ANSI 3 PHASE - PADMOUNTED TRANSFORMERS - MTR



ANSI 3 PHASE - PADMOUNTED TRANSFORMERS - MTR

This specification covers Distribution Padmounted Transformers 45—2500 kVA.

KVA High Voltage Low Voltage

45 - 150OKVA 4160GY/2400 - 34500GY/19920 600V and below, Wye or Delta

2400 Delta - 34500 Delta

2000-25OOKVA 7200GY/4160 - 34500GY/19900 600Y/347, 480Y/277

4160 Delta - 34500 Delta

The following major selections are required:

Paragraph 1.0 Choice - Scope - Type of cooling fluid

Paragraph 2.0 Input - Ratings

Paragraph 2.2 Choice - Ratings, AWR (65 C or 55 C)

Paragraph 3.1 Choice - Cabinet Security (Pentahead or Hexhead)

Paragraph 3.3 Choice - Cable feed (Radial, Loop, or shown on drawings)

Paragraph 4.1.5 Choice - Accessory — (Pentahead or Hexhead) Bolt

Paragraph 5.1 Choice - High Voltage Terminations

5.1 Dead Front — Wells and Inserts

5.1 Live Front — Porcelain Bushings

Paragraph 6.0 Option - High Voltage Switching - (LBOR) Switch

Paragraph 7.0 Option - High Voltage Fusing

1. Protective fuse links are rated maximum 3500 AIC at 8.3kV maximum voltage

2. Bayonet fuse links are rated maximum 3500 AIC at

8.3 kV maximum voltage

3. Partial range current limiting fuses available in series with expulsion type fuses. (only if (1) or (2) is provided)

4. Full range current Limiting fuses

a. NX, ELX type fuses which are rated 50,000 AIC rms symmetrical and are available through 15 kV

in a draw—out loadbreak, dry fuse well

B. NX, ELX type fuses which are rated 50,000 AIC rms symmetrical and are available through 23 kV

in a draw—out non-loadbreak, dry fuse well

5. Clip—mounted McGraw NX current limiting fuses located in the HV compartment (Live front only)

Paragraph 8.0 Option — High Voltage Surge Arresters

8.1 Dead Front — Metal Oxide Varister Elbow

8.1 Dead Front — Underoil. Metal Oxide

8.1 Live Front — Distribution Class, Metal Oxide

Paragraph 10.1 Option — Low Voltage Apparatus

10.1.1 Mounting plates for CTs and PTs.

1. Mounting provisions — breaker

2. 10.1.1 Individual breaker(s) mounted and wired.

Paragraph 10.1.1 Option — Low Voltage Apparatus, Circuit Breaker description.

PADMOUNTED TRANSFORMERS (2500 kVA and below)

1. SCOPE

1.1 This specification shall cover *[mineral oil] [high flash point hydro—carbon fluid] immersed three phase padmounted transformers of low silhouette design, 2500 kVA, or below with ratings noted below or as shown on the drawings.

1.2 The equipment to be furnished shall be designed, built and tested in accordance with the latest revision of all applicable standards of IEEE, NEMA, and ANSI. Transformer shall be designed for outdoor application at altitudes not to exceed 3,300 feet, in an ambient not exceeding 40 degrees C and average ambient for any 24—hour period not exceeding 30 degrees C.

** 2. RATINGS

2.1 The ratings of the transformer(s) shall be as follows or as shown on the drawings:

kVA: ______________

Frequency : ______________ hertz

Impedance: ______________ % (+7.5% tolerance)

Primary Voltage: ______________ volts _________ connected

______________ volts _________ connected

Primary Taps: ______________ +2~2 @ 2.5%

Primary BIL: ______________ kV

Secondary Voltage: ______________ volts _________ connected

Secondary BIL: 30 kV

2.2 The transformer shall carry its continuous rating with average winding or temperature rise by resistance that shall not exceed

*(55) (65) degrees C.

3. GENERAL CONSTRUCTION

3.1 The transformer tank and terminal compartment shall be bolted together to form an integral unit of the outdoor weather—resistant type. The terminal compartment shall be completely enclosed with one high voltage and one low voltage compartment door. There shall be no bolts, screws, or other fastening devices which are externally removable, with the exception of *(pentahead) (hexhead) bolts for security, that provide access to the energized parts within the enclosure. The enclosure shall be tamper—resistant design meeting the requirements of ANSI C57.12.28 — 1988 “Padmounted Equipment — Enclosure Integrity for Switchgear and Transformers”.

* Note to Spec Writer — Choice, select only one.

** Note to Spec Writer — Input required.

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3. GENERAL CONSTRUCTION (cont.)

3.2 Full height, air—filled incoming and outgoing terminal compartments with hinged doors shall be located side by side, separated by an isolating barrier. The doors shall be attached with stainless steel hinges and hinge pins and incorporate a three point latching mechanism operated by the low voltage door handle, with door stops on both doors to secure doors during servicing. To facilitate making connections and permit cable pulling, the doors and compartment hood shall be removable. A removable door sill shall be provided to permit rolling or skidding the unit into place over conduit stubs in foundation.

3.3 The high voltage compartment shall be on the left, and shall be accessible only after the door to the low voltage compartment has been opened. The high voltage compartment shall enclose the high voltage bushings or bushing wells and provide for incoming cable from below. The high voltage equipment shall be arranged for *(radial—feed)(loop—feed)(the type of feed as shown on the drawings).

4. STANDARD ACCESSORIES

4.1 The unit shall be equipped with the following standard accessories.

4.1.1 A weather cover over the cabinet is to be provided with additional hold—down hardware to secure it more firmly to the cabinet.

4.1.2 Four lifting hooks.

4.1.3 Bolted—on terminal compartment *[18 inches] [24 inches] [30 inches] [40 inches] deep with removable front sill.

4.1.4 Hinged, lift—off cabinet doors.

4.1.5 Interlocked *[penta—head] [hex—head] bolt/padlock handle to operate a cam assembly which is to be part of the three point door latching mechanism.

4.1.6 Tank ground pads (1 in HV - 1 in LV).

4.1.7 Steel high/low voltage compartment barrier.

4.1.8 Two 1/2 inch *[penta-head] [hex-head] bolts which must be removed from the steel high/low barrier before the HV door can be opened.

* Note to Spec Writer — Choice, select only one.

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4. STANDARD ACCESSORIES (cont.)

4.1.9 Nameplate — A durable metal nameplate made of corrosion—resistant material and conforming to ANSI/IEEE C57.12.00 — 1980 affixed to each transformer.

4.1.10 Oil level/fill plug and oil drain plug.

4.1.11 Self—actuating pressure relief device to relieve slow pressure build—up shall be provided that will automatically vent when pressure reaches l0(±2) PSI and recloses when pressure falls to 6 PSI.

4.1.12 Removable neutral ground strap.

4.1.13 Five—legged core/coil assembly suitable for grounded WYE—grounded WYE connections, DELTA-ground WYE connections or DELTA—DELTA connections as required.

4.1.14 Handhole cover bolted onto tank top (protected by weather cover).

4.1.15 Tap changer handle for de—energized operation only.

4.1.16 Drain valve with sampling device.

4.1.17 Liquid level gauge.

4.1.18 Dial type thermometer.

4.1.19 Provision for pressure vacuum gauge.

4.1.20 Lightning arrester mounting pads (live front only).

5. HIGH VOLTAGE TERMINATIONS

* 5.1 DEAD FRONT construction, with externally clamped high voltage epoxy bushing wells with loadbreak 200 ampere inserts. Contractor to provide loadbreak elbows for the size and type cable shown on the drawings.

* 5.1 LIVE FRONT construction, with externally clamped high voltage porcelain bushings with a double eyebolt for 2/0 cable (45—225 kVA) or a single eyebolt for 4/0 cable (300—2500 kVA).

* Note to Spec Writer — Choice, select only one, DEAD FRONT or LIVE FRONT

*** Note to Spec Writer — Option.

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*** 6. HIGH VOLTAGE SWITCHING

6.1 Oil immersed switching

6.1.1 Designed for padmounted transformers enabling an operating person to quickly isolate a line fault in a loop feed

system, while maintaining full service continuity.

6.1.2 Available in 200 300 400 and 600 amp, hook stick operable.

Available at the following ratings, as defined by ANSI

Standard C37.72, 1987, American National Standard

Requirements for Manually—operated, Dead Front Padmounted

Switchgear with Load Interrupting Switches and Separable

Connectors for Alternating—Current Systems.

6.1.3 The electrical characteristics of each rating:

Ratings 200A – 300A 400A 600A

Maximum Voltage:

10(Line —Ground) 21.9 kV 15.5 kV 8.3 kV

Impulse Withstand Voltage 125-150 kV 150 kV 95 kV

Continuous and 200-300 A 400 A 600 A

Interrupting Current

Momentary & Making Current:

(Sym) l0 kA l6 kA lO kA

(RMS)(Asym) 16 kA 25.6 kA 10 kA

60 Hz Withstand Voltage:

Design 70 kV 60 kV 35 kv

Production 50 kV 40 kV 34 kV

Corona Extinction Voltage (RMS) 26 kV 19 kV 11 kV

Mechanical Operations 500 + 500 + 500 +

*** Note to Spec Writer — Option.

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*** 7. HIGH VOLTAGE FUSING

7.1 The high voltage shall include the following:

+7.1.1 Protective fuse link consisting of an internal, oil immersed, expulsion type fuse made of a fiber tube supporting and surrounding the fuse element. Protective fuse link to be replaceable through the handhole cover located on the tank top. The link is to be sized to operate only in the event of a winding failure, isolating the transformer from the primary system.

+7.1.2 Bayonet—type fuse assembly shall be of a

hookstick—operable, drawout, loadbreak design. The fuse

shall be either a dual—sensing or current-sensing with

an internal isolation link supplied in series for

additional safety. The fuse is to be sized for protection from

secondary system faults or heavy overload conditions. The dual

sensing fuse shall provide additional protection against long

term transformer heating.

+7.1.3 Partial range current limiting fuses consisting of

internal, oil immersed, block mounted fuses mounted inside

the tank. Either the protective expulsion fuse link (1) or the

bayonet expulsion fuse link (2) must be connected in series with

the partial range current limiting fusing for complete

system protection.

+7.1.4 Full range current limiting fuses consisting of a general

* purpose [ELX], [NX] fuse mounted in a loadbreak or non- loadbreak draw—out Dry Fuse Well. The current limiting fuse shall be designed to limit both the current magnitude and the energy associated with low impedance faults.

7.1.5 Clip mounted current limiting fuses consisting of Cooper

NX fuses clip mounted and bolted to the high voltage

bushings and insulators located in the high voltage

compartment. Available only in a LIVE FRONT design with

porcelain bushings.

7.2 Fuses to have continuous current ratings sized per the manufacturer’s recommendation for the indicated kVA, impedance and primary voltages.

* Note to Spec. Writer -- Choice, select only one.

+ Note to Spec. Writer -- Choice, select either (l,2,l&3,2&3,4 or 5).

*** Note to Spec. Writer — Option.

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*** 8. HIGH VOLTAGE SURGE ARRESTERS

8.1 Dead front — The transformer shall be designed as loop—feed, but utilized as radial—feed with second set of wells used for dead front arresters. Provide dead front metal oxide varistor elbow arresters.

8.2 Dead front — Underoil surge arresters shall be of the metal oxide type of the Distribution Class, installed in the tank and block mounted underoil.

8.3 Live Front — Surge arresters shall be of the metal oxide type of the Distribution Class, installed in the high voltage compartment and appropriately grounded.

9. LOW VOLTAGE TERMINATIONS

9.1 The low voltage compartment shall be arranged for cabling from below. Three line bushings and one insulated neutral bushing with an externally removable ground strap shall be supplied. The bushings shall be supplied with spade type terminations and standard NEMA spacing and drilling.

9.2 Externally clamped low voltage epoxy or polyester bushings with threaded copper studs and NEMA four hole rotatable spades (45 to 500 kVA), NEMA eight hole rotatable spades (750 to 2500 kVA).

*** 10. LOW VOLTAGE APPARTUS

10.1 Low Voltage compartment shall include the following additional equipment:

10.1.1 Mounting plate for CTs and PTs in low voltage compartment where shown on the drawings.

10.1.2 Provisions for mounting molded case breaker(s)low voltage compartment where shown on the drawings.

10.1.3 Individual breaker(s) mounted and wired by the manufacturer from the low voltage bushing spades to the line—side of the breaker(s).

** _______ Qty _________ Amp ______ Pole _____________SYM AIC

* Note to Spec Writer — Choice, select only one.

** Note to Spec Writer — Input required.

*** Note to Spec Writer — Option.

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11. ENCLOSURE & FINISH INTEGRITY

11.1 The enclosure shall be designed to meet the requirements of ANSI C57.12.28 — 1988 “Padmounted Equipment — Enclosure Integrity for Switchgear and Transformers”. To comply, all tank, cabinet, and fin steel shall be shot—blasted prior to application of the protective finish to comply. The finish process should include an epoxy primer and a final urethane coat. The total, film thickness applied shall be 3.0 MIL thickness as determined by testing per U.P.A. Technology MINIDERM S-100A standard.

11.2 The paint finish shall be capable of passing a 1500 hours Salt Spray test per ASTM B117 and Federal Specification TT—P—141 with NO blistering and passing method 6061 with less than 1/16 inch underfilm corrosion.

11.3 The paint finish shall be capable of passing a5 1000 tours Humidity test with 98% relative humidity at 45 C, ±1 C with no blistering.

11.4 The paint finish shall be capable of passing a direct impact test per ASTM D—2794 for values greater than 160 in—lbs. and also capable of passing a crosshatch—tape adhesion test.

11.5 The paint finish shall be capable of passing oil resistance tests of three days immersion at room temperature and three days immersion at 1000C with no apparent effect. The paint color shall be GREEN 7GY/3.29/1.5MUNSELL.

12. TESTING PROGRAM

12.1 The following tests shall be made on all transformers. The numbers shown do not necessarily indicate the sequence in which the tests shall be made. All tests shall be made in accordance with the latest revision of ANSI Standard Test Code C57.12.90, where applicable.

12.2 Transformers shall pass the following routine electrical tests:

12.2.1 Ratio Test

12.2.2 Demagnetization Test

12.2.3 Applied Voltage Test of High Voltage

12.2.4 Applied Voltage Test of Low Voltage

12.2.5 400 Hertz Induced Voltage Test

12.2.6 Iron loss and Exciting Current Test

12.2.7 Impedance and Load loss Test

12.2.8 Full Wave Impulse Test.

12.3 Transformers shall pass a Mechanical Leak and Pressure Test on tank and coolers

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12. TESTING PROGRAM (cont.)

12.4 The following ANSI basic design tests are to be made on a sufficient number of transformers and ratings to demonstrate compliance with these standards. Design tests are not required to be repeated unless the design of the transformer is changed so as to modify the reliability of predicated results.

12.4.1 Short circuit

12.4.2 Audible sound level

12.4.3 Temperature rise

12.4.4 Power factor

12.5 Certified copies of actual loss data for the standard tests and test data on basic design shall be furnished upon request by the engineer.

13. QUALITY

13.1 Transformers addressed by this specification are subject to a quality program which establishes requirements to assure that the transformers provided by the vendor will comply with Industry Standards or this specification.

13.2 This specification covers three phase padmounted transformers,

2500 kVA, or below with ratings noted on page 1 or as shown on the drawings. The transformers shall be Asea Brown Boveri (ABB) MTR or equal.

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