MAINTENANCE, TROUBLE SHOOTING TESTING OF …

1 ACBMAINTENANCE, TROUBLE SHOOTINGTESTING OF RELEASESSAFE & SUREL&T SWITCHGEAR15 SAFE & SUREL&T SWITCHGEARESPSERVICEMANUALBREAKER IS NOT CLOSINGBREAKER IS NOT TRIPPING WITH UNDERVOLTAGE OR SHUNT CIRCUIT BREAKERSCOMPLAINTCOMPLAINTPROBABLE CAUSEa) Undervoltage release not connected with ) Undervoltage release, Shunt release, Magneto thermal release connecting link not adjusted ) Magneto thermal release removed from ACB, but trip bar of release kept ) Latch of the mechanism spring not in proper position or ) Under voltage release coil burnt out or open circuited.)fBimetal element of magneto thermal release bent ) After overload or short circuit fault, breaker not reset (ONLY FOR MANUALLY RESET TYPE ACB.)h) Sticking of tripping mechanism due to excess SOLUTIONa) Give rated voltage to under voltage ) Adjust the connecting linkageof releases ) Lock the trip bar at ) Fix the spring ) Replace the under voltagerelease.

2 FReplace the magneto ) Reset the breaker by pressing OFF / RESET ) Clean the tripping mechanismwith CRC 2-26 & grease them,(refer section on greasing)PROBABLE CAUSEa) Shunt release does not get ) Supply of under voltage release does not get cut ) Link pins of Undervoltage or shunt release ) Due to dust release becomes SOLUTIONa) Check control wiring ofshunt release & ensure that shunt release gets ) Check control wiring. c) Ensure that pins are in ) Remove the dust from the release & clean it withCRC & SUREL&T SWITCHGEARESPSERVICEMANUALBREAKER IS NOT TRIPPING BY MANUAL TRIP PUSH BUTTONCOMPLAINTCOMPLAINTCOMPLAINTPROBABL E CAUSEa) Trip push buttons connecting link is short. (Not adjusted properly.)b) Latch of the mechanism. jammed because of IS NOT TRIPPING IN CASE OF OVERLOAD OR SHORT CIRCUIT FAULTPROBABLE CAUSEa) Connection between and magneto thermal release is loose or open ) Overload setting of magneto thermal release is more than actual load ) Magneto thermal release linkage not adjusted SOLUTIONa) Tighten the terminals of in case of open ) Make the overload setting of ACBas per actual load ) Connect the linkage of magneto thermal release to trip bar properly & ensure its tripping CONTACTS OF ONE OF THE POLE OF ACB NOT CLOSINGPROBABLE CAUSEa) Excessive dust accumulated in the pole ) Nylon rollers of the pole assembly are not ) Pole connector setting ) Nylon rollers of the pole assembly are SOLUTIONa) Clean the pole assembly mechanism with CRC grease and dust with brush & apply fresh ) Clean the nylon rollers with CRC2-26 and relubricate them.

3 (refer section on greasing)c) Consult the manufacturer of Circuit Breakerd) Consult the manufacturer of Circuit SOLUTIONa) Adjust the push button link ) Clean the latch of the mechanism with CRC & SUREL&T SWITCHGEARESPSERVICEMANUALCOMPLAINTCOMPL AINTCOMPLAINTCOMPLAINTPITTING ON MAIN CONTACTSPROBABLE CAUSEa) Arcing contact gap is not adjusted ) Thickness of arcing contact is reduced below the specified limit. (> mm)POSSIBLE SOLUTIONa) Adjust the gap of arcing contacts,it should be + or mmb) Replace both fixed and moving arcing ON ARCING CONTACTSPROBABLE CAUSEa) Rough deion plates of arc ) Breaker is operated without arc chute in SOLUTIONa) Clean the deion plates and sideinsulating strips of arc chutes ) Always operate ACB with arc chute inposition & keep the arc chutes cleanPROBABLE CAUSEa) Threads of mechanical indicating assembly worn ) Shutter assembly is not properly set in the cradle.

4 C) Secondary isolating contactsnot matching ) Dovel pin broken. e) Telescopic rail becomes SOLUTIONa) Replace the mechanical ) Fix the shutter assembly properly inthe ) Match the fixed and movingsecondary isolation contacts ) Replace the dovel ) Clean the telescopic rail with CRC2-26. Remove dust, grease &relubricate CAUSEa) Poor termination (High Milli- Volt drop across termination on ACB.)b) Dusty ) Use of undersized cable orbus ) High ambient SOLUTIONa) Clean the terminals with CRC 2-26and do proper retermination. Ensurethat milli volt drop within ) Do periodic cleaning of circuit ) Use cables or bus bars of ) Reduce load current or select & installcorrect rating of IS NOT RACKING IN THE CRADLE FREELYOVERHEATING18 SAFE & SUREL&T SWITCHGEARESPSERVICEMANUALBREAKER IS NOT CHARGING WITH MOTORBREAKER IS NOT CLOSING REMOTELYCOMPLAINTCOMPLAINTPROBABLE CAUSEa) Motor is not getting ) Loose connections insecondary isolating ) Motor is burnt SOLUTIONa) Check the limit switch of it if it is damaged.

5 B) Fix the secondary isolating contacts properly,c) Replace the SOLUTIONa) Breaker is not in service positionb) Closing coil is not getting supply,c) Closing coil burnt out or open SOLUTIONa) Take the breaker in service ) Check control circuit and ensure that coli gets ) Replace the closing coil,19 SAFE & SUREL&T SWITCHGEARESPSERVICEMANUALCOMPONENETS TO BE GREASEDGREASE TO BE USEDSCHEDULE FOR GREASINGP) PINS1) ROLLER ASSEMBLY2) POLE LATCH SPRING RETAINER3) STAINLESS STEEL PROFILE4) SLOTTED GUIDE5) POLE LATCH NYLON ROLLERS6) CRANK7) PLATE1) LITHON 2 OF HINDUSTANPETROLEUM OR SYNTHOLUBE10 OF LEACH(FOR COMPONENTS SHOWN IN CIRCLE)2) BALEMEROL MOLY GREASE ML OFBALMER LAWRIE & CO.(FOR COMPONENTS SHOWN IN SQUARE)EVERY 500 OPERATIONS OR 6 MONTHSSECONDARY ISOLATING CONTACTSSLIDING SURFACE OF FIXED & MOVING CONTACTS WITH PETROLEUM JELLYSERVICE OF ACBsLITHON2 MOLYGREASE ML76 PLATECRANK20 SAFE & SUREL&T SWITCHGEARESPSERVICEMANUALGREASINGCOMPON ENTS TO BE GREASEDCOMPONENTS GREASED FOR LIFECOMPONENTS NOT TO BE GREASEDA Breaker normally greased and operating in a dust-free and non-corrosive atmosphere over a period of two years can undergo its normal cycle of mechanical endurance without greasing.

6 As ideal service conditions are hardly encountered, it is recommended to regrease the breaker after a cycle of 500 operations or six months, whichever is rubbing surfaces in the mechanism, poles etc. are to be greased except thecontacts (copper on copper) and sintered bearings. Prior to greasing, these surfacesshould be throughly cleaned. Excess grease must be wiped Lithon 2 of Hindustan Petroleum (Yellow)grade of pole parts FRCD gears in electrical Balmerol Moly grease ML (Black) of Balmer Lawire & Co. for mechanism in mechanical & electrical following components are provided with self-lubricating sintered rings impregnated with grease for life. Trip rod Intermediate shaft of manual control Free-return charging device for electrical operation. All releases Main isolating contacts and cradle terminals Earthing terminal Secondary isolating contacts21 SAFE & SUREL&T SWITCHGEARESPSERVICEMANUALTESTP roper termination test of Cables, Busbars and Crimping of Cables can be tested by measuring Milli-Volt drop across them.

7 If the termination is not good, loose/unclean/ less contact area then the joint resistance increases. The voltage drop across such joints will be more as compared to a good of contacts of any switchgear can be tested by measuring mV drop, across them. If the contacts are pitted / unclean then contact resistance increases, so we get high mV drop across TERMINATION TESTJ oint LocationTest CurrentMax. mV DropGood mV to Bus Barbar / Link to 1 Terminal to Lug to 2 Terminal to Lug to 2 Cable to Cable Lug (across crimping joint)Typical Milli -Volt Drop Values22 SAFE & SUREL&T SWITCHGEARESPSERVICEMANUAL8. OVERLOAD AND SHORT CIRCUIT TESTING OF the circuit breaker by pressing the trip push button of the release as shown is necessary to check the mechanical setting of the we will be TESTING circuit breaker by Secondary Injection Method, disconnect all the wires from magneto thermal the release at point for all three phase as shown normally open (NO) auxiliary contact of ACB in series with test panel'sauxiliary contact.

8 (This is to cut off the current flowing through the release as soon as ACB trips.) out the rated CT secondary current. For L & T ACB rated CT secondary current is the test current as follows :*For 2 times overload (200%)Test current=Rated CT secondary current x No. of times of overload= x 2= amps*For 3 times overload (300%)Test current=Rated CT secondary current x No. of times of oveload= x 3= ampsT1 M1 T2 M2 T1 M1 T2 M2 T1 M1 T2 M2 STrip push & SUREL&T SWITCHGEARESPSERVICEMANUALI nternal connections of the DN release with CT is shown in the following TESTINGINTERNAL WIRING DIAGRAM OF NEW DN RELEASECTR PhaseCTY PhaseCTB PhaseT1M1T2M2T1M1T2M2T2M1T2M2SO / LBime xxxSCMagneticC xxxShortinglink forfixing E/FreleaseNote :For TESTING overload pass current between T1 % TESTING short-circuit pass current between S & M1 or on overload TESTING we have pass current between T1 % T2 terminals of the release.

9 Contact the output terminals of the panel to T1 and T2 terminals of releases as shown below (use sq. mm copper wire).To Current Source (Panel)T1 M1 T2 M2 T1 M1 T2 M2 T1 M1 T2 M2 S24 SAFE & SUREL&T TIME in OF RATED 1 7 8101216 18 OPERATING LIMITS THERMAL} triptime curveMinimum triptime curveCurrent vs Time (I-T) characteristic of DN type release is given below. Find out the minimum and maximum trip time for 200% and 300% overload the curve and note it down in table & SUREL&T SWITCHGEARESPSERVICEMANUALS witch on the supply and adjust the test current. Immediately switch off the current. Keep the variac at adjusted position. Reset the time counter. Cool the release for about 10 setting = oneSr. Current (Amp)Trip Time in SecondsRemarkOK / Not per Current (Amp)Trip Time in SecondsRemarkOK / Not 1 SHORT CIRCUIT TESTINGi)For short circuit TESTING , connect the output terminals of current control panel to S and M1 or M2 terminals of )When M1 is connected test current should be 45 Amp and for M2 the test current should be 57 Amp.

10 (M1 and M2 magnetic threshold are of the order 500% to 700% of CT secondary.)iii)Close the )Switch on the current and check for instantaneous tripping operation of : Connect the wires of magneto thermal release as per wiring on the current and check trip time of the ACB. Fill up the data in above & SUREL&T SWITCHGEARESPSERVICEMANUALMICROPROCESSOR BASED RELEASE SR 21SR 21 The self powered SR 21 release has four zones of protection1. Protection against overload : Long Time2. Protection against short circuit : Short Time3. Protection against short circuit : Instantaneous4. Protection against Earth fault : Ground faultThe release is fed by three current tranformers with nominal CT secondary current 750 release provides, choice of characteristics suitable to load is provided with thermal memory changing the position of this switch to ACTIVEPOSITION the release provides COLD & release also displays the type of fault under which the breaker trips through itsindicators.