LINDSEY OIL REFINERY LIMITED, UK UTILITIES INTEGRATED
MONITORING AND CONTROL SYSTEM
Introduction
The goal of this project was to develop and build
this system in order to integrate the control of the electric
utility with the other production islands control of the refinery.
As a result, the following achievements were sought after:
- Increase of the reliability;
- Increase of the efficiency;
- Electric Power Consumption and Production expenditures optimization;
- Electricity Quality improvement, in regard to internal and National
Grid requirements;
- Increase of the efficiency of the operators actions;
- Maximum efficient follow up of the operative personnel;
- Maximum operative personnel protection and improper operator
actions effect minimizing;
- Process and personnel actions follow up data base consolidation
in order to achieve integrated solution of the tasks of the Electric
Utilities Management, including online assessment of the equipment
residual recourses and flexible maintenance planning. The last
function was planned to be implemented in the near future.
Background
The electrical network at Lindsey Oil Refinery
was operated and monitored from two main hardwired panels located
within the Utilities Control Room:
- ‘AEI’ Panel
- ‘CHP’ Panel.
The AEI panel was over thirty years old and mainly
comprised control and current monitoring of 11kV and 415V circuit
breakers within the Utilities Substation. It also provided:
- Manual synchronization of generators 8G-1&2;
- Power measurements ;
- Alarm handling;
- Speed governor control;
- Voltage regulator control;
- Disturbance recording.
The CHP panel was more modern and performed
similar duties to the AEI panel, but handling one 40MW gas turbine
generator (9G-1) and monitored and controled upstream Yorkshire
Electricity & Inoggy supplies to the LOR electrical network.
Hardwired contacts at the CHP panel, initialized
automatic plant wide load shedding. Current monitoring at the
AEI panel allowed selective plant load shedding to take place.
To the top of the page
THE TASKS, THE FULFILLEMENT OF WHICH IT ENABLED
THE GOAL TO BE ACHIEVED
- To transfer existing electrical control functions
from the Utilities Control Room to a Centralized Control Room
by means of the objectives:
- To provide facilities to monitor and control
electrical plant remotely from a central location.
- To allow the plant to overcome the problems and constraints
associated with thirty-year-old technology and equipment;
- To take advantage of current technology in providing the required
flexibility and reliability for the new system to be easily modified,
developed and integrated with other plant systems;
- To simplify the existing relay panels by deriving control from
microprocessor based equipment and overcoming maintenance problems
associated with aging relay logic;
- The contain high capacity for future development and expansion
and the ability to interrogate for errors and provide effective
man machine interface. The system will also provide increased
ease for faultfinding and reduced breakdown time.
FEATURES SPECIFICATION
Introduction
The system’s basic functions are:
- Provision of a ‘soft’ control system to monitor
and control the main 11,000 volt electrical network;
- Provide automatic and manual control and synchronization of
existing 11kV generators 8G-1 and 8G-2;
- Interface with the electrical power system via dedicated transducers
for system analysis and trending.;
- Replicate the existing CHP system hardwired controls to screen
based mimics. Interface with the existing Burner Management System
panel;
- Control and monitoring of 3.3kV and 415V Utilities switchboards;
- Monitor the Central Control Room building internal distribution
equipment;
- Implement optimized load shedding at emergency situations;
- Interface with the existing Plant Steam Production Control Subsystem;
System overview
The low layer of the system is based on two triple
modular redundant TRICON 9.6 controllers. The control function
is distributed on the principle, which allows the system to remain
“alive” if one of the controllers completely fails.
Such failure practically is impossible due to the fact that the
controllers have very high availability , because of their triple
redundancy. Field records of 250 years MTBF are available.
Supply Power Quality Monitoring
General requirements for switchboards 1A, 2B,
3A and 4B are to analyze the Power Quality of the system in terms
of disturbances, i.e. the system provides information on:
· Supply interruptions
· Voltage sag & swell
· Harmonics
· Transients
· Noise
· Poor power factor
· Crest factor
Waveforms are displayed on a dedicated mimic
page selected by the operator.
Synchronisation
Synchronisation is automatic and manual. The
two 11kV generators 8G-1 and 8G-2are treated as individual units
with hardware and software design reflecting this philosophy.
The synchronization function was raised as one of the most important
, because it has to be done frequently. The reason of that was
the demand for the Refinery Electric Power System to be flexible
and efficient.
Generating from the controllers correction signals
to the voltage and speed is the synchronization procedure, done
by regulating system of the power supply being synchronized.
The permissive for this procedure to start is the availability
of a set of parameters.
The check of availability if these parameters is done by means
of software and hardware redundancy.
If some signals are missing the procedure starts again. After
three unsuccessful attempts, the system generates alarm signal.
High accuracy of synchronization was achieved,
which brings high quality and long life of the equipment. Low
qualified personnel can initiate this procedure.
Six synchronizing references will be necessary
to fulfill total system synchronization. These are shown on the
attached sketch URS_FIG02 and listed below:
1) LOR Incomer 1
2) Bus Bars 1A
3) Generator 8G-1
4) LOR Incomer 2
5) Bus Bar 2B
6) Generator 8G-2
To the top of the page
Operation following Synchronization
Background
Turbo-generators 8G-1 and 8G-2 have two modes
of control; Speed control and Back Pressure Control. On speed
control the objective is to maintain a constant MW output from
the generators. This results in a constant low pressure steam
flow from the turbine driver outlet into the refinery low pressure
steam main header, giving a varying pressure in the low pressure
steam main, depending on demand.
On Back Pressure Control, the objective is to maintain a constant
pressure on the refinery low-pressure steam main header. This
results in a varying MW output from the generators, as the turbine
governor automatically adjusts in order to maintain the refinery
low pressure steam header pressure. Thus in this mode, the electrical
power generated varies in direct proportion to the low-pressure
steam demand of the refinery.
The low pressure steam system can vary considerably depending
on process demand, therefore normal operating mode for the Turbo-
generators is on Back Pressure Control to maintain a constant
pressure on the low pressure steam system.
“Back Pressure Control” Mode.
This mode is only possible when the frequency
is being held constant by a second generator (9G-1) or when running
parallel with the National Grid.
When operating in Back Pressure Control, an increase
in the back pressure will be corrected via the pressure set point
change to the Controller, which will cause the inlet valves to
close accordingly.
Control can also be set at negative values, e.g. it is possible
to compensate for pressure loss ( process demand for steam ).
If the National Grid Supply were lost the turbine
generators would automatically change over to speed control .
The speed control device will be pre-set at its upper limit ,
therefore the generators output would increase to maximum ,this
in turn will reduce the amount of electrical load shedding required
and ensure stable frequency control.
Any change over of turbine controls will be bump-less to ensure
the stability of the refinery electrical and steam systems.
LOAD SHEDDING
Load shedding package provides for different
scenarios, in regard with the specific situation. This results
to increasing the refinery flexibility to keep the processes running
to the maximum possible extent. The Load Control is implemented
with high reliability by means of the triple redundant controllers
and the hot backed up Supervisory control via the both Workstations.
NEW MNEMONIC SCREENS
New mnemonic panels were in the scope of the
supply. They were built on a modern contemporary style. Along
with the live light indication, digital presentation of selected
parameters was provided.
The control priority via these panels was arranged
through a specific priority.
Communication to the Steam
producing Sub-system
A communication was established between the two
systems, realizing bilateral data flow, which resulted to overall
control backup.
Energy Metering and electric power import-export
optimization
Special software shell over the turbo-generator
control algorithms was developed. This shell ensures import/export
energy measuring, as well as, power factor or reactive power control.
The continuous import/export consumed and produced energy improved
the utility efficiency.
Supervisor Monitoring and Control through the Main
Control Room
Function of monitoring of the Main Control
Room Power Supply and its active backing up through Uninterruptible
Power Supply and Diesel generator was added to the System.
To the top of the page
Click on the images to
enlarge
Reference for this product
To the top of the page
home / about
us / products / news
/ quality assurance / download
/ contact
