ADVANTAGES AND CHALLENGES OF MODULAR SOLUTIONS FOR ELECTRICAL SUBSTATIONS

Copyright Material PCIC Europe Paper No. PCIC Europe EUR19_27

Luigi Bellofatto

Skema SpA 20811 Cesano Maderno

(MB)

ITALY

Abstract – There is an increasing demand by operators in the Oil & Gas sector for modular units to create unique solutions that can be completely customised and which are ready for use when transported to the final operating site ("plug and play" solutions). Complete electrical substations ready to be transported and put into service at the final installation site have been constructed and tested in accordance with Client specifications, ambient conditions and limits on transport dimensions. The distinguishing feature of these substations is their modular construction. Every substation is subdivided into two or more modular structures specially developed and produced so that they can be disconnected and transported on barges or lorries to the final installation site where they are reconnected and ready for use without the need for other systems. With this type of supply the local construction of buildings for substations and successive installation of panels and internal systems is no longer necessary. Consequently the time and costs for modular substations are much lower and they operate reliably since they have already been tested.

I. INTRODUCTION

The electrical substation is a single structure which is

installed in a predefined site in an installation for the distribution of electricity to other substations or final users.

The electrical panels in a substation are the hub of the electrical power network. Switches are opened and closed locally or from outside the substation which must therefore have a secure communication system.

This paper presents substations that have been manufactured for onshore and offshore Oil & Gas installations.

Ambient conditions are severe, therefore the substations are closed structures with outside connections using cables. All the rooms of the substations are equipped with HVAC system.

The modules supplied were metal structures, suitably insulated and fire resistant, containing mechanical and electrical equipment, instruments, air ducts, cable ducts, lifting equipment necessary for maintenance, all connected to form the main and auxiliary systems of the substation.

The individual equipment items were manufactured in the factories of the supplier, transported to the fabrication yard, installed in the modules that form the entire electrical substation and connected to form part of the relative main or auxiliary system. The systems were tested at the fabrication yard.

The modules were then disconnected, prepared for transportation with suitable preservation, loaded onto a barge and transported to the final installation site.

The modules were then reassembled and connected to form the entire substation.

All the systems were tested again and the substation was handed over to the final Client.

The paper describes the systems for disconnecting the modules, for the preparation for transport and their preservation, and the procedures for reassembly on the final installation site.

A description is also given for checking the construction, pre-commissioning and commissioning procedures in the fabrication yard, which are necessary also for the activities on site.

II. ADVANTAGES OF MODULARISATION The advantages of modularisation of electrical

substations were:

• Reduction of man-hours on site • Reduction of peak labour force requirements • Reduction of the risk of falls on site • Greater overall productivity • Reduction of site congestion • Reduction of site security problems • Possibility of conducting QA / QC controls and

acceptance of operations on completed parts of the module before mechanical completion

• Minimising risks that could affect the construction plans, costs and operations of the systems

• Possibility of choosing the final installation site of the substation at a later time

A. Reduction of man-hours on site An important contribution to the reduction of time and

costs was the reduction of man-hours at the installation site. The substations arrived on site which had already been prepared with concrete piles on which the modules were positioned.

Installation took place following the procedures agreed with the Client a few months before the modules were shipped.

After the installation and reassembly of all the modules the cables were reconnected between adjacent modules and the air ducts were joined.

Every cable to be reconnected had already been prepared before transport, placed in a wooden crate and with the ends wrapped in a sack and already prepared for reconnection by numbering each wire and attaching a cable-tag to the sheath of the cable. Before reconnecting the cables, they were first laid in the cable tray which was a natural continuation of the tray in the adjacent module.

Before reconnections, all cables wires shall be checked for continuity and insulation to ground following the same procedure and signing a test report. The wires of the cable were reconnected in the same terminal blocks from which they had been disconnected and therefore without any surprise or problem because this procedure was already tested previously.

The air ducts were also connected without any surprise as this involved bolting together two flanges of the air ducts, which were already face to face, and replacing any insulation.

All the work done by the labour force on site was therefore reduced considerably compared to the time necessary for complete or partial installation locally.

Fig. 1 Man-hours the for installation and testing with

modular approach

Fig. 2 Man-hours for installation and testing without the

modular approach. The number of work hours is represented by the size of

the blocks. The block diagrams in figures 1 and 2 show the flow of

activities and an assessment of the proportions of hours in the fabrication factory, fabrication yard and in final installation site with the modular substations system and the direct construction system on site, considering the logistics difficulties and qualification of local personnel.

You can see how the modular substations system also requires preparation for transportation activities such as sea fastening of the equipment, preservation of equipment and modules which the direct installation system does not require.

In spite of these differences, the modular substations system requires fewer hours compared to the direct installation system on site.

B. Reduction of peak labour force requirements During the installation of units in the rooms of the

substation there are specific periods of time when the size of labour force performing installation work peaks. In fact while the HVAC units are being installed it is possible to install the panels in other modules at the same time, or for example the lamps can be installed at the same time as the F&G sensors.

This peak will not occur in the final installation yard because with the modular substations system the work consists only of connecting cables and air ducts between adjacent modules and not installing all the equipment in the substation.

C. Reduction of the risk of falls on site

Reduction of the risk of falls concerns both the

equipment and the personnel working on site. Since the equipment is already installed and anchored

there is no risk of their falls. With regards to people, the risk of falling is reduced

because the job of reconnecting cables for example is done mainly in junction boxes and panels that do not require ladders or mobile scaffolding to be reached.

D. Greater overall productivity for production

With installation in the fabrication yard a higher

productivity is obtained compared to installation in the final installation yard. This is because the various facilities and materials for the construction of modules are easiliy accessible in the fabrication yard. Productivity is without doubt lower if installation takes place in a location not specialised in the production of modular substations.

E. Reduction of site congestion

With the modular substation system the equipment

arrives at the final yard already installed, so no plant is required for lifting, inserting and anchoring the equipment.

The construction of storages for installation material is no longer necessary; the loose material is already supplied in containers accessible inside; furthermore it is not necessary to build offices in the installation site.

For these reasons the Final installation yard occupied a smaller less congested area than a site in which the entire electrical substation is manufactured.

F. Reduction of site security problems

Site security was limited to checking the closure of the

modules and containers of material supplied loose. Storage facilities and containers outside the substation

were not needed to house installation material supplied in standard lengths which have to be cut to measure for installation, such as Unistrut, cable trays, cable spools, tubing, fittings etc.

Material handling outside the substation was reduced considerably because the material is already installed and therefore requiring less security checks.

G. Possibility of conducting QA / QC controls and

acceptance of operations on completed parts of the module before mechanical completion

FABRICATION FACTORY FABRICATION YARD

FINAL INSTALLATION

YARD

REAS

SEM

BLIN

G+CO

MM

ISSIONIN

G

TRANSFORMERS

SWITCHGEARS

HVAC

F&G

INSTALLATION+COMMISSIONING+SEA FASTENING+PRESERVATION+TRANSPORTATION

FABRICATION FACTORY

INSTALLATION+COMMISSIONING

FINAL INSTALLATION YARD

TRANSFORMERS

SWITCHGEARS

HVAC

F&G

Before the installation in the modules, all the equipment was checked by QA/QC and installed only after passing the FAT (Factory Acceptance Test). This test for complex equipment such as the HVAC units, panels and PLC required several days at the manufacturer’s premises for testing. After passing the FAT procedure the equipment was ready to be installed in the modules without any problem.

H. Minimising risks that could affect the construction

plans, costs and operations of the systems

The equipment control and acceptance operations were carried out before its installation in the modules, therefore the risk of having to remove faulty equipment was minimised.

I. Possibility of choosing the final installation site of the

substation at a later time The position where the substation is to be installed is

normally decided at the beginning of the project, however, with modular substations this decision can be taken or changed if necessary even after the substation has already been assembled.

III. EXAMPLES OF MODULAR ELECTRICAL

SUBSTATIONS

The electrical substations supplied for the Oil & Gas projects have different modular configurations. Some consist of a single module, others of several modules. An example was a substation that was designed, built and shipped in 32 modules because it had to be transported with 3.5 m width limitation.

This was a considerable challenge because the connections of 32 modules were studied in order to minimise their number and make the reassembly and electrical connections safe.

Particular care shall be taken in case of transportation of modules equipped with heavy equipment as transformers or HV/LV Switchgears. Where possible, the equipment shall be split in several parts and sea fastened to avoid that vibrations and mechanical stresses during transportation may damage the entire assembled equipment. In case of transformers where the splitting is not possible, the single equipment shall be secured and fastened to the module structure.

Fig. 3 Single module substation

Fig. 4 Four modules substation

Another characteristic concerns the position of the units for the HVAC, which can be installed either outside or inside the substation.

Fig. 5 Modular substation with 3 external HVAC units

Fig. 6 Modular substation with internal HVAC units

The external dimensions of the modular substations supplied vary from 15 x 3.5 x 4 m to 80 x 15 x 9 m approx. The weights vary from 27 tonnes to 1,100 tonnes. The dimensions of each module vary depending on transport requirements and any restrictions imposed by the Client.

IV. ENGINEERING The design and engineering of the modular substations

were developed through studies, calculations, drawings, verifications and validations, and a series of specific detailed procedures to ensure the correct sequence of assembly and testing operations on site.

Dedicated calculations, drawings, technical documentation and installation details were also developed to design each system, including the main

TRANSFORMER ROOM

BATTERY ROOM

ELECTRICAL ROOM

ELECTRICAL ROOM

ELECTRICAL ROOM

ELECTRICAL ROOM

ELECTRICAL ROOM

TRANSFORMER ROOM

TRANSFORMER ROOM BATTERY ROOM

equipment, to comply with all project and environmental requirements.

A 3D model of the modular substations has been developed, that allows a 360° view of the whole substation complete with structural and architectural parts, electrical and instrumentation, HVAC and F&G systems. The 3D model of the substation and its equipment enables to ensure a thorough and consistent monitoring of the most critical areas, a functional dimensional verification of the correct position of the internal elements in the various areas, and the removal of any clashes between the elements of the disciplines. It also enables to interface with the Client efficiently, giving a unique access key to the project for the success of both the engineering and construction phases.

V. EQUIPMENT IN THE ELECTRICAL

SUBSTATIONS The main items of equipment contained in the electrical

substations supplied for various projects were:

• Transformers • Electrical Panels • HVAC System • Fire &Gas System

The substations were completed with the following

systems:

• UPS • Lighting system and sockets • Lightning protection system • Internal and external telecommunications system

In this paragraph the main equipment and its

installation in the modular substations will be described.

A. Transformers

Resin transformers from 0.5 MVA to 2 MVA, 10/0.4 kV were installed in ventilated rooms allocated exclusively for this purpose or in cabinets placed next to the panels to which they are connected with busbars.

Transformers are the heaviest equipment (about 5,000kg) and cannot be installed subdivided into modules.

For transport the lower part of each transformer was anchored to rails with bolts, the top part was secured with straps to the structure of the module.

Special attention was given to the anchoring of each transformer during transport and dimensioned to withstand the oscillations and accelerations of the barge and lorries that transported the modules.

The transformers were installed in a way that allows them to be removed if replacement should become necessary. In the transformer room F&G sensors for smoke detection and infra-red sensors to check for temperature shall be installed.

For fire and gas detection, electronic smoke sensors shall be used or a pipe system installed at the transformer ceiling. The monitoring of the temperature shall be made with infra-red sensors close to the bolted connection from the transformers to the bus-bars.

B. Electrical Panels

Panels insulated with SF6 gas for voltages of 110 kV, 35 kV and 10 kV and air insulated panels for voltages of 400 V were installed in the substations.

Fig. 7 GIS room with 5 GIS “diameters” and control

panels Each panel is controlled locally by a synoptic panel

installed at a distance of few metres so that the local operator is not affected by thermal effects generated by an electric arc inside the panel. The panels supplied are certified to contain the internal arc in accordance with the relative Standard.

Every panel contains overload and short circuit protection devices and communicates with the central supervision system through copper cables and fibre optic cables.

A temperature control system of the connections between busbars with infra-red sensors is also installed in each panel.

Another feature of the panels is the internal arc detector systems using special fibre optics installed along the busbar routes of the panel, in the area where external cables are connected and where the transformers are installed.

C. HVAC System

Every substation is heated, cooled and ventilated by a

climate control system which draws in external air, treats it and introduces it into the substation through metal ducts. There was also an overpressure system, chemical filtration, which interfaces with the Fire & Gas system to ensure safety.

Fig. 8 Triple outdoor HVAC unit for modular

substation Fig. 9 Double HVAC indoor type unit for modular

substation

D. Fire & Gas System (F&G)

A Fire & gas detection system was designed in order to provide fast detection of a fire or gas inside the building and/or presence of hazardous gases around the building boundaries, to properly identify its location – giving to safety operators all the information related to act - and to take automatically pre-programmed action to reduce risks.

The F&G system was able to communicate with other systems in order to carry out the safety procedures.

The FGS was designed so as to avoid a single point failure which may hinder the integrity, reliability and capability of the overall system at all times during operation.

Fire & gas detection system mainly consisted of the following equipment:

• Fire and Gas Alarm Control Panel • Smoke detectors • Heat detectors • Gas detectors (CH4, H2, H2S and O2) • High sensitivity smoke detector (HSSD) (below

raised floor) • Manual push buttons • Sounder • Beacon • Monitoring and command modules, connected on

the wiring loops

A detection system for fire and hazardous gases such as H2, H2S and CH4 was installed in every modular substation.

The system consists of sensors installed in the ceiling and the false floor, connected by local concentrators to the central control panel. In the case of smoke or fire or an increase in temperature or the presence of hazardous gases, the F&G system produces acoustic and visual alarms inside and outside the substation, immediately closes the dampers in the air ducts and sends a signal to the HVAC system which initiates the operations necessary to isolate the substation from the external environment.

The F&G system also communicates with the central supervision system through copper cables and fibre optic cables.

The F&G detections system consists in smoke detections sensors installed in the room ceiling / false floor and with heat sensors infer-red type places close to the electrical bolted connections.

In case of large and high rooms where there is no interferences with structures, beams, cable trays, high equipment, the system with laser beams scanning the room ceiling shall be adopted.

VI. CHECKS AND TESTS ON THE SYSTEMS

The systems installed in the fabrication yard were

checked in 3 stages:

• Mechanical Completion, • Pre-commissioning • Commissioning

The results of the checks and tests were collected in

the related check sheets for future examination and reference also in the reassembly stage of the modules in the Final fabrication yard.

One advantage of modular substations was postponement of replacing malfunctioning components during testing at the final fabrication stage without delaying delivery of the substation. With the construction of the electrical substation directly in the final fabrication yard instead there was a risk of delaying delivery of the substation because a malfunctioning component, for which there is no spare part, may require several weeks to be replaced.

A. Mechanical Completion

After installation, every simple or complex component

was checked for correct mechanical installation.

The “Mechanical Completion” procedure involved from 10 to 15 checks for each component, following a sequence in accordance with the list written on pre-printed forms already agreed and approved by the Client. The Mechanical Completion activities including the recording of the results, signing and stamping of the forms was done together with the Client’s inspectors.

The challenge in this case was to carry out numerous checks without interfering with the installation of other components in progress and without delaying the delivery of the substation.

Since checks were carried out on the initial installation of similar components (lamps, cable glands, MCT, cable trays, F&G sensors) there were fewer problems in later installation work. This was the advantage of manufacturing and installing modular substations.

B. Pre-Commissioning Pre-commissioning activities concerned the functioning

of the simple parts of the installations. For example, for the lighting system each circuit was individually subjected to a function test (switching on/off, operating time of the batteries inside the lamps, checking the numbering of the components (TAG) belonging to the same circuit, measurement of the impedance for live-neutral and live-ground malfunctions). Another pre-commissioning function check was done on the F&G sensors belonging to the same loop.

All the pre-commissioning activities were carried out in accordance with sequences stated in the relative forms.

Pre-commissioning activities, including the recording of the results and affixing of stamps and signatures on the forms, were carried out together with the Client’s inspectors.

C. Commissioning

Commissioning activities concerned the functioning of

every complete system. Commissioning the HVAC system was very complex

because it involved measuring the correspondence of the HVAC system to the design requirements.

Therefore the temperatures at various points in the substation were measured and then the equipment involved was calibrated in order to obtain a thermal and air flow balance. Commissioning the HVAC also involved the power feed MCC of the HVAC, the variable speed drives for the fans, the static switches for the heaters, the F&G system and of course also the PLC of the HVAC.

Commissioning the lighting system was done by measuring the level of illumination in numerous zones and at predetermined points of the substations and recording the values measured for comparison with those required.

An advantage of the modular substation system was the possibility of being able to add or move lamps easily in the modules to even out the level of illumination.

VII. ACTIVITIES AFTER TESTING

When all the substation systems had passed the tests, they were prepared for transport.

These activities are necessary only in the case of modular substations constructed in the Fabrication yard and not directly at the final installation site.

These activities were:

• Sea fastening, • Preservation, • Dismantling, • Load-out.

A. Sea fastening All the equipment installed in the modular substation

was anchored mechanically to the module to prevent damage due to oscillations and vibrations during transport.

The structure of the modules was also reinforced with temporary vertical and oblique braces to stiffen the structure for lifting and transport.

Fig. 10 Modules with temporary braces Equipment with large dimensions such as the

transformers, panels and HVAC units were anchored using tape tie rods attached to the top part of the equipment and the floor of the module.

B. Preservation After or during sea fastening all the equipment installed

in the modular substation was wrapped with sheets of special material, of a type that reduces humidity, to form a closed cover.

C. Dismantling Dismantling was very laborious because it involved the

mechanical separation of the modules after first separating the flanges of the air ducts and disconnecting the electrical cables.

To ensure perfect alignment of adjacent modules guiding pins were installed (see figure 11).

Fig. 11 Guiding pin system The parts of the modules that were without walls after

separation were closed with temporary wood walls.

D. Loadout Each module was loaded using cranes or special

forklifts on the barge moored near the Fabrication yard and anchored for transport.

Fig. 12 Transfer of module

VIII. REASSEMBLY Reassembly in the final fabrication yard was performed

following the detailed reassembly procedures agreed with the Client.

The sequence of activities is the same as in the fabrication yard but in reverse; for the substations with a number of modules in particular:

1. Unloading of the first module onto its final plinths, 2. Removal of the temporary wall and ceiling, 3. Removal of the temporary internal braces of the

module, 4. Unloading of the next module onto temporary

plinths, 5. Removal of temporary walls and ceiling, 6. Positioning of the module above or next to the

module already placed using the guiding pins, 7. Removal of the temporary walls and temporary

braces, 8. Repeat from point 4 for the other modules.

After mechanical reassembly of all the modules the air ducts are reassembled and the cables are reconnected following the Cable Schedule.

IX. TESTING After reassembly of the modules to form the complete

substation, the procedures were followed for Mechanical Completion (only the components reassembled on site), Pre-commissioning and then Commissioning, based on the relative check sheets produced in the Fabrication yard.

X. CONCLUSION

The article has described the importance of the

selection of electrical substation made with modular system or made with conventional system, in order to meet the client requests, time and quality.

The substations contain several equipment connected with thousands of cables and wire connections and require specialised personnel for installation of single equipment and their operation together with other equipment in substation or outdoor.

The conclusion of this article is that to have on site a complete “plug-in and play” electrical substation, the modular solution is the best choice from timing and money saving.

XI. VITA Luigi Bellofatto has a Bachelor of science in

electronic engineering and management, a Master of Science and the PhD in Electronic Engineering from the Politecnico of Milan. He has been working with Skema since 1997 and after a significant experience as Electrical Engineer and then Project Engineer. He is currently the Lead Project Manager and he has been involved in several major international Oil & Gas projects both onshore and offshore.

He is a member of the PCIC Europe committee and holds the position as Technical Secretary.

luigi_bellofatto@skemaq.it