Basic Project Engineering : Electricals for a Green Field Project.

One of the young engineer informed me that he was on look out for some guidance on project engineering. He had been working in industry for last five years. He just got transferred to a green field project for his organization. Thinking of his inability to get some guidance on net, I thought to give some input for the young engineer. An engineer may feel little uncomfortable on joining a Project Team at the Basic Engineering Stage of Project.

At this point of time, the Management is in the process of working out a Realistic Estimate for the new facility. This would be the `First Cut Estimate’ to do the internal assessment. Subsequent to this, the Project Consultants will be engaged and detailed planning will be carried out.

If you have joined as a Key Member of the Electrical Team, following chronology will be of great help to get a grip on the situation.

1.    Technology In charge has to provide a rough layout of the facility to work on the basics.

2.    Layout of the Main Receiving Station to be chosen with the 'Highest Grid-voltage Possible'. This will be useful for Greater Stability of Power Supply. If it is in a Coastal Area or Polluted Location, a GIS is preferred.

3.    Express Feeder to the facility to be chosen. This is a must for proper voltage regulation.

4.    Grid Transformers to be with OLTCs and maintenance standby, if a Continuous Process Plant. Fault level of the Grid will decide the Percentage Impedance of the Transformer.

5.    Sizing and Location to be fixed up for Load Centre Sub-stations in various locations of the plant.

6.    HV or MV Power Distribution, to be decided, to Load Centre Substations. Cables can be Directly Buried, or through a RCC Cable Trench with Pumping Facility to keep it dry, or on Overhead Cable Trays. Buried Cables and Cables on Tray will reduce the cost as Cable in Duct and RCC Trench may lead to substantial deration. Overhead lines inside a Manufacturing Complex can be hazardous!

7.    Secondary Load Centre Sub-stations may be planned with Ring Main Units (RMU) as this will eliminate the need to take annual shutdowns for Bus-bar Cleaning and Tightening

8.    Layout of Load Centre Substations to be planned with convenient orientation for cabling etc. Ventilation/Pressurization is to be taken care to avoid adverse effect on   Switchgears. Transformers must be located at Different Enclosures with Oil Drainage, Soak Pit etc.

9.    Not to compromise on location of Panels due to the need of Ventilation and Safety. Invariably wrong selection of “Below the Staircase” is a compromising formula.

10. DB & Cabling layout at the Production Area is needed to size the shop floor properly.

11. Lump sum cost may be assigned to Energy Metering, Illumination, DC Supply etc.

After the “First Cut Estimate” is prepared, agreed and Project Consultant engaged, work to be started to crystalize ideas with Concept Notes on various systems and equipment. Following will be useful, detailed engineering will be the job of the consultants.

Concept Note#1: Layout of Power Receiving Station

·     Near the boundary of the complex.

·     Substation Rooms to be at an Elevated Room with Cellar below for Cabling. This is needed to avoid flooding.

·     Pumping arrangement, with sump, in Cellar to evacuate any water.

·     Bays for Lightening Arresters, Isolators, PTs, CTs, Incoming CBs, T-offs, Bus Bars, Sectionalisers, EB’s Metering Room, Transformers, Oil Drainage, Soak Pit, Cable Trench to Switchgear Room, MV Switchgear Panels, DC Battery & battery Charger Room, Ventilation Room, Control Room with Mimic Panel for Operation of Switchgears, OLTC Panels, Air Conditioning Unit, Monitoring Screen for CCTV of Yard, Energy Metering and Monitoring System.

·     All Entries to be kept properly closed to avoid entry of insects and vermin.

·     Epoxy Insulated Coating of 1 meter wide may be done, in front of Switchgear Panels.

·     Transformers to be ensured for proper mountings like Differential CTs, OLTC (Taps as per Voltage Conditions), Conservator, Oil Gauge and MOG, Winding & Oil Temperature Gauges for Alarm and Trip, Bochholz Relay, Oil Surge Vent.

·     Access Control and Boundary.

·     Earthings for System, Structures, Equipment, Fencing.

·     Single Core Cables, if needed, to be taken in Panels through Aluminium Plates to avoid setting up of an Eddy Current.

Concept Note#2: Cabling to Load Centers.

·     All outdoor cabling should be Armoured and with Black Covering Material.

·     Best Cabling Method is on Overhead Trays with requisite sizes of Cable Trays. This will help in avoiding the interference for Expansion Activities.

·     Gaps between Adjacent Cables to be maintained for Air Circulation/Ventilation.

·     No outdoor Termination with XLPE Cable is allowed. Covering against Ultraviolet is must.

·     Cable trays should be taken in Separate Trays, earthed, from Pipe Lines.

·     In case of Single Core Cables, Trefoil Formation with Non-metallic Clamps to be used.

Concept Note#3: Locating Load Center Sub-stations.

·     a. Production Plant (more than one, if needed for different buildings, away from each other),

b. Water Treatment Plant, Compressor Station, Boilers, Workshop, Lighting,  

  Administration Block,

c. ETP, and

d. CPP/DG House.

·     The Load Center Sub-stations to be located at centrally at a side. Place should be convenient to connect from the Trunk Cables from Main Receiving Station

Concept Note#4: Inside the Load Center Sub-stations.

·     It is preferable to have an Elevated Substation to avoid Flooding. Drainage pumps needed. Cables should not be submerged, which can affect Cooling/ Safety etc. Trays must be used for Cable Routing.

·     MV Switchboard may be of Ring Main Type (RMU), provided Fault-level Permits. This will economise the cost.

·     Station Batteries to be installed for Shunt Trip System. As a compromise, Power Pack Units can be used.

·     Adequate Ventilation to be provided. No Exhaust Fan `be provided near Any Electrical Panel (these causes accumulation of moisture near them).

·     Earthing to be provided for Systems and Body.

·     Single Core Cables, if needed, to be taken in Panels through Aluminium Plates to avoid setting up of an Eddy Current.

·     PLC of required size to be planned for Load Shedding etc. Processor Loading to be less than 50% of Designed Capacity. The output to be connected both in LV and MV Switchgears…selection on the basis of priority!

·     Electronic Energy meters to be merged with the Computerized Energy Monitoring System, through wireless connection, at Main Receiving Station.

·     Transformers to be ensured for proper mountings like Conservator, Oil Gauge and MOG, Winding & Oil Temperature Gauges for Alarm and Trip, Bochholz Relay, Oil Surge Vent.

·     Transformer Oil Drainage and Covered Sump to be planned.

·     Emergency Stop Switches must be placed in the Transformer Enclosures.

Concept Note#5: Workshop.

·     Electrical DBs to be planned in these locations. One Set of LT Incoming Cable can be brought to a DB in this building and distributed.

·     Ideally Workshop Building to house:

a. Mechanical Workshop.

b. Electrical & Instrument Workshop.

c. Library and Archive.

d. Office Block.

·     15% extra outlets may be planned for future.

Concept Note#6: Illumination.

·     LED type Tube Lights, High bay, Flood Lighting, Street Lights to be planned. They will provide attractive Payback Periods.

·     Door Switches to be connected for Sub-station and Cable Cellars.

·     Building management system may be incorporated for all office areas.

·     Streetlight Poles to be used only in case of need. Otherwise Walls, Buildings and Structures to be used for installing them. This will keep the premises free from obstructions.

Concept Note#6: Other Miscellaneous.

·     Class IE2 and better Motors to be used for greater efficiency.

·     Electronic Relay is preferable over Bi-metal type. However, thermal overload seetings should not be more than 90% of FLA.

·     Any Frequency Drives must be procured for keeping Harmonics within THD=±5%.

·     Detuned Filters for MCCs to be planned in consultation with Consultants/Vendors.

·     Automatic PFIC panels to be designed with Capacitors of 440 V (not 415 Volt) as the same has a substantially better longevity. 10% overvoltage (allowed regulation) overloads Capacitors by 30%.

·     Public Address Systems may be planned only in Noisy or Inflammable areas.