Chapter 3 Rev 1-1

3

DESCRIPTION OF ELECTRICAL COMPONENTS AND SYSTEMS

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3 3.1 3.1.1

DESCRIPTION OF ELECTRICAL COMPONENTS AND SYSTEMS

1

Electrical Components

4

3.1.1.1 3.1.1.2 3.1.1.3 3.1.1.4 3.1.1.5 3.1.1.6 3.1.1.7 3.1.1.8 3.1.1.9

The Control Panel Industrial PC Failsafe PLC Gas Leakage Monitoring Generator protection Synchronization Measuring Transducer View of the control panel Side view of the Control Panel View of the control panel swing frame

4 4 6 7 8 9 10 11 12 13

3.1.2.1 3.1.2.2 3.1.2.3 3.1.2.4

Supply panel Roof module AC Supply System DC Supply system View of the supply panel

14 14 15 16 18

3.1.3.1 3.1.3.2

Liquid fuel pumps control panel Static frequency converter (SFC) EMC Filter

20 20 20

3.1.4.1 3.1.4.2 3.1.4.3 3.1.4.4 3.1.4.5 3.1.4.6

Field Bus Modules Client Module Baseframe Module Lube Oil Module Turbine Module Gas Module Liquid Fuel Module

22 23 24 25 26 27 28

Electrical Systems

29

3.2.1.1 3.2.1.2 3.2.1.3

Control System System Architecture System Architecture Diagram Field Bus Structure Diagram

29 29 30 31

3.2.2.1 3.2.2.2 3.2.2.3 3.2.2.4 3.2.2.5 3.2.2.6 3.2.2.7 3.2.2.8

Back-up Safety System Failsafe PLC Back-up System shut down Criteria Safe State of the Machine Flame Monitoring (flame out) Turbine ignition supervision Turbine start-up supervision (acceleration time) Boiler Protection Data Exchange with Control System

32 32 32 34 34 34 35 35 36

3.2.3

Emergency Lube Oil Pump

37

3.3

Fire detection and extinguishing system

38

3.1.2

3.1.3

3.1.4

3.2 3.2.1

3.2.2

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3.3.1 3.3.2 3.3.2.1 3.3.2.2

3.4 3.4.1 3.4.1.1

Fire system’s equipment

38

Fire system operation Operational logic of the automatic detection Fire monitoring alarms

39 40 41

Gas monitor system

42

Description of the gas monitor system Gas monitor alarms

42 42

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3.1

Electrical Components

3.1.1

The Control Panel The control panel contains all the electrical control and regulation equipment, safety equipment and displays that are required for the operation of the gas turbine plant. Control and regulation is executed by means of an industrial PC system, which controls and regulates the field components via the field-bus. A failsafe PLC is used for safety back-up monitoring. The control panel also contains: Generator voltage regulator • Generator protections • Protection screen (if required) • Synchronization equipment • Transducers • Internal auxiliary power unit 400/230VAC In mechanical terms, the control panel is based essentially on a control panel rack without side or cover sections. A self-supporting wiring frame composed of prefabricated parts is built into the rack, and the electrical apparatus are mounted on this frame. •

All the wiring is installed in the rear level of the panel and can be accessed from the side at any time. The control panel is supplied with 24 V DC and 230 V AC voltages by the supply panel.

3.1.1.1

Industrial PC The TURBOMACH control system is based on two industrial PC designed for industrial applications. Each PC possesses its own processor, operating system, hard disk, floppy disk and other modules required for operation. The two industrial PC are divided in control and service sections. The two sections are linked to each other via Ethernet link. The electronic components of the control panel require a 24 VDC supply, which is provided by the supply panel.

3.1.1.1.1.

The “Control section” (Real time PC) This section contains the process software responsible for the open and closed loop controls which regulates the gas-turbine and its fuel supply for the various operating conditions. The main regulation functions implemented in this section include: • • • • •

Fuel regulation. Turbine speed and temperature control Active power control Load sharing control for multiple machines application Exhaust emission control of SoLoNOx turbines

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• • •

Lube oil pressure control Compressor inlet guide vanes control (IGV) Bleed valve control

This section consists of the following elements: Celeron single-board PC • MS-DOS 6.xx with real time multitasking operating system • Ethernet card • Profibus master card • Floppy disk. • USB connection • IDE Flash Disk The Profibus master card is the interface to the field level and controls via the field-bus all electronic input and output modules of the turbine plant. •

3.1.1.1.2.

The “Client service section” (HMI PC) This section contains the process software responsible for the turbo-generator functional sequences, data collection and interface to the remote workstation. All functions related to the human-machine interface (HMI) or machine-machine interface are handled here. The main functions implemented in this section include: • • • • •

Functional sequences for the turbine and its ancillary equipment. Command for the main installation inputs/outputs. Data storage. Data display (HMI interface and touch-screen) Interface for the remote workstation.

Interface with OPC protocol is available as standard. This section consists of the following elements: • • • • • • • • • •

ADM single-board PC Windows operating system Ethernet card (3, 1 of which is made from glass fibre) RS232 (2) connecting plug USB (5) connector Ethernet connection to the control PC Ethernet connection to the remote PC Touch screen 17” TFT color, SVGA Hard disk DVD-ROM/CD-RW

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3.1.1.2

Failsafe PLC A SIEMENS S7-300-315F failsafe programmable logic controller is used to ensure the safety of personnel and machinery. This consists of two sub-units (A and B), which work in parallel with the same software. An opto-electronic link enables data exchange between the two units. The controllers are component-tested and certified as failsafe. In accordance with DIN V 19250 the gas turbine plant complies with Requirement Class 6. This class also covers boiler burners. In accordance with IEC 1508, Requirement Class 6 corresponds to SIL 3 (Safety Integrity Level). In addition to the “failsafe section” this unit also contains a “non-failsafe section”. Basically, the “failsafe section” is used for the safety-relevant criteria of personnel protection. The “non-failsafe section” is used to implement the mechanical protection of the turbine. This mechanical protection ensures, for example, that the turbine is permanently lubricated. The essential tasks of this control are: Emergency shutdown function • Gas valve tightness check • Control of the liquid fuel valves (if available) • Flame monitoring • Ignition time monitoring • Start-up time monitoring • Overspeed control • Gas leak monitoring • Emergency lubrification control All inputs and outputs are transmitted in a safety-related manner. •

The binary input or output, as well as the analogue input, are implemented either: By means of one certified sensor, which because of its “special design” is considered failsafe and thus is looped as a single channel to both sub-units (A and B). • With two redundant non-certified sensors, wired independently to sub-units A and B. This logic applies especially to all external signals from the boiler and from the central fire detection system. •

CAUTION The tasks of the control system are limited to the gas turbine and do not include any safety-related handling of other plant components such as boiler, gas compressor or similar. Excepted are the boiler safety chain and the fire alarm signal.

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3.1.1.3

Gas Leakage Monitoring The gas monitoring system makes it possible to detect escaped gas within the package. This prevents the formation of dangerous gas concentrations, which could lead to explosions. Gas sensors are located in the gas turbine container. The gas sensors are connected directly to the failsafe PLC. (looped via sub-unit A and B). An optical warning indicator is located above the main access door of the enclosure, which is activated in the event of a gas alarm. The signal 4-20 mA corresponds to 0 - 100% of the Lower Explosion Limit (LEL). LEL corresponds to a concentration of 5% methane gas (CH4) in the air. The evaluation is carried out directly in the failsafe PLC by the STEP-5 software program. The analog input is failure controlled and a malfunction message is issued (SD). If it reaches 20% of the lower explosion limit, a warning is issued (WR). The warning is displayed on the turbine control screen. If it reaches 40% of the lower explosion limit, a shutdown is carried out (SD)

Alarm

Action

Threshold

Screen message

System fault

Shutdown (SD)

I 2,5 < > 20.5 mA

SRS-Gas detection input error

Gas warning

Warning (WR)

20%

SRS-Gas detection

Gas alarm

Shutdown (SD)

40%

SRS-Gas detection

In the event of a gas leakage, the failsafe PLC is responsible for: Shut down the gas turbine Interrupts the gas supply (safe condition of the machine) • Disconnects the electrical loads in the enclosure • Activates the optical warning indicator The failsafe PLCs inform the PC system of the gas alarm situation. • •

The PC system controls the container ventilation system, which purges the enclosure from the escaped gas. CAUTION The container ventilation is not directly controlled by the failsafe PLC.

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3.1.1.4

Generator protection Microprocessor-controlled Schlumberg SEB SIGMA-N protection relays are used for the generator protection. These are protection relays in a 19” plug-in module design (4U), in which several protective functions are programmable. The main characteristics of the protection relays are: • • • • • • • •

3.1.1.4.1.

Programmable thresholds and timers Event memory Relay outputs Display of the real time measurements and the setting parameters LEDs for operational and fault indications Keyboard for entering parameters Internal self-diagnosis Remote connection option

Generator Protection The generator protective functions are provided by 4 relays as follows: IDG 8N (turbines without step-up transformer)

87G:

Generator block differential current. IDT 8N (turbines with step-up transformer)

87 T:

Generator block differential current. ING 4N

50:

Over current (time independent) for short circuit protection

51:

Over current (time dependent) for overload protection.

64S:

Earth fault over current (time independent) for stator earth fault (95%) protection, via current transformers (if required) Negative sequence over current for unbalanced load protection.

46:

UAR 4N 27:

3 phase Under-voltage protection

59:

3 phase Over-voltage protection

64S:

Residual voltage (time independent) for stator earth fault (95%) protection, via open delta transformer. PQR 4N

40:

Loss of excitation

32:

Reverse power

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3.1.1.5

Synchronization The synchronizer, model Woodward SPM-A, compares the frequency, voltage and phase angle of the generator voltage with the reference voltage (bus-bar or grid) and generates the regulation signals. The speed is matched by means of an analog system that is sent to the regulation system. The voltage is directly equalized by the generator voltage regulator (AVR). The synchronizer gives the command to close the circuit breaker if the phase angle is within 5° window and the voltage and frequency difference are within the max. thresholds. The synchronizer receives and sends the following signals: • • • •

3.1.1.5.1.

Generator voltage Reference voltage (bus-bar or grid) Output analog signal for speed regulation Output impulse for circuit breaker command

Synchronization Voltage Input Check To verify the correct connection of the external voltage supply for the synchronization equipment, the system is provided with a voltage check relay. In case of voltage failure the synchronization sequence is automatically aborted.

3.1.1.5.2.

Synchronization equipment During the synchronization sequence, the difference between voltage and frequency and the phase displacement are tested with double-voltmeter, double-frequency metre and synchronoscope respectively. The best conditions to close the circuit breaker are when the synchronoscope needle indicates 12 o’clock and the difference in tension is lower then 10%.

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3.1.1.6

Measuring Transducer The control panel contains different transducers for the direct data reading.

3.1.1.6.1.

Active Power Transducer The active power transducer provides a signal 4-20mA proportional to the generator output in kW. This signal feeds directly an analogue input of the field-bus system. The active power value is used by the PC system for regulation process.

3.1.1.6.2.

Reactive Power Transducer (optional) The reactive power transducer provides a signal 4-20mA proportional to the generator output in kVar. This signal feeds directly an analogue input of the field-bus system. The reactive power value is used by the PC system for regulation process.

3.1.1.6.3.

Cosphi Power Transducer (optional) The cosphi power transducer provides a signal 4-20mA proportional to the generator output in cosphi. This signal feeds directly an analogue input of the field-bus system. The cosphi power value is used by the PC system for regulation process.

3.1.1.6.4.

Multi-purpose Power Transducer The 3710 ACM multi-purpose transducer is a 16-bit microprocessor-based digital power transducer device for three-phase systems. The transducer measures the generator voltages and currents. The basic parameters of the device can be quickly and easily programmed on the front panel. The basic parameters include volt and ampere scales, type of network or baud rate for data transmission, and are stored in a permanent memory. The following measurements are available: • • • • • • • • • •

Voltages (phase-phase or phase-neutral conductor) Currents (all phases) Active power and Reactive power Apparent power Active energy Reactive energy Apparent energy Power factor Frequency

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3.1.1.7

View of the control panel (Typical layout, not project-specific) For the project specific layout see the electrical drawings.

Industrial PC

Failsafe PLC

DC automatic fuses (MCB) AC automatic fuses (MCB) Transducers

Profibus node (control)Auxiliary relays

Terminal strip

Cable holders

400/230VAC Transformer

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3.1.1.8

Side view of the Control Panel

(Typical layout, not project-specific) For the project specific layout see the electrical drawings.

Synchronization equipment

Transducer

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3.1.1.9

View of the control panel swing frame (Typical layout, not project-specific) For the project specific layout see the electrical diagrams.

•

Synchronization instruments

PC HMI Touch-screen

Multi-purpose power transducer

Floppy disk, emergency stopLube pump switch, IG opening key

Vibrations Unit Control System

Generator protection

Grid Protection (option)

Voltage regulator (AVR)

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3.1.2

Supply panel The supply panel contains the DC power supply and the Ac distribution system. The direct voltage distribution system supplies a stable, linear and constant 24VDC for all control and regulation system. A battery charger keeps the maintenance free batteries at the optimum charge state. The main supply from the client is fed into the distribution system through a manual power switch. The AC distribution system provides the energy for the turbine’s auxiliary equipment. In mechanical terms, the supply panel is based essentially on a control panel rack without side or cover sections. A self-supporting wiring frame composed of prefabricated parts is built into the rack, and the electrical apparatus are mounted on this frame. All the wiring is installed in the rear level of the panel and can be accessed at any time from the side. In the supply panel swing rack are installed the 24VDC battery charger and the fire monitor unit.

3.1.2.1

Roof module The roof module field bus is positioned inside the AC supply panel. It includes all the inlets and outlets devices that are necessary to control all the auxiliary equipments mounted on the upper part of the package, which is called “roof module”. The roof module is a part of the plant and includes all the control and command signals, as far as the tools mounted on the upper part of the package. The supply panel generates the 400VAC voltage supply. The field actuators and the sensors that are controlled by this module are: • • • •

Inlet and outlet air diverters control unit for the package ventilation Oil cooler-fans control unit Oil mist-separator filter insertion control unit Comburent air-filters solenoid valve control unit

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3.1.2.2

AC Supply System The three phase 400 VAC power supply is fed by the customer’s external distribution system. (Protected by means of a fuse or circuit breaker). The feeder is normally composed of a 400 VAC three-wire system and the 230 VAC are produced and distributed internally with an auxiliary voltage transformer. The main power distribution system consists of a bar bus upon which are mounted several magnetotermics that protect the engines. The main components are: • • • • • • • •

Start motor Lube oil heater Package heater Lube oil cooler fans Package fans Electrostatic filter fans Liquid fuel circuit power system (only for liquid fuel versions) Compressor washing water pump

The 230VAC auxiliary distribution supplies the following equipments: • • • • • • •

24 VDC battery charger. Sockets and lighting for control panels and enclosure Electrostatic filter Air conditioner Generator heater Fire detection unit Control panel heater (if installed)

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3.1.2.3

DC Supply system The DC supply system ensures a continuous non-interruptible power supply of 24 VDC for the entire turbine plant. The main components of the DC supply system are the battery charger, the batteries and the distribution system.

3.1.2.3.1.

Battery Charger The rectifier unit, the battery and the loads are connected in parallel, so that the battery can be charged and the DC loads supplied at the same time. If supply voltage is present the rectifier unit provides the current and keeps the battery fully charged. The battery can contribute to the supply of current if the load exceeds the nominal current of the battery charger. In the event of a supply power failure the batteries take over supplying the loads without interruption. The rectifier unit itself is of the primary switched mode type and works according to the principle of pulse width regulation. The regulation is carried out according to the UI characteristic as per DIN 41773, with voltage compensation for the battery temperature.

3.1.2.3.2.

Battery The battery consists of 4 mono-blocks with 6V elements connected in series, providing 24VDC. The batteries are lead-acid maintenance-free (sealed batteries) with a total capacity of 100Ah. The primary task of the batteries is, in the event of a failure of the charger, e.g. as a result of a mains power failure, to guarantee the post-lubrication of the turbine by means of the electrically driven pump.

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3.1.2.3.3.

DC distribution system The 24 VDC distribution system provides the power for the different panels and modules installed in the package. Each output is provided with an automatic fuse (MCB) and auxiliary contact that provides an alarm signal in case of an open fuse. The battery voltage is controlled by the PC system and can be read on the HMI monitor. The current supplied by the battery charger can be read on the charger display.

3.1.2.3.4.

DC supply system for the emergency lube pump System 24VDC battery grants the emergency lube pump supply system. The pump allows the plant post-lubrification in case of an interruption in the AC supply system.

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3.1.2.4

View of the supply panel (Typical layout, not project-specific) For the project specific layout see the electrical drawings.

DC automatic fuses (MBC)

Ac automatic fuses MBC)

Profibus node (Supply + Roof) A

uxiliary relays

AC distribution bus bar

Terminals

AC main distribution

General switch, star / delta starter

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View of the supply panel swing frame ((Typical layout, not project-specific) For the project specific layout see the electrical drawings.

24VDC battery charger

CERBERUS

Fire monitor unit 9

7 4

5

6

1

2

3

0

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3.1.3

Liquid fuel pumps control panel The liquid fuel pumps panel includes the static frequency converters (SFC), controlling the servo-motors which are coupled to the liquid fuel pumps (Main and Pilot for SoLoNOx turbines). The panel is independent; in case it is used, it is located inside the turbine enclosure near the wall of the control panel room. The 24Vdc and the three-phase 400Vac power supply required for the liquid fuel pumps system is fed by distribution system on the supply panel. The line and motors protections are installed on the supply panel therefore in case of maintenance the power supply must be disconnected in the supply panel. The liquid fuel pump panel is composed of the following main components: • • • •

3.1.3.1

Inlet EMC filters Static frequency converter (SFC) for the Main fuel pump Static frequency converter (SFC) for the Pilot fuel pump (if required) Panel Ventilation fan

Static frequency converter (SFC) The static frequency converter changes the input AC voltage into constant DC voltage, and then via an inverter IGBT, from the DC current, a three phase voltage with variable frequency is produced to power the servo-motor and to turn the pump at the speed required by the turbine control system. An operation module with display is provided and can be used to program, through software, configuration adjustments. This configuration is only to be modified by Turbomach personnel. This configuration is provided and programmed to elaborate a 4-20mA signal transmitted by the turbine control system: the 4-20mA signal corresponds to 0-100 % maximum speed of the servo motor. The speed it is controlled by a closed loop circuit implemented in the SFC software. The speed signal it is produced by a resolver installed on the servo-motor. CAUTION Do not modify the static frequency converter software configuration, modification of the liquid fuel schedules can jeopardize the gas turbine plant.

3.1.3.2

EMC Filter The converter is a non-linear component for the electric current. Therefore the current is not sinusoidal and it contains harmonic components. The harmonic currents cause distortion in the line voltage and EMC interference. To attenuate these distortions one three-phases filter is mounted on the network side. The filter provides an emission limit within the class A. (industrial area).

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View of the liquid fuel pumps Panel Typical layout, not project-specific. (For the project specific layout see the electrical drawings)

Static frequency Converter (SFC) Main liquid fuel pump Static frequency Converter (SFC) Secondary liquid fuel pump (SFC)

Ventilation fan

AC inlet EMC filter

Terminal strip

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3.1.4

Field Bus Modules The field bus modules are used to collect in different areas of the turbine package all relevant signals of the turbine and ancillary equipment. They are set on a skid installed in the same acclimatised frame of the main panels. Any module contains a field bus node that is connected to active digital and analogue input/output terminals or other control cards. The physical state of each input/output connected to the bus module is visible by means of the terminal mounted LED. Each bus node is supplied with two 24 VDC power supplies from the supply panel, one to operate the bus coupler and the other for the power supply of the various equipment. All field bus modules are connected in series with a data-cable fibre optic cable.

MOR

Modules frame configuration

MOR

Liquid fuel module

MOR

Gas module

MOR

Turbine module

MOR

Oil module

MOR

Basement module

Client module

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3.1.4.1

Client Module The client module is used for signal exchange between the gas turbine Control System and the Client's Supervision System. The exchange of signals is made by potential free relay contacts on both sides. The voltage used by the turbine system inputs is 24 V DC. CAUTION The contact rating of the gas turbine control signal relays is 30 VDC/1A or 125 VAC/0.5 A

Typical module layout (For the project specification layout see the electrical drawings)

Field bus module Terminal strip

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3.1.4.2

Baseframe Module The baseframe module contains all the electrical input and output signals of: • • •

Soundproof enclosure Base-frame components Generator

This module is used typically to control: • • • • •

Container temperature Generator winding and bearing temperatures Vibration input signal from the converters Generator exciter current Generator internal automatic fuse failure

Typical module layout (For the project specification layout see the electrical drawings)

Field bus module Terminal strip

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3.1.4.3

Lube Oil Module The lube oil module collects all electrical input and output signals from the lube oil system.

The actuators and field sensors controlled by this module include: Oil tank level • Oil pressure and temperature Oil system filters •

Typical module layout (For the project specification layout see the electrical drawings)

Field bus module Terminal strip

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3.1.4.4

Turbine Module The turbine module collects all input and output signals which are required for controlling and regulating the turbine, with the exception of all the input and output signals directly connected to the fail safe PLC (Process Logic Controller).

The actuators and field sensors controlled by this module include: • • • • • • •

Compressor inlet guide vanes control (IGV) Compressed air discharge valve (bleed valve) Turbine temperatures Turbine speed Turbine bearing temperature Turbine compressor washing system Comburent air- filter obstruction control system

Typical module layout (For the project specification layout see the electrical drawings)

Field bus module Terminal strip

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3.1.4.5

Gas Module The field module for the gas system collects all input and output signals which are required for controlling the distribution of gas fuel. Excepted are those which are directly connected to the fail safe PLC (Process Logic Controller).

The actuators and field sensors controlled by this module include: Gas pressure transmitter Pressure transmitter to control the gas filter obstruction • Gas fuel metering valve The fuel metering valves (main gas valve and pilot gas valve in SoLoNOx machines) are controlled by means of an electronic driver card, which is located in the module. • •

Typical gas module layout

Field bus node with

MOR

(For the project specification layout see the electrical drawings)

electronic driver card Terminals

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3.1.4.6

Liquid Fuel Module The liquid fuel module (for liquid fuel turbines only) contains all input and output signals, which are required for monitoring the liquid fuel supply. Excepted are those which are directly connected to the fail safe PLC (Process Logic Controller).

The field actuators and sensors controlled by this module include: •

Control system for the liquid fuel line filter obstruction

•

Liquid fuel drain tank level and temperature switch

•

Liquid fuel leakage control system

•

Liquid fuel circuit control valves

•

Liquid fuel control signal from and to the SCF pumps panel

Typical layout of the fuel module

Field bus module

MOR

(For the project specification layout see the electrical drawings)

Terminal strip

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3.2

Electrical Systems

3.2.1

Control System The control system can be divided in: service unit, Human Machine Interface (HMI-PC) control unit, Real time (RT PC) The service unit is in charge of commanding, visualizing, monitoring and setting of the whole turbo generator parameters. The control unit governs the gas turbine, the fuel supply, and the functioning sequences of the turbo generators as well as its apparatus, according to the system request and the different needing of the control system..

• •

Each unit is provided with independent industrial PC. The control unit also contains the fieldbus control (Profibus DP), which is connected to the input, and output components that are controlled at the field level (module).

3.2.1.1

System Architecture The system architecture consists essentially of two industrial PC’s the control and service sections, the Profibus DP data transmission system and the fieldbus interface cards located in the modules. For safety-relevant monitoring the failsafe PLC is connected to the fieldbus, and the remote or local control system is connected to the service unit.

3.2.1.1.1.

Fieldbus Master The fieldbus master is a PC plug-in card allocated in the control PC. The card administers (collects and distributes) all available data from the closed-loop control circuit and control system according to the cyclical master-slave process.

3.2.1.1.2.

Data Transmission Data transmission takes place via a twisted, shielded twin-core cable, from the control PC to the failsafe control unit and to the optical bus terminal (OBT). The OBT converts the transmission signal from electrical to optical format. An optical fibre cable connects the OTB to the different acquisition nodes in the cubicle and in the field. The transmission speed used in this plant is 12 Mbits/s.

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3.2.1.2

System Architecture Diagram Control cubicle

* HMI = Human Machine Interface

Control PC - MCU: Control / Regulation

Service PC: HMI* / data storage

Pentium CPU

AMD CPU

Ethernet

Ethernet 1

Fieldbus Master

Ethernet 2 Touch-screen (local screen)

Failsafe PLC

Profibus DP

OBT

Fieldbus BFIB

Enclosure

Optical Bus Terminal

Profibus DP Optical Fiber Cable

Remote control room

Fieldbus BFIB

Remote control PC (HMI* / data storage) Printer (not supplied by TBM)

Fieldbus BFIB Client remote control

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3.2.1.3

Field Bus Structure Diagram The field bus cable routing of the gas turbine plant is shown below:

Control Panel

Auxiliary panel

Industrial PC Real time unit

Failsafe PLC S7 CPU 315F

Optical bus terminal

Bus node BoilerModule (option)

Industrial PC MMI unit Bus node Control panel

Bus node Oil module Bus node Turbine module Bus node Liquid fuel mod. Bus node Gas module

Supply Panel Bus node Supply panel

Bus node Baseframe mod. Bus node Client module

Bus node Roof module

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3.2.2

Back-up Safety System During operation a safety back-up system protects the entire turbine plant from possible damage resulting from dangerous turbine and ancillary equipment malfunctions. Furthermore, the system evaluates sensor signals from the gas detector and the central fire detection system. A failsafe PLC type Siemens S5-95F is used for this purpose.

3.2.2.1

Failsafe PLC The failsafe PLC employed carries out all safety checks relating to personnel or mechanical protection. The device works independently from the turbine control system and puts automatically the entire turbogenerator to a predefined safe state in case of inadmissible operating parameters. The failsafe PLC software is programmed in STEP 5.

3.2.2.2

Back-up System shut down Criteria The STEP 5 program is divided into operational blocks. One block carries out a routine check every 20 ms in case of activation of one of following digital inputs. Shutdown of the turbine if immediately activated.

3.2.2.2.1.

Direct shut down criteria based on a 20 ms routine check: • • • • • • • • • • • • • • • •

Fire alarm Boiler safety chain alarm Exhaust gas back pressure too high PS5201 Instrument air pressure too low PS0402 Lubricating oil pressure too low PS3031 Turbine under-speed ST1801 Turbine over-speed ST1801 Generator protections External EMERGENCY SHUTDOWN (plant, remote workstation) Internal EMERGENCY SHUTDOWN SB0110 (turbine container, control panels) Main control PC Watch-dog fail Disconnection of essential power supply automatic fuses Fuel valves relays chain control Gas pressure too low PS2007 Gas pressure too high PS2008 Gas leakage > 40% LEL DT2050

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3.2.2.2.2.

Sequences related shut down criteria: Another block carries out sequences related checks and a shutdown of the turbine if necessary:

•

Flame monitoring (flame out) TT1825 Ignition time overrun Turbine start-up time overrun.

•

Failure of gas fuel valve check PS2017 / PS2018

• •

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3.2.2.3

Safe State of the Machine Each shut down criteria activated in the back-up system will produce an immediate shutdown of the plant, controlling the main fuel valve and equipment as follow (safe state): • • • • • • • •

3.2.2.4

Ignition spark-plug K 1010 off Generator circuit breaker open Primary gas quick-action stop valve MV 2001 closed Secondary gas quick-action stop valve MV 2002 closed Gas purge valve MV 2010 opened Liquid fuel pump M2121 and M2131 (if installed) stopped Primary liquid fuel quick-action stop valve MV 2101 closed Secondary liquid fuel quick-action stop valve MV 2102 closed

Flame Monitoring (flame out) In Solar gas turbines it is not possible to use direct flame detectors as used, for example, with burners. For this reason, two indirect measurements are used for checking the flame out : the temperature and the speed. For measuring the turbine temperature T5, two signals coming from two thermocouples, wired redundantly to sub-units A and B, are used. For the speed measurement two speed pick-ups, also wired redundantly to sub-units A and B, are used. These measurements are independent of regulation tasks. A decrease in temperature T5 below 204°C or in speed below 90% in anytime between acceleration and stop sequence, cause a FLAME OUT shutdown.

3.2.2.5

Turbine ignition supervision During the start-up phase the flame ignition of the turbine is monitored. For this purpose the temperature T5 is memorized, before the ignition sequence. When the spark plug is excited and the fuel is introduced in the ignition torch a timer is started. Within a time according the burned fuel (approx. 20 seconds), a predefined temperature T5 increase (typical 60°C) must be detected, and if the temperature of 204°C is not achieved, it is considered as ignition failure and the turbine shutdown activated. If the start is aborted, the quantity of fuel flowing into the gas turbine is very small because during ignition the fuel flow is set to the minimum value. During this time the gas turbine compressor delivers enough air flow, so that this small quantity of fuel is evacuated via the exhaust system and no explosive mixture can remain in the turbine.

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3.2.2.6

Turbine start-up supervision (acceleration time) Following flame stabilization, (approx. 20 seconds) the spark plug is deactivated and a second timer is activated. The control system regulates the combustion fuel so that the desired temperature is reached (>204°C) and a constant acceleration to 66% of nominal speed is obtained. This process has a duration of maximum 240 seconds for T70CED and Titan turbines and 120 for Mars turbines. At 66% of nominal speed, the starter motor is disengaged and the turbine accelerates autonomously to 100% of nominal speed. This acceleration process has to be carried out within a limited and monitored time interval. The start-up time supervision consists in checking the time needed to reach at first 66% and then 95% of the nominal speed. If these two start-up acceleration times are not met, it is considered as failure and the turbine shutdown activated.

3.2.2.7

Boiler Protection The safety chain alarm of the exhaust heat recovery system must be connected to the turbine safety control, producing a turbine shutdown in case of critical boiler situation. All protection criteria of the waste heat recovery system (boiler or others) must be fulfilled before any turbine start, paying special attention to the exhaust duct. When the crank speed has been reached, a signal is sent to the boiler control system to begin ventilation of the boiler and associated ducting, comprising the by-pass duct if available. After the purging time, specified by the concerning legislation, which is in function of the air volume to evacuate from the boiler, a signal is sent to the turbine control system to enable the fuel ignition. NOTE The duration of the ventilation of the combustion gas duct must be performed and controlled by the boiler control itself.

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3.2.2.8

Data Exchange with Control System The bus connection between the safety back-up system and the control PC system is a stable connection although it is not to be considered a safe and fast connection. Only data necessary for the normal operation of the plant are exchanged via the bus connection. Since the safety back-up system controls the safety functions autonomously, this data transmission circuit is not necessary in the event of a fault. It is anyway advisable that the safety system does not have to wait the bus transmission data in case of PC control system failure or bus communication failure. Four hardwired lines, installed with direct cabling, between PC control system and safety system provides an immediate link between them. CAUTION The hardware connections between the PC and the safety system do not contain criteria relating to operating personnel’s safety; they are exclusively for the safety of the machinery.

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3.2.3

Emergency Lube Oil Pump The lube pump/pumps are activated when the turbine is running or when the main lubrification is required. Furthermore, the bearings and the oil circuit have to be lubrified before (pre-lubrificatin sequence) and after (post-lubrification sequence) the turbine functioning. The lube oil pressure monitoring is always active during the lubrification process, in order to detect any dangerous drop in the oil pressure. If this happens, The PC control unit transmits the emergency lube pump activation command. In addition to the PC control system the plant is equipped with a further independent lowpressure transmitter, which is connected to the redundant safety backup system. This pressure transmitter checks the lube oil pressure and switches the emergency pump, in parallel with the control system. The DC emergency pump is automatically activated in case the lube oil pressure drops. The pump remote control switch is “normally switched off” for security reasons. This means that the emergency pump activates automatically if the control or security systems are off, or in case of damage in the field bus unit. In case of fire, a selector on the supply line allows shutting down the pump if the lube oil leakage feeds the fire. The pump can be stopped only after having detected that the oil presence is making the situation worst. Stopping the pump before the ending of the post-lubrification process can seriously damage the bearings. In case of failure in the control system, the DC emergency lubrification pump starts automatically. If this occurs, operator has to disconnect the pump through the proper selector, before the battery discharges completely

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3.3

Fire detection and extinguishing system An automatic, electronically controlled fire detection system for the turbogenerator enclosure protection is provided. The system is monitored and operated from the fire monitor unit, and is equipped with CO2 extinguishing system. The installation is designed, executed and certified in accordance with local regulations. The fire monitoring and extinguishing system detects flames inside the package and, after a preset time delay, releases extinguishing agent (CO2) that will fill the enclosure. WARNING In case of fire alarm a personnel or equipment risk persists. The measures to be taken by the operator in case of fire alarms are explained in the chapter 1

3.3.1

Fire system’s equipment The fire monitoring and extinguishing system consists of following main components and parts: Fire monitor unit • • • • • • •

Electronic control and monitoring unit with micropressor. One protective zone with cross-linked protection line. Additionally channels for auxiliary control line (manual and smoke detectors) Front panel with control buttons and display. 220VAC supply with 24VDC internal battery. Manual fire alarm button on the front panel. Outdoor weather-proof enclosure (optional)

Equipment’s in the control panel’ s area: •

Smoke detector DT0125

Equipment’s in the container: •

Infrared ray detectors RT0210 and RT0220 (cross linked line)

Equipment’s outside the container: • • •

Manual release push-button SB0302, alongside the enclosure Warning horn and flashing light signals HAL0305, above the inspection door Position switch GS0300 for the inspection door.

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Extinguishing system: • • • • • • • • •

3.3.2

CO2 bottles set B0312 filled for one extinguishing action. CO2 odoriser bottle B0315 Pilot bottle B3011 Pressure gauge with pressure switch PS10311 upon the pilot bottle Weight switches for CO2 bottle leakage monitoring WS0312 Extinguishing agent release solenoid valve MV0311 Pressure switch PS0316 for the CO2 release confirmation. Distribution piping, and spray nozzles. CO2 bottles protection cubicleFF0310 (optional)

Fire system operation The fire fighting system is designed to detect and extinguish a fire propagating in the enclosure. Fires, such as fuel fires or lube oil fires, are quickly extinguished by flooding the area with an inert gas. The inert atmosphere is created by discharging a high concentration of CO2 into the container. To accomplish this, the enclosure ventilation system is shut-down, the extinguishing agent is discharged into the enclosure and the ventilation shutters are closed.. The fire detection system is equipped with a DC emergency power supply and remains active even in the event of 220 VAC supply failure. Once armed, normal system activation is controlled by the fire detection system; the extinguishing agent can also be released any time by pressing the push button in case of an emergency The fire extinguishing buttons are mounted outside the container.To operate, break the glass and press the button. In order to reset the button, replace the glass cover. The possible flame inside the enclosure is monitored by the infrared flame detectors. The infrared flame detector, with highly sensitive element reacts rapidly to all flaming fire in which carbonaceous materials are burnt, such as wood, plastic, alcohol, natural gas, petroleum products etc. A pyro-electric sensor evaluates a specific wavelength of the hot carbon dioxide emitted by the flame. The detector achieves high immunity to deceptive phenomena by means of a second pyro-electric sensor which operates on another wavelength. Signal from both sensors are correlated which enables clear differentiation between flame radiation and deceptive phenomena. Thus the detector is widely insensitive to artificial light, sunlight, and all kinds of heat, ultraviolet, x-ray, and gamma radiation. As soon as a detector responds the control unit actuates a preventive warning signal. Acoustic and lighting warning panel is provided outside the enclosure above the maintenance door for operator's alerting. When both detectors respond simultaneously, or if a manual button is pressed, the control unit gives the extinguishing command. After a delay, a valve is actuated to release the extinguishing agent. The main discharge valve is installed on the first CO2 battery cylinder, producing when energised the cascade opening of all the cylinder discharge valves of the set. For personnel safety reason, an odorant stored in a bottle, connected to the piping and actuated by the discharge pressure, may be mixed with the odourless CO2 ,while discharging into the enclosure. The discharged CO2 is flushed to the protected area through spray nozzles. The spray nozzles are designed to distribute the gas smoothly and evenly on the enclosure. The nozzles are sized for discharging the whole extinguishing agent in about 60 seconds. In the event of loss of extinguishing agent, the weight switch of the leaking cylinder in question transmits an alarm signal to the fire detection system.

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Only when allowed by local standards: Container door The inspection door, located at the longitudinal side of the container and equipped with handle, is provided with limit switch that locks the automatic discharge of the extinguishing agent if the door is open, for this reason the inspection door must be maintained closed. For maintenance purpose a specific description is provided on the fire control unit.

3.3.2.1

Operational logic of the automatic detection The signals of the infrared sensors, connected on the two automatic channels of the fire monitor, are processed by the following logic:

First channel

Second channel

Alarm signal

OK

OK

none

not OK

OK

fault

OK

not OK

fault

not OK

not OK

fault

not OK

fire detected

fault, pre-alarm, fire alarm

fire detected

not OK

fault, pre-alarm, fire alarm

fire detected

OK

pre-alarm

OK

fire detected

pre-alarm

fire detected

fire detected

pre-alarm, fire alarm

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3.3.2.2

Fire monitoring alarms The fire monitoring system provides, for the turbine control system, the following main alarms:

3.3.2.2.1.

Fire system failure Monitoring or extinguishing system defects, such as sensor failure, line interruption, measurement unit failures or supply failure, container’s door opening (in case of plants equipped with end-switch), activates this alarm. • • • •

3.3.2.2.2.

Indicates a fault of the monitoring system or parts of it. The control system signals it as system error (ER). This alarm doesn’t cause any automatic action. Leakage of the extinguishing agent (control of the bottles)

Fire warning This alarm is activated when one out of two automatic fire sensors detects a fire. The alarm is announced by a continuous sound emitted by the beeper present in the enclosure and by a warning signal in the main control system. Indication given by light diodes is also visible on the front panel of the fire detection monitoring system and the display indicates the affected area. • •

3.3.2.2.3.

Indicates that one automatic fire sensor detects a fire. The control system signals it as system warning (WR).

Fire alarm This alarm is activated when both automatic sensors detect a fire. Activation is also possible via manual push buttons installed on the enclosure. The alarm is announced by an intermittent sound emitted by the beeper present in the enclosure and by an alarm signal in the main control system. Indication given by light diodes is also visible on the front panel of the fire detection monitoring system The gas turbine unit is instantly shut down, in parallel the extinguishing sequence is activated. Indicates that two sensors (infra-red) detect a fire, or The manual fire release buttons are actuated. The control system signals it as alarm (SD), producing a turbine shutdown.

• •

3.3.2.2.4.

Smoke alarm Indicates a smoke presence on the control and the supply panels. The control system signals it as system warning (WR) • This alarm doesn’t cause any automatic action. Consider also the installation of a fire extinguishing equipment specific for fire generated by electrical apparatus near the electrical panels container. •

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3.4

Gas monitor system

3.4.1

Description of the gas monitor system The unit is equipped with a gas leakage monitoring system, that covers the enclosure internal area. The gas detection system is designed to continuously monitor the explosive level of the atmosphere within the enclosure. The system consists of a gas sensor assembly installed in the container. The detection sensor it is connected to the safety back-up PLC (Process Logic Controller), which provides the monitoring. The safety system triggers the system fault, warning and alarm signals. The processed value is in percent of the LEL (lower explosion limit) : typically 10% of LEL for warning and 20% of LEL for alarm The 100% LEL indication means the gas has reached a concentration where the gas/air mixture becomes sufficient to produce an explosion (= 5% vol. CH4 in air). If the gas concentration in the container increases the pre-selected levels, visual warnings, alarms, and safety sequence, including turbine shutdown, are initiated to protect personnel and equipment. WARNING In case of gas leakage detection alarm an explosion risk persists. The measures to be taken by the operator in case of gas danger are explained in the chapter 4 “Description of the operating sequences”.

3.4.1.1

Gas monitor alarms The gas monitoring system provides, for the turbine control system, the following main alarms:

3.4.1.1.1.

Gas monitor system failure Indicates system or part of it out of service. • A system fault message is issued (SD). • The gas-turbine shut-down and a dedicated safety sequence is activated. Monitoring system failure such as sensor failure, line interruption, measurement unit breakdown or supply failure, activates this alarm. Due to the high danger of the gas leakage within the enclosure, the monitoring is performed by the safety back-up PLC, working in the context of a redundancy control. For this reason in case of one channel failure a shutdown for discrepancy is activated. •

3.4.1.1.2.

Gas leakage warning • • •

Indicates a gas concentration in the package above 10% LEL and below 20 % LEL. The control system signals this as a warning (WR). Fans and air gates will be activated, if not already activated, to ensure gas evacuation

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3.4.1.1.3.

Gas leakage alarm • • • •

Indicates a gas concentration in the package above 20 % LEL. The control system signals this as alarm (SD) The unit is shut-down and a dedicated safety sequence is activated Fans and air gates will be activated, if not already activated, to ensure gas evacuation

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