Field Situation #2 - Identification of cables in Metropolitan Network power systems.
Field Situation #1: Identify and phase a lead covered underground cable circuit|
To Identify and Phase the cable circuit:
1. De-energize and ground the circuit at both ends.
2. At one end of the circuit, install the IPD transmitter. Attach the RED transmitter clip on the "A" phase conductor and attach the YELLOW clip on "B" phase conductor and then remove the grounds at that end of the circuit from all three phases.
3. Turn the IPD transmitter on. The amber lamp will begin to pulse.
4. At the identifying location, connect the clamp-on to the detector.
5. On three conductor cable circuits, lay the clamp-on against the cable sheath to identify the pulsing signal. Adjust the sensitivity control knob to the maximum. Once the signal is detected on the cable mark the cable to identify it as the cable to be worked on. Return to the transmitter, disconnect it and reground the circuit. Using a suitable cable spear, penetrate the cable sheath to the conductor. This is the final test of a de-energized cable. Remove the lead sheath and binder tapes from the cable and spread the conductors. Return to the transmitter and reattach the RED and YELLOW clips to the "A" and "B" phases, remove the grounds and turn the transmitter on. Positively establish the direction of the incoming signal and place the clamp-on around each conductor in the circuit keeping the identified side of the clamp-on facing the direction of the IPD transmitter. Mark the "A" and "B" phase conductors. You can identify "C" phase conductor by changing the RED clip from "A" phase to "C" phase at the transmitter and the YELLOW clip stays on the "B" phase conductor. This will put a RED signal on "C" phase in the circuit. Remove the grounds and turn the IPD transmitter on. Mark the "C" phase cable. Return to the transmitter, disconnect it and reground the circuit. On three conductor cable circuits if there is any question about the direction of the incoming signal, you can correctly identify phases using a grounding harness at the work location. Expose an inch of each conductor to be phased. Connect a grounding harness to each exposed cable conductor and to ground. Place the clamp-on around each of the grounding harness leads, with the clamp-on label facing toward the conductors being phased. Mark each conductor phase for later use.
9. Turn the IPD transmitter off and re-ground the circuit.
10. Before re-energizing, use the IPD to check the phases to be sure that no one crossed phases in a reconstructed splice or switch. At the IPD transmitter location, remove the grounds and turn the instrument on. Proof phases at each available terminating location to assure the phases are correct, remove the IPD transmitter and grounds and re-energize the circuit.
Field Situation 2: Identification of cables in Metropolitan network power systems. A typical example would be the need to connect a new transformer to an existing network system.
1. Identify the cable phases from the new transformer to the cable ends at the splice location.
2. Identify and phase the existing three-phase cable circuit.
Procedure 1: Identify phases of the new cable ends.
1. The new cable from the new transformer will be phased and marked at both ends. Ground the conductors at the splicing location using a grounding harness.
2. The IPD transmitter is connected at the new transformer. Establish and mark the phases then connect the IPD transmitter. The RED clip goes on the "A" phase conductor and the YELLOW clip goes on the "B" phase conductor. Switch the IPD transmitter on and the YELLOW lamp should begin flashing.
3. Return to the splicing location to phase and mark the new cable conductors. Remove the transmitter at the new transformer and replace the grounds.
Procedure 2: Identify and phase the existing three-phase cable circuit.
1. The network feeder is de-energized and tested at the station, to be sure that all network protectors had opened and that there is no back-feed to the station. After de-energizing and testing, ground the terminations at the station.
2. At one of the network transformers, just beyond the splicing vault, ground a network transformer.
3. Install the IPD transmitter at the station. The RED clip goes on the "A" phase conductor and the YELLOW clip goes on the "B" phase conductor. Remove the grounds and turn the IPD transmitter on. The transmitter should begin to impulse into the feeder cable circuit due to the grounds at the grounded network transformer.
4. Identify and phase the cable as described in Field Situation 1. Afterward, at the station, turn the IPD transmitter off and replace the grounds.
5. Splicing operations can now begin between grounds. One at the station and one at the network transformer beyond the splicing location and also at the new transformer. Some power companies may have policies that also ground another transformer closer to the splicing area to insure closer grounding protection.
6. When the splice is started and the conductors have been joined permanently, but before insulating, recheck the phases. Electrically separate the spliced conductors, and at the station, remove the grounds and turn the IPD transmitter on. Use the IPD detector and clamp-on at the grounded transformer beyond the splice area and at the grounded new transformer to check to be sure the phases are correct.
7. Complete the splicing operation. Remove all of the grounds that have been installed at the network transformers. Remove the grounds at the station and turn the IPD transmitter on. This step is a final check to insure that no transformers have been left grounded on this network system when preparing to re-energize the system. The RED lamp should light and remain lit which indicates all transformer grounds have been removed. If the yellow lamp begins flashing, re-check the network transformers for grounding.
Both of these Field Situation operations have been completed safely because the system is always grounded. The only time a ground has to be removed is when the Impulse Phaser transmitter is installed to identify the circuit and phases. Immeadiately after completion of identifying operations, the grounds are reapplied.
The network feeder identification operations can also be accomplished by permanently applying grounds at the station and installing the IPD transmitter at the network transformer beyond the splicing location and grounding elsewhere according to company policies.
In the years between its introduction and now, the operation of the Impulse Phaser remains the same. Because of improvements in electronic technology, improvements have been introduced into its design making the instrument function more efficiently.
Although the Impulse Phaser remains the most accurate and preferred method to identify a paper/lead cable, the need to identify solid dielectric cables in vaults and in direct buried situations is presently the greatest requirement for the Impulse Phaser.