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Post on 19-Nov-2014
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Reliability Issues of Generator Control & Protection System at PH#5
Smarak SwainManager, IEM
Under the guidance of:
Mr. D.B.GhoshSenior Manager, IEM
Problem Statement
Reliability issues pertaining to uninterrupted supply of power
Necessary changes in generator control system for effective control
Fool-proof protection of generator through modern numeric system wherever needed
Lower maintenance cost by moving towards automation
Constraints
Though PH#5 is new, most equipments are old. System brought from PH#3
Generator excited by separate DC generator PH#5 runs at low manpower. Low manpower
is the need of the hour to stay competitive in the industry
Exciter Upgradation
Separate DC Excitation Brushless Excitation Static Excitation
Separate DC Excitation System
Static Excitation for PH#5
Carbon dust from commutator brush wear causes stator overheating
There are commutator problems such as sparking & rotor earth fault caused by carbon dust
Oil leakage is a major problem in DC exciter of PH5 Static excitation improves efficiency Faster time response Safety concerns
Digital Voltage Regulators (D-AVR)
Far more reliable than analog system Multiple operating Modes: PF, VAR modes D-AVRs provide fast transient performance for
improved voltage response to system disturbances Programmable generator voltage soft start to build
voltage to rated output eliminating need to start in manual
Human Machine Interface Analog AVR in PH5 often faces the problem of
hunting
BHEL AVRs
PROS Most electrical and
electronic instruments in PH5 are of BHEL make. Easier retrofitting possible
We have been dealing with BHEL for a long time
BHEL’s loyal and prompt service makes it a favourite
CONS BHEL’s products are
usually not its own R&D products. Products are not the latest in market
BHEL’s digital-AVR is costly
Few monitoring and add-on facilities available in excitation systems of other vendors are not available
ABB AVRs (PROS)
All logical and sequential control functions for different modes of operation are built-in, and so there is no necessity of any engineered applications like stand-alone PLC programs
Control interface to the control room available through remote HMI facility
Built in Data Logger allows System Debugging over wide time areas
Built in Fault Logger stores up 99 Faults Static excitation system (~70 lacs) cheaper than
that of BHEL excitation system (~80 lacs)
GE Energy D-AVRs (PROS)
Incorporates most advantages of ABB AVRs IGBT based digital controller provides faster
variation in firing angle compared to thyristor based controls
Digital AVR supplied by GE Energy (~ 10 Lacs) is far cheaper than those by ABB (25 Lacs) and BHEL (40 Lacs)
Auto-synchronizer is an optional integrated feature in case of GE Energy system
ABB & GE Products (CONS)
There are apprehensions about performance of ABB & GE Energy systems. GE Energy salesperson has however provided a list of plants using their products world over. Contacts of their customers in India have also been provided
Doubts regarding prompt service and expert commissioning engineers persist
Parts are shipped from abroad. Availability of spares may be a problem
Since GE Energy’s EX2100 doesn’t have a big market in India, they may not have expert technical staff in India
Budgetary Allocations
BHEL (Approximate Figures) One D-AVR: Rs.40,00,000 Three D-AVR: Rs.120,00,000
GE ENERGY (Approximate figures) One Digital AVR: Rs.10,00,000 Three Digital AVR: Rs.30,00,000 Two Spare AVR: Rs.20,00,000 Total: Rs.50,00,000
Protection Relays at PH#5
All relays in generation protection panel are old solid-state relays
Slow response Malfunctioning of some relays No provision for self-diagnostics and testing Large Maintenance Related Shutdowns Problems in fault monitoring Over-heating of relays
Cautions…
Critical failure in a numerical relay can degrade protection more significantly than a failure in older systems. Adequate backup protection should be provided accordingly
Numerical relays are microprocessor based relays. Most operators being in the middle and upper age group need to be trained on its operation and monitoring.
Making a retrofit numerical relay connection shall require overhead costs other than just the cost of relay installation
Budget
APPROXIMATE COST OF INSTALLING NUMERIC RELAYS WILL BE:
Cost of Numerical relay: Rs.3,50,000
Cost of back-up relay: Rs.3,50,000
Overhead: Rs.2,00,000
(Accessories and installation cost)
Total Cost Rs.9,00,000
Budgetary Rationale
Power Cost/KWH (as per LDC): Rs.1.8
Power Cost/MWH: Rs.1800
Power output of generator in 1 hour:Rs.43,200 (24MW average production)
Uptime for Rs.9 lacs revenue: 900000/43200 = 20.833 Hours
If we can prevent a downtime of 21 hours, due to maintenance shutdown or breakdown, we can recover the financial investment.
Thank You
Numeric Relays
NUMERIC PROTECTION
OLDER RELAYS
100% Stator Protection
95%
Complete Over-exitation Protection
Two Set Point Over-exitation Protection If Any
Unbalanced Armature Current Protection
Negative Sequence Protection provided
Frequency tracking Algorithm
Poor Frequency Response
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