SU942168A1 - Method of testing mine cables for fire-proofness - Google Patents

Description

(54) METHOD FOR TESTING FIRE CABLES FOR FIRE SAFETY

one

The invention relates to electrical engineering and can be used to test cables used in fire hazardous conditions.

There are known methods for testing fire safety, by which an external heat source (flame) is applied to the cable sheath and, according to the results of exposure, the fire safety of the cable l and 2.

The closest in technical essence to the present invention is a method that takes into account the preheating of the cable with current for a regulated time of s .15

A common drawback of the known methods is the fact that the factors affecting the cable under test do not correspond to the actual causes of the fires caused by the cable inoperability.

The purpose of the invention is to increase the reliability of the cable by increasing the objectivity of the control.

This goal is achieved by using the energy of a short arc circuit excited in the cable as a source of additional thermal energy, and the arc action time takes paBHbnvf for the controlled response time of the protective apparatus.

When testing cables designed to power powerful electric motors, an appropriate electric motor is additionally connected to the cable under test.

FIG. 1 is a block diagram for testing fire safety of mine cables; in fig. Figures 2 and 3 are examples of the cross-section of a cable core to augment an arc short-circuited cable. with cuts.

The test facility contains a transformer substation 1, a switching device 2, a circuit breaker 3, plug connectors 4 for connecting a sample of the cable under test, a circuit breaker 5,

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a current adjustment device 6 for on-the-off examinations;

load, switching device 7 dL that fire safety tested

motor connections 8. Cable sizes can be considered satisfactory

On the current, voltage, and response time of the protective equipment, an oscilloscope 9 is recorded. Test cable 10 is notched and the insulation of the 11 phases is peeled before the cores are exposed 12 (Figs. 2 and 3). The revival of the arc short-circuit the wire 13 is produced, the diameter of which is equal to the wire diameter of the test specimen cable. The method is carried out as follows. A test specimen 10 of a cable 5 m long with exposed conductors 12 is connected to plug-in sockets 4 of a test installation. The switching device 2 and the circuit breaker 3 are turned on, a voltage equal to l.OSUn is applied. from the transformer substation 1 to the test sample 10 kabetsh. The current flowing through the cable model heats it up to the maximum allowable temperature of the cores in operation. Moreover, the amount of current is controlled by the device 6, which is connected to the test sample 1O of the cable through an automatic switch 5. The temperature is measured using a thermocouple (not specified). When the established temperature is reached, the arc is produced. 3. By bridging the exposed cores 12 of sample 10 of the cable with a wire 13. At the same time, the response time of the protective equipment is one and a half times the response time of the protective equipment under actual operating conditions. When testing cabs & lems designed to supply electric motors with a power of 1OO kW before forming an arc voltage. 3. To test cable sample 1O, the electric motor 8 is connected using a switching device 7. In this case, an additional factor is realized when the test voltage is disconnected energy account of an electric motor operating during run-in time in generator mode. The fire safety assessment is carried out visually and, in the absence of ignition, the envelope is repeated many times with an increase in the power supply each time.

Claims (3)

in the absence of ignition of the cable sheath after six times of testing with the response time of the protective apparatus in the proposed system of operation. The use of izofeteny allows you to increase the trouble-free operation of electrical power systems in conditions of increased fire hazard. Claim 1; The method of testing mine cables is not fire safe, including preliminary tests by heating 1 ° .... .... operating temperature, the subsequent impact on the cable of additional thermal energy during the regulated exposure time, repeated tests at the pre-heating power levels and evaluation of the results on the condition of the cable sheath after exposure to test factors, that is, in order to increase the reliability of the cable by increasing the objectivity and control, as the source of dszpolnitelnogo thermal energy using energy supplied by the cable of the short arc closure "" "the time of action of the arc is equal to half the time of operation of the protective apparatus. 2. The method according to Claim 1, characterized in that the tests of cables intended for connecting powerful electric motors are carried out with an additional connection of electric motor to the cable to be tested. Sources of information taken into account in the examination 1. GOST 7006-72, paragraph 4.11 , with. 17 2. GDR standard, CLE 0472. 3.Toldobin GD, Ponchik S. X. Test methods for testing fire safety cables. , Ref. Sat Safety, labor and mine rescue, M., 1976, No. 2 (prototype).