Post Insulator Dimensional Deviation Inspection Platform (Parallelism, Eccentricity, Camber & Shed Angle Tester) — GB/T 8287.1 / IEC 60168 Annex A

Post insulator deviation inspection platform at a glance

• Purpose: the shape and position deviation check of post insulators — parallelism, eccentricity, camber, shed angle, angular deviation of the fixing holes, structural height and shed diameter — on one platform.
• Standard: GB/T 8287.1-2008, Annex A (methods of checking the shape and position deviations), which corresponds to IEC 60168, Annex A, and to IEC 60168 Clause 5.1 (verification of the dimensions).
• Vertical module: 400 mm turntable, effective height 1000 mm, fitting flange up to 400 mm, turntable 0 – 2 rpm, lifting 500 mm/min, flatness and concentricity 0.1 mm.
• Horizontal module: digital inclinometer 4 x 90° with ±0.2° accuracy, structural height 0 – 1000 mm and shed diameter 0 – 500 mm digital calipers, lifting scale travel 0 – 300 mm.
• Measuring devices: shed angle by a 2500-line rotary encoder (0 – 90°, accuracy 0.1°); other deviations by four digital dial indicators (range 25.4 mm, accuracy 0.01 mm) with automatic deviation calculation.
• Data: one run acquires parallelism, eccentricity, camber and shed angle automatically and prints the statistics; data is uploaded by Modbus-RTU or Modbus-TCP.

1. What this platform is used for

Annex A of IEC 60168 / GB/T 8287.1 specifies the methods for checking the tolerances of parallelism, eccentricity, angular deviation, camber and shed angle of post insulators. If any of these deviations exceeds the tolerance, the insulator cannot be assembled correctly on the structure, the fixing holes will not match the stand-off fittings, and the specified creepage and clearance distances may not be maintained. The dimensional verification of Clause 5.1 is therefore a type test and sample test that every post insulator design has to pass before delivery.

The CT-PD26 covers the complete check on one platform, built from a vertical measuring module and a horizontal measuring module. The vertical module performs the parallelism, eccentricity, camber and shed angle checks, supported by the dedicated measuring software. The horizontal module performs the angular deviation of the fixing holes, the structural height and the shed diameter checks with digital read-out.

The platform is used by post insulator manufacturers, electric power companies and electrical testing laboratories, for sample tests and for routine dimensional inspection.

2. Standards applied

• GB/T 8287.1-2008 – Indoor and outdoor post insulators of ceramic material or glass for systems with nominal voltage greater than 1000 V – Part 1: Tests, Annex A – shape and position deviation check methods.
• IEC 60168 – Tests on indoor and outdoor post insulators of ceramic material or glass for systems with nominal voltages greater than 1000 V – Annex A: tolerances of parallelism, eccentricity, angular deviation, camber and shed angle; Clause 5.1: verification of the dimensions.
• Type and sample test – the dimensional verification of Clause 5.1 is a type test and a sample test, so it is carried out on every design and repeated on samples from production.

3. Technical parameters

Vertical measuring module

Horizontal measuring module

4. Key functions

• One run automatically acquires the parallelism, the eccentricity, the camber and the shed angle, controls the test sequence and prints the statistics at the end.
• Turntable rotates 360° without limit and the measuring unit travels over the full 1000 mm height, so the whole insulator is measured without re-fixing.
• Shed angle measured by a 2500-line rotary encoder over 0 – 90° with an accuracy of 0.1°.
• Four digital dial indicators with a range of 25.4 mm and an accuracy of 0.01 mm, with automatic deviation calculation; the data can be collected by cable and transmitted to the control system in real time.
• Measuring data uploaded through serial Modbus-RTU or Ethernet Modbus-TCP.
• Motion limits are protected and the protection threshold is configurable.
• All indicating devices of the horizontal module are battery powered and digital, and the module rides on levelling castors so it is moved to the measuring position.

5. Typical applications

• Post insulator manufacturers – type test and sample test of the shape and position deviations, and routine dimensional inspection before dispatch.
• Electric power companies – incoming inspection of post insulators for substations.
• Electrical testing laboratories – third party verification to GB/T 8287.1 and IEC 60168.
• Switchgear and substation assembly – checking that the fixing holes of the insulator match the stand-off fittings of the structure.

6. Frequently asked questions

1. Which deviations does the platform check?

Parallelism of the end faces, eccentricity (the maximum deviation between the axes of the upper and lower fixing-hole centre circles), camber or straightness of the insulator axis, the shed or umbrella angle, the angular deviation of the fixing holes, the structural height and the shed diameter.

2. Why does a post insulator have to be checked for these deviations?

Because if any of them exceeds the tolerance of IEC 60168 / GB/T 8287.1 Annex A, the insulator cannot be assembled correctly on the structure, the fixing holes will not match the stand-off fittings, and the specified creepage and clearance distances may not be maintained.

3. What is the largest post insulator that can be checked?

The vertical module takes post insulators with a metal fitting flange diameter up to 400 mm and a structural height up to 1000 mm, and both can be customised. The horizontal module takes a fitting flange diameter up to 600 mm, with a structural height measurement of 0 – 1000 mm and a shed diameter measurement of 0 – 500 mm.

4. Is the calculation of the deviations done by hand?

No. The digital dial indicators have a range of 25.4 mm with an accuracy of 0.01 mm and the deviation is calculated automatically. One run acquires the parallelism, eccentricity, camber and shed angle data sets and prints the statistics at the end of the test.

5. Can the measuring data be taken into a quality system?

Yes. The measuring data can be uploaded through serial Modbus-RTU or Ethernet Modbus-TCP, and the data of the dial indicators can be collected by cable and transmitted to the control system in real time.

6. Can the platform be used for disc insulators or composite insulators?

No. A disc insulator unit has its own dimensional check – disc diameter, structural height and axial and radial deviation – which is carried out on a dedicated disc insulator deviation checking device. This platform is built for post insulators.

Related insulator dimensional and mechanical test equipment

Disc insulator units are checked on the deviation checking device for disc insulator units, the ball and socket locking system on the locking pin testing machine for ball and socket couplings, and the mechanical strength of post insulators on the cantilever and torsion testing machine. The complete range is listed under insulator test equipment.