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TOOLS AND EQUIPMENT USED FOR DC HIGH POT TESTING
- Tools and equipment needed should be in good condition and must be checked by Supervisor / Safety Engineer prior to use in the construction area. These includes but not limited to:
- Boom Truck
- Electrical Hand Tools
- High Voltage Module
- Control Unit
- Ground Leads
- High Voltage Output Cable
- Interconnection Cable
- Kilovoltmeter
- Term Shield Conn.
- All tools utilized in a classified area should be intrinsically safe and suitable for hazardous areas.
METHODS / PROCEDURES FOR DC HIGH POT TESTING
- GENERAL REQUIREMENTS / OVERVIEW
- Only qualified employees are allowed to perform high voltage test or work.
- High voltage cables shall be DC high-potential tested in accordance with SAES-P-104 (It is aramco standard).
- This DC hi-pot testing applies to cable voltage rated 5kV and above. Refer to SAES-P-104 (It is aramco standard).
- Prior to DC hi-pot testing, perform cable continuity and phasing check for each.
- Check the insulation resistance of the cable using 5000 volts DC megger The insulation resistance of each core should be checked to ground and between cores.
- All permanent and consumable materials shall be prepared prior to testing.
- Manpower, equipment, tools, and other logistics shall be prepared and ready for installation.
- Prepare the workplace such as barricading the area and housekeeping.
- Electrically hazardous task plan / permit shall be completed and signed before any work proceeds.
TESTING PROCEDURE FOR DC HIGH POT TEST
- SET-UP INSTRUCTIONS
- Connect the ground terminal and the HV module to a known earth ground.
- Connect the output HV cable to the HV output connector located on the HV module. The exposed shield connection on the HV output cable is at guard potential and must not be grounded.
- The external interlock plug must be wired to an external interlock switch or shorted with a jumper. (Pins 1 & 3 of interlock plug).
- With Main Breaker off, plug Input cord into control panel receptacle and into grounded outlet.
- Identify the HV terminal and the ground terminal of the specimen to be tested. Connect the ground terminal to the Ground post of the HV module. Attach the spring clip of the HV cable to the HV terminal of the specimen.
- When commencing high pot test, removed first the cover of HV chamber then disconnect the lead wire to the HV bushing of transformer and connect it to the test bushing socket of the high pot test terminal.
- Oil filling for the HV cable chamber shall be done to make sure that no contact of lead wire to HV bushing will occur before the high pot testing start.
- After the high pot test is done, oil shall be drain out of the HV chamber and return the lead wire connection to HV bushing of transformer.
- And after the test bushing is taken out from the HV chamber, fill the chamber again with oil and ensure the hole is firmly blocked with cover.
NOTE: The HV termination of the HV cable must be safely separated from grounded objects. Proximity to grounded objects may cause excessive leakage or flashover.
Connection Diagram
CABLE TESTING
- Switch the MAIN BREAKER ON of the test equipment. The AC ON lamp will light.
- Close external interlock switch, if used.
- Push the HV ON pushbutton. The HV ON lamp will light. The VOLTAGE CONTROL must be at 0 (RESET) for the HV ON pushbutton to operate.
CAUTION: The unit is now capable of producing high voltage at the output.
- Advance the VOLTAGE CONTROL slowly until the desired test voltage is read on the OUTPUT VOLTAGE kilo-volt meter.
- Maintain the test voltage for 15 minutes. The OUTPUT CURRENT meter indicates the leakage current of the specimen under test. Select appropriate current range. See manufacturer’s instruction manual for notes on interpretation of current readings.
NOTE: Refer to SATR-P-3214 and SATR-P-3218 (These are test repot for more detailed Test Results Acceptance Criteria.
- After maintaining test voltage for 15 minutes, turn the VOLTAGE CONTROL, slowly, in the counterclockwise direction to 0 (RESET).
- Press the HV OFF pushbutton, or open the external interlock switch.
- Allow sufficient time for the specimen charge to bleed off, which is indicated when the kilo-volt meter reading returns to zero.
- Switch MAIN BREAKER off.
WARNING: The specimen under test may retain a lethal electrical charge even when the test set is turned off. The specimen must be discharged with a properly grounded grounding stick. Keep the HV terminal of the specimen and the test set’s output cable grounded at all times except when actually performing tests. Do not approach the HV module until ground bonds have been applied.
- Results shall be filed and recorded on applicable test form per approved SATIP (Typical plan).
HV SHIELDED CABLE
- Check the voltage rating of the cable and select the test voltage which one wants to supply for examination, refer to Table 3 of SAES- P-104 for DC High Potential Field Test Voltage.
- Start the high potential test equipment.
- The test voltage shown on Table 3 of SAES-P-104 shall be reached in equal voltage and time increments. Each increase shall be made
- Divide the test voltage rating by 5 (means 5 steps), apply the voltage slowly in a minimum of five increments until the maximum test voltage is reached.
- After each voltage increase, the leakage current shall be allowed to If the time intervals chosen are on insufficient duration to stabilize the current, the cable shall be discharged and the test repeated with new time intervals of greater, but still equal duration.
- Record the stabilized leakage current, in micro ampere, at the end of each time intervals.
- Allow the voltage to remain constant at the full test voltage and record the leakage current at 15, 30, and 45 seconds and at one minute intervals thereafter for 15 minutes for shielded cable. Compute the cable resistance using Ohm’s Law; R=V/I, where R=Resistance of Cable, V=Voltage injected, and I=Leakage current recorded.
NOTE: Plot the test voltage vs. leakage current on graph paper as the test progresses. The step voltage slope should be reasonable linear for the graphic plots.
Please check aslo: ELECTRICAL FIELD TEST AND INSPECTION PROCEDURES OF SWITCHGEAR GENETRAL