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Requirements for medium voltage cable design?


There are many types of cables in life. According to GB/T2900.10-1984, wires and cables are defined as: wire products used to transmit electric energy, information and realize electromagnetic energy conversion. In order to facilitate the selection and improve the applicability of the products, my country's wire and cable products can be divided into the following five categories according to their uses. The categories include bare wires, winding wires, power cables, communication cables, and wires and cables for electrical equipment.

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Requirements for medium voltage cable design?

There are many types of cables in life. According to GB/T2900.10-1984, wires and cables are defined as: wire products used to transmit electric energy, information and realize electromagnetic energy conversion. In order to facilitate the selection and improve the applicability of the products, my country's wire and cable products can be divided into the following five categories according to their uses. The categories include bare wires, winding wires, power cables, communication cables, and wires and cables for electrical equipment.

                                                   

1. What is a medium voltage cable?

Medium voltage cables have a voltage range between 6 kV and 33kV. They are mostly produced as part of power generation and distribution networks for many applications such as utilities, petrochemical, transportation, wastewater treatment, food processing, commercial and industrial markets.

In general, they are mainly used in systems with a voltage range up to 36kV and play an integral role in power generation and distribution networks.


2. Standards for medium voltage cable design

——IEC 60502-2: The most commonly used medium-voltage cables in the world, with a rated voltage up to 36 kV, a wider range of design and testing, including single-core cables and multi-core cables; armored cables and unarmored cables, two types The armor "belt and wire armor" is included.

- IEC/EN 60754: designed to assess the content of halogen acid gases, and aims to determine the acid gases released when insulation, sheathing, etc. materials are on fire.

- IEC/EN 60332: Measurement of flame propagation throughout the cable length in the event of a fire.

- IEC/EN 61034: specifies the test for determining the smoke density of burning cables under specified conditions.

- BS 6622: Covers cables for rated voltages up to 36 kV. It covers the scope of design and testing, including single core and multi core cables; armored only cables, wire armor only types and PVC sheathed cables.

- BS 7835: Covers cables for rated voltages up to 36 kV. It covers the scope of design and testing, including single-core, multi-core cables, armored cables only, armored only, low-smoke halogen-free cables.

- BS 7870: is a series of very important standards for low and medium voltage polymer insulated cables for use by power generation and distribution companies.

 

3. The structure and material of the cable

Compared with low-voltage cables, medium-voltage cables have different sizes and types, and their manufacturing processes and raw materials determine that their structures are more complex.

In medium voltage cables, the insulation process is quite different from that of low voltage cables, in fact:
- The medium voltage cable consists of three layers instead of one layer: conductor shielding layer, insulating material, insulating shielding layer.
- The medium voltage insulation process is achieved by using CCV lines instead of conventional horizontal extruders.
- Even if the insulation has the same designation as the low voltage cable (e.g. XLPE), the raw material itself is different to ensure a purer insulation. Color masterbatches used for low-voltage cables cannot be used for core identification.
- Metallic screens are commonly used in the construction of medium voltage cables for low voltage cables dedicated to specific applications.

Common failure

Poor quality cables increase failure rates and put the end user's power supply at risk.

The main reasons for this are premature aging of cable infrastructure, poor quality foundation of joints or cable termination systems, resulting in reduced reliability or operational efficiency.

For example, the release of partial discharge energy is a precursor to failure, as it provides evidence that the cable is beginning to deteriorate, which will lead to failure and failure, followed by a power outage.

It is recommended to select high quality cables that have been thoroughly tested to extend their life and predict maintenance or replacement intervals and avoid unnecessary interruptions.