Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – For fault location
Reexamination Certificate
1999-01-21
2001-02-06
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
For fault location
C324S074000
Reexamination Certificate
active
06184689
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a secondary service conductor tester.
An electrical power utility provides electrical power via either underground electrical cables or suspended electrical cables to its customers. A power revenue meter, which normally includes a rotating measurement dial, provides an interface connection between the electrically conductive cables of the power utility and the electrically conductive wiring of the customer. The power revenue meter provides an important delineation between the electrical cable which is the responsibility of the power utility to maintain and the electrical wiring of the customer which is the responsibility of the customer to maintain. The electrical cables from the power utility to the customer are referred to as secondary service, while the electrical wiring of the customer beyond the power revenue meter is referred to generally as the customer wiring.
Customers periodically complain to the power utility concerning potential electrical faults resulting from the secondary service. The customer is not permitted to remedy problems associated with the secondary service. For example, such secondary service electrical faults may include voltage fluctuations and electrical equipment malfunction which is normally the result of a faulty neutral wire. In response to a customer complaint regarding electrical faults, the power utility must verify the condition of the customer's secondary service. The secondary service includes the utilities electrical cables and mechanical connections between-separate electrical cables. To verify the operation of the secondary service a representative from the power utility must travel to the customer and remove the power revenue meter from its meter base supporting the revenue meter. For residential customers the power revenue meter is normally located on the side of the customer's residence at the point where the utility power cable (secondary) interfaces with the electrical wiring of the customer. The lineman then inspects the meter base for apparent visual problems such as loose contacts within the meter base. If no apparent problems exist, then a secondary service conductor tester is engaged with the meter base to replace the removed power revenue meter. The secondary conductor tester provides a current load to the secondary cables to simulate power usage by the customer in order to detect problems originating with the secondary service cables. In particular, the secondary conductor tester measures the voltage levels on the secondary cables, which if below some threshold value indicates that a fault may exist.
The secondary service electrical fault may be the result of many factors, such as, a poor connection of an electrical cable to the meter base, an insufficient crimp on a connector joining a pair of electrical cables, a poor connection of the electrical cable to a transformer on a utility pole, an electrical cable with poor electrical characteristics, or a short from the electrical cable to ground which normally occurs underground. The short from the electrical cable to ground may be the result of a gopher chewing away the insulation of the electrical cable.
If the utility determines that the source of the fault is in the customer wiring (e.g., not in the secondary service) then it is not the responsibility of the power utility to remedy the problem. Likewise, the customer is not permitted by the power utility to repair, remove the power revenue meter, nor generally check the secondary service. An electrical fault on the customer wiring may result from a multitude of factors, such as, an imbalanced load, a bad ground or neutral connection at an electrical panel, a faulty circuit breaker, or a poor appliance.
H. J. Arnett Industries, L.L.C. of Portland, Oreg. manufactures a secondary service conductor tester under the trade name The Super Beast. The Super Beast is a cylindrically shaped device with a set of rearwardly disposed electrical contacts that engage the contacts of the meter base in the same manner as the power revenue meter. The Super Beast is sized to be approximately the same as the displaced power revenue meter so that it may be supported by the meter base and fit within a housing that surrounds the meter base and power revenue meter. The Super Beast houses a pair of active loads which each draw 10 amps of current when activated. Each of the loads includes a primarily inductive/resistive element and a fan element. Each load is arranged within The Super Beast so that it is vented to the exterior of The Super Beast housing to provide self-cooling. The combination of the pair of self-cooling load elements and its compact size permits The Super Beast to be self supported on the meter base in the same manner as the power revenue meter.
When The Super Beast is engaged with the meter base, a fault condition on the secondary service is normally indicated by an 8-10 volt voltage drop on the secondary electrical cable when applying a 20-amp load to the secondary cable using both loads. Unfortunately, several minutes may be necessary before a significant voltage drop is detectable. This time delay before a noticeable voltage drop may be the result of a corroded mechanical connector joining a pair of electrical cables. In addition, frequently the voltage drop is somewhat greater than zero while being somewhat less than 8 volts making it difficult for the lineman to discern whether a fault exists within the secondary service. Accordingly, the lineman may have difficulty discerning some faults and may inadvertently terminate the secondary service test prior to the fault manifesting itself.
What is desired, therefore, is a secondary service conductor tester that makes it easier for a lineman to discern whether a fault exists on the secondary service.
SUMMARY OF THE INVENTION
The present invention overcomes the aforementioned drawbacks of the prior art by a secondary service conductor tester that includes a housing. A set of at least two wires suitable for detachably engaging a meter base are electrically connected to the secondary electrical service of a power utility. A plurality of electrical loads each of which includes a fan unit are capable of drawing approximately 80 amps or more current when activated. A switch is electrically connected to at least one of the at least two wires and the plurality of electrical loads to select respective pairs of the at least two wires through which the current is drawn. A display indicates the electrical voltage drop when a pair of wires are electrically connected to the meter base and the plurality of electrical loads are activated. The electrical loads and the switch enclosed within the housing and at least one of the at least two wires at least periodically electrically connected to the plurality of electrical loads in response to switching the switch.
The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 4646003 (1987-02-01), Phillips et al.
patent: 5650717 (1997-07-01), Draus et al.
Chernoff Vilhauer McClung & Stenzel LLP
H. J. Arnett Industries
Kerveros James
Metjahic Safet
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