1.Background and Purpose

To meet the high-precision current measurement and protection requirements of Ecuador’s substations , the project team recently completed the installation and commissioning of outdoor 600V Extended Range Current Transformer (CTs). This testing verified that the selected CTs’ installation quality, full-load and overload performance, insulation withstand voltage, and accuracy met design standards and operational requirements, laying a solid foundation for official commissioning.

2.Equipment Overview

Models and specifications

CT Model: RECT -78A 300/ 5A

Rated primary current: 300 A, rated secondary current: 5 A

Accuracy class: 0.3B-0.5

Mechanical structure: epoxy resin casting, ring network structure, protection grade IP65

Installed on the outdoor switchgear side, it is used for current measurement and differential protection of medium and high voltage lines.

Connect to the electricity meter to provide real-time data for the power system and ensure intelligent monitoring of the distribution network .

3.On-site installation and preliminary inspection

Installation Preparation

Survey the geographical environment in advance, embed key components such as brackets , and ensure that all bolts and grounding studs comply with the requirements of the assembly drawings.

Appearance and insulation inspection of CT components

The CT shell has no cracks, bubbles or damage, and the outer surface has uniform color .

The primary and secondary terminals and binding posts are free of rust , and the insulating sleeves are intact and free of wear.

Ground connection

The CT metal casing is firmly connected to the ground wire, and the ground resistance test result is <0.5 Ω, meeting the operating specifications.

4.Field Testing and Data Recording

Insulation withstand voltage test

Apply an AC withstand voltage test voltage of 3 kV on the primary side for 60 s and ground the secondary side.

After the test, inspection found no partial discharge, breakdown or leakage, and the insulation performance was qualified.

Transformation ratio and load test

Use a standard ratio test device to test the CT with no load and load:

No-load error: < 1 %, in line with 0.1 level measurement requirements.

Full load error: < 3 %, in line with 0.3 level measurement requirements.

Short-time overload test

A short-term overload current of 31.5KA lasts for 1 second, and there is no visible damage to the CT, which meets the requirements .

Temperature rise test

In an environment not exceeding 55 degrees Celsius , no abnormalities occurred and the site met the design specifications.

5.System monitoring test

Secondary circuit wiring

For secondary wiring to protective devices, instrument cabinets , and switch cabinets , the torque of the wire end screws must meet the standards and must not be loose.

Acceptance conclusion

After on-site installation inspection, insulation withstand voltage, transformation ratio and load, phase difference, short-time overload, temperature rise and automation joint adjustment and other comprehensive tests, the CT performance indicators meet the requirements of the “Technical Specifications for Current Transformers for Power Systems” (GB/T 14285 2016) and design documents, and have the conditions for safe, reliable and long-term stable operation. It is recommended to be approved for formal operation.

7.Subsequent maintenance and suggestions

Regular inspections

It is recommended to conduct an appearance and grounding inspection, a ratio and insulation test every six months to ensure long-term performance.

Environmental Monitoring

The outdoor environment is dusty and humid. It is recommended to install a protective cover and regularly clean the dust on the CT surface to prevent insulation aging.

Data analysis

Use the digital analysis platform to analyze computer data , analyze the 600V metering CT operating status , and promptly identify potential faults and risks .

The acceptance test was successfully completed, and the equipment is in good operating condition. The relevant test reports and data have been archived. The project team will continue to monitor the operation and carry out subsequent maintenance and monitoring work according to the maintenance plan.

Compay：HEYI Electrical Co., Ltd.

Brand: HEYI/ASCT

Contact: Bethy

E-mail: heyi@heyiele.com             

Tel: 86-13968747975

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