Electrical transmission or interconnection systems – Switching systems – Condition responsive
Reexamination Certificate
2000-10-30
2002-04-23
Ballato, Josie (Department: 2836)
Electrical transmission or interconnection systems
Switching systems
Condition responsive
C307S112000, C307S115000, C307S113000, C307S064000, C307S043000
Reexamination Certificate
active
06376937
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to a collar for a watt-hour meter, and more particularly to a meter collar which is configured for a use with an interface circuit that facilitates using an on-site energy source in lieu of or in addition to commercial power from an electric utility company. The interface circuit may isolate the utility company's power lines when the on-site source is used, or it may permit the on-site power source to be used in parallel with commercial power. The invention is also directed to an interface circuit itself, whether it is used in conjunction with a meter collar or is instead associated with other components of a customer's private electrical distribution system, such as a meter socket box or a circuit breaker box.
Some customers of commercial electrical utility companies would like the option of using power which they, the customers, generate or store locally, or on-site. The customer's on-site power source may comprise, for example, a generator which is powered by a gasoline or diesel engine or a combustion turbine, a solar cell array which charges storage batteries that then supply electricity to an inverter for conversion to alternating current, a fuel cell and an inverter, or simply back-up storage batteries which are kept charged using commercial power and which supply power through an inverter when necessary.
Among the problems that typically confront a customer who wants the option of using either his or her on-site power source or the utility company's power is that the modifications in the wiring of the customer's private electrical distribution system (at the customer's residence, for example, or at a small business establishment receiving two-phase service) to accommodate the on-site power source are relatively expensive. Another problem is that the customer's electrical distribution system should either be isolated from the utility company's power lines, or connected to the power lines in a carefully controlled manner, when the on-site power source is used. The isolation option not only prevents possible damage to the utility company's distribution system and to the loads of other customers, it also protects technicians who may be working on the utility company's power lines from electricity generated by the customer's on-site power source. Safety is a paramount concern for utility companies, which train their line technicians to make sure the lines they are working are on are electrically isolated from the utility company's generating facilities. It is not customary for line technicians to also isolate the segments they are working on from the customers, however, unless the technicians have been specifically trained to do so.
Despite this potential hazard, it may desirable to permit a customer to use his or her own on-site power source in parallel with the utility's power, so that both the on-site power and the utility's power can be consumed by the customer's loads. If the utility permits, parallel operation would also allow excess on-site power to be coupled to the utility's power lines for distribution to other customers.
FIG. 1
illustrates a typical prior art arrangement illustrating how a utility's distribution system may be connected to the private distribution system of a customer who receives two-phase service (such as a residential customer with 110-volts/220-volt service or a small business owner with 110-volt/220-volt service). A utility substation
20
receives power at a high voltage from a generating station (not illustrated) and distributes this power (at a stepped-down but nevertheless relatively high voltage and in three phrases) to a network which includes a step-down transformer
22
. The primary winding of the transformer
22
receives one of the phases from the substation
20
, and the secondary winding in center-tapped. The center tap, which is grounded, is connected to a neutral power line
24
. A “leg
1
” of the secondary winding is connected to a leg-
1
power line
26
and a “leg
2
” of the secondary winding is connected to a leg-
2
power line
28
. The potential difference between the leg-
1
power line
26
and the neutral line
24
is typically 110 volts (average) and the potential difference between the leg-
2
power line
28
and is also typically 110 volts (average). However, leg-
1
power line
26
is 180° out of phase with the leg-
2
power line
28
. Consequently, a load which is connected between the neutral line
24
and either of the leg-
1
or leg-
2
power lines
26
and
28
receives 110 volts while a load connected between the leg-
1
and leg-
2
power lines
26
and
28
receives 220 volts. The two-phase service that is illustrated in
FIG. 1
can thus supply power to both 110 volt loads and 220 volt loads that are connected to a customer's private distribution system.
FIG. 1
also shows the front side of a meter socket box
30
and the back side of a watt-hour meter
32
. The socket box
30
has a recessed socket
34
with utility-side contacts
36
and
38
and customer-side contacts
40
and
42
. Each of the contacts includes a pair of electrically conductive arms (not numbered). The socket
34
also includes a neutral contact
44
that is connected by a neutral service line
46
to the neutral power line
24
and to a neutral line
48
of the customer's private distribution system. The arms of the contact
36
are connected via a leg-
1
service line
50
to the leg-
1
power line
26
and the arms of the contact
38
are connected via a leg-
2
service line
52
to the leg-
2
power line
28
. The arms of the contact
40
are connected to a leg-
1
line
54
of the customer's distribution system while the arms of the contact
42
are connected to leg-
2
line
56
of the customer's distribution system
With continuing reference to
FIG. 1
, the back side of the meter
32
is provided with four contacts,
58
,
60
,
62
, and
64
. When the meter
32
is plugged into the socket
34
as indicated schematically by arrow
66
, the contact
60
is wedged between the arms of the contact
36
to form a connection, the contact
58
is wedged between the arms of the contact
38
to form a connection, the contact
64
is wedged between the arms of the contact
40
to form a connection, and the contact
62
is wedged between the arms of the contact
42
to form a connection. Meter
32
is an electromechanical meter having a Farraday motor and a gear train (not illustrated) which turns dials (not illustrated) when the motor rotates. The meter includes a low resistance winding (not numbered) between the contacts
58
and
62
and another low resistance winding (also not numbered) between the contacts
60
and
64
. The meter also includes a high resistance winding (not numbered) between the contacts
62
and
64
. The net result is that, when the meter
32
is plugged into the socket
34
, the leg-
1
line
54
of the customer's distribution system is connected to leg-
1
power line
26
, the neutral line
48
of the customer's distribution system is connected to neutral power line
24
, and the leg-
2
line
56
of the customer's distribution system is connected to the leg-
2
power line
28
. The meter
32
records the watt-hours consumed by the loads connected to the customer's distribution system.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a meter collar which houses, in whole or in part, or which is connected to, an interface circuit that permits easy connection of an on-site power source to a customer's loads while reliably and automatically disconnecting the utility's power lines from the loads.
Another object is to provide a meter collar which houses, in whole or in part, or which is connected to, an interface circuit that permits easy connection of a on-site power source to a customer's loads in parallel with the utility.
Another object is to provide a meter collar which houses, in whole o
Ballato Josie
Deberadinis Robert
Kunitz Norman N.
Potomac Capitol Investment Corp.
Venable
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