IED

s

C

han

ge

of

En

erg

y S

yste

m

C

hal

len

ges

an

d S

olu

tio

n f

or

Pro

tect

ion

an

d C

on

tro

l

A

C a

nd D

C o

n on

e to

wer

V

olta

ge s

tabi

lity

(rea

ctiv

e po

wer

)

Sho

rt c

ircui

ts w

ith n

ew g

ener

atio

n so

urce

s; t

rans

ient

s

Com

bina

tion

of o

verh

ead

line

&

cabl

es

Influ

ence

of

tem

pora

ry o

verlo

ad

S

um

mar

y, C

on

clu

sio

n

2014

Oct

ober

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e 3

Dr.

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rman

n / I

C S

G E

A P

RO

Dev

elo

pm

ent

in P

rote

ctio

n

Mic

ropr

oces

sor

tech

nolo

gy c

hang

ed th

e w

orld

of P

rote

ctio

n an

d A

utom

atio

nM

ultif

unct

ion

devi

ces

with

pow

erfu

l com

mun

icat

ion

are

stat

e of

the

art

Ava

ilabl

e te

chno

logy

has

an

impa

ct o

n pr

otec

tion

and

auto

mat

ion

devi

ces

2014

Oct

ober

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16

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Pag

e 4

Dr.

H-J

. Her

rman

n / I

C S

G E

A P

RO

Tec

hn

olo

gy:

Sta

te o

f th

e A

rtM

od

ern

Inte

llig

ent

Ele

ctro

nic

Dev

ices

(IE

Ds)

M

icro

proc

esso

r ba

sed

devi

ces

with

pow

erfu

l com

mun

icat

ion

are

stat

e of

the

art

T

his

tech

nolo

gy is

rea

dy f

or t

he n

ew r

equi

rem

ents

Mo

du

lari

ty i

n c

om

mu

nic

atio

ndi

ffere

nt p

lug-

in m

odul

es,

prot

ocol

s M

od

ula

r h

ard

war

eF

lexi

ble

conf

igur

atio

n (I

Os)

Mo

du

lari

ty o

f F

un

ctio

ns

Acc

ordi

ng to

the

appl

icat

ion

the

nece

ssar

yfu

nctio

ns c

an b

e as

sign

ed to

the

dev

ice

durin

g th

e en

gine

erin

g pr

oces

s

SIP

RO

TE

C

DIG

SI

67

21

63

40

79

27

51

N4

9

81

87

T

32

R2

16

7G

87

N5

1

40

79

59

51

N6

4

63

…3

7

51

V

64

R4

9

67

87

L5

1G

49

T

79

50

N5

02

7

63

50

24

86

81

81

50

50

21

87

50

…

Dev

ice

Eng

inee

ring

Tool

Presentation 6.11


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hts

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erve

d.

Pag

e 5

Dr.

H-J

. Her

rman

n / I

C S

G E

A P

RO

Ch

ang

e o

f E

lect

ric

En

erg

y S

yste

m h

as a

big

Im

pac

t o

n P

rote

ctio

n a

nd

Au

tom

atio

n

Sho

rtag

e of

ene

rgy

reso

urce

s an

d th

e in

crea

sing

env

ironm

enta

l bur

den

are

a bo

oste

r fo

r a

glob

al c

hang

e of

tho

ught

in th

e fie

ld o

f en

ergy

pol

itics

.

Exa

mpl

e: O

ffsh

ore

Win

d F

arm

&

HV

DC

Tra

nsm

issi

on

2014

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ober

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16

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hts

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erve

d.

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e 6

Dr.

H-J

. Her

rman

n / I

C S

G E

A P

RO

Ch

ang

e o

f E

lect

rica

l En

erg

y S

yste

mIn

flu

ence

on

Pro

tect

ion

an

d A

uto

mat

ion

Lar

ge

dis

tan

ce b

etw

een

Gen

erat

ion

an

d L

oad

Cen

ters

N

ew s

olut

ions

for

ener

gy t

rans

port

(ov

erla

y ne

twor

k, u

ltran

et)

P

rote

ctio

n c

on

cep

ts

Rea

ctiv

e po

wer

pro

blem

s (v

olta

ge s

tabi

lity)

S

up

ervi

sio

n v

ia P

MU

s

Incr

ease

d C

on

trib

uti

on

fro

m R

ene

wab

le E

ner

gy

in G

ener

atio

n

Incr

ease

d nu

mbe

r of

con

vert

er s

tatio

ns

Sm

all s

ho

rt c

ircu

it c

urr

ents

F

luct

uatin

g ge

nera

tion

Wid

e ra

ng

e o

f fa

ult

cu

rren

ts

Ch

ang

ed N

etw

ork

To

po

log

y

Tapp

ed li

nes;

Sea

cab

les

betw

een

stat

ions

(ch

argi

ng c

apac

itanc

es)

N

ew t

ran

sien

t ef

fect

s

Com

bina

tion

of o

verh

ead

lines

and

sho

rt c

able

s

Pro

tect

ion

co

nce

pts

Un

pre

dic

tab

le L

oad

Flo

w d

ue

to F

luct

uat

ing

Gen

erat

ion

O

verlo

ad p

robl

ems

(set

ting

of p

rote

ctio

n)

Ad

apti

ve p

rote

ctio

n

Sou

rce:

Sie

men

s pa

per

2013

-07

2014

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Dr.

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n / I

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G E

A P

RO

Ove

rlay

Net

wo

rk –

AC

/DC

on

th

e S

ame

To

wer

Infl

uen

ce o

n t

he

Pro

tect

ion

DC

-Sys

tem

±40

0 kV

AC

380

kV

AC

110

kV

+

-k

HV

DC

: ±

400

kVP

ower

: 2,

2 G

W; L

engt

h: 3

40 k

m

AC

110

kVU

ltran

etbe

twee

n A

mpr

ion

and

Tra

nsne

t BW

Cor

ona

effe

ct :

nonc

ritic

al in

fluen

ce o

f ohm

icco

uplin

g fr

om D

C to

AC

for

tran

sfor

mer

s

Test

res

ults

: dry

wea

ther

: 1m

A/k

m, r

ainy

10m

A/k

m

Inte

rsys

tem

fau

lts

(AC

/DC

)

Ver

y fa

st f

ault

clea

ring

via

DC

pro

tect

ion

D

etec

tion

on th

e A

C-s

ide

?

Avo

id th

e ris

k of

an

over

fun

ctio

n

Inve

stig

atio

ns

are

nec

essa

ry

2014

Oct

ober

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16

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hts

res

erve

d.

Pag

e 8

Dr.

H-J

. Her

rman

n / I

C S

G E

A P

RO

Lar

ge

Dis

tan

ce -

Gen

erat

ion

an

d L

oad

Cen

ters

R

eact

ive

Po

wer

Su

pp

ly -

Vo

ltag

e S

tab

ility

Pro

ble

ms

Pla

ce o

f ge

nera

tion

and

load

flow

in

fluen

ces

the

volta

ge b

and

385

kV

Ove

rhea

d lin

e: D

eman

d of

Q =

f(P

)e.

g.:

380

kV

(11

0 km

);n-

0: 1

400

MW

, 300

Mva

r;

n-1:

180

0 M

W, 5

50 M

var

Rea

ctiv

e po

wer

sup

port

is n

eces

sary

(Gen

erat

ors,

MS

CD

N, V

SC

,..)

422

kV

Pro

tect

ion

of a

Cap

acito

r B

ank

Mod

ern

IED

incl

udes

al

l nec

essa

ry f

unct

ions

7SJ8

5BB

QA1

MP

I-3p

h 1

FG

Cap

.ban

k 1

I-3ph

V-3p

h

50

FG

CB

I-3ph

MP

I-3p

h 2

MP

I-3p

h 5

60C

4950

N 3759

C

50BF

Ctrl

MP

I-3p

h 3

BI BOM

P I-

3ph

4

MP

I-3p

h 6

MP

I-3p

h 7

FG

Sid

e

I-3ph

46

FG

Diff

.pro

t.

87

FG

U/I

3ph

I-3ph

∑++

FG

U/I

3ph

I-3ph

∑+-

50 49

1)

CB

MP

V-3

ph 1

59

Res

trike

50

I-unb

al.

FG

Ca

p.ba

nk 2

I-3ph

V-3p

h

60C

59C

I-unb

al.

49

Presentation 6.12


2014

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rict

ed ©

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hts

res

erve

d.

Pag

e 9

Dr.

H-J

. Her

rman

n / I

C S

G E

A P

RO

Rea

ctiv

e P

ow

er S

up

ply

–S

ynch

ron

ou

s C

on

den

ser

Op

erat

ion

of

a G

ener

ato

r in

a N

ucl

ear

Po

wer

Pla

nt

Nuc

lear

pow

er p

lant

was

shu

t do

wn

1500

MV

A g

ener

ator

del

iver

s no

w t

he n

eces

sary

rea

ctiv

e po

wer

(sy

nchr

onou

s co

nden

ser)

Syn

chro

nous

Gen

erat

or(M

otor

ope

ratio

n)

Ope

ratin

g ra

nge:

-40

0Mva

r (u

nder

exc

ited)

+ 9

00M

var

(ove

r ex

cite

d)

Dyn

amic

rea

ctio

n d

uri

ng

a r

eal

even

t

Sys

tem

vol

tage

Sys

tem

dis

turb

ance

in T

urk

ey

Rea

ctiv

e po

wer

infe

edvi

a th

e sy

nchr

onou

s co

nden

ser

Fas

t rea

ctio

n of

the

sync

hron

ous

cond

ense

r an

d st

abili

zatio

n of

the

volta

ge

2014

Oct

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hts

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Pag

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Dr.

H-J

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n / I

C S

G E

A P

RO

Lar

ge

Dis

tan

ce -

Gen

erat

ion

an

d L

oad

Cen

ters

R

eact

ive

Po

wer

Su

pp

ly -

Vo

ltag

e S

tab

ility

Pro

ble

ms

PM

U p

art o

f mod

ern

IED

s M

onito

ring

with

SIG

UA

RD

PD

P(P

DP

: P

haso

r D

ata

Pro

cess

ing)

Sup

ervi

sion

of t

he

Nos

e (P

U)

Cur

veN

ET

OLT

C

Load

GP

Pla

nt;Q

Pla

nt

PN

et;Q

Net

Tran

sfor

mer

tapp

ing

Ope

ratin

g po

int

befo

re th

e e

vent

No

sta

ble

ope

ratin

g p

oint

afte

r th

e e

vent

PP

lant

Act

ive

Po

we

rP

Net

volta

ge

PU

cur

ve

befo

re th

e ev

ent

PU

cur

ve

afte

r th

e e

vent

2014

Oct

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Dr.

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RO

Co

nve

rter

Sta

tio

n -

Fau

lt C

urr

ents

Wh

ich

fau

lt c

urr

ent

is s

een

by

the

pro

tect

ion

?

Co

nve

rter

sup

ply

fro

m o

ne

sid

eF

ault

curr

ent

will

be

deliv

ered

by

the

sync

hron

ous

gene

rato

rs;

limite

d fa

ult

curr

ent

(app

.1*

I rat

edor

Ipr

eloa

d) c

omes

e.

g. f

rom

the

win

d fa

rm

Co

nve

rter

sup

ply

fro

m b

oth

sid

esF

ault

curr

ent

is li

mite

d fr

om b

oth

side

s (a

pp.

1*I r

ated

or lo

wer

)

Cri

tica

l ar

e u

nsy

mm

etri

cal

fau

lts:

SD

LWin

dV

: re

quire

s re

activ

e po

wer

(p

ositi

ve s

yste

m)

+ f

ault

ride

thro

ugh

supp

ort

HV

DC

: F

ault

curr

ent

of 1

* I r

ated

with

a

posi

tive

and

nega

tive

syst

em im

peda

nce

Co

nve

nti

on

al s

up

ply

Suf

ficie

nt f

ault

curr

ent

will

be

deliv

ered

for

al

l fau

lts v

ia t

he s

ynch

rono

us g

ener

ator

s

2014

Oct

ober

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hts

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Pag

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Dr.

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n / I

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G E

A P

RO

Co

nve

rter

Sta

tio

n -

Fau

lt C

urr

ents

W

hic

h f

ault

cu

rren

t is

see

n b

y th

e p

rote

ctio

n?

Pre

sent

des

ign

of t

he c

ontr

ol:

Con

vert

ers

supp

ly a

pos

itive

seq

uenc

e cu

rren

t (S

DLW

indV

)

Wit

ho

ut

neg

ativ

e se

qu

ence

imp

edan

ce

and/

or c

onve

rter

impe

danc

e th

ere

is n

o sh

ort-

circ

uit

curr

ent

–ev

en if

all

tran

sfor

mer

sta

r po

ints

are

ear

thed

T

he

con

tro

l sy

stem

of

con

vert

ers

mu

st b

e ad

apte

d if

nec

essa

ry.

A n

egat

ive

seq

uen

ce s

ou

rce

imp

edan

ce is

req

uir

ed.

P

rote

ctio

n b

ehav

ior

mu

st b

e ev

alu

ated

(si

mu

lati

on

+ t

est)

L1-

E

No

neg

ativ

e se

qu

ence

cu

rren

t I2

Presentation 6.13


2014

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hts

res

erve

d.

Pag

e 13

Dr.

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n / I

C S

G E

A P

RO

Co

nve

rter

Sta

tio

n -

Fau

lt C

urr

ents

Pra

ctic

al f

ault

cas

e

Pha

se t

o ea

rth

faul

t on

the

OH

L

curr

ent vo

ltage

Zer

o s

equ

ence

cu

rren

t is

onl

y de

liver

ed f

rom

the

tra

nsfo

rmer

No

faul

t cu

rren

t co

ntrib

utio

n fr

om t

he w

ind

farm

21 Z<

2014

Oct

ober

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hts

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erve

d.

Pag

e 14

Dr.

H-J

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rman

n / I

C S

G E

A P

RO

Ch

ang

ed N

etw

ork

To

po

log

yS

ea C

able

Ap

plic

atio

n i

n O

ffsh

ore

Win

d F

arm

s

Thi

s co

nfig

urat

ion

lead

s to

tr

ansi

ents

Clo

sin

g t

he

CB

fro

m o

ne

sid

e:In

rush

cur

rent

with

NO

zer

o cr

ossi

ng

de

laye

d tr

ip n

eces

sary

to

avoi

d st

ress

with

the

CB

Fau

lt c

urr

ent

is n

ot

sin

uso

idal

:D

epen

ding

on

desi

gn o

f th

e co

ntro

l ha

rmon

ics

may

be

poss

ible

re

actio

n of

the

pro

tect

ion

mus

t be

eva

luat

ed

1-p

has

e fa

ult

in

th

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trip

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2014

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ober

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e 15

Dr.

H-J

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15-

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Sie

men

s A

G 2

014

All

rig

hts

res

erve

d.

Pag

e 16

Dr.

H-J

. Her

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n / I

C S

G E

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sure

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< 3

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kV

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arac

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Impr

ovem

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of t

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ista

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prot

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cess

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Presentation 6.14


2014

Oct

ober

15-

16

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rest

rict

ed ©

Sie

men

s A

G 2

014

All

rig

hts

res

erve

d.

Pag

e 17

Dr.

H-J

. Her

rman

n / I

C S

G E

A P

RO

Su

mm

ary,

Co

ncl

usi

on

S

mar

t G

rid in

fluen

ces

the

tran

smis

sion

grid

and

has

add

ition

al in

fluen

ce o

n pr

otec

tion

and

cont

rol.

T

he p

rese

nt t

echn

olog

y (h

ardw

are,

com

mun

icat

ion

and

softw

are

stru

ctur

e) o

f IE

Ds

is r

eady

to

fulfi

ll th

e ne

w c

halle

nges

.

In

som

e ap

plic

atio

ns th

e pr

esen

t te

chno

logy

/ de

vice

s ca

n be

use

d. O

nly

engi

neer

ing

wor

k is

req

uire

d (e

.g.

over

head

line

–ca

ble

com

bina

tion)

.

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ther

app

licat

ions

nee

d ad

ditio

nal i

nves

tigat

ion/

res

earc

h w

ork

to u

nder

stan

d th

e ne

w p

heno

men

a, t

o de

velo

p ad

ditio

nal f

unct

iona

lity

or m

odify

pre

sent

fu

nctio

ns.

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or s

elec

tive

oper

atio

n th

e pr

otec

tion

need

s fa

ult c

urre

nts.

To

impr

ove

the

cont

rol o

f co

nver

ters

as

wel

l the

pro

tect

ion

sim

ulat

ions

and

tes

ts a

re n

eces

sary

.

To g

uar

ante

e th

e sy

stem

sta

bili

ty o

f S

mar

t G

rid

s ad

dit

ion

al

inve

stm

ent

in p

rote

ctio

n a

nd

co

ntr

ol

is n

eces

sary

.

Presentation 6.15
