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Loop resistance measurement phase is zero

time:2020/8/15   source:华天电力  reading:353 time

The zero-phase circuit (zero-phase loop) is a circuit formed when the phase line and the neutral line are connected. The measurement frequency of the zero-phase loop of the continuity characteristics of the protective conductor and the protective device in the electrical equipment is once every three years, and As part of the acceptance work, the reconstructed object and the new object are measured. According to regulations, the zero-phase measurement includes measuring the resistance of all lines of electrical equipment and calculating the short-circuit currents of all phases of the line.

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Calculate the operating current range of the machine under short-circuit conditions based on these data:

Machine type

The time to install the electromagnetic release,

Rated thermal expansion current,

Allowable shutdown time.

The time current parameter is used to calculate the expected response time of the automatic protection device.

Through the analysis of this table in the test report, the quality of electrical installation work, the quality of installed electrical equipment and switchgear, cables and wires can be determined; it can also be determined whether the protective measures are taken in the event of a short circuit in the circuit breaker Can work in time.

If the value of this parameter is too high when measuring the resistance of the zero-phase circuit, so that the calculated short-circuit current is close to the value of the response current of the electromagnetic release, the response time of the circuit breaker may be longer than the allowable time. The increase in the zero-phase loop resistance value indicates the need to check the quality of all circuit connections, the condition of cables and wires, and connected equipment and equipment. If the situation has not changed after performing the above work. It may be necessary to replace the automatic protection device with another automatic protection device with higher current characteristics, or change the electrical items of the line (divide the line into two or more branches or use an automatic protection device with a lower rating) Device).

The work result of the loop resistance tester measuring the zero phase makes it possible to evaluate the correct selection of protective automatic equipment and the quality of electrical connections in electrical installations, thereby reducing the risk of electric shock to personnel, the possibility of fire caused by short-circuiting of electrical components, and damage to electrical equipment The risk is minimized.

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