CA2146511A1 - Power distribution boxes and networks for film production crews - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A power generating and distributing system for film production crews includes a three-phase generator and a power distributing network. The network consists of cables and multi-phase power distribution boxes that ultimately supply power to single-phase distribution boxes and single-phase equipment. Each multi-phase distribution box has a set of lights that indicate whether each phase input terminals of the box is live, and another set to indicate the state of its circuit breakers and electrical outlets. The indicator lights are colour coded to indicate which breakers and outlets are connected to which phase input terminals. Power cables that couple each phase input terminal of the distribution box to an upstream distribution box are also colour coded to identify corresponding input terminals. An electrical discontinuity in the network, such as an open breaker or a disconnected cable, can be quickly traced by visual inspection of indicator lights.

Description

2146~11 POWER DISTRIBUTION BOXES AND NETWORKS
FOR FLM PRODUCTION CREWS
FIELD OF THE lNVENTION ;
The invention relates generally to portable power generating -5 systems for use by film production crews, and more specifically, to checking of electrical continuity in such systems.
BACKGROUND OF THE INVENTION
Recording scenes for films traditionally requires a multitude of high~powered portable lights and other equipment that operate from a 1 l~volt 10 source. An adequate power source is normally unavailable, and a production crew will normally use a portable diesel-powered three-phase generator and a network of cables to distribute power to various single-phase 110-volt power outlets.
; Since about the 1960' s, a key component of portable power ;; 15 generating systems used by production crews in Canada has been a power distribution box. The distribution box receives three voltage phases, neutral, and ground from an upstream source (typically another distribution box) to ` ~ which it is coupled with cables and releasable connectors. The distribution box `~ may be configured either to pass the three phases, neutral, and ground through power outlets to other downstream distribution boxes or to provide multiple , ~ ~ single-phase power outlets. The arrangement is hierarchical with upstream ;
boxes serving as splitters and power disconnects that isolate various downstream branches. Each ]power oudet may be controlled by a separate ~ circuit breaker to guard against overloads. In main and branch disconnects, a ;~ ~ 25 single multi-pole circuit breakers may control a set of electrical outlets ;
; simultaneously in response to an overload in any one of the phases.
~ Single-phase power boxes (power boxes operated from a single voltage phase) , '~ -1- ' ~'''''';
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- 2146~11 are found at the lowest level of the power distributing network, providing - -multiple single-phase outlets for operation of lights and other equipment.
This arrangement allows groups of equipment to be conveniently added to and removed from the network. It also reduces the likelihood that an 5 overload created in one equipment grouping will disable other equipment groupings. However, given the nature of video production, including indiscriminate connection of equipment to power outlets, overloads and simultaneous failures of different equipment groupings are quite common.
A major problem with such practices is that the source of an 10 electrical discontinuity can be very difficult to identify. If a particular item or grouping of equipment fails, a circuit breaker may have opened on a distributionbox a considerable distance upstream from the equipment. Alternadvely, a - ;power cable may be disconnected somewhere upstream from the equipment.
The production crew is often forced to hunt for the discontinuity, checking 15 circuit breakers on various distribution boxes and using voltage meters to check electrical continuity at various cable junctions.
Locating and handling electrical discontinuities has been frustrating and time-consuming. Since film production is labour intensive and often involves costiy equipment rentals, delays in locating and correcting 20 electrical discontinuities contribute significantly to production costs. Although this problem has persisted for several decades, no solution has been made commercially available.
SUMMARY QF TH~3 ~ENTION
In one aspect, the invention provides a portable power 25 distribution box for distributing electric power from a source providing a ~;
plurality of phases, a neutral, and a ground. The distribution box has a housingcontaining a plurality of phase input terminals, a neutral input terminal, and ground input terminaL Releasable connector means which are accessible from ~ ~

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externally of the housing permit each phase input terminal to be coupled to a different phase, the neutral input terminal, to the neutral, and the ground input terminal, to the ground. A multiplicity of electrical outlets are mounted to thehousing. Circuit breakers means couple the electrical outlets to different phase5 input terminals so that each electrical outlet is powered from an associated phase input terminal or isolated from the associated phase input terminal in response to a current overload. The electlical outlets may simply pass the phases in which case separate outlets may be provided to pass the neutral and the ground, or each electrical outlet may be coupled to a phase input terminal, neutral and 10 ground to serve as single-phase outlet. The circuit breaker means may consistof separate circuit breakers each coupling one of the electrical outlet to its associated phase input terminal and controlling only the one electrical outlet.
The circuit breaker means may alternatively consist of a multi-pole circuit breaker which couples multiple electrical outlets to various input terminals and15 which simultaneously isolates all such outlets from the phase input terminals in u ~ response to a current overload sensed at any one of the outlets. Input-power ~ indicating means are mounted on the housing to emit light to indicate the : ~`
; electrical state (powered or unpowered) of each phase input terminals.
Output-power indicating means are mounted on the housing to emit light to 20 indicate the electrical state (powered or unpowered) of each electrical outlet.
Various electronic displays might potentially be used to visually indicate the electrical states of the phase input terminals and electrical outlets.
However,` in preferred form, the indicating means are separate indicator lights.A set of input indicator lights may be connected to the phase input terrninals -25 such that each light is illuminated when an associated phase input terminal is powered and extinguished when the associated phase input terminal is -~
~ unpowered. A set of output indicator lights may be connected to the electrical `~ outlets such that each light is illuminated when an associated electrical outlet is - 21~511 powered and is extinguished when the associated electrical outlet is unpowered.
The input and output indicator lights may be colour coded to permit a worker to identify which electrical outlets are associated with which phase input ter ninals.
In another aspect, the invention provides a power distribution 5 systems adapted for use by production crews and operable with a portable generator providing a plurality of phases, a neutral, and a ground. The power distribution system comprises a portable upstream power distribution box and several portable downstream power distribution boxes. The distribution boxes are electrically coupled, the coupling means including cables terminated with 10 releasable connectors. Each distribution box has phase input terminals, a neutral input terminal, a ground input terminal, and connector means for releasably connecting the input terminals to the cables such that each phase input terminals is coupled to a different phase, the neutral input terminal, to the neutral, and the ground input terminal, to the ground. Each distribution box has15 multiple electrical outlets, and circuit breaker means coupling the electrical outlets to different ones of the phase input terminals. Each distribution box has input-power indicating means adapted to emit light to indicate the electrical state of each of its phase input terminals, and output-power indicating means adapted `, to emit light to indicate the electrical state of each of its electrical outlets. As ~ -20 mentioned above, the input-power and output-power indicating means of each distri~ution box preferably produce light that is colour-coded to relate the electrical outlets to the phase input terminals of the distribution, box. The connector means may comprise power cables electrically connected to the phase ~ ~-input terminals and colour-coded to identify the associated phase input : ` :
25 terminals.
With a power distribution system configured as described above, a production crew can quickly trace the location of an electrical `~
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discontinuity that has produced an equipment failure. Breakers need not be closely examined and various cable junctions need not be checked with a voltage meter. The power distribution box immediately upstream of the equipment will give a visual indication of received electrical power and also whether its electrical outlets are live. All upstream boxes will provide similarvisual indications. A tripped breaker or an open junction in the cables between distribution boxes can be quickly identified.
Various aspects of the invention will be more apparent from a description below of preferred embodiments and will be more specifically defined in the appended claims.
DESCRIPFION OF THE DRAWlNGS
The invention will be better understood with reference to drawings in which:
fig. 1 is an isometric view of a three-phase portable power distribution box with a door open to expose a control panel; ~
.
fig. 2 is a plan view of the power distribution box with the door ; ~ closed;
; ~ fig. 3 is an end view of the power distribution box showing its various single-phase outlets;
fig. 4 is an electrical schematic of the wiring within the ~
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" ~ distribution box; and, fig. 5 is a schematic representation of a portable power .
.
generating and distributing network incorporating the power distribution box. :
DESCRIPrION OF PREFERRED EMBODIMENTS
Figs. 1~ illusbrate various features of a portable distribution box PDB 1. This particular distribution box PDB 1 is adapted to receive -three-phase power and to output single-phase power. It comprises a metal -housing 10 which includes a control panel 12, a hinged door 14 with a window ~

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16 that permits viewing of the control panel 12, and a conventional catch 18 to secure the door 14. A pair of handles 20 attached to the housing 10 facilitate carrying. The housing 10 contains three phase input terminals INI-lN3, a neutral input terminal IN4, and a ground input terminal IN5 (all of which are shown only in fig. 4), which are mounted in a conventional manner within the housing 10. The input terminals INl-IN5 are preferably conventional posts carrying clamping mechanisms for wiring, but any electrical junction is appropriate. Power cables P1-P5 extend from the housing to permit the distribution box PDB1 to be coupled to an upstream source. The cables Pl-P5 are electrically connected to different input terminals IN1-IN5. The cable P1 which is typical is terminated with a conventional releasable CAMLOCKTM
connector 21 for coupling the phase input terrninal IN1 to a phase output terminal of an upstream three-phase source. Similar connectors terminate the ;~ cables P2-P5, but have not been illustrated.
The housing 10 carries six single-phase electrical outlets OUT1-OUT6 that are shown in fig. 2. The electrical outlet OUTl is typical and :
comprises a phase output ter ninal 22, a neutral output terminal 24, and a - ~
ground output terminal 26. The electrical outlets OUTl-OUT6 are arranged in :
~ a straight-line fashion equally spaced apart along one side of the housing 10.
`~- 20 Six circuit breakers CBI-CB6 are mounted to the housing 10 and accessible at : . .
the panel 12. Each of the circuit breakers CB1-CB6 is associated with and controls a different one of the electrical outlets OUT1-OUT6. Three input indicator lights LIl-LI3 are mounted on the panel 12. Each of the input indicator lights LI1-I,I3 is associated with a different one of the phase input terminals IN1-lN3 and visually indicates the electrical state (powered or unpowered) of its associated phase input terminal. Six output indicator lights LO1-LO6 are also mounted on the panel 12. Each of the output indicator lights ~ ~:
: ~. ,; ' LO1-LO6 is associated with a different one of the electrical outlets ~ :.;~."', ~::
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OUT1-OUT6 and circuit breakers CB1-CB6, providing a visual indication of the state of the associated breaker (open or closed) and consequently the state of the associated electrical outlet (powered or unpowered).
Fig 4 is a schematic representation of various components of 5 the power distribution box PDB 1. Each input indicator light is connected between its associated phase input terminal and neutral. Thus, each input indicator light is illuminated or extinguished according to the electrical state of its associated phase input terrninal. Each circuit breaker couples the phase output terminal of its associated electrical outlet to one of the phase input ~ ~
terminals. The outlet OUT1, breaker CB1 and output indicator light LO1 form .
a typical associated set. The breaker CB1 couples the electrical outlet OUT1 to phase input terminal IN1, the output terminal of CB1 being connected to the phase output ter ninal 22 of the electrical outlet OUT1 and the input terminal of the breaker CB 1 being connected to the phase input terminal IN 1. The output indicator light LO1 has one electrical contact connected to junction of the phase ~ -output ter ninal 22 of the outlet OUT1 and the output terminal of the circuit breaker CB 1 and has another electrical contact connected to neutral thus indicating the electrical state, powered or unpowered, of the electrical outlet OUT1. If the phase input terminal INI is powered, the output indicator light 20 LO1 is illurninated whenever the circuit breaker CB1 is closed and extinguished ~` whenever the circuit breaker CB 1 is open. Accordingly, when the phase input terminal IN1 is live, the~ output indicator light LO1 provides an immediate visual ~ ;
indication of whether the circuit breaker CB 1 is in an open or closed state. -The manner in which the electrical outlets OUT1-OUT6 are 25 coupled to the phase input IN1-lN3 should be noted. Ideally all three phases ; of a generator supplying power to the distribution box PDB1 and comparable ~; boxes should be equally loaded. In prior art distribution boxes, the six : ~
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`,:~ , ::,: '-:" ~:, ~-;'' : , .:- ' ', , 21~6~ 1 electrical outlets OUT1-OUT6 would effectively be divided into adjacent pairs, and each adjacent pair would be connected to the same phase input terminal.
Common practice among production crews is simply to connect downstream boxes to the electrical outlets OUTl-OUT6 sequentially from left-to-right or 5 vice versa. If not completely filled, a load current might be drawn from only one phase or perhaps from two phases. The third phase often tends to have no load. In the distribution box PDB 1 illustrated, the six outlets OUT l-OUT6 are grouped as a left set 28 of three and a right set 30 of three. Within each set 28, 30, each electrical outlet is connected to a different phase input terrninal 10 IN1-IN3. As the outlets OUT1-OUT6 are filled from left-to-right, there is a greater tendency to distribute current load among all phases, even if the outlets are not completely utilized. This arrangement will not guarantee that all phasesdraw equal currents, but does tend to ensure that all phase are conducting some load current given prevailing practices among production crews.
The various indicator lights are colour coded to facilitate identification and tracing of discontinuities. The three power input indicator ; " lights LI1-LI3 are respectively red, amber and 'olue. Each of the output ~ indicator lights LO1-LO6 produces light of the same colour as the input -, .. .
indicator light associated with the phase input terminal to which the electrical outlet associated with the output indicator light is coupled. For example, the ~ ~ -~ . : .....
output indicator lights LO1 and LO4 produce red light and correspond to the red input indicator light LIl associated with the input terrninal IN1. The associated i~
electrical out1ets OUTl and OUT4 are of course powered from the same phase - ~ ;
input terminal IN1 through their respective breakers CB1 and CB4. In use, the electrica1 state of the power distribution box PDB 1 is fully indicated to the user. ~ :
The input indicator lights LI1-LI3 indicate whether each phase is properly received. The output indicator lights LO1-LO6 indicate whether any of the circuit breakers CB 1-CB6 is open and any corresponding electrical outlet is , -, , ¢ ~, . , ~ ~ ' . . , , i . . , : , . ' ~146~1 unpowered. If the input indicator light LI1 were extinguished, for exarnple, there would be an electrical discontinuity (open cable connection or open breaker) upstrearn. If only one of the output indicators lights LO1 and LO4 were extinguished, but the input indicator light LI1 illuminated, there would be5 an imrnediate indication that a single breaker CB 1 or CB4 is open. Although such a condition rnight be apparent without colour coding of the various lights,the colour coding is helpful where multiple discontinuities arise. For exarnple,one phase input terminal may unpowered but a circuit breaker powered from another live phase input terminal may not have been reset or may have opened 10 in response to an overload. Additionally, each of the cables P1-P5 is colour coded to identify its associated input terminal. In this embodiment, the ccnnector associated with the cable P1 is r~d, corresponding to input indicator light LI1 associated with the phase input terrninal IN1. * The cables P2 and P3 are colour coded by termination with similar connectors (not shown) that are 15 respectively black (arbitrarily selected to correspond to the phase input terminal P2 which has an associated amber indicator light LI2) and blue. By observing :. . ,.. , :, the colour coding scheme when connecting the box PDB1 and comparable ~ :
~ boxes in a network, a particular phase can be conveniently traced upstrearn and ;;
``~ downstream among various branches, by inspecting phase input and output : ~ 20 indicators lights on the boxes, to determine what items of equipment are connected to a particular phase and together creating an overload condition.
The advantage provided by the invention will be more apparent with reference to fig. 5 which schematically illustrates a portable power generating and distributing network adapted for use by production crews. The network includes a conventional portable three-phase electric generator ~at provides three separate 110-volt phases 32 (120-degrees phase-shifted relative to one another) at phase outputs 34, 36, 38, produces a neutral output at 40, and a ground output at 42. A main disconnect 44 receives and effectively g .. . . , ~ ,. - ~ ~, , . , . ,, ~, - .
:, ,,., , ~ .; , ;.-~ .. , ~, . .. .. -passes the three phases, neutral and ground downstream to a double disconnect 46. The double disconnect 46 serves essentially as a sp!itter, supplying electric power downstream to two main branches BRl, BR2 (components of the branch BR2 not illustrated) of the distribution network. This permits power to each 5 main branch to be turned off or on separately. Branch disconnects BD1, BD2 receive and pass the three-phase power from the double disconnect 46. The branch disconnects BD1, BD2 may in turn supply three-phase power to multiple downstream three-phase to one-phase distribution boxes, such as the ;
boxes PDBl-PDB4 (all identical to the distribution box PDB1). The power 10 distribution box PDB1 is shown coupled to three downstream single-phase power boxes SPB 1-SPB3 which receive a single phase input and might typically have multiple single-phase voltage outlets powered from the single phase. The comparable power distribution box PDB3 is shown coupled to three downstrearn single-phase power boxes SPB4-SPB6. Lighting and other ~ .:
equipment would normally be plugged into the 110 volt sockets of the : `
single-phase boxes SPBl-SPB6.
Each three-phase distribution box in the network~ whether a main disconnect, double discoMect, branch disconnect or the like, uses the same arrangement of input and output indicators lights that has been described 20 in connection with the power distribution box PDBl and also the same colour coding of its power cables. The various disconnects, however, will normally use multi-pole circuit ~breakers that control sets of electrical outlets simultaneously. For example, the double discoMect 46 has two sets of electrical outlets that supply three-phase power to the two network branches 25 BRl, BR2. Each set of outlets of the double disconnect 46 is associated with its own multi-pole circuit breaker that couples the three phase outlets of the set ~ to the phase input terminals of the double disconnect 46, and disables all three ::~

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phase outlets simultaneously if an overload occurs. Each set of outlets in the -double disconnect 46 has its own set of three output indicator lights.
To better indicate the utility of the invention, a hypothetical problem will be considered. A member of the production crew may connect an item of equipment 48 with a significant current demand to the single-phase box SPB2 that is powered from the distribution box PDB 1. Another member of the production crew may already be operating another item of equipment 50 that draws a significant current from the single-phase box SPB5 that is powered from the distribution box PDB3. The load current introduced by the newly-connected equipment 48 may not be sufficient to trip a breaker in either of the two immediately upstream distribution boxes, namely, distribution box PDB1 or the branch disconnect BD1. However, when combined with load - . .
current from the other item of equipment 50 connected to the box SPB5 (and - ~
equipment elsewhere), there may be sufficient total current demand to trip a .; . -breaker in the upstream double disconnect 46. All phases are disabled : -throughout network branch BR1, and all equipment is disabled, including the two noted items of equipment 48, 50. -The crew member operating the equipment 48 can trace the problem quickly and directly to the open circuit breaker of the double disconnect ~', 20 46. First, he may disconnect the equipment 48 which apparently triggered the power failure. Tracing to the immediately upstream distribution box PDB 1, he ~,., 1~ willi note that the output indicator lights LO1-LO6 and the input indicator lights LI 1-LI3 are all extingùished, indicating a problem upstream. Moving upstream to the branch disconnect BD1, he will immediately observe that its input and ;~ 25 output indicator lights are all extinguished, indicating a problem further upstream. Moving upstream to the double disconnect 46, he will note that its ` ~ ~ input indicator lights are illuminated, but the output indicator lights for the set of -;
outlets supplying power to branch BR1 are all extinguished. He thus quickly , .
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identifies that a circuit breaker associated with the disconnect 46 has tripped,and he can reset tlhe open breaker. Equipment can then be redistributed among the various phases to avoid recurrence of the overload. In that regard, the colour-coded output indicator lights can be used to identify which single phase 5 power boxes are powered from the same phase as the box SPB2 and which items of equipment, such as the equipment 50, are powered from that phase and together created the overload.
Another hypothetical problem will be considered. The power supply line 52 has been inadvertently disconnected from an electrical outlet of the double disconnect 46. The particular output terminal is assumed to be - ~ ~
associated with an amber output indicator lamp on the double disconnect 46. A ~:
member of the production crew notes that the item of equipment 48 has failed together with other equipment connected to the single phase power distribution box SPB2, and must identify the source of the problem.
The crew member checks the upstream distribution box PDB 1 that supplies power to the single phase box SPB2. He notes that the amber output indicator lights LO2 and LO5 are extinguished, and that the phase input terminal ~2 of the power distribution box PDB 1 has an extinguished amber input indicator light LI2. Moving upstream to the branch disconnect BD1, he 20 will immediately observe that its amber input and output indictor lights are also extinguished. Moving further upstream to the double disconnect 46, he will note that its amber input indicator light is illuminated and its amber output indicator lights are also illuminated. He will thus have identified an electrical discontinuity between the double disconnect 46 and the branch disconnect BD1, ~ .
25 specifically the disconnected cable 52. By checking cable junctions along the cable 52, he can find and correct the disconnection.
Two-phase generators are still in use in the film production ` industry although three-phase generators are more common. If a two-phase -,, , - 12- ~

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generator is used, a power distribudng network may be formed of cables and distribution boxes similar to the box PDB I . The distribution boxes will of course be adapted to receive only two phases, neutral and ground. The distribution boxes may be adapted either to pass the two phases, neutral and S ground or to provide multiple electrical outlets powered from the two phases.
Only two colour-coded indicator lights are required to indicate the state of phase inputs. One output indicator light will be associated with each electrical outlet that provides one of the phases, and may be colour-coded to identify the -;
associated phase input terminal. The invention can thus accommodate power 10 distribution networks and systems that involves two or more electrical phases.
It will be appreciated that particular embodiments of the invendon has been described and that modifications may be made therein without depardng from the spirit of the invention or necessarily departing from the scope of the appended claims. For certainty of interpretation, any reference15 in the claims to a "producdon crew" should be understood as a crew involved in film producdon or comparable video recording.

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Claims (10)

1. A portable power distribution box adapted to be used by aproduction crew to distribute electric power from a source that provides a plurality of phases, a neutral, and a ground, the power distribution box comprising:
a housing;
a multiplicity of input terminals mounted in the housing, the input terminals including a plurality of phase input terminals, a neutral input terminal, and ground input terminal;
releasable connector means connected to the input terminals and accessible from externally of the housing for releasably coupling each of the phase input terminals to a different one of the phases, the neutral input terminal to the neutral, and the ground input terminal to the ground;
a multiplicity of electrical outlets mounted to the housing;
circuit breakers means coupling the electrical outlets to different ones of the phase input terminals thereby to power each of the electrical outletfrom an associated one of the phase input terminals and to isolate each of the electrical outlets from the associated phase input terminal in response to a current overload;
input-power indicating means mounted on the housing and coupled to the phase input terminals for emitting light to indicate the electrical state of each of the phase input terminals; and, output-power indicating means mounted on the housing and coupled to the electrical outlets for emitting light to indicate the electrical state of each of the electrical outlets.

2. The portable power distribution box of claim 1 in which:
the input-power indicating means comprise a plurality of separate input indicator lights, each of the input indicator lights is associated with a different one of the phase input terminals and electrically connected to the associated phase input terminal such that the input indicator light is illuminated when the associated phase input terminal is in a powered state and is extinguished when the associated phase input terminal is in an unpowered state;
and, the output-power indicating means comprise a multiplicity of separate output indicator lights, each of the output indicator is associated with a different one of the electrical outlets and electrically connected to the associated electrical outlet such that the output indicator light is illuminated when the associated electrical outlet is in a powered state and is extinguished when the associated electrical outlet is in an unpowered state.

3. The portable power distribution box of claim 2 in which:
each of the input indicator lights produces light of a different colour; and, each of the output indicator lights produces light of the same colour as the input indicator light associated with the phase input terminal to which the electrical outlet associated with the output indicator light is coupled by the circuit breakers means.

4. The portable power distribution box of claim 3 in which the connector means comprise a plurality of power cables extending from the housing, each of the cables being electrically connected to a different one of the phase input terminals and coded with a colour indicating the phase input terminal to which the cable is connected.

5. The portable power distribution box of claim 1 in which:
the plurality of phase input terminals consists of three phase input terminals;
the multiplicity of electrical outlets comprises six electrical outlets spaced apart along a straight line, the six electrical outlets constituting a left set of three outlets and a right set of three outlets;
each of the electrical outlets of the left set is coupled by the circuit breaker means to a different one of the three phase input terminals;
and, each of the electrical outlets of the right set is coupled by the circuit breaker means to a different one of the three phase input terminals.

6. The portable power distribution box of claim 2 in which each of the electrical outlets comprises a phase output terminal electrically connected to the phase input terminal associated with the electrical outlet, a ground output terminal electrically connected to the ground input terminal, and a neutral output terminal electrically connected to the neutral input terminal.

7 . A power distribution system adapted for use by a production crew and operable with a portable generator providing a plurality of phases, a neutral, and a ground, the system comprising:
a portable upstream power distribution box;
a plurality of portable downstream power distribution boxes;
means for electrically coupling the upstream power distribution box to the downstream power distribution boxes, the coupling means comprising power cables terminated with releasable connectors;
each of the upstream and downstream power distribution boxes comprising:
(a) a housing;
(b) input terminals mounted in the housing, the input terminals comprising a plurality of phase input terminals, a neutral input terminal, and aground input terminal;
(c) connector means cooperating with the connectors to releasably connect each of the input terminals to the cables such that each of the phase input terminals is coupled to a different one of the phases, the neutral input terminal is coupled to the neutral, and the ground input terminal is coupled to the ground;
(d) a multiplicity of electrical outlets mounted on the housing;
(e) circuit breakers means coupling the electrical outlets to different ones of the phase input terminals thereby to power each of the electrical outletfrom an associated one of the phase input terminals and to isolate each of the electrical outlets from the associated phase input terminal in response to a current overload;
(f) input-power indicating means mounted on the housing and coupled to the phase input terminals for emitting light to indicate the electrical state of each of the phase input terminals; and, (g) output-power indicating means mounted on the housing and coupled to the electrical outlets for emitting light to indicate the electrical state of each of the electrical outlets.

8. The system of claim 7 in which, for each of the upstream and downstream power distribution boxes:
the input-power indicating means comprise a plurality of separate input indicator lights, each of the input indicator lights is associated with a different one of the phase input terminals and electrically connected to the associated phase input terminal such that the input indicator light is illuminated when the associated phase input terminal is in a powered state and is extinguished when the associated phase input terminal is in an unpowered state;
and, the output-power indicating means comprise a multiplicity of separate output indicator lights, each of the output indicator is associated with a different one of the electrical outlets and electrically connected to the associated electrical outlet such that the output indicator light is illuminated when the associated electrical outlet is in a powered state and is extinguished when the associated electrical outlet is in an unpowered state.

9. The system of claim 8 in which, for each of the upstream and downstream power distribution boxes:
each of the input indicator lights produces light of a different colour; and, each of the output indicator lights produces light of the same colour as the input indicator light associated with the phase input terminal to which the electrical outlet associated with the output indicator light is coupled by the circuit breakers means.

10. The system of claim 9 in which, for each of the upstream and downstream power distribution boxes, the connector means comprise a plurality of power cables extending from the housing, each of the cables being electrically connected to a different one of the phase input terminals and codedwith a colour indicating the phase input terminal to which the cable is connected.