What tests are there in electrical engineering. Testing of electrical installations and protective equipment. Laboratory tests and measurements in electrical installations

Electricity has become so densely embedded in our daily life that many people notice electricity only in its absence. In order for electricity to continue to be so invisible, careful and responsible work of laboratory specialists who are engaged in testing and measurements in electrical installations of consumers is necessary.

What are electrical laboratories for?

Electrical laboratories are needed not only to carry out tests of electrical installations, such a laboratory is capable of replacing almost all services of electrical networks. To ensure a safe and uninterrupted power supply, it is necessary to periodically inspect the electrical installation and the electrical network.

One of the main functions of the electrical laboratory is to carry out test checks for the performance of grounding and protective devices. In addition, the duties of the laboratory staff include checking cable lines for detecting unauthorized connections, insulation breakdown, etc.

The electrical laboratory can test both a certain type of electrical installation and all electrical equipment. Also, the electrical laboratory checks the performance of protection devices, the condition and electrical safety of tools, as well as protection against electric shock.

The need for electrical measurements

Some people think that performing tests of electrical installations and a complex of electrical measurements is a useless and meaningless exercise, and for customers it is an additional and waste of money. But it is not worth drawing such conclusions. Let's see why electrical measurements are needed, which are carried out by laboratories.

Various electrical installations and equipment are involved in the operation of the power supply system, which, due to continuous operation and long-term operation, are prone to breakdowns. In this case, the electrical laboratory is irreplaceable. Specialists of such laboratories carry out diagnostics by means of electrical measurements and, thanks to this, identify the causes of breakdowns in electrical installations.

The trouble-free operation of the electrical system requires periodic attention, which can be provided by an electrical measuring laboratory through testing and measurement. The electrical system consists of many components, each of which needs preventive maintenance. It should be remembered that only an electrical laboratory can qualitatively perform a complex of electrical measurements, eliminate all malfunctions that can lead to emergency situations, human casualties.

It is necessary to carry out tests of electrical installations in order to determine their suitability for further use, as well as to detect and eliminate defects in work. Test performance should not be lower than required, approved by the state standard.

If you previously doubted the need for electrical measurements, then we think that now these doubts have disappeared.

Types of tests

Acceptance tests carried out during commissioning of equipment after installation or repair at the installation site. For electrical installations, they consist in setting up electrical equipment. Industrial production is distinguished by a variety of electrical installations, which use modern automated electric drives with control stations, transformer substations, overhead and cable power lines, etc. Therefore, the scope and norms of acceptance tests provide for the necessary checks, measurements and tests for various types of electrical equipment that make up electrical installations, and determine the main criteria for the suitability of electrical equipment for operation.

These criteria can be divided into two types: absolute and relative.

Absolute the criteria clearly define the signs during verification and the values ​​of physical quantities during measurements or tests, by which it is possible to judge the suitability (or unsuitability) of the tested electrical equipment for operation.

The standards also provide absolute criteria for the state of insulation, contact connections, permissible temperatures of live parts and windings of electrical machines and apparatus, timing characteristics of switches, etc.

Relative The criteria for the condition of the equipment under test are based on a comparison of the measurement data of some electrical quantities during commissioning tests with the measurement data of the same values ​​obtained earlier, for example, during factory tests or on the basis of comparison of measurement data performed during commissioning on the same type of equipment.

Such criteria often have to be used when analyzing the characteristics of electrical machines, transformers, as well as when measuring insulation resistance.

The final conclusion on the possibility of putting the electrical installation into operation is given on the basis of its comprehensive testing in operation. When carrying out these tests, it is possible to timely identify and repair the weakened parts of electrical equipment.

Preventive tests perform during the operation of electrical equipment according to the PPR schedule. Their volume and frequency are established by local instructions, depending on the conditions and mode of operation of the electrical equipment. Regular preventive tests prevent the occurrence of sudden damage and thus prevent possible interruptions in the continuity of the power supply. Thanks to the introduction of preventive tests, the accident rate of electrical equipment has been sharply reduced. Preventive tests allow you to more fully assess the condition of electrical equipment and its main elements: mechanical part, magnetic system, live parts with their contact connections and insulation.

Rejection tests - this is a fault detection of electrical equipment before repair.

Operational tests, or interoperational control (IOC), carried out in the process of repairing electrical equipment.

Control tests performed after repair, regardless of its volume. The purpose of these tests is to establish the compliance of the technical data of electrical equipment and automation equipment produced after repair, passport data, technical conditions for repair, standards, etc.

Type tests are carried out with changes in design, materials or manufacturing technology, if these changes can affect the characteristics of the machine and the transformer, and, as a rule, include verification of the relevant parameters according to the acceptance test program.

These tests are intended to establish whether the actual data characterizing the design of the machine is consistent with the data that was laid down in the design or obtained as a result of experimental design studies.

Inspection, testing and adjustment of electrical equipment.

General information. Before carrying out measurements related to the adjustment or testing of devices, a set of preparatory measures must be performed:

thorough examination of the tested object in order to identify and eliminate defects;

study of the electrical circuit and the establishment of standards for test voltages and currents

drawing up a measurement scheme with an indication of the required devices, their class, measurement limit, permissible insulation resistance, etc .;

ensuring the necessary conditions for measurement (temperature, humidity, surface cleanliness, lighting, etc.) and safe work;

preparation of the workplace and the necessary equipment in accordance with the measurement scheme.

When making high voltage measurements, special attention must be paid to the quality of the equipment connection to the ground loop, checking it visually or using an ohmmeter.

All work should be carried out in strict compliance with safety regulations.

Choice of instruments. Measuring devices, depending on their purpose, area of ​​application and working conditions, should be selected according to the following basic principles:

there must be a possibility of measuring the investigated physical quantity;

the measuring range of the device should cover all possible values ​​of the measured quantity. With a large range of changes in the latter, it is advisable to use multi-range devices;

the device must provide the required measurement accuracy. Therefore, you should pay attention not only to the class of the selected device, but also to factors affecting the additional measurement error (non-sinusoidal currents and voltages, deviation of the device position when it is installed in a position other than normal, influence external magnetic and electric fields, etc.);

when carrying out some measurements, an important role is played by the efficiency (consumption) of the measuring device, its weight, hectares, the location of the controls, the uniformity of the scale, the ability to read the readings directly on the scale, speed, etc .;

connecting the device should not significantly affect the operation of the device under study, therefore, when choosing devices, their internal resistance should be taken into account. When the measuring device is connected to matched circuits, the input or output resistances must be of the required nominal value;

the device must meet the general technical requirements of safety engineering in the production of measurements, established (GOST 22261-76), as well as technical conditions or private standards;

it is not allowed to use devices: with obvious defects in the measuring system, housing, etc .; with expired verification period; non-standard or not certified by the departmental metrological service; not corresponding to the insulation class to the voltages to which the device is connected.

Determination of the measurement error. The deviation of the measurement result from the true value of the measured value is called the measurement error.

The error inherent in a measuring instrument under normal conditions of use (GOST 22261-76) is the main one. If one of the influencing quantities deviates beyond the limits established for the normal value or the area of ​​normal values, additional errors appear. The limits of permissible basic and additional errors of measuring instruments are established in the form of absolute, reduced, relative errors or in the form of a certain number of divisions.

The absolute measurement error Δ is expressed in units of the measured value and is defined as the difference between the measured Xmeas. and the true values ​​of the measured value X, that is, Δ = Xmeas. - X.

Due to the fact that the true value of the measured quantity is unknown, in practice, they use the actual value of the quantity, found experimentally and as close as possible to the true value.

The measurement quality is most fully characterized by the relative measurement error δ, equal to the ratio of the absolute measurement error to the true (real) value of the measured quantity, X:

For a comparative assessment of the accuracy of arrow devices, they use the concept of the reduced error of the device γ,% - the ratio of the absolute error to the limiting value of the scale:

The value of Хк is taken equal to: the final value of the scale - for devices with a one-sided scale; the sum of the end values ​​of the instrument scale - for instruments with a double-sided scale; the difference between the final and initial values ​​of the range - for devices with a zero-left scale; the length of the scale if the scale has sharply tapering divisions.

Means of measurement, the limits of permissible errors of which are expressed in the form of relative or reduced errors, (according to GOST 13600-68) are assigned accuracy classes selected from a number of numbers (1; 1.5; 2; 2.5; 3 ; 4; 5; 6).

For dial gauges, the accuracy class determines the maximum permissible value of the basic reduced measurement error. Knowing the accuracy class of the device, it is possible to determine the limit of the relative measurement error:

Often the value of the desired value A is determined indirectly from the results of several measurements associated with the desired value by known dependencies. In this case, the relative error is determined as follows:

δ l = (| А δа | + | В δв | + | С δс | + ..-) / Л, where δ а, δв, δс - relative errors of measurement of quantities В, С, В;

TYPES OF TESTS OF ELECTRICAL EQUIPMENT.

During installation and after its completion, as well as in operating conditions, electrical equipment of electrical installations is checked, tested and adjusted.
Electrical equipment can be damaged during transportation and installation. During operation, it may be damaged due to natural wear and tear, as well as structural defects.
Regulated requirements are imposed on the adjustment of electrical equipment, for compliance with which the following tests are carried out:
typical in accordance with the current GOST;
acceptance in accordance with the PUE, and in some cases with the instructions of the Ministry of Energy;
preventive and others in accordance with the Rules for the Technical Operation of Power Plants and Networks (PTE), the scope and standards for testing electrical equipment and instructions for individual elements of electrical equipment.
Typical tests are carried out at manufacturing plants according to programs and with volumes specified in standards and technical conditions, but they can be partially carried out at the installation site of electrical installations. In type tests, the compliance of electrical equipment with the requirements imposed on it by standards is checked.
Acceptance tests are carried out in newly constructed and reconstructed installations up to 500 kV. During the tests, the conformity of the mounted equipment to the project is revealed, the necessary characteristics are taken and a certain amount of measurements is performed. After considering the test results, a conclusion is made on the suitability of the equipment for operation.
Preventive tests are carried out during the operation of the equipment, which makes it possible to expand the possibilities of detecting defects in order to timely repair or replace equipment.

Purpose of testing electrical equipment- verification of compliance with the required
technical features, establishing the absence of flaws, obtaining
initial data for the next preventive tests, also a study
equipment operation. There are the following types of tests: 1) typical; 2)
control; 3) acceptance certificates; 4) operational; 5) special.

Typical tests of new equipment different from the existing
design, materials or technological process adopted at its
manufacture, produced by the manufacturer in order to verify compliance
all the requirements for equipment of this type by standards or
technical criteria.

Control tests every product (machine, apparatus, device and
etc.) upon release from the manufacturer to verify the conformity of the
products to the main technical requirements. Control tests are performed according to
reduced (in comparison with type tests) program.

Acceptance tests exposed after installation all over again
equipment put into operation to assess its suitability for operation.

Equipment in operation, including those that have been out of repair,
exposed operational tests, the purpose of which is to check it
serviceability. Operational tests are tests' under serious and current
repairs and preventive tests not related to the removal of equipment in
repair.

Special tests are carried out for research and other purposes for
special programs.

Programs (also norms and methods) of type and control tests
installed by GOSTs for the corresponding equipment. Volume and norms
acceptance tests are determined by the "Rules for the construction of electrical installations".
Performance tests are carried out in accordance with the "Test Standards
electrical equipment "and" Rules for the technical operation of electrical installations
consumers ". In the process of acceptance and operational tests
it is necessary to additionally take into account the requirements of industrial and departmental
instructions.

A certain part of the test work is common when setting up different
parts of electrical installations. Such works include checking circuits
electronic connections, checking and testing of insulation, etc.

Checking electronic circuit diagrams

Checking electronic circuit diagrams predicts:

1) familiarization with the design switching schemes as principle
(complete) and editing, as well as a cable magazine;

2) checking the compliance of the installed equipment and apparatus with the project;

3) inspection and verification of the conformity of the assembled wires and cables (brands,
material, section, etc.) to the project and current rules;

4) checking the presence and correctness of the marking on the ends of wires and cores
cables, terminal blocks, device outputs;

5) checking the installation properties (reliability of contact connections, laying
wires on panels, cable routing, etc.);

6) checking the correctness of the circuit installation (continuity);

7) checking the circuits of electronic circuits under voltage.

The primary and secondary switching circuits are inspected in full when
acceptance tests after completion of the installation of the electrical installation. At
In preventive testing, the scope of switching testing is significantly reduced.
Installation errors or other deviations from
the project is saved by adjusters or installers (depending on the volume and disposition
work). Basic configurations and deviations from the project are only permissible
after agreeing them with the design organization. All configurations must be
shown in the drawings.