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What should be checked for secondary circuits of HV switchgears?

Mar 08, 2017

Secondary circuit check items for High Voltage Switchgears

secondary circuit check

1. All secondary circuits should be chose according to the bear rated voltage and rated current. Requirements: current circuit and voltage circuit: ≮2.5mm2, weak current part: 1mm2(except special requirements from user).

2. All secondary circuits should be connected with instrument and terminals by lugs which should be tight.

3. Distribution terminals of all secondary circuits should have mark which should be right and clear.

4. Normally, transition terminals are not allowed to be used during secondary wiring. The middle part of guiding lines should not be welded or connected by bolts.

5. Safety measures should be made when secondary guiding lines go through metal plates or components, such as rubber washer.

6. secondary elements check

(1) Secondary elements should be complete, no fault. Nameplates are clear and modes are right. There should be verification marks on meters and metering grades should meet the requirements.

(2) Secondary elements installation should be consistent with drawings.

(3) All secondary elements should have manufacture name, mark, qualification certificate or test reports.

Check and record

7. Secondary circuit connection check

(1) Check electrical connection according to scheme drawing, connecting drawing.

(2) AC circuit should not have short-circuit and grounding; secondary circuit of PT should have fuse and should not be short-circuit; secondary circuit of CT should not be open circuit; AC, DC, strong current and weak current circuits should not be mixed.

(3) Supply regulated voltage, current to circuit and imitate actual working condition and interlock test.

(4) When secondary elements are live, test 2-5 times with lowest acting voltage or current according to technical requirements to test the acting reliability.

(5) Proceed insulation test.

Apply voltage 2000V, and discharge for 1 min without breakdown. Use 500V megger to test insulation and value should be less than 10MΩ.