Electrical

JABUNGCLASSROOM

TRAINING

Electrical

JABUNGCLASSROOM

TRAINING

Agenda

Electrical overview Generating system Main Switchgear Switchgear protection Earthing Lighting Protection Hazardous Areas SIL Introduction as applied to MCC system qualification (SQ) Introduction to of some validation phrases that will used during the course:-

SQ-System Qualification PQ-Process Qualification TQ-Technical QualificationIQ-Installation QualificationCCQ-Computer Code Qualification

Electrical System Overview 1

The electricity supply at Jabung Gas Compressor Station is provided by on-site generating plant.

Electricity distribution is specified to be by armoured cables to metalclad switchgear, motor control centres and distribution boards.

The electricity supply is nominal 400V/230V a.c, 3 phase and neutral, 50 Hz..

Comprehensive grounding and lightning protection systems are specified to provide a high degree of security to the facilities.

Main Switchboard 3 The Main Switchboard is specified as metal-clad and

fully fault rated for the maximum system short circuit level.

The Main Switchboard bus bars are specified to be divided into four sections, connected by bus- tie circuit breakers.

Each generating set is specified to be connected to a separate section of the Main Switchboard bus bars. The fourth section is provided for connection of a future generating set and future gas compressors.

Because the DE is specified with the same rating as the GE’s, there is no concept of emergency or standby loads. However, all the station auxiliary support loads are specified to be connected to the bus bar section supplied by the DE.

Other loads, mainly to the gas compressors, are connected to the other three bus bar sections.

The main incoming circuit breakers and the bus tie circuit breakers are all specified as withdrawable units.

Main Switchgear supporting ServicesMain Switchgear supporting Services

Main Switchgear DistributionMain Switchgear Distribution

Generating System 2

There are three generating sets, two of which are driven by gas engines (GE) and one is diesel engine (DE) driven. All the generating sets have the same rating and can run in parallel if required.

Although one GE is specified to support all the Station loads, it is specified that in normal operation the two GE generators will run. This will ensure that if one engine fails, the other set will continue to run and give uninterrupted supply.

In the unlikely event that the second GE should then fail, the DE set can run and is specified to supply all the Station loads.

In order to ensure stable operation of the engines, each set is specified with a resistive load bank. Should the load on a set fall below that required for stable operation of the engine, the load bank will switch-in automatically in stages of required values of resistance to provide loading.

Each load bank is specified to be connected to each generator upstream of the Main Switchboard so that it may also be used to test load a generator after maintenance before re-connection to the Main Switchboard.

Distribution from Combined Diesel and Gas GeneratorsDistribution from Combined Diesel and Gas Generators

Compressor Auxiliary Switchboards 4

Each gas compressor is specified to be provided with an Auxiliaries Switchboard to control the various drives and loads of a compressor such as the starter motor, oil pumps, heaters, coolers and igniters, etc.

The switchboards are specified to the same construction standards as the Main Switchboard.

The actual loads will depend upon the installed compressor, and will differ from one manufacturer to another.

Compressor Services Switchboard 5

A Services Switchboard is specified for each compressor cab for lighting, ventilation and small power receptacles.

The switchboards are specified to the same construction standards as the Main Switchboard.

UPS Units 6 A 24V d.c. unit and a 230V a.c. unit are specified for the instrumentation, control, communication

and alarm systems.

In the event of loss of electricity supply, the UPS batteries are specified to maintain 100% output for a period of 8 hours (battery autonomy).

The 24V d.c. UPS is specified with two dual redundant rectifiers, each capable of 100% duty.

The 230V a.c UPS, is specified with an automatic by-pass and a maintenance by-pass. The automatic by-pass is in synchronism with the UPS and the maintenance by-pass is manually operated.

All batteries are specified as valve regulated, lead acid (vrla). These have a long design operating life, typically 10 years, with virtually maintenance free operation.

Switchgear Trip Supply Unit 7

If the electricity supply is lost to a section of the Main Switchboard, a d.c. Trip Supply Unit is specified to ensure operation of the various circuit breaker tripping relays.

The unit is specified to the same standards and construction as the 24V d.c. UPS.

Earthing schematic

R Y B N ELV Generator

Conductive parts as defined in IEE 16th Edition Clause 542-01-09

Main Earth Bus Bar

Independent Earth Electrode

PES Earth Terminal on incoming supply

Grounding System 8 Each generator neutral point is specified as solidly grounded. Ground

fault current is not high enough to require the provision resistance grounding.

Isolators are specified for the generator grounding circuits, so that only one generator can be grounded at any time to prevent circulating currents between the generators when they are operating.

All items of electrical equipment are specified to be connected to the electrical grounding system by dedicated ground conductors. In addition, grounding will be provided by the cable armouring so that two grounding connections will be provided to each item of electrical plant as a matter of good practice.

As the station is specified to have an impressed current cathodic protection (CP) system for all the underground piping, it is important that the electrical grounding does not impose an unnecessary current drain on the CP system. Accordingly, the design specifies that all grounding electrodes are stainless steel, all buried grounding conductors are insulated and all grounding rods must be at least 5m. from a buried pipe.

The design also specifies that in addition to the electrical grounding, all non-electrical metallic items of plant shall be connected (bonded) to the grounding system. This is to achieve operator safety by ensuring these can never be a difference of electrical potential between electrical and non-electrical metalwork.

Lightning Protection 9

The lightning protection system is specified to be in accordance with international design codes, requiring the use of roof grids (collectors) for buildings and structures, down conductors and grounding rods.

Down conductors are specified with disconnecting links to allow measurement of ground rod resistance.

All specified lightning protection materials and design considerations are specified to be the same as for the electrical grounding system.

The lightning protection and electrical grounding systems are specified to be connected together, in accordance with code recommendations.

Lighting 10

Indoor lighting is specified to be by fluorescent luminaires.

Outdoor lighting is specified to be by high pressure sodium SON floodlights.

Lighting columns more than 3m. high are specified to be the hinged type, so that luminaires can be maintained at ground level.

Hazardous Areas 11 The governing code for the hazardous area assessment is specified

as the Institute of Petroleum, IP Code Part 15, Area Classification for Petroleum Installations.

For the purpose of the hazardous area classification, the process gas is specified as Fluid Category G (i).

It is anticipated that Hazardous Areas Zone 0 and Zone 1 Classification will be occur in localised areas. These will be, typically, sources such as process equipment vents and breathers and will be limited in extent. However, it is specified that the Contractor shall, as far as is possible, locate all electrical equipment outside of any hazardous area.

All electrical equipment is specified Apparatus Group IIA, Temperature Class T2 or better.

For Zone 1 areas, the required hazardous area enclosure for electrical equipment is specified as EEx’e’ and EEx’d’, in that order of preference.

For Zone 2 areas, the required hazardous area enclosure for electrical equipment is specified as EEx’e’, EEx’N’ and EEx’d’ in that order of preference.

Note: Electrical equipment shall not be installed in a Zone 0 hazardous area.

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