QUA IBOE POWER PROJECT (QIPP)
DOCUMENT NUMBER: NGAB-MP-EBDES-00-00001
Country Code Company Facility / Plant Code OriginatingOrganization Discipline Code Document Type Document Sub Type
Equipment / Component Loc Code Numeric Sequence Number
NG
AB
MP
E
B
DES
00
00001
Electrical Design Philosophy
for EPC-1 and EPC-2
(including AC and DC UPS Equipment)
11 26-Jul-2012 J. Lauthers See Page 2 See Page 2 Bassey J.Umoh Issued for CITT 0 15-May-2011 Jonathan
Lauthers See Page 2 See Page 2 Bassey J.Umoh Issued for Approval 10 25-Feb-2011 ILF William Coe Jonathan
Lauthers Scott Laidlaw Issued for Use Rev Date Prepared By Reviewed By Endorsed By Approved By Reason for Issue
Authorization Page
Prepared by: Date:
Jonathan Lauthers
Electrical Lead
Endorsed by: Date:
Elton Lesikar
EMDC Functional Manager
Endorsed by: Date:
Alex Guiscardo
EMDC Functional Manager
Endorsed by: Date:
Nolan O'Neal
Global Ops Functional Manager
Endorsed by: Date:
Patrick Anastasio
QIPP Engineering Manager
Approved by: Date:
Bassey J.Umoh
Project Manager
REVISION MODIFICATION LOG
Revision Section Description
10 All Reformatted for ITT 0 All Issued for Approval 11 ALL Issued for CITT
TABLE OF CONTENTS
1 SCOPE / PURPOSE 6
2 POWER PLANT 7
2.1 General 7
2.1.1 Basic Power Plant Configuration 7
2.1.2 Nigerian Electricity Regulatory Commission Grid Code Requirements 7
2.2 Assumptions 8
2.3 Electrical Design Philosophy for Power Plant 9
2.3.1 Applicable Standards 9
2.3.2 Voltage Levels 9
2.3.3 Power Train Sizing and Design 11
2.3.4 General Distribution Requirements 13
2.3.5 Normal Power Supply 14
2.3.6 Backup Power Supply – Essential / Black-Start Diesel Generators 17
2.3.7 Backup Power Supply – DC / UPS 19
2.3.8 Electrical Protection Systems 22
2.3.8.1 Generators 22
2.3.8.2 Generator Step-Up Transformer 23
2.3.8.3 Generating Unit Protection 23
2.3.8.4 Auxiliary Power Supply Systems 24
2.3.9 Electrical Control and Management System (ECMS) 24
2.3.10 Metering and Measuring 25
2.4 Electrical Design Philosophy for Substations 25
2.4.1 Substation at Power Plant Area 26
2.4.1.1 Switchgear and Instrument Transformers 26
2.4.1.2 Earthing and Lightning Protection 27
2.4.1.3 Protection 27
2.4.1.4 Electrical Control and Management System (ECMS) 28 2.4.1.5 Electrical Supply, Auxiliary Services 28 2.4.2 Substation Extension at Ikot Abasi Area 28
3 BROWNFIELD FUEL GAS PIPING 29
3.1 General 29
3.2 Assumptions 29
3.3 Electrical Design Philosophy for Fuel Gas Piping 29
3.3.1 Hazardous Area Classification 29
3.3.2 Lightning Protection 29
3.3.3 Earthing 29
4 TRANSMISSION LINE 30
4.1 General 30
4.2 Assumptions 30
4.3 Electrical Design Philosophy for Transmission Line 30
5 ATTACHMENTS ERROR! BOOKMARK NOT DEFINED.
1 SCOPE / PURPOSE
The purpose of this document is to define the basic concept and minimum requirements for the design of electrical systems including AC and DC Uninterruptible Power Supply (UPS) equipment for the Qua Iboe Power Project, Simple Cycle Power Plant.
QIPP power plant and power plant substation is intended to be operated by 3rd party personal under an O&M contract. An access road inside the double fence around the plant and a gate(s) in the inner fence(s) to the 330 kV substation will be installed for access by PHCN/TCN personal. A separate building accessed by these gates will house required metering display for PHCN /TCN. Access from this metering building into the substation proper shall be controlled by QIPP security.
The QIPP to Ikot Abasi transmission line will be handed over to PHCN / TCN after acceptance. Operations and maintenance will performed by the QIPP O&M contractor prior to acceptance. The QIPP modifications to Ikot Abasi substation will be turned over to PHCN / TCN for operation after acceptance. For Ikot Abasi substation all energized operations will be done by PHCN / TCN.
The plant is built for either base load or peaking load application. It will have various grid support features including black start and extended power factor support.
2 POWER PLANT
2.1 General
2.1.1 Basic Power Plant Configuration
This Philosophy refers to Simple Cycle (SC) configuration, approximately 500 MW at ISO conditions upon completion of Base Case including Option 1:
• Base Case, including Option 1 results in 3 or 4 gas turbine generator (GTG) units to meet approximately 500MW power plant output
• Black-start of the power plant and capability for dead bus closure of 330 kV circuit breakers (CB) to energize TLine is required
• Island Operation capability is required
• Preliminary Internal Load List – to be developed during EPC Bid (EPC Tendering, Phase 2)
• Typical Cause and Effect Matrix – to be developed during EPC Bid (EPC Tendering, Phase 2)
• Earth resistance shall be measured during dry season
• The CONTRACTOR shall meet the minimum requirements stated in the Nigerian Electricity Regulatory Commission (NERC) Grid Code and guidelines (the “Code”, or The Grid Code for the Nigeria Electricity Transmission System, Version 01 or later).
2.1.2 Nigerian Electricity Regulatory Commission Grid Code Requirements
The requirements are taken from NERC’s The Grid Code for the Nigeria Electricity Transmission System, Version 01. Numbers of referenced sections may change in later versions of the Code.
The following items are a summary of selected important grid code requirements. Compliance of the complete Grid Code is required.
Part 3 - Connection Conditions:
• Section 2.1: Frequency range: 50Hz +/-2.5% is the normal range, +3.5% / - 3% under extreme conditions
• Section 2.1: Voltage range: 330kV +/-5% is the normal range, no data given for extreme conditions
• Section 2.1.9: basic insulation value (BIV) for 330kV: 1300kV • Section 2.2: voltage perturbations
• Section 4.2: SCADA, measurement and data exchange (serial interfaces for data exchange with control centers, transient recording facilities at the connection point
• Section 4.3: telecommunication installations (hot line direct telecommunication cannels, communication lines for SCADA and protection
• Section 4.4: power system control (data for control centers)
• Section 4.5: protection criteria and metering (main and backup protection, typical fault clearance times, metering according metering code at the connection point)
• Section 4.6: additional requirements for power stations (performance requirements): • Generating unit power factor range: 0.85 lagging – 0.95 leading, at the generating
unit terminals (note: QIPP shall use minimum of 0.8 lagging – 0.9 leading, in order to compensate the reactive power generation/consumption of the 330kV OH-line to the substation Ikot Abasi
• Reactive power output must be (in steady state conditions) fully available within the voltage range +/-10% of nominal voltage at the connection point
• Generating unit must be capable of ramping up at a rate of at least 3% • Automatic voltage regulator (AVR) is required, including PSS
• Generating units must continue operation within frequency range -5% / +3% Part 4 - Operation Code:
• Section 4 - Black start: black start station shall have the ability for at least one of its generating units to start-up from shutdown and to energize a part of the total system, or be synchronized to the system
2.2 Assumptions
The entire output of the power plant is absorbed by TCN (grid operator), as to be stipulated in the Power Purchase Agreement (PPA).
GTG - Package:
• Generator voltage 15kV – this voltage fits to most Vendors/Manufacturers standards. Anyhow, the Vendor/Manufacturer may choose another voltage level between 12 and 20kV to apply the Vendor’s/Manufacturer’s standard.
• Generator cooling: air-cooled, TEWAC
• Static excitation system
• Mechanical Balance of Plant (BoP) systems e.g., fuel gas treatment skid, cooling system, water treatment system, diesel generators
2.3 Electrical Design Philosophy for Power Plant
2.3.1 Applicable Standards
The electrical system design, manufacturing, construction, installation, test and commissioning shall be in accordance with the relevant codes, standards, rules and regulations as listed below, all in latest valid edition:
• Local law, requirements of the grid code and authorities • IEC - (International Electro-technical Commission) • British Standards (BS)
2.3.2 Voltage Levels
Description Operating Voltage Earthing
Arrangement Used for
High Voltage Grid 50 Hz; 330 kV 3 ph +13% / -10% (1) Transformer neutral properly grounded (earthed) Grid connection Generator Bus Duct 1) 50 Hz; Un ±5%, 3 ph (rated voltage 15kV or acc. manufacturer standard)
The neutral of the generator is grounded
(earthed) via a
grounding resistor.
Generators and generator main connection
MV System 2) 50 Hz; 6.6 kV ±10% 3 ph + PE
The LV neutral of the transformers is grounded (earthed)
via a resistor, limiting the earth fault current to approximately 200 A.
Plant auxiliary power main distribution, large motors >200kW
LV Systems 3) 50 Hz; 400 V ±10% , 3 phase + N + PE 230 V ±10%, 1 phase
+ N + PE
The star point of the low voltage AC system is properly grounded (earthed).
Process equipment, auxiliary systems, motors ≤200kW.
Separate systems for lighting power sockets and HVAC.
Description Operating Voltage Earthing
Arrangement Used for
AC Uninterruptible Power Supply System 4) 50 Hz; 230 V ±5% 1 phase + N + PE
The neutral of the low voltage AC UPS system is properly grounded (earthed).
UPS for process equipment, control- monitoring- and communication equipment
DC System 5) 7) 110 V +10% / -15% 2 phase + PE
The 110V DC system is isolated from ground. Earth faults will be detected.
Preferred UPS for process equipment, protection-, control- and monitoring equipment
DC System 6) 7) 24 V +10% / -15% 2 phase
The 24 V DC system negative pole is solidly grounded.
Internal power supply and signal voltage for protection-, control- and monitoring systems
Note 1) the voltage variation for generators shall be in accordance with IEC 60034 +/-5%. Applying this voltage range, the unit transformers, LV auxiliary transformers, cables etc. can be designed to keep the consumer voltage within the standard voltage variations for MV/LV AC systems of 10% under all normal operating conditions. Also the grid code requirement +/-10% at connection point and the grid study data shows the maximum voltage drop 3% on HV OH-line to Ikot Abasi. No on-load tap changers (OLTC) will be required for unit transformers and LV auxiliary transformers. To compensate the voltage drop over the GSU transformers and the required voltage variation range of the 330kV grid, all the GSU-transformers will be equipped with OLTC.
Note 2) 6.6 kV is a typical MV level for power plants, where standard equipment designed for 7.2kV maximum operating voltage can be used with sufficient margin for operational overvoltage conditions.
Note 3) 400/230V is recommended by IEC 60038. If this system is used for three-phase-consumers as well as for single phase three-phase-consumers, a neutral conductor is required. Large distribution systems should be designed with solidly grounded (earthed) neutral (TN-system). The neutral conductor (N) should be separate from the protective ground conductor (PE) to achieve a high level of electromagnetic compatibility (EMC), hence a TN-S system shall be used, TN-C-S may be used for main distribution boards only. Distribution-panels supplying lighting and power-sockets shall be segregated from the LV-switchgear, utilising Δ/Υ-transformers. Distribution-panels serving domestic consumers (i.e. kitchen, bathrooms, laboratory) shall be equipped with an “earth leakage circuit breaker”.
Note 4) Single phase UPS are preferred to provide sufficient short circuit currents for selective tripping. UPS shall be used only for protection and monitoring equipment, which is not available
for DC-supply using standard equipment available for reasonable cost. Since the UPS-inverter includes a voltage regulator, the voltage variation can easily be reduced to +/-5%.
Note 5) The DC voltage level of the station batteries shall be chosen considering the power demand (some emergency consumers will require a power demand >10kW), limiting the voltage drop to keep the voltage within the specified variation range, and to limit electromagnetic interference. 110V is the best choice for such applications. Anyhow, other standard voltages such as 220V or 125V may be used, if this is the supplier’s preference.
Note 6) 24VDC is the standard voltage for I/Os of automation systems. A centralized 24VDC system is not recommended considering the voltage drop to supply a distributed control system. Note 7) For DC-Systems a wider voltage variation range of +10/-15% is recommended, which is the most economic compromise of battery sizing and acceptable voltages for consumers.
2.3.3 Power Train Sizing and Design Generator
• Sizing of all components: generator capability shall be higher (approximately +10%) than the maximum turbine output at site conditions which would generate the maximum power
• Generator voltage according with the supplier standard • Cooling method OAC may be acceptable
• Rated power factor: 0.8
• Power factor (minimum) range: 0.8 lagging – 0.9 leading
• Static excitation: dual channel AVR, n-1 redundancy for rectifier units
• Power supply static excitation: via excitation transformer, connected via IPB directly to the generator bus – alternative: supply from MV switchgear
• Synchronization: dual channel automatic synchronization, for 2 CB’s, manual synchronization only from local turbine control board with backup-synchro-check relay • Under normal conditions synchronization of the generator will be done using the
GCB (generator circuit breaker)
• In case the unit shall be synchronized to the grid following island operation (house load operation), the synchronization will be done using the 330 kV CB of the respective generating unit
• For island operation (supplying power to the grid as single power source for an island) a “dead-bus-closure” shall be possible for the GCB and for the 330 kV CB of the GTG generating unit.
• Isolated phase bus design with pressurization • T-offs for unit transformer
Generator Circuit Breaker
• SF6 type, designed and tested according IEEE C37.013 • Outdoor installation acceptable
• With motorized disconnector and earthing switches on both sides Generator step-up transformer (GSU)
• Oil immersed type, outdoor arrangement
• Cooling type ONAN/ONAF, cooling fans n+1 redundancy: the transformer capacity shall be designed for ONAN cooling at rated conditions, ONAF-mode shall be used for overload and abnormal conditions (e.g. higher ambient conditions)
• OLTC, range and tapings shall be selected to meet grid code / voltage variations under all operating conditions. The OLTC range shall be designed for all operating conditions (e.g. full load, part load, synchronizing) considering the worst case grid voltage variation, limiting the generator voltage to +/-5% and compensating the voltage drop of the GSU transformer.
• According grid code the 330kV system shall be operated within the range 95 – 105% of rated voltage
• Further the grid code requires power supply without restriction within the range 90 – 110% of rated voltage
• A grid study shows that the voltage variation in all 330kV substations is <19% and maximum voltage was 109%
Unit Protection
• Redundant multifunctional microprocessor based protection system Monitoring
• Instrumentation and monitoring for the generating units shall be sufficient to meet the requirements of protection systems (section 2.3.8) and condition monitoring systems (hereafter listed)
• Condition monitoring: it is recommended to install such additional condition monitoring systems for expensive electrical equipment, which is not yet standard but of proven design and available for reasonable cost, such as:
• GSU transformers: hydran for transformer oil (early warning device that alert developing fault conditions that could lead to equipment failures and unscheduled outages,
• Generators: partial discharge sensors and portable equipment for monitoring PD on the generators (early warning device that alerts insulation problems that could lead to equipment failures and unscheduled outages)
Grid Connection
• Via 330kV switchyard/substation
2.3.4 General Distribution Requirements
• All panels including lighting dc, etc shall have voltage indication. LV non critical panel may be LED per phase for critical need LED + meter. For switchgear LV and MV need switchgear class metering with a minimum metering of 3 phase voltage on each bus and ampacity on each source circuit breaker.
• All MV rear access panels need voltage indication in rear. Typically in MV piezo-electric voltage indication is used. All rear access panels shall be lockable and labeled.
• All panel and switchgear doors shall be supplied hinged and with built in locks.
• Larger panels that can accommodate space heaters shall be supplied with them, and LED indication that they are energized.
• All incomers to switchgear shall have Ammeters, all buses in all equipment shall have voltage indication
• Where n+1 sparing is employed for plant equipments, system segregation (cables shall not be run in same tray or duct) should be developed to ensure robustness of supplies and availability of equipment during periods of maintenance or breakdown, the supplies are to be independently derived as far as possible.
2.3.5 Normal Power Supply
Note the following drawings show three unit transformers and two essential generators. Detail design will determine the correct number of both. Though there is no electrical reason you cannot back feed from the grid through the GSU and through the UAT with the generator breaker open there currently is no mechanism to pay for this so this will procedurally not be allowed. If in the future this is allowed, the system shall be designed to allow this back feed. Contractor shall design the system to allow for back feed from the power grid.
Normal Power Sources for Plant Auxiliaries
• During normal operation of the GTG-units the generators are synchronized to the grid, the auxiliary power is supplied from the HV grid and from the GTG-units
• During house load operation of the GTG-unit(s) the generator(s) are operating in an island supplying the plant auxiliary power only, with just plant load for island load only one GTG should be running
Fig. 3: House load operation of GTG(s)
Unit transformers
• Connected via IPB to GTG generator bus • Oil-immersed type, ONAN
• Rating: designed for maximum auxiliary load: • One GTG unit starting
• Plus one GTG unit in operation • Plus common loads (BOP)
• Plus third GTG in standstill (if applicable) • Plus 10% safety margin
MV switchgear
• Metal clad air insulated and arc resistant switchgear with drawout switching units, type tested and factory assembled
• Separate bus bar section for each GTG-unit: incomer from unit transformer, feeders for starting motor, GTG LV auxiliary transformer, GTG excitation (if applicable)
• 3 or 4 couplers between the 4 bus bar sections. LV distribution general
• Fed from MV switchgear via LV auxiliary transformer(s)
• LV switchgear / MCC: metal enclosed arc resistant switchgear with draw out units, type tested and factory assembled – exceptions: for sub distribution boards of black box systems the equipment may be fixed installed according manufacturers standard
GTG LV distribution
• Fed from MV switchgear via GTG LV auxiliary transformer 1x100% • System segregation shall be maintained
• LV switchgear with single incomer, no coupler Common LV distribution
• Fed from 2 different MV bus bar sections via LV auxiliary transformers 2x100%
• System segregation shall be maintained between all 2x100% feeders or 3x100% feeders • Common main distribution: 2 incomer, coupler, automatic transfer device (2 of 3)
• Important common LV sub distribution boards: 2x100% feeders from main distribution • For LV sub distribution for redundant feeders/consumers: 2 incomers, coupler,
automatic transfer device (incomers and coupler controlled by “2 of 3” logic)
• For LV sub distribution for single feeders/consumers: 2 incomers, no coupler, automatic transfer device (incomers controlled by “1 of 2” logic)
• Less important LV sub distribution boards: 1x100% feeders from main distribution Power supply for 330kV switchyard/substation
• 2x100% Feeders from dedicated LV auxiliary transformers 2x100%, 2 incomers, couplers, automatic transfer devices (incomers and couplers controlled by “2 of 3” logic) • System segregation shall be maintained
Automatic transfer devices (ATD)
• ATD for 2 redundant normal incomers and 2 busbar sections with couplers: • The ATD shall control the 2 normal incomer CB’s and the coupler CB • Normal switching conditions: both incomers closed, coupler open • ATD for 2 redundant normal incomers and 1 busbar section
• Normal switching condition: one incomer closed, the other incomer open • The ATD shall be designed for
• Manually initiated load transfer between the normal sources without power outage, if the sources are synchronized
• Transfer of load shall be initiated automatically by incomer-protection and busbar under-voltage in order to minimize power outages
• Transfer of load shall be done only in safe condition: • if the new backup source is healthy,
• if the sources are synchronized in case of paralleling sources, • if the residual voltage is uncritical in case repowering after an outage • Short-circuit faults and earth faults at the busbar shall block the ATD • The ATD shall not interfere during diesel island operation
2.3.6 Backup Power Supply – Essential / Black-Start Diesel Generators General design criteria:
• Essential / Black-Start Diesel Generators shall be high speed 1500 rpm diesel generators which will result in three or four units to supply starting power to one GTG and worst case essential plant load and have an N+1 configuration. The attached drawings show a preliminary configuration of 2 100% essential generator on two separate buses. The finial number of essential generators and essential buses shall be engineered to maximize reliability and simplify controls.
• Capability of N diesel generator sets shall be sufficient for all GT-units in emergency shutdown or standby operation plus start-up of one GT-unit (black-start immediately after a trip of all GTG-units without grid power available)
• Each diesel generator shall be equipped with a day fuel tank for 8 hours minimum
• Each diesel generator shall be equipped with starting battery system for 5 starts without external power
• Each diesel generator shall also offer the possibility to be manually started, either by batteries or compressed air. Two electric starter-motors per diesel-engine are required.
2.3.7 Backup Power Supply – DC / UPS Fig. 5: DC / AC UPS Systems:
400
V Distribution Board
2/3 ATD Battery Charger 1 11 0 VDC UPS Inverter 1 230 VAC UPS Inverter 2 230 VAC 230 VAC UPS 11 0 VDC Battery Charger 2 Battery 1 Battery 2• Normal power source for the DC / AC UPS is the 400V distribution system (essential) • The sketch above shows a typical application for important DC consumers, consisting of
2 x 100% DC UPS system:
• Critical loads which shall be redundant shall be powered from the DC busses
• Each system consists of a 110V battery, which is normally supplied from the 400V AC system via battery charger and a 110VDC distribution board (voltage could change depending on total load, size of loads, distance to loads)
• The battery charger is designed for consumer load plus charging of the battery
• Redundant consumers will be connected to separate DC-systems, single DC consumers may be supplied via decoupling diodes from both DC-systems
• DC-system(s) will be used for all emergency loads (e.g. GT emergency oil pump, protection-, monitoring and control systems) DC motors started directly which have voltage drops that impact other loads are required to be on separate DC systems or to be on drive / inverter applications which remove the transients.
• All buses shall have voltage metering • All sources shall have ampacity metering
• The sketch above shows also a typical application for important AC consumers, consisting of a 2 x 100% AC UPS system
• The AC busses are separated by a normal open bus coupler or two separate panels which can be manually connected.
• Each system consists of a single-phase UPS inverter, which is supplied from the DC system
• The inverters are designed for full consumer load and are connected in load sharing mode in parallel
• The AC-UPS-system will be used for all emergency loads, which is not feasible to connect to the DC-system (e.g. HMI and such monitoring- control- and communication systems, which are not available for DC-supply)
• All buses shall have voltage metering • All sources shall have ampacity metering General design criteria:
• Designed for 1 hour power outage (but for HV switchgears at the substation 8-hours outage), all GTG-units shutdown or standstill (Note: design of DC/UPS-systems for 1 hour power outage is common practice, if a backup power source e.g. diesel generator units is available. Even in case of problems during automatic starting it should be possible to manually initiate a battery start or air start of a Diesel engine within 1 hour, if
qualified personnel are available on site. For essential switchgears such as MV, and Balance of Plant, 8 hours is required for DC/UPS-systems.
• Essential generators shall have two methods of starting. However, if the essential Diesel generator starts without problems, the power outage will last 5…20 seconds only, where the batteries will not be charged by normal/essential power)
Separate 110VDC system:
• One per GTG-unit: with 2x 100% battery charger and 2x 50% batteries • One for plant common: with 2x 100% battery charger and 2x 100% batteries • One for HV switchyard: with 2x 100% battery charger and 2x 100% batteries • Different nominal voltage (e.g. 125VDC) may be used for GTG-package 24VDC system (if required):
• Via 2x 100% DC-DC-converter, fed from different 110VDC busbars • DC-DC-converter installed decentralized, e.g. in control panels Separate 230VAC UPS system:
• One per GTG-unit: with 2x 100% inverter • One for plant common: with 2x 100% inverter • One for HV switchyard: with 2x 100% inverter The 110VDC UPS system will be used for:
• Process equipment, which is required for emergency shutdown (e.g. emergency oil pump)
• Switchgear control for HV, MV and LV
• Protection-, control- and monitoring equipment The 230VAC UPS system will be used for:
• Protection-, control- and monitoring equipment, which is not available for DC supply, such as computers and monitors for HMI’s and servers, communication equipment The 24VDC UPS system will be used for:
• Protection-, control- and monitoring equipment, which is not available for 110V DC supply, such as internal voltage for PLC systems, power plant control and monitoring systems and other “black box” control systems.
Other systems with dedicated backup batteries:
• Diesel driven fire fighting pumps shall be equipped with their own battery system for starting
• Other systems will have independent integrated batteries to meet the requirements, e.g. emergency lighting fixtures, fire detection system, PABX etc.
2.3.8 Electrical Protection Systems
In addition to specific protection mentioned below, transfer tripping / blocking schemes shall be used where ever possible, in the plant.
2.3.8.1 Generators
The mechanical generator protection will include: • Cooling air temperature
• Winding temperature • Bearing temperature
• Bearing oil temperature and pressure • Sealing oil temperature and pressure • Vibration monitoring
The electrical generator protection shall be redundant and will include following protection functions at the minimum:
• Differential protection
• Negative phase sequence protection • Loss of excitation protection
• Reverse power protection
• Stator ground fault protection (100% coverage) • Volt/hertz (over excitation) protection
• Over-/under voltage protection • Over-/under frequency protection
• Voltage restrained over-current or backup distance protection • Inadvertent energization protection
• Voltage balance, to detect PT blown fuse • Out of step protection
2.3.8.2 Generator Step-Up Transformer
The mechanical transformer protection for Generator Step-up Transformer (GSU) will include: • Buchholz relay (for main oil and for OLTC oil)
• Dial thermometer for oil temperature • Dial thermometer for winding temperature • Oil level (for main oil and OLTC oil) • PT100 detection for winding temperature
• Pressure relief device (for main oil and OLTC oil)
The electrical transformer protection shall be redundant and will include following protection functions (the protection zone shall include also the unit transformer and the HV connection line to the HV substation):
• Differential protection
• Restricted earth fault protection (low impedance differential) • Over-/under voltage protection
• Over-/under frequency protection • Over fluxing V/Hz protection • Overload protection
2.3.8.3 Generating Unit Protection
Additionally to the generator- and transformer protection following overall unit protection functions are required:
• Overall differential protection
• Protection functions to detect a grid fault: • Under voltage / over voltage protection • Under frequency / over frequency protection • Voltage unbalance protection
• Phase / vector shift protection
2.3.8.4 Auxiliary Power Supply Systems
The protection of MV cables, motors and transformers will be provided by non-redundant protection relays, which are installed in the MV switchgear.
The protection of LV systems is integrated into the LV switchgear, e.g. using protection devices built in into circuit breakers or using fuses.
2.3.9 Electrical Control and Management System (ECMS)
The control system of the power plant shall be used to monitor:
• System status of generation critical electrical system and components • Generator loading and load sharing control status.
The power plant ECMS shall be used for the following:
• Generate maintenance alerts and provide detailed real time equipment and system status information.
• Record system and equipment events/alarms into Notification and Alarm Management System (NAMS) and Historian server
• Trending performance of the electrical system will be done by the Historian server. • Online configuration of “Intelligent Electrical Devices” (IEDs) i.e., protection relays
• Transient event analysis for generators, HV switchyard and MV switchgear/MCC by the Historian server
• Load shedding is not required for GTG units.
• The essential generator will be sized to carry 100% of load to start one GTG and plant load. A simple load shed system shall be provided to prevent overload in case bus couplers are closed and a second GTG starter-motor is attempted to be started.
The ECMS capability may be integrated into the NAMS, or alternatively realized in a separate system which interfaces with the Master Turbine Panel.
The ECMS shall gather data from the following electrical equipment: • Generator • Generator protection • Transformer • Transformer protection • OLTC • HV Switchyard
• HV line / busbar protection • MV switchgear / MCC • LV switchgear / MCC • MV / LV Motor protection • Automatic transfer devices • AC/DC UPS
• Essential / start-up Diesel generator units • Variable Frequency Drives (VFD)
• Condition monitoring systems (e.g. generator partial discharge monitoring, transformer hydran system)
2.3.10 Metering and Measuring
Fiscal metering (for custody transfer) shall be installed at the connection points for the T-Lines. Metering shall be compliant with the grid (metering) code. Any other potential future load from QIPP substation at 330 kV shall require fiscal metering (e.g. supply for QIT Terminal).
The grid-operator (PHCN/TCN) shall be provided with separate fiscal metering devices installed in an enclosure at the switchyard-fence and granting access to meter-readings without entering either the power-plant, or the substation.
A multifunctional measuring/metering device class 0.2 shall be provided: • For each GTG unit, measuring at the generator terminals
• For each GTG unit transformer, measuring at the MV switchgear incomer A multifunctional operational measuring device class 0.5 shall be provided at least:
• For each LV incomer from transformer / diesel generator • For each main LV sub-distribution incomer
2.4 Electrical Design Philosophy for Substations
For the purpose of power evacuation generated in the Power Plant, the Power Plant will be tied to TCN network with a 330 KV double circuit TLine.
QIPP 330 kV substation will under normal circumstances be controlled by power plant personnel in Central Control Room (CCR), up to and including gantry to first tower of transmission line.
2.4.1 Substation at Power Plant Area
The substation at power plant will be brand new Greenfield substation. The substation will have a secure fenced area with limited & controlled access. The substation will share common facilities with the power plant. The control room for power plant will make provision for switchyard control panels. The substation will be constructed self-contained as far as possible. Provision will be made to control the power plant substation from the central control room of the power plant. However, there shall be a separate building within the substation-premises to accommodate substation-related electric- and control-equipment (SCADA) hence it shall be also possible to control the switchyard from the substation.
The Applicable standard for the 330 KV Switchyards is the One-and-Half- Breaker arrangement in conventional open air design.
For 3+1 feeders from generating units and 2 OH transmission line feeders. Since the high voltage connection from step-up transformers to the substation will be designed preferably as OH-line, all generating feeders must be arranged for arriving at the same end of the switchyard – consequently 4 bays are required. The disconnect switches to allow work on spare bays while substation is energized, all future equipment foundations and any other civil work to bring the ground surface to finish grade and cover to reduce the impact to the substation when fitting out spare bay, a bus jumper to replace future equipment shall be provided for any diameter with al spare bay to allow full functionality to the supplied circuit.. .Circuit breakers and other devices are not required in spare bays.
All feeder metering and protection shall be routed to the 330 kV substation building, the fiscal metering on the transmission line circuits will be redundant with one set of signals routed to the PHCN metering building and one set to the 330 kV substation building. In addition to metering phone communication through the power line carrier will also be in the PHCN metering building. The PHCN metering building will have the same requirements as the substation building (HVAC, office furniture etc).
The 330 kV substation at Power Plant shall have orientation, physical room, and bus capacity to handle a future plant of approximately 500 MW. The circuit breakers and other equipment in the diameter for the QIPP to Ikot Abasi transmission line circuits shall be rated for 1000 MW at maximum of 80% loading. Expansion room for the future circuits to connect the future power plant shall be possible on either side of the substation to facilitate connecting the future interconnect transmission line on either side of the substation with a transmission line crossing. The future space shall be within the road and fencing of the substation.
2.4.1.1 Switchgear and Instrument Transformers
The switchgear and other equipment should be rated accordingly for required root-mean-square (rms) and creepage and in general confirm to all required standards.
2.4.1.2 Earthing and Lightning Protection
The substations earthing system shall be designed and installed in accordance with the recommendation guide for safety in Substation Grounding. The maximum ground fault current (“step and touch” study shall be performed by the CONTRACTOR) shall consider possible power plant and grid extensions. The substation earthing system will be interconnected with the power plant earthing system, as far as possible a uniform design will be applied plant-wide. Surge and lightning arrestors shall be provided for all 330kV OH-lines to meet the grid code requirements.
2.4.1.3 Protection
For Line protection Main-I and Main-II scheme shall be used with distance protection scheme. The Main-II should be from different manufacturer. The protection scheme shall be coordinated with Auto reclosing facility and Teleprotection schemes. Teleprotection signals from protection Main-II shall be transmitted via a Power Line Carrier system. Teleprotection signals from Main-I shall utilize the SDH (synchronous digital hierarchy) equipment connected to the OPGW.
The distance relays, if practical, at the both ends of the line shall be of the same type. Each line feeder protection shall consist of following protection functions:
• Line main protection:
• Distance protection with auto-reclosure functionality • Over-/under voltage protection
• Overload protection • Fault locator
• Line backup protection:
• Distance protection with auto-reclosure functionality • Over-/under voltage protection
• Overload protection • Fault locator
The incoming feeders from the generating units will be protected by the unit protection of the power plant. However, a backup-protection will be installed as part of the substation for following protection functions:
• Over current protection • Earth fault protection
2.4.1.4 Electrical Control and Management System (ECMS)
The ECMS functionality shall follow the power plant philosophy (see 2.3.9)
It is expected that the ECMS capability will be integrated into an integrated substation protection and control system.
2.4.1.5 Electrical Supply, Auxiliary Services
Since the power plant substation consists of 330kV voltage level only, it is not practicable to supply the auxiliary power from the high voltage.
The power supply will be derived from the 400V common main distribution board via 2x 100% feeders, supplying power from the normal plant supply or from the essential Diesel generator unit. Hence no additional LV auxiliary transformers and no essential Diesel generator units are required for the substation. The 400V sub distribution board will have 2 incoming feeders, coupler and automatic transfer device (2 of 3). Non-essential consumers of the substation will also be supplied from this distribution board located in the substation, but will be switched off during Diesel island operation.
The uninterruptible backup power for the substation will be separated from the power plant by installing dedicated systems for the substation:
• 110V DC system for the substation: with 2x 100% battery charger and 2x 100% batteries for 8 hours back up control of the HV equipment and to supply protection-, control- and monitoring systems
• DC system for the substation communication, e.g., 48V DC
• 230V UPS for the substation: with 2x 100% inverter and 2x 100% batteries for 8 hr back up to supply critical control-, monitoring- and communication equipment, which is not available for DC-supply (e.g. HMI, printer, FO-converter)
2.4.2 Substation Extension at Ikot Abasi Area
The overall extension at Ikot Abasi is in process to be built as one of the NIPP projects. QIPP will build out two bays for the double circuit 330 kV TLine.
The two bays will be built out using the same design philosophy and equipment as used at Ikot Abasi substation.
3 BROWNFIELD FUEL GAS PIPING
3.1 General
This Philosophy gives the description of the classification of hazardous areas, earthing and lightning protection of the Brownfield fuel gas piping through QIT to Power Plant area. The philosophy shall generally comply with the current philosophy of the QIT area and applicable GPs.
3.2 Assumptions
All Hazardous area classifications, earthing, and lightning protection, if applicable, will be carried out in accordance with the required API, NEMA, ANSI and Global Practice standard (note if powered from power plant the IEC standards will apply)
No cathodic protection is necessary because piping is on sleepers and not buried.
3.3 Electrical Design Philosophy for Fuel Gas Piping
3.3.1 Hazardous Area Classification
Areas in which an explosive gas atmosphere is present or likely to be present in quantities such as to require special precautions shall be shown and classified as hazardous areas, according to applicable API standard and GPs
3.3.2 Lightning Protection
If necessary, lightning protection devices shall be used according to applicable Global Practice
standard 3.3.3 Earthing
4 TRANSMISSION LINE
This Philosophy describes the electrical design which is concerned with the 330kV Transmission Line from QIT – Ikot Abasi.
4.1 General
The electrical design shall be accordance with PHCN / TCN standard 2007 edition or later.
4.2 Assumptions
The electrical design is according to PHCN / TCN standard and regulations and supplemented by the Owner’s Requirement document.
4.3 Electrical Design Philosophy for Transmission Line
The Transmission Line is going to be a 330 kV double circuit TLine. Twin Bison conductors, ACSR 380/50, 431 mm2 (as specified by TCN) with a continuous current rating under site conditions provide each of the two circuits 1360 A of load carrying capacity. As a result each circuit is rated for a maximum thermal limit of 777 MVA, but due to temporary significant voltage - drop approximately for 550 MW, hereinafter referred to as “approximately 500 MW”. Each circuit or set of lines will have the capacity to carry the entire export power load of approximately 500 MW (ISO), due to N+1 sparing philosophy (i.e., an installed spare). The completed TLine capacity is referred to N+1 as approximately 500 MW, and not approximately 1,000 MW.
4.4 Options
4.4.1 An option to bid high temperature Al conductor to reach 1000 MW per circuit is currently included in the bid documents.
5 ATTACHMENTS
5.1 Attachment 1 – Electrical Single Line Diagram (Simplified)
Electrical Design Philosophy - Single Line Diagram (Simplified) - Simple Cycle Power Plant NGAB-IL-EDSLD-AT-50056
