Any type of cable has inherent characteristics only. One of the main electrical parameters is insulation resistance.
Insulation resistance norms are information that is the basis of all construction, operational and maintenance work.
Since the design of each cable assumes the presence of two metal wires, they are always under the influence of various environmental factors. This effect, if improperly used, can lead to their complete failure and reduce this parameter, such as resistance.
In addition, in the absence of isolation a significant amount of energy is lost and, as a result, can result in additional expenses.
- 1 Assortment of cable products
- 2 Conductor insulation
- 3 Insulating materials
- 4 Technical certificate
- 5 Climatic conditions
Assortment of cable products
At the moment, manufacturers offer a large number of a wide variety of cables. Some common are:
- Communication cables
- Cables for general use
- Power cables
- Control cables
- Distribution cables
Each of the above products is distinguished by its technical characteristics, unique design, functions. Resistance can also have different levels. For the production of a certain type of cable, its technology is used, due to the area of its use.
In order to minimize the risk of failure of any type of cable, it is necessary to insulate its conductive wires. To do this, apply dielectric material, which has the property to prevent the passage of electric current and its resistance.
Insulating shells are made from such raw materials as rubber, plastic and paper. It can be used as one of these materials, and several at once in various combinations. Each manufacturer uses its own materials and insulating covers for each type of its products. Currently on the market you can find a cable with insulation for absolutely any purpose.
From the purpose of the cable depends on the type of materialfrom which insulation will be made. For example, rubber is used as an insulating material when using cable products at high temperatures. It is this material that is least exposed to the negative effects of high temperature than all other currently existing ones.
By means of insulation, the conductor wires of the cables are reliably protected from external and internal negative factors. Insulating materials help minimize energy losses and the risk of melting and fire.
In addition, the probability of a short circuit when working with insulation is almost zero. The isolation rate is an indicator equal to current resistance in the system between the structural elements and the source of its power.
Dielectric, which is used to create an insulating coating, after a certain period time loses its original properties, decreases the resistance of the material, as a result comes in worthlessness Therefore, it is necessary to regularly check whether the properties of the insulating material have changed.
For this purpose, each manufacturer set a special rulewhich is on the product. Norm of resistance of insulation The indicator of resistance of an insulating material to direct voltage refers to the list of main indicators of cable products.
This value is determined and indicated by the manufacturer. The necessary information can be found in the technical documentation, instruction manual or in the state standardization system.
When sending cables for sale, the manufacturer must enclose the relevant documentwhich will contain all the necessary information. It should be noted that to use in practice information on such an important parameter as resistance, which are indicated in the technical documentation, must be correlated with its total length.
In that case, if the size of the cable size exceeds 1000 meters, then the resistance rate specified in the data sheet should be divided by this number. If less, then multiply by the cable length. The resulting mathematical calculations data can be used to assess the cable line.
It should be noted that in the implementation of the measurement work of cable lines can not be ignored weather conditions in which the work is carried out. This factor has a very serious impact on the results obtained.
In the overwhelming majority of cases, in the technical passport of cable products, standards for air temperature are specified, equal to 20 degrees. For this reason, in addition to the air temperature indicator, it is also necessary to take into account its humidity. For example, in case of rain, the result obtained may be an order of magnitude lower than the actual one.
To determine the exact data, it is necessary to dry the surface on which the terminals are located. Some cable types may also have a standard insulation resistance between the sheath and the ground. In order to apply this value for practical purposes, it must also be correlated with the size of the cable. For power cables The following standards are established:
- If the voltage value is less than 1000 V, the insulation resistance is less than 10 MΩ or is not normalized at all.
- In systems with voltages above 1000 V, the insulation resistance index should not be less than 0.5 MΩ.
For the uninterrupted functioning of the control variety of cable products, the level of insulation resistance must be at least 0.5 MΩ.