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Internship Report-
BQPS II
By
Saad Janjua

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Preface
Bin Qasim Power Plant 2 (BQPS II) is a Combined Cycle Power Plant
which houses 3 Gas Turbines and 1 Steam Turbine. The total generation
capacity of the plant is 560 MW, where each of the GTs contribute
130.8MW, whereas the ST contributes 190 MW. The plant site boasts an
efficiency of 45 percent, and uses Natural Gas procured from SSGC, as
its fuel. Harbin Electric, China, was responsible for BQPS II Plant
Engineering Procurement and Commission (EPC).
A scaled map of the Plant Site:

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ADMINISTRATION
Administration of the plant site is divided into three main departments.
The workings of each department are as follows:
 Electrical
Electrical Department deals with, and not limited to the
Generators, Transformers, Switchgears, Gas Insulated
Substation (GIS), DCS and the PLC System installed at the
plant site.
 Mechanical
At BQPS II, the maintenance of all sorts of machinery
including ST and GT falls under the domain of the
Mechanical Department.
 Instruments and Control
The regulatory control and measurement of the power, gas
and water flow of the plant is basically the domain of I&C
Department at BQPS II. This includes but is not restricted to
PEECC, DCS control, Unit Data Highway (UDH), Plant Data
Highway (PDH) PLCs, and vibration, heat and other
Measuring valves and instruments.

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Installations at the Plant Site
NG Compressors and Switchgear:
Three NG Compressorsareinstalled at the plant site, butonly 2 are in working order,
as only 2 NG Compressors fulfill the demand of the plant site. NG Compressors
compress incoming gas at 3Bars to 28 Bars as per requirement of the GTs. The NG
switchgear consists of breakers and supply for the motors and pumps present for the
efficient operation ofNG compressors. NG compressorparameters are all controlled
by Allan Bradley PLC. It includes pumps for the circulation of CCCW, ACW, lube
oil pumps, filters and the NG compressor starting motor. A UPS is also present to
supply power only to the PLCs.
The starting motor of the NG compressor is an MV motor having the rated power
8.5MW and rated current around 850A. The motors contain soft starters to control
the starting current and keep it at a low value. The soft starter operates only for 40
seconds and then it is disconnected once the motor attains speed. The compressor
rotates at 10000 rpm.
Gas Turbines:
Power Plant at BQPS II comprises of 3 GTs. All of the GTs have been
installed adjacent to each other and have the following characteristics:
 GE 9E
 3 bearing machine
 GE Mark VI E control
GT Generator:
 Type: GE 9A5 TEWAC
 Specs:
 2 poles, 3 phase, 50Hz

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 163500 KVA / 130.8MW
 Armature Amps: 6293A
 Armature Volts: 15000V +/-5VAC
 Field Amps: 969A
 Field Exciter Volts: 375V
 Rated Speed: 3000 rpm
 Direction of Rotation from Exciter end: Clockwise
 Lagging Power Factor: 0.8
 Leading Power Factor: 0.93
 Site Elevation: 5m
 Water Cooled (in 35-out 40)
 Production at Y Configuration
Generator Excitation System:
 EX 2100
 Output: 81VDC, 10.3A
 Brushless
Vibration Measuring Equipment:
 Proximity probes
 Flux Probe
 Velocity Vibration Probes
Factors affecting GT performance:
 Ambient Temperature
 Fuel Heating Value
 Humidity
Compressor Protection:
 Inlet Guide Vanes
 Inlet Bleed Valves

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GT Auxiliaries
Power Electrical and Electronic Circuit Centre (PEECC):
Every GT has its own PEECC installed. PEECC is responsible for controlling the
auxiliaries associated with the GTs.
Installed Systems in PEECC:
 Bentley Nevada vibration Protection
 Backup DC batteries for auxiliary lube oil motors
 Ex 2100
 GE Mark VI E
 Normal Incoming (400V)
 Stand-by Incoming
 Motor Control
 SpaceHeater Control
 Isolator Transformer
 Coupling Circuit Breaker
 Essential Breaking
 DC Panel
 Emergency Motor Power
 Inverter
 DC Battery Charger

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Main and Auxiliary Transformers:
The main transformer for each GTG is rated at 170MVA 15KV/220KV (ONAF).
The transformer houses a shell type winding. The transformers are manufactured
by TBEA, China. CTs and PTs are connected to it for instrumentation and
protection purposes.
The electrical protections for the transformers include overcurrent, earth fault,
differential protection and winding temperature protection. The mechanical
protections included are backhauls relay and pressure relief valve (PRV). Bushings
are present for the connections of the transformer.
For the voltage regulation of the transformer there is an ON-LTC (On-Load Tap
Changer) attached to the HV side of the transformer. The LTC is always attached
to the HV side because the current at the HV side is less it is easier to change the
taps. Secondly the HV windings are done over the LV windings on one limb, so it
is easier to change turn ratio from the HV windings.
The auxiliary transformer is air cooled and steps down the generated 15kV to
6.6kV to provide power to auxiliaries and unit PCs and common PCs. The rating of
the transformer is 30MVA. Three auxiliary transformers 15KV/6.6KV are installed
on-site, one for each GT.

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GT GE G60 Protection System
GE G60 is the protection system being used for each of the 3 GTs at plant site. For
General Electric Generators, rating more than 100 MW, G60 is the standard
protection system. At BQPS II, the first parameter of this protection system
includes a GCB (Generator Circuit Breaker) manufactured by ABB which is
controlled by numeric relays for protection of the generator. Numeric relays are
microprocessorbased relays, programmed according to the desired parameters.
Numeric Relays are more reliable and responsive as compared to
electromechanical relays. Each GT is installed with many protection parameters
such as the ones mentioned below.
Differential Protection:
For a GT, differential protection is used to identify any internal (stator) fault of a
generator. There are two CTs connected in the GLAC and GNAC compartments,
on each phase, to feed the relay. The relay works on the difference between the two
currents. Any difference of current causes the relay to operate. Therefore the relay
is programmed to operate on a Differential Current vs Restraining Current curve,
which inherently depends on the ratio error and the phase angle error of the CTs.
This curve consists of two slopes, one for the internal faults of the generator and
the other for any external faults.
Under-voltage Protection:
The Under-voltage protection in a GT, is used to protect the generator when
voltage produced falls below a certain value. Under-voltage can be caused when a
heavy load is added to the system. When the voltage falls it can damage the
machines operating on low voltages, because the current in the generator winding
increases. This protection kicks in at 0.9 times the rated voltage (15KV).The
Under-voltage fault is detected by a definite time overcurrent relay.

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Over-voltage Protection:
Over-voltage protection is triggered when a heavy load is removed from the
system or as a result of regulator failure which cause the voltage produced to
increase. This causes the internal flux of the generator to increase, which results in
core heat up, and produces corelosses. The setting for overvoltage protection is
around 1.1 times the rated value.
Over-frequency Protection:
Over-frequency protection is triggered when a heavy load is removed from the
system. This removal causes the internal flux of the generator, and the produced
voltage value to drop. The alarm triggering value for Over-frequency protection is
52.5Hz.
Under-frequency Protection:
Under-frequency condition can be triggered when a heavy load is added to the
system. It can cause the internal flux of the generator to increase, as a result of
which, the core may heat up and core losses might increase. Generally, the Under-
frequency and Over-frequency protections are collectively called abnormal
frequency protection.
Volts/Hz relay:
This is a backup protection for the abnormal voltage and frequency protections. If
somehow, they fail to operate, Volts/Hz relay can operate and trip the breaker.

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Phase Unbalance:
Phase unbalance protection may be triggered when unequal loads are connected to
each phase. This can cause the productionof negative sequence currents in the
armature windings. As a result, the frequency of the generator may be disturbed,
thus phase unbalance protection should be tripped.
Reverse Power Protection:
It is important that when the turbine output is very low and it starts drawing power
from the system and starts acting as a motor, it should be tripped. This
phenomenon of generator acting as a motor is known as motoring. It acts as an
induction motor. This phenomenon can also be caused when the generator is
energized at low speeds. Forprotection against reverse power, reverse power
relays are used.
Reverse power relay will operate whenever the generator is tripped or turned off.
The setting for the reverse power relay for low forward power is 0.05% of the rated
power which is operated by the relay 32L (NEMA code). The setting for low
reverse power is -0.08% of the rated power which is operated by the relay 32R.
Over-Excitation Protection:
When current in the field winding is increased the excitation increases beyond
limit. It causes the flux to increase and the core to heat up and increase the core
losses. Maximum excitation limit system is used to control the excitation and keep
it under limit. This protection can also be triggered by loss of potential transformer
signal to voltage regulator.

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Loss of Excitation:
When there is a loss of excitation in the field windings, Reactive Power is absorbed
from the system to make up for less excitation. As a result of that, major system
shutdown may occur. Loss of synchronism can also occur, thus causing damage to
the generator. As there is a suddenand significant change in the reactive power
consumption, this fault may be detected by loss of excitation relay.
Black Start Condition:
When the plant site completely shuts down in case of emergency, with no gas
supply, and a ‘dead’ national grid, the following black start conditions apply.
 1 Emergency Diesel Generator of 1.2MW for emergency loads such as Lube
Oil Motor for ST
 800Ah battery Bank for ST and plant auxiliaries

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Heat Recovery Steam Generator (HRSG)
3 horizontal HRSGs have been installed at the plant site, one for each GT. The
function of HRSG is to recover the heat of the GTG exhaust gas. HRSG utilizes
this heat to convert the input DeMin water into steam, which in turn rotates the
steam Turbine. The HRSG system contains two HP feed pumps (6.6KV). One of
the two pumps is the main pump and the other is standby. These are the pumps
which take hot water from condenser, and pump it into HP drums. Two LP feed
pumps and two lube oil pumps are also present which have redundancy too. These
motors are three phase LV motors. A diverter damper skid connects the GT
exhaust gas system to HRSG. Diverter Damper is hydraulically controlled. A
sealing fan is used to seal the GT exhaust gas flow into either direction. HRSG
Boiler being used is of CICI # 703, manufactured in China. The steam collected
from all HRSGs is then collectively sent to the ST.

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The Steam Turbine and Generator
The steam turbine facility is installed behind the CCR. It includes the ST and its
generator.
ST Generator:
 Power Rating: 190MW
 Rated Voltage: 25.75 KV
 Rated Current: 8000A
 Hydrogen Cooled
 Rotation Speed:3000 rpm
STG Cooling:
The auxiliary system for the generators include hydrogen cooling, water cooling,
seal oil system and lube oil system. A generator has mainly four important parts,
stator core, stator winding, rotor core and rotor winding. The stator winding is
cooled by the demineralized water produced in the water treatment plant. It has the
conductivity of almost 0.125S/cm. The cooling of rotor core, rotor winding and
stator core is done by Hydrogen gas coming from the hydrogen plant. The
hydrogen gas is present between the rotor and the stator winding.
It is important that the bearings of the generators have properlubrication and for
that purpose, lube oil is used which is circulated by pumps. A sealing oil system is
also maintained to trap the hydrogen gas in the generator. The pressure of oil is
greater than the pressure of hydrogen to keep it inside. There are four CCCW
hydrogen coolers for the cooling of hydrogen too.
Excitation System:
The exciter for the steam turbine generator is UNITROL-5000 and it provides the
rated current of 1100A and a rated voltage of 230V. The static exciter consists of a
generator as well as thyristor banks. An FCB (Field Circuit Breaker) is used to trip

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the circuit for excitation. The excitation transformer is a 2500kVA transformer and
provides AC to thyristor banks. This AC voltage is then converted to DC. A
control mechanism is used which is to control the magnitude of field current. On
gaining load, a voltage drop occurs, as a result of which, additional current is
needed for the exciter to producemore terminal voltage. This is the reason why
thyristors and not diodes are used to control the average voltage and current.
Protection Systems for STG:
The protection system for ST generator is similar to that of GT generator. ABB
protection system, RET-650 and/or REG-650 for transformers and generators
respectively. The exciter has a crowbar circuit for protection too. It trips when fault
occurs in the stator. It grounds all the flux present on the bodyof the rotor so that
the generator doesn’tact like a motor.
 EH Pressure Low Trip
 Lube Oil Pressure Low Trip
 Condenser Value Low Trip
 Over speed of TSI Trip
 Axial Displacement Trip
 Rotor Vibration Trip
 Turbine Differential Expansion Trip
 Generator Fault Trip
 HP Casing Temperature Differential Trip
 Over Speed of DEH Trip
 Loss of Power DEH Trip
 Exhaust Temperature High Trip
 Manual Trip
 Bearing Temperature and Return Oil Trip

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Maintenance
Power Systems at BQPS II, like any other plant, require constant monitoring and
maintenance. Maintenance forms a significant portion of the daily chores of the on-
site workforce. Mentioned below are the basics of maintenance practice used at
BQPS II.
Plant Maintenance Types:
 Preventive Maintenance
This type of maintenance takes place at scheduled intervals.
 Corrective Maintenance
This type of maintenance is undertaken after an error occurs at the
plant site. This is also known as Breakdown maintenance.
Causes:
 Errors in Synchronizing
 Under/Over frequency operation
 Lightning surges
 Faults i.e. short circuits
 Single phase or out of phase operation
 Unbalanced load
 Overload
 Over/Under voltage
 Loss of field
 Predictive Maintenance
The engineering staff plans predictive maintenance by using
measurement tools to get an early diagnosis of a possible error in
the system.

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 Operating Maintenance
 Coolers
Accumulation of sludge may start to vary difference in
input/output cooling water temps. Continually decreasing
efficiency indicates that cleaning needs to be done.
 Air Filters:
Dirty air filters raise working temp of machine, also
accumulate dirty air. Examine filters once a week to avoid
physical damage.
 Shaft Grounding Brush:
Check shaft to ground voltage atleast once a week. Brushes
must not be allowed to wear beyond a certain limit.
 Excitation:
Normally exciter components require little or no
maintenance. Equipment should be kept dry and clean.
 Inspection of Generator Parts
 Armature Core:
Should be inspected for hot spots or damaged punchings. The
inside of a generator should be checked for evidence of oil
which indicates oil leakage past the oil detectors.
 Armature Windings:
Checked for leakage oil and over-heating.

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Water Usage at Plant Site
Water Intake Facility:
Water Intake facility includes basic filtering of seawater and pumping it to the rest
of the plant. The electrical pumping of water takes place through certain LV and
MV motors. At the sea water intake, there are two ACW (Auxiliary Cooling
Water) pumps and three STCW (Steam Turbine Cooling Water) which are all MV
pumps. The ACW pumps are rated at 670kW each, whereas the STCW pumps are
rated at 2.5MW pumps each. The STCW Pumps carry the cooling water to
condensers. These pumps have journal bearing to take care of the radial movement
and thrust bearings to take of the axial movement. These pumps also have inbuilt
lube oil system and cooling system for lubrication and cooling.
Sodium Hypochlorite (NaOCl) Manufacturing Plant:
Sodium Hypochlorite is by its nature, an antimicrobial agent, which
suppresses/kills microbial growth. NaOCl is produced by the process of
electrolysis. In this plant, water is passed electrolyzed in six different electrolysis
chambers. In each chamber, water is electrocuted at 55KA, 24V to produce
NaOCl. Transformers are used to step down 6.6KV to 235V. This voltage is then
converted to 23V DC using thyristor banks (water cooled)in the Rectifier
Chamber. NaOCl is added to all the water which is pumped from the water intake
facility to inhibit the growth of organic matter, which might later block the water
ducts being used for cooling or other purposes.
Water Treatment Plant:
Water Treatment Plant is an integral part of the CCPP. It produces Demineralized
(DeMin) Water which has two essential functions; Firstly, being converted to

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steam to drive Steam Turbine, and secondly as cooling water for NG Compressor
lube oil and the ST Generator Stator Windings. Sea water has a conductivity of 55-
60K micro Siemens, and a turbidity of 35NTU, whereas, DeMin water has a
requirements of conductivity less than 10 micro Siemens, and turbidity less than
0.1 NTU. Question arises as to how this significant change in water’s properties is
brought about. Shown below is a schematic of the process involved in making
demineralized water from sea water.

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Installed Switchgear at BQPS II
6.6kV Switchgear:
The 6.6kV switchgear is placed in the CCR building. It controls the supply for all
the MV motors. It contains 3 bus bars which can be coupled using bus couplers. The
supply comes from UAT (Unit Auxiliary Transformer) through three buses. It
supplies powerto various areas of the plant as mentioned below. The circuit breakers
used are VCBs (Vacuum Circuit Breakers), manufactured by Schneider.
6.6KV Loads:
 Black Start Diesel Generator
 2 VFDs (Hiconics)
 12 Transformers (6.6KV/400V)
 27 motors
 NaOCl Plant Transformers (6.6KV/235V)
400V Switchgear and ATS:
The 400V switchgear is also known as the common PC which contains the
transformers which step down 6.6kV coming from the UAT to 400V. It contains the
supply system and breakers for all the LV motors and other auxiliaries which are
operated at this voltage. This switchgear is present in the CCR so the feedback from
all the breakers goes to the CCR and is remotely operated. There are two 400KV bus
bars which are also coupled together.
ATS (Auto Transfer Switch) is a systemincorporated at the plant site which provides
supportfor LV and MV supply. In case of any tripping, the ATS distributes load on
other online transformers evenly ATS panels are present in the net relay room in
CCR. TS is an integral feature of the plant and any improper operation of the ATS
can result into problems in the auxiliaries present on the plant site.

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Gas Insulated System (GIS)
The GIS houses Bus bars and extend for a length of 1 km from the GIS. An
underground cable (XLPE) is used to carry the supply from the transformers to the
GIS. The bus bar scheme used for carrying the supply for transmission is single
bus double breaker type. This scheme is economical as well as reliable as
compared to single bus single breaker scheme. It includes breakers, isolators, earth
switches, CTs and PTs which are all gas insulated. The gas used for insulation is
SF6 which is a common practice at 220kV systems.
The advantage of using SF6 over vacuum is that it reduces the size of the substation
and less spaceis needed for isolation of equipment. The incoming lines in the GIS
are from the transformers of GT and ST transformers. The outgoing lines are KCR-
I, KCR-II, Short Line 1 and Short Line 2. The short lines are the lines which are
coupled the plant BQPS-1. A bus coupler is used for switching from one bus to the
other whenever needed.
The GIS also includes a control room and also houses the protection systems. The
protection system present in the control room sends signal to the protection system
of the GIS control room and as a result
of that communication takes place
between both the systems. This is how
the line breaker is going to be tripped.
The only breaker for the ST generator
is the line breaker which should trip in
any fault situation. A DC system is
present to supply power to the control
system. Wattmeters are also present to
calculate the energy utilized.
Map of GT connected to the Bus Bar at GIS.

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Central Control Room (CCR)
Central Control Room houses all the HMI. It centralizes all the communication on the
plant site. The CCR has 8 display panels which display all the numbers (data) from every
corner of the plant, (DCS) and provides read and control options all under one roof. All
the alarms that generate in the machinery installed at the plant show at CCR. CCR also
coordinates all the work permits and tagging system for maintenance related work at the
plant. 6.6KV switchgear is also housed in the building where CCR is present.
THE END