27.00-00BDWG.

SECTION 27 - PAD-MOUNTED TRANSFORMERS

TABLE OF CONTENTS11/16/10 ELKINSCECCONI GUINN

RECOMMENDED NUMBER OF CUSTOMER CONDUCTORS IN SECONDARY

THREE WIRE SERVICES, FLOATING WYE CONNECTIONTHREE-PHASE, THREE-WIRE 480 VOLT SERVICE

COMPARTMENT OF THREE-PHASE PAD-MOUNTED TRANSFORMERS

MINIPAD THREE-PHASE TRANSFORMER (FMO)

NEUTRAL CONNECTIONS LABELS FOR 3 WIRE SERVICES

THREE-PHASE PAD-MOUNTED TRANSFORMER (CONT.) GENERAL INFORMATIONSTANDARD THREE-PHASE PAD-MOUNTED TRANSFORMERS

LOCATION OF OIL-FILLED PAD-MOUNTED TRANSFORMERS

TRANSFORMER SECONDARY SPADE BLOCK TERMINALS

PROTECTIVE POLES FOR OIL FILLED PAD-MOUNTED TRANSFORMERS

TERMINATION BOX INSTALLATION

NEUTRAL CONNECTIONS VARIATIONS FOR 3-WIRE SERVICESTHREE-PHASE PAD-MOUNTED TRANSFORMERS PRIMARY AND SECONDARY WINDING -

THREE-PHASE PAD-MOUNTED TRANSFORMER WITH CUSTOMER'S SECONDARY CABLE

THREE-PHASE PAD-MOUNTED TRANSFORMERS PRIMARY AND SECONDARY WINDING -

27.06-06

27.06-28

27.06-12

27.06-14

27.06-1627.06-20

27.06-26

27.06-09

27.06-08

27.06-0227.06-0327.06-05

FOUR WIRE SERVICES, GROUNDED WYE CONNECTION 27.06-24

O

2

1

APPR.REVISED BY CK'D

3

CABLE AND CONDUIT ENTRANCE SINGLE-PHASE PAD-MOUNTED TRANSFORMER27.05-03

CABLE TRAINING - PADS-VAULTS SINGLE-PHASE PAD-MOUNTED TRANSFORMERSZ-BAR SECONDARY TERMINALS FOR SINGLE-PHASE LOW PROFILE PAD-MOUNTED

27.05-04

TRANSFORMERS 27.05-06

INSTALLATION 25-75 KVA (CONCRETE PADS ONLY)

FEED THROUGH BUSHING INSERT IN LOW PROFILE PAD-MOUNTED TRANSFORMERS

OPEN WYE-OPEN DELTA TRANSFORMER BANK USING SINGLE-PHASE 7.2KV27.05-12

27.05-10COMPOSITE HOOD SINGLE-PHASE TRANSFORMER INSTALLATION 27.05-08

PAD-MOUNTED TRANSFORMERS

OPEN WYE-OPEN DELTA TRANSFORMER BANK USING SINGLE-PHASE 13.2KV,14.4KV AND 19.9KV PAD-MOUNTED TRANSFORMERS

27.05-13OPEN WYE-OPEN DELTA TRANSFORMER BANK 480 VOLT, 3-WIRE SERVICE

USING SINGLE-PHASE 7.2KV AND 13.2KV PAD-MOUNTED TRANSFORMERS 27.05-14ATHREE-PHASE OPEN WYE-OPEN DELTA CONNECTION 7200/12470 X 13200/22860

TO 240/480V PAD-MOUNTED TRANSFORMER 480 VOLT THREE-PHASE27.05-14BTHREE WIRE SERVICE

CABLE AND CONDUIT ENTRANCE SINGLE-PHASE PAD-MOUNTED TRANSFORMER27.05-01INSTALLATION 100 KVA AND LARGER (CONCRETE PADS ONLY)

7/15/11 ELKINSCECCONI BURLISON

DWG.

27.02-08

THREE-PHASE LOOP-FEED PAD-MOUNTED TRANSFORMERS

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.

FUSES IN LOOP FEED DELTA-WYE TRANSFORMERS WILL BE SIZED FOR THE DELTA CONNECTION (12KV) WHEN SHIPPED FROM THEGENERAL WAREHOUSE. FUTURE CONNECTIONS TO GROUNDED WYE (23KV) WILL REQUIRE FUSE REPLACEMENT.

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) OILSWITCH LOCATED INSIDE THE HIGH VOLTAGE COMPARTMENT (OR OTHER THREE-PHASE SWITCHING) TO PREVENT FERRORESONANT OVERVOLTAGES. THIS SWITCH IS RATED FOR 200 AMP LOADBREAKS.

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.

225 KVA UNITS IN SERVICE THAT ARE NO LONGER PURCHASED.

FUSING: TRANSFORMERS ARE PROTECTED ON THE PRIMARY SIDE WITH BAY-O-NET FUSING AND INTERNAL WEAK LINKS. BAY-O-NET

PRIMARY VOLTAGES: STANDARD PRIMARY VOLTAGES ARE 12,470Y/7200 VOLTS (IN SIZES UP TO 2500KVA) 22,860Y/13,200 VOLTS

VOLTAGE TAP SETTINGS: TWO TAPS, ABOVE AND BELOW AT 2.5% ARE AVAILABLE ON ALL NEW 12,470GRDY/7200, 22,860GRDY/13,200

KVA RATINGS: STANDARD KVA RATINGS ARE 75, 150, 300, 500, 750, 1000, 1500, 2500 AND 3750 KVA. THERE ARE OLDER 112 AND

SECONDARY VOLTAGES: STANDARD 208Y/120 VOLT SECONDARY VOLTAGES ARE AVAILABLE IN SIZES UP TO 750 KVA (A 1000 KVA

GENERAL DESIGN: LOOP FEED TRANSFORMERS HAVE A DEAD-FRONT PRIMARY COMPARTMENT WITH SIX BUSHING WELLS. IN ADDITION,

(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.

6/29/10 SIMMONS GUINN ELKINS

STANDARD THREE-PHASEPAD-MOUNTED TRANSFORMERSAND BAY-O-NET FUSE TABLE

NOTES:

1. DIP POLE FUSES MUST BE EQUAL TO OR LARGER THAN BAY-O-NET FUSE SIZES SHOWN ABOVE.

0

APPR.REVISED BY CK'D

1

2

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 PRIMARYTRANSFORMERS SHOULD BE USED OTHERWISE.

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 SYSTEMSAND 500KVA FOR 34,500GRDY/19,920 VOLT SYSTEMS. 4160Y/2400 VOLT SECONDARY IS AVAILABLE IN 2500KVA FOR USE ON EITHERA 12470GRDY/7200 OR 22,860GRDY/13,200 VOLT SYSTEM.

2. DIP POLE FUSING RECOMMENDATIONS BASED ON SINGLE TRANSFORMER OF INDICATED SIZE. FOR MULTIPLE UNITS ON RADIALFEED, 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 POLEOR PAD-MOUNTED SWITCHGEAR FUSES ARE PROTECTING THE TRANSFORMER. IT IS RECOMMENDED THAT MANUAL FAULT INDICATORSBE USED ON THE TRANSFORMER PRIMARY SOURCE-SIDE CABLES WITH THESE UNITS TO ASSIST WITH IDENTIFYING ANY FUTURE

5. AS AN ALTERNATIVE, A 100E DIP POLE FUSE CAN BE USED IN THIS APPLICATION UPON APPROVAL FROM THE REGIONAL

7515030050075010001500

2500

751503005007501000150025003750150500

815254065100100

(SEE NOTES 3,4)

581525404065

100 (SEE NOTE 4)125 (SEE NOTE 6)

512

211245082112460721124300211436072114370621143508

9220176434

9220176433

21124102211245082112460721124300211436072114360721143706

922017643492201764362112410221124201

20K30K50K65K100K65KS65KS

100KS

20K20K40K50K

50KS50KS65KS

125E (SEE NOTE 5)125E25K25K

PRIMARYRATING (KV)

TRANSFORMERKVA

HV BAY-O-NETFUSE LINK

AMPERE RATING

CATALOGNUMBER

MINIMUM DIP POLE FUSE AMPERE RATING

12.4712.4712.4712.4712.4712.4712.47

12.47

22.8622.8622.8622.8622.8622.8622.8622.8622.8634.534.5

SHORTING BAR

BLOWN FUSES.

COORDINATION ENGINEER.

4. UNITS THAT CURRENTLY USE A 140 AMPERE RATED BAY-O-NET FUSE SHOULD BE REFUSED WITH THE SAME ( CN 21144407).

3

6. THE 125 AMP BAY-O-NET FUSE WILL NOT COORDINATE WITH THE 125E DIP POLE FUSE. THESE TRANSFORMERS SHOULD HAVEMANUAL FAULT INDICATORS PLACED ON THE TRANSFORMER PRIMARY SOURCE-SIDE CABLES TO ASSIST WITH IDENTIFYING ANYFUTURE TRANSFORMER FAILURES.

7. WHEN ONE FUSE BLOWS ON A DIP POLE THAT SERVES A THREE-PHASE TRANSFORMER OR BANK OF TRANSFORMERS, ALL FUSESSHALL BE REPLACED. THIS IS NECESSARY BECAUSE THE FAULT AND SINGLE-PHASING CAN CHANGE THE CHARACTERISTICS OF THEFUSES THAT DID NOT BLOW.

9/9/11 SIMMONS BURLISON ELKINS

REVISED BY CK'D APPR.

DWG.

1

27.06-03

2

3

0

CONNECTING PARALLEL SECONDARIES

ANY TIME PARALLEL THREE-PHASE SECONDARY CONDUCTORS ARE RUN TO THE CUSTOMER OR THE CUSTOMERCOMES TO THE SECONDARY TERMINALS OF THE TRANSFORMER, EACH PARALLEL CONDUCTOR SHOULD BE THESAME LENGTH. HOWEVER, EXCESSIVE CONDUCTOR LENGTH SHOULD BE CUT SO THE CONDUCTORS MAKE ANEAT, SAFE FIT TO THE SECONDARY TERMINALS. WHEN CUTTING OFF EXCESS CONDUCTORS, DIFFERENT LENGTHSCAN BE TRIMMED FROM THE THREE-PHASE CONDUCTORS OR THE NEUTRAL, AS LONG AS ALL CONDUCTORS ON

SINGLE PHASING

PAD-MOUNTED TRANSFORMERS SHOULD NOT BE LEFT TO SINGLE PHASE FOR LONG PERIODS OF TIME. SINGLEPHASING IS AN OUTAGE CONDITION AND SHOULD BE TREATED AS SUCH. PAD-MOUNTED TRANSFORMERSSUBJECTED TO EXTENDED PERIODS OF SINGLE PHASING WILL OVERHEAT DUE TO CIRCULATING MAGNETICCURRENTS.

THE SAME PHASE ARE THE SAME LENGTH.

CABLES SHOULD BE BENT AT THE BOTTOM OF THE SECONDARY COMPARTMENT AND TRAINED TO COME UPSTRAIGHT UNDER THE SECONDARY BUSHING WHERE THEY ARE TO BE CONNECTED. THERE SHOULD BE ENOUGHSLACK IN THE CABLES TO ALLOW FOR TRENCH SETTLEMENT. CUT THE CABLES TO PROPERLY FIT AT THESECONDARY BUSHINGS. ATTACH THE CABLES TO THE SET SCREW BLOCKS STARTING AT THE BACK OF THESECONDARY BUSHING.

6/29/10

THREE-PHASE PAD-MOUNTEDTRANSFORMER (CONT.)GENERAL INFORMATIONSIMMONS GUINN ELKINS

7/15/11 DANNA BURLISON ELKINS

FAULT INDICATORS

THREE-PHASE TRANSFORMERS - MANUAL FAULT INDICATORS SHALL BE INSTALLED ON THE LOAD SIDE PRIMARYCABLES WHEN THE TRANSFORMER IS WITHIN A LOOP SYSTEM OR ON A RADIAL SYSTEM CONTAINING MORE THANONE TRANSFORMER. FAULT INDICATORS ARE NOT REQUIRED ON A SINGLE, RADIAL-FED, THREE-PHASE

SEE DWG. 26.07-08 FOR MORE DETAIL.

8/15/11 SIMPSON SIMPSON ELKINS

ALL CONDUCTORSOF THE SAME PHASEOR NEUTRAL MUSTBE THE SAME LENGTH

TRANSFORMER.

BUILDING WALL

TRANSFORMER PAD

TRANSFORMER

1'-0"

1'-0"

4'-0"

3'-0" 4" GALV.STEEL CONDUIT CUT TO

7'-0" LENGTH

FILL 12" DIA.MIN. HOLE AND 4"

DIA. CONDUIT WITH3000 PSI CONCRETEROUND FORM TOP

AND SLOPECONCRETE AT BASE OF POLE

SEE NOTE 1

PLAN VIEW

3" MIN.CONCRETE

STANDARD POLE

DWG.

27.06-06

ALL AROUND

ALL AROUND

REMOVABLE POLE

CONCRETE3" MIN.

BASE OF POLECONCRETE AT

AND SLOPEROUND FORM TOP

3000 PSI CONCRETEDIA. CONDUIT WITH

HOLE AND 4"FILL 12" DIA. MIN.

7'-0" LENGTHSTEEL CONDUIT CUT TO

4" GALV.

3'-0"

4'-0"

NOTES:

2. TRANSFORMER PROTECTION POLES SHOULD BEINSTALLED ON ALL SIDES OF THE TRANSFORMERWHICH ARE SUBJECT TO VEHICULAR TRAFFIC.

3. POLES SHOULD BE PAINTED YELLOW.

4. THESE PROTECTIVE POLES SHALL BE PROVIDEDAND INSTALLED BY THE CUSTOMER.

5" SCH 80 PVC CONDUIT CUT TO

3'-0" LENGTH

6" COMPACTEDSTONE OR GRAVEL

5. CUSTOMER MAY PROVIDE AN ALTERNATE DESIGNFOR A REMOVABLE BARRIER, BUT MUST BEAPPROVED BY THE FIELD ENGINEER.

1'-0"

MAX. 4'-10" MAX. 4'-10"

4/12/10

PROTECTIVE POLES FOR OIL FILLED

PAD-MOUNTED TRANSFORMERSSIMPSON SIMPSON ELKINS

CN 21002407

CN 21002407

0

3

2

1

APPR.REVISED BY CK'D

SEE NOTE 7

7. CN 9220151882 (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.

1. ON THREE-PHASE PAD-MOUNTED TRANSFORMERS,

2'-0" IN FRONT OF THE TRANSFORMERBETWEEN THE DOORS TO ACCOMMODATETHE DOOR SWING AND SHALL BE REMOVABLE.

THIS POLE SHOULD BE CENTRALLY LOCATED

POLE SHOULD BE LOCATED APPROXIMATELY3'-6" IN FRONT OF THE TRANSFORMER (NO

ON SINGLE-PHASE TRANSFORMERS, THIS

LESS THAN 3').

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.

1/27/12 SIMPSON

5'-2"MAXIMUM

5'-2"MAXIMUM

SIMPSON ELKINS

DWG.

27.06-09

NOTES:

1. IF THE RECOMMENDED CONDUCTOR LIMITS ABOVE ARE EXCEEDED, THE CUSTOMER MUST CONSIDERINSTALLING 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 BYTHE CUSTOMER AS SHOWN ON DWG. 27.06-08.

4/12/10 SIMPSON SIMPSON ELKINS

RECOMMENDED NUMBER OF CUSTOMERCONDUCTORS IN SECONDARY COMPARTMENT

OF THREE-PHASE PAD-MOUNTED TRANSFORMERS

PER PHASE IN PAD-MOUNTED TRANSFORMERSRECOMMENDED NUMBER OF CUSTOMER CONDUCTORS

TRANSFORMER SIZEPAD-MOUNTED

(KVA)

300

500

1000

750

1500

2500

150

20

20

8

8

8

75

8

8

8

NUMBER OFHOLES IN

SECONDARYBUSHING SPADE

3750 20

0

3

2

1

APPR.REVISED BY CK'D

2. SEE DWG. 27.06-12 FOR TRANSFORMER SECONDARY SPADE BLOCK TERMINALS.

480Y/277

NUMBER OFHOLES IN

SECONDARYBUSHING SPADE

208Y/120

3. MAXIMUM CUSTOMER CONDUCTOR SIZE IS 750 KCMIL CU/AL.

4. PARALLELED CUSTOMER CONDUCTORS MUST BE "RUNG OUT" PRIOR TO ENERGIZING TO PREVENT CROSSPHASING.

N/A

N/A

10

20

8

8

8

8

N/A

16

16

12

12

12

12

12

12

16

480Y/277

N/A

N/A

16

16

12

12

12

12

N/A

208Y/120

5. SIX-CONDUCTOR SECONDARY SPADE BLOCK TERMINALS REQUIRE THAT A MINIMUM OF SIX BOLT HOLES BEATTACHED TO SECONDARY BUSHING SPADE OF TRANSFORMER. EIGHT-CONDUCTOR BLOCKS REQUIRE AMINIMUM OF EIGHT BOLT HOLES BE ATTACHED TO SECONDARY BUSHING OF TRANSFORMER.

4/1/11 SIMPSON SIMPSON ELKINS

1/27/12 SIMPSON SIMPSON ELKINS