Annex_1_Transformer_Specific_Requirements.pdf

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Annex 1 - Transformer-Specific Requirements

1. Requirements

The transformer information and specifications in this section are for the equipment referenced in Specification “Power Transformer, The City of Palo Alto Utility Department”, and shall be used in conjunction with the requirements of this Specification.

In this section, a box checked (✔) next to an item indicates that the item is required or applicable; a box not checked indicates that the item does not apply or is not acceptable.

The meanings of the following symbols used by the company are defined as:

✔ Denotes a normal requirement.

* Denotes a requirement which will be specified at the time of order.

** Denotes a requirement to be specified by the supplier.

NA Denotes Not Applicable

Denotes a requirement which may be specified at the time of order; the supplier shall provide an adder.

2. General Requirements

Work order number: 40031443

REQ number: *

Equipment number(s): EM-20, EM-21, HO-20, HO-21, CO-22, CO-23

Location:

620 East Meadow Dr, 1350 Hopkins Ave, 1040 Colorado Ave Palo Alto, CA 94303

3. Equipment Identification and Order Requirements

Delivery location: 2 per address listed

Delivery date:

2 transformers to be delivered at earliest available date, 2 transformers to be delivered 2 years after earliest available date, and 2 transformers to be delivered 4 years after earliest available date

Notice of shipment date: Earliest Available

Installation date: Earliest Available

City of Palo Alto representative:

Brandon Grossman, Project Engineer

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4. Service Conditions

4.1. Ambient Temperature

If checked (✔) below, the transformer and all associated components shall be designed for special low-temperature and/or high-temperature operation without de-rating.

-20°C daily minimum ☐

-10°C daily minimum √

+45°C daily maximum √

+50°C daily maximum ☐

4.2. Elevation

The transformer shall be designed for special high-elevation operation without de-rating, up to the specified elevation, if checked (✔) below.

3300 feet √

4.3. Unusual Service Conditions

List any unusual service conditions

5. Service Class

5.1. Service Class

The transformer shall be suitable for the class of service checked (✔) below.

Distribution step-down ☐

Power transformer step-up ☐

Power transformer step-down √

Transmission substation system tie step-up and step-down operation ☐

Core / shell form:

Core form √

Shell form ☐

Supplier’s choice ☐

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Core form:

Type 1 Core (3 limbs core for single phase) ☐

Type 2 Core (2 limbs core for single phase) ☐

Type 3 Core (3 limbs core for three phase) √

Type 4 Core (4 limbs core for single phase) ☐

Type 5 Core (5 limbs core for three phase) ☐

5.2. Phase Designation

The phase of the transformer shall be as checked (✔) below.

Single-phase ☐

Three-phase √

5.3. Winding Type

The transformer winding type shall be as checked (✔) below.

Two-winding √

Three-winding ☐ Three-winding autotransformer

5.4. Cooling Class

The cooling class shall be as checked (✔) below.

Self- cooled rating

ONAN ☐

Self- cooled rating and one forced-cooled rating

ONAN / ONAF ☐

Self- cooled rating and two forced-cooled rating

ONAN / ONAF / ONAF √

ONAN / ONAF / ODAF ☐

ONAN / ODAF / ODAF ☐

One of the classes checked above (supplier’s choice) ☐

One forced-cooled rating (no self-cooled rating)

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ODAF ☐

ODWF ☐

Two forced-cooled rating (no self-cooled rating)

ODAF / ODAF ☐

ODWF / ODWF ☐

Other class, as follows: ☐

6. Winding Designation

The IEEE winding designation per Table 7 (single-phase) / Table 8 (three-phase) of IEEE

C57.12.00 shall be as follows:

H-winding 115000 x 60000 V - Delta

X-winding 12470 Grd Y / 7200

Y-winding

6.1. Polarity or Angular Displacement

If the transformer is single-phase, the polarity shall be subtractive. If the transformer is three-phase, the angular displacement shall be as checked (✔) below in Figure 1.

6.1

6.6

6.2

6.7

6.3

6.8

6.4

6.9

6.5

Figure 1: Three-Phase Transformer Angular Displacement

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6.2. Neutral Grounding

Winding Solidly Grounded Grounded through impedance Isolated

High Voltage ☐ ☐ ☐

Low Voltage √ ☐ ☐

6.3. Capacity Ratings

The capacity ratings at 65° C average winding temperature rise for the HV-, LV-, and TV-terminals, as applicable, shall be as specified in the rows checked (✔) below in Table 1, Transformer Capacity Ratings.

Table 1—Transformer Capacity Ratings

Terminals Self-Cooled

(MVA)

First Stage Forced-Cooled

(MVA)

Maximum Forced-Cooled

(MVA)

H & X 20 27 34 √

Y See Note 2. ☐

Y ☐

Note 1. If designated by “**” in the table, the self-cooled and first-stage forced-cooled capacity ratings shall be selected by the manufacturer and need not be the standard values normally associated with the specified maximum forced-cooled capacity rating(s).

Note 2. If this row is checked, the Y-terminal capacity ratings shall be 35% of the ratings of the H and X terminals, or, for an autotransformer, 35% of the MVA parts of the largest of the series and common windings. The calculations for the largest parts for a non-load tap changing or a reduced capacity load tap changing autotransformer shall be calculated with Equation (1) and (2).

���� �………… . . (1)

��,��� = � × 1 −

�����………… . . (2)

Where

S is the output kVA rating of an autotransformer SS,max is the largest kVA rating for the series part of an autotransformer SC,max is the largest kVA rating for the common part of an autotransformer HVmax is the maximum high voltage rating HVmin is the minimum high voltage rating LVnom is the nominal low voltage rating

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6.4. Impedance(s)

Transformer impedance(s) shall be as checked (✔) below.

Selected by the supplier ☐

As specified below in Table 2 √

Table 2—Transformer Impedance(s)

Winding to Winding V

LL

Percent Impedance

Base

MVA

1. H to X 60 to 12.47 9.25% 20

2. H to Y to

3. X to Y to

4. H to X 115 12.47 9.25% 20

5. H to Y to

6. X to Y to

6.5. Insulation Levels

6.5.1. Transformer Class

Power transformer class as per IEEE C57.12.00 section 5.10 as follows:

Class I power transformer ☐

Class II power transformer √

6.5.2. Basic Insulation Level (Winding)

Terminals BIL (kV)

H 650 x 350

X 110

Y NA

Ho NA

Xo 110

HoXo NA

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6.6. Bank Operation and Parallel Operation

6.6.1. Bank Operation

If the transformer is single-phase, and if checked (✔), the transformer shall be suitable for operation in a three-phase bank with similar transformers as specified. The similar transformers are identified below, and the associated impedance test data and nameplate drawings are attached. ☐

6.6.2. Parallel Operation

If the transformer is three-phase, or single-phase operated in a three-phase bank, and if checked (✔), the transformer or transformer bank shall be suitable for operation in parallel with similar transformer(s) as specified. The similar transformer(s) are identified below, and the associated impedance test data and nameplate drawings are attached.

Six (6) 20/27/34 Transformers for Three (3), City of Palo Alto Substations, purchased using this specification.

6.7. Audible Sound Level

The transformer shall be designed to comply with the decibel rating as checked (✔) below.

NEMA TP-

80050

( 71 / 73 / 74 ) ☐ 5 dB below NEMA TP- 80050

( 66 / 68 / 69 ) √

Other ( / / ) ☐

The sound test shall include the load sound test

7. De-Energized Tap Changers

7.1. DETC Tap Voltages

If checked (✔), the transformer shall have a de-energized tap changer. √

The de-energized tap rating shall be as specified by the row check (✔) in Table 3.

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Table 3—De-Energized Tap Voltage Ratings (kV, L-L)

Desired Rating

Nominal System

Voltage

(kV, L-L)

Center Tap Voltage

Rating

(kV, L-L)

De-Energized Tap Voltage

Ratings

(kV, L-L)

√ 115 115 120 / 117.5 / 115 / 112.5 / 110

√ 60 60 63 / 61.5 / 60 / 58.5 / 57

7.2. Series-Parallel Reconnection

If checked (✔), means for series-parallel reconnection shall be furnished for the specified winding(s) as follows.

H-winding √

Reconnection by a de-energized switch ☐

Reconnection by a terminal board √

X-winding ☐

Reconnection by a de-energized switch ☐

Reconnection by a terminal board ☐

Special requirements:

1. The following shall be guaranteed in both 115kV and 60kV HV connections:

a. Impedance (as per technical specification section 5.5)

b. Load Loss (as per technical specification section 5.8)

2. The following shall be guaranteed on the HV connection that provides the highest

a. No-load Loss (as per technical specification 5.8)

b. Audible sound level (as per technical specification 6.2.3)

3. The following tests shall be performed in both 115kV and 60kV HV connections during the Factory Acceptance Test:

a. Winding DC resistance

b. Ratio and Phase relationship

c. Impedance and load Loss

d. Zero Sequence Impedance

e. Lightning Impulse

f. Induced voltage with Partial Discharge

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7.3. Wye-Delta Reconnection

If checked (✔), means for wye-delta reconnection shall be furnished for the specified winding(s) as follows.

-winding ☐

Voltage rating on the wye connection (as shown in Table 1): kV ☐

Voltage rating on the delta connection: kV ☐

Winding BIL on the delta connection: kV ☐

Reconnection by a de-energized switch ☐

Reconnection by a terminal board ☐

-winding ☐

Voltage rating on the wye connection (as shown in Table 1): kV ☐

Voltage rating on the delta connection: kV ☐

Winding BIL on the delta connection: kV ☐

Reconnection by a de-energized switch ☐

Reconnection by a terminal board ☐

Special requirements:

8. Load Tap Changer

If checked (✔), the following LTC equipment shall be furnished.

Type:

Mounted on the transformer tank wall √

Suspended from the transformer tank cover ☐

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Location and Function:

High-side / End of Series Winding in Auto for HV variation ☐

High-side / End of Series Winding for LV variation ☐

High-side / End of Series Winding for combined voltage variation ☐

Low-side / LV Line End in Auto for LV variation ☐

Low-side / LV Line End in Auto for HV variation ☐

Low-side / LV Line End in Auto for combined voltage variation √

At Auto connection ☐

At Auto-neutral end ☐

Phase(s):

Three-phase √

Single phase ☐

Type of Change-over Selector Switch:

Reversing √

Fine coarse ☐

Supplier’s choice from above ☐

Type of transition impedance:

Resistance type ☐

Reactance type √

Method of arc interruption:

Switched in vacuum √

Switched in non-vacuum ☐

If checked (✔) below, the following information shall govern.

Model BIL (kV) Current (A) (✔)

Reinhausen RMV-II Supplier’s Choice Supplier’s Choice

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8.1. Tap Range and Capacity

The LTC shall regulate the 12,470V terminal voltage

Percentage voltage range: ± 10%

+/- Steps: 16 steps above & below nominal (0.625% steps)

The voltage output of the tertiary winding must be constant ☐

The LTC shall have the following capacity on taps below the neutral:

Reduced capacity ☐

Full capacity √

8.2. Automatic Control

8.2.1. Beckwith

If checked (✔), automatic control using a Beckwith M2001D shall be supplied. The LTC equipment will be furnished with a Beckwith M-2948 tap position sensor. The 4-20 mA wiring connections from the Beckwith M-2948 will be terminated at Beckwith M-2025D Current Loop Interface module in the main control cabinet; the M-2025D will provide LTC tap position indication into the M2001D Beckwith LTC controller.

Any specific to go with this selection:

8.2.2. Reinhausen

If checked (✔), automatic control using a Reinhausen Manufacturing TAPCON 250 shall be supplied. ☐

8.2.3. Supplier’s choice

If checked (✔), supplier will choose one of the options from above sections 8.2.1-2 with the consultation of the company of suggest equivalent to the company. √

Control wiring shall be terminated on twelve (12) point Marathon blocks or CPAU approved equal.

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8.3. LTC Backup Control Relay

If checked (✔), a Beckwith LTC backup control relay model M-0329A or equal shall be furnished. √

8.4. LTC Parallel Balancing Module

If checked (✔), a Beckwith LTC parallel balancing module model M-0115A or CPAU approved equal shall be furnished. √

8.5. Latching Switch Relay (LSR)

If checked (✔), following LSR type switch shall be furnished. ☐

Electroswitch √

8.6. Remote Indication

If checked (✔), provisions for LTC remote indication shall be furnished by wiring a dry contact from the LSR switch to the terminal blocks for customer connection to SCADA for status indication.

8.7. Control Switch Relay (CSR)

If checked (✔), following CSR type switch shall be furnished. ☐

Electroswitch √

8.8. Remote Control

If checked (✔), provisions for LTC remote control shall be furnished by wiring CSR switch to SCADA dry contacts. √

8.9. LTC Instrumentation and Monitoring Equipment

8.9.1. Liquid Level Indicator

MESSKO MTO-STF160 or CPAU approved equal √

8.9.2. Dehydrating breather

MESSKO MTraB or CPAU approved equal √

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8.9.3. Oil Temperature Indicator (OTI)

QUALITROL or CPAU approved equal √

8.9.4. Pressure relief device

QUALITROL XPRD or CPAU approved equal √

8.9.5. Rapid Pressure Rise Relay (RPRP)

QUALITROL 900 Series or CPAU approved equal √

8.9.6. Seal-in-relay

QUALITROL 909-300 or CPAU approved equal √

9. Auxiliary Equipment

9.1. Bushings

9.1.1. BIL Requirements

Terminals BIL (kV)

H 650 x 350

X 150

Y NA

Ho NA

Xo 110

HoXo NA

9.1.2. Insulator material

Porcelain ☐

Polymer ☐

Composite ☐

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Supplier’s choice √

9.1.3. Insulator color

ANSI/IEEE No.70 light gray √

9.1.4. Approve Bushing supplier(s)

ABB(Hitachi), Siemens, AREVA, PCORE √

9.1.5. Bushing(s) of choice

Terminal Manufacturer Catalog number Voltage

(KV)

BIL (kV) Current

(A)

9.1.6. Bushing Connection Box

Provide Bushing Connection Box For LV ☐

LV Arresters are to be located in this connection box ☐

Bus Duct will be connected to LV bushing connection box ☐

LV Bushing Center Line-To-Center Line Spacing TBD

LV Bushing Center Line Height Above Transformer TBD

9.2. Arrester Provisions

Transformer arresters shall, or shall not, be provided as follows:

Surge arresters shall not be provided by the supplier ☐

Surge arresters shall be provided by the supplier √

If checked (✔) above Surge arresters shall be provided by the supplier, the Surge arresters shall have the following characteristics:

9.2.1. Arrester rating(s)

Terminal Duty Cycle Rating (kV) Maximum Continuous Operating Voltage (kV)

H1, H2, H3 144 115

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X1, X2, X3 12 10.2

9.2.2. Insulator material

Porcelain ☐

Polymer √

Composite √

9.2.3. Insulator color

ANSI/IEEE No.70 light gray √

9.2.4. Approve Arrester supplier(s)

ABB(Hitachi), Cooper Power Systems, General Electric, Hubbell, Siemens √

9.2.5. Arrester(s) of choice

Terminal Manufacturer Catalog number Duty

Cycle

(KV)

MCOV

(kV) Rated

SC

Current

Energy Rating

H1, H2, H3

Hubbell or

CPAU

approved equal

SVN144CA155AA 144kV 115kV

65kA 13kJ/kV-

MCOV Energy

Class G

X1, X2, X3

Hubbell or

CPAU

approved equal

EVP001000 12.2kV 10kV

63kA 9kJ/kV-MCOV

Energy Class E √

9.3. Instrumentation and Monitoring Equipment

9.3.1. Oil Temperature Indicator (OTI)

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9.3.2. Winding Temperature Indicator (WTI)

9.3.3. Liquid Level Indicator Oil

Main Tank:

Conservator Tank (if applicable):

QUALITROL or CPAU approved equal ☐

9.3.4. Time delay relay

Agastat or CPAU approved equal √

9.3.5. Temperature Monitor

QUALITROL ITM 509-300DW or CPAU approved equal √

9.3.6. Dissolved Gas Analysis (DGA) Monitor

GE TRANSFIX DGA 500 or CPAU approved equal √

9.4. Cooling Equipment

9.4.1. Pump(s) – Not allowed

9.4.2. Fan(s)

Vendor:

Krenz-Vent √

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Voltage rating:

240Vac single phase √

208/240Vac single phase ☐

208Vac three phase ☐

240Vac three phase ☐

480Vac three phase ☐

Other ☐

9.5. Current Transformers

The manufacturer shall furnish five-tap multi-ratio bushing current transformers (BCT) as specified below in Table 4, Bushing Current Transformers.

Table 4—Bushing Current Transformers

Terminals BCT Position Ratio Relaying Accuracy

H1,2,3 or H1 Top (H1, H2, H3) 1200:5A C400

H1,2,3 or H1 Middle (H1, H2, H3) 1200:5A C400

H1,2,3 or H1 Middle

H1,2,3 or H1 Middle

H1,2,3 or H1 Middle

H1,2,3 or H1 Bottom

H0 n/a

X1,2,3 or X1 Top (X1, X2, X3) 3000:5A C400

X1,2,3 or X1 Middle

(X1 LDC CT) 2400:5A

Single Ratio C200

X1,2,3 or X1 Middle

(X1, X2, X3 ETM) (X2

also for Hot Spot Gauge) 2400:5A Single Ratio

C200

X1,2,3 or X1 Bottom

X0 or X2 Top (X0) 1200:5A C400

X0 or X2 Middle (X0) 1200:5A C400

Y1,2,3 or Y1 Top

Y1,2,3 or Y1 Bottom

Y2 n/a

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If checked (✔), Line drop compensator CT shall be furnished. ☐

9.5.1 CT’s shall be supplied by the following vendor

Meramec or CPAU approved equal √

9.5.2 CT shorting blocks shall be supplied by the following vendor

Marathon or CPAU approved equal √

9.6. Insulating Liquid

Insulating liquid shall be:

Mineral oil (Ergon HyVolt ll NG or CPAU approved equal) √

9.7. Liquid Preservation System

The type of oil preservation system shall be as checked (✔) below:

Sealed-tank system ☐

Nitrogen gas pressure system ☐

Self-Generating Nitrogen gas pressure system √

Conservator system ☐

Nitrogen gas pressure or conservator system (manufacturer’s choice) ☐

If Conservator system checked (✔) in 9.7, below components shall be supplied:

If Self-Generating Nitrogen gas pressure system is checked, it shall be:

Waukesha Nitrogen Generator N2GEN-400 or CPAU approved equal √

9.7.1. Dehydrating breather (Conservator Only)

MESSKO MTraB ☐

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9.7.2. Gas detector relay (Conservator Only)

MESSKO MSafe ☐

EMB Buchholz BF80/10 ☐

QUALITROL 038 ☐

9.8. Pressure relief device (Main Tank)

QUALITROL XPRD √

Supplier’s choice ☐

9.9. Rapid Pressure Rise Relay (RPRP) – Main Tank

QUALITROL 900 Series √

9.10. Alarm Monitor

If checked (✔), the transformer shall be furnished with an alarm monitor. ☐

9.11. Auxiliary Power

9.11.1. AC Voltage

The AC power supply will be as checked (✔) below:

120 / 240 VAC, three-wire √

208 VAC, single-phase ☐

120 / 208 VAC, three-phase ☐

VAC, single-phase ☐

VAC, three-phase ☐

9.11.2. DC Voltage

The DC power supply will be as checked (✔) below:

48 VDC ☐

125 VDC √

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10. Site Commissioning

If checked (✔), the site commission tests shall be performed by the supplier. ☐

If checked (✔), the site commission tests for the DGA monitor will be performed by the supplier.

11. Tank

11.1. Location of Accessories

All accessories shall be located per Section 5 of IEEE C57.12.10 unless otherwise requested as checked (✔) below.

S1 S2 S3 S4 Liquid level indicator √ ☐ ☐ ☐ Liquid temperature indicator √ ☐ ☐ ☐ Winding temperature indicator √ ☐ ☐ ☐ Nameplate √ ☐ ☐ ☐ Auxiliary cooling control (control cabinet) √ ☐ ☐ ☐ LTC equipment (if wall-mounted) √ ☐ ☐ ☐ Conservator (if specified) ☐ ☐ ☐ ☐

Preference to have all the accessories on the same side of the tank ☐

The following equipment shall share a common centerline with that of the transformer base if checked (✔) below:

HV bushings √

LV bushings ☐

YV bushings (if specified) ☐

LTC equipment (if specified) √

Auxiliary cooling control (control cabinet) ☐

Conservator (if specified) ☐

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11.2. Contents for Shipment

The transformer tank shall be filled for shipment with contents as checked (✔) below:

Oil ☐

Dry air ☐

Manufacturer’s choice: √

12. Lost Cost Multipliers

The loss cost multipliers are as follows:

No-load loss cost multiplier (A) = $ 3000 . 00 / kilowatt

Load loss cost multiplier (B) = $ 1300 . 00 / kilowatt

Auxiliary loss cost multiplier (C) = $ 1300 . 00 / kilowatt

13. Receiving, Installation and Energization Requirements

The supplier shall be responsible for delivering the unit to the pad, assembling, oil filling, field testing, and providing certification that the transformer can be energized as checked (✔) below:

According to the City of Palo Alto’s Substation Operations Procedure √

According to the supplier’s standard methods ☐

Delivery to pad only (field assembly work not required) ☐

Other: ☐

For vacuum filling, the Leak Down (Leak Up) process shall be used √

14. Site-Specific Requirements

List any site-specific requirements below:

1. Transformer footprint shall be as small as possible.

2. 12.47kV Bushings to be top-mounted vertical bushings arranged for direct outdoor connection to owner-supplied open tubular bus.

Preliminary Bushing Locations: Per ANSI C57.12.10. Following segment assignments shall be confirmed with CPAU before manufacturing. See below:

HV Cover bushing: Segment 3

LV top bushing: Segment 4

Load Tap Changer and Control panel: Segment 1

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15. Design Requirements List any design-specific requirements below:

In section 8 of this document “Low-side / LV Line End in Auto for combined voltage variation” selected as “Location and Function” of LTC due to the following scenario on site:

The following table shows the statistics of daily recorded maximum and minimum voltages from March 27,2025 to March 26,2026 collected from

SCADA:

Maximum Voltage Values Minimum Voltage Values

Max 66.35 kV Max 65.26 kV

Min 64.43 kV Min 62.28 kV

Avg 65.37 kV Avg 64.11 kV

Median 65.37 kV Median 64.12 kV

The De-Energized Tap Changer (DTC) will be at tap position 3 (60kV). LTC will operate to compensate the voltage changes on the High Voltage side and the transformer will function as variable flux design. The transformer flux density shall be within the limit specified at section 6.2.2 in specification considering this scenario.

The Average Oil Rise over Ambient for most of the Transformers the company purchased in last 10 years were 35°C. The bid proposal shall be prepared using this information as design guide.