Installation Construction Procedure for Pad-Mounted Transformers

James

Field: Electrical Operations

China

1. Scope of Application

This technical specification applies to the installation of pad - mounted transformers.

1.1 Construction Process

1.2 Standard Construction Process Description
2. Construction Preparation

(1) Main Machinery and Tools

Handling and Hoisting Tools: Truck crane, truck, winch, chain hoist, three - step rack, cribbing, steel wire rope, strap rope, rolling bar.
Installation Tools: Bench grinder, electric welding machine, gas welding tools, electric hammer, adjustable wrench, hammer, pipe - threading die, electrician's ladder, electric drill.
Testing Tools: Steel tape measure, steel ruler, level, plumb bob, megohmmeter, multimeter, clamp - on ammeter, thermometer, bridge and test instruments.

(2) Working Conditions

Construction drawings and technical documents are complete and correct.
The civil engineering works are basically completed, and the elevation, dimensions, structure, and strength of pre - embedded parts and weldments all meet the design requirements.
The site is cleaned up, and the roads are unobstructed.
The foundation of the pad - mounted substation is accepted and qualified, and the pre - reserved holes for the incoming and outgoing lines of the electrical conduits and cable conduits embedded in the foundation and the relevant pre - embedded parts are inspected and meet the requirements.

(3) Workers:

Main Construction Workers: Electricians, crane operators, commissioning workers. Construction workers must undergo regular vocational training and work with certificates.

3. Inspection of the Transformer Body

When the pad - mounted substation is delivered to the site, inspect the pad - mounted substation, the transformer body, nameplate parameters, random documents, as well as spare parts and components.

(1) Verify the certificate of conformity and accompanying technical documents. The pad - mounted substation shall have factory test records.

(2) The transformer shall be equipped with a nameplate. The nameplate shall indicate the manufacturer, rated capacity, primary and secondary rated voltages, current, impedance voltage (%), connection group, and other technical data. The accessories shall be complete; the insulating parts shall be free from damage and cracks; the oil - filled parts shall not leak; the air pressure indication of gas - filled high - voltage equipment shall be normal; and the coating shall be intact.

(3) Section Steel: Various specifications of section steel shall meet the design requirements and show no obvious rust.

(4) Bolts: Except for anchor bolts and bolts of anti - vibration devices, galvanized bolts shall be used, together with corresponding flat washers and spring washers.

4. Installation of Pad - Mounted Substation

(1) A dedicated lifting tool should be used to lift from the bottom.
(2) Place the pad - mounted substation horizontally on the pre - prepared foundation. Then, seal the gap between the product base and the foundation with cement mortar to prevent rainwater from entering the cable chamber. Connect the high - voltage and low - voltage cables through the bottom sealing plates of the high - voltage and low - voltage chambers.

(3) Seal the gap between the cable and the conduit to prevent water ingress.
(4) After installation in place, reliable grounding shall be ensured: The two main grounding terminals on the slot of the substation base, the neutral point and enclosure of the transformer, and the lower terminal of the arrester shall each be directly grounded. A set of grounding devices shall be used for all grounding points. Drive grounding piles at the four corners of the foundation and then connect them into a single unit. The grounding resistance shall be less than 4 ohms, and there shall be no fewer than two grounding leads from the grounding grid to the pad - mounted substation.

5. On - site Inspection and Electrical Testing

(1) The tests of the pad - mounted substation must comply with the following regulations:
For a pad - mounted substation composed of three independent units, namely a high - voltage switchgear, a low - voltage switchgear, and a transformer, the acceptance test for the high - voltage electrical equipment part shall be carried out in accordance with the provisions of the Standard for Acceptance Test of Electrical Equipment in Electrical Installation Engineering (GB50150) and be qualified.

(2) For a pad - mounted substation where high - voltage switch fuses and the transformer are combined in the same sealed oil tank, the tests shall be carried out in accordance with the requirements of the technical documents provided by the product.

(3) The tests of the low - voltage switchgear shall comply with the following regulations:
The specified models of each distribution switch and protection device shall meet the design requirements;
The insulation resistance value between phases and between phases and ground shall be greater than 0.5MΩ;
The AC withstand voltage test voltage for electrical devices is 1kV. When the insulation resistance value is greater than 10MΩ, a 2500V megohmmeter can be used instead. The test duration is 1 minute, and there shall be no flashover or breakdown phenomena.

6. Quality Acceptance

(1) Documentation: Factory - provided documents, installation and test records, construction drawings, and explanatory documents for design changes, etc.

(2) Before commissioning the pad - mounted substation, a comprehensive inspection of the equipment shall be carried out.

The high - voltage plug is reliably connected; the arrester and the pad - mounted substation are reliably grounded.
All meters on the high - voltage side indicate normally.
The plug - in fuse tube is installed in place; the tap - changing switch is in the correct position; the load switch is in the open position.
All electrical components on the low - voltage side are in the open state.

After the inspection is completed, before connecting the power supply and operating the load switch, the load switch operation instructions on the inner side of the high - voltage side door panel shall be read first, and then the equipment can be put into operation.

References

DL/T 5190.5 - 2004 Technical Specification for Construction and Acceptance of Electric Power Construction.
GB 50150 - 2006 Standard for Acceptance Test of Electrical Equipment in Electrical Installation Engineering.
DL/T 5161 - 2002 Regulations for Quality Inspection and Evaluation of Electrical Installation Engineering.