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Ultra high voltage single core cable selection and application

2 months ago 99 0 News

The sheath protector is generally installed in the cable line cross-connect box and in the grounding protection box.

1, the role of the protective layer protector

1) Limit the power frequency induced voltage in the metal sheath of the cable line

——When the cable line is in normal working condition, the high voltage cable sheath protector exhibits a high resistance state, and the power frequency induced current loop in the metal sheath of the cable is cut off.

2)Rapidly reduce the power frequency and shock overvoltage in the metal sheath of the cable line

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——When a ground fault occurs in the cable line, lightning overvoltage or internal overvoltage causes a high overvoltage in the metal sheath, the sheath protector exhibits a low resistance conduction state, so that the fault current quickly rushes into the earth through the protector. .

2, the choice of protective layer protector

1) The residual voltage under the action of the maximum inrush current shall not be greater than the value of the voltage withstand voltage of the cable sheath divided by 1.4 (included in the insulation coordination factor).

2) The maximum power frequency overvoltage may be tolerated, not broken down or damaged under the action of 5s.

3) After the maximum inrush current may be accumulated for 20 times, the protector shall not be damaged.

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3, the performance of the sheath protector

The common labor ratio K is the protection performance of the sheath protector:

Selection and application of high voltage single core power cable sheath protector

The smaller the residual ratio of the protector than K, the better the protection performance.

4. Regular inspection and maintenance of the sheath protector

Periodically measure the DC reference voltage of the cable sheath protector at 1 mA and the leakage current at 0.75 times the reference voltage, especially after system failure.

Selection and application of high voltage single core power cable sheath protector

It can be tested by the cable sheath overvoltage protector characteristic parameter tester.


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