Alison KB501 Upgrade | Offshore, Gabon Perenco production activity in Gabon began in 1992 with the acquisition of mature fields off Port-Gentil, with 8,000 barrels of oil produced daily. 26 years later, the annual average production reached 90,000 boepd and 50 million cubic feet of natural gas in 2017. This growth was supported by the continuous development of mature fields, a balanced acquisition strategy and several exploration successes.
Perenco Gabon operates oil and gas licenses both offshore and onshore. In addition to this oil and gas portfolio, there are two floating offshore storage and offloading units (FSO, Floating storage and offloading) offshore. For over 10 years, They has been providing natural gas to the power stations of Libreville and Port-Gentil. The gas is produced onshore, processed in accordance with the current specifications and delivered under pressure using a 450 km pipeline.
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THE PROBLEM
The existing control system, AVR, fuel system and fire and gas systems had become obsolete with spare parts availability no longer guaranteed. The Units reliability had dropped and was becoming unserviceable.
THE SOLUTION
Turbine Controls Ltd were contracted to provide a solution that would use parts which would not become obsolete for the next couple of decades and meet the required start reliability requirement. The retrofit consisted of:
A new fuel control governor and automatic sequencer control system which was implemented using an Allen Bradley ControlLogix 5000 PLC based system.
The fuel control system HP fuel pumps were removed and replaced with the TCL Posiflow® off engine liquid fuel system, using a variable speed electrically driven gear fuel pump to modulate the fuel to the KB501 engines.
An CGCM AVR system complete with protection relays.
New HMI displays that are built around the way an engineer functions in a control room environment.
TCL were responsible for the design, manufacture, installation and commissioning for all equipment supplied. All software for the PLC and SCADA systems was written and tested by TCL engineers at our Leicester HQ.
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Grid Compliance | Taylors Lane, Uniper UK Taylors Lane Power Plant was opened in 1979 by the Central Electricity Generating Board. It’s now operated by Uniper. The plant can be operated remotely from Enfield Power Station or on site. There are two generator units fired on gas-oil with a capacity of 132 MW. Each unit uses 4 gas generators derived from the Rolls-Royce Olympus jet engine.
Taylors Lane power station is operated by Uniper and is located in London near Wembley Stadium. It consists of two DEO2 (double ended twin RR Olympus engines) gas turbines operated in open cycle mode, developing 70MW each. The turbines were originally installed in the 1970’s by GEC Gas Turbines and provide electrical grid support in times of peak demand.
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Problem:
The gas turbine governor system was upgraded by TCL in 2010; however, this didn’t include upgrading their Dial-A-Megawatt controller from the 1980’s. This system would allow the employee’s at Enfield to remotely dial there MW output at Taylor’s Lane.
The Dial-A-Megawatt controller was outdated; this was causing the MW output value at Enfield’s remote monitoring system to be incorrect.
Solution:
TCL were contacted by the engineer at Taylor’s Lane to improve the reliability of the of the remote monitoring system’s feature to dial a megawatt setpoint.
Once our engineer was on site they looked at the issue and quickly came up with a solution. Rather than going via several signal cables through the old dial-a-megawatt controller, we took the inputted value from the remote monitoring system and sent it into the TCL PLC. This would allow the PLC to calculate the fuel adjustments needed and either raise or lower the speed of the gas turbine.
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Low Voltage Switchgear | CEC, Zambia Copperbelt Energy Corporation (CEC), Zambia owns and operates a number of Avon powered standby generators which provide emergency power to local copper mines in the event of loss of supply from the national distribution network. These gas turbines are also used for peak load control and it is therefore essential that these sets are available for operation and have high start reliability.
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THE PROBLEM
The gas turbine control system had been replaced by TCL in 2004, however this project did not include upgrading the low voltage switchgear or MCC (motor control centre) boards. This switchgear had become unreliable and was suffering from obsolescence issues associated with obtaining spare parts. In particular, the DC switchgear uses 120 Vdc supplies and the heavy‐duty contactors required for switching this voltage have become very difficult to source.
THE SOLUTION
TCL were contracted by CEC to replace the existing MCC boards with new AC and DC switchgear designed to the latest standards and employing the latest technology. The new boards were designed to have the same footprint as the old switchgear to simplify the installation and enable the existing field cables to be re‐used. A form 4 type 2 construction was used to allow maintenance of individual drives, whilst others are still live.
The switchgear replicated all the existing drives. The AC boards utilised direct‐on‐line starters, whilst the DC boards used soft‐ starters based on the TCL SmartStart technology. The TCL SmartStart was also supplied for the RR Avon starter which has been installed on many RR Avon and Olympus installations. The original DC starters used resistors to limit the starting current. This method not only relies on the use of 110 Vdc contactors but also puts large electrical and mechanical stresses on the drive train as the resistors are switched out of circuit. Using the TCL SmartStart not only means that 110 VDC contactors are no longer required but also the stresses on the drive components are greatly reduced.
Remote I/O, PLC modules were fitted in the boards to provide the interface with the main control system. This included starting contacts and feedback from the drives for monitoring and fault finding. The remote I/O modules were connected together on a local Ethernet communications ring which will be connected to the main gas turbine control system at site.
The switchgear was designed and manufactured in our Leicester works and was subjected to a thorough works test. Each drive was functionally tested using suitable electric motors which allowed full and part load conditions to be simulated.
All switchgear is designed and manufactured to BS EN 61439.
As with the supply of all control equipment TCL provide a very flexible approach to the design. The switchgear is very much designed to the requirements of each client. Amongst the many options that can be accommodated are:
Form factor, depending upon maintenance requirements
Pull‐out or fixed drawers
Soft‐start or DOL
Serial communications, Ethernet, Modbus etc.
Intelligent starters
TC are able to provide LV switchgear, up to 600 Vac and 240 Vdc. This can be designed to replace existing boards or for new installations.
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Steam Turbine Control System | Coventry, UK Coventry and Solihull Waste Disposal Company Ltd (CSWDC) operate a waste processing plant in Coventry. Some of the waste is burnt and the resultant heat is used to produce steam which in turn is used to generate electricity through two steam turbines rated at 5MWe and 12MWe. The control system of the 5 MW steam turbine was becoming increasingly unreliable resulting in a number of unscheduled shutdowns.
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THE PROBLEM
The key requirement of the steam turbines are to run continuously for long periods between shutdowns. The waste incinerators can only operate if there is place to process the produced steam, reduce the pressure and temperature. Although this can also be done via a steam bypass let down system this will result in a loss of generation revenue.
The existing control system fitted to the steam turbine consisted of:
Simplex steam turbine governor and control PLC, based on GE Fanuc hardware
TMR steam turbine protection system, including overspeed trip
Allen Bradley PLC5 air cooled condenser (ACC) and steam bypass control system
Local screen based HMI
Bently Nevada turbine supervisory
Alstom AVR and generator protection
The existing control equipment was reaching the end of its supported life‐cycle with more regular failures and spare parts had become harder to source. In addition fault diagnosis was awkward due to the limited visibility of the control algorithms in the PLC systems. The result was numerous service calls from the OEM for even minor faults and setpoint changes.
CSWDC employed TCL to design and install a replacement steam turbine control and protection system.
THE SOLUTION
The steam turbine control system was replaced with a modern state of the art microprocessor based system. In this case the Allen Bradley ControlLogix5000 range of PLC equipment was selected. This was configured in a duty/standby processor configuration with ControlNet communications for key control signals.
The steam turbine governor controls were replaced with a Woodward 505 controller.
The ACC and bypass controls were also replaced with a ControlLogix5000 PLC configured in a simplex processor configuration.
The Steam turbine protection system was replaced with a duplex plant safety system based on the Pilz range of machinery protection relays.
The following equipment was removed:
ACC steam bypass PLC5 controller
Steam turbine control and governing system, GE Fanuc
TMR Steam turbine protection system, GE Fanuc
Generator protection relay
Automatic voltage regulator, Alstom Digirec
Bently Nevada turbine supervisory monitor
The following equipment was installed:
Simplex ControlLogix5000 PLC for ACC and steam turbine bypass control
Duplex ControlLogix5000 PLC for steam turbine control
Woodward 505 for steam turbine governor control
Dual/redundant plant safety system (PSS), Pilz safety relays
Vibrometer turbine supervisory monitor
Jaquet overspeed trip monitor
Basler DECS250 duty/standby AVR
Generator protection relay P346 – MICOM
This was a turnkey project and TCL were responsible for the design, testing and installation. One of the key elements of the design was the configuration and integration of all the different parts of the complete system, including AVR, Woodward 505 and the generator protection relay. This also involved configuring a number of different communications protocols in order to pass signals to and from the different elements of the hardware.
The equipment was installed in two phases. Firstly the ACC and steam turbine bypass PLC5 controls were replaced with an Allen Bradley ControlLogix5000 Based system. During the second outage the steam turbine control and protection system was installed. At the same time the steam bypass control was moved to the Steam turbine control system, leaving the previously installed Controllogix PLC as a back‐up in case of a steam turbine outage. This required careful planning and execution of the installation and commissioning in order to limit the bypass system outage to a minimum and also to ensure plant and personnel safety.
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Static Excitation System | CEC, Zambia Copperbelt Energy Corporation operate a twin RR Avon gas turbine generator (EA2) at their copper mine in Luano, Zambia. The unit operates in simple cycle mode and is used for grid support and for emergency generation to the mine in the event of grid supply failure. The gas turbine was installed by GEC in the mid 1970s.
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THE PROBLEM
The original rotating excitation system consisted of:
Permanent magnet generator
Pilot exciter
Main exciter
Rotating diode and resistor assembly
Single channel AVR, maximum current output 15A
The exciter had developed a vibration problem which could not be cured despite repeated rebalancing exercises. In addition spare parts for the above equipment had become difficult to source and expensive. A decision was made to replace the rotating system with a static excitation system and CEC employed TCL to carry out this conversion.
THE SOLUTION
A new slip‐ring assembly was designed to fit onto the generator main shaft mating with the existing main exciter coupling. The output connections of the slip rings connected to the tails of the generator rotor field winding.
A slip‐ring pedestal was designed and constructed to house the slip‐ rings and provide cable connections for the field cables from the AVR output.
An excitation transformer was installed to provide the power for the AVR from the 11kV generator output.
A Basler DECS200 based AVR was designed and installed to provide the excitation current direct to the generator rotor, via the new slip‐ring assembly. The new AVR was rated at 450A full load current.
The following equipment was removed:
Permanent magnet generator
Pilot exciter
Main exciter
Rotating diode and resistor assembly
Automatic voltage regulator
The following equipment was installed:
Rotating slip‐ring assembly
Slip‐ring assembly pedestal
Static automatic voltage regulator, max current 450A
Excitation transformer
The completed installation was tested in various modes of operation, including parallel and island modes, to ensure compliance with the dynamic response characteristic requirements
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Control System Retrofit | Saudi Electricity Company, Various Plants Saudi Electricity Company (SEC) operates a number of GEC RR Avon powered mobile gas generators at various locations within the Kingdom of Saudi Arabia. These are moved to locations where there is a power shortage and are used primarily during periods of peak demand in the summer months.
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The Problem
The key requirements of the mobile generators are to reach full load in a short time and run reliably for the peak demand period.
The existing fuel control system fitted to the RR Avon mobile gas turbine consists of:
Analogue electronic governor interfacing with an on‐ engine hydro‐mechanical fuel control unit.
Relay based sequence control system.
The on‐engine fuel control components are seen as major source of system unreliability. This equipment is built to aerospace standards and is very susceptible to the aggressive environment of an industrial application, particularly in terms of fuel quality. Hydro‐mechanical equipment is also notoriously difficult to maintain and troubleshoot and, being of an aero‐space standard, it is also very expensive to repair.
The analogue electronic governor and relay based sequencer were also prone to frequent breakdown. The system has very limited diagnostics which has the effect of extending the fault finding process. The problems with the control and fuel system meant that the generators could not be relied on to generate when required.
SEC employed TCL to supply a replacement control system because of their past experience with the RR Avon and their ability to supply a tried and tested off‐engine fuel system.
The Solution
Replace the gas turbine fuel governor system with modern state of the art equipment that is more suited to the requirements of an industrial application.
The heart of the new control system is the Posiflow off engine liquid fuel which has been installed on numerous similar installations. This system uses a positive displacement gear pump driven at a variable speed by an electric motor and frequency converter. The gear pump is very rugged and ideally suited to an aggressive industrial environment.
The following equipment was removed:
Analogue electronic Governor
On‐engine fuel control system
Batteries and battery charger
The following equipment was installed:
Turbine Controls TC95‐03 micro‐processor based governor
TCL Posiflow fuel system
Replacement batteries and battery charger
The equipment had to be compatible with retained equipment and adhere to the overall control system philosophy devised by Rolls‐Royce and GEC.
TCL have modified four GEC mobile generators in Saudi Arabia at various locations including Ar‐Ar and Al‐Qurayat power stations.
Following successful installation and commissioning of the equipment the gas turbine start and operating reliability has significantly improved.
Note: The TC95‐03 Governor system has now been replaced with the TC41‐GG gas turbine governor system.
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Control System Retrofit | Uniper Energy, Sweden E-ON operates a twin Olympus gas turbine generator (EO2) at their Karlshamn power plant in southern Sweden. The unit operates in simple cycle mode and is used for grid support and for black start of the main generators at the power station. The key requirements of the gas turbine are to start reliably at short notice following long periods of being shutdown. The gas turbine was installed by GEC in the mid 1970s.
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THE PROBLEM
The key requirements of the gas turbine to start reliably at short notice following long periods of being shutdown.
The existing control system fitted to the gas turbine consists of:
Off‐engine servo valve controlling the swash angle of the on engine HP fuel pumps
Relay based sequence control system.
Analogue electronic AVR
The off‐engine fuel control components were a major source of system unreliability. This equipment included a delicate hydraulic actuator which was susceptible to the aggressive environment of an industrial application, particularly in terms of fuel quality. Hydro‐mechanical equipment is notoriously difficult to maintain and troubleshoot and being of an aero‐space standard it is also very expensive to repair.
The analogue electronic AVR and relay based sequencer were also prone to frequent breakdown. The system had very limited diagnostics which had the effect of extending the fault finding process. Ever increasing maintenance costs were being witnessed in order to achieve the start reliability.
E‐ON employed TCL to supply a replacement control system because of their past experience with the RR Olympus and their ability to supply a tried and tested off‐engine fuel system.
THE SOLUTION
Replace the gas turbine control system with a modern state of the art microprocessor based system. In this case the Allen Bradley ControlLogix5000 range of PLC equipment was selected. This was configured in a simplex processor configuration with redundant ControlNet communications for key control signals. The new PLC replaced the existing off‐engine fuel control and the relay based sequencer control equipment.
The on‐engine fuel pumps were removed and replaced with the Posiflow off engine liquid fuel system which has been installed on numerous similar installations by TCL. This system uses a positive displacement gear pump driven at a variable speed by an electric motor and frequency converter. The gear pump is very rugged and ideally suited to an aggressive industrial environment.
The existing analogue electronic AVR was replaced with a digital unit, in this case the Basler DECS200N in a dual redundant configuration.
The following equipment was removed:
Hydro/electric fuel control
Unit control panels
On‐engine fuel HP fuel pumps
DC MCC boards
Generator protection
The following equipment was installed:
New control panel suite
TCL Posiflow fuel system
Dual channel AVR DECS200N
DC MCC boards
Generator protection Siemens dual
redundant system
The equipment had to be compatible with retained equipment and adhere to the overall control system philosophy devised by Rolls‐Royce and GEC.
Following successful installation and commissioning of the equipment the gas turbine start and operating reliability has significantly improved.
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Control System Retrofit | RWE, UK Cowes Power Station operates two 70 MW diesel fired simple cycle Olympus gas turbines for peak load and synchronous compensation duties. The units were originally installed in 1982 by Rolls Royce. Both units had been retrofitted with Woodward Netcon governors in the early 1990s.
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THE PROBLEM
The Netcon governors had become obsolete with spare parts availability no longer guaranteed. The Units reliability had dropped below the 95% required by RWE’s contract with National Grid.
Different settings being required by the governors between summer and winter operation to achieve engine light off. The main sources of unreliability were readily identified as:
The electro‐mechanical fuel control system and on engine fuel pumps.
Automatic sequencing control.
Governor set‐up
THE SOLUTION
Turbine Controls Ltd were contracted to provide a solution that would use parts which would not become obsolete for the next 20 years or better and meet the required start reliability of > 95%. The control system retrofit consisted of:
A new fuel control governor and automatic sequencer control system which was implemented using an Allen Bradley ControlLogix 5000 PLC based system.
The Olympus off engine fuel control system on‐engine HP fuel pumps were removed and replaced with the TCL Posiflow® off engine liquid fuel system, using a variable speed electrically driven gear fuel pump to modulate the fuel to the Olympus engines.
Dual redundant SCADA system providing both local and remote control and monitoring. The remote control and monitoring being done at Fawley Power Station on the mainland. The SCADA system also provides a detailed alarm reporting and diagnostic tools to aid in fault finding.
TCL were responsible for the design, manufacture, installation and commissioning for all equipment supplied. All software for the PLC and SCADA systems was written and tested by TCL engineers at our Leicester HQ.
After the retrofit different settings were no longer required for summer and winter operation and both units now meet >95% reliability required.
TCL continue to provide technical assistance and support to our customer at Cowes Power Station.
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