Insulation Measurement

Measurement of Insulation

Damage due to surges in electronic equipment (computers, tv., Video, etc..) Facilities have been increasing for years. This is due to the use of electronics increasingly sensitive to these surges.

In particular, computer systems can suffer serious damage or even be destroyed if they are adequately protected. The cost of these defects produced in the own aircraft or installation, is necessary to add the extra costs due to lack of service for days.

Causes of transient overvoltages

Causes a power surge caused are varied, but all can be included in the 4 groups described below:

-Direct impact of the beam, in which case it directly reaches the building, making the installation drivers are subjected to short periods of time at very high potential to cause instant destruction of electronic equipment connected to the facility.

-Impact far, cases in which the building has not been hit directly by lightning, despite which the system operation is affected due to the blast wave that is transmitted through power lines network power.

-Impacts clouds, cases in which the beam bounces from cloud to cloud. The electrical system may be affected due to the costs involved in cooling the atmosphere and cause this phenomenon increases the potential for drivers, especially if they come from outside the building.

-Switching processes, such as startup and shutdown operations, earth accidental switching of inductive or capacitive, etc.. they do that, as in the three previous cases surge risk exposures that crash in the normal functioning of the equipment.

TEST SET

High voltage facilities built according to standards DIN VDE 0100 series have to undergo the tests prescribed in this rule, part 610, when installed, altered or extended. These tests include not only the various measurements to check the operation of the measures of protection and bonding, but also apply to test the insulation resistance.

These tests should be performed when commissioning the installation and repeated later, modifications, repairs or extensions to an electrical installation. The installer must demonstrate that the facility meets the requirements regarding protection of humans, animals and electronic equipment [1]. Let us see what weight is to measure the insulation resistance within the mandatory testing and the extent to which consumer installations connected or surge protection can distort the test results.

In general, the measurement of insulation, the owner or user of the system collects data on the security status of the installation. If the resistance is very low the wires are subjected to excessive loads that can become the focus of a fire. It was just this fact that caused the insurance companies impose periodic measurements of insulation for electrical installations. But what does a low insulation resistance and how can we detect it?. Also here the standard (DIN VDE 0100 part 610) is very explicit. Table 1 shows the measured voltages to be applied and permitted insulation resistance.

As shown in this table, in facilities with a rated voltage of 230/400 V Insulation measurement is performed with a voltage of 500V. The resistance between the points described below must be greater than 0.5 MW, considering that the current measure excludes interference connected with the capacity of the cables.

The measuring device shall also comply, of course, the requirements of DIN VDE 0413, part 1. Now it is important to know between which drivers has to be measured. Again we find the answer in the standard, which establishes the following points:

a) between the active phases (L1, L2, L3) and the protective conductor (PE).

b) between the neutral (N) and the protective conductor (PE).

c) between the active phases (L1, L2, L3).

The insulation resistance must be done without network connection, but the facility can stay connected when consumers are reached values ​​set out in the table above. Otherwise you have to disconnect the network consuming facilities to carry out the test. However it should check whether the circuit under test are connected to electrical devices or sensitive electronic components that may be affected by stress test

Table to apply measuring voltages and resistances allowed. Nominal voltage of circuit test voltage V minimum value of insulation resistance or protection circuits MW of reduced control voltage 250 Rated 0.25 less than 500 V, if it is not protective circuitry or reduced control voltage 500 0, 5Tensión rated greater than 500 V 1000 1.0

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