HOTLINE MAINTENANCE

TECHNIQUE IN POWER

SYSTEM

INTRODUCTIONHOTLINE MEANS ENERGISED ELECTRICAL POWER LINE.HOTLINE MAINTENANCE - USED FOR ATTENDING WORKS ON ENERGISED ELECTRICAL SYSTEM WITHOUT INTERUPTING POWER SUPPLY.

PREVENTIVE MAINTENANCE / FAULT RECTIFICATION CAN BE CARRIED OUT

METHODS

HOTSTICK TECHNIQUE

BAREHAND TECHNIQUE

HOTSTICK TECHNIQUE

LINEMAN REMAINS AT GROUND POTENTIAL

WORK IS CARRIED OUT WITH LONG, LIGHT WEIGHT & HIGHLY INSULATED EPOXY GLASS/GLASS FIBRE STICKS (HOT STICKS ) MAINTAIN SUFFICIENT CLEARENCE WITH LIVE PARTS

FAULTS ON EARLY STAGE CAN BE RECTIFIED

USED UPTO 230 KV SYSTEM

BAREHAND TECHNIQUE

LINEMAN REMAINS AT LINE POTENTIAL

WORKS DIRECTLY WITH HAND

WEARS SPECIALLY MADE CONDUCTIVE SUIT, BOOT, GLOVES AND SOCKS TO KEEP IT IN SINGLE VOLTAGE

MAINTAIN SUFFICIENT CLEARANCE TO EARTH POINTS

USED UPTO 765 KV SYSTEM

FEATURES OF 230/400 KV YARD IN TS-IICONSISTS OF 2 MAIN BUSES WITH TRANSFER BUS EACH IN 230 KV & 400 KV YARD

22 BAYS IN 230 KV YARD AND 13 BAYS IN 400 KV YARD CONSISTING OF UNITS, STS, ICTS, MINING & GRID FEEDERS

EACH BAY IS EQUIPPED WITH BUS ISOLATORS, BREAKER, LINE ISOLATOR, CT, CVT, LAS ETC.,

ALL THE ABOVE FORM PART OF THE GRID AND PLAY VITAL ROLE IN SMOOTH TRANSFER OF POWER GENERATED BY OUR 7 UNITS

CURRENT PRACTICE IN YARD MAINTENANCE

HALF YEARLY ROUTINE MAINTENANCE CARRIED OUT THRO ANNUAL MAINTENANCE CONTRACT

WORK ON BUS ISOLATOR IS CARRIED OUT BY CLEARING THE CONCERNED BUS AND TAKING THAT FEEDER ON TRANSFER BUS

WORK ON EQUIPMENTS VIZ., (BREAKER),LINE ISOLATOR, CT, CVT, LAS ETC., IS CARRIED OUT BY SHUTTING DOWN THE CONCERNED FEEDER

BUS CLEARING AND LINE SHUT DOWN ARE CARRIED OUT WITH PRIOR APPROVAL FROM THE CONCERNED AUTHORITY

WORKS THAT CAN BE CARRIED OUT USING HOT LINE MTCEPERIODICAL TIGHTNESS IN LIVE BUSESREPLACING OF DAMAGED ISOLATOR CONTACTS,ISOLATOR & BREAKER PAD CLAMPS AND DAMAGED CONDUCTOR CHANGING OF FAULTY INSULATORS IN STRUNG BUSBYPASSING T CLAMPS AND BUS BAR JUMPERS OF LOW CURRENT PATHTIGHTENING OF BOLTS AND NUTS ON CLAMPS

ADVANTAGES

BUS CLEARANCES CAN BE REDUCED.EXTEND THE LIFE OF ISOLATORS ETC BY MINIMISING THEIR FREQUENT OPERATIONRISK OF TRIPPING OF UNITS/ FEEDERS IN CASE OF ANY BUS FAULT DURING SINGLE BUS OPERATION CAN BE AVOIDED WHICH PREVENTS FURTHER CASCADE TRIPPING IN GRIDSAVE ENERGY, EQUIPMENT AND TIME BY MINIMISING SHUT DOWNS

LIMITATIONSNEEDS SPECIAL IMPORTED AND RECOMMENDED TOOLSNEEDS QUALIFIED, TRAINED AND EXPERIENCED PERSONSCAN NOT BE CARRIED OUT UNDER ADVERSE WEATHER CONDITIONSINVOLVES HUGE INVESTMENT FOR ESTABLISHING THE HOT LINE CREW AND IMPORTING SPECIAL TOOLS

FEASIBILITY STUDY

ADVANTAGESMINIMISATION OF FREQUENT OPERATION OF EQUIPMENTS ESPECIALLY BUS ISOLATORS

LIMITATIONSC0MPLICATED PROCEDURE FOR WORKS IN CURRENT FLOWING PATH FOR EXAMPLE TO ATTEND BUS ISOLATOR ALIGNMENT PROBLEM,IT REQUIRES:CHANGE OVER TO TRANSFER BUSBUS ISOLATOR IS TO BE ELECTRICALLY SEPERATED FROM THE MAIN BUS VOLTAGE WHICH INVOLVES DISCONNECTION OF JUNCTION POINTS

LIMITATIONS-CONTINUED

IN ABOVE CASE ,THERE IS A POTENTIAL RISK OF DISTURBING NEIGHBOURING BAYSAVAILABILITY OF ONLY VERY LIMITED AGENCIESMOBILISATION & DEMOBILISATION OF CREW AND EQUIPMENT IS COSLY FOR PIECE MEAL WORK WEATHER WILL HAVE MORE SAY WHILE CARRYING OUT THE WORK

MAINTENANCE COST ANALYSIS400KV BAY(USING HOT LINE TECHNIQUES):TIGHTNESS CHECKING,CLAMPS REPLACEMENT ETC., EXCEPT ISOLATOR ALIGNMENT FOR ONE BAY ---------------------- Rs. 40,000BUS ISOLATORS ALIGNMENT (2X40000)----- Rs. 40,000TOTAL COST FOR ONE BAY ---------------------- Rs. 80,000TOTAL COST FOR 13 BAYS ----------------------- Rs.10,40,000

MAINTEANCE COST ANALYSIS-CONTINUED400KV BAY (USING ANNUAL MAINTENANCE CONTRACT):1. TOTAL COST FOR ONE BAY INCLUDING ALL EQUIPMENTS USING OFF LINE METHOD------- Rs. 3,300 2. TOTAL COST FOR 13 BAYS -------------------------- Rs.42,900

COST OF HOT LINE MAINTENANCE OVER OFF LINE METHOD ---------------- 24.24 times higher

MAINTEANCE COST ANALYSIS-CONTINUED230KV BAY(USING HOT LINE TECHNIQUE):TIGHTNESS CHECKING,CLAMPS REPLACEMENT ETC., EXCEPT ISOLATOR ALIGNMENT FOR ONE BAY ---------------------- Rs. 25,000 2. BUS ISOLATORS ALIGNMENT (2X30000)----- Rs. 60,000TOTAL COST FOR ONE BAY --------------------- Rs. 85,000TOTAL COST FOR 22 BAYS ---------------------- Rs.18,70,000

MAINTEANCE COST ANALYSIS-CONTINUED230KV BAY(USING ANNUAL MAINTENANCE COTRACT):1.TOTAL COST FOR ONE BAY INCLUDING ALL EQUIPMENTS USING OFF LINE METHOD---------- Rs. 3,6002. TOTAL COST FOR 22 BAYS ---------------------------- Rs.79,200

COST OF HOT LINE MAINTENANCE OVER OFF LINE METHOD --------------- 23.61 times higher

CONCLUSIONSIN EQUIPMENT OPERATION POINT OF VIEW HOT LINE METHOD IS ADVANTAGEOUS.POLICY DECISION HAS TO BE TAKEN AS THE MAINTENACE COST WILL BE APPROXIMATELY 24 TIMES HIGHER THAN PRESENT MAINTENANCE COST

CONCLUSIONS-CONTINUEDONLY ONE KNOWN AGENCY IS AVAILABLE FOR BARE HAND TECHNIQUE WHICH MAY LEAD TO THE NON-AVAILABILITY OF THE CREW AS AND WHEN REQUIED

MOBILISATION OF EQUIPMENT & CREW WILL BE TIME TAKING AND COSTLY FOR ANY SPECIFIC EMERGENCY WORKS