Air Circuit Breaker

I.B. 32-150-3

RECEIVING • OPERATION • MAINTENANCE

"De-ion"

; -vji Type DH m

! Type Kv Amps Kva Vi* i i| 50-DH-250 5.0 1200 250,000 50-DH-250 5.0 2000 250,000 75 DH 150 7.5 600 150,000 / - - 75-DH-150 7.5 1200 150,000 75-DH-250 7.5 1200 250,000 I ; 75 DH ? 250 7.5 2000 .1 - - 250,000

'' 2 ' 75-DH-500 7.5 1200 500,000 75-DH-500 7.5 2000 500,000 150 DH 150 15.0 600 150,000 3 - - 150-DH-250 15.0 1200 250,000 150-DH-500 15.0 1200 500,000 150-DH-500 15.0 2000 500,000

! . At T • , : ELECTRIC 4 WESTINGHOUSE CORPORATION SWITCHGEAR AND CONTROL DIVISION EAST PITTSBURGH WORKS EAST PITTSBURGH, PA. { NEW INFORMATION EFFECTIVE OCTOBER, 1947 (R*p. 3-49) Printed In U S,A.

* A e • N \ 4 1

i o

One of the outstanding improvements in modern power distribution has been the “development of the air circuit breaker by Westinghouse for distribution circuit voltages. On circuits where the duty on breakers is heavy, long life with a minimum of maintenance makes the "De-ion 7 ' air breaker an outstanding performer. In the type DH magnetic "De-ion" air circuit breakers, Westing- house offers a complete standard line for circuits from 2.3 to 15 kv. This instruction book applies to breakers for the 7.5 and 15 kv classes and to 5 kv, 250,000 kva breakers which have the same class of insulation and general construction.

Each of the type DH air circuit breakers is three-pole, electrically operated, and is built as a complete horizontal drawout unit for metal-clad switchgear. Breaker units of the same rating are interchangeable so that changing breakers f is a matter of minutes. Since they are drawn out horizontally, no lowering or lifting is necessary. Steel barriers and automatic interlocks prevent contact with live parts while the breakers are being changed. As in the case of most high voltage electrical equipment, these breakers should be inspected and maintained at regular intervals in order to obtain the most dependable performance. 3 2

| I mm :1W -

I.B. 32-150-3 AIR CIRCUIT BREAKER

!1 DESCRIPTION

The type DH air circuit breaker is a three-pole, rier between personnel and live parts when the electrically operated, horizontal drawout unit for unit is in the cell. This barrier assembly is in two metal-clad switchgear. In the type designation, parts for convenience in handling. the numbers preceding DH indicate the voltage rating in hundreds of volts, and the numbers follow- * ing DH indicate the maximum interrupting rating CHUTE in thousands of kva. The various ratings have A ARC similar many parts in l . r structural features and i * common. P- 1 BLOWOUT Fig. 1 shows a type 150DH250 breaker with -MAGNET the main barrier assembly and one arc chute re- CONDENSER moved. This shows clearly the arrangement of the - BUSHING FINGER arc chutes and blowout magnet assemblies, the con- CONTACTS tacts and insulated operating rods, and the sole- A noid operating mechanism These components are MOVING . CONTACT ARM supported in a welded steel frame mounted on flanged wheels for guiding it into the metal clad OPERATING - TRIPPING ROD cell. In the lower part of the frame also is located TRIGGER- the levering-in device for moving the breaker into final contact engagement. This device is inter- SOLENOID locked with the mechanism to prevent inserting or MECHANISM withdrawing the breaker with the contacts closed. Also located in the lower part of the frame are the secondary contacts for automatically disconnecting the control wiring when the breaker is withdrawn, the auxiliary switch, and other auxiliary devices. TRIP COIL A barrier assembly is placed on the breaker before it is rolled into its . The front sheet is cell of FIG. 1. Type 150 DH 250 Circuit Breaker with Main one-eighth inch steel to form a grounded bar- Barrier and One Arc Chute Removed. RECEIVING, HANDLING, STORING All type DH breakers are completely assem- damaged, file a claim immediately with the carrier bled and given operating tests at the factory, and notify the nearest Westinghouse Sales office. after which they are carefully inspected and pre- pared for shipment by workmen experienced in HANDLING the proper handling and packing of electrical equipment. In order to afford maximum protection Remove the crating and packing carefully to against damage, the main barrier assembly and the avoid damage from negligent handling of crowbars arc chutes are removed from the breaker and or other tools. Use a nail puller for the uncrating. packed separately. For each three-pole breaker Care must be used in handling the arc chutes, there is one barrier assembly and three arc chutes. since the splitter plates within them are made After the equipment has been unpacked, make of a ceramic material which may break if dropped. a careful inspection for any damage which may have The base of the crate may be used as a skid for occurred in transit. If the apparatus has been moving the breaker, or the breaker may be lifted 3 RECEIVING, HANDLING AND STORING. with sling under the crate. If the breaker is to be STORING is crated. lifted with slings, move it while it still The arcing chambers are shipped in separate best way to After the breaker is unpacked, the containers to guard against damage from rough move it is by rolling it on its own wheels. handling and for better protection from dust and i If it is necessary to lift the breaker after it is water or liquids. Store them in their shipping or barriers uncrated, lift it without the arc chutes containers until ready for use. in place. Slings may be placed under the breaker in a clean frame or in holes provided in the frame. Use a Store all components of these breakers prevent the cables from distorting the dry place. During the storage period, keep them spreader to . blowout magnets. sufficiently warm to prevent moisture condensation

TABLE OF WEIGHTS (POUNDS)

ARC CHUTE BARRIER ASSEMBLY TYPE BREAKER UNIT (Each)

75-DH-150 1175 57 150 75 DH 250 1400 65 160 - - 160 75-DH-500 1600 105 150 DIM 50 1175 57 150 - 160 150 DH 250 1250 70 - - 160 150-DH-500 1450 105

INSTALLATION the With the exception of the arcing chambers and or excessive friction. As the contacts touch near necessary to close barriers, these breakers are shipped completely end of the closing stroke, the force assembled and adjusted. No adjustments should be the breaker increases rapidly. required and none should be made unless obviously 2. With the breaker in the closed position, check needed. the contacts to make certain that the adjustments When the breaker has been removed from the have not been disturbed. Refer to Fig. 2 for proper crate, remove the wooden clamp and angle iron settings. If adjustments are required, they may be braces which support the blowout magnet pole made as described under OPERATION AND AD- pieces during shipment and the breaker is ready JUSTMENTS. for final assembly. A light film of grease is applied to both the arcing Caution: Severe injury may be sustained and main contacts before the breaker is operated if any part of the body is struck by the con- at the factory. This film is normally removed before , tact arms since they move very rapidly on the shipment. Before the breaker is placed in service opening stroke. Personnel working about the inspect the arcing contacts to see that they are free breaker should stay clear of the space in which of oil or grease. the contact arms move while breaker is 3. The breaker is more easily handled with the closed or is being closed. arc chutes and barriers removed; mount these parts The following sequence of operations should be after the breaker has been moved near the metal- performed in preparing the breaker for use: clad cell structure. , play a of 1 Breakers are usually shipped with the con- Before installing the arc chutes stream . each end to tacts closed and with a tie on the trip lever to pre- dry compressed air through them from matter. Then examine vent tripping. After the breaker is unpacked and remove any dust or foreign and slots the shipping ties and braces removed, take off the the chutes to make certain that the vents foreign material Assemble tie on the trip lever and trip the breaker. Then close are open and free from . by removing the re the breaker carefully by hand, using the emergency the arc chutes on the breaker - magnet pole hand closing lever. Make certain that all parts are taining straps from the front of the position, making functioning properly and that there is no binding pieces and sliding the chutes into o 4 INSTALLATION. I.B. 32-150-3 AIR CIRCUIT BREAKER the top of the laminated pole faces. Connect the STATIONARY MOVING |II TQ |11 shunt strap to the front arcing horn in the chute. ARCING CONTACT 16 ' 16 ARCING CONTACT ARCING ^ MOVING Tighten the lower connection of the shunt strap CONTACT SPRINGS ^CONTACT ARM / STATIONARY since it may have loosened during transit. The arc ARCING SECONDARY CONTACT ^jCONTACT SHUNT V chute is now completely installed. - MOVING Make a final SECONDARY CONTACT check by operating the breaker slowly by hand to — PUFFER )K CYLINDER see that there is no interference in the movement of the moving contact. SECONDARY . CONTACT SPRINGS' 4. Set the two sections of the barrier assembly UPPER STATIONARY into position and bolt them in place They are held MAIN CONTACT —* . MOVING MAIN by two bolts in the breaker frame at the bottom of CONTACT BRIDGE — LOWER STATIONARY the barriers. The front sheets are held together at MAIN CONTACT the top by a single bolt. o 5. Thoroughly test the control wiring for possible grounds and short circuits which may have devel- LL oped during the installation period. CONDENSER7 INSULATING BUSHING OPERATING ROD The breaker is now ready to be placed in the metal-clad cell and operated electrically. Caution: When this FIG. 2. Contact Assembly. drawout equipment is put into the cell and moved in beyond the test position, the high voltage parts of the breaker will be energized. If the barrier is completely sure that the rear arcing horn connectors engage assembled on the breaker, personnel will be the contacts on the blowout coils. protected from contact with the live parts. If , After a chute has been placed in position, make however, the barrier assembly is left off and sure (1) that it is centrally located so that there is the breaker rolled into the cell, live parts are no interference with the travel of the moving con- exposed. The breaker should never be rolled tacts and (2) that it is securely held in position by into an energized cell structure without the retaining strap with top of the chute parallel to having the complete barrier assembly in place. OPERATION AND ADJUSTMENT Before adjusting a circuit breaker, it is advan- circuit contacts in the cell. Above the arcing con- tageous to become familiar with the construction tacts are located the blowout magnets and arc and function of the various parts. The following chutes. The breaker is tripped by lifting the trip- paragraphs describe the operation and the various ping trigger either manually, or electrically by adjustments which can be made. This material means of the trip coil. should be studied carefully before doing any work on the breaker. OPERATING MECHANISM The general arrangement of the breaker com - The solenoid operating mechanism with its trip ponents is shown in Fig. 1. The solenoid coil is - * free linkage is shown in Fig. 3. In this mechanism built to exert a horizontal force on the mechanically- the horizontal pull of the solenoid coil is transmitted trip free linkage. This linkage, in turn, exerts - to the contact operating rods through a system of an upward force on the pole unit insulating oper - links which rotates counter-clockwise about the ating rods. The moving contact arms carry the operating center. The linkage system consists of main contact bridges, secondary contacts, and arc - four major links: the non trip free lever, trip free ing contacts. On opening, these contacts separate - lever, upper trip free link, and lower trip free link. in the order named; on closing, they touch in the These members are arranged as shown and are reverse order. held to form a rigid member by the cam link and * On the outer ends of the condenser bushings are tripping cam. The tripping cam is held fixed by "C ' clusters of finger contacts for engaging the main the tripping latch. 5 OPERATION AND ADJUSTMENT

I I

FIG. 3. Solenoid Operating Mechanism. When the solenoid is energized, it pulls on the release the tripping cam so that it is free to rotate. i junction of the non-trip free lever and the lower trip Without the restraining force of the cam and cam free link, causing the system to rotate about the link, the major linkage collapses under the force of operating center The trip free lever . then exerts the contact springs and the accelerating springs an upward force on the operating rods through the which are located in an air bumper attached to the cross bar to close the breaker. The breaker is held in this position by the closing latch and the tripping trip free lever. The junction of the upper and lower latch. trip free links moves to the right and the trip free The breaker is tripped either electrically or manu- lever rotates clockwise, thus opening the breaker. ally by lifting the trigger which disengages the The position of the linkage is then that shown in primary latch. This allows the tripping latch to Figure 3B. 6 I B 32-150-3 OPERATION AND ADJUSTMENT, . . AIR CIRCUIT BREAKER

In moving to this position the roller on the lower MECHANISM ADJUSTMENTS trip free link has disengaged the closing latch. The retrieving springs now move the solenoid core The mechanism in the type DH air circuit breaker which moves the linkage to the reset position as is adjusted at the factory and is designed to give long performance any shown in Figure 3C. In this position the tripping trouble-free . Do not make adjustment faulty latch is reset and the breaker may be reclosed. unless operation is observed.

MECHANISM PANEL Latch-Checking Switch. If the breaker is designed for automatic reclosing duty, there are The mechanism panel is mounted on the front two switches mounted on the front panel. The lower of the closing solenoid mechanism as shown in Fig. switch is the cut-off switch and the upper switch is 4. On it are mounted the following auxiliary de- the latch-checking switch. The latter prevents vices included as standard on all breakers: energizing the solenoid to reclose the breaker until Shunt Trip Magnet. This device may be the tripping latch has reset. This switch is adjusted equipped with a coil for direct current or alternat- with the breaker in the open position. Turn the adjusting make then i ing current or capacitor tripping. screw until the contacts and advanced two more turns. This switch should open i Cut-Off Switch. This switch causes the supply early in the closing stroke and close when the to the closing solenoid to be cut off after the breaker breaker is opened. is closed. Cut-Off Switch. If the circuit breaker cannot Position Indicator. This device gives positive be closed electrically because *a fuse or breaker indication of the position of the breaker contacts. has opened the supply to the closing solenoid, check Operation Counter. This counter records each the cut-off switch. This switch interrupts the supply operation of the breaker. to the solenoid when the breaker has closed. The adjustment of the switch is made by means The following special devices may also be of a screw in the end of the cut-off switch operating mounted on the mechanism panel when required: arm which extends through the mechanism panel Undervoltage Trip Attachment. This de- as shown on Fig. 5. This screw may be adjusted by vice may be equipped with either an a-c or d-c loosening the two lock nuts which lock it to the arm. coil to trip the breaker on undervoltage. Special With the breaker in the closed position, adjust a-c and d-c coils are also available for use with time the screw until the switch makes contact and then delay undervoltage tripping devices mounted in the turn the screw down two more turns. This gives metal-clad cell. Latch-Checking Switch. This switch is sup- plied when the breaker is used for automatic reclosing service. It prevents completion of the closing circuit until the closing mechanism has reset after being tripped. r OPERATION : SECONDARY COUNTER CONTACT f .OCKING PIN

- i \ _ POSITION 1 L INDICATOR ’ -. m Rf #1 CUT-OFF SWITCH

' SHUNT TRIP MAGNET

: FIG. 4. Mechanism Panel. FIG. 5. Cutoff Switch Adjustment. 7 OPERATION AND ADJUSTMENT. o

FIG. 6. Tripping Latch Adjustment. the switch the correct amount of overtravel. After it is adjusted, tighten the two lock nuts. Check the operation by closing the breaker slowly by hand. FIG. 7 Primary Latch and Trip Cora Adjustment. The cut off switch should make contact near the end of the closing stroke and should open when Primary Latch. The primary latch may be the breaker is opened. readily observed from the front of the breaker. This should be adjusted with the lower latching to close Tripping Latch. If the breaker fails surface (on the trigger) extending slightly outward on energizing of the closing coil, the cause may be from the surface on the tripping latch lever. See the faulty operation of the tripping latch. Examine Fig. 7. the tripping trigger. If this latch primary latch on To adjust this latch, place the breaker in the does not reset when the breaker is in the open J open position and hold the tripping latch lever down then the difficulty may be due to improper position, against the trigger. Adjust the trigger stop until the tripping latch and the trip- clearance between the front edges of the latching surfaces coincide may be measured by removing the ping cam. This and then turn the screw down a half turn so that panel forms the seat of the chair- horizontal which the lower surface extends slightly outward. shaped breaker frame and is slotted to clear the If this latch is not properly adjusted, the breaker contact operating rods. The minimum clearance may trip from the impact of a normal closing opera- between the roller and the cam with the breaker tion. Note that this adjustment may require adjust- open is one-thirty-second of an inch. ment of the trip core as described below. If this minimum clearance cannot be measured, it can be obtained by adjusting the stop on the non- Trip Coil Core. Another possible cause of a trip free lever. This stop is accessible after removing breaker tripping during a normal closing operation the front panel on which the trip coil is mounted as is improper adjustment of the trip core. At the bot- shown in Fig. 6. tom of the trip coil is a stop for the trip core. There In order to remove this panel, first remove the should be a one thirty-second to one-sixteenth inch nut which holds the trip core to the trigger and gap between the core and the stop with the trigger may be adjusted by then the spring from the operating arm of the opera- down against its stop. This under the long hex nut im- tion counter. The panel bolts may then be loosened loosening the lock nut trip rod and the panel removed. The panel should be moved mediately below the trigger. The brass long hex nut as if on hinges at the left-hand edge to prevent may then be screwed in or out of the damage to the wires connecting to the cut-off switch to vary the gap. and trip coil. There is no need to remove the wires. BREAKER CONTACT ASSEMBLY When the panel has been removed, loosen the lock- assembly for one pole is ing nut and adjust the stop bolt until the clearance The breaker contact between the roller and the cam is between one- and shown in Fig. 2. In this assembly the stationary bushings three-thirty-seconds inches. contacts are mounted on the condenser 0 8 OPERATION AND ADJUSTMENT, I.B. 32-150-3 AIR CIRCUIT BREAKER and the moving contacts are mounted on the mov- When the arcing contacts have been properly ing contact arm. There are three sets of contacts adjusted, they should touch on all three poles at in the assembly called the main, secondary, and approximately the same time in the closing stroke. arcing contacts. It is satisfactory, if, when the first pole touches, the greatest distance between arcing The main contacts are of a silver nickel alloy contacts on other - . poles is not greater than A bridge on the moving contact arm connects the one-fourth inch. two stationary main contacts giving a high-pressure line contact. ARC CHUTES AND BLOWOUT MAGNETS The secondary and arcing contacts are of a silver The arc chute on the type DH air circuit breaker tungsten material with a high resistance to arc consists of an assembly of insulating refractory plates burning. The stationary members are brazed to a enclosed in a rectangular Micarta tube or jacket. single casting mounted on springs which are com- In position on the breaker, the jacket is between the pressed when the breaker is closed. The travel of poles of the blowout magnet and the lower end is this casting is restricted by stops which permit the immediately above the arcing contacts. top to travel more than the bottom so that, on open- The refractory plates have inverted V-shaped ing, the last point of contact is on the arcing contacts. slots starting immediately over the arcing contacts In addition to the contacts, the moving contact so that the arc is drawn into these slots. The slots arm also carries the puffer which supplies a puff of in the plates are alternately off center on opposite air through the nozzle under the moving arcing sides to increase the length of the arc path as the contact each time the breaker operates. This air arc progresses up the chute. serves to speed circuit interruption at low currents Inside the front and rear surfaces of the chute where the effect of the magnetic blow-out coils is are metallic arcing horns to which the arc transfers lessened. It has no appreciable effect in opening from the arcing contacts. The front horn is con- high currents. nected electrically to the moving contact, the rear horn through the blowout coil to the stationary CONTACT ADJUSTMENTS contact. Thus when the arc transfers to the horns, the blowout coil is included in the circuit. D Main Contacts. The main contact bridges are The action of the breaker interrupting an arc held in place on the moving contact arm by studs in is shown in Fig. 8. When the arcing contacts which pass through the main contact springs. Ad - separate, an arc is drawn between them without justment of the main contacts is made, with the the blowout coil carrying current as indicated by breaker in the latched closed position, by setting position 1 The arc rises rapidly this position the stop nuts on these studs so that there will be . from under the influence of magnetic and thermal one sixteenth inch clearance between the face of forces - air currents. These cause the arc to impinge on the nut and the back of the moving contact arm. the arcing horns, thus including the blowout coil If no clearance is present at these points, main in series with the arc. contact pressure may be lacking or absent, thus When current starts blowout coil forcing load current through the intermediate and to flow in the , the arc is driven very rapidly into the slots in the arcing contacts. This can result in overheating and refractory plates by the magnetic field. Successive damage to the contacts. If new contacts are being positions of the arc are shown in Fig. 8. installed or if the contacts have been smoothed, it is well to operate the breaker electrically several Because the slots are staggered, the arc is times so that the surfaces assume their permanent lengthened as it progresses up the chute by being shape before this adjustment is made. extended laterally from one slot to the next. This exposes a large part of the arc to the relatively cool Arcing Contacts To assure the proper . com- surfaces of the plates and to the de-ionizing effect pression in the arcing contact springs, these con- of the blowout magnet field, which results in fast tacts be adjusted should so that, with the breaker and positive interruption of the circuit. closed, the dimension from the contact surface to the front surface of the stud block is between lu( / $ HORIZONTAL DRAWOUT ARRANGEMENT and 1% inches. This adjustment is made by turn- ing the nuts which attach the insulating operating All type DH air circuit breakers are arranged 3 rod to the cross bar. for use in metal-clad equipment from which they 9 OPERATION AND ADJUSTMENT

FIG, 8. Arc Chute and Blowout Coil. may be drawn out horizontally. As may be seen the lower left-hand side of the breaker frame. This in Fig. 9, all parts are supported on a steel frame permits the plug-in connector to be extended 12 with four wheels with roller bearings to facilitate inches to the rear of its normal position so that the moving the breaker, and flanges which engage with control circuits may be connected and the breaker rails to align the breaker in the cell. operated electrically while the main contacts are disengaged. The main conductors project horizontally from the rear of the breaker, and are supported and insu- This test position occurs at the outer limit of lated from the steel back plate of the frame by breaker travel obtained by operation of the levering Micarta condenser bushings. On the ends of these - in device crank. If it is desired to connect the con main conductors are circular clusters of contact - trol circuits when the breaker has been cranked to fingers arranged to engage the circular bar con - this position, pull out the secondary contact locking ductors in the cell. pin shown in Fig. 4. While holding this pin out, The control circuit wiring also is arranged for push the secondary contact bracket toward the rear drawout disconnection by means of an 18-point of the breaker until the secondary contacts engage. connector block arranged to plug into a mating The main barriers may be removed and the breaker block mounted on the cell. This secondary con- operated safely in this position since the main nector block is mounted on a movable bracket on contacts are disconnected. 10 OPERATION AND ADJUSTMENT, I.B. 32-150-3 AIR CIRCUIT BREAKER When the breaker is in the cell far enough to be connected to the high voltage bus, the frame work of the breaker is effectively grounded by a special connector located immediately above the secondary plug-in connector block. This connector jaw engages a copper bar which is mounted in the cell and connected to the cell ground bus.

In order to move the breaker in or out of the cell against the resistance of the contact fingers, a levering-in device is provided on each breaker. There is a lever on each side mounted on a common * shaft across the back of the breaker. On each lever is a roller which engages a groove on the side wall of the cell. A removable crank engages another shaft at the right front corner of the breaker which turns the levers through a worm gear arrangement.

To move the breaker from the "test" position to final contact engagement it is necessary only to place the crank on the shaft, push until its slot engages the shaft driving pin, and turn until the breaker is in position. For safety, a mechanical interlock prevents closing the breaker while the crank is in position and also prevents cranking the breaker while the breaker is closed. FIG. 9. Rear View of 150 DH 250 Circuit Breaker. MAINTENANCE

Westinghouse power air breakers are durable rough guide for those with no previous experience pieces of equipment and have a long life under with Westinghouse power air circuit breakers. normal conditions of operation. However, condi - Note highly repetitive duty inspections tions vary widely and signs of wear may appear that for should operations much more rapidly in some cases than others. In be made at either 2500 or 5000 as indicated by the operation counter. If the breaker central station service, barring abnormal condi- is required to switch only normal currents and tions, years of service may be expected before any load extensive parts replacement is required. moderate overloads, the 5000 figure may be used. If the breaker is relayed to trip on system faults in In highly repetitive service such as motor start- addition to being used for load switching, the 2500 ing or arc furnace switching, maintenance will be figure should be used. If faults occur often, more determined by the number of operations, amount frequent maintenance may be required. of dirt, grit or other harmful substances which Arc Chutes insulating parts the settles on breaker parts, and the care with which . The of arc chute remain in the across the the breaker is kept clean and in proper adjustment. circuit contacts at all times. During the time that the contacts are open, Experience on a given installation will prove to these insulating parts are subjected to the full po- be the best guide for maintenance and parts re- tential across the breaker. Ability to withstand this placement. The table on page 12 will serve as a potential depends upon thecare given the insulation.

ii MAINTENANCE, will not appre general inspections blow out the arc chute pitting on the main contact surfaces - On ability because with dry compressed air by directing the stream ciably impair their current-carrying used Any excessive upward from the contact area and out through of the high contact pressure . with a fine file or sand each of the slots between the arc splitter plates. roughness may be removed - not recommended for this Also direct the dry air stream thoroughly over the paper. Emery cloth is not to remove excessive amounts arc box shields. These are the ceramic liners in purpose. Be careful this unnecessarily shortens the lower end of the chute where the arc is drawn. of contact material since the life of the contacts. The arc chutes may be removed periodically for slowly by hand to deter a thorough inspection. Remove any residue of dirt Operate the breaker - contact surfaces operate in the or arc products with a cloth or by a light sanding. mine whether the opening the proper sequence Do not use a wire brush or emery cloth for this proper sequence. On part, (2) secondary contacts purpose because of the possibility of embedding is: (1) main contacts part When the contacts conducting particles in the ceramic material. part, (3) arcing contacts . become worn to the point of changing this sequence, arc Note: The ceramic material in the replace them. chutes may have a dirty appearance from re- high peated arc interruption and still have a Mechanism. Apply a light lubricating oil to If apply an a c dielectric strength. in doubt, - the various wearing surfaces throughout the breaker for one test voltage of 25 kv not more than with the following exceptions. Do not oil the sur- of breakage minute. When there is evidence faces listed below. Keep them free of dirt and grit: or appreciable erosion of the slots in the contact surfaces, including main ceramic plates, the chutes should be replaced. 1. All electrical bridges, arcing contacts, contact blade of rear arc , inspect it After an arc chute has been replaced horn, and auxiliary switch contacts. to make certain that the contact of the rear arcing 2 Trigger surfaces in operating mechanism. horn has engaged the connector on the blowout . coil, that the upper edge of the jacket is substan- Wipe off the excess oil on the operating rods, that tially parallel to the magnetic pole faces, and main condenser bushings, and other insulating sur- the front arcing horn is securely connected to the faces. j lower bushing by means of the shunt strap. . A list of renewal parts recom- Contacts. Inspect the contacts periodically for Renewal Parts to be kept in stock will be furnished upon evidence of excessive burning. Under normal con- mended When ordering renewal parts, specify the ditions the contacts should be usable for a large request. of the part, and include all of the information number of operations within the rated interrupting name given on the breaker nameplate. capacity of the breaker. A moderate amount of

MAINTENANCE GUIDE FREQUENCY OF OPERATION OUTY

OPERATION Moderate Heavy Very Heavy Light Oper per day 5 Oper. per day 15 Oper. par day 30 Oper.per day 60 . 2 mos. 2500-5000 Oper. Clean external surfaces 3 mos. 3 mos. Blow out arc chutes and 2 mos. 2500 5000 Oper. inspect contacts 6 moB. 3 mos. - 4 mos. 2500 5000 Oper. Inspect mechanism 12 mos. 6 mos. -