By sion932 
With the rapid development of the power industry, the demand for high-voltage power transmission and distribution systems with high reliability and safety is increasingly prominent. As a key national standard in China’s power cable field, GB/T 18890.1-2015 “Power cables with cross-linked polyethylene insulation and their accessories for rated voltage of 220 kV (Um=252 kV)—Part 1: Test methods and requirements” plays a crucial role in regulating the production, testing and application of 220kV cross-linked polyethylene (XLPE) insulated power cables and their accessories. This article aims to elaborate on the core content, technical characteristics and engineering significance of this standard.
1. Overview of GB/T 18890.1-2015
Issued on October 9, 2015 and implemented on May 1, 2016, GB/T 18890.1-2015 is a recommended national standard in China, which replaces the previous guiding technical document GB/Z 18890.1-2002. The upgrade of the standard nature from guiding to recommended reflects its enhanced applicability and authority in the industry, providing clearer and more mandatory technical guidelines for manufacturers, testing institutions and engineering construction units.
This standard is modified based on IEC 62067:2011 “Power cables with extruded insulation and their accessories for rated voltages above 150 kV (Um=170 kV) up to 500 kV (Um=550 kV)—Test methods and requirements”. While aligning with international advanced technical standards, it also combines the actual situation of China’s power industry to ensure that the technical requirements are in line with domestic engineering practice and promote the internationalization of China’s high-voltage power cable technology.
2. Scope of Application
GB/T 18890.1-2015 specifies the test methods and requirements for fixedly installed 220kV (Um=252kV) XLPE insulated power cable systems, cable bodies and their accessory bodies. It is applicable to single-core cables and their accessories used under normal installation and operation conditions. However, it should be noted that this standard is not applicable to cables and their accessories used under special conditions, such as submarine cables. For these special-purpose products, the test methods in this standard may need to be modified or special test conditions may need to be set according to actual application scenarios.
In addition, this standard does not cover transition joints connecting XLPE insulated cables and paper-insulated cables, which need to be regulated by other relevant standards or technical specifications.
3. Core Technical Requirements
3.1 Marking and Characteristics Requirements
To ensure the traceability and testability of products, the standard requires clear marking of cables and their accessories. For cables, the following characteristics shall be clearly defined or stated: manufacturer’s name, model, manufacturing date, rated voltage (U0, U and Um values), conductor type and material, nominal cross-sectional area, insulation material and nominal thickness, shielding layer and metal sheath structure, outer sheath material and thickness, and relevant electrical parameters (such as capacitance, nominal electric field strength, etc.).
For accessories, the marking requirements include the correct marking of the cable used for the test, the conductor connection hardware (installation process, tool requirements, contact surface treatment, type and number, etc.), and the accessory itself (manufacturer’s name, model, manufacturing date, rated voltage, installation manual number and date, etc.).
3.2 Test Conditions
The standard specifies strict test conditions to ensure the accuracy and comparability of test results. Unless otherwise specified for special tests, the test shall be carried out at an ambient temperature of (20±15)℃. For AC test voltage, the frequency shall be 49Hz~61Hz, the waveform shall be basically sinusoidal, and the voltage value shall be expressed by the root mean square (r.m.s.). For the standard lightning impulse test voltage waveform, the front time shall be 1μs~5μs, and the half-peak time shall be (50±10)μs in accordance with relevant national standards. In addition, the test voltage specified in the standard is expressed as a multiple of the rated voltage U0 (127kV for 220kV system), and the specific test voltage value shall be implemented in accordance with the requirements of Table 4 in the standard.
3.3 Key Test Items and Requirements
The standard classifies the tests into routine tests, sampling tests, type tests, pre-qualification tests and post-installation electrical tests according to the purpose and frequency of the tests, covering the whole life cycle of cable products from production to installation.
Routine tests shall be carried out on each manufactured length of cable and each prefabricated accessory, including partial discharge test, voltage test and outer sheath electrical test. For the partial discharge test, the test voltage shall be gradually increased to 1.75U0 and maintained for 10s, then slowly decreased to 1.5U0. Under 1.5U0, there shall be no detectable discharge exceeding the declared sensitivity (10pC for cables and 5pC for accessories). For the voltage test, the power frequency AC voltage of 2.5U0 shall be applied between the conductor and the metal shield/metal sheath and maintained for 30min without insulation breakdown. The outer sheath electrical test shall apply a DC voltage of 25kV between the metal shield/metal sheath and the conductive layer on the outer sheath surface for 1min without breakdown.
Sampling tests are carried out on cable samples representing the delivery batch, including conductor inspection, conductor resistance and metal shield/metal sheath resistance measurement, insulation and outer sheath thickness measurement, XLPE insulation thermal extension test, capacitance measurement, lightning impulse voltage test, water permeability test (when applicable), etc.. The test frequency and sample selection shall be in accordance with the relevant provisions of the standard to ensure the batch quality of products.
Type tests, pre-qualification tests and post-installation electrical tests are mainly used to verify the overall performance of the cable system, the long-term operation stability and the reliability after installation. The test items and procedures are more complex and comprehensive, involving the overall performance assessment of the cable system under various working conditions and the verification of installation quality.
3.4 Water Blocking Measures
For cable systems laid underground, in water-prone underground passages or in water, the standard recommends using a radially impermeable barrier to coat the cable. To prevent the need for replacing long sections of cables in case of water ingress due to cable damage, longitudinal water blocking measures can also be adopted, and the longitudinal water permeability test method is specified in the standard.
4. Engineering Significance and Application Value
As an important technical standard in the field of 220kV XLPE insulated power cables, GB/T 18890.1-2015 has important engineering significance and application value. Firstly, it standardizes the test methods and technical requirements of cables and their accessories, improves the quality and reliability of products, and reduces the failure rate of power cable systems in operation. Secondly, the standard is modified with reference to international standards, which helps to promote the technological progress and internationalization level of China’s power cable industry, and facilitates the exchange and cooperation of domestic manufacturers with the international market.
In addition, the implementation of this standard provides a unified technical basis for engineering design, construction, acceptance and operation and maintenance, ensuring the safe and stable operation of the 220kV power grid. For manufacturers, complying with the standard requirements helps to improve product competitiveness; for power grid operation units, the standard provides a reliable basis for product selection and quality inspection, which is of great significance for ensuring the safe and efficient operation of the power system.
GB/T 18890.1-2015, as a recommended national standard, provides comprehensive and strict technical guidelines for the test and quality control of 220kV XLPE insulated power cables and their accessories. Its implementation not only helps to improve the overall quality level of China’s power cable products, but also plays an important role in promoting the safe and stable operation of the power grid and the healthy development of the power industry. With the continuous progress of power cable technology, it is necessary to pay attention to the update and revision of relevant standards to adapt to the new technical requirements and application scenarios, and continue to promote the modernization and high-quality development of the power industry.