SECTION 27 - PAD-MOUNTED TRANSFORMERS TABLE OF CONTENTS

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2 CABLE AND CONDUIT ENTRANCE SINGLE-PHASE PAD-MOUNTED TRANSFORMER INSTALLATION 100 KVA AND LARGER (CONCRETE PADS ONLY) CABLE AND CONDUIT ENTRANCE SINGLE-PHASE PAD-MOUNTED TRANSFORMER INSTALLATION KVA (CONCRETE PADS ONLY) CABLE TRAINING - PADS-VAULTS SINGLE-PHASE PAD-MOUNTED TRANSFORMERS Z-BAR SECONDARY TERMINALS FOR SINGLE-PHASE LOW PROFILE PAD-MOUNTED TRANSFORMERS COMPOSITE HOOD SINGLE-PHASE TRANSFORMER INSTALLATION FEED THROUGH BUSHING INSERT IN LOW PROFILE PAD-MOUNTED TRANSFORMERS OPEN WYE-OPEN DELTA TRANSFORMER BANK USING SINGLE-PHASE 13.2KV, 14.4KV AND 19.9KV PAD-MOUNTED TRANSFORMERS OPEN WYE-OPEN DELTA TRANSFORMER BANK USING SINGLE-PHASE 7.2KV PAD-MOUNTED TRANSFORMERS OPEN WYE-OPEN DELTA TRANSFORMER BANK 480 VOLT, 3-WIRE SERVICE USING SINGLE-PHASE 7.2KV AND 13.2KV PAD-MOUNTED TRANSFORMERS A THREE-PHASE OPEN WYE-OPEN DELTA CONNECTION 7200/12470 X 13200/22860 TO 240/480V PAD-MOUNTED TRANSFORMER 480 VOLT THREE-PHASE THREE WIRE SERVICE B STANDARD THREE-PHASE PAD-MOUNTED TRANSFORMERS THREE-PHASE PAD-MOUNTED TRANSFORMER (CONT.) GENERAL INFORMATION LOCATION OF OIL-FILLED PAD-MOUNTED TRANSFORMERS PROTECTIVE POLES FOR OIL FILLED PAD-MOUNTED TRANSFORMERS THREE-PHASE PAD-MOUNTED TRANSFORMER WITH CUSTOMER'S SECONDARY CABLE TERMINATION BOX INSTALLATION RECOMMENDED NUMBER OF CUSTOMER CONDUCTORS IN SECONDARY COMPARTMENT OF THREE-PHASE PAD-MOUNTED TRANSFORMERS TRANSFORMER SECONDARY SPADE BLOCK TERMINALS THREE-PHASE, THREE-WIRE 480 VOLT SERVICE THREE WIRE SERVICES, FLOATING WYE CONNECTION FOUR WIRE SERVICES, GROUNDED WYE CONNECTION THREE-PHASE PAD-MOUNTED TRANSFORMERS PRIMARY AND SECONDARY WINDING - NEUTRAL CONNECTIONS VARIATIONS FOR 3-WIRE SERVICES THREE-PHASE PAD-MOUNTED TRANSFORMERS PRIMARY AND SECONDARY WINDING - NEUTRAL CONNECTIONS LABELS FOR 3 WIRE SERVICES MINIPAD THREE-PHASE TRANSFORMER (FMO) O 7/15/11 CECCONI BURLISON ELKINS 11/16/10 CECCONI GUINN ELKINS REVISED BY CK'D APPR. SECTION 27 - PAD-MOUNTED TRANSFORMERS TABLE OF CONTENTS DWG B

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19 THREE-PHASE LOOP-FEED PAD-MOUNTED TRANSFORMERS GENERAL DESIGN: LOOP FEED TRANSFORMERS HAVE A DEAD-FRONT PRIMARY COMPARTMENT WITH SIX BUSHING WELLS. IN ADDITION, NEW TRANSFORMERS WITH DELTA-WYE RECONNECTABLE PRIMARY AND THOSE RATED 1000KVA AND ABOVE HAVE A 200 AMP OPEN-CLOSE OIL SWITCH LOCATED IN THE HIGH VOLTAGE COMPARTMENT. FUSING: TRANSFORMERS ARE PROTECTED ON THE PRIMARY SIDE WITH BAY-O-NET FUSING AND INTERNAL WEAK LINKS. BAY-O-NET FUSES IN LOOP FEED DELTA-WYE TRANSFORMERS WILL BE SIZED FOR THE DELTA CONNECTION (12KV) WHEN SHIPPED FROM THE GENERAL WAREHOUSE. FUTURE CONNECTIONS TO GROUNDED WYE (23KV) WILL REQUIRE FUSE REPLACEMENT. PRIMARY VOLTAGES: STANDARD PRIMARY VOLTAGES ARE 12,470Y/7200 VOLTS (IN SIZES UP TO 2500KVA) 22,860Y/13,200 VOLTS (IN SIZES UP TO 3750 KVA) AND14,400 DELTA/24,940Y/14,400 (DELTA-WYE PRIMARY IN SIZES UP TO 2500 KVA). 34,500GRDY/19,920 VOLT TRANSFORMERS ARE AVAILABLE BY SPECIAL ORDER FOR EASTERN REGION ONLY. DELTA-WYE TRANSFORMERS: DELTA-WYE TRANSFORMERS SHOULD ONLY BE USED WHERE A CONVERSION IS PLANNED WITHIN THE NEXT THREE YEARS OR WHERE THERE IS NO SINGLE RATED PRIMARY AVAILABLE IN THE REQUIRED SIZE. SINGLE RATED PRIMARY TRANSFORMERS SHOULD BE USED OTHERWISE. DELTA-WYE TRANSFORMERS CAN BE USED AT 12 OR 23 KV AND WILL BE SHIPPED FROM THE GENERAL WAREHOUSE IN THE DELTA CONNECTION (12KV). FUTURE CONNECTION TO GROUNDED WYE (23KV) MUST BE DONE IN THE FIELD BY CHANGING CONNECTIONS ON THE DELTA-WYE SWITCH (OR TERMINAL BOARD ACCESSIBLE BY WAY OF HANDHOLE), ACCORDING TO THE INSTRUCTIONS SHOWN ON THE TRANSFORMER NAMEPLATE. ADDITIONALLY, BAY-O-NET FUSES SHOULD BE CHANGED TO SIZE SPECIFIED FOR 23KV. DELTA-CONNECTED TRANSFORMERS SHOULD BE ENERGIZED (OR DE-ENERGIZED) USING THE THREE-PHASE (OPEN-CLOSE) OIL SWITCH LOCATED INSIDE THE HIGH VOLTAGE COMPARTMENT (OR OTHER THREE-PHASE SWITCHING) TO PREVENT FERRORESONANT OVERVOLTAGES. THIS SWITCH IS RATED FOR 200 AMP LOADBREAKS. VOLTAGE TAP SETTINGS: TWO TAPS, ABOVE AND BELOW AT 2.5% ARE AVAILABLE ON ALL NEW 12,470GRDY/7200, 22,860GRDY/13,200 AND 34,500GRDY/19,920 TRANSFORMERS AND ON DELTA-WYE UNITS. DELTA TAP SETTINGS ARE 14,400,13,500, 13,200, 12,470 AND 12,210 VOLTS. WYE TAP SETTINGS ARE 24,940, 23,380, 22,860, 21,600 AND 21,150 VOLTS. KVA RATINGS: STANDARD KVA RATINGS ARE 75, 150, 300, 500, 750, 1000, 1500, 2500 AND 3750 KVA. THERE ARE OLDER 112 AND 225 KVA UNITS IN SERVICE THAT ARE NO LONGER PURCHASED. SECONDARY VOLTAGES: STANDARD 208Y/120 VOLT SECONDARY VOLTAGES ARE AVAILABLE IN SIZES UP TO 750 KVA (A 1000 KVA UNIT IS AVAILABLE FOR OVERLOADS) FOR USE ON 12,470GRDY/7200 OR 22,860GRDY/13,200 VOLT SYSTEMS. THE 208Y/120 VOLT SECONDARY IS AVAILABLE IN 75 AND 150KVA SIZES FOR USE ON A 34,500GRDY/19,920 VOLT SYSTEM. 480Y/277 VOLT SECONDARY IS AVAILABLE IN SIZES UP TO A 3750KVA FOR 22,860GRDY/13,200 VOLT SYSTEMS, 2500 KVA FOR 12470GRDY/7200 VOLT SYSTEMS AND 500KVA FOR 34,500GRDY/19,920 VOLT SYSTEMS. 4160Y/2400 VOLT SECONDARY IS AVAILABLE IN 2500KVA FOR USE ON EITHER A 12470GRDY/7200 OR 22,860GRDY/13,200 VOLT SYSTEM. PRIMARY TRANSFORMER RATING (KV) KVA HV BAY-O-NET FUSE LINK AMPERE RATING SHORTING BAR (SEE NOTES 3,4) (SEE NOTE 4) 125 (SEE NOTE 6) 5 12 CATALOG NUMBER MINIMUM DIP POLE FUSE AMPERE RATING 20K 30K 50K 65K 100K 65KS 65KS 100KS 20K 20K 40K 50K 50KS 50KS 65KS 125E (SEE NOTE 5) 125E 25K 25K NOTES: 1. DIP POLE FUSES MUST BE EQUAL TO OR LARGER THAN BAY-O-NET FUSE SIZES SHOWN ABOVE. 2. DIP POLE FUSING RECOMMENDATIONS BASED ON SINGLE TRANSFORMER OF INDICATED SIZE. FOR MULTIPLE UNITS ON RADIAL FEED, CONSULT WITH REGION RELIABILITY AND PROTECTION ENGINEER FOR DIP POLE FUSING. 3. THE SHORTING BAR IS NOTHING MORE THAN A SOLID COPPER LINK WITH AN ISOLATION LINK CONNECTED IN SERIES. THE DIP POLE OR PAD-MOUNTED SWITCHGEAR FUSES ARE PROTECTING THE TRANSFORMER. IT IS RECOMMENDED THAT MANUAL FAULT INDICATORS BE USED ON THE TRANSFORMER PRIMARY SOURCE-SIDE CABLES WITH THESE UNITS TO ASSIST WITH IDENTIFYING ANY FUTURE BLOWN FUSES. 4. UNITS THAT CURRENTLY USE A 140 AMPERE RATED BAY-O-NET FUSE SHOULD BE REFUSED WITH THE SAME ( CN ). 5. AS AN ALTERNATIVE, A 100E DIP POLE FUSE CAN BE USED IN THIS APPLICATION UPON APPROVAL FROM THE REGIONAL COORDINATION ENGINEER. 6. THE 125 AMP BAY-O-NET FUSE WILL NOT COORDINATE WITH THE 125E DIP POLE FUSE. THESE TRANSFORMERS SHOULD HAVE MANUAL FAULT INDICATORS PLACED ON THE TRANSFORMER PRIMARY SOURCE-SIDE CABLES TO ASSIST WITH IDENTIFYING ANY FUTURE TRANSFORMER FAILURES. 7. WHEN ONE FUSE BLOWS ON A DIP POLE THAT SERVES A THREE-PHASE TRANSFORMER OR BANK OF TRANSFORMERS, ALL FUSES SHALL BE REPLACED. THIS IS NECESSARY BECAUSE THE FAULT AND SINGLE-PHASING CAN CHANGE THE CHARACTERISTICS OF THE FUSES THAT DID NOT BLOW /9/11 SIMMONS BURLISON ELKINS 6/29/10 SIMMONS GUINN ELKINS REVISED BY CK'D APPR. STANDARD THREE-PHASE PAD-MOUNTED TRANSFORMERS AND BAY-O-NET FUSE TABLE DWG

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40 CONNECTING PARALLEL SECONDARIES ANY TIME PARALLEL THREE-PHASE SECONDARY CONDUCTORS ARE RUN TO THE CUSTOMER OR THE CUSTOMER COMES TO THE SECONDARY TERMINALS OF THE TRANSFORMER, EACH PARALLEL CONDUCTOR SHOULD BE THE SAME LENGTH. HOWEVER, EXCESSIVE CONDUCTOR LENGTH SHOULD BE CUT SO THE CONDUCTORS MAKE A NEAT, SAFE FIT TO THE SECONDARY TERMINALS. WHEN CUTTING OFF EXCESS CONDUCTORS, DIFFERENT LENGTHS CAN BE TRIMMED FROM THE THREE-PHASE CONDUCTORS OR THE NEUTRAL, AS LONG AS ALL CONDUCTORS ON THE SAME PHASE ARE THE SAME LENGTH. CABLES SHOULD BE BENT AT THE BOTTOM OF THE SECONDARY COMPARTMENT AND TRAINED TO COME UP STRAIGHT UNDER THE SECONDARY BUSHING WHERE THEY ARE TO BE CONNECTED. THERE SHOULD BE ENOUGH SLACK IN THE CABLES TO ALLOW FOR TRENCH SETTLEMENT. CUT THE CABLES TO PROPERLY FIT AT THE SECONDARY BUSHINGS. ATTACH THE CABLES TO THE SET SCREW BLOCKS STARTING AT THE BACK OF THE SECONDARY BUSHING. ALL CONDUCTORS OF THE SAME PHASE OR NEUTRAL MUST BE THE SAME LENGTH SINGLE PHASING PAD-MOUNTED TRANSFORMERS SHOULD NOT BE LEFT TO SINGLE PHASE FOR LONG PERIODS OF TIME. SINGLE PHASING IS AN OUTAGE CONDITION AND SHOULD BE TREATED AS SUCH. PAD-MOUNTED TRANSFORMERS SUBJECTED TO EXTENDED PERIODS OF SINGLE PHASING WILL OVERHEAT DUE TO CIRCULATING MAGNETIC CURRENTS. FAULT INDICATORS THREE-PHASE TRANSFORMERS - MANUAL FAULT INDICATORS SHALL BE INSTALLED ON THE LOAD SIDE PRIMARY CABLES WHEN THE TRANSFORMER IS WITHIN A LOOP SYSTEM OR ON A RADIAL SYSTEM CONTAINING MORE THAN ONE TRANSFORMER. FAULT INDICATORS ARE NOT REQUIRED ON A SINGLE, RADIAL-FED, THREE-PHASE TRANSFORMER. SEE DWG FOR MORE DETAIL /15/11 SIMPSON SIMPSON ELKINS 7/15/11 DANNA BURLISON ELKINS 6/29/10 SIMMONS GUINN ELKINS REVISED BY CK'D APPR. THREE-PHASE PAD-MOUNTED TRANSFORMER (CONT.) GENERAL INFORMATION DWG

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42 BUILDING WALL TRANSFORMER PAD MAXIMUM 5'-2" TRANSFORMER MAXIMUM 5'-2" 1'-0" 1'-0" SEE NOTE 1 1'-0" MAX. 4'-10" MAX. 4'-10" PLAN VIEW NOTES: FILL 12" DIA. MIN. HOLE AND 4" DIA. CONDUIT WITH 3000 PSI CONCRETE ROUND FORM TOP AND SLOPE CONCRETE AT BASE OF POLE 4'-0" 1. ON THREE-PHASE PAD-MOUNTED TRANSFORMERS, THIS POLE SHOULD BE CENTRALLY LOCATED 2'-0" IN FRONT OF THE TRANSFORMER BETWEEN THE DOORS TO ACCOMMODATE THE DOOR SWING AND SHALL BE REMOVABLE. ON SINGLE-PHASE TRANSFORMERS, THIS POLE SHOULD BE LOCATED APPROXIMATELY 3'-6" IN FRONT OF THE TRANSFORMER (NO LESS THAN 3'). 2. TRANSFORMER PROTECTION POLES SHOULD BE INSTALLED ON ALL SIDES OF THE TRANSFORMER WHICH ARE SUBJECT TO VEHICULAR TRAFFIC. 3. POLES SHOULD BE PAINTED YELLOW. FILL 12" DIA. MIN. HOLE AND 4" DIA. CONDUIT WITH 3000 PSI CONCRETE ROUND FORM TOP AND SLOPE CONCRETE AT BASE OF POLE 4'-0" 4. THESE PROTECTIVE POLES SHALL BE PROVIDED AND INSTALLED BY THE CUSTOMER. 5. CUSTOMER MAY PROVIDE AN ALTERNATE DESIGN FOR A REMOVABLE BARRIER, BUT MUST BE APPROVED BY THE FIELD ENGINEER. 3" MIN. CONCRETE ALL AROUND 3" MIN. CONCRETE ALL AROUND 4" GALV. STEEL CONDUIT CUT TO 7'-0" LENGTH CN SEE NOTE 7 3'-0" 6. ANY SINGLE AND THREE-PHASE PAD-MOUNTED TRANSFORMERS THAT ARE EXPOSED TO PAVED AREAS AND/OR VEHICULAR TRAFFIC SHALL HAVE PROTECTIVE BARRIERS PROVIDED AND INSTALLED BY THE CUSTOMER. 7. CN (6"X6"X8' CONCRETE POST, GRAY IN COLOR) IS AVAILABLE AS A PROTECTIVE POLE. EXPOSED PART OF POLE TO BE PAINTED WITH "HIGHWAY YELLOW" (OR SIMILAR YELLOW COLOR) CONCRETE PAINT. 4" GALV. STEEL CONDUIT CUT TO 7'-0" LENGTH CN " SCH 80 PVC CONDUIT CUT TO 3'-0" LENGTH 6" COMPACTED STONE OR GRAVEL 3'-0" STANDARD POLE REMOVABLE POLE /27/12 SIMPSON SIMPSON ELKINS 4/12/10 SIMPSON SIMPSON ELKINS REVISED BY CK'D APPR. PROTECTIVE POLES FOR OIL FILLED PAD-MOUNTED TRANSFORMERS DWG

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44 PAD-MOUNTED TRANSFORMER SIZE (KVA) NUMBER OF HOLES IN SECONDARY BUSHING SPADE 480Y/277 NUMBER OF HOLES IN SECONDARY BUSHING SPADE 208Y/120 RECOMMENDED NUMBER OF CUSTOMER CONDUCTORS PER PHASE IN PAD-MOUNTED TRANSFORMERS 480Y/ Y/ N/A 16 N/A N/A 16 N/A N/A 16 N/A NOTES: 1. IF THE RECOMMENDED CONDUCTOR LIMITS ABOVE ARE EXCEEDED, THE CUSTOMER MUST CONSIDER INSTALLING A JUNCTION BOX. THE JUNCTION BOX AND ALL ASSOCIATED EQUIPMENT (BOX, BUS, CONNECTORS, RACEWAY, PAD, PAD GROUNDS AND ALL CONNECTIONS) SHOULD BE OWNED, INSTALLED AND MAINTAINED BY THE CUSTOMER AS SHOWN ON DWG SEE DWG FOR TRANSFORMER SECONDARY SPADE BLOCK TERMINALS. 3. MAXIMUM CUSTOMER CONDUCTOR SIZE IS 750 KCMIL CU/AL. 4. PARALLELED CUSTOMER CONDUCTORS MUST BE "RUNG OUT" PRIOR TO ENERGIZING TO PREVENT CROSS PHASING. 5. SIX-CONDUCTOR SECONDARY SPADE BLOCK TERMINALS REQUIRE THAT A MINIMUM OF SIX BOLT HOLES BE ATTACHED TO SECONDARY BUSHING SPADE OF TRANSFORMER. EIGHT-CONDUCTOR BLOCKS REQUIRE A MINIMUM OF EIGHT BOLT HOLES BE ATTACHED TO SECONDARY BUSHING OF TRANSFORMER /27/12 SIMPSON SIMPSON ELKINS 4/1/11 SIMPSON SIMPSON ELKINS 4/12/10 SIMPSON SIMPSON ELKINS REVISED BY CK'D APPR. RECOMMENDED NUMBER OF CUSTOMER CONDUCTORS IN SECONDARY COMPARTMENT OF THREE-PHASE PAD-MOUNTED TRANSFORMERS DWG

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