INSPECTION PROCEDURE FOR POWER TRANSFORMATOR

This list of standards is provided for guidance only and is not intended to be comprehensive. It is included to assist the Inspector in selecting relevant sources of information where client's specific requirements do not exist

TECHNICAL STANDARDS
The following standard may be used, but not limited to :

1. I.E.C. 76, International Standard for Power Transformers.
2. API  RP 500, Hazardous Area for Electrical Equipment.
3. ANSI. C.57.12.00, Test Code for Liquid Immersed Distribution, Power and Regulating Transformers.
4. NEC, National Electrical Code

INSPECTION PROCEDURE

INTRODUCTION

The inspection services setup in this procedure is a general guidance that shall be performed by the inspection personnel. The detail inspection and the acceptance criteria shall refer to applicable code and standard used that stated in contract document or client specification.

The inspection personnel shall be qualified by training and experience, such personnel shall be capable of performing the inspection services mentioned below

PRE-INSPECTION MEETING

Prior to manufacture testing of the generator, a pre-inspection  meeting shall be held, to setup an inspection and test plan, get information regarding to schedule, and other things that necessarily required in performing inspection. If no such meeting held then requirements must be established.

The inspection and test plan should contain item to be inspected and verified, which more detailed in section 6.4 Inspection below, acceptance criteria, verifying document, etc.

The agreed inspection and  test plan shall be as a reference of in performing inspection

DOCUMENT REVIEW

For certification purpose, the company shall review the design of power Transformer for appraisal such as following but not limited to :

• Code / standard used
• Owner specification (Design criteria)
• Data sheet
• One line diagram
• Wiring & schematic diagram
• Cable schedule
• Area classification
• Manufacture technical data
• Factory Acceptance Test Certificate
• Operating and maintenance procedure

VISUAL CHECK

The inspection personnel shall perform all inspections specifically required and other inspections as he believes are necessary to enable him to certify that power generator has been fabricated and installed in accordance with the requirements of code and standards referred to.

The required inspection and verification, which shall be performed by the inspection personnel, shall be adequate to make possible at least the following inspections at sufficiently frequent intervals to ensure good quality of workmanship :

• Name plate.
• Warning sign and safety personnel.
• Area classification
• Bushings and insulator.
• Lifting facilities.
• Drain valve operational and lockable.
• Dielectric sampling facilities.
• Main  cable and grounding.
• Tools and accessories

TESTING

After completion of fabrication and installation, the inspection personnel shall witness load test according to code and standard referred to.

In the process of load test, the following item, but not limited to shall be verified :

• High voltage isolation.
• Insulation resistance.
• Coolant dielectric strength
• Relays - Buchholz.
• Tap changing mechanism.
• Windings resistance.
• Voltage ratio.
• Losses 
• Excitation.
• Impedance and load loss.
• Polarity and vector or phase rotation.
• Temperature rise.
• Noise test.
• Short-circuit test.
• Tank pressure test

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