UPS Bypass Line Transformer Material Selection Criteria & Checklist

This article is about UPS Bypass Line Transformer Material Selection Criteria & Checklist & Requirements of Electrical Power System as per International Codes and standards for Commercial Buildings, Plants and Refinery Projects.

UPS Bypass Line Transformer Material Selection Criteria & Checklist

QC Before Installation- Bypass Line Transformer shall conform to all applicable requirements, standards, and specifications prior to release to be used as part of work.
Incoming Bypass Line Transformer shall be visually inspected for damage / defects occurred during transportation and conformance to all applicable requirements.
Bypass Line Transformer shall be new and unused.
Bypass Line Transformer shall be in accordance with the Saudi Aramco-approved project-specific design drawings, diagrams, schedules, lists, databases, and associated design documents.
Check that the Contractor or it’s Saudi Aramco approved third party inspector performed the quality activities at the supplier and sub-supplier locations as required by the inspection level assigned for the materials and equipment identified in SAER-1972 Inspection Requirements.

All transformers shall be designed and tested in accordance with ANSI/NEMA ST 20 or IEC 60076.
A stand-alone (separate from the UPS cabinets) dry type, shielded isolation transformer, shall be provided in the UPS bypass AC line circuit.
The K factor of the bypass transformer shall be minimum K-4. A higher K factor transformer shall be provided if specified on the Data Schedule to withstand heating effects of loads with a higher degree of non-linearity
For aluminum wound transformers, a 220°C insulation system shall be used. Winding temperature rise shall not exceed 150°C at full rated load in a 40°C ambient environment.
For copper wound transformers, a 180°C insulation system shall be used. Winding temperature shall not exceed 115°C at full rated load in a 40°C ambient environment.
The primary of the bypass AC line transformer shall contain one tap 5% above nominal voltage and two taps each 5% below nomimal voltage.
The neutral bar of the bypass AC line transformer shall be sized for at least 200% ampacity of the secondary phase conductors.
Enclosures over 60 lbs in weight shall be provided with brackets, holes or other means for lifting. NEMA ST20 Sec. 3.2
“Enclosures shall be non-combustible and corrosion resistant.
NEMA ST20 Sec. 3.3.1”
“Wiring compartment shall provide adequate space for the size cables which provide the ampacities required by the National Electrical Code.
NEMA ST20 Sec. 3.4.2.1”
The transformer core shall be grounded to the transformer frame and enclosure. NEMA ST20 Sec. 3.2.2
“Nameplates shall specify the following information: Ratings for KVA, Voltage, Frequency, Phases, Temperature Rise, Vector Diagram, Tap voltages, Connection Diagram, % Impedance and weight if over 100lbs, Name of Manufacturer and Transformer Identification.
NEMA ST20 Sec. 3.25”
“Terminal Markings, shall be provided and placed next to the terminals and shall consist of a capital letter followed by a roman numeral.
NEMA ST20 Sec. 3.29”
“Sound levels shall not exceed the values given in Table 3-9.
(See Attachment) NEMA ST20 Sec. 3.32”
“Transformer tests shall be in accordance with Section 4, Table 4-1.
(See Attachment) NEMA ST20 Sec. 4”
All internal devices and components shall be provided with an identifying number or a nameplate to identify the item and its function. Nameplate abbreviations shall match the item description shown on the UPS schematic drawings.
“Instruction Manuals
Each system shall be provided with instruction manual(s) including the following information as a minimum. The required number of sets shall be as specified on the buyer’s Non-Material Requirements for Interruptible Power Supply (UPS) Form NMR-9597.
a) Installation & commissioning instructions
b) Operating instructions
c) Wiring & schematic diagrams
d) Service instructions with calibration & trouble shooting guide
e) Factory Test procedures & Certified test reports”
Check that the UPS system are supplied from the approved manufacturer as per Regulated Vendors List for Electrical Equipment. SAES-P-101 (09 June 2007 Issue) SAES-P-101 (29 Feb. 2004 Issue)

International Standard and Codes for UPS Static Switch

1. Non-Hazardous Indoor Enclosures, Installation and Pre-Commissioning
2. Boxes, Enclosures, and Accessories Materials Selection & Requirements

3. 17-SAMSS-516 Uninterruptible Power Supply System, 17 August 2007
4. NEMA ST20 Dry Type Transformers for General Applications, 1992 Edition
5. SAES-P-101 Regulated Vendors List for Electrical Equipment, 09 June 2007

ATTACHMENT(S): 1. Attachment – 1 NEMA ST20 Table 3-9, Average Sound Level and Table 4-1, Routine Test (Transformers)