Why is accurate phase identification so important?
- It’s common for underground cables to be mislabeled. This causes confusion during outages. Also, when two circuits need to be looped together, the labeling must be right. It’s inconvenient to de-energize a circuit to determine phasing. The AP30 determines phasing on energized equipment.
- Long over-head lines can easily have mislabeled or uncertain phasing. This can result in substation problems such as delays in construction.
- When a utility wants to optimize load balance to reduce losses, it’s essential to know which phase is which, so loads can be transferred correctly.
- If a protective relay or revenue meter is working incorrectly, it’s vital to know where the phasing got mixed up.
- It’s common to have confused phasing through three-phase transformers. It’s important to determine the phasing to avoid trial-and-error transformer connections.
- Besides the issues associated with load balance and system optimization, inaccurate phase labeling can result in equipment damage and injury of personnel.
Why not use “Phasing Sticks” instead?
A set of Phasing Sticks is really just a high-range voltmeter that will determine if two phases match or not. Phasing Sticks can determine if two like-labeled conductors are actually different phases, but an AP30 is required to determine which one is labeled correctly.
Can the AP30 determine phase rotation?
Yes. The AP30 will display the phase angle of every voltage reading. This determines rotation.
Where can the AP30 be used?
The AP30 will determine the phase of any energized conductor with at least 120V and has been used up to 500kV.
- Bare buswork as in substations
- Bare conductors such as distribution or transmission lines
- Taped buswork as used in switchgear
- Test points on 200A cable elbows
- Test points on 600A cable elbows
- Insulated bolts on the back of 600A T-body elbows
- Potential transformer secondaries. (It will work indoors as long as the Hotstick Unit is in sight of the Field Unit and the Field Unit is outside an open door.)
- 120V household outlet
- With the optional GPS/Cell antenna extension reel, the Field Unit can be taken into deep vaults or indoors to determine phasing.
What’s the maximum distance between the Reference and Field Unit?
Measurements have been routinely taken with a distance of 800 miles between the Reference and Field Units. At this distance it is common to get some seasonal power angle shift across the power grid, so it’s a good idea to verify occasionally on a known phase before checking unknown equipment.
This power angle shift should be insignificant at the more normal maximum distances, say in the 300 mile range.
What are the basics of how the AP30 system works?
The Reference Unit takes a reading every second of the degrees to the next voltage sine wave zero crossing. When a Field Unit calls in, the Field Unit compares the local angle measurement to the cataloged value for that matching second. Since the GPS time is precisely the same at each location and since the phase “A” voltage is in phase at each location, the angle comparison determines how many degrees the Field Unit voltage is away from the Reference Unit, which then determines the phase identification as well.
What factors make the AP30 a superior product in the marketplace?
- The AP30 PhaseTrakker provides instantaneous absolute phase and phase angle identification, anywhere on an overhead or underground transmission or distribution system, (where live contact is possible.)
- With each purchase, the AP30 Field Unit includes a free year of cellular service.
- In areas where no cellular service is available, the AP30 can still record up to 1000 phase readings over a period of 30 days, which can be retrieved when cell signal is re-acquired. The system is configured to allow transferring the phase data to a laptop for use with mapping systems and databases.
- The AP30 is portable, durable, and can be used independently from the work vehicle.
- The AP30 features an easy to read LCD screen, and all calibration functions can easily be performed via convenient touch-screen process. Phase readings can be instantly shifted to adjust for Delta-Wye transformers.
- The AP30 Field Unit can be calibrated to communicate with 2 Reference units at different locations. As long as the Field Unit and Reference Unit are located on the same power grid, (regardless of distance,) phase identification can be achieved.
Is a cellular signal amplifier available for the Field Unit in areas of weak reception?
Yes! EDM offers a portable, rechargeable cellular amplifier accessory for the Field Unit.