Insulator Deviation Checking Device (Axial & Radial Deviation Tester) for Disc Ceramic & Glass Insulators

Insulator deviation checking device at a glance

• Purpose: the dimensional check of disc type ceramic and glass insulator units — disc diameter, structural height, axial deviation and radial deviation — on one device.
• Standard: IEC 60383-1, Clause 17 (verification of the dimensions) and Clause 22 (verification of the axial, radial and angular displacements); GB/T 1001.1-2003.
• Why it is needed: if the shed diameter, the structural height or the deviations are outside the limits of the standard, the unit cannot be assembled into a string and cannot be accepted.
• Measuring range: axial and radial deviation 0 – 25.4 mm, measuring accuracy 0.01 mm, deviation checking capacity not less than 5 mm.
• Specimens: disc units of 70, 160, 210, 300, 420 and 550 kN — coupling sizes 16, 20, 24, 28, 32 and 36; shed diameter up to 500 mm, structural height device range not less than 400 mm.
• Practical point: light and mobile, and the measuring device needs no mains supply, so it is taken to the samples instead of the samples being carried to it.

1. What this device is used for

The dimensional check is one of the basic sample and routine tests on a string insulator unit. The diameter of the shed, the structural height of the unit and the axial and radial deviation of the unit all have to be inside the limits given by the standard — otherwise the unit cannot be assembled into a string and cannot be accepted.

The CT-AD26 carries out this check on one fixture. It measures the disc (shed) diameter, the structural height, and the axial and radial deviation of the unit, and the reading is taken from a digital display, so the result is direct and accurate and can be zeroed at any specified position. For the axial and radial deviation the device works out the maximum deviation and the minimum deviation automatically, so there is no tedious manual calculation.

The device is used by manufacturers of disc insulators, by power utilities and by electrical laboratories, for the incoming inspection of purchased units and for the dimensional check in type and routine tests.

2. Standards applied

• IEC 60383-1 – Insulators for overhead lines with a nominal voltage above 1000 V – Part 1: Ceramic or glass insulator units for a.c. systems – Definitions, test methods and acceptance criteria. Clause 17 – Verification of the dimensions; Clause 22 – Verification of the axial, radial and angular displacements.
• GB/T 1001.1-2003 – Insulators for overhead lines with a nominal voltage above 1000 V – Part 1: Ceramic or glass insulator units for a.c. systems – Definitions, test methods and acceptance criteria.
• Inspection guide for power grid materials (2017 edition) – Chapter 25: Disc type ceramic and glass insulators, dimensional check, class C.

3. Technical parameters

The measuring device is of the high accuracy digital display type and needs no external power supply, so the device can be taken to where the samples are.

4. Key functions

• Measures the disc (shed) diameter, the structural height, the axial deviation and the radial deviation of one disc insulator unit on a single fixture.
• Digital display of high accuracy: the reading is direct and accurate, and can be zeroed at any specified position.
• The maximum deviation and the minimum deviation are calculated automatically by the device – no manual calculation.
• Pre-tensioning mechanism and lifting device hold the unit in the measuring position; a protection guard protects the operator.
• Industrial aluminium profile frame, welded, drilled and milled parts, precision linear bearings and a mini hand wheel with a high accuracy linear guide.
• Light and mobile, and no mains supply needed for the measuring device.

5. Typical applications

• Disc insulator manufacturers – dimensional check as a sample and routine test, and final inspection before dispatch.
• Power utilities – incoming inspection of purchased disc units.
• Electrical testing laboratories – dimensional verification within type test programmes and third party inspection.
• Grid material inspection – the class C dimensional check of the inspection guide for power grid materials.

6. Frequently asked questions

1. Which deviations does the device measure?

It measures the axial deviation and the radial deviation of the disc insulator unit, together with the disc (shed) diameter and the structural height. The deviation measuring range is 0 to 25.4 mm with an accuracy of 0.01 mm, and the maximum deviation and the minimum deviation are calculated by the device automatically.

2. Which insulator units fit on the device?

Disc type ceramic and glass units of 70 kN, 160 kN, 210 kN, 300 kN, 420 kN and 550 kN, that is coupling sizes 16, 20, 24, 28, 32 and 36, one single unit at a time. The shed diameter can be up to 500 mm and the structural height device covers not less than 400 mm.

3. Does the device need a power supply?

No. The measuring device is of the digital display type and needs no external power supply, which is why the device is light enough to be moved around and can be taken to where the samples are.

4. Which standard clause does the check come from?

IEC 60383-1, Clause 17 for the verification of the dimensions and Clause 22 for the verification of the axial, radial and angular displacements. The corresponding Chinese standard is GB/T 1001.1-2003, and the dimensional check also appears as a class C item in Chapter 25 of the inspection guide for power grid materials (2017 edition).

5. Is the calculation of the deviation done by hand?

No. The device works out the maximum deviation and the minimum deviation automatically, so the result is read directly from the digital display without manual calculation.

6. Can the device be used for post insulators?

No. Post insulators have their own shape and position deviation check – parallelism, eccentricity, camber, shed angle and the angular deviation of the fixing holes – which is carried out on a dedicated post insulator inspection platform.

Related insulator inspection equipment

The locking system of the same coupling is verified on the locking pin testing machine for ball and socket couplings, post insulators are checked on the post insulator deviation inspection platform, and the routine mechanical test is run on the routine tensile testing machine for disc insulators. The complete range is listed under insulator test equipment.