Catalogo Thyripol Ingles_excitacao

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Thyripol D™ Digital excitation and voltage regulation system for synchronous machines Introduction

he THYRIPOL D™ excitation system is used for the excitation and voltage

regulation of synchronous machines fitted with slip rings. In such cases the rotor winding is supplied directly by the Thyripol D by means of static thyristor rectifiers in B6C configuration. Instead of the terminal voltage the system can also perform the reactive power or the power factor regulation.

Due to its outstanding features the dry type GEAFOL™ transformers of Siemens are the best choice as excitation transformers.

The system takes from the machine terminals the necessary energy for supplying the field winding through a three-phase medium voltage

excitation transformer, which can be a dry type or an oil-immersed one. This transformer is especially designed for supplying fully controlled thyristor rectifier bridges. The protection of the excitation transformer is performed by a fully digital overcurrent relay of the SIPROTEC™ series of Siemens. The generated voltage is controlled by varying the moments at which the thyristors are fired, that is, become conductive. This way a controlled direct current is supplied to the field winding. The automatic voltage regulator is responsible for automatically matching the excitation current to the actual load condition of the synchronous generator. For the excitation build up (field flashing) auxiliary energy must be taken from the power plant auxiliaries (AC or DC). The energy drain from the auxiliary source is automatically switched off as soon as the main rectifier (thyristor bridge) takes over the field supply, what occurs as the terminal voltage reaches about 15% of its rated value. Anyway the field flashing device is switched off if the generator voltage has not built up during the adjusted time interval.

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The measuring of the analogical values, the voltage and reactive power regulation, the control of the start up and shut down processes, the setpoint generation for the regulators and the whole system monitoring as well as the alarm generation are carried out by the processor modules in a completely digital way. The CPU modules possess floating point RISC technology microprocessor. No transducers are used for voltage and current measuring. The powerful operating system of the voltage regulator allows defining the several sampling times to be used by the processor. The shortest sampling time of 0.1 ms is associated with the fastest task. Power stage

he current is rectified by a fully controlled three-phase rectifier bridge of the

Simoreg™ 6RA70 series. The rectifier is air forced cooled. The thyristors are individually protected by ultra fast supervised fuses. The rectifier bridge is designed for the most severe overload conditions of the generator. The Simoreg converter possesses a complete protection and monitoring system of all thyristors, what also includes junction temperature calculation and indication.

Outward appearance of a 2,000 A rectifier bridge. The compact construction of the unit and the parameterization device on the converter door are noticeable.

On request the Thyripol excitation system can be designed with N+1 redundancy, that is, an identical Simoreg unit is additionally supplied in order to increase the system availability. In this configuration, only one Simoreg converter (namely the “master channel”) is working at a time: the other one (defined as “slave channel”) stands by and follows up continuously the master unit. If faults involving the master channel occur, the slave channel takes over the excitation field supply immediately, without any oscillations on the generator voltage, so that the generator remains in safe operation.

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Automatic voltage regulator (AVR)

he regulation, monitoring and control tasks of the excitation system are carried out by

powerful RISC technology processor modules with floating point arithmetic. This feature allows the processors to work directly with real numbers, what means that there is neither a scale limitation nor the need of scale adjustments. Furthermore, the operational system is multitasking based on priorities: the processor carries out at first the task associated with the shortest sampling time, that is, the task with the highest priority. Immediately afterwards the processor carries out the task associated with the second shortest sampling time and so on. This way the accomplishment of a certain task can be interrupted several times, during its processing, by tasks with shorter sampling times. This way of processing guarantees that the digital regulator performance can be compared to the one of an analogical regulator. The CFC programming language is very friendly and possesses numerous possibilities for on line editing and testing. Furthermore it enjoys the use of all the facilities of the Windows™ operating system.

There are two independent regulating channels: AUTOMATIC (automatic voltage regulator or AVR) and HAND (field current regulation).

The regulation and control software is fully graphic and friendly, what makes the programming and understanding easier.

Both regulating channels (AUTOMATIC and HAND) act on the same rectifier bridge. A bumpless channel changeover from automatic to hand and vice-versa is ensured by a follow up routine. If specified by the client the regulation is configured as double automatic voltage regulators. In such cases two identical and completely independent automatic channels are designed, each one possessing its own hand channel. The power supply for the electronics is always taken in a redundant way, namely from the excitation transformer and from the station battery. Automatic channel

he automatic channel corresponds to the automatic voltage regulator (AVR), which

compares the generator voltage actual value with the reference value (voltage setpoint) adjusted by the power plant operator.

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For the measuring of the actual generator voltage the three phases are used. This way any unbalance among the phases is taken into account, leading to a very precise measuring. The generator voltage and current actual value detection is fully digital and does not employ any kind of transducers. The generator voltage setpoint is digitally generated and can be adjusted in the range 90% to 110% of the rated generator voltage. During the operation of the synchronous generator attention must be paid to its capability diagram. For this reason the following limiters act on the AVR:

• Quick acting excitation current limiter (field forcing limiter)

• Overexcitation limiter • Underexcitation limiter • Volt/Hertz limiter • Stator current limiter

The automatic voltage regulator includes also the power system stabilizer (PSS), which stabilizing output signal is derived from the power and frequency oscillations (accelerating power). Additionally the THYRIPOL D excitation system includes also a reactive power (or power factor) regulator for controlling the reactive

power (or power factor) of the generator itself or of any point of the plant.

During the automatic voltage regulation it must be ensured that the generator always works inside its capability diagram. This function is carried out by the limiters.

Hand channel

his control channel corresponds to the excitation current regulator. It is

extremely useful when performing tests on the generator. In addition the hand channel works as a stand-by regulator allowing continuing of the operation even at failures in the AVR. The setpoint of the excitation current ranges from about 10% up to 110% of the rated excitation current of the generator. By taking an independent power supply for the excitation system (e.g. during tests) the setpoint range stretches from zero to 110%.

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REACTIVE POWER (MVAr)

ACTIVE POWER(MW)

OVEREXCITATIONUNDER-EXCITATION

STATORTHERMAL

LIMIT

STABILITYLIMIT

STATORTHERMAL

LIMIT

ROTORTHERMAL

LIMIT

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Channel changeover and follow-up

bumpless channel change-over from AVR to excitation current regulator and vice-

versa can occur at any time. This is possible thanks to the follow-up routine, which ensures that the selected control channel follows up the settings of the other channel. This way the outputs of both channels have always the same firing angle for the thyristors, what guarantees a bumpless channel changeover at any time. Certain failures involving the AVR cause an automatic changeover to the hand channel. A trip signal is released if failures occur in the hand channel being selected the hand channel. In the double channel configuration (two independent automatic voltage regulators) an automatic changeover to the standby AVR takes place at the occurrence of failures in the operating AVR. In such cases a channel changeover to the hand channel takes place automatically only if both AVRs are simultaneously faulty. Mode of control

he system is prepared not only for local operation (by means of a man-machine interface)

but also for remote operation (through the power plant superordinated control system). The color touch screen man-machine interface (MMI) is installed on the regulator cubicle door. This device is also fitted with a keyboard that can be used additionally to the touch screen functionality.

The local control of the excitation system is performed through the integrated touch screen man machine interface.

Through this device commands (Excitation ON /OFF, Channel selection, etc.) can be entered and actual system parameters (excitation current and voltage, generator active and reactive power, generator voltage, setpoints etc) can be read out. Furthermore alarm messages in plain text with time stamp are displayed on the screen for making trouble shooting procedures even easier.

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The Thyripol D excitation system can be connected to the superordinated control system of the power plant by means of normal cabling because all of the input and output signals are available on terminal strips as potential-free contacts. Furthermore the system is also ready to be connected to a communication network using the PROFIBUS DP protocol. This communication link can be optionally built using optical fiber. Other communication protocols are optionally available (ETHERNET, MODBUS etc). De-excitation and overvoltage protection

t normal conditions de-excitation is carried out by forcing the thyristor bridge to

operate as inverter. The field polarity inversion causes thus a very quick reduction of the excitation current towards zero. About 5 s after introducing inverter operation the controller opens the field circuit breaker (FCB) at the AC side of the rectifier bridge. Since the excitation current at this time will have already reached zero, the main contacts of the FCB open at no load condition, what increases the lifetime of the device. For safety reasons the FCB is always fitted with 2 independent trip coils.

The use of a field circuit breaker at the AC side of the rectifier bridges has several advantages over a conventional field circuit breaker at the DC side. The main advantage is that the whole excitation power supply, i.e. the excitation transformer, is completely separated from the rectifier in the event of a short circuit on the generator terminals.

Additionally the Thyripol D excitation system possesses also a linear field discharge resistor. It is used to dissipate the stored energy of the exciter field winding in emergency situations, where inverter operation cannot be ensured any more. The discharge resistor is inserted in the field circuit whenever the FCB opens. The overvoltage protection is carried out by the Sicrowbar™ unit, a static switch developed and manufactured by Siemens. This device is composed by two anti-parallel thyristors, which are fired separately according to the polarity of the induced overvoltage, which is detected by a sensor that requires no auxiliary energy to operate.

When a thyristor of the Sicrowbar™ device is fired the discharge resistor is immediately inserted in the circuit so that the overvoltage is safely

suppressed.

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Mechanical features

ll low voltage devices of the excitation system are housed in metallic cubicles fitted with

front and rear doors. A typical construction with N+1 redundancy comprises 4 cubicles with total dimensions 2400 x 1000 x 2500 mm (WxDxH). The openings on the doors for cooling are provided with filter. The cubicles are constructed with 1.9 mm dick steel sheets. The supporting frames are made of 2.5 mm dick steel sheets. The cubicle wiring uses self extinguishing copper conductors insulated for 750 V.

All conductors have identification rings at both ends. Each one of the devices has identification tags with the device symbol according to the electrical diagrams and have easy access. The standard protection degree is

IP41. The standard finish color is light grey Munsel N6,5. However any other finish color is possible according to the client’s specifications. Thyripol with double automatic channel and redundant rectifiers (1+1), designed for 140 MVA hydrogenerators.

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Troubleshooting

he access to the parameters of the voltage regulator for viewing and changing is easily

done by means of the Drive Monitor software tool provided with the

excitation system. This powerful tool is used for commissioning and troubleshooting of the excitation system. This tool gives on line values of all regulator and generator signals.

The main features of the Drive Monitor software tool are described below:

Menu-assisted access to all parameters.

On line help for each parameter to be viewed and/or modified.

On line read out, writing and comparison of parameters.

Output of parameter sets to a printer.

Copying of existing parameter sets to other identical excitation systems.

Fault memory for the last 64 fault occurrences in the regulator.

Integrated oscilloscope function for graphical presentation of the trace buffer contents (Trace Function).

The trace function can be selected to store up to 8 measured quantities with 128 measuring points each. A measured quantity or the activation of a fault message can be parameterized as a trigger condition. It is possible to record the pre-event and post-event history by programming a trigger delay. The sampling time for the measured value memory can be parameterized to between 3 and 300 ms. A data base is automatically generated for future use. This data base is compatible with MS-Excel®.

A useful functionality of the Drive Monitor software tool is the trace function (integrated oscilloscope) for recording analogical and digital signals.

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A typical Thyripol excitation system

n the example below it is shown a Thyripol excitation system designed for a maximum

continuous field current of 1240 A. This system possesses 2 identical automatic voltage regulators (double AVR). Furthermore, the rectifier set was designed with 1+1 redundancy, i.e., it is composed by 2 parallel connected thyristor bridges, each one capable of supplying 100% of the maximum excitation current of the synchronous machine. At a time only one bridge is producing the necessary field current. At the occurrence of failures in this rectifier bridge, the stand by bridge takes over the current immediately without any voltage oscillation on the generator terminals.

This operation philosophy is essentially better than the conventional one, where all the bridges work simultaneously, then:

• There is no need of circuits for equalizing the current sharing between parallel thyristors;

• Guaranteed 100% redundancy; • Each rectifier bridge is

controlled by its own AVR; • One regulator can be serviced

whereas the other is operating; • Heavy-duty fan units

integrated to each rectifier bridge;

• The readiness of the stand by rectifier is continually monitored.

The above described project is only a sample showing a typical solution, which reflects the current philosophy and technology. The Siemens’ Engineering Team is indeed able to fulfill any specification of excitation systems, with features that can be quite different from the above related ones.

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Field circuit breaker at the AC side of the rectifier: safe de-

excitation process and longer service life of the

breaker.

Two fully controlled rectifier bridges (1 + 1 redundancy).

Each rectifier bridge is designed for 100% of the rated

current of the excitation system.

De-excitation resistor with linear

characteristic: endless service life.

Field flashing taken from the power plant

auxiliaries (AC and/or DC).

Insulated copper busbars and

protection barrier against unexpected touch: higher safety

during maintenance.

Overvoltage protection by static switch (Sicrowbar™

device).

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Benefits for the customer

he THYRIPOL excitation system results from the huge Siemens’ experience in development,

design and manufacture of control, regulation and rectifier systems.

Having Siemens as a partner for voltage regulation assures the customer the certainty of being assisted by the world’s biggest manufacturer of equipments for power generation and transmission.

HIGHLIGHT BENEFITS

Huge experience in this area proved by the more than 2000

excitation systems that have been delivered since 1966.

Proved solutions with high reliability and availability.

Manufacture of excitation systems in Brazil since 1985.

Understanding of the needs of the local customers.

The main components of the excitation system, like e.g.

voltage regulator, power rectifiers and field circuit

breaker, are standard devices manufactured by Siemens itself.

Certainty of quality, full compatibility of components and guarantee of spare parts.

Training at the site or at Siemens’ training center, given by our

engineers.

Without any difficulty for learning how to operate and service the equipments.

Engineering, manufacturing and tests in Brazil.

Direct contact to the people that design and manufacture.

The customer himself has access to system software for diagnosis.

The system software is open and friendly. Quick troubleshooting.

Siemens offers customized trainings, where the contents are defined together with the customer, so to fulfill the customer’s necessities concerning operation and maintenance of the excitation systems.

Please visit our site in Internet for more information regarding the Siemens’ solutions for voltage regulation and excitation systems: www.siemens.com.br/excitacao.

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Standard features of the THYRIPOL D digital excitation system

Standards and regulations Regulations of the Submódulo 3.6 of the ONS (Brazilian corporation for regulating and operating the national power generation and transmission).

IEEE Std421 regulations and recommendations.

Applicable standards of IEC, VDE, DIN and Brazilian ABNT.

Generator rated excitation current Up to 3000 A DC (Please see note #1)

Maximum ceiling voltage Up to 1200 V DC (Please see note #1)

Control voltage 110, 125 or 220 V DC

Auxiliary power source for field flashing

From the power plant auxiliary power supply (AC or DC).

Normally it is necessary to supply to the field approx. 15% of the no load excitation current during about 10 s.

Connection to potential transformers

3 x PT’s on phases L1, L2 and L3 (“V connection” is also allowed).

Secondary voltage: 110, 115 or 120 V; power consumption: 10 VA per phase.

Connection to current transformers

2 x CT’s on phases L1 and L3.

Secondary current: 1 or 5 A; power consumption: 10 VA per phase.

Regulator Fully digital; double channel configuration: Auto Channel (AVR) and Hand Channel (excitation current regulator).

On request: double automatic channel, each with its own hand channel.

Limiters • Quick acting excitation current limiter (field forcing limiter)

• Overexcitation limiter (inverse time characteristic)

• Underexcitation limiter

• Stator current limiter (inverse time characteristic)

• V/Hz limiter

Power supply for the regulator electronics

Redundant configuration: from the excitation transformer and from the station battery.

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Setpoint range (typical) • Generator voltage: 90% ... 110%

• Excitation current: 10% ... 110% By taking an independent power supply for the excitation system (e.g. during tests) the field current setpoint range changes to 0% ... 110%.

Rectifier Three-phase fully controlled thyristor bridge (B6C) with six thyristors and forced air cooling by heavy duty fan units.

Redundant configuration (1+1) is provided on request.

Power requirements from the station battery

Interfacing and control circuits: 500 W (continuously) / 1500 W (Short time - 5 s)

Typical total dimensions of the cubicle assembly at redundant configuration of the rectifier

2400 x 1000 x 2300 mm (W x D x H)

Approximate weight for the above mentioned assembly

1500 kg

Standard protection degree of the cubicle

IP 41 or according to customer’s specifications

Finish color Grey Munsel N6,5 or according to customer’s specifications.

Some optional features normally requested

• Redundant rectifiers (1+1)

• Communication through optical fiber

• Other communication protocols (different from the standard PROFIBUS DP), e.g. TCP/IP, Modbus, etc.

Standard interfaces to other equipments

• Potential free contacts (conventional wiring)

• Serial through PROFIBUS DP protocol (RS485 or optical fiber)

Standard analogical outputs for remote indication

(4...20 mA)

(Please see note #2)

• Excitation current

• Voltage setpoint

• Current setpoint

• Generator voltage

Some standard features • PSS based on accelerating power, according to IEEE Std421.5.

• Field overvoltage protection by Sicrowbar™ (the trigger voltage is defined during the project detailing and depends on generator and system data).

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• Reactive power or power factor regulator.

• Easy copying of parameter sets to other identical excitation systems (e.g. from the same power plant).

• Access to all system parameters for viewing and/or changing directly through the integrated parameterizing unit. No PC needed for such tasks.

• Drive Monitor software tool for commissioning, tests and diagnosis supplied together with the equipment. Oscilloscope function included.

• Color touch screen man machine interface integrated on cubicle door. Another one, with the same features, can be optionally supplied for the control room.

Note #1: For excitation currents higher than 3000 A or in the cases where the ceiling voltage lays over 1200 VDC, the THYRIPOL D excitation system is constructed with SITOR™ rectifier components. Note #2: As standard feature the THYRIPOL excitation system possesses 4 analogical outputs for remote indication of the mentioned values. Instead of such values the customer can specify any others. According to specifications the quantity and/or type of analogical outputs can also be modified. Modifications in the mentioned features can be made due to technological improvements at any time without prior notice.

For more information please contact us: Siemens Ltda. Av. Mutinga, 3800 05110-901 São Paulo, SP Tel.: (11) 3908-1888 / 3908-1876 FAX: (11) 3908-1811 Internet: www.siemens.com.br/excitacao

Edition: November 2009