Instrumentation, Controls & Electrical / Technical Description / February 2016

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1 / Technical Description / February 2016 SPPA-E3000 Static Excitation Systems (SES) Static excitation systems for excitation and voltage regulation of synchronous machines Answers for energy.

2 Table of contents 1. Introduction Basic circuit Basic Module (mech. design) Equipment scope Method of operation Automatic voltage regulator Field current regulator Other modes Tracking control Excitation limiter Power system stabilizer (PSS) Control Software Application Technical specifications Abbreviations Unrestricted Siemens AG All rights reserved

3 1. Introduction The SPPA-E3000 SES type THYRIPOL (SPPA Siemens Power Plant Automation) is a static excitation system that is suitable for every type of synchronous generator or synchronous compensator. It is suitable for use in hydro, steam, or gas power plants. It is easily adapted to the conditions in the plant, making it optimally suitable for both new plants and modernization of existing plants. Numerous flexible, project-specific adaptations are possible to take account of the technical conditions when modernizing plants. This document describes the SES static excitation system for rated field currents up to 2000 A and provides information on the optional load-dependent variant THYRIPOL -L. It is only possible to provide a rough idea of the large number of auxiliary equipment items and options that can be supplied for plant-specific designs. The essential operating characteristics of the THYRIPOL -S excitation system are: High level of safety Great availability Easy adaptability Low maintenance requirement Fast response Good closed-loop control characteristics Robust design Fig. 1: Example: THYRIPOL cubicle group Fig. 1: Example of the THYRIPOL -S static excitation system A voltage regulator based completely on digital technology controls the excitation of the synchronous machine directly through a thyristor converter. The voltage regulator contains a powerful microprocessor, which takes care of both voltage regulation and all important limiting and monitoring functions in the excitation system as well as generating the delay angle for the converter. A high level of availability is achieved with the use of tried and tested industrial components. The consistently modular design pays off in the extremely easy operation and service. A short description of the basic modules of the basic circuit and a detailed account of the scope of devices and components and how they work are provided below. 3 Unrestricted Siemens AG All rights reserved

4 2. Basic circuit Excitation transformer (1) On the primary side, the converter transformer is connected to the terminals of the synchronous machine and is used as a power source for the field-circuit rectifier. The converter transformer can optionally be connected to the medium-voltage system of the power plant auxiliary power supply. Thyristor converter (2) The thyristor converter consists of a fully controlled compact converter. De-excitation device (3), (4), (5) The de-excitation device consists of the field circuit breaker (3) on the supply side (optionally also output side) of the thyristor converter, combined with the overvoltage protection SICROWBAR (4) and the field discharge resistor (5) Overvoltage protection (4) The crowbar overvoltage protection is connected directly to the DC output of the thyristor converter and prevents any overvoltages that may arise from faults in the synchronous machine. Open- and Close-Loop control (6), (7) The controller consists of the voltage regulator (6) for regulating the generator terminal voltage and the independent manual regulator (7) for regulating the field current Both regulators are implemented in a powerful module, which also performs all higher-level control, monitoring, and communication tasks. Trigger set (8) The trigger set function and monitoring near to the converter are performed by a SINAMICS DC-MASTER compact station series 6RA80 for converter powers up to approx. 2,000 A. Excitation build-up (9) There is also a field-flashing circuit (9) as an auxiliary item of equipment, which initiates targeted excitation build-up independently of the remanent voltage of the synchronous machine SG 3~ Fig. 2: Basic circuit of the static excitation system THYRIPOL 4 Unrestricted Siemens AG All rights reserved

5 3. Basic Module (mech. design) The THYRIPOL -S excitation system is installed in a standard cubicle group, which is specially designed for the use of electronic closed- and open-loop control systems in conjunction with power electronics. A modular design and easily accessibility of all components simplify handling of all functions and optimization equipment. The dimensions of the standard cubicle group are 1600 mm wide, 2200 mm high, and 600 mm deep. The easy adaptation to the needs of the plant and, especially conversions in existing plants, can result in deviations from the above dimensions. Open- and closed-loop control cubicle This cubicle (Fig. 3) groups together all open- and closed-loop control equipment of the excitation system and controls for local operation. These include the measuring transducers for voltage and current, the voltage regulator, the field current regulator, the current limiting controller, optional local control unit, and, if optionally included, additional control, monitoring, or protection equipment. The same cubicle also contains all power supply modules for the regulators and trigger sets mentioned above. It also encloses the electronic control equipment, the contactors, protective circuit breakers, measuring and auxiliary relays and matching transformers for connecting the auxiliary voltage. Redundant SIMOTION D435-2 regulator module The core components of the open- and closed-loop control cubicle are the SIMOTION D435-2 modules with analog/binary input/output and communication modules. All these components are used in standard industrial equipment in use all over the world, ensuring great robustness and high availability. The following functions are implemented on the SIMOTION D435-2: Closed-loop control (see Chapter 5.1) Limitations (see Chapter 5.5) Power system stabilizer (PSS, see Chapter 5.6) Internal control and monitoring of the plant Communication with the I&C Operator control and monitoring Redundant current and voltage actual-value sensing Fig. 3: Redundantly designed regulator cubicle 5 Unrestricted Siemens AG All rights reserved

6 SIMOTION D435-2 Control Unit. Programmable controller: Interfaces: 8 DI, 8 DI/DO 4 DRIVE-CLiQ 2 Profibus 2 Ethernet 2 USB 1 option slot Number of IOs that can be configured Freely programmable IO modules Available as digital and analog inputs/outputs Fig. 4: SIMOTION D435-2 processor module Fig. 5: Interface modules (example: TM15 / TM30) This I/O component acquires, converts, and transmits the control actual values. Accuracy: 0.5% Resolution: 14 bits Sampling rate: 100 µs 2 additional process inputs: 0..20mA and 0..10V Voltage inputs (3-phase): 100/110/120 V Current inputs (2-phase or 3-phase): 1/5A Fig. 6: SIMOTION D435-2 processor module The interaction between the core components is schematically illustrated in Fig. 15 for a 2-channel fully redundant voltage regulator (2 automatic / 2 manual channels). 6 Unrestricted Siemens AG All rights reserved

7 4.Equipment scope Excitation transformer A converter transformer, e.g. of the cast-resin type GEAFOL, is provided to supply the excitation system with power. The GEAFOL design avoids the restrictions of liquid-filled transformers while benefiting from their advantages, such as reliability and a long life. The transformers are designed for installation in a metal or masonry transformer cell and for equipment with: Temperature monitoring for alarm and tripping Cable connection to the high voltage and low voltage side The cast-resin insulation enables maintenance-free operation of the transformer. This also makes the winding moisture-resistant and tropic-proof, as well as self-extinguishing. The transformer has an aluminum winding. This has a very similar coefficient of thermal expansion to the cast resin. This design also provides a high level of electrical safety and resistance to high-voltage pulses. The following options are possible: Design of the converter transformer as an oil-immersed transformer as is suitable for the installation conditions Transformer enclosure with / without connections to the generator leads Design with 3 single-phase converter transformers with segregated generator leads Fig. 7: Example: cast-resin converter transformer 7 Unrestricted Siemens AG All rights reserved

8 Thyristor converter Depending on the redundancy requirements, the thyristor converter comprises one or two adjacent cubicles with the power thyristors, the associated heat sinks, arm-circuit fuses, monitoring equipment and the triggering units for the thyristors. The thyristor converter is designed as a fully controlled 6-pulse three-phase bridge circuit, which receives power from a converter transformer. As shown in Fig. 9, any value between the two limits for the ceiling voltage U p and the maximum negative field voltage U fu can be reached practically without delay with the converter. Fig. 8: SINAMICS DCM The largest negative field voltage U fu is reached at approx. 80% of the ceiling voltage U p, considering a safety distance from the limit of inverter stability. This permits extraordinarily fast elimination of the field current I f to zero. That is particularly useful on load rejection when power-frequency overvoltages have to be reduced. The diagram under the basic circuit (Fig. 9) shows the field voltage U f and the field current I f, versus time when control switches to full overexcitation at instant t 1 and control switches to full inverter operation at instant t 2. As of t 3, the field current has decayed and inverter operation can be terminated. The maximum rate of change of the field current depends on the two limits and the time constant in the field circuit of the synchronous machine. The time constant depends on the load condition of the synchronous machine. For the ceiling voltage, minimum values are prescribed in the standards, but these are often exceeded to take account of special requirements for control response. By connecting inverters in parallel, it is possible to implement redundancy (2x100%) for load distribution among the converter bridges. High-breaking-capacity semiconductor fuses protect the thyristors in the event of short-circuits on the DC or three-phase side. Thyristors that have become defective due to a fault are isolated by the semiconductor fuse so that operation with the remaining parallel arms can continue under nominal conditions without interrupting operation. Protection from overvoltages is achieved by using high-blocking capability thyristors. Series connection is usually unnecessary because of the high off-state voltages of modern thyristors. As a special use case, a diode converter (B6) can be connected in series with the fully controlled three-phase thyristor converter (B6C). The diode converter is fed from a transformer-reactor, which provides a voltage that is proportional to the generator stator current. This enables generator-load-dependent support of the field current and makes for a highly dynamic control response to support the generator voltage on load changes and on shortcircuits in the power system. This option is designated THYRIPOL -L excitation system. (L: load-dependent) Fig. 9: 6-pulse thyristor converter bridge To dissipate the heat of the converter losses, redundant radial fans are provided as a built-on element on top of the converter cubicles. If SIMOREG compact units are used, a powerful fan is integrated into each device. A redundant fan design is also possible as an option. 8 Unrestricted Siemens AG All rights reserved

9 Overvoltage protection If the field winding of a synchronous machine is connected to a controlled or uncontrolled converter, overvoltages cannot be prevented without special protection measures. These overvoltages can arise due to injected currents, which are transferred to the field circuit when operational faults occur on the three-phase side of the synchronous machine. They can also occur on switching operations in the three-phase supply circuit of the excitation system. The excitation system is therefore equipped with a crowbar surge suppressor. This uses anti-parallel connected thyristors, which are parallel to the field winding of the synchronous machine and to the converter output. In the event of a fault, these thyristors in the surge suppressor are fired via a BOD (break-over diode) element. They are able to carry high current for a short time and at the same time to limit the voltage in order to prevent impermissible voltage loads on the converter and the rotor. The firing voltage of the BOD element is below the maximum permissible repetitive peak off-state voltage (URRM) of the converter thyristors. (see Fig. 12) A monitoring device signals that the surge suppressor has responded to protect the generator. Fig. 10: Example: SICROWBAR surge suppressor (overvoltage protection), type 7VV3003 De-excitation device The de-excitation device must ensure de-excitation of the synchronous machine independently of the control of the excitation system. This includes reliable interruption between the excitation power source (converter transformer) and the field winding of the generator. The THYRIPOL excitation system therefore has an incoming circuit breaker on the three-phase side of the field-circuit rectifier, which disconnects the converter and therefore the field of the generator from the converter transformer in 3 poles. Alternatively, the DC side can also be disconnected by a field circuit breaker instead of disconnection on the three-phase side. In any case, the field circuit of the generator must remain closed because otherwise high overvoltages occur. For this purpose, the crowbar is actively fired with the de-excitation command, such as protective de-excitation, and the field discharge resistor in the field circuit is switched on. The excitation energy is decreased in this together with the field winding. This resistor also determines the de-excitation time and, because the current is loadindependent, the voltage applied to the field winding and the thyristors of the converter. 1 Field winding 2 Field discharge resistor 3 Overvoltage protection 4 Rectifier 5 AC-Field circuit breaker Fig. 11: Schematic view of the de-excitation device Three-phase supply Sequence: Firing pulse blocked AC-fieldcircuit breaker opened and reduction of energy in field winding via the field discharge resistor 9 Unrestricted Siemens AG All rights reserved

10 As standard, the field discharge resistor is implemented as a cast-iron resistor with a linear current-voltage characteristic. In special cases and as an option, a resistor with a non-linear current-voltage characteristics can be connected instead of the linear field discharge resistor. To increase safety and to permit operational de-excitation, control of the converter into inverter mode is also provided (see Fig. 12). In this case, the negative voltage -0.8 x U fd is applied to the field winding of the generator as a negative field voltage. In this case, the thyristor bridge functions in inverter mode with α = 150 el and reduces the field current to zero within a short time. The de-excitation time is largely determined by the magnitude of the negative field voltage. Gate control voltage of the BOD element Protection range U RRM U fd U fn repetitive peak off-state voltage ceiling voltage rated field voltage Operation with ceiling voltage Rated-load operation UfN Operation with neg. ceiling voltage (inverter) Fig. 12: Overvoltage protection range and de-excitation via inverter operation In inverter mode, the three-phase incoming circuit breaker / field circuit breaker is closed to enable the energy stored in the rotor to flow back into the power system via the thyristor bridge, which is operating in inverter mode. After the field current has been reduced to almost 0 A, the command stage of the digital trigger set automatically blocks the firing pulses and the three-phase incoming circuit breaker / field circuit breaker is opened in an almost de-energized condition after deexcitation. For protective de-excitation, this method of inverter de-excitation is not possible. The de-excitation is then performed via the SICROWBAR and field discharge resistor, as described above. 10 Unrestricted Siemens AG All rights reserved

11 Supplying power to the excitation system and field-flashing circuit The standard application includes power supply to the THYRIPOL excitation equipment from the generator terminals. Powering the excitation system from the medium-voltage network of the power plant auxiliary power supply is also possible as an option. However, when the excitation system is powered from the generator terminals, field flashing either from the low-voltage system of the power plant auxiliary power supply or from the battery is required. In the first case, the field-flashing circuit comprises a small matching transformer and an uncontrolled rectifier, which can be routed via a switching device parallel to the converter to the field winding of the generator, or in the second case, a connection to the power plant battery via a contactor, blocking diode, and current limitation resistor. All devices belonging to the function components "overvoltage protection," "de-excitation device," and "field flashing" are grouped together into one unit in common cubicles. 1 Converter transformer (1 three-phase transformer or 3 single-phase transformers) 2 Converter 3 Surge suppressor and de-excitation system 4 Field-flashing circuit for excitation build-up 5 Auxiliary voltage (connection to power plant battery or auxiliary power supply Fig. 13: Basic circuit diagram of the SES excitation system Local operator control and monitoring unit For local operation and monitoring of operating states and measured values from the excitation system, and for signaling faults and alarms, a SIMATIC HMI IPC477 operator control and monitoring device is installed in the cubicle door of the open-loop and closed-loop control cubicle. Main functions and features of the visualization unit: Display of operational and display values of both channels Display of analog values Password protection Local operation of the excitation system Display of fault messages and help with elimination of faults Fig. 14: Local operator unit. Example with IPC Unrestricted Siemens AG All rights reserved

12 Data exchange with the peripherals As standard, data is exchanged from/to the excitation system via a PROFIBUS-DP interface with a baud rate of 12Mbit/s. With redundant excitation systems, the PROFIBUS DP interface can also have a redundant design. The essential control commands and checkback signals for operation and monitoring of the excitation system and fault messages and measured values of the generator and field variables are transmitted. Optionally, the signal interface can also be implemented with conventional wiring (hard wired) with coupling relays and optocouplers. SINAMICS DCM (incl. thyristor bridge) Channel 1 SINAMICS DCM (incl. thyristor bridge) Channel 2 Profinet Profinet NTG-3000 Channel 1 SIMOTION D435-2 Channel 1 Optional expansion modules (e.g. TM31) Channel 1 Optional expansion modules (e.g. TM31) Channel 2 SIMOTION D435-2 Channel 2 NTG-3000 Channel 2 Profibus DP (option) Profibus DP (option) Fig. 15: Schematic view of a fully redundant 2-channel voltage regulator The internal communication between the components is shown in Fig. 15. The open-loop and closed-loop control of the excitation system can be implemented either non-redundantly in 1 channel (1 automatic channel voltage regulator and 1 manual channel field-circuit rectifier) or fully redundantly in 2 channels (2 automatic channel voltage regulator and 2 manual channel field-circuit rectifier), also with redundant actual-value sensing. The power supply units for open-loop and closed-loop control are also implemented redundantly, both as 1 and 2-channel variants. 12 Unrestricted Siemens AG All rights reserved

13 5. Method of operation 5.1 Automatic voltage regulator The voltage at the generator terminals is the main controlled variable. Its setpoint can be varied during operation with the setpoint adjuster by ±10% (depending on the generator). Moreover, the voltage can be controlled as a function of the reactive current to stabilize the reactive power distribution over several generators that are run in parallel. This is done with an adjustable quadraturedroop circuit, which can also be used to compensate for the voltage drop across the unit transformer. The voltage regulator controls the setpoint formed in this way with an accuracy of < ±0.5% over the entire defined load range of the synchronous machine. Above this load range, the synchronous machine can only be operated for a short time. After a settable time, the excitation limiter intervenes to bring the field current back to the permissible value in such a case. Further equipment features of the voltage regulator Soft start function (permits controlled excitation build-up of the generator) Tracking function between two regulator channels (with redundant, 2-channel systems) Tracking function between manual (field current regulator) and automatic channel (automatic generator voltage regulator) Black start of a de-energized power system Electrical braking Reactive power / power factor controller Digital recording and monitoring function (TRACE function) for recording binary and analog signals in the excitation system (option) Automatic Voltage Regulator complies with IEEE type ST6B model. 5.2 Field current regulator The field current regulator is an additional control mode for the automatic voltage regulator. The field current of the synchronous machine is adjusted to the field current setpoint adjuster. A field current regulator ensures that the set value is maintained. The field current is measured internally in the SINAMICS DCM on the input side. In excitation devices in SINAMICS DCM design, the field current is calculated from the three-phase input current of the converter. To be able to switch bumpless from one mode (manual mode) to the other (automatic mode), the output signals of both regulators are compared and track each other. With the load-dependent THYRIPOL -L excitation system, the field voltage is regulated instead of the field current. 5.3 Other modes Power factor (cos j) or reactive power control at the generator terminal (automatic closed-loop control system) In the cos j controller, the actual value is compared with a settable cos j setpoint. If a deviation is found, the setpoint of the voltage regulator is varied until the cos j control deviation has been eliminated. In island operation or at no load of the machine, switchover from cos j control to the automatic voltage regulator is automatic. The reactive power controller is also in operation. 5.4 Tracking control During operation, the setpoints of all active modes are continuously tracked to enable fast and almost bumpless switchover. Automatic switchover to the field current regulator is performed only in the event of a fault, including when internal monitoring functions of the field current respond or on fault messages in the generator voltage actual-value sensing. Tracking of the signals between the two channels is performed via Profinet (see Fig. 15). 13 Unrestricted Siemens AG All rights reserved

14 5.5 Excitation limiter Under-excitation limitation By varying the setting of the voltage setpoint, this limitation prevents individual generators from moving too far into the underexcited range during low-load periods. The excitation is increased without regard for the terminal voltage as soon as the settable limit characteristic is reached. The limit characteristic, which is coordinated with the machine protection, is formed by comparing the generator terminal voltage and a variable that depends on the stator current and the electrical angle between the voltage and the current. This enables good adaptation to the stability limit when operating in parallel with the grid. Over-excitation limitation The excitation limiter intervenes with a time delay in such a way as to temporarily enable enhanced grid support followed by a voltage reduction. The excitation limiter permits a maximum ceiling current for a time of < 10s. If the voltage in the power system is to remain below the setpoint or the setpoint is to be adjusted to higher voltage values and the power limits of the generator are preventing the generator from taking the actual value to this setpoint, the excitation limiter will intervene. Stator current limitation In the range of high active power or low voltage, the generator stator current can exceed its rated value despite field current limitation. To avoid such operating conditions, the stator current limiter, which acts via excitation of the generator, is provided. V/Hz limitation Generators are usually insensitive to high induction of short duration. The load caused by a frequency reduction for large transformers is more critical because, in this case, localized eddy currents occur during excessive induction, which can result in thermal overload. To avoid a power system collapse in such a case, it is better to reduce the voltage with the frequency, i.e. to use a V/Hz limitation. 5.6 Power system stabilizer (PSS) The PSS complies with IEEE type 2B model (Dual Input PSS) or optionally PSS3B (Dual Input PSS). The active power and the compensated frequency are used as the input variables. Both input variables are calculated from the 3-phase stator variables (currents and voltage) of the generator by means of a calculation algorithm. In the natural frequency range of the machine and power system, it exerts a damping influence via the voltage regulator and generator excitation. A PSS is recommended for power systems with long transmission lines, whose static stability is at risk and in which the natural damping characteristic of the generator is insufficient. 5.7 Control Each operating condition of the excitation system is monitored and displayed. The internal monitoring sequence provides the following messages at the cubicle terminal in addition to the internal display: Fault with protection off command Fault in the automatic closed-loop control system and switchover to the manual closed-loop control system Group message of various internal fault signals Operational messages are also provided for external display: Excitation is on Excitation is off Automatic closed-loop control system is on Manual closed-loop control system is on cos j control/reactive power control is on Limitations active For customer-specific design in modernization projects, further detailed messages are optionally possible. 14 Unrestricted Siemens AG All rights reserved

15 6. Software Operator-friendly software tools (Web server) ensure convenient commissioning and maintenance of the excitation system. The regulator can be parameterized completely with the Web server. For this purpose, the voltage regulator is connected to a PC via an Ethernet interface and configured via this. The current parameter values can be displayed directly in the parameter list. After selection of a certain parameter, it can be modified by entering a new value. Several predefined parameter lists for certain applications (e.g. inputs/outputs) and a complete parameter list are available. A separate parameter list can also be compiled by entering the parameter numbers. It is also possible to store the current parameterization on data media. This provides a way of documenting the actual condition of the voltage regulator. THYRIPOL -S has a TRACE memory. This is an important tool not only for commissioning, but also for diagnostics and troubleshooting. With the TRACE function, up to 128 analog values of any type (measurement channels) can be recorded in a similar way to a storage oscilloscope, and up to 8 of these can be displayed simultaneously. Each measuring channel can alternatively be used for recording 16 binary values. A convenient trigger can be used to start recording. When the pretrigger is set, the pre-event and post-event history around the instant of the trigger event are recorded. The depth of recording can be configured. The sampling interval between two measuring points is 1.25 ms. Fig. 16: View of measured variables from the TRACE memory THYRIPOL -S 15 Unrestricted Siemens AG All rights reserved

16 7. Application Static excitation systems SES Generator power [MVA] Fig. 17: Applications of the SPPA-E3000 SES excitation systems In the upper power range, the converters of the SES excitation systems are implemented as thyristor stacks. In the lower power range, on the other hand, SIMOREG DC-MASTER compact units are mainly used. Example of a design in the lower power range 1. Two-channel open-loop and closed-loop control with a IPC477 local operator unit 2. SINAMCS DC Master compact unit with a thyristor converter, AC power supply 3. AC incoming circuit breaker, excitation build-up circuit, and de-excitation Fig. 18: Excitation system with 2 x 100% converter compact units and integrated redundant regulator 16 Unrestricted Siemens AG All rights reserved

17 8. Technical specifications The excitation system is designed in compliance with the valid IEC, VDE, DIN, and IEEE standards. Requirements from customer specifications can also be considered. The design is based on the following definitions of the VDI/ VDE guidelines 3680, sheet 2: Rated field voltage U fn The voltage that must be applied to the field winding at the nominal power, nominal power factor, and rated speed of the synchronous machine at the operating temperature to generate the rated field current I fn. Rated current of the excitation system I EN The current that the synchronous machine requires as the field current at maximum continuous operating values is decisive for rating the excitation system components and is therefore defined as the rated current of the excitation system. It should be at least I EN > 1.05 I fn Excitation system ceiling current I p The maximum excitation system output current is called the ceiling current of the excitation system I p. It should be at least 1.4 times the rated field current I fn for a period of at least 10 s. Excitation system ceiling voltage U p The ceiling current is defined as the maximum voltage that the excitation system can output at full deflection of the final control element toward positive voltage values. Depending on the connection circuit, it depends on the operating state of the synchronous machine, the field current source, and the change over time of this operating state. Depending on the excitation system, the following factors are considered by default: THYRIPOL 1.6 U fn THYRIPOL -L 1.4 U fn For the voltage rating of the excitation system, the nominal ceiling voltage is decisive. The nominal value of the power source is based on it as the supply voltage of the excitation system. For the THYRIPOL excitation system, that means, on connection to the generator terminals, the rated voltage is assumed there and the excitation system is loaded with the rated field current I fn of the generator. In the case of the load-current dependent THYRIPOL -L excitation system, the rated current I GN flows in the stator of the synchronous machine. This assumes the generator is at normal operating temperature. Accuracy of the closed-loop control: 0.5% over the entire defined load range of the synchronous machine 17 Unrestricted Siemens AG All rights reserved

18 9. Abbreviations a Control angle of the converter - expressed in el AVR Automatic voltage regulator B6C/ B6 6-pulse thyristor bridge circuit - controlled/ uncontrolled BOD Break-over diode for protection against surges GEAFOL Cast-resin transformer I EN I f I fn I p PSS PROFIBUS DP SG SICROWBAR SIMATIC S7-300 SINAMICS DCM SINAMICS CM Rated current of the excitation system Field current of the generator Rated value of the field current Excitation system ceiling current Power system stabilizer Process Field Bus distributed I/Os Synchronous Generator Surge suppressor module Controller with CPU, digital inputs and outputs, and communication module Compact converter of SINAMICS DCM of type 6RA80 Converter Control Module SPPA Siemens Power Plant Automation SPPA-E3000 Electrical engineering solutions of the Siemens Power Plant Automation THYRIPOL -L Load-dependent THYRIPOL excitation system U f U fn U fu U p U pl SES CES BES U p0 Voltage applied to the terminals of the field winding Rated value of the field voltage Negative field voltage Excitation system ceiling voltage Load ceiling voltage of the excitation system Static Excitation Systems Compound Excitation System Brushless (rotating) Excitation Systems No-load ceiling voltage of the excitation system 18 Unrestricted Siemens AG All rights reserved

19 Published by and copyright 2016 Siemens AG Power and Gas Freyeslebenstrasse Erlangen, Germany If you would like more information, please contact: Siemens AG Fossil Power Generation Division Siemensallee Karlsruhe, Germany sppa-e3000.energy@siemens.com e3071_dt21_ses_thyripol_s_technbeschreib_e_v1-0-0_arbex-01.docx AL: N ECCN: N Unrestricted All rights reserved. Trademarks mentioned in this document are the property of Siemens AG, its affiliates, or their respective owners. Printed on elementary chlorine-free bleached paper. Subject to change without prior notice. The information in this document contains general descriptions of the technical options available, which may not apply in all cases. The required technical options should therefore be specified in the contract. 19 Unrestricted Siemens AG All rights reserved